Materials and Properties
ZHANG Chunbo, LIU Xuanbo, YAO Xuerong, SU Cui, SHI Hongwei, ZHANG Longgui, ZHANG Taoyi
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The phase structure of polymer blends directly affects the macroscopic properties of the materials； therefore， it is important to investigate the size and spatial distribution of each phase. In this work， the confocal Raman imaging technique was adopted to study the distribution of phases of PE⁃LD/EVOH blends in the horizontal and depth directions and 3D space in the compression⁃molded specimens. The phase structure of PE⁃LD/EVOH blends in 3D space was obtained at the first time， and the phase region visually corresponded to the chemical composition of the blends. The results indicated that the PE⁃LD/EVOH blends were immiscible system. 20 wt% EVOH could be dispersed in the PE⁃LD matrix in a regular cylindrical form with a diameter of the cylinder in the range of 3~6 μm. The introduction of polyethylene grafted with maleic anhydride （PE⁃g⁃MAH） made the phase structure change significantly from the regular to irregular shape， and the cross⁃section size was reduced to 2 μm. This indicates that PE⁃g⁃MAH can enhance the compatibility between PE⁃LD and EVOH significantly.
LIN Xuhang, QIAN Shanhua, ZHANG Wei, BIAN Da, NI Zifeng
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To improve the wear resistance of polytetrafluoroethylene （PTFE）， KH560⁃surface⁃modified and non⁃surface⁃modified tungsten trioxide （WO3） filled polytetrafluoroethylene composites were comparatively studied. The PTFE/nano⁃WO3 composites were prepared through cold pressing and sintering， and their mechanical and tribological properties were investigated by using material testing and wear testing machines. The effects of nano⁃WO3 content and surface modification on the properties of the composites were also investigated. The results indicated that grafting KH560 on the surface of nano⁃WO3 improved the compatibility between the PTFE matrix and modified nano⁃WO3 and thus improved the mechanical properties of the PTFE/nano⁃WO3 composites. Compared to pure PTFE， the composite containing 5 wt% modified nano⁃WO3 showed a decrease in tensile strength by 17.7 %， but an increase in elongation at break increased by 43.5 % and in bending strength by 16.1 %. Compared to the composites with unmodified nano⁃WO3， the introduction of modified nano⁃WO3 effectively improved the wear resistance of PTFE. The friction coefficient and wear rate of the composite containing 5 wt% modified nano⁃WO3 were reduced by 14.2 % and 73.4 %， respectively， compared to those of pure PTFE. The findings of this work will provide a technical reference for the application of PTFE and the research and development of new materials.
BO Haiwa, ZHAO Zhongguo, WANG Chouxuan, XUE Rong
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In this paper， PLA/PDLA/CNTs composites with low over diffusion and high conductivity were prepared by using a solution adsorption⁃melting method. The PDLA component in the composites plays a good role of volume repulsion in promoting the dispersion of CNTs and enhancing the crystalline properties of PLA， thus effectively regulating the conductive network structure of the composites. The conductivity of the composites showed an increasing trend at first and then tended to decrease with an increasing in the PDLA content. The composite containing 0.2 wt% PDLA and 0.6 wt% CNTs obtained an increase in electrical conductivity from 10-6 to 10-4 S/m， which were improved by two orders of magnitude. Its conductive percolation value was reduced to 0.45 wt% compared to the PLA/CNTs composite （0.58 wt%）. In addition， the introduction of CNTs and PDLA effectively improved the crystallization properties and complex viscosity of the compo⁃sites. The onset crystallization temperature and the maximum peak crystallization temperature of the composite with 0.5 wt% PDLA and 0.6 wt% CNTs increased by 30.6 ℃ and 20.8 ℃， respectively， compared to those of pure PLA. The mechanical investigation indicated that the tensile strength of the composites was further improved as a result of the synergistic effect of CNTs and PDLA. Therefore， the conductive network structure could be effectively regulated through incorporating PDLA into the PLA/CNTs composites， along with an improvement in the mechanical properties of the composites. This work provides a new method for improving the comprehensive performance of conductive composites.
SHEN Dantong, XUE Yuting, LI Rongjie, XU Fang, WENG Yunxuan
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Poly（lactic acid） （PLA）⁃based waterborne polyurethane （WPU） was synthesized using PLA⁃OH and hexamethylene diisocyanate as raw materials with different contents of 2，2⁃dimethylolbutyric acid （DMBA） as a hydrophilic chain extender. Then， the PLA⁃WPU adhesive film and ultrafine fiber synthetic leathers were prepared. The particle size of the PLA⁃WPU lotion decreased with an increase in the DMBA content， and however， its solid content increased. The resultant PLA⁃WPU superfine fiber synthetic leather also obtained an increase in the tensile strength and maximum load but a decrease in the water contact angle. The solid content of the PLA⁃WPU lotion containing 5.5 wt% DMBA reached 35.4 %， and its particle size was 196.37 nm. In this case， the tensile strength of PLA⁃WPU superfine fiber synthetic leather was 29.9 MPa， which was as about 1.7 times as that of the superfine fiber substrate. In addition， the water contact angle of the PLA⁃WPU superfine fiber synthetic leather decreased to 73 ° when the DMBA content increased to 5.5 %.
ZHANG Qingsong, LI Liangyong, CAO Weiqiang, CHENG Yanwen, PENG Tianxiang, WANG Juntong, LI Houyang
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To evaluate the effect of alkali treatment of coir⁃geotextile on the tensile properties of epoxy⁃based materials， two types of alkali solutions， NaOH and NaHCO3， were used for pretreating the coir⁃geotextile and the effects of alkali solution concentration and treatment time on the surface morphology of the coir⁃geotextile was investigated. The coir⁃geotextile with epoxy resin as a substrate was prepared. The results indicated that after the coir⁃geotextile was treated with 5 % NaOH solution for 6h and 10 % NaHCO3 solution for 96~168 h， the tensile enhancement effect on the epoxy⁃based materials presented good consistency， resulting in a maximum value. Based on the analysis of microstructure and FTIR， the surface contour of the coir fiber gradually showed more explicit characteristics with an increase in the treatment time with alkali solutions. Beyond the appropriate treatment time， the coir fiber showed a rougher surface， accompanied by a more apparent large⁃area corrosion phenomenon. The surface of coir fiber treated with 10 % NaHCO3 solution for 96~168 h is similar to that with 5 % NaOH solution for 6h. The treatment with an NaHCO3 solution did not damage the cellulose structure of the fiber surface and also did not increase the surface roughness of the fiber significantly.
WANG Xiaohui, DONG Liming, GU Junjie, YAO Bing, CHEN Yan, LI Jing
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A 2，6⁃monosubstituted bisphenol⁃A （BPA）⁃isophthalaldehyde （IPD） oligomerized phenolic resin with a number⁃average molecular weight of 1.150×103 g/mol and a polydispersion index of 1.004 was synthesized through microwave⁃assisted solution copolycondensation in an open system using BPA and potential biomass IPD as monomers. This potential biomass IPD has a low melting point， a weak π⁃π stacking interaction， and a slightly higher activity than terephthalaldehyde （TPD）. The structure of the as⁃synthesized phenolic resin was confirmed by 1H⁃NMR， 13C⁃NMR， and FTIR. A reversible thermochromic composite Nickel⁃based butadiene rubber （NiBR） film was prepared by using the as⁃synthesized phenolic resin as a color developing agent. The results indicated that the flexibility of BPA⁃IPD and partially generated carboxyl end groups of IPD facilitated to generate low⁃ and high⁃temperature eutectic phases with lower latent heat due to a low melting point and a weak π⁃π stacking interaction of IPD. This improved the crystallization limit in the low temperature eutectic phase and color changing speed of the NiBR film and enhanced its compatibility with 1，4⁃high cis⁃NiBR and stability. The total color difference of the NiBR film was optimized to be around 85 at 12~37 ℃ through a formula. The absorption⁃scattering color depth difference of the NiBR film were approximately 20 and 45 at visible light range of 480~600 and 600~660 nm， respectively， and its color changing speed was 2.14 s-1.
ZHAO Xiaohong, LU Xin
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Glycerol， sodium hexametaphosphate （SHMP）， and polyethylene glycol （PEG） were used to modify cassava starch， and then， the modified starch/PBAT/calcium carbonate composites were prepared. The modified starch and its composites were analyzed by using FTIR， XRD， SEM， DSC and TG. The influence of modified starch on the structure and properties of the composites was investigated. The results indicated that the outer plasticization of glycerol and the inner plasticization of PEG and SHMP changed the chemical structure of starch. The amorphous components of modified starch increased. The starch particles were changed from a full spherical shape to the irregular large one. The thermal stability of the modified starch was improved before 250 ℃ but deteriorated after 250 ℃， which is beneficial to its processing and thermal decomposition. There are differences in the crystallization and melting behavior of the starch modified with different modifiers. In the composites， there was no change in the original crystal forms of PBAT， calcium carbonate， and starch； however， the differences in compatibility led to differences in the thermal and mechanical properties of the composites. The modification of starch improved the toughness of the composites. The synergistic modification of glycerol， SHMP， and PEG resulted in the good compatibility of starch with PBAT and calcium carbonate， and the composites achieved the optimal comprehensive performance.
CHAI Songhua, DU Hongxiu, WU Kai, HUANG Rui, ZHOU Chici
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To explore the bonding behavior between the BFRP bars and concrete under dynamic loads， forward and reverse cyclic pull⁃out tests were conducted on the BFRP bars， and their bonding dynamic performance was studied. According to the experimental results， the bond stress⁃strain relationship curve shows that there is a bond behavior between the BFRP reinforcement and concrete under cyclic load， which undergoes four stages of stress characteristics as follows： elastic stage， crack propagation stage， crack closure stage， and friction stage； As the diameter of BFRP polymer bars increased， the bonding strength between the BFRP bars and concrete interface decreased. With an increase in the cycle number， the bond strength between the BFRP reinforcement and concrete decreased， the slip corresponding to the bond strength increased， the shear hysteresis area decreased， and the energy dissipation capacity decreased. Based on the experimental results， a prediction model suitable for calculating the bonding performance between the BFRP bars and concrete under cyclic loading was established， laying an experimental and theoretical foundation for the seismic and fatigue behaviors of the BFRP⁃reinforced concrete.
CHEN Zhengcong, LIN Rui, HE Yi, LI Song
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To evaluate the effect of graphene content on the properties of SBS⁃modified asphalt mixture， SBS⁃modified asphalt was used as a raw material and graphene as a modifier to prepare asphalt composites with graphene contents of 0.1， 0.2， and 0.3 wt%. The properties of the resultant modified asphalt mixture were evaluated， and their high temperature stability， low temperature crack resistance， and water were investigated. The optimal addition amount of graphene was determined according to the radar map. The modification mechanism of graphene for the SBS⁃modified asphalt was analyzed through fluorescence sampling microscope and SEM. The results indicated that the penetration of the modified asphalt mixtures decreased significantly but their softening point increased significantly due to the presence of graphene. Moreover， their ductility also decreased remarkably. In terms of road performance， the addition of graphene significantly improved the rutting resistance of the SBS⁃modified asphalt mixtures， whereas their low temperature crack resistance and water stability were slightly reduced. The radar map test results indicated that the modified asphalt mixtures obtained the best comprehensive performance at a graphene content of 0.2 wt%. In the mixing process of the SBS⁃modified asphalt with graphene， a lamellar structure and a large specific surface area of graphene make it easy to mix with asphalt molecules. Meanwhile， SBS can insert into graphene during the mixing process， resulting in stable physical crosslinking and improving the performance of the SBS⁃modified asphalt mixtures accordingly.
Processing and Application
CHEN Hao, JIAO Xiaolong, ZHU Ningdi, DONG Zhengyang, ZHANG Jianfeng, ZHAO Peng
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During the injection molding process， the polymer melt undergoes intricate changes in temperature and density， directly impacting the final product quality. An ultrasonic on⁃line measurement method for monitoring the temperature and density of the polymer melt during molding was proposed in this article， and the results validated the accuracy of this method through comparisons with alternative approaches. A non⁃sealed rheological mold with an open bottom was designed and manufactured. An acquisition platform was established for collecting the ultrasonic signals as well as the temperature and pressure signals. Following with the signal collection， analysis and computations were performed to derive the variation curve of ultrasonic velocity within the polymer melt. Through incorporating the pressure and temperature signals， the computational analysis of melt information during injection molding was conducted. The experimental results demonstrated that the ultrasonic velocity signal could qualitatively reflect the melt evolution process within the mold cavity without a damage. Through leveraging the pressure signal， the iterative calculations of melt temperature were performed， showing an error of less than 6 % compared to the results from infrared fiber⁃optic temperature sensors. This resulted in a quantified analysis of polymer melt temperature with a minimal degradation. Through separating the time/frequency domain analyses of the ultrasonic signal， the changes in the acoustic impedance and sound velocity were obtained， enabling the calculation of the evolving density curve of the melt. This curve closely aligned with the results obtained through the pressure⁃volume⁃temperature method， presenting a mere mean squared deviation of 0.040 3 g/cm3. As a result， the non⁃destructive quantitative measurement of polymer melt density was achieved. This ultrasonic measurement technology enables the real⁃time monitoring of polymer melt information in injection molding， exhibiting vast potential applications in the practical production processes.
LYU Moyu, LIU Xuejun, MENG Chunling
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First， temperatures at mold surface and inside mold， and heating time and consumed electricity were measured by means of experiments for electric⁃heating empty mold and rotational molding process to make liner of hydrogen cylinder with four different thicknesses， and the heating efficiency and magnification factor were calculated in the five cases based on these measurements. Then， a computational method for the design of electric⁃heating rotational molding process was proposed. After the material and mass of mold， physical properties and mass of the powders inside the mold， and process parameters were defined， the effective thermal energy was calculated at first， and then the thermal energy from heating wire required in heating phase was estimated according to the magnification factor. As a result， the full load heating power and length of heating wire were obtained. The model of static bed was applied to simulate the heating time and thermal energy actually required from heating wire with the aid of the FLUENT software. The application steps of the method were illustrated through an electric⁃heating rotational molding process to make a hollow plastic cube. The influence of the full load heating power and mold material on the heating efficiency and the heating time and thermal energy actually required from heating wire was investigated. The results indicated that the heating efficiency decreased with an increase in the thickness of the liner of hydrogen cylinders. The heating time decreased slowly with an increase in the full load power. In the application of the steel mold， the heating time became longer， and more thermal energy from heating wire was required compared to the application of an aluminum mold.
JIANG Shu, WANG Yang, ZHAI Menglei, LI Qingtao, HUANG Ming, LIU Chuntai
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At present， the composites with short or long fibers as reinforcement have been widely used in automotive non⁃load⁃bearing parts. If the composites need to be further developed for the application in automotive main or secondary load⁃bearing parts， it is necessary to use continuous carbon fiber to improve their product strength and stiffness. However， in the forming process of continuous fiber⁃reinforced composites， the small elongation at break of carbon fiber makes it easy to cause molding defects such as fiber fracture， wrinkling， and tearing in the position of the large curvature. To solve this problem， the influence of the starting point and initial orientation of fiber laying on the overlay effect was analyzed theoretically through the simulation method of continuous fiber⁃reinforced composite laying with mold. To reduce fiber forming defects， the structural and overlay optimization design of continuous carbon⁃fiber reinforced B⁃pillar reinforced plate were carried out， and the geometry of B⁃pillar reinforced plate and the method of laying prepreg for the hot⁃pressing process were determined. Through the optimization of segmented overlay， the proportion of the unqualified layer at 0 °， 90 °， 45 °， and -45 ° was reduced from 45.18 %， 52.83 %， 72.21 %， and 71.78 % to 2.47 %， 3.45 %， 5.31 %， and 4.77 %， respectively. This indicated that the segmented overlay could effectively improve the lamination performance of the continuous carbon fiber. Based on the optimized overlay design， the B⁃pillar reinforced plate that meets the performance requirements has been successfully trial produced.
Plastic and Environment
HU Yanqing, HU Fan, ZHOU Jianchi, DOU Yibo
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This paper reviewed the research progress in the upcycling of waste plastics from physical⁃mechanical recycling to the chemical upcycling of plastic waste. The elucidation and analysis of advanced chemical catalytic methods， including， thermal catalysis， microwave catalysis， bio⁃catalysis， electro⁃catalysis， and photocatalysis， were introduced， which exhibited great potential for a wide range of application. Moreover， the rational design， structure characterization of catalyst， and performance evaluation on the upcycling of waste plastics were also systemically introduced. Especially， the yield， selectivity， and reaction mechanisms of plastic treatment were discussed. In addition， the advantages and disadvantages of various methods were comparatively presented. Based on the current progress in the waste plastic recycling， some insights into the challenges and future directions in this field were proposed to provide guidance for the recycling of plastics into high⁃value⁃added chemicals.
Machinery and Mould
LIU Qingdong
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The Kawasaki motorcycle engine intake manifold has a complex structure. A two⁃step core⁃pulling mechanism was designed due to the presence of inclined holes in the holes as well as a strong core⁃pulling force somewhere. A lifter was designed on both stationary half and moving half. A plate was added to the three⁃plate mold for the inclined core⁃pulling on the stationary half. Aim at four parting surfaces on the mold， a sequential distance parting mechanism was designed. The results indicated that the mold structure is reasonable， reliable and can meet the requirements of production.
Review
ZHANG Xiaowei, LI Yue, HUA Ye, HU Fa
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This paper reviewed the permeation mechanism of gases in polymer materials in detail. The test methods for hydrogen permeability of polymer linings of Type IV hydrogen storage cylinders and domestic and international test standards were briefly introduced. The effects of test temperature， test pressure， and polymer material properties on the hydrogen permeability of the liner material were further discussed along with the trend of the development direction in future.
GONG Qiang, JIN Zhiming
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This paper introduced the applications of model algorithms in the injection molding technology and summarized the predictive control effectiveness of relevant model algorithms in various stages of injection molding. Finally， proposes the future research directions in quality predictive control of injection molding products were proposed together with the relevant technological development trends in model algorithms.
CHENG En, YE Donglei, CHENG Debao, TIAN Huafeng, ZHAO Xiaoying, XIANG Aimin
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This paper introduced the influence of the viscosity， conductivity， surface tension of solution， and volatility of solvent on the electrospinning preparation of nanofiber film， classification of electrospinning techieques and the gelatin⁃based nanofiber film using degradable gelatin and other substances as raw materials. The applications of electrospun gelatin⁃based nanofiber films in the edible， antibacterial and antioxidant films， tissue engineering， nanofiber dressing， and filtration were introduced.
MENG Fanyue, WEN Yue, LI Chen, GAO Shan
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This paper reviewed the composition， application status， and development trend of bio⁃based plastics and analyzed the aerobic degradation of microorganisms and the factors affecting the biodegradability of plastics. The problems and shortcomings in the current degradation process were also pointed out. Finally， the future applications of bio⁃based materials was prospected.
LI Xuan, HE Yu, MING Bai, ZHANG Xiaoyan, LIU Fuhua, LAI Sheng
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This paper introduced the development of polyimide （PI）⁃based friction materials briefly and reviewed the research progress in the preparation of PI composite friction materials by using hot molding， cold hot isostatic pressing， 3D printing， and other molding techniques such as injection molding and extrusion. Finally， the development prospect of the molding technologies for the PI⁃based friction materials was prospected. This paper will provide a useful reference for the development of high⁃performance PI⁃based friction materials.
Others
LIU Xue
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The main contents of the keynote reports of 3 academicians and 32 industry experts and professors at The First Forum on Technology Innovation and Application of Polymer Materials of the Journal of China Plastics were introduced， including the current situation， development trend and challenges of the plastics industry， functional polymer materials， special engineering plastics， flame retarded materials， foaming materials， elastomers， molding processing technology and equipment， international standardization， microplastics analysis and testing， carbon footprint management， high⁃value patent mining， etc.
