Materials and Properties
Jing ZHANG, Hong WANG, Wei ZOU, Zhongjie DU, Chen ZHANG
Abstract (
626 )
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267
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A surface chemical reaction was conducted to prepare the isocyanate?modified cellulose nanocrystals (IPDI?CNC), and the resulting product was blended with polyamide 6 (PA6) to improve its crystallinity. The effects of pristine CNC and IPDI?CNC on the crystallization degree, crystallization kinetic parameters, and crystallization kinetics of PA6 were investigated by differential scanning calorimetry. The results indicated that IPDI?CNC exhibited better dispersibility in PA6 than CNC due to a significant improvement in crystallinity of PA6 as a result of the surface modification by IPDI. The non?isothermal crystallization process was studied by the Jeziorny’s method, and the results demonstrated that IPDI?CNC could act as a heterogeneous nucleating agent to improve the crystallization speed and crystalli?nity of PA6. Moreover, the addition of IPDI?CNC reduced the water absorption of PA6 by 71.4 % due to the increase of crystallization degree.
Juan LIANG, Zewen JIANG, Weiguang GONG, Xin MENG
Abstract (
573 )
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314
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56 )
The chain?extended PLA was prepared by blending PLA with poly(amino?epoxy) silsesquioxane (PSQ), and phosphate?functionalized poly(amino?epoxy) silsesquioxane (PPSQ). The effect of phosphite ester groups on the chain extension and flame retardancy of PSQ in PLA matrix was investigated, and the flame retardant mechanism of PPSQ was further studied in detail. The results showed that the PPSQ significantly improved the molecular weight and complex viscosity of PLA in comparison of PSQ, indicating that the PLA?PPSQ compound achieved a better chain?extension effect. The incorporation of PPSQ also enhanced the flame retardancy of PLA and led to a limiting oxygen index of 25.4 vol% for the chain?extended PLA, which increased by 31.6 % compared to pure PLA. Furthermore, the heat release rate and total heat release of PLA?PPSQ compound also decrease by 18.1 % and 16.6 %, respectively. On the basis of the flame retardant mechanism, the introduction of phosphite ester groups into PSQ can promote the migration of silicon to the surface during the combustion of PLA?PPSQ compound and forms a dense carbon layer rich in silicon carbide and silicon oxide. Such a carbon layer can effectively inhibit the transfer of heat and oxygen and endows PLA with excellent flame retardancy accordingly.
Zijia LI, Enlong ZHEN, Baolei JIAO, Zhen QIAN, Weijun ZHEN, Ling ZHAO
Abstract (
550 )
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273
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53 )
A series of polyethylene (PE)/polyolefin elastomer (POE)/CaCO3 blending particles were prepared as a channel flow regulator for the fractured?vuggy carbonate reservoir, and the effects of CaCO3 content and PE/POE mass ratio on the density, adhesion, melting behavior and tensile strength of the blending particles were investigated. The results indicated that the density of the channel flow regulator increased with an increase of CaCO3 content, and the addition of CaCO3 could meet the requirement for the adjustment of density from 1.05 to 1.20 g/cm3. The PE/POE blending particles with different contents of CaCO3 varied from melting adhesion to softening adhesion by a combination of the relatively high temperature melting behavior of PE and the good adhesion property of POE. The melting temperature range and tensile strength of PE/POE/CaCO3 composites were also easily manipulated by the CaCO3 content and PE/POE mass ratio. However, the tensile strength of PE/POE/CaCO3 composites was found to increase with an increase of PE content at the same CaCO3 content.
Hongyue YUAN, Zhangyong JIN, Jing JIANG, Xianhu LIU, Zhenfeng ZHAO
Abstract (
863 )
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347
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The effect of the content of single?walled carbon nanotubes (CNTs) on the rheology, thermal stability, foaming behavior and mechanical properties of microcellular injection?molded polypropylene (PP)/CNTs composites was investigated. The results indicated that the complex viscosity of the composites gradually increased with an increase of CNTs content, and their thermal stability was also improved. The agglomeration occurred with the addition of 0.15 wt % CNTs, and however the size of agglomerates was fairly small and the substrates were tightly bound. The distribution of pores in the microcellular injection?molded samples was nonuniform, and the pore size ranged from 10 to 70 μm. The pore diameter decreased at first and then tended to increase with an increase of CNTs content. The elastic modulus and yield stress were found to decrease slightly after the microcellular foaming process according to the uniaxial tensile test results, and however the elongation at break increased by approximately 400 %. Moreover, there is no significant change in the mechanical properties of the foamed samples.
Wei ZHAI, Jianjian SUN, Bohua WANG, Chong TENG, Shiyu XIE, Fenghao HAO, Yujuan JIN
Abstract (
566 )
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317
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52 )
Hyperbranched ethylenediamine triazine polymer (HBETP) was synthesized by a one?step method using ethylenediamine and cyanuric chloride as raw materials and acetone as a solvent, and then polylactic acid (PLA)/polypropylene carbonate (PPC) blends were prepared by melt blending with HBETP as an impact modifier. The thermal properties, mechanical properties and the cross?sectional morphology of PLA/PPC/HBETP blends were investigated by means of differential scanning calorimetry thermogravimetric analysis, electronic universal testing machine and scanning electron microscopy. The results indicated that the elongation at break and impact strength of the blends increased by 266.0 % and 122.9 %, respectively, when 0.6 phr of HBETP was incorporated. HBETP can act as an effective impact modifier for toughening of PLA/PPC blends.
Man LI, Dingsheng WU, Jiali LI, Jinyan HU, Kefu WANG, Quan FENG
Abstract (
632 )
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370
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52 )
In this study, a solution was offered for the difficulty in electrospinning of ethylene?vinyl acetate copolymer (EVA) nanofibers by introduction of inorganic salts, and an adhesive material with a framework structure was obtained based on this nanfibers. A series of composites was prepared by hot compression with an EVA nanofiber sheet between two polypropylene melt?blown nonwoven layers, and the effect of hot pressing temperature on their shear strength was investigated. Furthermore, the tensile properties and air filtration efficiency were evaluated for the composites obtained at the optimum temperature. The results indicated that the EVA nanofibers exhibited a good morphology when prepared at a spinning solution concentration of 6 wt%, a CHCl3/THF mass ratio of 7/3, and a LiCl addition amount of 0.2 wt%. The composites achieved the maximum shear strength at the hot pressing temperature of 80 °C, and their air filtration efficiency reached over 98.71 %. Such a value was evidently greater than the filtration efficiency of the 4?layer commercial melt?blown mask cloth. Compared to uncompounded melt?blown fabrics, there is a significant improvement in the mechanical properties for the composites prepared in this work.
Chunhao CHEN, Zhongmei MIAO, Menghua XI, Bin GUO, Yanan HUANG
Abstract (
733 )
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263
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50 )
To improve the mechanical and water?resistant properties of thermoplastic starch plastics (TPS), a photo?crosslinking modification was conducted on the surface of TPS with 2,4,6?trimethylbenzoyldiphenyl phosphine oxide as a photoinitiator under the ultraviolet (UV) irradiation at different wavelengths. The effect of UV wavelength on the cross?linking degree, stretching performance, dynamic mechanic properties and water?resistance of modified TPS was investigated. The results indicated that the modified TPS achieved the maximum tensile strength of 4.1 MPa, flexural strength of 2.7 MPa, and impact strength of 96.8 kJ/m2. The modified TPS exhibited two glass transition temperatures at -37.48 and 50.32 °C in the starch and glycerol domains, respectively. Moreover, a maximum contact angle of 75 °C was obtained for the modified TPS, and their water resistance was improved remarkably. The characterization of cross?linking degree further confirmed that the TPS gained an optimum crosslinking structure.
Ya’e TANG, Bengang LIU
Abstract (
814 )
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238
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49 )
The blends of polystyrene (PS) and cross?linked poly(methyl acrylate) (PMA) were prepared by dissolving PS particles in a mixture of divinylbenzene, methyl acrylate (MA) and azobisisobutyronitrileand then initiating the polymerization of MA. The resulting blends were used to prepare a series of blend foams by an autoclave method. The structure and properties of PS/cross?linked PMA blends were characterized by a contact angle tester, differential scanning calorimeter analyzer, Fourier?transform infrared spectrometer and dynamic mechanics analyzer, and the structure of the blend foams was investigated by scanning electron microscopy. The result indicated that the introduction of cross?linked PMA improved the nucleation efficiency of the foaming system, and the contact angle of the blends decreased from 100.5 ° to 86.1 ° with an increase of MA content. The blend foams exhibited a narrow distribution in bubble size at the MA amount of 9.6 phr. Their cell size was distributed in the range of 40~60 μm, and their cell density reached 1.2×108 every square centimeter.
Processing and Application
Fucheng LI, Guofa ZHOU
Abstract (
645 )
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275
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50 )
The accurate prediction and precise control are two key technologies for the extrusion die swell deformation of medical heteromorphosis double?cavity catheter to realize the precision forming. A comparative analysis was performed for the traditional and gas?assisted precision extrusion forming. The results indicated that the extrusion die swell deformation was induced by the secondary flow driven by the second normal stress difference of the viscoelastic melt. On the other hand, a large second normal stress difference was generated during the traditional extrusion forming, and the secondary radial flow induced by the second normal stress difference was the direct driving force of the deformation caused by extrusion die swell. This led to the extrusion die swell and ellipticity error of the medical heteromorphosis double?cavity catheter obtained by traditional extrusion forming, and its maximum die swell ratio and ellipticity error were 1.86 and 6.3 %, respectively. The second normal stress difference of the viscoelastic melt could be basically eliminated by the gas assisted precision extrusion forming of the medical heteromorphosis double?cavity catheter, which eliminated the secondary flow in the extrusion process. Therefore, the high?precision shape control could be realized for the medical heteromorphosis double?cavity catheter.
Yanjun LI, Jiayu ZHAN, Miao JIN, Tong LI, Wenbo ZHANG
Abstract (
995 )
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394
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58 )
This paper provided a methodology for the determination of plastics pipeline span for overhead installation on the basis of the theory of material mechanics and creep test data. This method was applied to calculate the spans of PVC?U pipe for power installations and PE pipe for water supply. The results indicated that the plastics pipeline could meet the requirement for the use of urban integrated pipe gallery. This paper also gives a reference for further study on the long?term performance and applications of plastics pipeline.
Chunrui ZHANG, Jinyong JU
Abstract (
1024 )
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391
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60 )
Fused deposition modeling (FDM) 3D printed process has the advantages of low cost and high adaptability, and however the poor mechanical performance of the 3D printed preforms limits their wide applications. In this paper, the 3D printed preforms fabricated under four loading conditions of tension, compression, bending and torsion were taken as the research objects, and the filling rate and fill cell type were taken as the analysis parameters. The impact parameters for the filling rates of the 3D printed preforms were first determined to establish a general analytical relationship between the filling rate and geometric parameter of the lattice filling unit, and then the 3D geometric models were constructed for the 3D printed preforms with different filling rates. Furthermore, the finite element simulation analysis was performed for the 3D printed preforms to clarify the influence of filling rates on the mechanical properties under different load conditions. The simulation and experimental results indicated that there was a great influence from the filling rate on the tensile stress, compressive stress and bending stress of the 3D printed preforms, and however the influence could be ignored under the torsion. In this case, the optimum filling rates could be determined for the 3D printed preforms under the certain loading conditions. On the basis of the proposed three?dimensional modeling method, the mechanical properties of the 3D printed preforms can be simulated and analyzed effectively. This study generates a positive effect on reducing the test number of products and R&D cost.
Liangxian LIU, Zhihua FENG, Chunxue HU, Jinan GE
Abstract (
730 )
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407
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52 )
Aiming at the defect of small wall thickness near the bottom end of some molded PET bottles, a Polyflow? simulation software was adopted to perform a numerical simulation for the stretch blow molding process of PET bottles. The interactive orthogonal test method was used to optimize the combination of process parameters including the heating temperature of parison, the stretching speed of rod, pre?blowing pressure, delay time and high blowing pressure so as to improve the minimum thickness and uniformity of the bottle. An optimum combination of process parameters was achieved when the delay time was set as 0.06 s, the stretching speed as 1.6 m/s, the pre?blowing pressure as 0.7 MPa, and the heating temperature was set as 110 °C. After the process parameters were optimized, the minimum wall thickness and wall thickness uniformity increased by 28 % and 63%, respectively.
Additive
Xiang YU, Ruyang LI, Jingwen ZHAI, Huanhuan TAN
Abstract (
664 )
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523
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50 )
In this study, the PET/PAAS/activated carbon composites were prepared by a mechanical blending method, and their thermal properties, crystal structure and VOC content were investigated by means of differential scanning calorimetry, X?ray diffraction and high?performance liquid chromatography. The results indicated that the addition of activated carbon improved the crystallinity of the composites but reduced their VOC content. The melting point of the composites was found to increase at first and then tend to decrease with an increase of activated carbon content. The composites achieved the maximum melting point and breaking strength at the activated carbon contents of 0.75 and 0.25 wt%, respectively. When 1.25 wt% of activated carbon was incorporated, the composites exhibited a formaldehyde removal rate of 97.54 %, a acetaldehyde removal rate of 92.1 %, and a acetone removal rate of 80.2 %.
Machinery and Mould
Fangfang LIU, Weihe ZHANG
Abstract (
819 )
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419
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64 )
Aiming at the structural characteristics of the rearview mirror base of automobile as well as the problems occurring in their molding process, an optimization design was carried out for the mold structure. The problem of warpage deformation after plastic forming was solved with a pre?deformation technology. A reasonable and advanced pouring system was determined through the use of mold flow analysis, and the demolding problem was also solved by use of fixed?mode tunnel core, moving mode oblique core and the delayed pulling of diagonal push rod. By using a mesh format and a tilting cooling channel, the molding cycle was shortened from 35 s to 30 s.
Hong YANG
Abstract (
1006 )
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823
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66 )
In this paper, the mold flow analysis of plastic products of UAV upper cover was performed with the Moldflow analysis software, and several schemes of gating system were designed by combining with the molding technology of plastic products. The gating system of the UAV upper cover model was optimized through the analysis of mold flow, and a set of effective gating systems were determined. The injection process parameters were optimized, and the design of injection mold was completed on the basis of the analysis results. The product was found to meet the design requirements according to the molding test results.
Review
Run ZHANG, Ping XUE, Suwei WANG, Ke CHEN
Abstract (
1113 )
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769
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237 )
The latest research progress in the applications of shape memory polymers was reviewed in this paper, and the advantages and existing problems in the practical applications for aerospace, biomedical, electronic devices, intelligent textiles and self?assembly technology were analyzed. Meanwhile, the vital problems in the future development of shape memory polymers were discussed, and their developing tendency was prospected.
Qiming CAO, Xin MENG, Weiguang GONG, Chenyang LI, Zhongyang YAO
Abstract (
1176 )
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734
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78 )
Nucleating agents play a very important role in the crystallization of polylactic acid (PLA). This paper introduced the crystallization mechanisms of PLA and the development status of biomass nucleating agents for PLA in China and overseas. These biomass nucleating agents included polysaccharide (starch, cellulose, chitin, chitosan and cyclodextrin), phenol (lignin), alcohol (inositol), protein (amino acid) and carboxylic acid (orotic acid). Furthermore, the problems in the applications of biomass nucleating agents for PLA were analyzed, and their development in the future was prospected.
Beijing YANG, Xu YANG, Jingying SU, Haimei LI
Abstract (
966 )
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599
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74 )
This paper introduced the concept, composition and development status of spray?free plastics and especially discussed the surface quality of spray?free plastics, the formation reasons and relevant solutions of defects, and the application of numerical simulation for the prediction of processing quality. Moreover, the influencing factors of weather resistance and mechanical properties of spray?free plastic parts were analyzed. The application prospect and development direction of spray?free plastics were summarized.
