Semicrystalline polymers usually undergo multilevel microstructural evolutions with annealing and stretching processes,which is es-sential to tailor the physical properties of the polymer.Here,poly(butylene carbonate)...Semicrystalline polymers usually undergo multilevel microstructural evolutions with annealing and stretching processes,which is es-sential to tailor the physical properties of the polymer.Here,poly(butylene carbonate)(PBC)sheets were prepared via isothermal annealing and unidirectional pre-stretching processes,then the changes of PBC in crystallinity,mechanical properties,thermal properties and microscopic changes before and after annealing and stretching were measured,as well as the relationship between microstructure and macroscopic proper-ties before and after stretching.The strengthening mechanism of PBC was also described.It was demonstrated that shish-kabab structure emerged under the pre-stretching process.With the increase of the tensile ratio,the crystallinity,structure and mechanical properties are in-creased differently.Among them,the crystallinity and tensile strength after annealing-stretching treatment increased to 24.45%and 104.5 MPa,respectively,which were about 1.55 times and 3.4 times of those-without any treatment.展开更多
The effects of crystallization temperature and blend ratio on the polymorphic crystal structures of poly（butylene adipate） （PBA） in poly（butylene succinate） （PBS）/poly（butylene adipate） （PBS/PBA） blends we...The effects of crystallization temperature and blend ratio on the polymorphic crystal structures of poly（butylene adipate） （PBA） in poly（butylene succinate） （PBS）/poly（butylene adipate） （PBS/PBA） blends were studied by means of differential scanning calorimetry （DSC）, wide-angle X-ray diffraction （XRD） and atomic force microscopy （AFM）. It was revealed that the polymorphism of PBA can be regulated by the blend ratio even in a non-isothermal crystallization process. The results demonstrate that high temperature favors fiat-on α crystals, while low temperature contributes to edge-on β crystals. It was also found that the effect of blend ratio on the crystallization mechanism of PBA is well coincident with that of the crystallization temperature. The increment of PBS content in the PBS/PBA blend gives rise to more β-form crystals of PBA. For those PBS/PBA blends with low PBA content, the interlamellar phase segregation of PBA makes its molecular chains so difficult to diffuse from one isolated microdomain to another that high crystallization temperature and sufficiently long crystallization time will be required if the PBA α-type crystals are targeted.展开更多
In order to improve the wettability and biocompatibility of the poly （butylene terephthalate） non-woven （PBTNW）, the method of surface modification is used to graft copolymerization of chitosan （CS） onto the PBT...In order to improve the wettability and biocompatibility of the poly （butylene terephthalate） non-woven （PBTNW）, the method of surface modification is used to graft copolymerization of chitosan （CS） onto the PBTNW under alkylpolyglycoside （APG） inducing. The product is thoroughly characterized with the Fourier transform infrared spectroscopy （FrIR）, the electron spectroscopy for chemical analysis （ESCA）, the thermogravimetric （TG） and the scanning electron microscopy （SEM）. It is found that chitosan is successfully grafted onto PBTNW. In addition, the water contact angles, hemolysis tests and cytotoxicity evaluation tests show an improvement in wettability and biocompatihility as a result of graft copolymerization of chitosan. So the CS-grafted PBTNW exhibits greater superiority than the original PBTNW. The CS-grafted PBTNW can be a candidate for blood filter materials and other medical applications.展开更多
A biodegradable blend foaming material of poly(butylene adipate-co-terephthalate)(PBAT)/poly(propylene carbonate)(PPC)was successfully prepared by chemical foaming agent and screw extrusion method.First,PBAT was modif...A biodegradable blend foaming material of poly(butylene adipate-co-terephthalate)(PBAT)/poly(propylene carbonate)(PPC)was successfully prepared by chemical foaming agent and screw extrusion method.First,PBAT was modified by bis(tert-butyl dioxy isopropyl)benzene(BIBP)for chain extension,and then the extended PBAT(E-PBAT)was foamed with PPC using a twin(single)screw extruder.By analyzing the properties of the blends,we found that Young’s modulus increased from 58.8 MPa of E-PBAT to 244.7 MPa of E-PBAT/PPC 50/50.The viscosity of the polymer has a critical influence on the formation of cells.Compared with neat PBAT(N-PBAT),the viscosity of E-PBAT increased by 3396 Pa·s and E-PBAT/PPC 50/50 increased by 8836 Pa·s.Meanwhile,the dynamic mechanical analysis(DMA)results showed that the storage modulus(E’)at room temperature increased from 538 MPa to 1650 MPa.The various phase morphologies(“sea-island”,“quasi-co-continuous”and“cocontinuous”)and crystallinity of the blends affected the spread velocity of gas and further affected the foaming morphology in E-PBAT/PPC foam.Therefore,through the analysis of phase morphology and foaming mechanism,we concluded that the E-PBAT/PPC 70/30 component has both excellent strength and the best foaming performance.展开更多
In recent years, poly(butylene adipate-co-terephthalate)(PBAT) has been widely used. However, PBAT-degrading bacteria have rarely been reported. PBAT-degrading bacteria were isolated from farmland soil and identified....In recent years, poly(butylene adipate-co-terephthalate)(PBAT) has been widely used. However, PBAT-degrading bacteria have rarely been reported. PBAT-degrading bacteria were isolated from farmland soil and identified. The effects of growth factors on the degradation of PBAT and the lipase activity of PBAT-degrading bacteria were assessed. The degradation mechanism was analyzed using scanning electron microscopy, attenuated total reflection Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, Xray diffraction, and liquid chromatography-mass spectrometry. The results showed that Stenotrophomonas sp. YCJ1 had a significant degrading effect on PBAT. Under certain conditions, the strain could secrete 10.53 U/m L of lipase activity and degrade 10.14 wt.% of PBAT films. The strain secreted lipase to catalyze the degradation of the ester bonds in PBAT, resulting in the production of degradation products such as terephthalic acid, 1,4-butanediol, and adipic acid. Furthermore, the degradation products could participate in the metabolism of YCJ1 as carbon sources to facilitate complete degradation of PBAT, indicating that the strain has potential value for the bioremediation of PBAT in the environment.展开更多
Poly（propylene carbonate） （PPC） was melt blended in a batch mixer with poly（butylene carbonate） （PBC） in an effort to improve the toughness of the PPC without compromising its biodegradability and biocompatibi...Poly（propylene carbonate） （PPC） was melt blended in a batch mixer with poly（butylene carbonate） （PBC） in an effort to improve the toughness of the PPC without compromising its biodegradability and biocompatibility. DMA results showed that the PPC/PBC blends were an immiscible two-phase system. With the increase in PBC content, the PPC/PBC blends showed decreased tensile strength, however, the elongation at break was increased to 230% for the 50/50 PPC/PBC blend. From the tensile strength experiments, the Pukanszky model gave credit to the modest interfacial adhesion between PPC and PBC, although PPC/PBC was immscible. The impact strength increased significantly which indicated the toughening effects of the PBC on PPC. SEM examination showed that cavitation and shear yielding were the major toughening mechanisms in the blends subjected the impact tests. TGA measurements showed that the thermal stability of PPC decreased with the incorporation of PBC. Rheological investigation demonstrated that the addition of PBC reduced the value of storage modulus, loss modulus and complex viscosity of the PPC/PBC blends to some extent. Moreover, the addition of PBC was found to increase the processability of PPC in extrusion. The introduction of PBC provided an efficient and novel toughened method to extend the application area of PPC.展开更多
Binary biodegradable polymers films, poly(butylene adipate-co-terephthalate)(PBAT) and poly(glycolic acid)(PGA), were prepared through batch melt mixing to obtain Film Ⅰ and Film Ⅱ under two different processing con...Binary biodegradable polymers films, poly(butylene adipate-co-terephthalate)(PBAT) and poly(glycolic acid)(PGA), were prepared through batch melt mixing to obtain Film Ⅰ and Film Ⅱ under two different processing conditions. PGA crystals played a major role in enhancing the mechanical and barrier properties of the films. For Film Ⅰ, there were initial PGA crystals before the film blowing process, the PGA molecular chain further crystallized, forming the oriented crystallization of PGA. Moreover, the Xcand crystalline size in Film Ⅰ were higher than those in Film Ⅱ. Compared with the different processing methods, Film Ⅰ has excellent mechanical and oxygen barrier properties due to the crystallization and orientation. The tensile strength reached 45.0 MPa, and tear strength exceeded 138.2 kN/m, while the elongation at break was as high as 750% for PBAT/PGA 85/15 in Film Ⅰ. The WVTR, WVP coefficients, and OP coefficients of PBAT/PGA films were decreased obviously with increasing the PGA content both in Film Ⅰ and Film Ⅱ. Moreover, the barrier properties of oxygen in Film Ⅰ were better than that in Film Ⅱ. This work reveals a feasible processing technique by introducing of initial crystallization of PGA to blow PBAT/PGA films with excellent mechanical and barrier properties.展开更多
A series of branched poly（butylene succinate）（PBS） were synthesized with several branching agents namely trimethylol propane（TMP）, malic acid, trimesic acid, citric acid and glycerol propoxylate. The structure o...A series of branched poly（butylene succinate）（PBS） were synthesized with several branching agents namely trimethylol propane（TMP）, malic acid, trimesic acid, citric acid and glycerol propoxylate. The structure of the branched polymers was analyzed by SEC and ~1H-NMR. The effect of branching agent structure on crystallization was also investigated and played a significant role. Isothermal studies showed that glycerol propoxylate could act as a nucleating agent. By contrast high content of TMP disturbed the regularity of the chain and hindered the crystallization of PBS. From the non-isothermal kinetic study, it was found that glycerol propoxylate increased noticeably the crystallization rate due to the flexible structure of the branching agent. A secondary nucleation was observed with glycerol propoxylate attributed to the crystallization of amorphous fraction included between crystallites formed at the primary crystallization. Chain topology was obtained through rheological investigations and the synthesized polymers showed a typical behavior of a mixture of linear and randomly branched PBS. The incorporation of branches improved the processability of PBS for film blowing application and the modulus and the stress at break of the resulting film were significantly increased.展开更多
Differential scanning calorimetry（DSC） has been widely applied to study crystallization and melting of materials. However, for polymeric lamellar crystals, the melting thermogram during heating process usually exhib...Differential scanning calorimetry（DSC） has been widely applied to study crystallization and melting of materials. However, for polymeric lamellar crystals, the melting thermogram during heating process usually exhibits a broad endothermic peak or even multiple endotherms, which may result from changes of metastability via recrystallization process. Sometimes, the recrystallization exotherm cannot be observed due to its overlapping with the melting endotherm. In this work, we employed a step heating procedure consisting of successive heating and temperature holding stages to measure the metastability of isothermally crystallized poly（butylene succinate）（PBS） crystals. With this approach we could gain the fraction of crystals melted at different temperature ranges and quantitatively detect the melting-recrystallization behavior. The melting-recrystallization behavior depends on the polymer chain structure and the crystallization temperature. For instance, PBS block copolymer hardly shows recrystallization behavior while PBS oligomer and high molecular weight PBS homopolymer demonstrate remarkable melting-recrystallization phenomenon. High molecular weight PBS isothermally crystallized in the low temperature range shows multiple melting-recrystallization while those isothermally crystallized at elevated temperatures do not exhibit observable recrystallization behavior. Furthermore, the melting endotherms were fitted via the melting kinetics equations. The original isothermally crystallized lamellae demonstrate quite different melting kinetics from the recrystallized lamellar crystals that melt at the highest temperature range, which is attributed to the different degrees of stabilization. Finally, the mechanism of melting-recrystallization is briefly discussed. We propose that apparent meltrecrystallization phenomenon be observed when melting of preformed lamellar crystals and recrystallization of thicker lamellae have similar free energy barrier.展开更多
The effect of PBS on the morphological features of PVDF has been investigated by optical and atomic force microscopies under various conditions. It was found that neat PVDF forms large γform spherulites with extraord...The effect of PBS on the morphological features of PVDF has been investigated by optical and atomic force microscopies under various conditions. It was found that neat PVDF forms large γform spherulites with extraordinarily weak birefringence at 170℃. Adding 30% PBS makes PVDF exhibit intrigued flower-like spherulitic morphology. The growth mechanism was explained by the decrease of the supercooling and the materials dissipation. Increasing the PBS content to 70% favors the formation of ring banded spherulites. Temperature dependent experiments verify the α→γ phase transition occurs from the junction sites of the ot and y crystals, while starts from the centers of α spherulites in the blends. Ring banded structures could be observed in neat PVDF, 70/30 blend and 30/70 blend when crystallized at 155℃, without γ crystals. The band period of PVDF α spherulites increases with crystallization temperature as well as the amount of PBS content. At 140℃, spherulites in neat PVDF lose their ring banded feature, while coarse spherulites consisting of evident lamellar bundles could be found in 30/70 blend.展开更多
Development of home compostable materials based on bioavailable polymers is of high strategic interest as they ensure a significant reduction of the environmental footprint in many production sectors.In this work,the ...Development of home compostable materials based on bioavailable polymers is of high strategic interest as they ensure a significant reduction of the environmental footprint in many production sectors.In this work,the addition of thermoplastic starch to binary PLA/PBAT blends was studied.The compounds were obtained by a reactive extrusion process by means of a co-rotating twin screw extruder.Thermomechanical,physical and chemical characterization tests were carried out to highlight the effectiveness of the material design strategy.The compounds were subsequently reprocessed by cast extrusion and thermoforming in order to obtain products suitable for the storage of hot food.The extruded films and the thermoformed containers were further characterized to highlight their thermo-mechanical,physical and chemical properties.Thermo-rheological,mechanical and physical properties of the material and of the cast film were analyzed thoroughly using combined technique as capillary rheometer,MFI,DSC,VICAT/HDT,XRD,FTIR,UV-Vis,SEM,permeability and,lastly,running preliminary chemical inertness and biodegradation tests.Particular attention was also devoted to the evaluation of the thermo-mechanical resistance of the thermoformed containers,where the PLA/PBAT/TPS blends proved to be very effective,also presenting a high disintegration rate in ambient conditions.展开更多
Poly（butylene succinate） （PBS） with different molecular weight was synthesized from 1, 4-butanediol and succinic acid by direct melt condensation. The synthesized PBS was identified by IH-NMR and FTIR spectrometry...Poly（butylene succinate） （PBS） with different molecular weight was synthesized from 1, 4-butanediol and succinic acid by direct melt condensation. The synthesized PBS was identified by IH-NMR and FTIR spectrometry. The molecular weight was calculated from the intrinsic viscosity, and its value was between 20000 and 70000. The crystallization behavior and crystal morphology as function of molecular weight were investigated by DSC and PLM, respectively. The mechanical properties and hydrolytic degradation behaviors related with change of molecular weight were also studied in this work. The results demonstrated that the properties of PBS were determined by both molecular weight and crystallization properties （crystallinity as well as crystal morphology）. Our work is important for the design and preparation of PBS with proper molecular weight for its practical application.展开更多
Biodegradable poly（butylene succinate） （PBS） and layered double hydroxide （LDH） nanocomposites were prepared via melt blending in a twin-screw extruder. The morphology and dispersion of LDH nanoparticles within ...Biodegradable poly（butylene succinate） （PBS） and layered double hydroxide （LDH） nanocomposites were prepared via melt blending in a twin-screw extruder. The morphology and dispersion of LDH nanoparticles within PBS matrix were characterized by transmission electron microscopy （TEM）, which showed that LDH nanoparticles were found to be well distributed at the nanometer level. The nonisothermal crystallization behavior of nanocomposites was extensively studied using differential scanning calorimetry （DSC） technique at various cooling rates. The crystallization rate of PBS was accelerated by the addition of LDH due to its heterogeneous nucleation effect; however, the crystallization mechanism and crystal structure of PBS remained almost unchanged. In kinetics analysis of nonisothermal crystallization, the Ozawa approach failed to describe the crystallization behavior of PBS/LDH nanocomposites, whereas both the modified Avrami model and the Mo method well represented the crystallization behavior of nanocomposites. The effective activation energy was estimated as a function of the relative degree of crystallinity using the isoeonversional analysis. The subsequent melting behavior of PBS and PBS/LDH nanocomposites was observed to be dependent on the cooling rate. The POM showed that the small and less perfect crystals were formed in nanocomposites.展开更多
Poly(butylene adipate-co-terephthalate)(PBAT)is a promising biodegradable flexible polymer but suffers from slow crystallization rate,making it less attractive for some applications like the injection-molded products ...Poly(butylene adipate-co-terephthalate)(PBAT)is a promising biodegradable flexible polymer but suffers from slow crystallization rate,making it less attractive for some applications like the injection-molded products in comparison with low-density polyethylene(LDPE).This work aimed to accelerate the crystallization of PBAT by adding a self-assembly nucleating agent octamethylenedicarboxylic dibenzoylhydrazide(OMBH).PBAT/OMBH composites with various OMBH contents(0 wt%,0.5 wt%,0.7 wt%,1 wt%,2 wt%,3 wt%and 5 wt%)were prepared through melt-mixing.The effect of OMBH on the crystallization behavior,morphologies and mechanical properties of PBAT was investigated.The highest nucleation efficiency value of 59.6%was achieved for PBAT with 0.7 wt%OMBH,much higher than that of 22.7%for PBAT with 0.7 wt%talc.Atomic force microscopy results showed that OMBH formed fine fibers and induced the formation of transcrystalline layers of PBAT.Fourier transform infrared spectroscopy(FTIR)combined with two-dimensional correlation spectra suggested that the intermolecular dipole-dipole N—H…O=C interactions but not hydrogen bond between OMBH and PBAT promoted the crystallization of PBAT in the initial period of crystallization.The presence of OMBH did not change the crystal form of PBAT but had positive contribution in enhancing its crystallinity and mechanical properties.This work is essential for preparing PBAT with high crystallization rate,enhancing its potential applications in injection-molded products.展开更多
The degradation of thermoplastic starch blend in the presence of commerciala-amylase and unpurified amylase of microbial origin was investigated.The blends consisting of thermoplastic starch and poly(butylene succinat...The degradation of thermoplastic starch blend in the presence of commerciala-amylase and unpurified amylase of microbial origin was investigated.The blends consisting of thermoplastic starch and poly(butylene succinate)have potential use in packaging applications thus,it is essential to establish susceptibility to degradation.Molar mass loss,gravimetric weight loss,and molecular structure were evaluated.The changes in the surface were observed with scanning electron microscopy.It was confirmed that there was a significant difference in gravimetric weight loss between the blends degraded in two different solutions.Unpurified enzymes of microbial origin,produced by Rhizopus oryzae cultures decomposed analyzed materials more efficiently than purified commercial ones.Moreover,it was proved that in applied conditions,the molar mass of PBS fraction did not change significantly.展开更多
The correlation between ring-opening polymerization （ROP） of cyclic butylene terephthalate （CBT） and crystallization of polymerized CBT （pCBT） strongly affected the final properties of pCBT and its composites. T...The correlation between ring-opening polymerization （ROP） of cyclic butylene terephthalate （CBT） and crystallization of polymerized CBT （pCBT） strongly affected the final properties of pCBT and its composites. The major objective of this contribution is to pinpoint the threshold temperature between them and the interrelation is successfully disclosed. That is, crystallization during polymerization occurs below 204 ℃ and the crystallization properties of pCBT are determined by this isothermal ROP stage; polymerization and crystallization are gradually separated with the increase of temperature of ROP （Tp） from 204 ℃, and the crystallization properties of pCBT are dominated by cooling stage; only polymerization is performed above 212 ℃. Moreover, quantitative analysis suggests that uniform crystal size distributions and thicker lamellar crystals derive from the stage of crystallization during polymerization. On the contrary, the crystal size distributions become wider above 204 ℃ of Tp and lead to obvious double melting peaks during heating scan. These efforts provide a very useful guide for the related investigation and application of CBT.展开更多
The main aim of this research was to investigate the synergistic influence of additives and poly（butylene succinate）（PBS） in improving both the mechanical and flame retardant properties of polylactide（PLA） blend...The main aim of this research was to investigate the synergistic influence of additives and poly（butylene succinate）（PBS） in improving both the mechanical and flame retardant properties of polylactide（PLA） blends. Tricresyl phosphate（TCP） and montmorillonite（MMT） were the additives used to improve the mechanical characteristics and fire resistance of PLA. Differential scanning calorimetry（DSC） thermograms revealed that the addition of TCP and MMT significantly affected their thermal behaviors. The results of the mechanical and morphological characterizations were in agreement with the changes in thermal behavior. The impact strength and limiting oxygen index（LOI） value of PLA significantly increased with the presence of PBS. The failure mode of the blends as evidenced by scanning electron microscopy（SEM） changed from brittle to ductile. The addition of TCP and MMT produced excellent anti-dripping and self-extinguishing behaviors of the blends, achieving V-0 rating. For the PLA/PBS blends, the synergistic combination of PBS and additives led to an acceleration of cold crystallization, a significant increment of flexibility and impact toughness, and an improvement of flame retardancy.展开更多
Oriented and non-oriented Teflon films, which were found to have the same crystalline structure, but different surface morphologies, were used to sandwich poly（butylene adipate） （PBA） films during isothermal cryst...Oriented and non-oriented Teflon films, which were found to have the same crystalline structure, but different surface morphologies, were used to sandwich poly（butylene adipate） （PBA） films during isothermal crystallization. It was found that both the Teflon surface structure and the PBA polymorphic structure are the determining factors to induce epitaxial crystallization. The oriented Teflon film was able to induce epitaxial crystallization of PBA α crystal, while the non-oriented Teflon did not induce any epitaxial crystallization of PBA. Epitaxial crystallization did not occurred for PBA β crystals between neither the oriented nor the non-oriented Teflon films. The enzymatic degradation rate of PBA films was not determined by the epitaxial crystallization, in fact it was still dependent on the polymorphic crystal structure of PBA. The morphological changes of PBA films after enzymatic degradation confirmed again that the epitaxial crystallization only occurred for the PBA film with α crystal structure which was produced by being sandwiched between oriented Teflon films, and it happened only on the surface of PBA films.展开更多
A low-molecular-weight polylactide-poly(butylene succinate)(PLA-PBS)copolymer was synthesized and incorporated into polylactide(PLA)as a novel toughening agent by solvent casting.The copolymer had the same chemical st...A low-molecular-weight polylactide-poly(butylene succinate)(PLA-PBS)copolymer was synthesized and incorporated into polylactide(PLA)as a novel toughening agent by solvent casting.The copolymer had the same chemical structure and function as PLA and it was used as a plasticizer to PLA.The copolymer was blended with PLA at a weight ratio from 2 to 10 wt%.Phase separation between PLA and PLA-PBS was not observed from their scanning electron microscopy(SEM)images and the crystal structure of PLA almost remained unchanged based on the X-ray diffraction(XRD)measurement.The melt flow index(MFI)of the blends was higher as the amount of PLA-PBS increased,indicating that the block copolymer did improve the mobility of the PLA chains.Moreover,tensile tests revealed that PLA with greater PLA-PBS copolymer exhibited higher elongation at break and it reached the maximum at 8 wt%of PLA-PBS in PLA,which was around 6 times higher than that of pure PLA.Furthermore,the glass transition temperature,measured by differential scanning calorimetry(DSC),markedly decreased with an increasing amount of the copolymer as it decreased from 61.2℃ for pure PLA to 41.3℃when it was blended with 10 wt%PLA-PBS copolymer.Therefore,the PLA-PBS copolymer was shown to be a promising plasticizer for fully biobased and toughened PLA.展开更多
Poly(glycolic acid)(PGA)is derived from glycolide obtained by fermenting pineapples or sugarcane,which has excellent gas barrier properties and a small carbon footprint.PGA is a potential substitute for the current al...Poly(glycolic acid)(PGA)is derived from glycolide obtained by fermenting pineapples or sugarcane,which has excellent gas barrier properties and a small carbon footprint.PGA is a potential substitute for the current aluminum-plastic composite films used in high barrier packaging applications.However,its poor ductility and narrow processing window limit its application in food packaging.Herein,poly(butylene succinate-co-butylene adipate)(PBSA)was used to fabricate PGA/PBSA blend films through an in situ fibrillation technique and blown film extrusion.Under the elongational flow field used during the extrusion process,a unique hierarchical structure based on the PBSA nanofibrils and interfacially oriented PGA crystals was obtained.This structure enhances the strength,ductility and gas barrier properties of the PGA/PBSA blend film.In addition,an epoxy chain extender(ADR4468)was used as a compatibilizer to further enhance the interfacial adhesion between PGA and PBSA.70PGA/0.7ADR exhibited a very low oxygen permeability(2.34×10^(-4)Barrer)with significantly high elongating at break(604.4%),tensile strength(47.4 MPa),and transparency,which were superior to those of petroleum-based polymers.Thus,the 70PGA/0.7ADR blown films could satisfy the requirements for most instant foods such as coffee,peanuts,and fresh meat.展开更多
基金supported by the Sichuan Provincial Regional Innovation Cooperation Project(No.2024YFHZ0159).
文摘Semicrystalline polymers usually undergo multilevel microstructural evolutions with annealing and stretching processes,which is es-sential to tailor the physical properties of the polymer.Here,poly(butylene carbonate)(PBC)sheets were prepared via isothermal annealing and unidirectional pre-stretching processes,then the changes of PBC in crystallinity,mechanical properties,thermal properties and microscopic changes before and after annealing and stretching were measured,as well as the relationship between microstructure and macroscopic proper-ties before and after stretching.The strengthening mechanism of PBC was also described.It was demonstrated that shish-kabab structure emerged under the pre-stretching process.With the increase of the tensile ratio,the crystallinity,structure and mechanical properties are in-creased differently.Among them,the crystallinity and tensile strength after annealing-stretching treatment increased to 24.45%and 104.5 MPa,respectively,which were about 1.55 times and 3.4 times of those-without any treatment.
基金financially supported by the National Natural Science Foundation of China(Nos.21204045 and 21276151)Natural Science Basic Research Plan in Shaanxi Province of China(No.2011JQ2004)Key Scientific Research Group of Shaanxi Province(No.2013KCT-08)
文摘The effects of crystallization temperature and blend ratio on the polymorphic crystal structures of poly（butylene adipate） （PBA） in poly（butylene succinate） （PBS）/poly（butylene adipate） （PBS/PBA） blends were studied by means of differential scanning calorimetry （DSC）, wide-angle X-ray diffraction （XRD） and atomic force microscopy （AFM）. It was revealed that the polymorphism of PBA can be regulated by the blend ratio even in a non-isothermal crystallization process. The results demonstrate that high temperature favors fiat-on α crystals, while low temperature contributes to edge-on β crystals. It was also found that the effect of blend ratio on the crystallization mechanism of PBA is well coincident with that of the crystallization temperature. The increment of PBS content in the PBS/PBA blend gives rise to more β-form crystals of PBA. For those PBS/PBA blends with low PBA content, the interlamellar phase segregation of PBA makes its molecular chains so difficult to diffuse from one isolated microdomain to another that high crystallization temperature and sufficiently long crystallization time will be required if the PBA α-type crystals are targeted.
文摘In order to improve the wettability and biocompatibility of the poly （butylene terephthalate） non-woven （PBTNW）, the method of surface modification is used to graft copolymerization of chitosan （CS） onto the PBTNW under alkylpolyglycoside （APG） inducing. The product is thoroughly characterized with the Fourier transform infrared spectroscopy （FrIR）, the electron spectroscopy for chemical analysis （ESCA）, the thermogravimetric （TG） and the scanning electron microscopy （SEM）. It is found that chitosan is successfully grafted onto PBTNW. In addition, the water contact angles, hemolysis tests and cytotoxicity evaluation tests show an improvement in wettability and biocompatihility as a result of graft copolymerization of chitosan. So the CS-grafted PBTNW exhibits greater superiority than the original PBTNW. The CS-grafted PBTNW can be a candidate for blood filter materials and other medical applications.
基金financially supported by the National Key Research and Development Program of China(No.2016YFC0501402)Science and Technology Services Network Program of Chinese Science Academy(STS Project)(No.KFJSTS-ZDTP-082)Chinese Academy of Sciences(Changchun Branch)(Nos.2020SYHZ0002 and No.2020SYHZ0047)。
文摘A biodegradable blend foaming material of poly(butylene adipate-co-terephthalate)(PBAT)/poly(propylene carbonate)(PPC)was successfully prepared by chemical foaming agent and screw extrusion method.First,PBAT was modified by bis(tert-butyl dioxy isopropyl)benzene(BIBP)for chain extension,and then the extended PBAT(E-PBAT)was foamed with PPC using a twin(single)screw extruder.By analyzing the properties of the blends,we found that Young’s modulus increased from 58.8 MPa of E-PBAT to 244.7 MPa of E-PBAT/PPC 50/50.The viscosity of the polymer has a critical influence on the formation of cells.Compared with neat PBAT(N-PBAT),the viscosity of E-PBAT increased by 3396 Pa·s and E-PBAT/PPC 50/50 increased by 8836 Pa·s.Meanwhile,the dynamic mechanical analysis(DMA)results showed that the storage modulus(E’)at room temperature increased from 538 MPa to 1650 MPa.The various phase morphologies(“sea-island”,“quasi-co-continuous”and“cocontinuous”)and crystallinity of the blends affected the spread velocity of gas and further affected the foaming morphology in E-PBAT/PPC foam.Therefore,through the analysis of phase morphology and foaming mechanism,we concluded that the E-PBAT/PPC 70/30 component has both excellent strength and the best foaming performance.
基金supported by the Research Fund at the Shaanxi Provincial Science and Technology Department of China (No. 2018SF-375)Beijing Key Laboratory of Plastics Health and Safety Quality Evaluation Technology, Beijing Technology and Business University (No. TQETJP2018 004)。
文摘In recent years, poly(butylene adipate-co-terephthalate)(PBAT) has been widely used. However, PBAT-degrading bacteria have rarely been reported. PBAT-degrading bacteria were isolated from farmland soil and identified. The effects of growth factors on the degradation of PBAT and the lipase activity of PBAT-degrading bacteria were assessed. The degradation mechanism was analyzed using scanning electron microscopy, attenuated total reflection Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, Xray diffraction, and liquid chromatography-mass spectrometry. The results showed that Stenotrophomonas sp. YCJ1 had a significant degrading effect on PBAT. Under certain conditions, the strain could secrete 10.53 U/m L of lipase activity and degrade 10.14 wt.% of PBAT films. The strain secreted lipase to catalyze the degradation of the ester bonds in PBAT, resulting in the production of degradation products such as terephthalic acid, 1,4-butanediol, and adipic acid. Furthermore, the degradation products could participate in the metabolism of YCJ1 as carbon sources to facilitate complete degradation of PBAT, indicating that the strain has potential value for the bioremediation of PBAT in the environment.
基金financially supported by the fund of Science&Technology Bureau of Jilin Province of China(No.20126023)the National High Technology Research and Development Program of China(863 Program)(No.2012AA062904)the National Natural Science Foundation of China(No.51021003)
文摘Poly（propylene carbonate） （PPC） was melt blended in a batch mixer with poly（butylene carbonate） （PBC） in an effort to improve the toughness of the PPC without compromising its biodegradability and biocompatibility. DMA results showed that the PPC/PBC blends were an immiscible two-phase system. With the increase in PBC content, the PPC/PBC blends showed decreased tensile strength, however, the elongation at break was increased to 230% for the 50/50 PPC/PBC blend. From the tensile strength experiments, the Pukanszky model gave credit to the modest interfacial adhesion between PPC and PBC, although PPC/PBC was immscible. The impact strength increased significantly which indicated the toughening effects of the PBC on PPC. SEM examination showed that cavitation and shear yielding were the major toughening mechanisms in the blends subjected the impact tests. TGA measurements showed that the thermal stability of PPC decreased with the incorporation of PBC. Rheological investigation demonstrated that the addition of PBC reduced the value of storage modulus, loss modulus and complex viscosity of the PPC/PBC blends to some extent. Moreover, the addition of PBC was found to increase the processability of PPC in extrusion. The introduction of PBC provided an efficient and novel toughened method to extend the application area of PPC.
基金supported by the Science and Technology Development Plan of Jilin Province(Nos.20210203199SF and 20210509017RQ)the Science and Technology Development Program of Yantai of China(No.2022ZDCX015)+2 种基金the Chinese Academy of Sciences(Changchun Branch)(Nos.2021SYHZ0044 and 2021SYHZ0042)Science and Technology Bureau of Changchun City of China(Nos.21SH13 and 21KY01)Development and Reform commission of Jilin Province of China(No.2021C039-2).
文摘Binary biodegradable polymers films, poly(butylene adipate-co-terephthalate)(PBAT) and poly(glycolic acid)(PGA), were prepared through batch melt mixing to obtain Film Ⅰ and Film Ⅱ under two different processing conditions. PGA crystals played a major role in enhancing the mechanical and barrier properties of the films. For Film Ⅰ, there were initial PGA crystals before the film blowing process, the PGA molecular chain further crystallized, forming the oriented crystallization of PGA. Moreover, the Xcand crystalline size in Film Ⅰ were higher than those in Film Ⅱ. Compared with the different processing methods, Film Ⅰ has excellent mechanical and oxygen barrier properties due to the crystallization and orientation. The tensile strength reached 45.0 MPa, and tear strength exceeded 138.2 kN/m, while the elongation at break was as high as 750% for PBAT/PGA 85/15 in Film Ⅰ. The WVTR, WVP coefficients, and OP coefficients of PBAT/PGA films were decreased obviously with increasing the PGA content both in Film Ⅰ and Film Ⅱ. Moreover, the barrier properties of oxygen in Film Ⅰ were better than that in Film Ⅱ. This work reveals a feasible processing technique by introducing of initial crystallization of PGA to blow PBAT/PGA films with excellent mechanical and barrier properties.
基金financially supported by the company MBD Texinov(France)the company Roquette Frères(France)+4 种基金the ANRTthe framework of the collaborative project Agroboost funded by BPI FranceRhone-Alpes RegionRhone-Alpes FEDERthe Basse Normandie Regional Council
文摘A series of branched poly（butylene succinate）（PBS） were synthesized with several branching agents namely trimethylol propane（TMP）, malic acid, trimesic acid, citric acid and glycerol propoxylate. The structure of the branched polymers was analyzed by SEC and ~1H-NMR. The effect of branching agent structure on crystallization was also investigated and played a significant role. Isothermal studies showed that glycerol propoxylate could act as a nucleating agent. By contrast high content of TMP disturbed the regularity of the chain and hindered the crystallization of PBS. From the non-isothermal kinetic study, it was found that glycerol propoxylate increased noticeably the crystallization rate due to the flexible structure of the branching agent. A secondary nucleation was observed with glycerol propoxylate attributed to the crystallization of amorphous fraction included between crystallites formed at the primary crystallization. Chain topology was obtained through rheological investigations and the synthesized polymers showed a typical behavior of a mixture of linear and randomly branched PBS. The incorporation of branches improved the processability of PBS for film blowing application and the modulus and the stress at break of the resulting film were significantly increased.
基金financially supported by the National Natural Science Foundation of China(No.21374054)the SinoGerman Center for Research Promotion and the National Basic Research Program of China(No.2014CB932202)
文摘Differential scanning calorimetry（DSC） has been widely applied to study crystallization and melting of materials. However, for polymeric lamellar crystals, the melting thermogram during heating process usually exhibits a broad endothermic peak or even multiple endotherms, which may result from changes of metastability via recrystallization process. Sometimes, the recrystallization exotherm cannot be observed due to its overlapping with the melting endotherm. In this work, we employed a step heating procedure consisting of successive heating and temperature holding stages to measure the metastability of isothermally crystallized poly（butylene succinate）（PBS） crystals. With this approach we could gain the fraction of crystals melted at different temperature ranges and quantitatively detect the melting-recrystallization behavior. The melting-recrystallization behavior depends on the polymer chain structure and the crystallization temperature. For instance, PBS block copolymer hardly shows recrystallization behavior while PBS oligomer and high molecular weight PBS homopolymer demonstrate remarkable melting-recrystallization phenomenon. High molecular weight PBS isothermally crystallized in the low temperature range shows multiple melting-recrystallization while those isothermally crystallized at elevated temperatures do not exhibit observable recrystallization behavior. Furthermore, the melting endotherms were fitted via the melting kinetics equations. The original isothermally crystallized lamellae demonstrate quite different melting kinetics from the recrystallized lamellar crystals that melt at the highest temperature range, which is attributed to the different degrees of stabilization. Finally, the mechanism of melting-recrystallization is briefly discussed. We propose that apparent meltrecrystallization phenomenon be observed when melting of preformed lamellar crystals and recrystallization of thicker lamellae have similar free energy barrier.
基金financially supported by the National Natural Science Foundations of China(No.20974011)the program of Introducing Talents of Discipline to Universities(No.B08003)
文摘The effect of PBS on the morphological features of PVDF has been investigated by optical and atomic force microscopies under various conditions. It was found that neat PVDF forms large γform spherulites with extraordinarily weak birefringence at 170℃. Adding 30% PBS makes PVDF exhibit intrigued flower-like spherulitic morphology. The growth mechanism was explained by the decrease of the supercooling and the materials dissipation. Increasing the PBS content to 70% favors the formation of ring banded spherulites. Temperature dependent experiments verify the α→γ phase transition occurs from the junction sites of the ot and y crystals, while starts from the centers of α spherulites in the blends. Ring banded structures could be observed in neat PVDF, 70/30 blend and 30/70 blend when crystallized at 155℃, without γ crystals. The band period of PVDF α spherulites increases with crystallization temperature as well as the amount of PBS content. At 140℃, spherulites in neat PVDF lose their ring banded feature, while coarse spherulites consisting of evident lamellar bundles could be found in 30/70 blend.
文摘Development of home compostable materials based on bioavailable polymers is of high strategic interest as they ensure a significant reduction of the environmental footprint in many production sectors.In this work,the addition of thermoplastic starch to binary PLA/PBAT blends was studied.The compounds were obtained by a reactive extrusion process by means of a co-rotating twin screw extruder.Thermomechanical,physical and chemical characterization tests were carried out to highlight the effectiveness of the material design strategy.The compounds were subsequently reprocessed by cast extrusion and thermoforming in order to obtain products suitable for the storage of hot food.The extruded films and the thermoformed containers were further characterized to highlight their thermo-mechanical,physical and chemical properties.Thermo-rheological,mechanical and physical properties of the material and of the cast film were analyzed thoroughly using combined technique as capillary rheometer,MFI,DSC,VICAT/HDT,XRD,FTIR,UV-Vis,SEM,permeability and,lastly,running preliminary chemical inertness and biodegradation tests.Particular attention was also devoted to the evaluation of the thermo-mechanical resistance of the thermoformed containers,where the PLA/PBAT/TPS blends proved to be very effective,also presenting a high disintegration rate in ambient conditions.
基金financially supported by the National Natural Science Foundation of China(No.51173112)
文摘Poly（butylene succinate） （PBS） with different molecular weight was synthesized from 1, 4-butanediol and succinic acid by direct melt condensation. The synthesized PBS was identified by IH-NMR and FTIR spectrometry. The molecular weight was calculated from the intrinsic viscosity, and its value was between 20000 and 70000. The crystallization behavior and crystal morphology as function of molecular weight were investigated by DSC and PLM, respectively. The mechanical properties and hydrolytic degradation behaviors related with change of molecular weight were also studied in this work. The results demonstrated that the properties of PBS were determined by both molecular weight and crystallization properties （crystallinity as well as crystal morphology）. Our work is important for the design and preparation of PBS with proper molecular weight for its practical application.
基金supported by the National High Technology Research and Development Program of China (863 Program No. 2009AA03Z319)the National Natural Science Foundation of China (Nos. 30870633, 31000427)the Fundamental Research Funds for the Central Universities (DUT12JB09)
文摘Biodegradable poly（butylene succinate） （PBS） and layered double hydroxide （LDH） nanocomposites were prepared via melt blending in a twin-screw extruder. The morphology and dispersion of LDH nanoparticles within PBS matrix were characterized by transmission electron microscopy （TEM）, which showed that LDH nanoparticles were found to be well distributed at the nanometer level. The nonisothermal crystallization behavior of nanocomposites was extensively studied using differential scanning calorimetry （DSC） technique at various cooling rates. The crystallization rate of PBS was accelerated by the addition of LDH due to its heterogeneous nucleation effect; however, the crystallization mechanism and crystal structure of PBS remained almost unchanged. In kinetics analysis of nonisothermal crystallization, the Ozawa approach failed to describe the crystallization behavior of PBS/LDH nanocomposites, whereas both the modified Avrami model and the Mo method well represented the crystallization behavior of nanocomposites. The effective activation energy was estimated as a function of the relative degree of crystallinity using the isoeonversional analysis. The subsequent melting behavior of PBS and PBS/LDH nanocomposites was observed to be dependent on the cooling rate. The POM showed that the small and less perfect crystals were formed in nanocomposites.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.52073261 and U1704162).
文摘Poly(butylene adipate-co-terephthalate)(PBAT)is a promising biodegradable flexible polymer but suffers from slow crystallization rate,making it less attractive for some applications like the injection-molded products in comparison with low-density polyethylene(LDPE).This work aimed to accelerate the crystallization of PBAT by adding a self-assembly nucleating agent octamethylenedicarboxylic dibenzoylhydrazide(OMBH).PBAT/OMBH composites with various OMBH contents(0 wt%,0.5 wt%,0.7 wt%,1 wt%,2 wt%,3 wt%and 5 wt%)were prepared through melt-mixing.The effect of OMBH on the crystallization behavior,morphologies and mechanical properties of PBAT was investigated.The highest nucleation efficiency value of 59.6%was achieved for PBAT with 0.7 wt%OMBH,much higher than that of 22.7%for PBAT with 0.7 wt%talc.Atomic force microscopy results showed that OMBH formed fine fibers and induced the formation of transcrystalline layers of PBAT.Fourier transform infrared spectroscopy(FTIR)combined with two-dimensional correlation spectra suggested that the intermolecular dipole-dipole N—H…O=C interactions but not hydrogen bond between OMBH and PBAT promoted the crystallization of PBAT in the initial period of crystallization.The presence of OMBH did not change the crystal form of PBAT but had positive contribution in enhancing its crystallinity and mechanical properties.This work is essential for preparing PBAT with high crystallization rate,enhancing its potential applications in injection-molded products.
文摘The degradation of thermoplastic starch blend in the presence of commerciala-amylase and unpurified amylase of microbial origin was investigated.The blends consisting of thermoplastic starch and poly(butylene succinate)have potential use in packaging applications thus,it is essential to establish susceptibility to degradation.Molar mass loss,gravimetric weight loss,and molecular structure were evaluated.The changes in the surface were observed with scanning electron microscopy.It was confirmed that there was a significant difference in gravimetric weight loss between the blends degraded in two different solutions.Unpurified enzymes of microbial origin,produced by Rhizopus oryzae cultures decomposed analyzed materials more efficiently than purified commercial ones.Moreover,it was proved that in applied conditions,the molar mass of PBS fraction did not change significantly.
基金financially supported by the National Natural Science Foundation of China(No.21364004)Gansu Province University Fundamental Research FundsDoctor Research Fund of Lanzhou University of Technology,China
文摘The correlation between ring-opening polymerization （ROP） of cyclic butylene terephthalate （CBT） and crystallization of polymerized CBT （pCBT） strongly affected the final properties of pCBT and its composites. The major objective of this contribution is to pinpoint the threshold temperature between them and the interrelation is successfully disclosed. That is, crystallization during polymerization occurs below 204 ℃ and the crystallization properties of pCBT are determined by this isothermal ROP stage; polymerization and crystallization are gradually separated with the increase of temperature of ROP （Tp） from 204 ℃, and the crystallization properties of pCBT are dominated by cooling stage; only polymerization is performed above 212 ℃. Moreover, quantitative analysis suggests that uniform crystal size distributions and thicker lamellar crystals derive from the stage of crystallization during polymerization. On the contrary, the crystal size distributions become wider above 204 ℃ of Tp and lead to obvious double melting peaks during heating scan. These efforts provide a very useful guide for the related investigation and application of CBT.
基金financially supported by Prince of Songkla University (No.SCI600593S)the Faculty of Science Research Fund,Prince of Songkla University (No.1-2558-02-006)Development and Promotion of Science and Technology Talents Project (DPST)
文摘The main aim of this research was to investigate the synergistic influence of additives and poly（butylene succinate）（PBS） in improving both the mechanical and flame retardant properties of polylactide（PLA） blends. Tricresyl phosphate（TCP） and montmorillonite（MMT） were the additives used to improve the mechanical characteristics and fire resistance of PLA. Differential scanning calorimetry（DSC） thermograms revealed that the addition of TCP and MMT significantly affected their thermal behaviors. The results of the mechanical and morphological characterizations were in agreement with the changes in thermal behavior. The impact strength and limiting oxygen index（LOI） value of PLA significantly increased with the presence of PBS. The failure mode of the blends as evidenced by scanning electron microscopy（SEM） changed from brittle to ductile. The addition of TCP and MMT produced excellent anti-dripping and self-extinguishing behaviors of the blends, achieving V-0 rating. For the PLA/PBS blends, the synergistic combination of PBS and additives led to an acceleration of cold crystallization, a significant increment of flexibility and impact toughness, and an improvement of flame retardancy.
基金financially supported by the National Natural Science Foundation of China(No.51025314)the Oticon Foundation in Denmark
文摘Oriented and non-oriented Teflon films, which were found to have the same crystalline structure, but different surface morphologies, were used to sandwich poly（butylene adipate） （PBA） films during isothermal crystallization. It was found that both the Teflon surface structure and the PBA polymorphic structure are the determining factors to induce epitaxial crystallization. The oriented Teflon film was able to induce epitaxial crystallization of PBA α crystal, while the non-oriented Teflon did not induce any epitaxial crystallization of PBA. Epitaxial crystallization did not occurred for PBA β crystals between neither the oriented nor the non-oriented Teflon films. The enzymatic degradation rate of PBA films was not determined by the epitaxial crystallization, in fact it was still dependent on the polymorphic crystal structure of PBA. The morphological changes of PBA films after enzymatic degradation confirmed again that the epitaxial crystallization only occurred for the PBA film with α crystal structure which was produced by being sandwiched between oriented Teflon films, and it happened only on the surface of PBA films.
文摘A low-molecular-weight polylactide-poly(butylene succinate)(PLA-PBS)copolymer was synthesized and incorporated into polylactide(PLA)as a novel toughening agent by solvent casting.The copolymer had the same chemical structure and function as PLA and it was used as a plasticizer to PLA.The copolymer was blended with PLA at a weight ratio from 2 to 10 wt%.Phase separation between PLA and PLA-PBS was not observed from their scanning electron microscopy(SEM)images and the crystal structure of PLA almost remained unchanged based on the X-ray diffraction(XRD)measurement.The melt flow index(MFI)of the blends was higher as the amount of PLA-PBS increased,indicating that the block copolymer did improve the mobility of the PLA chains.Moreover,tensile tests revealed that PLA with greater PLA-PBS copolymer exhibited higher elongation at break and it reached the maximum at 8 wt%of PLA-PBS in PLA,which was around 6 times higher than that of pure PLA.Furthermore,the glass transition temperature,measured by differential scanning calorimetry(DSC),markedly decreased with an increasing amount of the copolymer as it decreased from 61.2℃ for pure PLA to 41.3℃when it was blended with 10 wt%PLA-PBS copolymer.Therefore,the PLA-PBS copolymer was shown to be a promising plasticizer for fully biobased and toughened PLA.
基金the National Key Research and Development Program of China(No.2022YFB3704900)the National Natural Science Foundation of China(No.52073004)China National Tobacco Corporation Guizhou Company(No.2023XM24)。
文摘Poly(glycolic acid)(PGA)is derived from glycolide obtained by fermenting pineapples or sugarcane,which has excellent gas barrier properties and a small carbon footprint.PGA is a potential substitute for the current aluminum-plastic composite films used in high barrier packaging applications.However,its poor ductility and narrow processing window limit its application in food packaging.Herein,poly(butylene succinate-co-butylene adipate)(PBSA)was used to fabricate PGA/PBSA blend films through an in situ fibrillation technique and blown film extrusion.Under the elongational flow field used during the extrusion process,a unique hierarchical structure based on the PBSA nanofibrils and interfacially oriented PGA crystals was obtained.This structure enhances the strength,ductility and gas barrier properties of the PGA/PBSA blend film.In addition,an epoxy chain extender(ADR4468)was used as a compatibilizer to further enhance the interfacial adhesion between PGA and PBSA.70PGA/0.7ADR exhibited a very low oxygen permeability(2.34×10^(-4)Barrer)with significantly high elongating at break(604.4%),tensile strength(47.4 MPa),and transparency,which were superior to those of petroleum-based polymers.Thus,the 70PGA/0.7ADR blown films could satisfy the requirements for most instant foods such as coffee,peanuts,and fresh meat.
