In this work,the lamellar structural evolution and microvoids variations of βpolypropylene(β-PP)during the processing of two different stretching methods,sequential biaxial stretching and simultaneous biaxial stretc...In this work,the lamellar structural evolution and microvoids variations of βpolypropylene(β-PP)during the processing of two different stretching methods,sequential biaxial stretching and simultaneous biaxial stretching,were investigated in detail.It was found that different stretching methods led to significantly different lamellae deformation modes,and the microporous membranes obtained from the simultaneous biaxial stretching exhibited better mechanical properties.For the sequential biaxial stretching,abundant coarse fibers originated from the tight accumulation of the lamellae parallel to the longitudinal stretching direction,whereas the lamellae perpendicular to the stretching direction were easily deformed and separated.Those coarse fibers were difficult to be separated to form micropores during the subsequent transverse stretching process,resulting in a poor micropores distribution.However,for the simultaneous biaxial stretching,theβcrystal had the same deformation mode,that is,the lamellae distributed in different directions were all destroyed,forming abundant microvoids and little coarse fibers.展开更多
To compare the suitable working conditions of polypropylene(PP)and polycaprolactam(PA6)materials in actual use in automobiles,the effects of different temperature aging and different reagents on the mechanical propert...To compare the suitable working conditions of polypropylene(PP)and polycaprolactam(PA6)materials in actual use in automobiles,the effects of different temperature aging and different reagents on the mechanical properties of the two materials,such as tensile,bending,compression,and impact were studied.The results indicate that the short⁃term low⁃temperature environment had no much effect on the mechanical properties of PP and PA6.After long⁃term thermal aging at 80℃,the strength of PP and PA6 increased while their toughness decreased.After short⁃term thermal aging at 120℃,PP strength decreases and toughness increases,while PA6 strength increases and toughness decreases.The soaking of glass water and car shampoo had no much effect on the mechanical properties of PP,but had a significant impact on the mechanical properties of PA6.With the increase of soaking time,the strength of PA6 significantly decreases and the toughness significantly increases.The soaking of 95#gasoline had no much effect on the mechanical properties of PA6,but has a significant impact on the mechanical properties of PP.After 720 h of soaking,the retention rates of the tensile strength,bending strength,and compressive strength of PP were all less than 80%,while the retention rate of the impact strength of the cantilever beam was 160.4%.展开更多
The performance of polypropylene film determines the reliability of capacitors.This paper studies the change of insulation characteristics of the insulation dielectric polypropylene of high-voltage capacitors during t...The performance of polypropylene film determines the reliability of capacitors.This paper studies the change of insulation characteristics of the insulation dielectric polypropylene of high-voltage capacitors during the long-term operation process.Moreover,the correction of the insulation failure model of polypropylene media is implemented.Some conclusions are drawn from a series of experiments.The breakdown strength of the insulation dielectrics decreases as the withstand time rises,with amaximum decrease of 37.91%compared to the polypropylene sample without withstand voltage.As the electric field increases from−20 to−100 kV/mm,the total amount of space charge,the trap energy level and the trap density inside the polypropylene increase by 524.15%,18.99%and 773.36%,respectively.In the capacitor simulation model,the electric field in the capacitor increases by 19.62%after presetting space charge relative to the nonspace charge.The experimental data are substituted into the inverse power model,and the trap parameters are used to modify the model.The results show that the ageing state of the polypropylene has a negative exponential relationship with the trap parameters.This paper provides an important reference for the study of the failure mechanism of polypropylene in high-voltage capacitors and the assessment of polypropylene ageing state.展开更多
A novel eco-friendly charring agent(L-OH)was successfully synthesized by combining pentaerythritol(PER)with lignin through a simple two-step reaction.The structure of L-OH was characterized using Fourier transform inf...A novel eco-friendly charring agent(L-OH)was successfully synthesized by combining pentaerythritol(PER)with lignin through a simple two-step reaction.The structure of L-OH was characterized using Fourier transform infrared(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM)and EDS.In addition,L-OH was introduced into polypropylene(PP)together with melamine(MEL)and ammonium polyphosphate(APP)as an intumescent flame retardant(IFRR).The flame retardancy of PP/IFRR composites were investigated using limited oxygen index(LOI),UL-94,thermogravimetric analysis(TGA)and cone calorimeter(CC)test.The experimental results indicate that the PP/IFRR composites pass the V-0 grade of the UL-94 test when the addition amount of IFRR is no less than 20%,and the LOI value of the composite reaches 32.2%at 30%IFRR addition.The peak heat release rate(PHRR)and peak smoke production rate(PSPR)of the composite decrease by 72.8%and 70.4%compared with pure PP,respectively.The flame retardancy mechanism was investigated by TGA,TG-FTIR and residual carbon analysis.These analyses indicate that L-OH can form a more continuous and dense carbon layer during the combustion process,which is the main factor contributing to the improved flame retardancy of PP.展开更多
A comparative study of products of thermal and thermocatalytic cracking of polypropylene(PP) in the presence of potassium polytitanate(PPT) synthesized by treatment of TiO_(2)(rutile) powder with molten mixture of KOH...A comparative study of products of thermal and thermocatalytic cracking of polypropylene(PP) in the presence of potassium polytitanate(PPT) synthesized by treatment of TiO_(2)(rutile) powder with molten mixture of KOH and KNO_(3) taken in a weight ratio of 30∶30∶40 has been carried out.It was shown that the studied type of PPT powder exhibits catalytic properties in the reaction of thermal decomposition of PP,compared to the effect of commercial zeolite catalyst CBV-780 traditionally used for this purpose.Based on the analysis performed,the differences in the mechanism of catalytic action of PPT and the zeolite were considered.The reasons for the observed differences in the composition of PP cracking products and in the rate of coke formation on the surface of studied catalysts were analyzed.Considering the obtained results,it has been proposed that the CBV-780 catalyst promoted more intensive production of the gaseous hydrocarbons compared to PPT,due to higher specific surface area(internal surface) accessible for relatively light and small-sized hydrocarbon products of cracking.However,intensive coke formation on the outer surface of the microporous zeolite contributes to the blocking of transport channels and the rapid loss of catalytic action.At the same time,PPT,which initially has a smaller specific surface area,retains its catalytic activity significantly longer due to slit-shaped flat pores and higher transport accessibility of the inner surface.展开更多
The present study presents an assessment of the interrelations between long-chain branching,specific nucleation,and end-use properties of polypropylene blends:blends of linear polypropylene(L-PP)and long-chain branche...The present study presents an assessment of the interrelations between long-chain branching,specific nucleation,and end-use properties of polypropylene blends:blends of linear polypropylene(L-PP)and long-chain branched polypropylene(LCB-PP)modified by a specificβ-nucleating agent(NA).Specimens with various LCB-PP compositions with and without NA were prepared under complex flow fields by injection molding.Wide-angle X-ray scattering was employed to capture the X-ray patterns of both the skin and core of the specimens,determining the overall crystallinity and amounts of individual polymorphs.The increasing content of LCB-PP andγ-phase,at the same time,in the blends is reflected in both increasing crystallinity and improved mechanical properties,namely,yield stress and Young’s modulus.On the other hand,the composition of the blends had no significant effect on the impact strength,except for nucleated L-PP.It has been demonstrated that adding a relatively small amount of LCB-PP is sufficient to modify the mechanical properties of linear polypropylene.Even a very small amount of LCB-PP in the L-PP suppressed the effectiveness of NA.展开更多
Geological samples often contain significant amounts of iron,which,although not typically the target element,can substantially interfere with the analysis of other elements of interest.To mitigate these interferences,...Geological samples often contain significant amounts of iron,which,although not typically the target element,can substantially interfere with the analysis of other elements of interest.To mitigate these interferences,amidoximebased radiation grafted adsorbents have been identified as effective for iron removal.In this study,an amidoximefunctionalized,radiation-grafted adsorbent synthesized from polypropylene waste(PPw-g-AO-10)was employed to remove iron from leached geological samples.The adsorption process was systematically optimized by investigating the effects of pH,contact time,adsorbent dosage,and initial ferric ion concentration.Under optimal conditions-pH1.4,a contact time of 90 min,and an initial ferric ion concentration of 4500 mg/L-the adsorbent exhibited a maximum iron adsorption capacity of 269.02 mg/g.After optimizing the critical adsorption parameters,the adsorbent was applied to the leached geological samples,achieving a 91%removal of the iron content.The adsorbent was regenerated through two consecutive cycles using 0.2 N HNO_(3),achieving a regeneration efficiency of 65%.These findings confirm the efficacy of the synthesized PPw-g-AO-10 as a cost-effective and eco-friendly adsorbent for successfully removing iron from leached geological matrices while maintaining a reasonable degree of reusability.展开更多
This study focuses on the electrical properties and microstructure of polypropylene(PP)-based blends used for cable insulation in nuclear power plants(NPPs).The PP-based blend,comprising isotactic PP and propylene-bas...This study focuses on the electrical properties and microstructure of polypropylene(PP)-based blends used for cable insulation in nuclear power plants(NPPs).The PP-based blend,comprising isotactic PP and propylene-based elastomer(PBE)at concentrations ranging from 0 to 50 wt%,underwent a melt blending process and subsequent cobalt-60 gamma-ray irradiation with doses ranging from 0 to 250 kGy.Electrical conductivity,trap distribution,and alternating(AC)breakdown strength were chosen to assess the insulation performance.These results indicate that the addition of PBE significantly improves the electrical properties of PP under irradiation.For PP,the electrical conductivity increased with irradiation,whereas the trap depth and breakdown strength decreased sharply.Conversely,for the blend,these changes initially exhibit opposite trends.When the irradiation was increased to 250 kGy,the AC breakdown strength of the blend improved by more than 21%compared to that of PP.The physical and chemical structures of the samples were investigated to explore the improvement mechanisms.The results offer insights into the design of new cable-insulation materials suitable for NPPs.展开更多
Leachate sludge,a byproduct of municipal solid waste leachate treated through biochemical processes,is characterized by high water content(761.1%)and significant organic matter content(71.2%).Cement that is commonly u...Leachate sludge,a byproduct of municipal solid waste leachate treated through biochemical processes,is characterized by high water content(761.1%)and significant organic matter content(71.2%).Cement that is commonly used for solidifying leachate sludge has shown limited effectiveness.To address this issue,an alkali-activated ground-granulated blast-furnace slag(GGBS)geopolymer blended with polypropylene fibers was developed to solidify leachate sludge.Moreover,unconfined compressive strength(UCS),immersion,as well as X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),and scanning electron microscope(SEM)tests were conducted to investigate the solidification effect and mechanism of the GGBS-based geopolymer and fibers on leachate sludge.The results showed that:the 28-d UCS of the solidified sludge with 20%and 30%GGBS is 0.35 MPa and 1.85 MPa,and decreases to 0.18 MPa and 1.13 MPa,respectively,after soaked in water for 28 d.Notably,the UCS of the solidified sludge with 30%GGBS satisfied the strength requirement of roadbed materials.Polypropylene fibers significantly enhanced the strength,ductility and water stability of the solidified sludge,with an optimal fiber content of 0.3%.Alkali-activated GGBS geopolymer generated three-dimensional,cross-linked geopolymeric gels within the solidified sludge,cementing sludge particles and filling intergranular pores to form a stable cementitious structure,thereby achieving effective solidification.Furthermore,incorporating polypropylene fibers improved the bonding and anchoring effect between fiber and solidified sludge,constrained lateral deformation of the solidified sludge,restricted crack propagation,and enhanced engineering performance of the solidified leachate sludge.展开更多
To examine the influences of waste polypropylene fiber(PPF)on the strength and internal pore structure of recycled aggregate concrete incorporating iron ore tailings,both the cubic compressive strength and axial compr...To examine the influences of waste polypropylene fiber(PPF)on the strength and internal pore structure of recycled aggregate concrete incorporating iron ore tailings,both the cubic compressive strength and axial compressive strength of the concrete were measured.Additionally,the microstructure was analyzed using scanning electron microscopy.The evolution of pore structure parameters,including pore size distribution,pore type distribution,and nuclear magnetic resonance spectral area in the concrete,was investigated through nuclear magnetic resonance(NMR)analysis.A model correlating the concrete's pore structure with its macroscopic performance was subsequently developed based on fractal theory.The results demonstrate that an appropriate amount of PPF created a bridging effect that decelerated the progression of macro cracks,enhanced the ductility of the concrete's failure mode,and increased both cubic compressive strength and axial compressive strength,with the most effective dosage being approximately 0.6%.An appropriate amount of PPF(ranging from 0.3%to 0.6%)facilitated the formation of harmless pores and shifted the pore size distribution towards medium and small sizes.Specifically,a fiber content of 0.6%resulted in the most significant reduction in the T2 spectral area.Furthermore,the pore structure of concrete exhibits distinct fractal characteristics.As the PPF content increased,the fractal dimension initially rose and then declined,demonstrating a strong correlation with the mechanical properties.展开更多
This study focused on the production of polypropylene(PP)/silver(Ag)composites via additive manufacturing.This study aimed to enhance the quality of medical-grade PP in material extrusion(MEX)three-dimensional printin...This study focused on the production of polypropylene(PP)/silver(Ag)composites via additive manufacturing.This study aimed to enhance the quality of medical-grade PP in material extrusion(MEX)three-dimensional printing(3DP)by improving its mechanical properties while simultaneously adding antibacterial properties.The latter can find extremely important and versatile properties that are applicable in defense and security domains.PP/Ag nanocomposites were prepared using a novel method based on a reaction occurring while mixing appropriate quantities of the starting polymers and additives,namely polyvinylpyrrolidone(PVP)as the matrix material and silver nitrate(AgNO_(3))as the filler.This process produced three-dimensional(3D)printed filaments,which were then used to create specimens for a series of standardized tests.It was found that the mechanical properties of the nanocomposites were enhanced in relation to pristine PP,especially for the PP matrix with various loadings of AgNO_(3)and PVP,such as 5.0 wt%and 2.5 wt%,respectively.The voids,inclusions,and actual-to-nominal dimensions also showed improved results.The 3DP specimens exhibited a more effective biocidal performance against Staphylococcus aureus than Escherichia coli,which developed an inhibition zone only in the case of PP with filler loading percentages of AgNO_(3)and PVP at 10.0 wt%and 5.0 wt%,respectively Compounds possessing such properties can be beneficial for various applications requiring increased mechanical properties and biocidal capabilities,such as in the Defence or medical industries.展开更多
Grafting of acrylic acid (AAc) and acrylamide (AAm) onto preirradiated PP film was performed in aqueous solution of AAc and AAm, respectively. Electron beam accelerator was used as irradiation source. The effect of f...Grafting of acrylic acid (AAc) and acrylamide (AAm) onto preirradiated PP film was performed in aqueous solution of AAc and AAm, respectively. Electron beam accelerator was used as irradiation source. The effect of ferrous sulfate, sodium nitrate, methanol and glucose on the degree of grafting was demonstrated. The function of the different additives was compared by the grafting of different monomers (AAc and AAm). The results show that the four of these additives are elective on the grafting of AAc. Only two of these additives, ferrous sulfate and methanol were effective on the grafting of AAm.展开更多
Aim To determine the effect of silane grafted polypropylene on the property of different filler/polypropylene composites. Methods Polypropylene (PP) composites filled with talc(Ta), baryta sulfate and calcium carbonat...Aim To determine the effect of silane grafted polypropylene on the property of different filler/polypropylene composites. Methods Polypropylene (PP) composites filled with talc(Ta), baryta sulfate and calcium carbonate coupled with silane grafted polypropylene (PP-g-Si) were made, their mechanical properties and thermal properties were investigated, respectively. Results As compared with the non-coupled composites, the mechanical properties of PP/Ta/PP-g-Si composites were improved to some extent, though the values of tensile modulus and the strain at peak were decreased. But for PP/BaSO4 and PP/CaCO3 composites, the values of their mechanical properties varied slightly or even decreased with increasing PP-g-Si content within the experimental component. Meanwhile, PP-g-Si also affected the melting and crystallization behavior of PP in the composites. Conclusion PP-g-Si offers compatibilization in PP/Ta composites, but offers no-compatibilization in PP/BaSO4 and PP/CaCO3 composites within the extent of the present range of PP-g-Si, which shows that PP-g-Si can be used as the macromolecular coupling agent of PP and Ta composite.展开更多
Polypropylene fibres and three sizes of steel fibres reinforced concrete are discussed. The total fibres content ranges from 0 4%-0 95% by volume of concrete. A four point bending test is adopted on the notched pris...Polypropylene fibres and three sizes of steel fibres reinforced concrete are discussed. The total fibres content ranges from 0 4%-0 95% by volume of concrete. A four point bending test is adopted on the notched prisms with the size of 100?mm×100?mm×500?mm to investigate the effect of hybrid fibres on crack arresting. The research results show that there is a positive synergy effect between large steel fibres and polypropylene fibres on the load bearing capacity in the small displacement range. But this synergy effect disappears in the large displacement range. The large and strong steel fibre is better than soft polypropylene fibre and small steel fibre in the aspect of energy absorption capacity in the large displacement range. The static usage limitation for the hybrid fibres concrete with “wide peak' or “multi peaks' load CMOD pattern should be carefully selected. The ultimate load bearing capacity and the crack width or CMOD at this load level should be jointly considered.展开更多
Polypropylene was cracked thermally and catalytically in the presence of kaoline and silica alumina in a semi batch reactor in the temperature range 400℃～550℃ in order to obtain suitable liquid fuels.The dependenci...Polypropylene was cracked thermally and catalytically in the presence of kaoline and silica alumina in a semi batch reactor in the temperature range 400℃～550℃ in order to obtain suitable liquid fuels.The dependencies between process temperatures,types of catalyst,feed compositions and product yields of the obtained fuel fractions were found.It was observed that up to 450℃ thermal cracking temperature,the major product of pyrolysis was liquid oil and the major product at other higher temperatures(475℃～550℃) are viscous liquid or wax and the highest yield of pyrolysis product is 82.85% by weight at 500℃.Use of kaoline and silica alumina decreased the reaction time and increased the yield of liquid fraction.Again the major pyrolysis product in catalytic pyrolysis at all temperatures was low viscous liquid oil.Silica alumina was found better as compared to kaoline in liquid yield and in reducing the reaction temperature.The maximum oil yield using silica alumina and kaoline catalyst are 91% and 89.5% respectively.On the basis of the obtained results hypothetical continuous process of waste polypropylene plastics processing for engine fuel production can be presented.展开更多
Oleic acid (OA)-modified CaCO3 nanoparticles were prepared using surface modification method. Infrared spectroscopy (IR) was used to investigate the structure of the modified CaCO3 nanoparticles, and the result showed...Oleic acid (OA)-modified CaCO3 nanoparticles were prepared using surface modification method. Infrared spectroscopy (IR) was used to investigate the structure of the modified CaCO3 nanoparticles, and the result showed that OA attached to the surface of CaCO3 nanoparticles with the ionic bond. Effect of OA concentration on the dispersion stability of CaCO3 in heptane was also studied, and the result indicated that modified CaCO3 nanoparticles dispersed in heptane more stably than unmodified ones. The optimal proportion of OA to CaCO3 was established. The effect of modified CaCO3 nanoparticles on crystallization behavior of polypropylene (PP) was studied by means of DSC. It was found that CaCO3 significantly increased the crystallization temperature, crystallization degree and crystallization rate of PP, and the addition of modified CaCO3 nanoparticles can lead to the formation of β-crystal PP. Effect of the modified CaCO3 content on mechanical properties of PP/CaCO3 nanocomposites was also studied. The results showed that the modified CaCO3 can effectively improve the mechanical properties of PP. In comparison with PP, the impact strength of PP/CaCO3 nanocomposites increased by about 65% and the flexural strength increased by about 20%.展开更多
In this work, the crystallization of immiscible polypropylene （PP）/polybutene-1 （PB） blends, in particular the effect of crystal morphology of PP （HTC, high Tm component） on the subsequent crystallization behavi...In this work, the crystallization of immiscible polypropylene （PP）/polybutene-1 （PB） blends, in particular the effect of crystal morphology of PP （HTC, high Tm component） on the subsequent crystallization behavior of PB （LTC, low Tm component） was studied. Herein, we firstly indicated that PP/PB blends were not completely compatible but characterized as the LCST-like phase diagram above the melting temperature of PP. Crystallization of PP at different crystallization temperatures brought about different PP crystal morphologies and PB was segregated and confined at different locations. Much larger-sized domain of PB component appeared in PP spherulites resulting from the effects of non-negligible phase separation and the slower PP crystallization rate as PP crystallized at high temperature. As temperature continued to fall below Tm of PB, the fractionated and confined crystallization of PB occurred in the framework of PP spherulites, reflected by the decreased crystallization temperature （To） of PB and the formation of form I＇ beside form II. Notably, if PP previously crystallized at high Tc, fractionated crystallization of PB became predominant and confined crystallization of PB became weak due to the much wider droplet-size distribution of PB domains.展开更多
The effects of aluminum hypophosphite（AHP） as a synergistic agent on the flame retardancy and thermal degradation behavior of intumescent flame retardant polypropylene composites（PP/IFR） containing ammonium polyph...The effects of aluminum hypophosphite（AHP） as a synergistic agent on the flame retardancy and thermal degradation behavior of intumescent flame retardant polypropylene composites（PP/IFR） containing ammonium polyphosphate（APP） and triazine charring-foaming agent（CFA） were investigated by limiting oxygen index（LOI）, UL-94 measurement, thermogravimetric analysis（TGA）, cone calorimeter test（CONE）, scanning electron microscopy（SEM） and X-ray photoelectron spectroscopy（XPS）. It was found that the combination of IFR with AHP exhibited an evident synergistic effect and enhanced the flame retardant efficiency for PP matrix. The specimens with the thickness of 0.8 mm can pass UL-94 V-0 rating and the LOI value reaches 33.5% based on the total loading of flame retardant of 24 wt%, and the optimum mass fraction of AHP/IFR is 1：6. The TGA data revealed that AHP could change the degradation behavior of IFR and PP/IFR system, enhance the thermal stability of the IFR and PP/IFR systems at high temperatures and promote the char residue formation. The CONE results revealed that IFR/AHP blends can efficiently reduce the combustion parameters of PP, such as heat release rate（HRR）, total heat release（THR）, smoke production rate（SPR） and so on. The morphological structures of char residue demonstrated that AHP is of benefit to the formation of a more compact and homogeneous char layer on the materials surface during burning. The analysis of XPS indicates that AHP may promote the formation of sufficient char on the materials surface and improve the flame retardant properties.展开更多
基金supported by the National Natural Science Foundation of China(No.51721091).
文摘In this work,the lamellar structural evolution and microvoids variations of βpolypropylene(β-PP)during the processing of two different stretching methods,sequential biaxial stretching and simultaneous biaxial stretching,were investigated in detail.It was found that different stretching methods led to significantly different lamellae deformation modes,and the microporous membranes obtained from the simultaneous biaxial stretching exhibited better mechanical properties.For the sequential biaxial stretching,abundant coarse fibers originated from the tight accumulation of the lamellae parallel to the longitudinal stretching direction,whereas the lamellae perpendicular to the stretching direction were easily deformed and separated.Those coarse fibers were difficult to be separated to form micropores during the subsequent transverse stretching process,resulting in a poor micropores distribution.However,for the simultaneous biaxial stretching,theβcrystal had the same deformation mode,that is,the lamellae distributed in different directions were all destroyed,forming abundant microvoids and little coarse fibers.
文摘To compare the suitable working conditions of polypropylene(PP)and polycaprolactam(PA6)materials in actual use in automobiles,the effects of different temperature aging and different reagents on the mechanical properties of the two materials,such as tensile,bending,compression,and impact were studied.The results indicate that the short⁃term low⁃temperature environment had no much effect on the mechanical properties of PP and PA6.After long⁃term thermal aging at 80℃,the strength of PP and PA6 increased while their toughness decreased.After short⁃term thermal aging at 120℃,PP strength decreases and toughness increases,while PA6 strength increases and toughness decreases.The soaking of glass water and car shampoo had no much effect on the mechanical properties of PP,but had a significant impact on the mechanical properties of PA6.With the increase of soaking time,the strength of PA6 significantly decreases and the toughness significantly increases.The soaking of 95#gasoline had no much effect on the mechanical properties of PA6,but has a significant impact on the mechanical properties of PP.After 720 h of soaking,the retention rates of the tensile strength,bending strength,and compressive strength of PP were all less than 80%,while the retention rate of the impact strength of the cantilever beam was 160.4%.
基金supported in part by the National Natural Science Foundation of China(Grant 52277153).
文摘The performance of polypropylene film determines the reliability of capacitors.This paper studies the change of insulation characteristics of the insulation dielectric polypropylene of high-voltage capacitors during the long-term operation process.Moreover,the correction of the insulation failure model of polypropylene media is implemented.Some conclusions are drawn from a series of experiments.The breakdown strength of the insulation dielectrics decreases as the withstand time rises,with amaximum decrease of 37.91%compared to the polypropylene sample without withstand voltage.As the electric field increases from−20 to−100 kV/mm,the total amount of space charge,the trap energy level and the trap density inside the polypropylene increase by 524.15%,18.99%and 773.36%,respectively.In the capacitor simulation model,the electric field in the capacitor increases by 19.62%after presetting space charge relative to the nonspace charge.The experimental data are substituted into the inverse power model,and the trap parameters are used to modify the model.The results show that the ageing state of the polypropylene has a negative exponential relationship with the trap parameters.This paper provides an important reference for the study of the failure mechanism of polypropylene in high-voltage capacitors and the assessment of polypropylene ageing state.
基金the equipment support of Sharing Platform of Scientific Equipments,Ministry of Education's Research Center for Comprehensive Utilization and Clean Process Engineering of Phosphrous Resources,Sichuan University。
文摘A novel eco-friendly charring agent(L-OH)was successfully synthesized by combining pentaerythritol(PER)with lignin through a simple two-step reaction.The structure of L-OH was characterized using Fourier transform infrared(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM)and EDS.In addition,L-OH was introduced into polypropylene(PP)together with melamine(MEL)and ammonium polyphosphate(APP)as an intumescent flame retardant(IFRR).The flame retardancy of PP/IFRR composites were investigated using limited oxygen index(LOI),UL-94,thermogravimetric analysis(TGA)and cone calorimeter(CC)test.The experimental results indicate that the PP/IFRR composites pass the V-0 grade of the UL-94 test when the addition amount of IFRR is no less than 20%,and the LOI value of the composite reaches 32.2%at 30%IFRR addition.The peak heat release rate(PHRR)and peak smoke production rate(PSPR)of the composite decrease by 72.8%and 70.4%compared with pure PP,respectively.The flame retardancy mechanism was investigated by TGA,TG-FTIR and residual carbon analysis.These analyses indicate that L-OH can form a more continuous and dense carbon layer during the combustion process,which is the main factor contributing to the improved flame retardancy of PP.
文摘A comparative study of products of thermal and thermocatalytic cracking of polypropylene(PP) in the presence of potassium polytitanate(PPT) synthesized by treatment of TiO_(2)(rutile) powder with molten mixture of KOH and KNO_(3) taken in a weight ratio of 30∶30∶40 has been carried out.It was shown that the studied type of PPT powder exhibits catalytic properties in the reaction of thermal decomposition of PP,compared to the effect of commercial zeolite catalyst CBV-780 traditionally used for this purpose.Based on the analysis performed,the differences in the mechanism of catalytic action of PPT and the zeolite were considered.The reasons for the observed differences in the composition of PP cracking products and in the rate of coke formation on the surface of studied catalysts were analyzed.Considering the obtained results,it has been proposed that the CBV-780 catalyst promoted more intensive production of the gaseous hydrocarbons compared to PPT,due to higher specific surface area(internal surface) accessible for relatively light and small-sized hydrocarbon products of cracking.However,intensive coke formation on the outer surface of the microporous zeolite contributes to the blocking of transport channels and the rapid loss of catalytic action.At the same time,PPT,which initially has a smaller specific surface area,retains its catalytic activity significantly longer due to slit-shaped flat pores and higher transport accessibility of the inner surface.
文摘The present study presents an assessment of the interrelations between long-chain branching,specific nucleation,and end-use properties of polypropylene blends:blends of linear polypropylene(L-PP)and long-chain branched polypropylene(LCB-PP)modified by a specificβ-nucleating agent(NA).Specimens with various LCB-PP compositions with and without NA were prepared under complex flow fields by injection molding.Wide-angle X-ray scattering was employed to capture the X-ray patterns of both the skin and core of the specimens,determining the overall crystallinity and amounts of individual polymorphs.The increasing content of LCB-PP andγ-phase,at the same time,in the blends is reflected in both increasing crystallinity and improved mechanical properties,namely,yield stress and Young’s modulus.On the other hand,the composition of the blends had no significant effect on the impact strength,except for nucleated L-PP.It has been demonstrated that adding a relatively small amount of LCB-PP is sufficient to modify the mechanical properties of linear polypropylene.Even a very small amount of LCB-PP in the L-PP suppressed the effectiveness of NA.
文摘Geological samples often contain significant amounts of iron,which,although not typically the target element,can substantially interfere with the analysis of other elements of interest.To mitigate these interferences,amidoximebased radiation grafted adsorbents have been identified as effective for iron removal.In this study,an amidoximefunctionalized,radiation-grafted adsorbent synthesized from polypropylene waste(PPw-g-AO-10)was employed to remove iron from leached geological samples.The adsorption process was systematically optimized by investigating the effects of pH,contact time,adsorbent dosage,and initial ferric ion concentration.Under optimal conditions-pH1.4,a contact time of 90 min,and an initial ferric ion concentration of 4500 mg/L-the adsorbent exhibited a maximum iron adsorption capacity of 269.02 mg/g.After optimizing the critical adsorption parameters,the adsorbent was applied to the leached geological samples,achieving a 91%removal of the iron content.The adsorbent was regenerated through two consecutive cycles using 0.2 N HNO_(3),achieving a regeneration efficiency of 65%.These findings confirm the efficacy of the synthesized PPw-g-AO-10 as a cost-effective and eco-friendly adsorbent for successfully removing iron from leached geological matrices while maintaining a reasonable degree of reusability.
基金supported by the National Natural Science Foundation of China(No.52077151)the State Key Laboratory of Electrical Insulation and Power Equipment(No.EIPE23208)the Key Laboratory of Engineering Dielectrics and Its Application,Ministry of Education(No.KFM202203).
文摘This study focuses on the electrical properties and microstructure of polypropylene(PP)-based blends used for cable insulation in nuclear power plants(NPPs).The PP-based blend,comprising isotactic PP and propylene-based elastomer(PBE)at concentrations ranging from 0 to 50 wt%,underwent a melt blending process and subsequent cobalt-60 gamma-ray irradiation with doses ranging from 0 to 250 kGy.Electrical conductivity,trap distribution,and alternating(AC)breakdown strength were chosen to assess the insulation performance.These results indicate that the addition of PBE significantly improves the electrical properties of PP under irradiation.For PP,the electrical conductivity increased with irradiation,whereas the trap depth and breakdown strength decreased sharply.Conversely,for the blend,these changes initially exhibit opposite trends.When the irradiation was increased to 250 kGy,the AC breakdown strength of the blend improved by more than 21%compared to that of PP.The physical and chemical structures of the samples were investigated to explore the improvement mechanisms.The results offer insights into the design of new cable-insulation materials suitable for NPPs.
基金financially supported by the National Natural Science Foundation of China(Grant No.52078142).
文摘Leachate sludge,a byproduct of municipal solid waste leachate treated through biochemical processes,is characterized by high water content(761.1%)and significant organic matter content(71.2%).Cement that is commonly used for solidifying leachate sludge has shown limited effectiveness.To address this issue,an alkali-activated ground-granulated blast-furnace slag(GGBS)geopolymer blended with polypropylene fibers was developed to solidify leachate sludge.Moreover,unconfined compressive strength(UCS),immersion,as well as X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),and scanning electron microscope(SEM)tests were conducted to investigate the solidification effect and mechanism of the GGBS-based geopolymer and fibers on leachate sludge.The results showed that:the 28-d UCS of the solidified sludge with 20%and 30%GGBS is 0.35 MPa and 1.85 MPa,and decreases to 0.18 MPa and 1.13 MPa,respectively,after soaked in water for 28 d.Notably,the UCS of the solidified sludge with 30%GGBS satisfied the strength requirement of roadbed materials.Polypropylene fibers significantly enhanced the strength,ductility and water stability of the solidified sludge,with an optimal fiber content of 0.3%.Alkali-activated GGBS geopolymer generated three-dimensional,cross-linked geopolymeric gels within the solidified sludge,cementing sludge particles and filling intergranular pores to form a stable cementitious structure,thereby achieving effective solidification.Furthermore,incorporating polypropylene fibers improved the bonding and anchoring effect between fiber and solidified sludge,constrained lateral deformation of the solidified sludge,restricted crack propagation,and enhanced engineering performance of the solidified leachate sludge.
基金Funded by the Natural Science Foundation of Shaanxi Province(No.2023-JC-QN-0553)。
文摘To examine the influences of waste polypropylene fiber(PPF)on the strength and internal pore structure of recycled aggregate concrete incorporating iron ore tailings,both the cubic compressive strength and axial compressive strength of the concrete were measured.Additionally,the microstructure was analyzed using scanning electron microscopy.The evolution of pore structure parameters,including pore size distribution,pore type distribution,and nuclear magnetic resonance spectral area in the concrete,was investigated through nuclear magnetic resonance(NMR)analysis.A model correlating the concrete's pore structure with its macroscopic performance was subsequently developed based on fractal theory.The results demonstrate that an appropriate amount of PPF created a bridging effect that decelerated the progression of macro cracks,enhanced the ductility of the concrete's failure mode,and increased both cubic compressive strength and axial compressive strength,with the most effective dosage being approximately 0.6%.An appropriate amount of PPF(ranging from 0.3%to 0.6%)facilitated the formation of harmless pores and shifted the pore size distribution towards medium and small sizes.Specifically,a fiber content of 0.6%resulted in the most significant reduction in the T2 spectral area.Furthermore,the pore structure of concrete exhibits distinct fractal characteristics.As the PPF content increased,the fractal dimension initially rose and then declined,demonstrating a strong correlation with the mechanical properties.
文摘This study focused on the production of polypropylene(PP)/silver(Ag)composites via additive manufacturing.This study aimed to enhance the quality of medical-grade PP in material extrusion(MEX)three-dimensional printing(3DP)by improving its mechanical properties while simultaneously adding antibacterial properties.The latter can find extremely important and versatile properties that are applicable in defense and security domains.PP/Ag nanocomposites were prepared using a novel method based on a reaction occurring while mixing appropriate quantities of the starting polymers and additives,namely polyvinylpyrrolidone(PVP)as the matrix material and silver nitrate(AgNO_(3))as the filler.This process produced three-dimensional(3D)printed filaments,which were then used to create specimens for a series of standardized tests.It was found that the mechanical properties of the nanocomposites were enhanced in relation to pristine PP,especially for the PP matrix with various loadings of AgNO_(3)and PVP,such as 5.0 wt%and 2.5 wt%,respectively.The voids,inclusions,and actual-to-nominal dimensions also showed improved results.The 3DP specimens exhibited a more effective biocidal performance against Staphylococcus aureus than Escherichia coli,which developed an inhibition zone only in the case of PP with filler loading percentages of AgNO_(3)and PVP at 10.0 wt%and 5.0 wt%,respectively Compounds possessing such properties can be beneficial for various applications requiring increased mechanical properties and biocidal capabilities,such as in the Defence or medical industries.
文摘Grafting of acrylic acid (AAc) and acrylamide (AAm) onto preirradiated PP film was performed in aqueous solution of AAc and AAm, respectively. Electron beam accelerator was used as irradiation source. The effect of ferrous sulfate, sodium nitrate, methanol and glucose on the degree of grafting was demonstrated. The function of the different additives was compared by the grafting of different monomers (AAc and AAm). The results show that the four of these additives are elective on the grafting of AAc. Only two of these additives, ferrous sulfate and methanol were effective on the grafting of AAm.
文摘Aim To determine the effect of silane grafted polypropylene on the property of different filler/polypropylene composites. Methods Polypropylene (PP) composites filled with talc(Ta), baryta sulfate and calcium carbonate coupled with silane grafted polypropylene (PP-g-Si) were made, their mechanical properties and thermal properties were investigated, respectively. Results As compared with the non-coupled composites, the mechanical properties of PP/Ta/PP-g-Si composites were improved to some extent, though the values of tensile modulus and the strain at peak were decreased. But for PP/BaSO4 and PP/CaCO3 composites, the values of their mechanical properties varied slightly or even decreased with increasing PP-g-Si content within the experimental component. Meanwhile, PP-g-Si also affected the melting and crystallization behavior of PP in the composites. Conclusion PP-g-Si offers compatibilization in PP/Ta composites, but offers no-compatibilization in PP/BaSO4 and PP/CaCO3 composites within the extent of the present range of PP-g-Si, which shows that PP-g-Si can be used as the macromolecular coupling agent of PP and Ta composite.
文摘Polypropylene fibres and three sizes of steel fibres reinforced concrete are discussed. The total fibres content ranges from 0 4%-0 95% by volume of concrete. A four point bending test is adopted on the notched prisms with the size of 100?mm×100?mm×500?mm to investigate the effect of hybrid fibres on crack arresting. The research results show that there is a positive synergy effect between large steel fibres and polypropylene fibres on the load bearing capacity in the small displacement range. But this synergy effect disappears in the large displacement range. The large and strong steel fibre is better than soft polypropylene fibre and small steel fibre in the aspect of energy absorption capacity in the large displacement range. The static usage limitation for the hybrid fibres concrete with “wide peak' or “multi peaks' load CMOD pattern should be carefully selected. The ultimate load bearing capacity and the crack width or CMOD at this load level should be jointly considered.
文摘Polypropylene was cracked thermally and catalytically in the presence of kaoline and silica alumina in a semi batch reactor in the temperature range 400℃～550℃ in order to obtain suitable liquid fuels.The dependencies between process temperatures,types of catalyst,feed compositions and product yields of the obtained fuel fractions were found.It was observed that up to 450℃ thermal cracking temperature,the major product of pyrolysis was liquid oil and the major product at other higher temperatures(475℃～550℃) are viscous liquid or wax and the highest yield of pyrolysis product is 82.85% by weight at 500℃.Use of kaoline and silica alumina decreased the reaction time and increased the yield of liquid fraction.Again the major pyrolysis product in catalytic pyrolysis at all temperatures was low viscous liquid oil.Silica alumina was found better as compared to kaoline in liquid yield and in reducing the reaction temperature.The maximum oil yield using silica alumina and kaoline catalyst are 91% and 89.5% respectively.On the basis of the obtained results hypothetical continuous process of waste polypropylene plastics processing for engine fuel production can be presented.
基金Supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars.
文摘Oleic acid (OA)-modified CaCO3 nanoparticles were prepared using surface modification method. Infrared spectroscopy (IR) was used to investigate the structure of the modified CaCO3 nanoparticles, and the result showed that OA attached to the surface of CaCO3 nanoparticles with the ionic bond. Effect of OA concentration on the dispersion stability of CaCO3 in heptane was also studied, and the result indicated that modified CaCO3 nanoparticles dispersed in heptane more stably than unmodified ones. The optimal proportion of OA to CaCO3 was established. The effect of modified CaCO3 nanoparticles on crystallization behavior of polypropylene (PP) was studied by means of DSC. It was found that CaCO3 significantly increased the crystallization temperature, crystallization degree and crystallization rate of PP, and the addition of modified CaCO3 nanoparticles can lead to the formation of β-crystal PP. Effect of the modified CaCO3 content on mechanical properties of PP/CaCO3 nanocomposites was also studied. The results showed that the modified CaCO3 can effectively improve the mechanical properties of PP. In comparison with PP, the impact strength of PP/CaCO3 nanocomposites increased by about 65% and the flexural strength increased by about 20%.
基金financially supported by Shandong Provincial Key R&D Program (No. 2015GGX102019)the Taishan Scholar Program
文摘In this work, the crystallization of immiscible polypropylene （PP）/polybutene-1 （PB） blends, in particular the effect of crystal morphology of PP （HTC, high Tm component） on the subsequent crystallization behavior of PB （LTC, low Tm component） was studied. Herein, we firstly indicated that PP/PB blends were not completely compatible but characterized as the LCST-like phase diagram above the melting temperature of PP. Crystallization of PP at different crystallization temperatures brought about different PP crystal morphologies and PB was segregated and confined at different locations. Much larger-sized domain of PB component appeared in PP spherulites resulting from the effects of non-negligible phase separation and the slower PP crystallization rate as PP crystallized at high temperature. As temperature continued to fall below Tm of PB, the fractionated and confined crystallization of PB occurred in the framework of PP spherulites, reflected by the decreased crystallization temperature （To） of PB and the formation of form I＇ beside form II. Notably, if PP previously crystallized at high Tc, fractionated crystallization of PB became predominant and confined crystallization of PB became weak due to the much wider droplet-size distribution of PB domains.
基金financially supported by the Fundamental Research Funds for the Central Universities(DL12CB07)Youth Science Fund of Heilongjiang Province(No.QC2011C102)Heilongjiang Major Research Projects(GA12A102)
文摘The effects of aluminum hypophosphite（AHP） as a synergistic agent on the flame retardancy and thermal degradation behavior of intumescent flame retardant polypropylene composites（PP/IFR） containing ammonium polyphosphate（APP） and triazine charring-foaming agent（CFA） were investigated by limiting oxygen index（LOI）, UL-94 measurement, thermogravimetric analysis（TGA）, cone calorimeter test（CONE）, scanning electron microscopy（SEM） and X-ray photoelectron spectroscopy（XPS）. It was found that the combination of IFR with AHP exhibited an evident synergistic effect and enhanced the flame retardant efficiency for PP matrix. The specimens with the thickness of 0.8 mm can pass UL-94 V-0 rating and the LOI value reaches 33.5% based on the total loading of flame retardant of 24 wt%, and the optimum mass fraction of AHP/IFR is 1：6. The TGA data revealed that AHP could change the degradation behavior of IFR and PP/IFR system, enhance the thermal stability of the IFR and PP/IFR systems at high temperatures and promote the char residue formation. The CONE results revealed that IFR/AHP blends can efficiently reduce the combustion parameters of PP, such as heat release rate（HRR）, total heat release（THR）, smoke production rate（SPR） and so on. The morphological structures of char residue demonstrated that AHP is of benefit to the formation of a more compact and homogeneous char layer on the materials surface during burning. The analysis of XPS indicates that AHP may promote the formation of sufficient char on the materials surface and improve the flame retardant properties.
