Materials and Properties
REN Guozhen, WANG Mengmeng, HUANG Jianjian, JIN Gang
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251 )
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Poly（ether ether ketone） （PEEK） has excellent performance and has been widely used in the high⁃end equipment field； however， the processing window of the PEEK melt is narrow and its processability is poor. Thermotropic liquid crystal polymer （TLCP） is a liquid crystal polymer with excellent dimensional stability， good processing fluidity， and a unique in⁃situ fiber self⁃reinforcing effect. In this study， PEEK/TLCP blends with different contents of TLCP were prepared by mean of an eccentric rotor extrusion mechanism dominated by a volume tensile flow field. The rheological properties， micromorphology， thermal properties and crystallization properties of PEEK/TLCP blends were studied under a tensile flow field. The results indicated that the addition of TLCP effectively broadened the processing range of PEEK under the tensile flow field. This resulted in a decrease in the viscosity of the system by 14.43 % at a low shear rate and by 80.68 % at a high shear rate. Owing to the action of tensile flow field， TLCP formed a fiber structure along the extrusion direction in the PEEK matrix over a wide range of content， and it also could promote the crystallization of the PEEK matrix at a low content. The blend containing 10 wt% TLCP obtained maximum tensile strength of 86.60 MPa， which was 4.6 % higher than that of the PEEK matrix.
WANG Wenhui, ZHU Huihao, LI Guo, WANG Yu, WU Fan, LIN Zhenbin, MA Yulu, XIE Linsheng
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232 )
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In this paper， PP/PC blends were prepared by using a laboratory⁃made internal mixer， and their microstructure， rheological properties， mechanical properties， and optical properties were characterized by topography analysis， rheological test， tensile test， notch impact strength test， and optical test. The UV shielding effect of UV⁃P filled PP/PC compounds was studied. The results indicated that there was a threshold of dispersed phase content in the coupling performance of light transmittance and haze. There was a threshold for the addition amount of UV⁃P according to the UV shielding effect. The tensile and impact strength of the as⁃prepared blends reached 30.40 MPa and 44.85 J/m， respective， at a PC content of 3 wt%. When 0.1 phr UV⁃P was incorporated， the blends presented an average transmittivity of 1.04 % in the UV region， a transmittance of 83.39 %， and a haze of 93.65 %. The blends developed in this work exhibited a good scattering effect and strong absorption of ultraviolet light.
LI Hongbo, YANG Rui, SU Zhengtao
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260 )
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Five types of polytetrafluoroethylene （PTFE）⁃based composites with carbon fiber （CF）， wollastonite fiber （WF）， polyimide （PI）， polyoxybenzoyl （POB） and copper powder （Cu） at a volume fraction of 25 vol% were prepared. The effects of different fillers on the mechanical properties， creep properties， thermal conductivity and tribological performance of the composites were comparatively investigated. The micro⁃morphology of the worn surface of the composites was analyzed， and their wear⁃resistant mechanism was discussed. The results indicated that the hardness and compressive strength of PTFE were significantly enhanced by the five types of rigid fillers， its creep was reduced， and its thermal conductance was improved. However， the tensile strength and elongation at break of PTFE were greatly reduced. The CF⁃modified PTFE composite exhibited the highest tensile and compressive strength and the best creep resistance. Meanwhile， the Cu⁃modified PTFE composite presented the highest hardness and the best thermal conductance. The modified PTFE obtained a considerably improvement in wear resistance due to the enrichment of the rigid fillers at the wear scar interface. The three types of inorganic fillers increased the friction coefficient of PTFE， whereas the two types of polymer fillers， PI and POB， reduced its friction coefficient slightly. The POB⁃modified PTFE composite presented the best tribological performance with a friction coefficient of only 0.19 and a volume wear rate of around 4.21×10-6 mm3/（N·m）. Its wear resistance was 260 times higher than that of pure PTFE.
ZHAO Mengmeng, YANG Hongjuan, SHEN Siyu, FENG Shuo, ZHANG Weimeng, HU Jing
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274 )
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Poly（lactic acid） （PLA） and poly（adipic acid⁃butylene terephthalate） （PBAT） were melt blended by using a torque rheometer with poly（ethylene glycol diglycidyl ether） （PEGDGE） as a compatibilizer. The effect of PEDGDE content on the properties of PLA/PBAT blends such as cross⁃sectional microscopic morphology， thermal properties， and mechanical strength was investigated using Fourier⁃transform infrared spectroscopy， scanning electron microscopy， and differential scanning calorimetry， etc. The results indicated that compared to the blending system without a compatibilizer， the PLA/PBAT/PEDGDE blends achieved an increase in elongation at break from 14.6 % to 38.9 %. Such a result was 2.7 times higher than that of PLA/PBAT. Due to the presence of PEGDGE， the PLA/PBAT blending system showed a shift of cold crystallization peak towards a low temperature， and its crystallinity increased significantly when 5 parts of PEGDGE were added.
ZHOU Long, DU Guoyong, DENG Chunping
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273 )
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A simple， efficient， and environmentally friendly method was adopted for oil⁃water separation. In this method， graphene oxide （GO） was first prepared by means of a modified Hummers method， and then a superhydrophilic⁃underwater superoleophobic sponge was prepared through two⁃step impregnation using polyurethane sponge （PU） as a matrix and GO and chitosan （CS） as modifiers. The addition of GO increased the roughness and hydrophilicity of the sponge surface， while the incorporation of CS enhanced the hydrophilicity of the sponge and the stability of the GO coating. The modified PU sponge exhibited good elasticity， thermal stability and water absorption. The oil⁃water separation experimental results indicated that a variety of oil⁃water mixtures could be separated only under the action of gravity， and their separation efficiency could reach more than 95 %. The modified PU sponge presented good reusability without a significantly reduction in the separation efficiency after reusing for 10 times. When the pump provided a dynamic external force， the static and dynamic continuous oil⁃water separation could be realized without stirring and with stirring， respectively. The high oil⁃water separation performance could be maintained for the modified PU sponge after wearing for 10 cycles.
DU Le, HU Yajie, HU Jian, SUN Tao, YUN Xueyan, DONG Tungalag
Abstract (
137 )
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A low molecular⁃weight poly（L⁃lactic acid） （PLLA） and poly（icconic acid⁃co⁃butanediol） （PBI） were first synthesized， and the resulting two copolymers were mixed to obtain high molecular weight poly （L⁃lactic acid co⁃icconic acid⁃co⁃butanediol） （PLBI） through a polycondensation reaction. Then， chitosan （Cs） was grafted with glycidyl methacrylate （GMA） to obtain a GMA⁃grafted chitosan copolymer （Cs⁃g⁃GMA） with double bond groups. Finally， the resulting Cs⁃g⁃GMA and PLBI films were laminated through UV curing to obtain a PLBI/Cs⁃g⁃GMA bacteriostatic film with covalent bonds at the interface. NMR analysis indicated that PLBI and Cs⁃g⁃GMA copolymers were successfully prepared. The infrared spectroscopic analysis of the PLBI/Cs⁃g⁃GMA film demonstrated that Cs⁃g⁃GMAwas successfully grated into the PLBI film. Mechanical test results indicated that the mechanical properties of PLBI film were significantly improved， and its elongation at break reached 214.3 %. Hydrophilic test results indicated that the hydrophilicity of the PLBI/Cs⁃g⁃GMA film was enhanced together with good cytocompatibility. The PLBI/Cs⁃g⁃GMA film exhibited a good antibacterial effect on escherichia coli with an antibacterial rate as high as 83.4 %.
YANG Xiying, CHEN Meng, ZHANG Wencai, PEI Qiang
Abstract (
156 )
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To determine the thermal stability of styrene⁃butadiene⁃styrene block copolymer （SBS）/nano⁃calcium carbonate composite⁃modified asphalt， the stability mechanism and qualitative judgment method were studied by using infrared spectroscopy， fluorescence microscopy， and material surface interface chemistry theory. Through using a softening point correlation method and an infrared spectroscopy technology correlation method， the regression models of softening point， SBS characteristic peak area， and modifier content were fitted， and a data model for softening point and SBS characteristic peak area was established. The results indicated that nano⁃calcium carbonate improved the thermal stability of SBS⁃modified asphalt through a physical action. The stability of the system was good a softening point difference ≤ 2.5 ℃， a SBS content difference ≤ 0.34 %， and a CaCO3 content difference ≤ 0.15 %. The infrared spectral correlation method revealed the internal factors of the system stability. The system was stable when the difference of characteristic peak area at 966 cm-1 was less than 0.24 and the softening point difference was less than 2.5 °C. The regression results indicated that the data model of softening point and SBS characteristic peak area established by this study was statistically significant， which could construct a new evaluation system for the study of the thermal stability of SBS/nanomaterials composite⁃modified asphalt.
Processing and Application
DENG Xiaozhen, LIU Biao, XIAO Bing, JIANG Shiyu, CHEN Tianrong
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136 )
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The gas⁃assisted technology was applied for the polymer extrusion molding of a hollow double⁃layer microtubule， and the finite element method was used to analyze and study the microtubule co⁃extrusion molding process. Four different co⁃extrusion numerical models were established， which included the traditional microtube co⁃extrusion， gas⁃assisted microtube co⁃extrusion， single inner wall gas⁃assisted microtube co⁃extrusion， and single outer wall gas⁃assisted microtube co⁃extrusion. The differences in die swell rate， velocity distribution， pressure distribution， and shear rate distribution were studied. The results indicated that the double⁃side gas⁃assisted technology effectively improved the extrusion swell， uneven velocity distribution， uneven shear rate distribution， excessive pressure drop， and other problems during the hollow double⁃layer microtube extrusion process. However， the gas⁃assisted micro co⁃extrusion with a single inner wall cannot resolve the problems caused by the traditional micro co⁃extrusion， and its extrusion expansion rate was 105.41 %. The gas⁃assisted micro co⁃extrusion with a single outer wall can lead to extrusion shrinkage， and there is no improvement effect on the shear rate distribution and pressure drop.
WANG Haolin, WANG Tingxi
Abstract (
119 )
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The solids conveying section of a single⁃aligned three⁃screw extruder under metering and dosing was simulated using a discrete unit method. The transport performance of polymer particles was analyzed through both positive displacement conveying and friction drag conveying in a one⁃screw extruder. The conveying characteristics parameters of the mono⁃aligned three⁃screw extruder were calculated and then compared with those of a conventional twin⁃screw extruder. The results indicated that the filling rate of the particles in the screw groove of the extruder was increased with an increase in the engagement zone of the three⁃screw extruder. The mono⁃aligned triple⁃screw extruder exhibited better performance of the twin⁃screw extruder in the aspects of the filling degree and mass flow rate， and its conveying output was approximately 1.3 times that of the twin⁃screw extruder. This indicates a promising prospect of engineering application in the polymer processing industry.
LI Hongwei, ZHANG Yongfeng, QI Wujun, RUAN Gangyong, RUAN Libo, FANG Yuchao
Abstract (
203 )
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In this study， the product standards of polyethylene pipes and reinforced polyethylene composite pipes in our country were analyzed and compared， the applicable ranges of pipe diameter， pressure， temperature and media under different implementation standards were enumerated. The advantages of polyethylene pipes and reinforced polyethylene composite pipes in the practical engineering application were introduced. The actual problems in the engineering practice were summarized into the following three aspects： （1） the problems caused by the performance of the material itself； （2） the problems caused by the implementation of product standards； （3） the problems resulting from the design and construction standards.
GAO Hailiang, HU Cheng, ZHOU Yuqiang, LIU Xin, CHENG Jianming, SONG Guizhen
Abstract (
168 )
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In the forming process of large⁃sized parts， the precision loss caused by the warping deformation at the bottom of the part is a prominent problem in the melt deposition additive manufacturing technology. Taking the bottom warping deformation of melt deposition molding （FDM） 3D printed parts as a research object， an orthogonal experiment was designed to study the effects of nozzle temperature， layer thickness， bracket temperature， filling density， the number of layers， and section length on the warping deformation of FDM 3D printing. The optimal combination of process parameters was obtained through range analysis and variance analysis. The results indicated that the warpage deformation obtained a minimum value of 0.402 mm at a layer height of 0.2 mm， a nozzle temperature of 210 ℃， a bracket temperature of 55 ℃， a filling rate of 40 %， a number of bottom layers of 25， and a section length of 20 mm. The factors of influence on the warpage deformation was by a order of layer thickness > number of layers > nozzle temperature > section length > filling density > bracket temperature. The warping deformation decreased with an increase in the number of layers but a decrease in the section length.
Additive
ZHOU Yingxin, WENG Yunxuan, LYU Yihui
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169 )
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The migration of phthalate esters from cling films and their migration behavior to simulants were analyzed using the test method in accordance with GB 31604.30—2016. The effects of temperature， time， and food simulants on the migration behavior of phthalate esters were investigated. The results indicated that for all three commercially available food⁃grade poly（vinyl chloride） （PVC） cling films， the migration of di（2⁃ethylhexyl） phthalate （DEHP） was detected. For the same food simulant， the migration of DEHP in PVC cling films increased with an increase in temperature and time at different experimental temperatures and times. For different food simulants， the migration of DEHP in PVC cling films in oil simulants and high alcohol simulants was greater than that in aqueous and acid simulants at the same temperature and time.
Standard and Test
ZHANG Panpan, LIU Jing, JIANG Jianzhun, CAO Xuejun
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113 )
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In this study， five nucleating agents with different properties in polypropylene （PP） were analyzed by using ultra high performance liquid chromatography （UPLC）. The factors affecting the extraction efficiency of sample pretreatment were studied， and the effects of heating extraction， ultrasonic extraction， and microwave⁃assisted extraction （MAE） were investigated. The results indicated that MAE generated a good extraction effect on PP with different properties. In this extraction method， the ACQUITY BEH C18 （50 mm×2.1 mm，1.7 μm） column was used for separation， acetonitrile and water were used as mobile phases， and the UV detection wavelength was set to be 213 nm. The correlation coefficient of external standard curve was >0.995， indicating a good linear relationship between 5 and 300 mg/L. This method presented a recovery ranging from 83.4 % to 113.1 % along with a relative standard deviation （n=9） varying from 0.9 % to 7.9 %. The method developed in this study is suitable for the reliable detection of nucleating agents in PP.
Plastic and Environment
DONG Dangfeng
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163 )
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In this study， an asphalt modifier （SPM） was prepared through a twin⁃screw extrusion granulation technology using recycled polyethylene/recycled polypropylene/recycled sulfur slag materials as raw materials at a mass ratio of 6/4/0.7. The effect of SPM content on the penetration， ductility， softening point， viscosity， low temperature crack resistance and rheology of modified AH⁃70 asphalt was investigated. The modification effectiveness was verified by the infrared spectrum and microtopography. The results indicated that the introduction of SPM improved the high temperature performance of the modified asphalt significantly， and a certain content of SPM could generate a positive effect on the low⁃temperature performance of the modified asphalt. This work can provide a theoretical basis for the application of SPM modifier in traffic construction.
Machinery and Mould
YE Weiwen, ZHANG Xiaojuan, ZHAO Liping, HOU Xianzhou
Abstract (
187 )
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Based on the analysis of the structural characteristics of a plastic part in an automobile elbow joint and its appearance and performance requirements， a complex injection mold was designed， including a core⁃pulling mechanism comprising a fixed mold and a moving mold， a fixed distance priority mold opening mechanism， a mold opening and closing sequence protection device， and a forced mold closing mechanism. Through using a fixed mold inclined slider core⁃pulling mechanism， the problem in lateral undercutting of the plastic part was successfully solved. Aiming at the problems of possible grain peeling and impact on the surface of the plastic flanging structure， a method for side parting and oblique core pulling was adopted to solve these problems. The fixed distance priority mold opening mechanism provided an effective guarantee for the core pulling sequence. The design of a forced mold closing mechanism could avoid collision between the fixed mold slider and moving mold slider during mold closing. The combination of the two sliders with the mold opening and closing sequence protection device ensured the safety and stability of mold production.
DING Hai, MA Bingxin, HUA Shaozhen, CAO Wei
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144 )
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In this study， the precision of central venous catheter extrusion mold was taken as a research object， and the accurate cross⁃section shape and size of die was obtained from the analysis of a reverse deformation technology with the aid of the Polyflow software. A three⁃factor and two⁃level orthogonal experiment simulation were carried out by using the parameters of compression angle， mold length and clearance angle， and the optimal central venous catheter die runner structure parameters were obtained from the variance analysis. The simulation results were further verified by the actual production. The results indicated that the extrusion die had a high yield and could be used as a reference for the development of related extrusion dies.
Review
ZHU Jiawei, PAN Wei, HUANG Shizheng, MOHINI Sain, YANG Weimin, JIAN Ranran
Abstract (
242 )
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Fused deposition modeling （FDM） technology has become a mainstream technology in the 3D printing field due to its low cost， easy operation， rapid prototyping， and wide applicability. Despite its important position in the 3D printing field， there are still some limitations of FDM technology， such as insufficient strength of printed parts and slow molding speed. These have become the important challenges limiting the further development of this technology. To address these issues， this paper discussed the efforts of domestic and foreign researchers in improving printing strength from two aspects， i.e.， optimizing interface bonding methods and enhancing material properties. Meanwhile， the limitations and improvement measures for increasing the printing speed of FDM equipments were discussed from the perspectives of optimizing equipment modules and printing strategies （such as injection printing）. Finally， some suggestions and opinions were proposed for the enhancement of printing strength and speed.
WANG Lei, ZHAO Min, WENG Yunxuan, ZHANG Caili
Abstract (
152 )
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In this paper， the applications of machine learning （ML） in the poly（lactic acid） （PLA） processing as well as its performance prediction was reviewed. The current applications of ML in predicting the crystallization properties， fatigue life， tensile strength， toughness， yield stress， density， and degradation degree of PLA were summarized. As discussed in the paper， ML could be used to monitor the possible defects in the PLA processing， thus reducing the production cost and improving the service life of PLA products. Finally， the future role and development of ML in the PLA processing and applications were prospected.
