Materials and Properties
TAN Jiao, WANG Junzhu, LI Shuai, LIU Xinye
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171 )
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In this study， the impact of phase⁃change microcapsules （PCM） on asphalt performance was investigated through a series of orthogonal experiments. These experiments focus on the evaluation of the effect of the urea⁃formaldehyde （melamine⁃urea⁃formaldehyde） resin as a shell material and n⁃tetradecane as a core material on the synthetic efficiency of PCM. The optimal preparation process for PCM was analyzed. Differential scanning calorimetry and dynamic shear rheology were employed to assess the performance of the PCM⁃modified asphalt （referring to as phase change bitumen）. The findings indicated that the most effective synthetic parameters were determined for PCM at an emulsifier concentration of 7 wt.%， an emulsification speed of 2 000 r/min， a mass ratio of core to wall material of 1∶1， a 1∶7 oil⁃to⁃water volume ratio， a synthetic time of 90 min， and a reaction temperature of 80 ℃. Under such conditions， PCM exhibited a latent heat of 117 J/g. Furthermore， the microcapsule shell presented excellent sealing properties， ensuring the stability of asphalt within the range required for construction temperature. The PCM⁃modified asphalt showed an exothermic interval from -7.1 to -17.9 ℃ and an endothermic interval from 2.3 to 13.5 ℃. The PCM⁃modified asphalt presented a phase⁃change enthalpy of 5.1 J/g at a microcapsule concentration of 7 wt.%. More importantly， the incorporation of PCM effectively slowed down the hardening process of the PCM⁃modified asphalt and maintained its stability at room temperature. The developed phase⁃change asphalt exhibits great potential for application.
PANG Xinlei, BAI Yu, WANG James H
Abstract (
118 )
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Polyether ether ketone （PEEK） oligomers were synthesized through a solution reaction using sulfolane as a solvent， the resultant oligomers were employed to synthesize high melt viscosity PEEK through solid⁃state polymerization in a twin⁃roller mixer. The effects of polymerization time on the crystallization properties， thermal properties and flowability of PEEK were investigated. The results indicated that both the degree of crystallinity and crystallization completeness of PEEK decreased with an increase in polymerization time. The degree of crystallinity of PEEK after polymerization for 5 h decreased by about 31.4 % as compared to that of the oligomers. All samples possessed residual weights greater than 50 % at 900 ℃， indicating outstanding thermal stability. In addition， the melt viscosities of PEEKs increased significantly with an increase in the polymerization time， and it reached approximately 13~360 times as high as that of oligomers.
MA Jianxin, WANG Guoliang, DU Zhongjie, WANG Wucong, JIN Hua, ZOU Wei, WANG Hong, ZHANG Chen
Abstract (
160 )
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Hydroxy⁃functionalized polyacrylate rubber particles （ACR⁃OH） were synthesized with micro⁃crosslinked polybutyl acrylate （PBA） as a rubber core and methyl methacrylate⁃hydroxyethyl acrylate copolymer （HEA） as a shell through seed emulsion polymerization. ACR⁃OH was mixed with triglycidyl isocyanurate （TGIC） and then added into polybutylene terylene phthalate （PBT）. Owing to the reactions occurring between the hydroxyl groups on the surface of ACR particles and epoxy groups in TGIC and between the epoxy groups in TGIC and hydroxyl end⁃group of PBT in the melt blending process， the modified PBT （PBT/TGIC/ACR⁃OH） gained the good compatibility between ACR and PBT. The effect of the addition of ACR⁃OH and TGIC on the impact strength and tensile strength of the modified PBT were investigated. The results indicated that the addition of ACR⁃OH effectively improved the toughness of PBT due to good compatibility. When the addition amounts of ACR⁃OH and TGIC were 20 and 2 phr， respectively， the impact strength of the modified PBT reached 20.45 kJ/m2， which was 8.4 times as high as that of pure PBT （2.43 kJ/m2）. Moreover， with the help of multi⁃functional TGIC， the modified PBT exhibited both good toughness and good strength at addition amounts of ACR⁃OH and TGIC of 8 and 2 phr， respectively. Its impact strength and tensile strength reached 10.87 kJ/m2 and 42.1 MPa， respectively.
SHEN Wentao, HU Xinrui, ZHANG Shuo, XU Miaojun
Abstract (
167 )
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A nickel⁃containing metal⁃organic framework material （MOF⁃74）， piperazine pyrophosphate （PPAP）， and a triazine charring foaming agent （CFA） were homogeneously mixed at a certain mass ratio and then incorporated into ethylene⁃vinyl⁃acetate resin （EVA）. The performance of the resultant EVA composites was characterized. When 19 wt% PPAP/CFA （IFR） was introduced with a mass ratio of 3：1， the EVA composites obtain a UL 94 V⁃0 classification in the vertical burning tests as well as a limiting oxygen index （LOI） of 26.9 %. IFR was mixed with MOF⁃74 at a mass ratio of 97：3， and then the resultant mixture was introduced into EVA， the resulting composites achieved a UL 94 V⁃0 classification along with an LOI of 27.1 % at a IFR/MOF⁃74 loading of 18 %. The cone calorimetry test results indicated that the addition of MOF⁃74 effectively inhibited the release of heat， smoke and carbon monoxide during combustion. It was demonstrated that MOF⁃74 generated an excellent synergistic flame⁃retardant effect. Meanwhile， the compatibility between the flame⁃retardant additives and polymer matrix was improved. Consequently， the mechanical properties of the resultant flame⁃retardant EVA composites were well maintained.
QU Daopeng, ZHANG Tao, HUA Chenxi, SONG Xinyu, CHENG Changli, LIU Yu, WANG Zhenyu
Abstract (
179 )
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A dual⁃material 3D printing technique is developed to rationally construct nano⁃silica/carbon black/epoxy （SiO2/CB/EP） composites through alternately arranging nano⁃silica/epoxy （SiO2/EP） composites with high strength and carbon black/epoxy （CB/EP） composites with high conductivity. According to the rheological properties， the epoxy composites with 11.6 wt.% SiO2 and 10 wt.% CB exhibits excellent printability. A stable diameter of 400 μm was achieved through controlling the extrusion pressure and printing speed. The SiO2/CB/EP composites show an excellent manufacturing accuracy and a highly ordered 3D structure as verified by the optical and micro⁃CT images. The tensile， compressive and bending strengths of the SiO2/CB/EP composites were 35 MPa， 64 MPa and 120 MPa， respectively， indicating that there is no attenuation compared to those of the SiO2/EP composites. Moreover， the electromagnetic interference shielding effectiveness of the composites is as high as 25 dB on the basis of the microwave absorbing mechanism.
SONG Long, ZHONG Wen
Abstract (
167 )
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Aiming at the problems in the high surface adhesion of ultrahigh⁃molecular⁃weight polyethylene （PE⁃UHMW） with viscous materials as well as its poor cleaning performance， the surface of PE⁃UHMW was modified with microstructure by using a laser marking machine， and then its hydrophobicity was characterized by using a contact angle tester. The results indicated that the surface modification increased the hydrophobicity of PE⁃UHMW by 50 %， resulting in its anti⁃adhesion performance with a self⁃cleaning ability. The hydrophobicity of PE⁃UHMW was investigated through forming different types of microstructures on the modified surface， and the results showed that the bionic hogweed texture⁃modified surface had the best hydrophobicity. Based on this rule， the optimal processing parameters of the microstructural hydrophobicity could be achieved by an optimized combination of processing parameters for the hydrophobicity of the hogweed bionic microstructure. This combination was determined to be a fabric size of 400 μm， a transverse spacing of 100 μm， and a vertical spacing of 100 μm. Through varying the size of the texture， a relationship between the hydrophobicity of the texture and area ratio could be derived. The hydrophobicity increased and then decreased with an increase in the texture area ratio， and the maximum was achieved at a weaving area ratio of approximately 18.5 %.
LIU Gang, YAO Cheng, JIA Lei, CHEN Xipeng, CAI Hansheng
Abstract (
160 )
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This study mainly focused on the hot⁃stretching⁃induced oriented crystallization structure of isotactic polypropylene （iPP） granules specialized for capacitance films （i.e. electrical grade iPP）. A series of characterization tools， including differential scanning calorimetry， wide⁃angle X⁃ray diffraction， two⁃dimensional small⁃angle/wide⁃angle X⁃ray scattering， and dynamic mechanical analysis， were employed to determine the long⁃period spacing， orientation degree， crystallinity， melt point and chain relaxation behavior of iPP. The stretching deformation resulted in a highly oriented fibrillar morphology. A strain⁃induced crystallization enhancement was observed， in which both of the orientation degree and crystallinity increased continuously with an increasing in the strain. Two types of lamellae with thicker or thinner thicknesses were newly formed during the hot⁃stretching process. The thicker one can be attributed to the melt⁃recrystallization mode， while the thinner one is ascribed to the strain⁃induced crystallization mechanism. The dependence of strain on their crystallinity and melt point seemed to be weak. Moreover， the electric density difference between the amorphous and crystalline phases decreased with an increase in the strain， and meanwhile the chain relaxation temperatures related to different condensed states became close to each other.
DING Xinyi, DUN Dongxing, QIN Junxi, CHEN Yulei, HAN Yufei, ZHANG Yuxia, ZHOU Hongfu
Abstract (
121 )
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PLA was melt⁃blended with a chain extender （CEAX8840） and a nucleating agent （ST⁃NAB3） by using a torque rheometer， and the microstructure， crystallization behavior， mechanical properties， and heat resistance of the modified PLA were characterized by suing scanning electron microscope， hot⁃plate polarizing microscope， differential scanning calorimeter， thermal deformation meter， universal testing machine， and impact tester. The results indicated that the modified PLA obtained the smallest crystal size at CEAX8840 and ST⁃NAB3 contents of 6 and 1 wt%， respectively； however， its crystal density was the highest. Moreover， the crystallization temperature and crystallinity degree of the modified PLA were increased to 123.9 ℃ and 44.9 %， respectively. In addition， its impact strength and thermal deformation temperature were increased to 64.7 kJ/m2 and 84.9 ℃， respectively.
Processing and Application
ZOU Xiaoyue, XU Jiahui, CHEN Zhenshu, YANG Youqiang, LU Zhanquan, JIA Yuxin, LI Cheng, YE Nanbiao, CAO Kun
Abstract (
153 )
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This paper introduced the developmental history of masks and reviewed the latest research advancements in polymer nonwoven filter materials and corresponding electret technologies. These electret techniques included corona charging， hydrocharging， and electrospinning， which were required for the addition of electret additives. The commonly used polymer nonwoven filter materials mainly included polypropylene and polylactic acid. Meanwhile， the prospect of the future trends in this field were proposed.
ZHAI Menglei, CHEN Wenguang, HUANG Ming, LEI Jinyu, ZHANG Na, LIU Chuntai, GAO Guoli
Abstract (
119 )
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In view of the limitation that the existing theoretical methods cannot reflect the influence of fiber wettability on permeability， the analytical expression of capillary pressure and the calculation formula of lateral dynamic permeability of fiber tow impregnation process were derived. The numerical simulation of the process of resin impregnated fiber tows was carried out by using a phase field method. The simulation results indicated that the numerical solution of the capillary pressure obtained by the phase field method was consistent with the analytical solution obtained from this paper. This proved the reliability of the developed method. The effects of fiber volume fraction and contact angle on the dynamic permeability were studied. The results indicated that this method could better characterize the effect of fiber wettability on the permeability and realize the dynamic prediction of the permeability at different impregnation radii. Compared to the existing permeability calculation methods， the developed method is more applicable and the calculation results are more accurate.
ZHOU Shengrong, WAN Zhou, WANG Yu, LI Guo, MA Yulu, XIE Linsheng
Abstract (
128 )
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A series of screw structures with different screw leads， outer diameters， and head numbers were established by using a modeling software. After the particle model was established and the contact parameters were set in the discrete element numerical simulation software， the conveying process of screw under different structures was simulated. The post⁃treatment module was used to analyze the force of particles in the conveying process and the mass flow rate at the outlet of the feeder， and the effect of screw structure on the feeding quality was discussed. The results indicated that the screw lead was the main factor affecting the conveying efficiency of the screw feeder. The conveying efficiency of the screw with the 20 mm lead was about 15 times as high as that with the 14mm lead； however， the discharging accuracy was reduced. The screw clearance is the main factor affecting the force of particles. The decrease of the clearance can lead to an increase in the force of particles. The average force of the screw clearance is about 1.2×10-2 N. The double⁃headed screw caused the surge of force in the particle conveying process， resulting in a peak value of about 15 N. Meanwhile， the discharge efficiency was reduced， but the discharge stability was improved.
FU Lingjie, XUE Peng, ZHOU Guofa
Abstract (
108 )
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Aiming at the functional self⁃lubricating liquid film assisted in⁃mold micro assembly molding of the micro universal spherical revolute motion pair， the key technical issue to achieve precise control of its manufacturing accuracy is to clarify the multi field collaborative coupling evolution law among the diameter manufacturing tolerance of the micro assembly interface， viscoelastic thermal fluid solid coupling impact load， the thickness of continuous phase transformation evolution zone， thermal viscoelastic plastic stress， and melt viscoelastic characteristics. The research results indicated that the diameter manufacturing tolerance of the micro assembly interface was controlled by the viscoelastic characteristics of the secondary injection molding melt. When the reference viscosity increased from 2 267 to 15 000 Pa·s， the diameter manufacturing tolerance of the micro assembly interface increased by 72.7 % from 11 to 19 μm. When the relaxation time increased from 0.05 to 0.25 s， the diameter manufacturing tolerance of the micro assembly interface decreased by 38.7 % from 31 to 19 μm. To meet the industry standard of dimensional manufacturing tolerance technical indicators ≤ 30 μm， it is not advisable to use a high elastic melt with a relaxation time ≤ 0.05 s for the functional self⁃lubricating liquid film assisted in⁃mold micro assembly molding.
SONG Shasha, SI Xingyu, ZHENG Niming, YU Ying, ZHANG Yang
Abstract (
327 )
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This review provided a comprehensive overview in four types of strain sensors， including piezoelectric， resistive， triboelectric， and capacitive strain sensors， and their sensing mechanisms were summarized. The essential methods for improving the sensitivity of hydrogel strain sensors were discussed， which involved the selection of suitable materials such as conductive nanoparticles and ionic materials and the adoption of specific structural designs such as microspheres， sawtooth⁃like patterns， and porous structures. A comprehensive integration of these factors was also involved. These strategies enable the hydrogel strain sensors to obtain a high sensitivity. Furthermore， the application of hydrogel strain sensors in the fields of smart electronics， wearable devices， and medical health were introduced. Finally， the current challenges and the prospect of future opportunities in the development and applications of hydrogel strain sensors were discussed.
HU Lingxiao, JIANG Huihui
Abstract (
140 )
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The visual pressure chamber was designed. The pressure inside chamber can be measured and controlled. The camera can record the process of defoaming through the glass. To quantitatively study the relationship between defoaming rate and pressure， it is necessary to ensure that the morphology and size of the bubbles studied are basically the same. This article explores a bonding method of PET film that can control the diameter deviation of the bubbles within ±10 % for easy experimental comparison， while also eliminating bubbles through conventional processes without irreversible effects. The experiment found that below the critical pressure， the pores hardly undergo deformation. Above the critical pressure， the rate of pore contraction exhibits a positive correlation with the pressure. Through theoretical analysis， one mathematical model has been abstracted to represent the compression behavior of pores under pressure. In Abaqus， the simulation of the defoaming process was conducted using an explicit dynamic fluid cavity model. The simulated results obtained using the fluid cavity model in Abaqus are generally consistent with the experimental observations. When the film and bubbles are subjected to pressure， the film overcomes its own strength and undergoes a brief elastic deformation， and then begins a nonlinear change. At the same time， the internal space of the bubbles begins to shrink. When PET film is subjected to pressure， the deformation starts from the middle and gradually diffuses towards both sides. The internal air pressure of the bubbles increases until a state of mechanical equilibrium is reached.
Additive
WEI Shenzhi, CHEN Juan, RAO Jie, ZHANG Yinghao, ZHOU Minjie, ZHANG Qi
Abstract (
160 )
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A phosphorus⁃nitrogen organic salt flame retardant （EP） was synthesized through a simple one⁃step reaction using etdronic acid as a phosphorus source （EA） and antiphenylenediamine （PPD） as a nitrogen source. Its structure was characterized by 1H⁃NMR and FTIR spectroscopy. The flame⁃retardant TPU was prepared by mixing TPU with EP using a melt blending method， and its thermal stability， flame retardant performance， and mechanical properties were investigated. The results indicated that the addition of EP generated little effect on the thermal stability of TPU， and its flame retardancy was significantly improved. The flame⁃retardant TPU containing 3 wt.% EP （TPU⁃3% EP） obtained a limiting oxygen index of 28.40 vol.% and also achieved a UL 94 V⁃0 classification in the vertical burn experiment. The residual carbon yield （CY） was more than twice that of pure TPU. Compared with pure TPU， the total heat release and peak heat release rate of TPU⁃3% EP were reduced by 22.12% and 61.85%， respectively， and its effective combustion heat was also reduced. EP can enhance the flame⁃retardant performance of TPU mainly by catalyzing the condensation phase to form charcoal and isolate thermal oxygen exchange. Moreover， the free radical quenching effectiveness in the gas phase also generates a certain flame⁃retardant effect.
Standard and Test
YIN Maofeng, WANG Xiaoke, SUN Guohua, ZHANG Xin, LI Pengpeng, MA Jinsong, XIAO Jun, HOU Lianlong
Abstract (
117 )
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The infrared spectra of common biodegradable plastics were first collected using attenuated total reflection infrared spectroscopy， and their characteristic functional groups were labeled. A blend of biodegradable plastic and non⁃degradable plastic was prepared through melt blending and solution blending. The results indicated that a rapid detection method based on infrared spectroscopy was efficient and accurate in the analysis of biodegradable plastics. This study provides useful references for promoting the development of biodegradable plastics and the treatment of plastic pollution.
Machinery and Mould
HUANG Shizheng, PAN Wei, ZHU Jiawei, MOHINI Sain, YANG Weimin, ZENG Xiankui, JIAN Ranran
Abstract (
127 )
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Based on the principle of polymer field⁃synergistic plasticization， transportation and mixing， a field synergistic elongation element with a new structure of field⁃synergistic elongation screw was designed and developed for enhancing mixing and heat transfer. The ANSYS Polyflow was employed to numerically simulate ordinary double head threaded screws and field synergistic elongation screws with different elongation element arrangements. The effects of screw configuration on the mixing performance， heat transfer performance， and plasticization uniformity of polymeric rubber were comparatively analyzed. The results indicated that the comprehensive performance of the field synergy elongation element was superior to that of the ordinary threaded screw. Among these screws， the heat transfer performance of screw B with concentrated arrangement of field synergy elongation element was the best， and the mixing performance of screw F with the dispersed arrangement of field synergy elongation element was the best. The radial convergence channel of the elongation element in the field synergy elongation element changed the direction of the velocity field， generating radial components in the velocity vector. This promoted the synergistic interaction between the velocity field and the temperature gradient and velocity gradient fields， increasing the stretching flow and deformation in the flow field and strengthening the heat and mass transfer and transportation process.
ZHUANG Yule, ZHAO Liping, QIN Ruiliang, JIANG Shangtian, SUN Guangdong, LIANG Shitian
Abstract (
173 )
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To address the problem in the existence of gate marks on the surface of a shredder shell plastic part， a hot runner mold with a complex inverted structure and a rear mold feeding mode was designed. The ejection action was completed through designing mechanical hooks. Considering the structural characteristics of the plastic parts with multiple inverted buckles surround them and internal bone positions， a four⁃sided slider splicing and core⁃pulling mechanism was designed for demolding on the lateral side of the rear mold. The back mold core was designed with multiple insert structures， which facilitated the processing， prevented the air trapping， improved the molding efficiency and quality. During the mass production， the various mechanisms of the mold operated smoothly， and the quality of the plastic parts was excellent， which could meet the requirements of design.
Review
WEN Qilin, JIA Xuehua, SUN Yanjun, NIU Siji, CHEN Yinghong, CHEN Ning
Abstract (
229 )
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The paper introduced the basic properties of several typical commercially available biodegradable thermoplastics， including polylactic acid， poly（butylene adipate⁃co⁃terephthalate）， polypropylene carbonate， and polybutylene succinate and reviewed the research progress in their modification. Several forming technologies for preparing biodegradable plastic packaging films were introduced in detail， including blowing film， casting， calendering， and biaxial stretching methods. The recent application status of biodegradable plastic films as green packaging materials was described.
LI Ruichao, ZHU Guangming, ZHANG Xuebei, GUO Xinyi
Abstract (
141 )
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This paper reviewed the latest research advancements in the catalytic activity and mechanisms of several cyanate ester⁃curing systems catalyzed by active hydrogen catalysts， transition metal complexes， ultraviolet light activated catalysts， organic tin catalysts， and ionic liquids. The prospect for the future trend in the low⁃temperature curing catalytic systems of cyanate esters were also proposed.
CUI Bao, YANG Jianjun, WU Qingyun, WU Mingyuan, ZHANG Jianan, LIU Jiuyi
Abstract (
294 )
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This paper reviewed the blending modification of polylactic acid （PLA） from the aspects of degradable materials， nanomaterials and polyurethane， and its applications were summarized. Finally， the future development prospect in modification of PLA was proposed.
XIAO Jinnan, ZHANG Zhenming
Abstract (
174 )
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This study systematically reviews the source characteristics， occurrence characteristics， pollution hazards， and potential risks of microplastics in agricultural soils in China. Furthermore， the key issues and future research directions of the microplastic pollution in farmland soil were discussed. It is expected to provide scientific ideas for systematic analysis and exploration of the microplastic pollution mechanisms and the prevention and control of risks in farmland soils.
Special discussion
SHI Xunruo
Abstract (
148 )
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This paper reviews the history， production and sales data of foreign poly（vinyl chloride）， the current situation of domestic poly（vinyl chloride） plastics， the current situation and requirements of domestic building energy consumption， the contribution of plastic building materials to carbon peaking and carbon neutrality， and the prospect of plastic building materials.
