In rotationally extruded fittings,high-density polyethylene(HDPE)pipes prepared using conventional processing methods often suffer from poor pressure resistance and low toughness.This study introduces an innovative ro...In rotationally extruded fittings,high-density polyethylene(HDPE)pipes prepared using conventional processing methods often suffer from poor pressure resistance and low toughness.This study introduces an innovative rotary shear system(RSS)to address these deficiencies through controlled mandrel rotation and cooling rates.We successfully prepared self-reinforced HDPE pipes with a three-layer structure combining spherical and shish-kebab crystals.Rotational processing aligned the molecular chains in the ring direction and formed shish-kebab crystals.As a result,the annular tensile strength of the rotationally processed three-layer shish-kebab structure(TSK)pipe increased from 26.7 MPa to 76.3 MPa,an enhancement of 185.8%.Notably,while maintaining excellent tensile strength(73.4 MPa),the elongation at break of the spherulite shishkebab spherulite(SKS)tubes was improved to 50.1%,as compared to 33.8%in the case of shish-kebab spherulite shish-kebab(KSK)tubes.This improvement can be attributed to the changes in the micro-morphology and polymer structure within the SKS tubes,specifically due to the formation of small-sized shish-kebab crystals and the low degrees of interlocking.In addition,2D-SAXS analysis revealed that KSK tubes have higher tensile strength due to smaller crystal sizes and larger shish dimensions,forming dense interlocking structures.In contrast,the SKS and TSK tubes had thicker amorphous regions and smaller shish sizes,resulting in reduced interlocking and mechanical performance.展开更多
The objective of this work is to demonstrate how the viscoelastic, thermal, rheological, hardness, wear resistance and fracture behavior of bioinert high-density polyethylene （HDPE） can be changed by the addition of...The objective of this work is to demonstrate how the viscoelastic, thermal, rheological, hardness, wear resistance and fracture behavior of bioinert high-density polyethylene （HDPE） can be changed by the addition of hydroxyapatite （HAP） nano particles. Also the effects of accelerated thermal ageing on the composite properties have been investigated. Different weight fractions of HAP nano particles up to 30 wt% have been incorporated in HDPE matrix by using melt blending in co-rotating intermeshing twin screw extruder. The fracture toughness results showed a remarkable decrease in proportion to the HAP content. The differential scanning calorimetry results indicated that the melting temperature and crystallinity were affected by the addition of HAP nano particles into the matrix. The complex viscosity increased as the percentage of HAP increased due to the restriction of the molecular mobility. The dynamic mechanical analysis results revealed that higher storage modulus （8.3 1011 Pa） could be obtained in the developed HDPE/HAP in 30 wt% compared to neat HDPE （5.1 1011 Pa）. Finally, the hardness and wear resistance of HDPE were improved significantly due to the addition of HAP nano particles. The changes in the HDPE and its nano composite properties due to ageing showed that the HDPE and its nano composites crystallinity increased while the fracture toughness, hardness, wear resistance, storage and loss modulus decreased.展开更多
Nanocomposites of high-density polyethylene(HDPE)modified with 0.2 phr graphene-zinc oxide(GN-ZnO)exhibited optimal mechanical properties and thermal stability.Two other nano-materials—GN and nano-ZnO—were also used...Nanocomposites of high-density polyethylene(HDPE)modified with 0.2 phr graphene-zinc oxide(GN-ZnO)exhibited optimal mechanical properties and thermal stability.Two other nano-materials—GN and nano-ZnO—were also used to compare them with GN-ZnO.increasing the content of GN-ZnO gradually enhanced the antibacterial and barrier properties,but the addition of 0.3 phr GN-ZnO led to agglomeration that caused defects in the nanocomposites.Herein,we investigated the antibacterial and barrier properties of HDPE nanocomposites infused with different nanoparticles(GN,ZnO,GN-ZnO)of varying concentrations.HDPE and the nanoparticles were meltblended together in a Haake-Buchler Rheomixer to produce a new environment-friendly nano-material with improved physical and chemical properties.The following characterizations were conducted:tensile test,thermogravimetric analysis,morphology,differential scanning calorimetry,X-ray diffraction,antibacterial test,and oxygen and water vapor permeation test.The results showed that the crystallinity of HDPE was affected with the addition of GN-ZnO,and the nanocomposites had effective antibacterial capacity,strong mechanical properties,high thermal stability,and excellent barrier performance.This type of HDPE nanocomposites reinforced with GN-ZnO would be attractive for packaging industries.展开更多
Impact behavior of polymers has received considerable attention in recent years,and much work based on fracture mechanic approaches has been carried out.In this paper,fracture behavior in large deformation of a high d...Impact behavior of polymers has received considerable attention in recent years,and much work based on fracture mechanic approaches has been carried out.In this paper,fracture behavior in large deformation of a high density polyethylene(HDPE)materials was investigated through experimental impact testing on single edge notched specimen(SENB)and by using theoretical and analytical fracture criteria concepts.Moreover,a review of the main fracture criteria is given in order to characterize the toughness of this polymer in the both cases(static and dynamic).The fractured specimens obtained from the Charpy impact test were characterized with respect to their fracture surfaces.Characteristic zones of the fracture surface can be assigned to different stages and mechanisms of the fracture process.Finally,for a better understanding of fracture and damage mechanisms and to provide the best estimation of fracture toughness in impact,an experimental approach based on microscopic observations(SEM)was used.展开更多
High-density polyethylene(HDPE)film leakage location detection is frequently accomplished using the double-electrode technique.The electric potential and potential difference are the main physical parameters in the do...High-density polyethylene(HDPE)film leakage location detection is frequently accomplished using the double-electrode technique.The electric potential and potential difference are the main physical parameters in the double-electrode approach.Due to the impact of the complex geoelectric environment,the electric potential and the electric potential difference are not sensitive enough to respond to minimal leakage.The tiny leaking area cannot be precisely located using the electric potential and electric potential difference.Using the COMSOL Multiphysics software,this study created a standard geoelectric model of the double-electrode method.We calculated a new parameter—the G parameter through secondary electric potential difference—based on the response characteristics of the electric potential and the electric potential difference while the HDPEfilm is leaking.The experiment demonstrates that the G parameter is more sensitive than the electric potential and electric potential difference for detecting the leaking area of HDPE film.The G parameter is more effective at detecting leakage than the electric potential and electric potential difference.The results of this study can be used to locate HDPEfilm leakage areas in a landfill.展开更多
In this research,the tensile properties'performance of compression moulded discontinuous randomized zalacca fibre/high-density polyethylene under critical fibre length was analysed by means of experimental method ...In this research,the tensile properties'performance of compression moulded discontinuous randomized zalacca fibre/high-density polyethylene under critical fibre length was analysed by means of experimental method and micromechanical models.These investigations were used to verify the tensile properties models toward the effect of fibre length and volume fraction on the composites.The experimental results showed that the tensile properties of composites had significantly increased due to the enhancement of fibre length.On the contrary,a decline in the tensile properties was observed with the increase of volume fraction.A comparison was made between the available experimental results and the performances of Tsai-Pagano,Christensen and Cox-Krechel models in their prediction of composites elastic modulus.The results showed that the consideration of fibre's elastic anisotropy in the Cox-Krenchel model had yielded a good prediction of the composites modulus,nevertheless the models could not accurately predict the composites modulus for fibre length study.展开更多
Chemical processes are complex, for which traditional neural network models usually can not lead to satisfactory accuracy. Selective neural network ensemble is an effective way to enhance the generalization accuracy o...Chemical processes are complex, for which traditional neural network models usually can not lead to satisfactory accuracy. Selective neural network ensemble is an effective way to enhance the generalization accuracy of networks, but there are some problems, e.g., lacking of unified definition of diversity among component neural networks and difficult to improve the accuracy by selecting if the diversities of available networks are small. In this study, the output errors of networks are vectorized, the diversity of networks is defined based on the error vectors, and the size of ensemble is analyzed. Then an error vectorization based selective neural network ensemble (EVSNE) is proposed, in which the error vector of each network can offset that of the other networks by training the component networks orderly. Thus the component networks have large diversity. Experiments and comparisons over standard data sets and actual chemical process data set for production of high-density polyethylene demonstrate that EVSNE performs better in generalization ability.展开更多
Wood-plastic composite is an environmentally friendly material,due to its use of recycled thermoplastics and plant fibers.However,its surface lacks attractive aesthetic qualities.In this paper,a method of decorating w...Wood-plastic composite is an environmentally friendly material,due to its use of recycled thermoplastics and plant fibers.However,its surface lacks attractive aesthetic qualities.In this paper,a method of decorating wood fiber/high-density polyethylene(WF/HDPE)without adding adhesive was explored.Canvas or polyester fabrics were selected as the surface decoration materials.The influence of hot-pressing temperature and WF/HDPE ratio on the adhesion was studied.The surface bonding strength,water resistance,and surface color were evaluated,and observation within the infrared spectrum and under scanning electron microscopy was used to analyze the bonding process.The results showed that the fabric and WF/HDPE substrate could be closely laminated together depending on the HDPE layer accumulated on the WF/HDPE surface.The molten HDPE matrix penetrates canvas more easily than polyester fabric,and the canvasveneered composite shows a greater bonding strength than does the polyester fabric-veneered composite.A higher proportion of the thermoplastic component in the substrate improved the bonding.When the hot-pressing temperature exceeded 160°C,the fabric-veneered WF/HDPE panels had greater water resistance,although the canvas fabric changed more obviously in terms of fiber shape and color,compared with the polyester fabric.For the canvas fabric,140°C–160°C was a suitable hot-pressing temperature,whereas 160°C–180°C was more suitable for polyester fabric.The proportion of the thermoplastic component in the composite should be not less than 30%to achieve adequate bonding strength.展开更多
The rheological behavior of composites made with high-density polyethylene (HDPE) and different agro fiber by-products such as corncob (CCF), Rice hull (RHF), Flax shives (FSF) and Walnut shell (WSF) flour of 60 - 100...The rheological behavior of composites made with high-density polyethylene (HDPE) and different agro fiber by-products such as corncob (CCF), Rice hull (RHF), Flax shives (FSF) and Walnut shell (WSF) flour of 60 - 100 mesh were studied. The experimental results were obtained from samples containing 65 vol.% agro fiber and 3 wt.% lubricant. Particle sizes distribution of the agro fibers was in the range of 0.295 mm to ?0.125 mm. SEM showed evidence of complete matrix/fiber impregnation or wetting. The melt rheological data in terms of complex viscosity (η*), storage modulus (G'), loss modulus (G"), and loss tangent (tanδ) were evaluated and compared for different samples. Due to higher probability of agglomeration formation in the samples containing 65 vol.% of agro fillers, the storage modulus, loss modulus and complex viscosity of these samples were high. The unique change in all the samples is due to the particle size distribution of the agro fibers. The storage and loss modulus increased with increasing shear rates for all the composites, except for Walnut shell composite which exhibited unusual decrease in storage modulus with increasing shear rate. Damping factor (tanδ) decreased with increasing shear rate for all the composites at 65 vol.% filler load although there were differences among the composites. Maximum torque tended to increase at the 65 vol.% agro fiber load for all composites. Corncob and Walnut shell composites gave higher torque and steady state torque values in comparison with Flax shives and Rice hull composites due to differences in particle sizes distribution of the agro fibers.展开更多
In this work, the effect of Bentonite (Nanoclay) on the mechanical and mor-phology properties of HDPE/Nanoclay composite pipe material was investi-gated. This led to the development of a composite material with improv...In this work, the effect of Bentonite (Nanoclay) on the mechanical and mor-phology properties of HDPE/Nanoclay composite pipe material was investi-gated. This led to the development of a composite material with improved me-chanical properties. The HDPE/nanoclay composites were produced using an injection moulding machine at 200?C and rotor speed of 50 rpm. The compati-bilizer used in this study was Polyethylene-graft-Maleic Anhydride. Different compositions of nanoclay reinforcements were prepared and added to HDPE resin. A particle size of 425 μm was used in proportions of 0%, 5%, 10%, 15%, and 20% on weight fraction basis. All the composites samples were characterized by Zwick Roell tensile testing machine and Scanning Election Microscopy (SEM). Experimental results obtained showed improvements in the tensile strength, and modulus at the expense of elongation. The maximum tensile strength and modulus was obtained at 10% filler composition. These enhanced properties are due to the homogenous dispersion of nanoclay in HDPE matrix, which is evident from the structure that was evaluated using SEM.展开更多
In this study, high-density polyethylene (HDPE)/exfoliated graphite nanoplatelet (xGnP) composites reinforced with a 2 wt.% concentration of nano-magnesia (n-MgO) were fabricated using an injection moulding machine. T...In this study, high-density polyethylene (HDPE)/exfoliated graphite nanoplatelet (xGnP) composites reinforced with a 2 wt.% concentration of nano-magnesia (n-MgO) were fabricated using an injection moulding machine. The thermal properties and morphological structures of the composites were investigated. The XRD results showed the peaks of xGnP and n-MgO, where the intensity of the xGnP peaks became stronger with adding increasing amounts of xGnP into the polymermatrix. In terms of morphology, some agglomeration of particles was observed within the matrix, and the agglomeration decreased the thermal properties of the composites. The nanocomposites showed less thermal stability than the pristine polymer. The reduction in the onset temperature compared to that of neat HDPE was attributed to less adhesion between the fillers and the matrix. In addition, the crystallinity was reduced by the addition of fillers.展开更多
High-density polyethylene (HDPE) films were irradiated by 60Co gamma ray with a dose of 100 kGy in air and then immersed in aqueous solution of acrylic acid (AA) and sodium styrene sulfonate (SSS) at different tempera...High-density polyethylene (HDPE) films were irradiated by 60Co gamma ray with a dose of 100 kGy in air and then immersed in aqueous solution of acrylic acid (AA) and sodium styrene sulfonate (SSS) at different temperature. The effects of grafting conditions such as temperature, reaction time, Mohr’s salt concentration, and total concentration of monomer on grafting yield were studied. Both grafting yield of AA and SSS onto HDPE respectively increases with total concentration of monomers. The highest grafting yield was observed at 3 mol/L monomers where the grafted PE swelled to the largest extent in the monomers mixture. The grafting yield increases with reaction time and then levels off. At higher temperature, the grafting yield decreases with Mohr’s salt concentration, but increases at low temperature when Mohr’s salt concentration is 0.083%. Which can be interpreted that in the presence of Fe2+ diperoxides and hydroperoxides may decompose at low temperature to form radical which can initiate the grafting. The physical and chemical properties of grafting films were also investigated.展开更多
High-density poly-ethylene (HDPE) is a nonbiodegradable recyclable plastic which is widely utilized in single use packaging applications. Consequently, it constitutes a significant amount of plastic waste found in lan...High-density poly-ethylene (HDPE) is a nonbiodegradable recyclable plastic which is widely utilized in single use packaging applications. Consequently, it constitutes a significant amount of plastic waste found in landfills. From literature, it has been shown that parts produced using composites of HDPE with carbohydrate-based polymers, such as thermoplastic starch (TPS), experience mechanical degradation through hydrolytic degradation process. The possible utilization of recycled-HDPE (rHDPE) and TPS composite in nonconventional manufacturing processes such as Fused filament fabrication (FFF) has however not been explored. This study explores the potential application of rHDPE and TPS composites in FFF and optimizes the extrusion process parameters used in rHDPE-TPS filament production process. Taguchi method was utilized to analyze the extrusion process. The extrusion process parameters studied were the spooling speed, extrusion speed and the extrusion temperatures. The response variable studied was the filament diameter. In this research, the maximum TPS content achieved during filament production was 40 wt%. This filament was however challenging to use in FFF printers due to frequent nozzle clogging. Printing was therefore done with filaments that contained 0 - 30 wt% TPS. The experimental results showed that the most significant parameter in extrusion process was the spooling speed, followed by extrusion speed. Extrusion temperature had the least significant influence on the filament diameter. It was observed that increase in TPS content resulted in reduced warping and increased rate of hydrolytic degradation. Mechanical properties of printed parts were investigated and the results showed that increasing TPS content resulted in reduction in tensile strength, reduction in compression strength and increase in stiffness. The findings of this research provide valuable insights to plastic recycling industries and researchers regarding the utilization of recycled HDPE and TPS composites as substitute materials in FFF.展开更多
Dynamic melt modification of polyethylene via the direct grafting of peroxide fragments shows promise for the development of processable functionalized materials.In this study,four linear low-density polyethylenes(LLD...Dynamic melt modification of polyethylene via the direct grafting of peroxide fragments shows promise for the development of processable functionalized materials.In this study,four linear low-density polyethylenes(LLDPEs)with comparable molecular weights but different short-chain branch(SCB)contents(ranging of 5-66 per 1000 carbon atoms)were modified via dynamic melt mixing using 2 wt% benzoyl peroxide at 145℃ and 50 r/min for 30 min.The influence of SCB content on the processability and structure of the resulting products was systematically investigated.All modified products exhibited good melt processability with melt flow rates(MFR)ranging from 0.46 g/10min to 1.07 g/10min.Products derived from low-SCB LLDPEs showed a lower MFR,higher cross-linking content,a larger number of long-chain branches,and a higher degree of benzoyl grafting.In contrast,those produced from high-SCB LLDPEs exhibited improved processability,reduced cross-linking,fewer long-chain branches,and lower benzoyl grafting levels.A detailed structural investigation of the soluble and insoluble fractions,which were separated using trichlorobenzene fractionation,was conducted to analyze the structural features of various modified products and demonstrate that the SCB content(i.e.,tertiary carbon density)significantly influences radical coupling during dynamic modification.Elevated tertiary carbon density,by introducing greater steric hindrance,suppresses radical coupling during dynamic modification,thereby reducing the efficiency of both crosslinking and peroxide fragment grafting.These findings provide new insights into the structure-reactivity relationships in peroxide-induced polyethylene modification and lay the foundation for tailoring material properties via dynamic processing.展开更多
Osmotic energy,existing between the seawater and river water,is a renewable energy source,which can be directly converted into electricity by ion-exchange membranes(IEM).In traditional IEMs,the ion transport channels ...Osmotic energy,existing between the seawater and river water,is a renewable energy source,which can be directly converted into electricity by ion-exchange membranes(IEM).In traditional IEMs,the ion transport channels are formed by nanophase separation of hydrophilic ion carriers and hydrophobic segments.It is difficult to realize high-density ion channels with controlled spatial arrangement and length scale of ion carriers.Herein,we construct high-density 1D ion wires as transmission channels.Through molecular design,hydrophilic imidazole groups and hydrophobic alkyl tails were introduced into the repeat units,which self-assembled into 1D ion transporting core and protecting shell along the main chains.The areal density of the ionic wire arrays is up to~10^(12)cm^(-2),which is the highest value.The ionic wires ensure both high ion flux transport and high selectivity,achieving an ultrahigh-power density of 40.5 W m^(-2)at a 500-fold salinity gradient.Besides,the ionic wire array membrane is well recyclable and antibacterial.The ionic wires provide novel concept for next generation of high-performance membranes.展开更多
UHMWPE fibers exhibit impressive modulus and strength,but they have not reached their theoretical limits.Researchers focus on molecular weight,orientation,and crystallinity of UHMWPE,yet their contributions to mechani...UHMWPE fibers exhibit impressive modulus and strength,but they have not reached their theoretical limits.Researchers focus on molecular weight,orientation,and crystallinity of UHMWPE,yet their contributions to mechanical properties are unclear.Molecular dynamics simulations are valuable but often limited by computational constraints.Our aim is to simulate higher molecular weights to better represent real UHMWPE fibers.We used Packmol and Polyply methodologies to construct PE systems,with Polyply reproducing more reasonable properties of UHMWPE fibers.Additionally,tensile simulations showed that orientation and crystallinity greatly impact Young's modulus more than molecular weight.Energy decomposition indicated that higher molecular weights lead to covalent bonds that can withstand more energy during stretching,thus increasing breaking strength.Combining simulations with machine learning,we found that orientation has the most significant impact on Young's modulus,contributing 60%,and molecular weight plays the most crucial role in determining the breaking strength,accounting for 65%.This study provides a theoretical basis and guidelines for enhancing UHMWPE's modulus and strength.展开更多
Ultra-high molecular weight polyethylene(UHMWPE)is a key material for marine applications owing to its outstanding self-lubrication and corrosion resistance.However,its long-term performance is compromised by plastic ...Ultra-high molecular weight polyethylene(UHMWPE)is a key material for marine applications owing to its outstanding self-lubrication and corrosion resistance.However,its long-term performance is compromised by plastic deformation in seawater.In this study,we performed a comparative analysis of the UHMWPE dynamics under seawater and water conditions to investigate the plastic deformation of UHMWPE induced by seawater.The results show that the plastic deformation of UHMWPE is amplified in seawater relative to the water conditions.Under thin fluid conditions,frictional interfaces exhibit a higher interfacial friction force and interaction energy in seawater than in water.Compared to freely diffused water molecules,hydrated ions occupy larger interchain spaces within polyethylene.Furthermore,the diffusion of hydrated ions weakens the interchain interactions,promoting more severe polyethylene chain rearrangement and accelerating seawater-induced plastic deformation in UHMWPE during friction.Furthermore,the diffused seawater accelerated the disentangling of the polyethylene chains and enhanced the orderly orientation distribution of polyethylene.Compared to free water molecules,the water molecules of hydrated ions exhibit enhanced attraction to free-flowing water molecules,thereby accelerating seawater flow across submerged UHMWPE surfaces.This flow enhancement promotes surface polyethylene chain mobility in seawater.展开更多
Conventional polyethylene(PE)fibers face limitations in large-scale industrial applications due to their poor thermal stability and inherent hydrophobicity,which restrict processing temperatures and dyeability,especia...Conventional polyethylene(PE)fibers face limitations in large-scale industrial applications due to their poor thermal stability and inherent hydrophobicity,which restrict processing temperatures and dyeability,especially in blended fabric production.In this research,a one-step ultraviolet(UV)irradiation technology was employed to modify medium molecular weight PE fibers through simultaneous crosslinking and grafting modifications,aiming to enhance their thermal stability and hydrophilicity.The modification employed a cost-effective,UV-initiated crosslinking system consisting of benzophenone(BP)as the photoinitiator and triallyl isocyanurate(TAIC)as the cocrosslinker.Acrylic acid(AA)was selected as the grafting monomer.These modifiers were thoroughly mixed with the PE matrix in a liquid-phase environment,and the mixture was melt-spun into fibers.The resulting fibers were then subjected to UV irradiation,which triggered the crosslinking and grafting reactions.The effects of the mass fraction of each component and irradiation parameters on modification efficacy were systematically investigated,followed by a comprehensive characterization of the modified PE fibers.The modified PE fibers achieved optimal thermal stability under the following conditions:2.0%mass fractions for both BP and TAIC,a UV irradiation intensity of 2000 mW/cm^(2),and an equivalent irradiation time of 60 s.This synergistic modification approach enables the fibers to maintain superior morphological integrity and mechanical performance when exposed to elevated temperatures ranging from 130 to 150℃.Meanwhile,an AA grafting mass fraction of 2.0%maximizes hydrophilicity with minimal impact on other properties,as evidenced by a dramatic reduction in the water contact angle(WCA)from 105.0°(hydrophobic)to 48.4°(hydrophilic).These improvements confirm the effectiveness of the modification strategy in synergistically enhancing both thermal stability and hydrophilicity of PE fibers.展开更多
The form-stable paraffin/high-density polyethylene/expanded graphite/epoxy resin composite phase change materials(CPCMs),exhibiting suitable thermal properties,including low melting temperature,high conductivity and h...The form-stable paraffin/high-density polyethylene/expanded graphite/epoxy resin composite phase change materials(CPCMs),exhibiting suitable thermal properties,including low melting temperature,high conductivity and high phase change enthalpy,was developed in this work.Herein,paraffin(PA)was utilized as a core PCM.High-density polyethylene(HDPE)was utilized for the shape stabilization and preventing the PCMs leakage.Expanded graphite(EG)was used to increase its thermal conductivity and act also in the porous supporting material.Epoxy resin(ER)was used to provide flexible encapsulated scaffold morphology and keep a highly tight network structure of the PCMs.However,the physical architecture,the chemical architecture and thermal behavior properties of specimens were investigated by using the spectroscopy and calorimetry techniques.The scanning electron microscope(SEM),X-ray diffraction(XRD)and fourier transform infrared spectrometer FTIR tests have shown good uniformity structure and good compatibility of components.In addition,the thermal conductivity tests revealed that the thermal conductivity of PA,initially 0.31 W/(m·K)improved up to 1.9 times by adding the 6 wt%mass fraction of EG in composite PCMs.Furthermore,the differential scanning calorimeter(DSC)measurements indicated that PA melting enthalpy,initially 231 J/g decreased up to 125 J/g with the increase of the amount of HDPE which was due to the limitation caused by the atomic network constructed by the base material.The thermogravimetric analyzer(TGA)and leakage-proof revealed the enhancement of the degradation of PA with the raise of amount of the HDPE into the CPCMs.Therefore,the proposed form-stable CPCMs are a great candidate for the thermal regulation and thermal energy storage employment.展开更多
Crack opening displacement(COD) was applied to characterize the fracture initiation of the tough high density polyethylene. Normal single side notched three point bend specimens and silica rubber replica techniques ...Crack opening displacement(COD) was applied to characterize the fracture initiation of the tough high density polyethylene. Normal single side notched three point bend specimens and silica rubber replica techniques were used to study the characteristic COD of high density polyethylene pipe and its butt fusion joints including the weld fusion zone and heat affected zone at different temperature from -78 ℃ to 20 ℃ . Testing results show that the characteristic COD appears to depend on the structural features that are determined by welding process and the testing temperature. As the temperature is lowered, the characteristic COD of all zones studied decreases. Because the welding process significantly changes some structural feature of the material, characteristic COD of the weld fusion zone is the smallest one among those of the three zones. The results can be used for the engineering design and failure analysis of HDPE pipe.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52373045 and 52033005).
文摘In rotationally extruded fittings,high-density polyethylene(HDPE)pipes prepared using conventional processing methods often suffer from poor pressure resistance and low toughness.This study introduces an innovative rotary shear system(RSS)to address these deficiencies through controlled mandrel rotation and cooling rates.We successfully prepared self-reinforced HDPE pipes with a three-layer structure combining spherical and shish-kebab crystals.Rotational processing aligned the molecular chains in the ring direction and formed shish-kebab crystals.As a result,the annular tensile strength of the rotationally processed three-layer shish-kebab structure(TSK)pipe increased from 26.7 MPa to 76.3 MPa,an enhancement of 185.8%.Notably,while maintaining excellent tensile strength(73.4 MPa),the elongation at break of the spherulite shishkebab spherulite(SKS)tubes was improved to 50.1%,as compared to 33.8%in the case of shish-kebab spherulite shish-kebab(KSK)tubes.This improvement can be attributed to the changes in the micro-morphology and polymer structure within the SKS tubes,specifically due to the formation of small-sized shish-kebab crystals and the low degrees of interlocking.In addition,2D-SAXS analysis revealed that KSK tubes have higher tensile strength due to smaller crystal sizes and larger shish dimensions,forming dense interlocking structures.In contrast,the SKS and TSK tubes had thicker amorphous regions and smaller shish sizes,resulting in reduced interlocking and mechanical performance.
基金the Deanship of Scientific Research at King Saud University for funding the work through the research group project No.RGP-VPP-133
文摘The objective of this work is to demonstrate how the viscoelastic, thermal, rheological, hardness, wear resistance and fracture behavior of bioinert high-density polyethylene （HDPE） can be changed by the addition of hydroxyapatite （HAP） nano particles. Also the effects of accelerated thermal ageing on the composite properties have been investigated. Different weight fractions of HAP nano particles up to 30 wt% have been incorporated in HDPE matrix by using melt blending in co-rotating intermeshing twin screw extruder. The fracture toughness results showed a remarkable decrease in proportion to the HAP content. The differential scanning calorimetry results indicated that the melting temperature and crystallinity were affected by the addition of HAP nano particles into the matrix. The complex viscosity increased as the percentage of HAP increased due to the restriction of the molecular mobility. The dynamic mechanical analysis results revealed that higher storage modulus （8.3 1011 Pa） could be obtained in the developed HDPE/HAP in 30 wt% compared to neat HDPE （5.1 1011 Pa）. Finally, the hardness and wear resistance of HDPE were improved significantly due to the addition of HAP nano particles. The changes in the HDPE and its nano composite properties due to ageing showed that the HDPE and its nano composites crystallinity increased while the fracture toughness, hardness, wear resistance, storage and loss modulus decreased.
基金The authors would like to acknowledge the financial support from the following organizations:Wuliangye Group Co.,Ltd.(No.CXY2019ZR001)Sichuan Province Science and Technology Support Program(No.2019JDRC0029)+2 种基金Zigong City Science and Technology(Nos.2017XC16,2019CXRC01)Opening Project of Material Corrosion and Protection Key Laboratory of Sichuan Province(Nos.2016CL10,2017CL03,2019CL05,2018CL08,2018CL07)Opening Project of Sichuan Province,the Foundation of Introduced Talent of Sichuan University of Science and Engineering(Nos.2014RC31,2017RCL31,2017RCL36,2017RCL16,2019RC05,2019RC07).Appreciation is also extended to Apex Nanotek Co.,Ltd.
文摘Nanocomposites of high-density polyethylene(HDPE)modified with 0.2 phr graphene-zinc oxide(GN-ZnO)exhibited optimal mechanical properties and thermal stability.Two other nano-materials—GN and nano-ZnO—were also used to compare them with GN-ZnO.increasing the content of GN-ZnO gradually enhanced the antibacterial and barrier properties,but the addition of 0.3 phr GN-ZnO led to agglomeration that caused defects in the nanocomposites.Herein,we investigated the antibacterial and barrier properties of HDPE nanocomposites infused with different nanoparticles(GN,ZnO,GN-ZnO)of varying concentrations.HDPE and the nanoparticles were meltblended together in a Haake-Buchler Rheomixer to produce a new environment-friendly nano-material with improved physical and chemical properties.The following characterizations were conducted:tensile test,thermogravimetric analysis,morphology,differential scanning calorimetry,X-ray diffraction,antibacterial test,and oxygen and water vapor permeation test.The results showed that the crystallinity of HDPE was affected with the addition of GN-ZnO,and the nanocomposites had effective antibacterial capacity,strong mechanical properties,high thermal stability,and excellent barrier performance.This type of HDPE nanocomposites reinforced with GN-ZnO would be attractive for packaging industries.
文摘Impact behavior of polymers has received considerable attention in recent years,and much work based on fracture mechanic approaches has been carried out.In this paper,fracture behavior in large deformation of a high density polyethylene(HDPE)materials was investigated through experimental impact testing on single edge notched specimen(SENB)and by using theoretical and analytical fracture criteria concepts.Moreover,a review of the main fracture criteria is given in order to characterize the toughness of this polymer in the both cases(static and dynamic).The fractured specimens obtained from the Charpy impact test were characterized with respect to their fracture surfaces.Characteristic zones of the fracture surface can be assigned to different stages and mechanisms of the fracture process.Finally,for a better understanding of fracture and damage mechanisms and to provide the best estimation of fracture toughness in impact,an experimental approach based on microscopic observations(SEM)was used.
基金supported by the National Key Research and Development Program of China (Grant Nos. 2019YFC1510802 and 2019YFC1804302)the National Natural Science Foundation of China (Grant No. 41504081)the Fundamental Research Funds for the Central Universities (Grant No. 2019B17214)。
文摘High-density polyethylene(HDPE)film leakage location detection is frequently accomplished using the double-electrode technique.The electric potential and potential difference are the main physical parameters in the double-electrode approach.Due to the impact of the complex geoelectric environment,the electric potential and the electric potential difference are not sensitive enough to respond to minimal leakage.The tiny leaking area cannot be precisely located using the electric potential and electric potential difference.Using the COMSOL Multiphysics software,this study created a standard geoelectric model of the double-electrode method.We calculated a new parameter—the G parameter through secondary electric potential difference—based on the response characteristics of the electric potential and the electric potential difference while the HDPEfilm is leaking.The experiment demonstrates that the G parameter is more sensitive than the electric potential and electric potential difference for detecting the leaking area of HDPE film.The G parameter is more effective at detecting leakage than the electric potential and electric potential difference.The results of this study can be used to locate HDPEfilm leakage areas in a landfill.
文摘In this research,the tensile properties'performance of compression moulded discontinuous randomized zalacca fibre/high-density polyethylene under critical fibre length was analysed by means of experimental method and micromechanical models.These investigations were used to verify the tensile properties models toward the effect of fibre length and volume fraction on the composites.The experimental results showed that the tensile properties of composites had significantly increased due to the enhancement of fibre length.On the contrary,a decline in the tensile properties was observed with the increase of volume fraction.A comparison was made between the available experimental results and the performances of Tsai-Pagano,Christensen and Cox-Krechel models in their prediction of composites elastic modulus.The results showed that the consideration of fibre's elastic anisotropy in the Cox-Krenchel model had yielded a good prediction of the composites modulus,nevertheless the models could not accurately predict the composites modulus for fibre length study.
基金Supported by the National Natural Science Foundation of China (61074153, 61104131)the Fundamental Research Fundsfor Central Universities of China (ZY1111, JD1104)
文摘Chemical processes are complex, for which traditional neural network models usually can not lead to satisfactory accuracy. Selective neural network ensemble is an effective way to enhance the generalization accuracy of networks, but there are some problems, e.g., lacking of unified definition of diversity among component neural networks and difficult to improve the accuracy by selecting if the diversities of available networks are small. In this study, the output errors of networks are vectorized, the diversity of networks is defined based on the error vectors, and the size of ensemble is analyzed. Then an error vectorization based selective neural network ensemble (EVSNE) is proposed, in which the error vector of each network can offset that of the other networks by training the component networks orderly. Thus the component networks have large diversity. Experiments and comparisons over standard data sets and actual chemical process data set for production of high-density polyethylene demonstrate that EVSNE performs better in generalization ability.
基金supported by the National Natural Science Foundation of China[31670573]the Innovation Training Program of Northeast Forestry University[201810225398].
文摘Wood-plastic composite is an environmentally friendly material,due to its use of recycled thermoplastics and plant fibers.However,its surface lacks attractive aesthetic qualities.In this paper,a method of decorating wood fiber/high-density polyethylene(WF/HDPE)without adding adhesive was explored.Canvas or polyester fabrics were selected as the surface decoration materials.The influence of hot-pressing temperature and WF/HDPE ratio on the adhesion was studied.The surface bonding strength,water resistance,and surface color were evaluated,and observation within the infrared spectrum and under scanning electron microscopy was used to analyze the bonding process.The results showed that the fabric and WF/HDPE substrate could be closely laminated together depending on the HDPE layer accumulated on the WF/HDPE surface.The molten HDPE matrix penetrates canvas more easily than polyester fabric,and the canvasveneered composite shows a greater bonding strength than does the polyester fabric-veneered composite.A higher proportion of the thermoplastic component in the substrate improved the bonding.When the hot-pressing temperature exceeded 160°C,the fabric-veneered WF/HDPE panels had greater water resistance,although the canvas fabric changed more obviously in terms of fiber shape and color,compared with the polyester fabric.For the canvas fabric,140°C–160°C was a suitable hot-pressing temperature,whereas 160°C–180°C was more suitable for polyester fabric.The proportion of the thermoplastic component in the composite should be not less than 30%to achieve adequate bonding strength.
文摘The rheological behavior of composites made with high-density polyethylene (HDPE) and different agro fiber by-products such as corncob (CCF), Rice hull (RHF), Flax shives (FSF) and Walnut shell (WSF) flour of 60 - 100 mesh were studied. The experimental results were obtained from samples containing 65 vol.% agro fiber and 3 wt.% lubricant. Particle sizes distribution of the agro fibers was in the range of 0.295 mm to ?0.125 mm. SEM showed evidence of complete matrix/fiber impregnation or wetting. The melt rheological data in terms of complex viscosity (η*), storage modulus (G'), loss modulus (G"), and loss tangent (tanδ) were evaluated and compared for different samples. Due to higher probability of agglomeration formation in the samples containing 65 vol.% of agro fillers, the storage modulus, loss modulus and complex viscosity of these samples were high. The unique change in all the samples is due to the particle size distribution of the agro fibers. The storage and loss modulus increased with increasing shear rates for all the composites, except for Walnut shell composite which exhibited unusual decrease in storage modulus with increasing shear rate. Damping factor (tanδ) decreased with increasing shear rate for all the composites at 65 vol.% filler load although there were differences among the composites. Maximum torque tended to increase at the 65 vol.% agro fiber load for all composites. Corncob and Walnut shell composites gave higher torque and steady state torque values in comparison with Flax shives and Rice hull composites due to differences in particle sizes distribution of the agro fibers.
文摘In this work, the effect of Bentonite (Nanoclay) on the mechanical and mor-phology properties of HDPE/Nanoclay composite pipe material was investi-gated. This led to the development of a composite material with improved me-chanical properties. The HDPE/nanoclay composites were produced using an injection moulding machine at 200?C and rotor speed of 50 rpm. The compati-bilizer used in this study was Polyethylene-graft-Maleic Anhydride. Different compositions of nanoclay reinforcements were prepared and added to HDPE resin. A particle size of 425 μm was used in proportions of 0%, 5%, 10%, 15%, and 20% on weight fraction basis. All the composites samples were characterized by Zwick Roell tensile testing machine and Scanning Election Microscopy (SEM). Experimental results obtained showed improvements in the tensile strength, and modulus at the expense of elongation. The maximum tensile strength and modulus was obtained at 10% filler composition. These enhanced properties are due to the homogenous dispersion of nanoclay in HDPE matrix, which is evident from the structure that was evaluated using SEM.
文摘In this study, high-density polyethylene (HDPE)/exfoliated graphite nanoplatelet (xGnP) composites reinforced with a 2 wt.% concentration of nano-magnesia (n-MgO) were fabricated using an injection moulding machine. The thermal properties and morphological structures of the composites were investigated. The XRD results showed the peaks of xGnP and n-MgO, where the intensity of the xGnP peaks became stronger with adding increasing amounts of xGnP into the polymermatrix. In terms of morphology, some agglomeration of particles was observed within the matrix, and the agglomeration decreased the thermal properties of the composites. The nanocomposites showed less thermal stability than the pristine polymer. The reduction in the onset temperature compared to that of neat HDPE was attributed to less adhesion between the fillers and the matrix. In addition, the crystallinity was reduced by the addition of fillers.
文摘High-density polyethylene (HDPE) films were irradiated by 60Co gamma ray with a dose of 100 kGy in air and then immersed in aqueous solution of acrylic acid (AA) and sodium styrene sulfonate (SSS) at different temperature. The effects of grafting conditions such as temperature, reaction time, Mohr’s salt concentration, and total concentration of monomer on grafting yield were studied. Both grafting yield of AA and SSS onto HDPE respectively increases with total concentration of monomers. The highest grafting yield was observed at 3 mol/L monomers where the grafted PE swelled to the largest extent in the monomers mixture. The grafting yield increases with reaction time and then levels off. At higher temperature, the grafting yield decreases with Mohr’s salt concentration, but increases at low temperature when Mohr’s salt concentration is 0.083%. Which can be interpreted that in the presence of Fe2+ diperoxides and hydroperoxides may decompose at low temperature to form radical which can initiate the grafting. The physical and chemical properties of grafting films were also investigated.
文摘High-density poly-ethylene (HDPE) is a nonbiodegradable recyclable plastic which is widely utilized in single use packaging applications. Consequently, it constitutes a significant amount of plastic waste found in landfills. From literature, it has been shown that parts produced using composites of HDPE with carbohydrate-based polymers, such as thermoplastic starch (TPS), experience mechanical degradation through hydrolytic degradation process. The possible utilization of recycled-HDPE (rHDPE) and TPS composite in nonconventional manufacturing processes such as Fused filament fabrication (FFF) has however not been explored. This study explores the potential application of rHDPE and TPS composites in FFF and optimizes the extrusion process parameters used in rHDPE-TPS filament production process. Taguchi method was utilized to analyze the extrusion process. The extrusion process parameters studied were the spooling speed, extrusion speed and the extrusion temperatures. The response variable studied was the filament diameter. In this research, the maximum TPS content achieved during filament production was 40 wt%. This filament was however challenging to use in FFF printers due to frequent nozzle clogging. Printing was therefore done with filaments that contained 0 - 30 wt% TPS. The experimental results showed that the most significant parameter in extrusion process was the spooling speed, followed by extrusion speed. Extrusion temperature had the least significant influence on the filament diameter. It was observed that increase in TPS content resulted in reduced warping and increased rate of hydrolytic degradation. Mechanical properties of printed parts were investigated and the results showed that increasing TPS content resulted in reduction in tensile strength, reduction in compression strength and increase in stiffness. The findings of this research provide valuable insights to plastic recycling industries and researchers regarding the utilization of recycled HDPE and TPS composites as substitute materials in FFF.
基金financially supported by the Science and Technology Project of PetroChina Company Limited,China(No.2022DJ6314)the National Natural Science Foundation of China(No.52173056)。
文摘Dynamic melt modification of polyethylene via the direct grafting of peroxide fragments shows promise for the development of processable functionalized materials.In this study,four linear low-density polyethylenes(LLDPEs)with comparable molecular weights but different short-chain branch(SCB)contents(ranging of 5-66 per 1000 carbon atoms)were modified via dynamic melt mixing using 2 wt% benzoyl peroxide at 145℃ and 50 r/min for 30 min.The influence of SCB content on the processability and structure of the resulting products was systematically investigated.All modified products exhibited good melt processability with melt flow rates(MFR)ranging from 0.46 g/10min to 1.07 g/10min.Products derived from low-SCB LLDPEs showed a lower MFR,higher cross-linking content,a larger number of long-chain branches,and a higher degree of benzoyl grafting.In contrast,those produced from high-SCB LLDPEs exhibited improved processability,reduced cross-linking,fewer long-chain branches,and lower benzoyl grafting levels.A detailed structural investigation of the soluble and insoluble fractions,which were separated using trichlorobenzene fractionation,was conducted to analyze the structural features of various modified products and demonstrate that the SCB content(i.e.,tertiary carbon density)significantly influences radical coupling during dynamic modification.Elevated tertiary carbon density,by introducing greater steric hindrance,suppresses radical coupling during dynamic modification,thereby reducing the efficiency of both crosslinking and peroxide fragment grafting.These findings provide new insights into the structure-reactivity relationships in peroxide-induced polyethylene modification and lay the foundation for tailoring material properties via dynamic processing.
基金financially supported by the Key R&D Program of Shandong Province(2022SFGC0801)the National Natural Science Foundation of China(No.22005162 and 22175009)the Natural Science Foundation of Shandong Province(No.ZR2020QE093)。
文摘Osmotic energy,existing between the seawater and river water,is a renewable energy source,which can be directly converted into electricity by ion-exchange membranes(IEM).In traditional IEMs,the ion transport channels are formed by nanophase separation of hydrophilic ion carriers and hydrophobic segments.It is difficult to realize high-density ion channels with controlled spatial arrangement and length scale of ion carriers.Herein,we construct high-density 1D ion wires as transmission channels.Through molecular design,hydrophilic imidazole groups and hydrophobic alkyl tails were introduced into the repeat units,which self-assembled into 1D ion transporting core and protecting shell along the main chains.The areal density of the ionic wire arrays is up to~10^(12)cm^(-2),which is the highest value.The ionic wires ensure both high ion flux transport and high selectivity,achieving an ultrahigh-power density of 40.5 W m^(-2)at a 500-fold salinity gradient.Besides,the ionic wire array membrane is well recyclable and antibacterial.The ionic wires provide novel concept for next generation of high-performance membranes.
基金financially supported by the National Natural Science Foundation of China(Nos.52303298 and 52233002)。
文摘UHMWPE fibers exhibit impressive modulus and strength,but they have not reached their theoretical limits.Researchers focus on molecular weight,orientation,and crystallinity of UHMWPE,yet their contributions to mechanical properties are unclear.Molecular dynamics simulations are valuable but often limited by computational constraints.Our aim is to simulate higher molecular weights to better represent real UHMWPE fibers.We used Packmol and Polyply methodologies to construct PE systems,with Polyply reproducing more reasonable properties of UHMWPE fibers.Additionally,tensile simulations showed that orientation and crystallinity greatly impact Young's modulus more than molecular weight.Energy decomposition indicated that higher molecular weights lead to covalent bonds that can withstand more energy during stretching,thus increasing breaking strength.Combining simulations with machine learning,we found that orientation has the most significant impact on Young's modulus,contributing 60%,and molecular weight plays the most crucial role in determining the breaking strength,accounting for 65%.This study provides a theoretical basis and guidelines for enhancing UHMWPE's modulus and strength.
基金financially supported by the National Natural Science Foundation of China(Nos.51909023 and 51775077)the Natural Science Foundation of Liaoning Province(No.2021-MS-140)the Fundamental Research Funds for the Central Universities(No.3132025114)。
文摘Ultra-high molecular weight polyethylene(UHMWPE)is a key material for marine applications owing to its outstanding self-lubrication and corrosion resistance.However,its long-term performance is compromised by plastic deformation in seawater.In this study,we performed a comparative analysis of the UHMWPE dynamics under seawater and water conditions to investigate the plastic deformation of UHMWPE induced by seawater.The results show that the plastic deformation of UHMWPE is amplified in seawater relative to the water conditions.Under thin fluid conditions,frictional interfaces exhibit a higher interfacial friction force and interaction energy in seawater than in water.Compared to freely diffused water molecules,hydrated ions occupy larger interchain spaces within polyethylene.Furthermore,the diffusion of hydrated ions weakens the interchain interactions,promoting more severe polyethylene chain rearrangement and accelerating seawater-induced plastic deformation in UHMWPE during friction.Furthermore,the diffused seawater accelerated the disentangling of the polyethylene chains and enhanced the orderly orientation distribution of polyethylene.Compared to free water molecules,the water molecules of hydrated ions exhibit enhanced attraction to free-flowing water molecules,thereby accelerating seawater flow across submerged UHMWPE surfaces.This flow enhancement promotes surface polyethylene chain mobility in seawater.
文摘Conventional polyethylene(PE)fibers face limitations in large-scale industrial applications due to their poor thermal stability and inherent hydrophobicity,which restrict processing temperatures and dyeability,especially in blended fabric production.In this research,a one-step ultraviolet(UV)irradiation technology was employed to modify medium molecular weight PE fibers through simultaneous crosslinking and grafting modifications,aiming to enhance their thermal stability and hydrophilicity.The modification employed a cost-effective,UV-initiated crosslinking system consisting of benzophenone(BP)as the photoinitiator and triallyl isocyanurate(TAIC)as the cocrosslinker.Acrylic acid(AA)was selected as the grafting monomer.These modifiers were thoroughly mixed with the PE matrix in a liquid-phase environment,and the mixture was melt-spun into fibers.The resulting fibers were then subjected to UV irradiation,which triggered the crosslinking and grafting reactions.The effects of the mass fraction of each component and irradiation parameters on modification efficacy were systematically investigated,followed by a comprehensive characterization of the modified PE fibers.The modified PE fibers achieved optimal thermal stability under the following conditions:2.0%mass fractions for both BP and TAIC,a UV irradiation intensity of 2000 mW/cm^(2),and an equivalent irradiation time of 60 s.This synergistic modification approach enables the fibers to maintain superior morphological integrity and mechanical performance when exposed to elevated temperatures ranging from 130 to 150℃.Meanwhile,an AA grafting mass fraction of 2.0%maximizes hydrophilicity with minimal impact on other properties,as evidenced by a dramatic reduction in the water contact angle(WCA)from 105.0°(hydrophobic)to 48.4°(hydrophilic).These improvements confirm the effectiveness of the modification strategy in synergistically enhancing both thermal stability and hydrophilicity of PE fibers.
基金This research was financially supported by the National Natural Science Foundation of China(52206087,52130607)the Natural Science Foundation of Gansu Province,China(20JR10RA193)+2 种基金the Industrial Support Plan Project of Gansu Provincial Education Department(2022CYZC-21,2021CYZC-27)the Doctoral Research Funds of Lanzhou University of Technology(061907)the Red Willow Excellent Youth Project of Lanzhou University of Technology.
文摘The form-stable paraffin/high-density polyethylene/expanded graphite/epoxy resin composite phase change materials(CPCMs),exhibiting suitable thermal properties,including low melting temperature,high conductivity and high phase change enthalpy,was developed in this work.Herein,paraffin(PA)was utilized as a core PCM.High-density polyethylene(HDPE)was utilized for the shape stabilization and preventing the PCMs leakage.Expanded graphite(EG)was used to increase its thermal conductivity and act also in the porous supporting material.Epoxy resin(ER)was used to provide flexible encapsulated scaffold morphology and keep a highly tight network structure of the PCMs.However,the physical architecture,the chemical architecture and thermal behavior properties of specimens were investigated by using the spectroscopy and calorimetry techniques.The scanning electron microscope(SEM),X-ray diffraction(XRD)and fourier transform infrared spectrometer FTIR tests have shown good uniformity structure and good compatibility of components.In addition,the thermal conductivity tests revealed that the thermal conductivity of PA,initially 0.31 W/(m·K)improved up to 1.9 times by adding the 6 wt%mass fraction of EG in composite PCMs.Furthermore,the differential scanning calorimeter(DSC)measurements indicated that PA melting enthalpy,initially 231 J/g decreased up to 125 J/g with the increase of the amount of HDPE which was due to the limitation caused by the atomic network constructed by the base material.The thermogravimetric analyzer(TGA)and leakage-proof revealed the enhancement of the degradation of PA with the raise of amount of the HDPE into the CPCMs.Therefore,the proposed form-stable CPCMs are a great candidate for the thermal regulation and thermal energy storage employment.
文摘Crack opening displacement(COD) was applied to characterize the fracture initiation of the tough high density polyethylene. Normal single side notched three point bend specimens and silica rubber replica techniques were used to study the characteristic COD of high density polyethylene pipe and its butt fusion joints including the weld fusion zone and heat affected zone at different temperature from -78 ℃ to 20 ℃ . Testing results show that the characteristic COD appears to depend on the structural features that are determined by welding process and the testing temperature. As the temperature is lowered, the characteristic COD of all zones studied decreases. Because the welding process significantly changes some structural feature of the material, characteristic COD of the weld fusion zone is the smallest one among those of the three zones. The results can be used for the engineering design and failure analysis of HDPE pipe.
