Materials and Properties
LI Wanlong, YANG Weimin, WANG Shuo, LI Changjin, ZHANG Yang, TAN Jing, YAN Hua, LI Haoyi
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167 )
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In this study， an organic⁃inorganic compounded nucleating agent （CH⁃S04） was used to enhance the mechanical properties of poly（lactic acid） （PLA） microfibers. The non⁃isothermal crystallization behavior of the resultant PLA/CH⁃S04 fiber films as well as the action mechanism of CH⁃S04 in the multistage drafting process were studied under different spinning temperatures and voltages， and their mechanical properties of PLA/CH⁃S04 fiber films were characterized. The results indicated that when the spinning temperature was 220 ℃ and the spinning voltage was 50 kV， the degrees of crystallinity of PLA/CH⁃S04 fiber films reached maximum values of 27.12 % at a spinning temperature of 220 ℃ and 32.32 % at a spinning voltage of 50 kV， which were 18.53 % and 23.73 % higher than that of pure PLA fiber film， respectively. In different spinning receiving forms， CH⁃S04 achieved the best crystallization enhancing effect on PLA when applying voltage and air flow together with collecting by a roller. The resulting PLA/CH⁃S04 fiber film obtained a degree of crystallinity of 36.66 %， which was 28.07 % higher than that of pure PLA fiber film. The PLA/CH⁃S04 fiber film obtained tensile strength 12.33 MPa at a spinning temperature of 240 ℃ and a spinning voltage of 50 kV， which was 11.58 % higher than that of pure PLA fiber film.
XU Wei, LYU Mingfu, DU Wenjie, GUO Peng, XU Yaohui
Abstract (
91 )
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The polypropylene （PP） with a broad molecular weight distribution was used as a matrix for preparing long⁃branched chain PP due to its excellent mechanical properties and processability. The twin⁃screw reactive extrusion was carried out to prepare the long branched⁃chain PP， enhancing the production efficiency. Additionally， melt radical grafting was conducted at two different temperature. The effect of long chain⁃branched structure on the properties of PP was investigated by using gel permeation chromatography， Fourier⁃transform infrared spectroscopy， and rheometry to determine the molecular weight and distribution， grafting degree， and tensile rheological behavior of the of the as⁃prepared PP. The mechanical test results indicated that the mechanical properties of the as⁃prepared PP decreased with an increase in the reaction temperature； however， its mechanical strength increased slightly with an increase in the content of long branched chains. The thermal analysis demonstrated that there was a significant increase in the crystallization temperature of PP but a decrease in its degree of crystallinity with an increase in the content of long branched chains. The crystallization temperature was increased by 11 ℃ at a processing temperature of 200 ℃ and a monomer content of 4 wt% compared to pure PP.
LI Guolin
Abstract (
81 )
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A type of damping masterbatch was prepared through blending and extrusion using homopolymer polypropylene and nitrile rubber powders as raw materials， and the effect of masterbatch content on the mechanical， damping， and thermal properties of modified high⁃impact polystyrene （HIPS） were investigated. The result indicated that， when the content of the masterbatch was 30 wt%， the notch impact strength of the modified HIPS decreased from 9.1 kJ/m2 to 3.5 kJ/m2， and its tensile strength decreased from 34.1 MPa to 21.3 MPa，its loss factor at 20 ℃ increased from 0.015 to 0.26， and its loss factor at 60 ℃ increased from 0.023 to 0.034. Thermogravimetric analysis results indicated that the heat resistance of the modified HIPS increased with an increase in the content of the damping masterbatch.
YU Tianliang, CHEN Wenge, CHEN Shirun, CHEN Da, ZHOU Wei, ZHOU Lanyan
Abstract (
82 )
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In this study， polyethylene （PE）/modified graphene composites were prepared through mechanical ball milling and hot melt extrusion， and the effect of modified graphene on the microstructure and properties of the composites were investigated. The results indicated that graphene can be uniformly dispersed in the PE matrix through modification with rare earth. The as⁃prepared PE/0.5 wt%CeO2@rGO composite exhibited a degree of crystallinity of 62.14 %， its tensile strength increased by 8.6 %， its elastic modulus increased by 5.79 %， and its impact toughness increased up to 4.35 kJ/m2. A change in the fracture mode took place from a sole ductile fracture to the brittle⁃ductile combined one. Meanwhile， the addition of modified graphene resulted in an increase in the thermal decomposition temperature by 20 ℃.
ZHANG Xiaoguang, WEI Tianqi, CUI Zhe, MAO Mingzhen, LI Hansheng, WANG Bozhou, WU Qin
Abstract (
71 )
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Polyphosphazene/carbon nanotubes （SWNTs） composites were prepared by using a solution⁃blending method. SWNTs were randomly distributed on the polyphosphazene matrix to form a conductive phase. The structure and properties of the as⁃prepared composites were characterized by using Fourier⁃transform infrared spectrometer， scanning electron microscope， thermogravimetric analyzer， electrical conductivity tester， and vector network analyzer. The results indicated that the electromagnetic shielding effectiveness and electrical conductivity of polyphosphazene/carbon nanotubes composites were related to the loading of carbon nanotubes in the matrix. The electromagnetic shielding effectiveness of the composites reached 60.9 dB at a SWNTs content of 15 wt%， its average electrical conductivity reached 0.989 4 S/cm， and its residual char yield was 35.66 wt% at 700 ℃.
ZHANG Hui, TANG Zhanzhan, BAO Haixia, CHENG Xinyuan, CHEN Bin
Abstract (
89 )
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The mechanical properties of unplasticized poly（vinyl chloride） （UPVC） pipe under high and low temperature environment were experimentally studied， and the constitutive models of UPVC pipe under different temperature were established. The relation between mechanical parameter and ambient temperature was proposed. A stress⁃strain curve model was established considering the influence of ambient temperature， and the proposed constitutive model was verified. The results indicated that the ambient temperature of UPVC pipe material has a great influence on the mechanical properties. Compared with the properties at normal temperature， the brittleness and yield strength of the material increased at low temperature， while the ductility and fracture strain decreased. At high temperature， the yield strength and fracture strain of the material decreased， while the ductility increased. Numerical analysis was carried out by using the programmed subroutine in terms of the ambient temperature variables. The numerical analysis results were in good agreement with the test ones.
Processing and Application
ZHANG Zheng, LI Fangquan, ZHU Guixiang, GUO Min, WANG Ying
Abstract (
66 )
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The spinnability of poly（butylene succinate terephthalate） （PBST） in a mono⁃solvent system of dichloromethane （DCM） or in a binary solvent system of chloromethane/N，N⁃dimethylformamide （DMF） was intensively investigated by using a solution electrospinning technique. The effects of polymer spinning solution concentration， feeding rate， and solvent ratio on the diameter of PBST nanofibers during the electrospinning process were also investigated. The diameter of the PBST nanofibers was further evaluated by the addition of a tetrabutylammonium chloride （TBAC） organic salt during the electrospinning process. The assistance effects of TBAC on different concentrations or solvent systems were also studied. The results indicated that the addition of TBAC could greatly elevate the conductivity of the polymer solution， improving its spinnability and consequently reducing the fiber diameter. Meanwhile， the filtration properties of the as⁃prepared PBST nanofibrous materials were also preliminarily explored. The PBST nanofibrous materials with a minimum fiber diameter of 65 nm were prepared by using a 5⁃wt% PBST/（DCM/DMF=7/3） polymeric solution， in which the mass ratio of PBST to TBAC was 4/1. The PBST nanofibrous materials obtained an optimal filtration efficiency of 99.98 % and a filtration resistance of 237 Pa when using an 8⁃wt% PBST/（DCM/DMF=7/3） polymeric solution， in which the mass ratio of PBST to TBAC was 16/1.
WANG Chen, HE Qi, LI Jingyao
Abstract (
70 )
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In this paper， a connecting pipe between evaporator and compressor in a certain type of automobile air conditioning system was selected as a design object， and the SolidWorks software was used to design the air conditioning connecting pipe copying shape checker. The structural characteristics of the copying shape checker were optimized for slicing， and the variable layer height slicing scheme of base plate （0.1 mm layer height）+pedestal （0.3 mm layer height） was adopted. The experimental results indicated that the 0.1 mm+0.3 mm variable layer height slicing scheme had a higher forming accuracy than the 0.1⁃， 0.2⁃ and 0.3⁃mm⁃fixed layer height slicing schemes. Compared to the 0.1⁃， 0.2⁃mm⁃fixed layer height slicing solutions， 0.1 mm+0.3 mm variable layer height slicing solution has less weight for the checker and higher printing efficiency. The 0.1 mm+0.3 mm variable layer height slicing solution was selected as an optimal solution， and the manufacturing practice of air conditioner connecting pipe copying shape checker was carried out using poly（lactic acid） filament as a raw material on an industrial grade fused deposition modeling 3D printer. The checker exhibited the characteristics of high precision， low cost， high efficiency， and light weight.
WEN Yuan, GUO Deyu
Abstract (
63 )
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In this study， a heat transfer model was established for an electric heating rolling machine， and a law of energy conservation per unit time was used to establish and solve analytical solutions for the air temperature inside the furnace， mold temperature， material temperature， and mold air temperature. This analytical solution is a specific set of solutions for a sixth order homogeneous constant coefficient differential equation in the heating section， and a specific set of solutions for a third order homogeneous constant coefficient differential equation in the cooling section. These solutions could be easily obtained through matrix calculation. The analytical solution was validated through experiments， and the results indicated a high degree of agreement between the calculated and measured values. The calculation accuracy of the air temperature inside the mold was 97.51 %， and the calculation accuracy of the air temperature inside the furnace was 98.02 %. The simulation calculation results of material temperature do not support the existing powder deposition theory. The use of in⁃mold temperature curves as a quality control method in engineering has some limitations.
MA Wenxian, CHANG Hongxiang, XU Feng, XU Yong
Abstract (
67 )
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In this paper， the effects of stretch behavior on the micropore structure， strength and thermal shrinkage of lithium battery separator were investigated. The design of experiment verification and effect analysis indicated that the stretch temperature had the strongest positive effect on the porosity of separator， followed by its stretch rate. The effect weakened at stretch rates between 8.5 and 10 times. Meanwhile， the stretch rate and stretch temperature had a strong interaction effect. In addition， the correlation coefficient between the stretch factor and regression model established by the pore size was 98.6 %. The negative effect of stretch temperature on the strength of the diaphragm was the strongest， followed by the positive effect of stretch magnification. When the stretch rate of the separator was 8.5~10 times， its efficacy was weakened. The separator obtained the best strength response value at a stretch rate of 37.5 %/s. In addition， the effects of pore formation and strength were explained through topography analysis. The negative effect of stretch temperature on the thermal shrinkage of the diaphragm was the strongest， followed by the positive effect of the stretch rate. The hedging of the effect weakened at a stretch rate of 7~8.5 times， and the stretch temperature and stretch rate had a strong interaction. The regression coefficient between separator crystallinity and thermal shrinkage was 81.1 %. The larger the separator crystallinity， the smaller was the thermal shrinkage.
XU Lu, LIU Jian, WANG Zhenchao, ZHANG Shijun, QIE Jichun, YOU Qijiang, CAI zhihui
Abstract (
59 )
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In this paper， the effects of ambient temperature and input energy on the mechanical properties of electrofusion joint used in the connection of small⁃caliber high⁃density polyethylene （PE⁃HD） gas pipes and pipe fittings were studied. Seven sets of parameters were applied for experiments， and the voltage， current， and welding interfacial temperature of the pipes and pipe fittings were collected during the welding process. The interfacial temperature increased gradually with an increase in the ambient temperature， and meanwhile the percentage of weld peeling decreases gradually. With an increase in the input voltage， the input energy increased， but the percentage of weld peeling decreased gradually. Furthermore， the higher input energy resulted in a phenomenon of over⁃welding. The failure in the removal of the skin layer of the pipe affected the welding quality. The intelligent electrofusion welding machine and data management software were recommended for use to monitor the energy input throughout the process， adjust the input energy in real time， and intelligently identify the quality of the weld.
Additive
ZHANG Xinyue, YANG Mingzhao, LI Congcong, SU Baoshan, LI Huanhuan, GAO Baoshan, SHU Zuju
Abstract (
64 )
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In this study， the fatty acid isobutylene ester （MO） was prepared by using soybean oil and isobutylene as raw materials， and then a highly active soybean oil⁃based reactive diluent （EMO） was synthesized through an epoxidation reaction using m⁃chloroperoxybenzoic acid as an oxidant. Then， the resultant EMO was added to epoxy resin to prepare compounding materials. The effects of transesterification reaction time， alcohol⁃oil ratio， catalyst ratio and reaction temperature on the conversion rate of MO and the effects of EMO and epoxy resin mixing ratio on the flexural properties of the as⁃prepared compounding materials were investigated. The results indicated that the conversion rate of MO reached 96.56 % at an optimal reaction time of 20 min for the transesterification reaction， a mass ratio of alcohol to oil of 7/1， a catalyst concentration of 0.6 wt%， and a reaction temperature of 70 ℃. The flexural strength of epoxy compounding materials increased at first and then tended to decrease with an increase in the EMO content. The epoxy compounding materials exhibited the highest flexural strength of 103.90 MPa at an EMO content of 10 wt%. Their flexural modulus decreased with an increase in the EMO content， but their toughness tended to increase.
LIU Sheng, WANG Qian, LIU Shun, LIU Haitang
Abstract (
74 )
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In this study， lignin was extracted from papermaking black liquor and then used as a new green lignin⁃based nucleating agent for the modification of poly（ethylene terephthalate） （PET）. This obtained lignin was compared with traditional sodium benzoate and talc nucleating agents， and its microstructure， crystallization and mechanical properties were characterized. The results indicated that the crystallization properties of the regenerated PET materials were improved by adding different nucleating agents. Among these nucleating agents， the lignin⁃modified regenerated PET obtained the most significant improvement in the degree of crystallinity up to 32.65 %， which was increased by 12.11 % compared to that of the pristine regenerated PET. The semi⁃crystallization time of the modified regenerated PET was reduced by 60 %. The recycled PET also obtained a significant improvement in the mechanical properties after modification， followed by an increase in the elongation at break. In particular， the lignin⁃modified regenerated PET showed enhanced tensile strength of 42.95 MPa， which increased by 104 % compared to that of the pristine regenerated PET， followed by an increase in the elongation at break by 2.46 %.
YANG Xiaochun, LIU Huiyuan, ZHANG Qing, YU Jing
Abstract (
62 )
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The thermal stability of poly（vinyl chloride） （PVC） could be improved by a sodium⁃A molecular sieve according to the Congo red experiment. The static thermal stability time of the modified PVC was increased up to 72 min， which was better than that of pure PVC （7 min）. The sodium⁃A molecular sieve was compounded with β⁃diketone， pentaerythritol， phenyl diisooctyl phosphate and epoxidized soybean oil to obtain a compounding heat stabilizer. The static and dynamic thermal stability of the PVC stabilized with this compounding heat stabilizer was measured by using Congo red test paper， thermal aging oven， and torque rheometry methods， and its thermal weight loss was analyzed by thermogravimetry. The results indicated that the heat⁃stabilized PVC achieved the best thermal stabilization effect at a mass ratio of sodium⁃A molecular sieve to β⁃diketone of 1/1， exhibiting a static thermal stabilization time of 84 min， a dynamic thermal stabilization time of 1 137 s， a shortest plasticization time of 104 s， and a minimum equilibrium torque of 37.94 N·m.
DING Wen
Abstract (
66 )
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Phosphorus⁃based flame retardant （FHPLC） was synthesized by using bisphenol fluorene （BPFL） and phenylphosphoyl dichloride （BPOD） as raw materials and then grafted onto waterborne polyurethane （WPU） to form a type of phosphate⁃based waterborne polyurethane （FHWPU） flame retardant. The resultant flame retardant was used for the flame⁃retardant coating of cotton fabrics. The feasibility of FHWPU on the flame retardancy of the flame⁃retardant coating of cotton fabrics was investigated. The results indicated that organophosphorus could be effectively grafted onto the FHWPU flame retardant， and the viscosity and particle size of the FHWPU flame retardant increased with an increase in the mass proportion of BPFL. The flame⁃retardant coating formed a dense FHWPU layer on the surface of cotton fabrics， resulting in an improvement in the mechanical and flame⁃retardant properties of cotton fabrics. The increments of the mechanical and flame⁃retardant properties were depressed with a decrease in the mass proportion of BPFL. The coated cotton fabrics reached a non⁃flammable level at a BPFL mass proportion of about 2.5 wt%. The results indicated that the FHWPU flame retardant was feasible for the flame retardancy of the coating of cotton fabrics.
Machinery and Mould
BI Chao, ZHAO Chong, WANG Binyuan
Abstract (
66 )
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In this paper， the energy consumption distribution of an extruder pelletizing component was systematically explored during the preheating and extruding stages. The findings indicated that the barrel set temperature was a pivotal factor influencing the energy consumption of the component during the preheating stage. In the normal extruding stage， the barrel set temperature， feed rate， and screw speed collectively exerted a significant impact on the energy consumption distribution of the extruder pelletizing component. To evaluate the impact of different speeds on the energy consumption of the component comprehensively， two working conditions were subdivided to be a small⁃range speed adjustment at a fixed feed rate and a large⁃range speed adjustment at a fixed main motor operating current.
LI Guolin
Abstract (
66 )
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A new stacked injection mold was designed according to the structural characteristics of the microwave oven inner cover. The mold adopts a new product layout， an interflow injection method， and a new lifter structure of hot and cold runners were adopted for the designed mold， resulting in a reduction in the mold cost by 40 % and a decrease in the tonnage of injection machines by 45 %. Through using a minimalist action control mechanism instead of the conventional stacked gear and rack action control mechanism， the molding cycle was shortened by 10 %. Square guide pillars and guide sleeves were adopted for the mold guiding and positioning system， improving the accuracy and lifespan of the mold greatly.
ZHANG Lihua
Abstract (
47 )
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A new multi plate the first mock examination with two cavities and a submarine gate and two⁃plate was innovatively designed for the injection molding of synchronous sealing shell plastic parts. In this mold， a zone and step demolding mode was adopted to achieve automated injection molding production of the plastic part. Such a specific method decomposed the entire circular groove on the inner wall into four sections， in which two sections were involved in the inward sliding blocks for core demolding， and other two sections were kept to use two "tile"⁃shaped lifters for side⁃core demolding. The semi⁃circular groove on the outer wall used two fixed mold side half slider blocks for side⁃core demolding， and the plastic part was ultimately pushed out of the mold by an ejector plate. The complete demolding of plastic parts was achieved through five actions of the mold， including three opening actions and two ejection actions， in which the third opening and two ejection actions were synchronous. The first mold opening allowed the inward sliding block to partially demold the inner wall circular groove， followed by the action of the half slider block of the outer wall to complete the side⁃core demolding. The second mold opening allowed the plastic part to detach from the cavity insert. The third mold opening included the second ejection action of the secondary ejection mechanism. The first ejection was achieved by using the first ejection plate of the second ejection mechanism to push the lifters out of the remaining circular groove on the inner wall. The second ejection plate pushed the plastic part out of the core molded part to complete demolding.
Review
ZHANG Liyan, YIN Rongzheng, TAN Jing, HOU Qinzheng, LI Changjin, YANG Tao, YANG Weimin, LI Haoyi
Abstract (
83 )
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To understand the development status of polyethylene （PE） ultrafine fibers as a chemical product， the nonwoven technology of ultrafine fibers at home and abroad was introduced and analyzed from the aspect of fiber fineness， and the spinning mechanisms， refining methods， and existing problems of wet spinning， flash phase separation， electrospinning， and melt blowing methods were reviewed. The key factors of wet spinning were high⁃quality gel solution and super drawing. The morphology of the prepared fibers was directly influenced by the degree of entanglement of polymer molecular chains， phase changes， and degree of synergistic curing and stretching of multiphase flow in flash evaporation phase separation. Due to the non⁃polar nature， high molecular weight， and high viscosity， PE is mostly electrospun through using solvents and conductive particles in solutions. However， greener melt electrospinning has attracted attention， because it can refine the fibers through blending small molecular substances， improving degradation temperature， lowering viscosity， and setting environmental temperature to extend whip time. The effect of process parameter on the separation of multi⁃component fibers after blending and melt spraying was analyzed. Finally， the hot research directions in future were pointed out， including the sustainable development technologies for supercritical green fluids and halogen⁃free environmentally friendly solvents.
WANG Yixiao, FANG Yuxuan, HOU Jiale, LIU Guoling, HAO Xufeng, WU Xinfeng
Abstract (
60 )
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This paper summarized and analyzed the preparation methods of highly thermally conductive boron nitride polymer⁃based phase change materials， including the blending， self⁃assembly molding， ice⁃templating， spinning method， and magnetic orientation methods. Meanwhile， the influence factors affecting the thermal conductivity and latent heat of the phase change materials was discussed.
ZHOU Wei, CHEN Jie, SI Zhihao, SHEN Fanglin, LUO Xiongfang, WANG Wenjuan, GU Yue, MENG Xinyi
Abstract (
61 )
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This paper reviewed the research progress in the antibacterial functional modification of gelatin matrix composites by using organic and inorganic materials. The effects of antibacterial agents， such as animal and plant extracts， carbon points， metal and metal compounding nanoparticles on the antibacterial functionalization of gelatin matrix composites were summarized. The applications and future development trend of antibacterial functional gelatin matrix composites were discussed.
