2023, 37 (4):
1-10;
Abstract (
236 )
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An intrinsically conductive TMBP/DABA thermosetting epoxy resin was prepared by using 3，3’，5，5’-tetramethylbifenol diglycyl ether （TMBP） containing diphenyl mesogenic unit as a raw material and 4， 4-diaminobenzanilide （DABA） containing aromatic amide mesogenic unit （DABA） as a curing agent. The resultant epoxy resin achieved a thermal conductivity as high as 0.33 W/（m·K）. Compared to the conventional bisphenol-A glycidyl ether （DGEBA）/4，4'-diaminodiphenyl methane （DDM） epoxy resin， the as-prepared epoxy resin obtained an increase in thermal conductivity by about 50 %. The out-of-plane and in-plane thermal conductivities of the composites reinforced with 75 wt% short-cut carbon fiber were increased by about 42.7 % and 40.2 %， respectively. The interface bonding strength between the TMBP/DABA matrix resin and short-cut carbon fiber （SCF） or continuous carbon fiber M55J was significantly improved by ultraviolet ozone oxidation method at an optimum modification time of 1 h. The thermal conductivity of the composite was also improved. The SCF/M55J/TMBP/BADA composites were prepared by using intrinsically conductive TMBP/DABA epoxy resin as a matrix resin and SCF and M55J as reinforcement fibers. The addition of SCF can simultaneously improve the thermal conductivities of M55J/TMBP/DABA unidirectional composite plates along the X， Y and Z axes， reaching maximum values of 98.07， 48.23 and 9.40 W/（m·K）， respectively. This work provides a new strategy for improving the comprehensive thermal conductance of composite materials.
2023, 37 (4):
11-16;
Abstract (
175 )
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22
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In this paper， poly （butylene adipate-co-terephthalate） （PBAT）/poly （lactic acid） （PLA）/dioctyl terephthalate （DOTP）/nano-ZnO composites were prepared by using a solvent casting method. Nano-zinc oxide was surface modified with stearic acid， and the effects of particle sizes and surface modification of nano-ZnO on the mechanical， thermal， hydrophobic， extraction and antibacterial properties of the composite films were investigated. The results indicated that the extraction resistance of the composite films was improved due to the replacement of the hydroxyl polar group on the surface of nano-ZnO with stearic acid. The entanglement of the long chain alkyl of stearic acid with polymer chains improved the compatibility of modified nano-ZnO with PBAT. The thermal properties of the composite films decreased with a decrease in the particle size of nano-ZnO but an increase in the addition amount of modified nano-ZnO. However， their extraction resistance increased. Moreover， the tensile strength of the composite films increased up to 13.8 MPa， and their hydrophobic properties increased up to a contact angle of 110 °. The antibacterial properties of the composite films were also enhanced with an increase in the antibacterial circle.
2023, 37 (4):
17-22;
Abstract (
204 )
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25
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Polylactic acid （PLA）/cellulose nanofiber （CNFs） nanocomposites were prepared through melt blending and injection molding， and the effect of CNFs on their crystallization behavior， rheological and mechanical properties were investigated. The results indicated that CNFs could be uniformly dispersed in the PLA matrix at a small content. CNFs can be used as a heterogeneous nucleating agent to induce the crystallization of PLA， improving the crystallization rate constant and reducing the half crystallization time. Compared to neat PLA， the nanocomposites with 5 wt% CNFs presented a decrease in the half crystallization time from 10.4 min to 2.9 min. The rheological experimental results demonstrated that the lubrication and dilution effects of CNFs reduced the storage modulus and loss modulus of PLA. Compared to neat PLA， the elongation at break of the nanocomposite containing 3 wt% CNFs was improved by 41.2 %.
2023, 37 (4):
23-29;
Abstract (
240 )
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23
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Poly（lactic acid） （PLA）/reed fiber （RF） blends with different contents of RF were prepared through melt blending， and the corresponding films were prepared by blow molding. The biodegradability properties of PLA/RF blending films were investigated in the presence of proteinase K， and their crystallization behavior and surface morpholo-gical evolution during the degradation of the samples were also determined by using differential scanning calorimetry （DSC） and scanning electron microscopy （SEM）. The results indicated that the enzymatic degradation of PLA was promoted by RF， and the enzymatic degradation rate of PLA/RF composites increased with an increase in the RF content. The degradation rate of composite films containing 30 wt% RF was the fastest， resulting in 81.11% degradation in 16 days. The addition of RF could reduce the crystallinity of PLA， affecting the degradation rate.
2023, 37 (4):
30-34;
Abstract (
169 )
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26
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Aiming to address the problems of slow retraction， small retraction force， and poor safety and reliability of common peroxide crosslinked polyethylene （PE-Xa） memory ring， a novel nano-silica （SiO2） modified PE-Xa memory ring was prepared， and the effect of crosslinking degree on the performance of the memory ring was investigated. The results indicated that the retraction speed and retraction force of the memory rings increased with an increase in crosslinking degree. The effect of surface treatment and addition of nano-SiO2 on the performance of the memory rings were investigated. The results indicated that nano-SiO2 was well dispersed due to the surface treatment with a silane coupling agent KH-570 as well as the mixing process at an ultra-high speed with a linear speed above 1 km/min. The addition of 1.5 % surface-treated nano-SiO2 could improve the retraction speed， retraction force and creep resistance of the memory ring greatly. The performance investigation indicated that the retraction speed and retraction force of the memory ring were better than those of the commercially available memory ring， and it passed the thermal stability test under the hydrostatic pressure specified in the standard of XLPE pipe as well as the hydrostatic pressure test specified in the system applicability.
2023, 37 (4):
35-38;
Abstract (
202 )
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20
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Biaxially oriented poly（vinyl chloride） （PVC-O） pipe segments were heated to make them undergo two disorientation at different degrees of complete disorientation and axial disorientation. Low temperature impact tests were carried out on the finished PVC-O pipe segments， fully disoriented pipe segments， axial disoriented pipe segments， and blank pipes. Axial tensile and radial tensile tests were carried out on the finished PVC-O pipe segments and axial disoriented pipe segments to analyze their mechanical properties before and after disorientation. The results indicated that the low temperature impact and axial tensile properties of the fully disoriented pipes decreased. The low temperature impact and axial tensile properties of the axial disorientated pipes also decreased， but their radial tensile properties showed little change.
2023, 37 (4):
39-45;
Abstract (
171 )
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22
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Two-component polyurethane （PU） sealants with an inorganic CaCO3 filler were developed to improve the performance for use as a high-speed railway sealing sealant. The surface morphology of polyurethane sealants with different contents of the CaCO3 filler was observed using a scanning electron microscope. The mechanical and adhesion properties of the PU sealant samples were analyzed and their heat and water resistance were evaluated. The results indicated that the inorganic filler could reduce the surface flatness of the sealants but improved their roughness. The appropriate addition amount of the CaCO3 filler enhanced the tensile strength， elongation at break， and modulus of the sealants； however， the excessive amount of the filler reduced their elongation at break. With the addition of the filler， the adhesion， heat resistance， and water resistance of the sealants were all improved considerably. In addition， the addition amount of 30 wt% CaCO3 filler was recommended for the PU sealants to achieved optimal comprehensive performances. The findings in this study provide a reference for enhancing the cost-effectiveness and performance of PU-based high-speed railway sealing sealants.
2023, 37 (4):
46-52;
Abstract (
182 )
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17
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Aiming at the easy contamination of pork by microorganisms along with a short shelf life， flavonoid compounds were extracted from Purslane through enzymatic hydrolysis， followed by ultrasonic-assisted alcohol extraction， and the antioxidant and bacteriostatic activity of the resultant Portulaca oleracea extract was investigated. The Portulaca oleracea extract and PVA composite film were applied for the preservation of pork to verify its bacteriostasis and preservation effects. The results indicated that the flavone extract of Portulaca oleracea L. had a scavenging activity on the OH and DPPH free radicals， and the scavenging rate of DPPH free radical was over 90 % at a flavone concentration of 0.02 mg/mL， exhibiting a high bacteriostasis effect on Staphylococcus aureus. When the ratio of Portulaca oleracea extract to PVA was 20∶30， the growth rates of total colony count， pH， H2S， MDA and TVB-N contents of chilled meat could be significantly inhibited， prolonging its shelf life.
2023, 37 (4):
53-59;
Abstract (
200 )
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Phosphating guar gum （DTGG） was obtained through the modification of guar gum （GG） with 9，10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide （DOPO） and 1，2，3，6-tetrahydrophthalic anhydride （THPA）， and its chemical structure was determined using Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. Flame-retardant poly（lactic acid） （PLA） blends were prepared through melt-blending PLA with DTGG as a carbon source and ammonium polyphosphate （APP） as acid and gas sources. The flame retardant properties of the resulting blends were investigated through vertical burning experiments （UL 94）， limiting oxygen index （LOI）， and the cone calorimeter tests， and their thermal properties and morphology were characterized through thermogravimetric analysis and field-emission scanning electron microscopy （FESEM）. The results indicated that the blends obtained an LOI value of 33.4 vol% at a DTGG/APP mass ratio of 9/11 and achieved a UL 94 V-0 classification in the vertical burning experiment. Meanwhile， the blends showed the lowest total heat release （THR） value， which decreased by 33.8% compared to that of pure PLA. The uniform distribution of DTGG and APP in the PLA matrix was found from the FESEM observation. The synergistic effect of DTGG and APP effectively enhanced the flame retardancy of PLA. The synergistic mechanism of DTGG and APP for the flame retardancy of PLA was also proposed.
2023, 37 (4):
60-66;
Abstract (
213 )
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Poly（butylene adipate terephthalate）（PBAT）/ poly（lactic acid）（PLA）（PBAT/PLA， 80/20）in-situ fibrillation blends were prepared by a single-screw melt-extrusion casting machine under various die temperature and stretching speed. The results indicated that at lower die temperature， with the increase of stretching speed， the diameter of PLA microfibers dwindles， the crystallinity degree enhance first and then lowers， the longitudinal tensile strength increases first and then decreases， and the mechanical anisotropy is obvious. When the die temperature was 150 ℃ and the stretching speed was 5.0 m/min， the number of dispersed phase PLA microfibers grow； the highest crystallinity of PBAT and PLA are 4.8 % and 23.7 %， respectively； the longitudinal tensile strength reaches the maximum of 29.8 MPa， which is at least 41 % higher than that of pure PBAT.
2023, 37 (4):
67-73;
Abstract (
276 )
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To regulate the pore structure of poly（lactic acid） （PLA） nanofibers， the nanofibers with an average diameter of 1.37 μm were prepared through electrospinning using PLA masterbatch as a raw material and the chloroform （CF）/N， N-dimethylformamide solution as a solvent， and their structures were investigated. The results indicated that the average diameter of the resultant nanofibers increased with an increase in the CF content， polymer concentration， and ambient humidity. With improving the spinning voltage and the filling speed， the average diameter tended to decrease. Meanwhile， environmental humidity has a significant effect on the pore structure of the fiber surface. The distribution density of pores on the fiber surface increased with an increase in humidity， and the shape varied from round to oval. In addition， the specific surface area of the as-prepared porous fiber was increased by 10 times （24.0 m2/g） compared to that of the PLA nanofibers with a smooth surface （2.4 m2/g）.
2023, 37 (4):
74-78;
Abstract (
192 )
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The performance of a foreign product and military anti?corrosion film （HP8714） was evaluated in terms of several key technical indicators， including water vapor transmission and vertical burning for 12 s， and the effects of adhesive type and content on the performance of the moisture barrier tapes were investigated by using ethyl acetate （EAC） as an adhesive solvent. The results indicated that the HP8714 TPU raw material （A198FR） could be used as a raw resin for the high?performance flame?retardant TPU moisture barrier tapes. With A198FR as the base material for barrier tapes， the pressure?sensitive adhesive， YY16， was determined as the most suitable adhesive at a preferred YY16/EAC mass ratio of 75/25. All of the property indexes were verified by third?party testing.
2023, 37 (4):
79-85;
Abstract (
209 )
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A series of poly（lactic acid） （PLA）/plasticized poly（vinyl alcohol） （CPVA） blends were prepared through melt mixing at different mass ratios of PLA to CPVA， and PLA/CPVA open-cell foams were prepared by using batch foaming and particle leaching methods with supercritical CO2 as a physical foaming agent. The results indicated that the crystallization temperature of PLA decreased significantly with an increase in the CPVA content， and its crystallinity increased at first and then decreased. Moreover， the melt viscoelasticity of the blends was improved. The volume expansion ratio （VER） of the open-cell foams decreased at first and then gradually increased with an increase in the CPVA content. Their open-cell content also increased. When the CPVA content reached 50 wt%， the VER of the open-cell foams was 23.1 times and their open-cell content reached 91.6 %.
2023, 37 (4):
86-94;
Abstract (
236 )
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28
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Catalytic co-pyrolysis of biomass and plastic is a promising way to improve bio-oil quality and mitigate the environmental issues caused by the disposal of petroleum-based waste plastics. In this study， the effects of in-situ and ex-situ catalytic modes on the performance of co-pyrolysis were investigated using HZSM-5 as a catalyst. Three types of catalysts， HY， HZSM-5 and Fe/HZSM-5， were then thoroughly characterized， and their effects on the performance of co-pyrolysis were also investigated. The in-situ mode resulted in a higher bio-oil yield compared to the ex-situ mode. However， the Diels-Alder and aromatization reactions were promoted in the ex-situ pyrolysis， leading to a higher aromatic selectivity of 82.8 %. The introduction of transition metal Fe improved the anti-coking ability； therefore， Fe/HZSM-5 had the least coke amounts of 3.77 wt% among the three catalysts. Compared to HZSM-5， Fe/HZSM-5 had a lower Br?nsted acid density， thus leading to a slight decrease in the selectivity of hydrocarbons but a dramatic increase in the selectivity of aromatics by 16.7 %. Owing to the coke deposition， the BET surface area， pore volume， and there was a decrease in the acidity of the three post-catalytic catalysts， lowering their catalytic ability.
2023, 37 (4):
95-103;
Abstract (
256 )
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This paper reviewed the research progress in the improvement of the material properties of polyhydroxybutyrate （PHB） through two different ways， physical blending and chemical structure modification. The modification methods included the melting blending with natural raw materials， inorganic filler， biodegradable resin， and the chemical structure modification through block/grafting. The future application prospect of PHB was future forecasted.
2023, 37 (4):
104-111;
Abstract (
275 )
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31
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This paper summarized the epoxidation process of waste cooking vegetable oil bio-based plasticizer and introduced three common epoxidation methods， including homogeneous acid catalysis， acidic ion exchange resin catalysis， and enzymes catalysis. The catalytic principle and characteristics were expounded separately. Finally， the application of waste cooking vegetable oil bio-based plasticizers was discussed and prospected.
2023, 37 (4):
112-120;
Abstract (
229 )
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This paper reviewed that the research status of polymer/graphene composites prepared through emulsion polymerization at home and abroad in recent years. The emulsion polymerization methods for the preparation of polymer/graphene composites were described in detail. The types of polymers in emulsion polymerization， the modification methods of graphene， the performance improvement of composites were summarized. The application fields and research directions of polymer/graphene composites prepared through emulsion polymerization were prospected.
2023, 37 (4):
121-135;
Abstract (
389 )
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27
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This article reviewed the recent research and manufacturing progresses of biodegradable grade biaxially oriented poly（lactic acid） （BOPLA） film， and intensively introduced two class biodegradable grade BOPLA films processed by basic and functional types. Moreover， the biaxially oriented processing technology in the improvement of resin matrix formulation， stretching temperature， stretching ratio， stretching rate and heat setting temperature as well as the introduction of method based on metallization technology of surface layer for the preparation of biodegradable grade BOPLA film were also introduced. Finally， development trend of biodegradable grade BOPLA film was prospected.
