Materials and Properties
ZHANG Zhongfeng, LIU Shuncheng, WANG Kejian, REN Yueqing, CHEN Lanlan, SUN Xiaojie, LIANG Wenbin
Abstract (
1059 )
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The PE-HD/POE blends were modified by crosslinking with BIPB as a peroxide crosslinking agent. The gel content of the crosslinked PE-HD/POE was analyzed， and the effect of crosslinking modification on the rheology and crystallization of PE-HD/POE blends were investigated by rotary rheometer and DSC. The tensile and impact properties were characterized， and impact fracture surfaces were observed by SEM. The results indicated that the crosslinking modification increased the complex viscosity of the blends and inhibited their crystallization， resulting in a decrease in crystallinity and thinner wafers. When 0.3 wt % of BIPB was added， the notched impact strength of the blends reached 61.1 kJ/m2， and their elongation at break exceeded 900 %. When the crosslinking degree was low， most of the molecular chains in the blends could move freely. The toughening mode was attributed to the low entanglement that produces large deformation to form a shear yield zone to offset the impact energy. With the improvement of crosslinking degree， the toughening mode was converted to the high entanglement that generated a large amount of small deformation to dissipate the impact energy at a high cross-linking degree， leading to a better toughening effect.
YU Wangwang, LIU Qin, ZHANG Ying, YANG Cheng, LEI Wen
Abstract (
992 )
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559
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The effects of maleic anhydride-grafted polypropylene（MAPP） and ethylene acrylic acid copolymer（EAA） on the properties of polypropylene（PP） /wheat straw powder（WSP） composites （PP/WSP） were investigated. The results indicated that the tensile and flexural strengths of PP/WSP increased with an increase of MAPP content. However， their impact strength increased at first and then tended to decrease. Moreover， the time for PP/WSP to reach the melting peak was prolonged. When EAA is used for the composites， the tensile， flexural and impact strengths were all found to increase no matter whether MAPP was used or not， especially for the composites without MAPP. The tensile， flexural and impact strengths of PP/WSP increased by 65.04 %， 45.42 % and 6.75 %， respectively. Moreover， their storage moduli were enhanced， and their surface hydrophobocity was strengthened. The balance torque of the composites also decreased from 13.9 N·m to 11.8 N·m， and their dimension change rate and water uptake rate after immersion in water decreased. The time to reach water absorption equilibrium was shortened. The addition of EAA could improve the interfacial bonding between WSP and PP. As a result， the mechanical properties， thermal stability， surface hydrophobicity， dimensional stability and processing convenience of the composites were all modified. In addition， their water uptake was reduced.
YANG LU, CHEN Hanting
Abstract (
773 )
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390
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The self-assembly was induced for a hydrophilic random copolymer of poly（DMAEMA-co-AA） in pure water， and the self-assemblies were fabricated by loading antibacterial active components. The results indicated that when the random copolymer contained 51.6 wt % of AA， poly（DMAEMA-co-AA） tended to form spherical and porous spherical self-assemblies in pure water. With an increase of pH value， the self-assemblies exhibited a “breathing” behavior and varied from small-size spheres to porous spheres. More than 85 % ethyl p-hydroxybenzoate sodium as an antibacterial component could be stably loaded on the self-assemblies to form the antibacterial nanomaterials. Moreover， the other antibacterial components could also be loaded on the self-assemblies. The antibacterial nanomaterials achieved a logarithmic antibacterial value of above 4.4， and they could prolong the storage time of food at room temperature when used for anti-bacterial packaging.
YUE Lina, SUN Yingjuan, ZHU Taohua, GAO Fan, CHAI Zhiyong, ZHAO Ziwei, CHANG Ge
Abstract (
866 )
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1001
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In this research， bacterial cellulose was modified by carboxylate on the basis of its polyhydroxyl structure， and then the polypyrrole/carboxylated bacterial cellulose conductive composites were prepared by in-situ compounding with polypyrrole as a raw material and carboxylated bacterial cellulose as a template. The microstructure， chemical structure and thermal stability of the resulting composites were evaluated， and the effect of carboxylate degree on the electrical properties of the composites were investigated. The results indicated that the electronic conductivity of the composites increased with an increase of carboxylate degree， and it reached a maximum value of 10-3 S/cm. The sample with a code of 0.04-48h achieved the optimum ionic conductivity.
QIAO Wenyu, WANG Chenglei, HU Hao
Abstract (
1374 )
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950
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19 )
Based on the characterization results of commercial PETG filaments as raw materials， PETG 2012 was selected as the matrix resin for the preparation of PETG filament for fused deposition modeling （FDM）. The PETG resin was modified by PC to improve its toughness and strength when used for the preparation of 3D printing filament. The test specimens were printed by FDM， and the effect of PC content on the performance of PETG filament and printed parts was investigated. The results indicated that PETG and PC had good compatibility at low contents of PC， and there was no obvious phase separation observed between the two phases. The blends showed a decrease in fluidity with an increase of PC content. Moreover， the PETG-printed parts exhibited an improvement in Vicat softening temperature and heat deflection temperature with an increase of PC content. In addition， the addition of PC improved the mechanical properties of printed parts significantly. The tensile strength of printed parts increased with an increase of PC content， and however their notched impact strength increased at first and then tended to decrease with an increase of PC content. To make PETG/PC filament meet the use condition of FDM 3D printers， the ratio of PETG and PC should be set to 1∶1 when preparing the PETG/PC filament， thus leading to excellent mechanical properties for 3D printing filaments.
ZHANG Xue, GUO Huiliang, ZHONG Zhenhua, CAI Pingxiong
Abstract (
933 )
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484
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In this paper， the titanium dioxide for color masterbatch was studied， and their conventional properties， resin system， temperature and weather resistance were investigated with the type and amount of coating agent as variables. Moreover， the relevant mechanisms were analyzed. The results indicated that the whiteness and oil absorption of trimethylol propane（TMP） decreased with an increase of coating agent content， whereas the volatile matter increased. The maximum whiteness of TMP coating reached 97.64， which was better than those of the other samples. In the PP resin system， the b* value decreased. The performance of TMP was better than the other three systems in the temperature resistant system， and it was also better than that of the standard sample at the coating content lower than 0.5 %. In the weathering system， the samples containing the TMP dosage of 0.5 and 0.7 wt % were better than the standard one. These results may be attributed to the fact that TMP has more functional groups， and therefore it can better wrap on the surface of titanium dioxide.
PENG Jingang, ZHU Ruixia, FAN Yingkui, SUN Baozheng, CHENG Liang
Abstract (
1052 )
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749
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In this paper， a hoop tensile test method was adopted to detect the hoop tensile strength of high-density polyethyene （PE-HD） pipes， and the effect of the change of curvature caused by the deformation of the sample on the hoop tensile strength was investigated during the test. In the experiment， the optimized parallel tests were carried out to obtain accurate test data. After the collection of the huge amount of test data， the results indicated that for the PE-HD pipes with the same outer diameter， their hoop tensile strength decreased by 10 % with a reduction of the curvature of hoop tensile specimen under the test. Moreover， the effect of the variation law of curvature on the hoop tensile strength of PE-HD pipes was discussed.
Processing and Application
TIAN Renjie, ZHU Guangming, LYU Yuwei, WU Taotao, REN Tianning, MA Zhiliang, ZHANG Shuang
Abstract (
982 )
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1025
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Polyetheretherketone （PEEK）/carbon black （CB） blending sheets with an thickness of 0.5 mm were prepared by a compression molding process using Victrex PEEK-450PF as a raw material， and their optical characteristics were characterized by a laser power meter and UV-Vis-IR spectrophotometer. The effect of CB content on the laser energy deposition efficiency of blending sheets was investigated under the process condition of a laser power density of 35 W/cm2 and a moving speed of 5 mm/s. A numerical model was established for the laser energy absorption of PEEK by using the COMSOL software. The results indicated that pure PEEK sheet did not strongly absorb the laser at a wavelength of 1070 nm. However， the addition of CB could significantly reduce the reflection and transmission of PEEK to the laser and enhance the photo?thermal conversion efficiency of blending sheets. There was little effect on the tensile strength of blending sheets. In addition， the numerical simulation results were found to be in good agreement with the experimental ones.
HUANG Guojia, LI Lushui, XU Qingyong, XIN Mingliang
Abstract (
890 )
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611
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Thermogravimetric analysis was used to determine the thermal decomposition process of PE100 compound for gas pipes at 2， 5， 10， 20 °C/min under four different heating rates in nitrogen. The thermal decomposition kinetics and mechanisms of PE100 compound were investigated by the Kissinger， Flynn-Wall-Ozawa and Coats-Redfern methods. The Toop method was used to evaluate the lifetime of PE100 compound at different temperatures. The results indicated that the thermal decomposition of PE100 compound presented a typical one-step reaction， and its average activation energy was 327.8 and 304.6 kJ/mol obtained from the Kissinger and Flynn-Wall-Ozawa methods， respectively. Moreover， the lnA value of apparent prefactor for PE100 compound was 53.9 min-1. Among the 12 common thermal decomposition models， the cylindrical symmetric contraction （R2） was considered as the most suitable mechanism to describe the thermal decomposition process of PE100 compound. The lifetime of PE100 compound obtained by Kissinger and Flynn-Wall-Ozawa method at 50 °C was 7.4×108 and 7.9×107years， respectively. However， the lifetime decreased rapidly with a rise of temperature.
LIU Xuejun, JIANG Hui
Abstract (
926 )
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In this work， two methods were adopted to calculate heat transfer coefficients at the internal surface of a cylindrical rotational mold in the heating process. In the first method， the test temperatures at the mold surface and inside were adopted to calculate heat transfer coefficients at the internal surface of the mold via a heat equilibrium equation for the internal space of the mold. In the second method， the formula for the heat transfer coefficients between the powder material in the rotary kiln and the kiln wall was used to calculate the coefficients at the internal surface of rotational mold. Both of the methods were used to calculate instantaneous and average heat transfer coefficients at the internal surface of the mold in the cases of no powders and powders of 0.21 kg loaded. The boundary layer theory of fluid mechanics was applied to explain the variation of heat transfer coefficients at the internal surface with time. The average heat transfer coefficients obtained by the first method were processed in the form of a dimensionless correlation of Nu with Pr （Nu= 45.73 Pr-0.55）. The correlation holds for a cylindrical rotational mold with its axial length larger than inner diameter， which rotates along its central axis. The results indicated that the average heat transfer coefficients at the internal surface decreased with an increase of the volume percentage of powders inside the mold. The results calculated by the above two methods were found to be in good agreement with each other. The relative error of calculated results by the second method was less than 20 % as long as the volume percentage of powders was higher than 62.4 vol %.
PENG Guorong, SUI Lili, LU Longfu
Abstract (
849 )
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822
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According to the characteristics of the inner wall of curved pipe with variable cross-section and the inner wall of straight pipe， the mathematical model was established for the demolding force of the inner wall of curved pipe by using a calculus method， and the demolding force of the core of connecting pipe was calculated. Based on the obtained results， the demolding mechanism of the inner wall of curved pipe was optimized and designed for the plastic part， and this mechanism was driven by a single oil cylinder to rotate and pull out the core of the two-sector gear bent pipes. On the basis of the demolding mechanism set in this work， the mold structure of plastic part was composed of a mold with two cavities and a single opening and two-plate mold. In this mold， there are two groups of external thread demolding mechanisms with a Haver slider and a sector gear bent pin core-pulling mechanism driven by a linkage oil cylinder. The die structure is simple and practical， and the action of mechanism is reliable. This design can offer a good reference for design of other similar molds.
Additive
GU Xiaohua, LYU Shiwei, LUO Hongxiang, LI Yan
Abstract (
812 )
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540
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Polyols were obtained by degrading waste PU rigid foams with cross-linking agents and catalysts containing small-molecular alcohols. The resultant degradable materials were blended with polyether polyols， catalysts and blowing agents to prepare white materials and then mixed with black isocyanates to get the regenerated PU hard foam. The rege-nerated PU rigid foam was analyzed in terms of the viscosity， hydroxyl value， density， strength， water absorption， thermal stability， infrared spectroscopy and scanning electron microscopy， and the effect of addition amount of catalyst on the recycling and reuse of the waste PU rigid foams was investigated. The results indicated that the waste PU rigid foams achieved the optimum degradation effect when 0.9 g of KOH catalyst was added. The density of regenerated PU hard foam was 37.6 kg/cm3， its compressive strength was 164.2 kPa， its thermal conductivity was 0.015 24 W/（m·K ）， and the water absorption rate was 0.429 5 %.
Standard and Test
HU Ping, LI Dagang
Abstract (
562 )
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438
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A method for determination of alkylphenols in the plastics for footwear productions was developed by gas chromatography mass spectrometry. The samples were obtained from ultrasonic extraction， and the extraction solvent， temperature and time were optimized. After purified with a membrane filter， the extracts were quantitatively determined by a GC-MS method， and then their quantification was performed by an external standard method. The calibration curves of alkylphenols were linear in the range of 0.1~10 mg/L with correlation coefficients （r2） more than 0.995. The detection limit was in the range of 0.3~1.1 mg/kg. The spiked average recoveries varied from 80.7 % to 113.3 % at three spiked levels with the relative standard deviations （n=6） of 1.3 %~8.6 %. The method developed by this work was simple， rapid， accurate， stable， and reproducible for determination of alkylphenols in the plastics for footwear productions.
Machinery and Mould
Hui XU
Abstract (
979 )
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770
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Aiming at the difficulties in performing the injection molding automation of plastic parts， a pair of single point submerged gate and two-plate twice-open mold injection mold were designed. The mold layout was set as one mold with two cavities. The single cavity mechanism in the mold was set as a fixed mold side with a fixed mold ejection mechanism driven by oil cylinder. On the side of the moving mold， there were two special compound mechanisms with an inclined roof and a slider block， a universal inclined roof mechanism， a tunnel slider block mechanism and an ejector pin ejection mechanism. The ejector mechanism of the fixed mold was driven by the oil cylinder to drive the fixed mold ejector plate to drive six inclined ejector rods to demold the six inverted buckle features automatically. Two special composite mechanisms were designed to be composed of a double slider with an inclined roof three times composite core pulling mechanism and a single slider inclined roof two times core-pulling mechanism. The function of these two mechanisms was to drive the slide block through the inclined guide pillar so as to drive the inclined top in the slide block to implement the secondary core pulling for the purpose of multiple multi-directional core pulling in the local area of the plastic part. In this mechanism， the use of universal inclined roof mechanism can effectively reduce the height and size of the mold. Moreover， by using the tunnel slider inclined core-pulling mechanism and adding a template opening by the side of the moving mold to drive the tunnel slider to implement inclined core pulling， the mold opening power can be utilized effectively， and the mold manufacturing cost can be reduced.
XUE Li, WANG Xunjie
Abstract (
825 )
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805
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Aimed at the requirement for the automatic injection molding production of complex plastic parts for a scroll compressor air valve，a type of three-plate mold with two cavities was designed. In this mold， according to the structural characteristics of four local features of the plastic parts， four kinds of demolding mechanisms were optimized to implement automatic demolding， which included a four-time demolding composite mechanism， a two-time demolding composite mechanism， an inclined guide pillar slider mechanism and a fixed mold bending pin core pulling mechanism. In the four-time demolding composite mechanism， the first core demolding of central inner hole was completed by using an external cylinder mechanism， then the second and third core demolding of mouth and end face were completed by using a delay slider mechanism， and finally the forth rotation core demolding of internal thread was completed by using the cylinder rack mechanism. In the second demolding composite mechanism， the first core demolding of central inner hole was completed by the inclined guide pillar slider mechanism， and the second core demolding of internal thread was completed by a cylinder rack mechanism. A universal mechanism was adopted to design the slider mechanism and fixed mold bent pin core pulling mechanism. Through the optimization design of the cylinder rack driving mechanisms in the four-time and two-time compound mechanisms， the overall structure size of the mold was optimized， and the operation cost of injection-molding machine was reduced effectively.
Review
YE Bading, LU Chenfeng, CHU Nengkui, SHEN Haibo, LI Binbin, XIE Pengcheng
Abstract (
1065 )
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1456
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38 )
This paper introduced the characteristics of all-electric injection molding machine， reviewed the research progress in the all-electric injection molding machine in the aspects of precision injection， intelligent injection， efficient injection and green injection at home and abroad， and briefly introduced the applications of all-electric injection molding machine in the auto parts electronics industry. The gradual maturity of dual-motor synchronous control technology provides a motivation for realizing the large-scale production of all-electric injection molding machine. The all-electric injection molding machine exhibits great potential for applications in the auto parts electronics industry due to its advantages of high efficiency， precision， intelligence， energy saving and environmental protection.
WEI Shiyi, TANG Yuntao, CHAI Chenze, ZHANG Yuxia, ZHOU Hongfu
Abstract (
1199 )
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1030
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This paper reviewed the research progress in the modified PLA open-cell materials， including biodegradable PLA blends， PLA/filler composites and copolymers of PLA. Furthermore， the preparation process， open-cell properties such as cell morphology， size and its distribution and open porosity， and the mechanical properties of PLA open-cell materials were elaborated. Moreover， the characteristics and applications of PLA open-cell materials were introduced.
WANG Xingran, WANG Minghao, DUN Dongxing, LI Shanzhe, ZHANG Xuedong, ZHOU Hongfu
Abstract (
848 )
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835
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In this paper， the research progress of polymer/carbon fillers foaming composites （PCFC） applied in the field of electromagnetic shielding was introduced. The effect of various carbon fillers （graphene， carbon nanotubes， carbon fibers） on the electromagnetic shielding performance of PCFC as well as their electromagnetic shielding mechanism were discussed systematically. Research demonstrated that the functionalization of carbon fillers， the regulation of cell structure， the design of multi level structures， the optimization of preparation process， etc. are effective approaches to improve the electromagnetic shielding performance of PCFC.
