Materials and Properties
TAN Liqin, LIU Weiqu, LIANG Liyan, LIN Jiaming
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912 )
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In this article， mercaptan silicone （PMMS） was firstly synthesized with hydroxyl?group?containing silicone oil and 3?mercaptopropylmethyldimethoxysilane as monomers. Then， a series of mercaptan?silicone?modified styrene?acrylic waterborne composite emulsions were prepared via seed emulsion polymerization with PMMS as a modifier and butyl acrylate， methyl methacrylate， styrene， and acrylic acid as monomers. Infrared spectroscopy， nuclear magnetic， and gel permeation chromatography were performed to characterize the structure and molecular weight of PMMS. The waterborne emulsion stability， water resistance， thermal stability， and mechanical properties of the samples loaded with various amounts of PMMS were further investigated using dynamic light scattering， thermogravimetric analysis and scanning electron microscopy， etc. These results demonstrated that the modified emulsion had good dispersion and excellent stability with the addition of 6 % PMMS （quality score）. Compared to pure latex film， the contact angle of the modified latex film increased from 31.1 ° to 97.8 °， and the water absorption rate decreased from 6.53 % to 2.96 %. In addition， the mechanical strength and decomposition temperature at 5 % weight loss of the modified latex film increased by 62.9 % and 75.79 °C than pure latex film， respectively.
MAO Chen, LIU Fan, E Yi, ZOU Shuyan, GONG Xinghou
Abstract (
658 )
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To realize the functionalization of PLA， the crystallization behavior of the modified PLA was investigated intensively. CoFe2O4 nanoparticles coated with oleic acid were first prepared using a chemical co?precipitation method， and then the PLA/CoFe2O4 composites were prepared using a solution casting method. The composition and structure of CoFe2O4 particles and the composites were investigated using Fourier transform infrared spectroscopy（FTIR）， transmission electron microscope（TEM）， and X?ray diffractometer （XRD）， and the crystallization behavior of the composites were analyzed using XRD， differential scanning calorimeter（DSC） and polarizing microscope（PLM）. The results indicated that the CoFe2O4 particles （10~20 nm） were uniformly dispersed in PLA without obvious agglomeration. A small amount （≤1.5 %） of CoFe2O4 particles could generate a significant heterogeneous nucleation effect on the crystallinity of PLA， promoting its crystallization and improving its crystallinity. With a maximum increase of 207 %， the excessive CoFe2O4 particle content generated a hindering effect on the crystallization of PLA.
JIAO Qi, LI Ruilong, CHEN Couxi, ZHANG Shouyu, SONG Chengpeng, CHEN Tonghai, JIANG Ruyuan, ZHENG Pengcheng
Abstract (
652 )
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A series of ternary antioxidant composite systems based on Irganox?1010 and 1076 as main antioxidants， Irgafos?168 as an auxiliary antioxidant， and Revonox?501 as a carbon radical capture agent. These antioxidant composite systems were applied for the modification of coal?based homopolypropylene （homo?PP） to enhance its thermo?oxidative aging performance. The resultant modified homo?PP samples were evaluated using polarizing optical microscopy， DSC， TGA， SEM and oxidation induction time， and their lifespan was predicted using the parameters obtained from TGA thermal analysis. The results indicated that the ternary antioxidant composite system had a much better enhancement effect on the thermo?oxidative aging performance of the coal?based homo?PP than the binary one， thus resulting in a much grea?ter OIT value. The incorporation of antioxidant composite system slightly enhanced the crystallinity of the coal?based homo?PP because the scission of PP molecular chains could be effectively prevented during the melting process. A synergistic effect derived from the ternary antioxidant composite system could improve the thermal stability of the coal?based homo?PP and prolong its lifespan at various ambient temperatures. A lifespan prediction demonstrated that the coal?based homo?PP modified with an optimal formulation of antioxidant composite system achieved a lifetime of 4.55×105 h at an ambient temperature of 50 ℃.
CHANG Pin, ZHANG Yi, SUN Feng, QIAO Liang, FAN Junming
Abstract (
682 )
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In this paper， monotonic tensile tests were first conducted using five high?density polyethylene （PE?HD） round bar specimens with different notch radii to study the effects of notch radius on the curves of engineering stress?displacement curves. Moreover， punch tests were also conducted on the PE?HD plate specimens to investigate the load?displacement curves with an indenter diameter and a punch speed. Finally， three empirical equations for the prediction of yield stress of PE?HD materials based on characteristic punch load were proposed. The results indicated that the yield stress obtained from the monotonic tensile tests increased with a decrease in notch radius at the same loading speed. Additionally， the maximum punch load increased with an increase in the indenter diameter or punch speed. The predicted yield stress based on the empirical equation is closest to the tensile test result when using the indenter diameter as variable.
WANG Qiyang, YANG Xiao, CHEN Jihuan, HE Yuexing, YANG Dongmei, HU Boyang, GUO Hong, LI Baoan
Abstract (
807 )
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542
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Polyethylene?based composites （N?PE?HD/P?GNPs） with a honeycomb graphene framework were prepared through electrostatic induction self?assembly and hot pressing process employing poly（diallyldimethylammonium chloride）?modified graphene nanosheets （P?GNPs） and polystyrene sulfonate?modified polyethylene particles （N?PE?HD） as raw materials. The morphology， microstructure， thermal conductivity， and mechanical properties of the composites were characterized using Fourier?transform infrared spectrometer， scanning electron microscopy， thermal conductivity tester， and electronic tensile testing machine. The results indicated that the formation of a continuous graphene framework effectively improved the thermal conductivity of the polyethylene?based composites. The N?PE?HD/P?GNPs system exhibited a thermal conductivity of 2.51 W/（m·K） with the addition of 20 wt % P?GNPs. This result is higher than 1.71 W/（m·K） of PE?HD/GNPs system by 1.47 times and 0.44 W/（m·K） of pure PE?HD matrix by 5.70 times. The N?PE?HD/P?GN Ps composites also showed tensile strength of 29.1 MPa， Young's modulus of 114 MPa， and elongation at break of 48 %. Their melting point and thermal decomposition temperature were determined to be 135.2 and 458 ℃， which are higher than those of pure PE?HD by 2 ℃ and 11 °C， respectively.
CAI Haokun, DONG Jian, JIANG Zhongyi
Abstract (
1798 )
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The effect of carbon black on the physical properties of polyethylene pipes with different carbon black weight fraction was investigated. the results indicated that carbon black had a certain effect on the oxidation induction time（OIT）， tensile properties and density of the thermoplastic compounds. With the same raw materials and process， the density was linearly related to the content of carbon black， and the density increased with an increase in the content of carbon black. In the carbon black content range of 1.43 %~3.51 %， the OIT became smaller with an increase in the dispersion grade of carbon black， and the OIT at 200 ℃ increased by 1.3~1.6 times compared to that at 210 ℃. The concept of the fracture success rate was defined as the stretching enough samples until five samples were successfully broken with the ratio of five to the total number of tests. The fracture success rate became smaller with an increase in the dispersion grade of carbon black. Moreover， it was proposed that the national standard GB/T 8804.1—2003 only required the data of successful breaking. This cannot reflect the tensile quality of pipes objectively and truly. It was suggested to consider the concept of fracture success rate.
WANG Fei, LIU Lichao, XUE Ping
Abstract (
739 )
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Ultra?high molecular weight polyethylene （PE?UHMW） and high?density polyethylene （PE?HD） blend fibers with tensile strength of 1.13 GPa were prepared via a melt spinning process. The crystal structure and mechanical pro?perties of the as?spun filaments and fibers were investigated using differential scanning calorimetry （DSC）， scanning electron microscopy （SEM）， X?ray diffraction （XRD）， sound velocity orientation test and tensile strength test. The results indicated that the degree of molecular chain orientation， crystallinity， and mechanical properties of the blend fibers were improved by blending with PE?HD having a low melt flow index （MFR）. For this type of blend fibers， their crystal grains formed by more highly oriented molecular chains could be stretched more effectively in the drawing direction， resulting in an improvement in mechanical properties due to a more regular and compact crystal structure.
WANG Zhenhua, YANG Zheng, JU Aoying, LU Shike, LIU Baoying, FANG Xiaomin, DING Tao, XU Yuanqing
Abstract (
744 )
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563
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Silane coupling agent （KH550 and KH560） and polymer interfacial compatibilizer M were used to modify the glass fiber reinforced polyformaldehyde composites （POM/GF）， and the mechanical properties of the resultant compo?sites were investigated using an electronic universal testing machine and a pendulum impact testing machine. Scanning electron microscopy， rotating rheometer and differential scanning calorimetry were conducted to investigate the effects of the type and content of compatilizer on the profile， rheological behavior， crystallization properties， and dynamic thermomechanical properties of the composites. The results indicated that the polymer compatilizer M had a better compatilizing effect on the POM/GF composites than the small molecules KH550 and KH560. The tensile strength， bending strength and notched impact strength of the POM/GF composites containing 0.5 wt % M reached 120.9 MPa， 170.5 MPa and 8.58 kJ/m2， respectively， which were increased by 14.2 %， 19.1 % and 32.3 %， respectively， compared to the composite without M. In addition， the incorporation of M increased the crystallization temperature of the composites， reduced their crystallinity， and promoted their crystallization process.
ZHANG Yunpeng, LIU Xiangwei, WANG Zhiming, ZHANG Zhao, WANG Qingzhao
Abstract (
704 )
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In view of the poor wear resistance and difficulty of replacement of seamless steel pipes used in coal mine paste delivery， the glass?fiber?reinforced PVC thermoplastic composite pipes （PVC?RTP） were developed for the use in the underground filling of coal mine， and their part composition， connection mode， process flow and process parameters were introduced comprehensively. The performance of the pipes at a nominal pressure of 9.5 MPa was also detected. The results indicated that the pipe exhibited a blasting pressure of 38.95 MPa， which was 4 times greater than the nominal pressure. There is no crack occurring in the pipe under the test time of 100 h and test pressure of 14.25 MPa. There is no leakage at 11.4 MPa. After 1 000 h， the pipes showed no rupture and no leakage. At a nominal pressure of 11.4 MPa and a ΔP/PN ratio of 48 %， the number of cycles reached 12 000， and no rupture and leakage were observed. With the characteristics of light weight， high wear resistance， and strong corrosion resistant， the composite pipes can better meet the requirement for the transportation of coal mine paste.
GUAN Tonghui, FU Ye, WENG Yunxuan
Abstract (
1449 )
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This paper focused on the degradation behaviors of poly （butylene?adipate?co?terephthalate） （PBAT） mulch under the soil?buried condition. Fourier transform infrared spectroscopy （FTIR）， X?ray photoelectron spectroscopy， thermogravimetric analysis， scanning electron microscopy， and gel permeation chromatography were conducted to analyze the changes of chemical structure， surface element analysis， thermal stability， surface micro?morphology， and molecular weight of PBAT films during the degradation process. After bury for four months， the FTIR spectra of PBAT showed attenuation in the intensity of C—O absorption peaks due to the broken ester bond in their molecular chains. The atomic ratio of O to C increased from 0.27 to 0.77， whereas the bonding energy of these elements decreased. The thermal stability of PBAT decreases due to the changes of aggregation state. The results indicated that the degradation of PBAT occurred at the molecular level during the burying experiment， resulting in a complete degradation of the whole biodegradable membrane in the soil.
WANG Lin
Abstract (
700 )
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987
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The enhancement effect of BASF low yellowing compound antioxidant system A on the anti?yellowing of PE?HD was evaluated， and their anti?yellowing， anti?oxygen and processing stability were investigated intensively. The results indicated that BASF antioxidant system A had a better anti?yellowing effect than normal antioxidant systems. After using the recommended dosage and double dosage， the yellowing degree of the product was low， and its yellow index changed little after multiple extrusion. However， its anti?oxidation effect was poor. The problem of yellowing can be resolved through reducing the content of antioxidant 1010.
ZHU Nenggui, SHEN Chao, LI Shengnan, ZENG Xiangbu, JIANG Tuanhui, ZHANG Xiang
Abstract (
571 )
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341
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Polypropylene/fly ash （PPFP1919/FA） micro foaming composites were prepared by chemical micro foaming method， and the rheological properties， foaming quality and mechanical properties of PPFP1919/FA composites with different FA content were studied. The results shows that the dispersion of FA in PPFP1919 matrix can improve the melt strength， melt elasticity and foaming ability of the composites. In addition， FA also plays a heterogeneous nucleation role in the foaming process， providing nucleation point， which improves the foaming quality and foaming effect， and the mechanical properties of the composites after foaming are affected to a certain extent. Comprehensive analysis shows that when FA content was 10 phr， the foaming effect of PPFP1919/FA micro foaming composite is the best.
Processing and Application
ZHENG Fangli, FU Nanhong, JIAO Xiaolong, YANG Weimin, XIE Pengcheng
Abstract (
633 )
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In this paper， the development status of artificial intelligence technology for the three types （expert system and case?based reasoning， evolutionary computation and machine learning） of injection molding parameter setting and optimization was reviewed， and some suggestions for future research directions were proposed.
ZHANG Dingran, LU Lingang
Abstract (
620 )
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Thermogravimetry analysis was conducted to investigate the pyrolysis status and mechanism of calixarene and 4?tert?butylcalixarene under a nitrogen atmosphere. Meanwhile， the reaction activation energy and the optimal mechanism function equation of the two pyrolysis processes were obtained using a thermal decomposition kinetics method. The results indicated that the overall structure of 4?tert?butylcalixarene was more stable due to the strong interaction between the C—H σ and C＝C π bonds. Calixarene exhibited excellent char forming performance， and 4?tert?butylcalixarene presented an excellent thermal stability. Their decomposition temperatures are very suitable for the use of polymer materials， Moreover， the pyrolysis kinetic analysis demonstrated that the activation energies of calixarene were determined to be 179.14 and 192.84 kJ/mol through calculation using the Kissinger′s and Flynn?wall?Ozawa′s methods， respectively. The activation energies of 4?tert?butylcalixarene were calculated to be 291.61 and 312.14 kJ/mol using the Kissinger′s and Flynn?wall?Ozawa′s methods， respectively. According to the Coats?Redfern method， the pyrolysis mechanism function of calixarene was determined to be g（α）=［-ln（1-α）］1/3 and its reaction order n was 1/3. Its non?isothermal pyrolysis mechanism belongs to random nucleation and subsequent growth reaction. The pyrolysis mechanism function of 4?tert?butylcalixarene was g（α）=α1/3 and its reaction order n was 1/3.
YANG Bo, XU Bin, YANG Chaolong
Abstract (
542 )
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To explore the influence of the key factors on the imbalance of polymer melt filling at a micro scale， a numerical simulation experiment was conducted using polyoxymethylene as a raw material in a semi?circular H?shaped symmetrical distribution microchannel system with the consideration of the mold temperature， melt temperature， injection rate and microchannel size. The temperature difference data between the symmetrical points at the sprue was analyzed.The obtained results indicated that there was a temperature asymmetry in the flow channel system during the process of microinjection， and the temperature difference between the symmetrical points increased with an increase in injection rate. The larger the melt inlet temperature， the greater the temperature difference between the symmetry points， and the more obvious the filling imbalance. The smaller the microchannel size， the smaller the temperature difference between the symmetrical points. The filling imbalance was also improved. Increasing the mold temperature can reduce the convective heat transfer between the melt and the wall surface. This could reduce the temperature difference between the symmetrical points and improve the imbalance of filling.
HE Jinhui, WANG Haixiong, LIU Shankun, LI Yajun
Abstract (
606 )
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365
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To understand the influence of ultrasonic vibration on the mechanical properties of fused deposition molded （FDM） products and the correlation between various variables， an ultrasonic vibration system was added to the original fused deposition molding equipment， and the fused deposition molding process was studied through combining a single factor experiment method with a quadratic regression orthogonal rotation combination experiment. In this study， the printing shell thickness， filling density and ultrasonic power were taken as research objects. The results indicated that ultrasonic vibration power generated a great influence on the tensile properties of materials. Under the same conditions， the materials achieved an increase in tensile properties by 13.8 % after ultrasonic treatment. Through response surface analysis and variance analysis， it is concluded that the above three factors and the interaction between shell thickness and packing density exhibited the most significant influence on tensile properties. The optimum technological parameters were determined to be a shell thickness of 1.2 mm， a packing density of 90 %， and an ultrasonic power of 40 W. The quadratic regression model of shell thickness， packing density and ultrasonic power was established using the test data， and the reliability of the regression model was tested. The obtained results indicated that the regression model was reliable and could be used to predict the optimized processing conditions of the tensile test.
YE Donglei, LIU Xuejun, WANG Xiao
Abstract (
596 )
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207
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Two kinds of heat transfer models were established for a cylindrical rotational mold in the heating process before the powders inside the mold started to melt. In the first model， the air inside the mold was taken as the primary fluid phase， and the powder was the secondary fluid phase. The mixture model in the multiphase module of FLUENT software was adopted to simulate the flow and heat transfer in the mold. The second heat transfer model is a simplified model， in which the geometry and temperature gradient of the mold were ignored， and the powder and air inside the mold were assumed to mix very homogeneously. Differential equations were given on the basis of energy conservation law and then solved with the aid of the MATLAB software. These two types of heat transfer models were used to calculate the mold temperatures and internal temperatures and also compared with the experimental results. The results indicated that he simulating accuracy of the first heat transfer model was better than that of the second heat transfer model， and the computational cost of the first model was much higher than that of the second model. Considering of the variation of physical properties， the simulating accuracy of the first heat transfer model was improved remarkably. However， it is hard for the second heat transfer model could change the simulating accuracy for mold temperatures hardly， whereas the simulating accuracy of the second heat transfer model became worse for internal temperatures.
Additive
YANG Zheng, WANG Zhenhua, LU Shike, LIU Yang, FANG Xiaoming, LI Jiantong, LIU Baoying, DING Tao
Abstract (
921 )
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Zinc borate （ZB） as a synergistic flame retardant was compounded with aluminum diethylhypophosphonate （ADP） for flame?retarding nylon 6. The flame retardant properties and mechanical properties of the resultant compounds were evaluated， and their flame retardant mechanism was investigated using vertical combustion， limiting oxygen index， cone calorimetry， thermogravimetric analysis， scanning electron microscopy and Raman spectroscopy. The results indicated that the synergistic flame?retardant effect resulting from ZB and ADP was remarkable. When 1.5 % Zb and 8.5 % ADP were added into PA6， obtained composites achieved a flame?retardant level classification of UL 94 V?0 with a limi?ting oxygen index of 29.8 vol % Compared to the samples without a synergistic agent， their peak heat release rate， average heat release rate， and mass loss rate decreased by 42.7 %， 27.3 % and 32.7 %， respectively. The cone calorimetry analysis indicated that the introduction of ZB into the ADP flame retardant system not only generated a flame?retardant effect of the vapor phase， but also promoted the flame retardancy of condensed phase. This was attributed to a synergistic flame retardant mechanism， mainly based on the gas?phase flame retardancy together with the condensed?phase flame retardancy
WANG Yazhen, LIU Xinyu, DONG Shaobo, LAN Tianyu, ZU Liwu
Abstract (
689 )
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Corn stalk （CS） was used as a raw material to prepare biochar， and then the PE?HD/corn stalkr biochar （CSB） composites was prepared through melt extrusion. The compatibilizing effect of maleic anhydride （MA） on the performance of the PE?HD/CSB composites was investigated. The prepared CSB and the resultant composites were characterized using scanning electron microscopy， thermal weight analysis， Fourier?transform infrared spectroscopy， rotational rheometer （DHR?2）， X?ray photoelectron spectroscopy. The interface properties of CS and CSB with PE?HD were evaluated using the Harmonic?Mean interface equations. The results indicated that compared to CS，CSB exhibited an increase in the degree of aromatization， and its interfacial tension with PE?HD was lower. The addition of MA improved the stability， compatibility， and mechanical properties of the PE?HD/CSB composites.
FENG Shan, JIANG Pingping, ZHANG Pingbo, ZHANG Zheming, ZHANG Kai, GU Qian
Abstract (
858 )
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Using terephthalic acid and 2?propylheptanol as raw materials， isopropyl titanate as a catalyst， bis（2?propylheptyl） terephthalate （DPHTP） were obtained by esterification. And using DPHTP as a plasticizer to prepare polyvinyl chloride （PVC） flexible film， and compare the application performance with the common DOP and DOTP on the market. The molecular structure of plasticizer was verified by FTIR and 1H?NMR. The differences in mechanical properties of DPHTP， DOP and DOTP plasticized PVC films are compared by TGA， tensile test， migration resistance test and volatility resistance test. The results show that， compared with DOP and DOTP， DPHTP plasticized film has better thermal stability and higher volume resistivity. Respectively， the volume resistivity of DPHTP plasticized film is 6.5×109， the 5 % thermal weight loss temperature is 272 ℃， the heating loss of DPHTP is 0.031 90 %. The conclusion shows that DPHTP has lower volatility and can endow PVC materials with excellent electrical insulation properties， and it was predicted to have broad development prospects in packaging materials and wire and cable industries.
Standard and Test
WANG Xiaodong, HUA Lei, DONG Aijuan, LUO Lihua
Abstract (
961 )
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902
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According to the decomposition equation of the first stage of azodicarbon amide（ADC） thermal decomposition in the temperature range of 200 ~ 240 ℃， the functional relationship between ADC decomposition process and gas generation process was established， and the thermal weight loss curve of ADC was transformed into TG gas?generation curve. The results indicated that by comparing the TG gas?generation curve of foaming agent ADC and the gas?generation curve measured by the drainage gas?gathering method， the data of starting temperature， maximum gas?generation?rate temperature， and ending gas?generation temperature of ADC measured by the two methods were very close with each other. The comparison adjusted R?squares between the two curves and the fitting curve were 0.993 7 and 0.915 43， respectively， In the first stage of ADC thermal decomposition， the TG gas?generation curve of ADC can be calculated using a TG gas?generation curve formula， which can replace the gas?generation curve measured by traditional drainage gas?gathering methods.
WANG Zhenchao, ZHANG Ying, PENG Yijuan, YU Xi, ZHANG Qiuju
Abstract (
790 )
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This manuscript first introduces the main methods for reliability evaluation of polyethylene pipe butt?fused joints in terms of short?term mechanical performance and long?term slow crack growth resistance capability. In recent years， phased?array ultrasonic have been widely used in non?destructive testing of the reliability of welded joints. Its testing automation and intelligent qualification technologies have become a mainstream research direction. At present， there are few tests on the reliability of welded joints in Chinese standards. In order to make polyethylene pressure?bearing pipelines developed in the direction of thick?walled， large?diameter， high?pressure resistance， extreme temperature application， long service life， and more safe， the reliability assessment of welded joints is required. The complete testing methods and package including accelerated testing， use of smaller samples instead of pipeline samples are hoped to be established. Finally， expect to see the new technologies used to transfer the characters of material to fused joints to facilitate the development of pipes application together with materials innovation.
Machinery and Mould
LI Xiang, WANG Dongyang, ZHU Xiangzhe
Abstract (
516 )
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369
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Based on the discrete element method， the solid conveying behaviors of a three?screw and a twin?screw extru?der were simulated respectively， and the particle movement trajectory， velocity distribution， and force distribution of the three?screw extruder were analyzed. The particles， filling efficiency， conveying quality and mass flow rates of the three?screw and twin?screw extruder were investigated comparatively. The results indicated that the particles located near the screw edge and barrel were greatly affected by the screw edge thrust and friction force of the barrel along with a higher speed. The filling sequence of particles in each area of the extruder was influenced by the direction of the screw rotation. The particles located in the meshing zone were affected by the spiral edge of the other side of the screw， which reduced the tendency of relative sliding between the particles and therefore improved the conveying capacity of the particles. There are more meshing areas on the three?screw extruder， so its filling efficiency is higher than that of the twin?screw extruder. As the rotation speed increases， the mass flow rates of the two extruders were improved significantly. Meanwhile， the mass flow rate of the three?screw extruder is about 25 % higher than that of the twin?screw extruder.
ZHANG Weihe, FENG Guoshu, ZHU Xiaoming, WU Zichun, YE Mingshan, DU Hai, SONG Dongyang, WANG Jing
Abstract (
998 )
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In this work， we designed a large and thin?walled injection mold with a sequential valve hot runner. The advanced and reasonable mold gating system was determined using the analysis of mold flow. The difficult problem from demolding plastic parts was successfully solved using a side core?pulling structure with a configuration of ′inclined top+inclined top rod′ and ′oil cylinder+shovel base+slider′. The labor productivity increased by about 10 % by using the conformal cooling channels. The first shoot was successful and the precision of the plastic parts met the requirements of mold design.
Review
AN Ying, LIU Yuliang, TAN Jing, YANG Weiming, YAN Hua, LI Haoyi
Abstract (
982 )
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The working principle of centrifugal electrostatic spinning technology was briefly described， and the recent research progress of centrifugal electrostatic spinning at home and abroad was reviewed. The fiber formation mechanism of centrifugal electrostatic spinning was summarized， and the centrifugal electrostatic spinning was divided into two categories according to the characteristics of spinning materials： solution centrifugal electrostatic spinning and melt centrifugal electrostatic spinning. The device and process innovations of these two types of spinning methods were classified， and the structural characteristics and advantages and disadvantages of various devices were summarized. Furthermore， their process parameters were analyzed. Finally， the applications of centrifugal electrostatic spinning of micro and nano fibers were briefly described， and the problems in centrifugal electrostatic spinning and the future development trend were analyzed.
LIU Jincheng, CHEN Qian, LIU Yupei, GAO Meng, ZHAO Xianhui
Abstract (
1553 )
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The synthesis methods of methyl methacrylate （MMA） were summarized， including acetone cyanohydrin， isobutylene， and ethylene methods， and their advantages and disadvantages were analyzed. A toxic raw material， HCN， was used in the acetone cyanohydrin method， generating a lot of waste. This does not meet the requirements of green production and therefore faces to be eliminated gradually. The production process of isobutylene and ethylene is green and clean in accord with the national conditions and strategic requirement of China. This has been considered as a main development direction in the future. In addition， the palladium?based catalysts and gold?based catalysts used in the production of MMA by the isobutylene method were also analyzed.
ZHANG Wei, CHEN Jie, LI Chenying, HU Libin, TAN Xiao, CAO Jingying
Abstract (
671 )
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This paper introduced the applications of halogen?free polyolefin cable materials， including several main polyolefin matrix materials， combustion characteristics， flame retardant mechanism， classification， applications characteristics， and current development direction.
