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2012, Volume 26 Issue 12 Publication date: 26 December 2012 Previous Issue Next Issue

Progress of Electrical Property in Polymer/Carbon Nanotube Composites

AN Chuantao, XIN Fei, XU Zhiguo

2012, 26 (12): 1-7; DOI: 10.19491/j.issn.1001-9278.2012.12.001

Abstract ( 557 ) PDF (0 KB)( 130 )

The  research  work  on  the  flame  retartant  behavior  of polymer/carbon  nanotuhes(covalently and non-covalently modified) composites was reviewed.  The heat release rate, mass loss rate, time to ignition, limiting oxygen index, and UL94 of the composites were discussed. The key points which need further study and directions for future work were given in conclusion remarks.





Research Progress in Total Biodegradable Starch Plastics

XIA Peng, XU Yalei, HOU Lianlong

2012, 26 (12): 8-13; DOI: 10.19491/j.issn.1001-9278.2012.12.002

Abstract ( 491 ) PDF (0 KB)( 143 )

This paper introduces the research of biodegradable plastics, especially totally biodegradable starch plastics including thermoplastic starch plastics, starch/biodegradable polymer blends, and starch/natural polymer blends. It focused on the principle and advantage of thermoplastic starch plastics as well as the selection and matching of plasticizer, the properties of the starch based blends with PBS, PVA, PCL, PLA, cellulose, lignin, and protein. The current challenge of total biodegradable starch plastics was analyzed. The prospect of total biodegradable starch plastics was given.

Research Progress in Toughing Modification of PVC

2012, 26 (12): 14-18; DOI: 10.19491/j.issn.1001-9278.2012.12.003

Abstract ( 432 ) PDF (0 KB)( 125 )

The advance in the study of toughening modification of PVC in recent years was reviewed with the emphasis on the modification by elastomer, nano-particles, fiber, elastomer/inorganic particles, and green fillers. It was pointed out that PVC composites had broad application prospect. The challenges which need further exploring included low-cost nanocomposites, the toughening mechanism of PVC composites, the hybrid effect of different fillers and their synergetic mechanism, different varieties of WF modified PVC.

Effect of Clay on Conductivities of Poly(mxylene adipamide)/Carbon Nanotube Composites

2012, 26 (12): 19-24; DOI: 10.19491/j.issn.1001-9278.2012.12.004

Abstract ( 416 ) PDF (0 KB)( 135 )

Poly(m-xylene adipamide) (MXD6)/multiwalled carbon nanotube (MWCNT)/ organo-montmorillonite (OMMT) composites were prepared via melt mixing in a rotational rheometer. The effects of OMMT on the electrical conductivities of the composites were investigated. It was revealed that the poor miscibility between MXD6 and MWCNT led to a strong tendency of aggregation of MWCNTs, therefore sharply decreased the efficiency of the construction of conductive network. Although OMMT was electrically inert, the presence of OMMT could significantly increase the conductivities of the composites. The X-ray diffraction and Molau data revealed that the majority of OMMT was distributed in the MXD6 matrix in the state of intercalation. The morphology of the composites was observed by field emission scanning electron microscopy, showing that MWCNTs adhere to the new surface of OMMT particles during melt mixing, forming a structure with higher dimensions. As a result， the dispersion of MWCNTs in the MXD6 matrix was greatly increased, and led to improved conductivity. Therefore, OMMT-filled MXD6/MWCNT was a promising material with good electrical conductivity.

Effect of Elvaloy on Properties of PVC

2012, 26 (12): 25-28; DOI: 10.19491/j.issn.1001-9278.2012.12.005

Abstract ( 516 ) PDF (0 KB)( 88 )

Blends of ethylene-vinyl acetate-carbon monoxide terpolymer (Elvaloy)/modified poly(vinyl chloride) (PVC) were prepared in a two-roll mixer via melt blending. The effects of content of Elvaloy on transparency, cold resistance, micro-morphological structure, mechanical properties, and plasticizing temperature were studied. It showed that the transmittance of PVC/Elvaloy blends was above 76 %, and the haze was lower than 21 %. Because of the addition of Elvaloy, the low-temperature impact strength of PVC increased twice as much, elongation at break increased, and brittleness temperature and plasticizing temperature decreased more than 20 ℃ and 10 ℃, respectively. When the contents of Elvaloy were 2, Elvaloy/PVC blends exhibited only one Tg, indicating the components were compatible. With increasing contents of Elvaloy, Tg of the blends decreased.

Effect of Nucleating Agent on Crystallization Behavior of PHBV

WENG Yunxuan, WU Lizhen

2012, 26 (12): 29-34; DOI: 10.19491/j.issn.1001-9278.2012.12.006

Abstract ( 229 )

Effects of Lanthanum Hydroxid on Flame Retardancy of Intumescent Flame Retarded Polypropylene

2012, 26 (12): 35-39; DOI: 10.19491/j.issn.1001-9278.2012.12.007

Abstract ( 435 ) PDF (0 KB)( 145 )

The effect of La(OH)3 on the flame retardancy and the mechanical properties of intumescent flame retardantcontaining polypropylene composites was studied. The limiting oxygen index, UL94 test, thermogravimetric analysis, scanning electron microscopy, tensile strength, elongation at break, and impact strength were employed to investigate the synergistic effects of La(OH)3. It showed that La(OH)3 could enhance the limiting oxygen index of the composites and made the retardancy reaching UL94 V0. The limiting oxygen index of the composites with 0.5 % La(OH)3 achieved 33.0 %. And La(OH)3 contributed to the formation of a compact char layer on the surface of the composites and increased the amount of the char residue. It could be speculated that the La(OH)3 reacted with intumescent flame retardant and caused the crosslinking of the composites, which increased the viscosity and resulted in a more homogenous and compact structure of char. And a suitable amount of La(OH)3 could also benefit the mechanical properties of the composites.

Study on Non-isothermal Crystallization Kinetics of PE-LLD/Nano-Al₂O₃ Composites

2012, 26 (12): 40-44; DOI: 10.19491/j.issn.1001-9278.2012.12.008

Abstract ( 1433 )

Non-isothermal crystallization behavior of linear low density polyethylene (PE-LLD)/nano-Al2O3 composites was investigated using differential scanning calorimetry. The non-isothermal crystallization kinetics was analyzed with Avrami and Mo methods. Kissinger method was used to estimate the activation energy for non-isothermal crystallization. When the content of nano-Al2O3 was between 5 % and 10 %, the heterogeneous nucleation in the crystallization process of PE-LLD was sufficient, the crystallization onset temperature, peak temperature, and crystallization rate increased only slightly. The addition of nano-Al2O3 decreased the activation energy of PE-LLD.

Flame Retardancy of Intumescent Flame Retarded Polypropylene Composites Based on Acrylic Resin as a Compatibilizer

2012, 26 (12): 45-50; DOI: 10.19491/j.issn.1001-9278.2012.12.009

Abstract ( 467 ) PDF (0 KB)( 147 )

A composite of polypropylene (PP) with pentaerytheritol phosphate ester melamine resin salt (PPEMR) with acrylic resin as a compatibilizer was prepared and its fire-retardant behavior was investigated. Rheological testing and scanning electron microscopy observation indicated that when the content of AR was between 2.5 phr and 3.75 phr, the melt viscosity of the composite was the highest. During burning, a foam char layer was formed.Thermal analysis and infrared spectra showed that carboxylic acid group of AR reacted with the -NH2 of PPEMR, which retarded the degradation and leaded to a comparatively thermal stabilization of the composite. The higher the melt viscosity, the easier the formation of the foam char layer. Thermal analysis curve assumed that the heat release process was delayed, and the heat release temperature range was broadened.

Influence of Microwave Irradiation on Properties of PP/Nano-TiO2 Composites

2012, 26 (12): 51-56; DOI: 10.19491/j.issn.1001-9278.2012.12.010

Abstract ( 233 ) PDF (0 KB)( 78 )

In this paper, PP/nano-TiO2 composites were prepared via melt blending, the properties of the composites were analyzed by means of mechanical tests, infrared spectroscopy, POM, SEM, and TEM, and then the influence of microwave irradiation on the properties of PP/nano-TiO2 composites was studied. It showed that after the PP master-batch was irradiated by microwave, the elongation at break greatly improved without decreasing the tensile and yield strengths, the degree of crystallinity increased by nearly 20 %, the crystal grain size increased, and crystallization rate had no changes. Infrared spectrum showed that some polar groups were brought into PP/nano-TiO2 composite; thereby the compatibility between the two-phases was improved, which was considered the reason for the improvement of the properties.

Preparation and Properties of PS/Nano-TiO2/SEBS Composites

2012, 26 (12): 57-61; DOI: 10.19491/j.issn.1001-9278.2012.12.011

Abstract ( 383 ) PDF (0 KB)( 162 )

Polystyrene/nano-TiO2/hydrogenated styrene-ethylene-butylene-styrene copolymer composites were prepared via melt blending. The effects of amount of nano-TiO2 and SEBS on the mechanical properties, torque ternary and thermal properties of polystyrene were studied. The impact fracture microstructure of composites was observed using SEM. With increasing content of SEBS, the impact strength of polystyrene/nano-TiO2 composites increased and the tensile strength decreased. When the content of SEBS was 8 phr and the weight ratio of PS and nano-TiO2 was 97∶3, the mechanical properties were the best. The impact strength of the ternary composites was 5.626 kJ/m2, and the tensile strength was 25.623 MPa. Thermal performance of the ternary composites was increased by the addition of nano-TiO2 and SEBS. The maximum torque of the ternary composites decreased by 17 N·m compared with PS with an average torque being 7 N·m. The particles of SEBS embedded in the matrix resulted in a typical ductile fracture.

Non-isothermal Crystallization Kinetics of Glass Fiber Reinforced Polypropylene

2012, 26 (12): 62-65; DOI: 10.19491/j.issn.1001-9278.2012.12.012

Abstract ( 376 ) PDF (0 KB)( 135 )

The influence of glass fiber content and length on non-isothermal crystallization behavior of PP was investigated. The crystalline morphology was examined using polarized optical microscope. It showed that the glass fibers provided nucleating sites for crystallization. With increasing glass fiber content, the crystallization rate increased gradually and t1/2 decreased. As the length of glass fiber increased, the crystallization rate increased first and then decreased. The Avrami exponent was in the range of 2.99~3.40, which implied the nucleation mechanism and geometry of crystal growth of PP was not changed.

Temperature Profile of Polypropylene during Cooling Stage in Gas-assisted Injection Molding

2012, 26 (12): 66-71; DOI: 10.19491/j.issn.1001-9278.2012.12.013

Abstract ( 414 ) PDF (0 KB)( 130 )

Under reasonable assumptions, the theoretical and experimental temperature distribution of polypropylene (PP) during the cooling stage in gas-assisted injection molding (GAIM) was studied via the numerical simulation coupled with experimental measurement. It showed that the cooling rate of PP was significantly increased after an injection of N2, and a small “crystallization platform” near the gas-melt interface was observed. The mathematic model was solved through the mathematical software package MATLAB and measurements of temperature profiles of PP and N2 showed good agreement with the numerical prediction during the liquid cooling process. During the solid cooling stage, the values of theoretical predictions of PP were larger than the experimental ones, while the values of theoretical predictions of N2 were lower than the experimental ones.

Effect of Supercritical Carbon Dioxide on Extrusion Foaming for PLA

2012, 26 (12): 72-75; DOI: 10.19491/j.issn.1001-9278.2012.12.014

Abstract ( 380 ) PDF (0 KB)( 121 )

In this paper, a co-rotating twin screw extruder connected with a melt pump was employed to carry out the extrusion foaming of a semi-crystalline PLA. The effect of CO2 concentration on PLA foam density, cell density, and cell diameter was investigated. With 7 % to 10 % CO2, PLA foam with low density of 40 kg/m3，small cell diameter of 285 μm, and high cell density of 1.5×106/cm3 was obtained. With increasing CO2 content, the initial crystallization peak of PLA foam decreased and the degree of crystallization increased, indicating that the supercritical CO2 promoted the crystallization of PLA in the extrusion foaming process.

Effect of Oriented Drawing on Properties and Structure of BaSO₄ Filled PTFE Composites

2012, 26 (12): 76-80; DOI: 10.19491/j.issn.1001-9278.2012.12.015

Abstract ( 529 ) PDF (0 KB)( 129 )

Polytetrafluoroethylene (PTFE) sealing materials filled with BaSO4 were prepared via molding and sintering process. Effect of drawing ratio on the density, compressibility, and resilience were investigated. The melt crystallization behavior and crystallite structure were studied using DSC and XRD. Experimental results show that the density of PTFE/BaSO4 composites decreased, compressibility increased, while the resilience decreased, the overall compression recovery increased. Also with increasing draw ratio, the melt crystallization behavior of PTFE was little influenced, but the crystallinity increased after a first decrease.

echnology of Reverse Deformation and Warpage Analysis of Rear Automotive Lamp Shell

2012, 26 (12): 81-86; DOI: 10.19491/j.issn.1001-9278.2012.12.016

Abstract ( 457 ) PDF (0 KB)( 123 )

Based on the CAE mold flow analysis techniques，a numerical simulation of injection molding analysis and a on-site tracking measurement were carried out on the rear automotive lamp shell. It was concluded that the simulation results of residual warpage deformation were basically consistent with the measured values with errors less than 50 %. On the basic of the numerical simulation model，combined with the scheme of reverse deformation，the optimum analysis of the reverse deformation was conducted with numerical simulation model，an optimum scheme was obtained. Compared with the injection without reverse deformation，the optimum scheme could reduce the warpage deformation about 90 %. The technology of reverse deformation provided reliable theoretical references for the warpage controlling of injection molding，the choices of mold and process design, and the determination of the pre-set deformation.

Study on Mechanical Property and Non-isothermal Crystallization Kinetics of High Relative Molecular Mass Nucleating Agent Modified Polypropylene

2012, 26 (12): 87-92; DOI: 10.19491/j.issn.1001-9278.2012.12.017

Abstract ( 456 ) PDF (0 KB)( 125 )

Non-isot hermal crystallization behavior of polypropylene and high relative molecular mass nucleating agent(PNA) modified polypropylene was studied using differential scanning calorimet ry (DSC) with the data analyzed with Jeziorny method.Mechanical property of polypropylene and PNA modified polypropylene was studied using electronic universal testing machines. It showed that PNA increased the crystallization rate of PP , indicated by decreased t1/ 2 and increased Zc . t1/ 2 of polypropylene with 0.3 phr PNA decreased to 64.9 % than t1/ 2 of polypropylene. n of polypropylene decreased with cooling rate increased , and n of PNA modified polypropylene increased with cooling rate increased, tensile strength and impact strength of PNA modified polypropylene were higher than polyprolylene.

Research Progress in Surface Modification of Ammonium Polyphosphate

2012, 26 (12): 93-97; DOI: 10.19491/j.issn.1001-9278.2012.12.018

Abstract ( 471 ) PDF (0 KB)( 159 )

The research work on the surface modification of inorganic flame retardant ammonium polyphosphate (APP) was summarized. Through surface modification and microencapsulation of APP, the hydrophobicity of APP was increased, the water-solubility and hydrolysis of APP in water were decreased. The surface modification also increased the compatibility of APP and polymer matrix decreased the damage of APP addition on the mechanical properties and processing performance.

Preparation and Characterization of Tin Compounds Nucleating Agent Polypropylene

2012, 26 (12): 98-102; DOI: 10.19491/j.issn.1001-9278.2012.12.019

Abstract ( 506 ) PDF (0 KB)( 120 )

Two noval nucleating agents SnB4 and SnD4 (stannic chloride, benzoic acid and p-tert-butyl benzoic acid) were prepared and employed in isotactic polypropylene (iPP). The iPP samples were studied using X-ray diffraction analysis, differential scanning calorimetry, and polarized light microscopy. The mechanical properties and Vicat softening temperature of iPP were also tested. It was found that the two nucleating agent improved the crystallinity and crystallization rate of iPP. Mechanical properties of the iPP were also somewhat improved, especially when SnD4 was used.

Research Progress in Grooved Barrel Single Screw Extruders

2012, 26 (12): 103-110; DOI: 10.19491/j.issn.1001-9278.2012.12.020

Abstract ( 488 ) PDF (0 KB)( 118 )

The structure，transmission mechanism，and industrial application of axial and spiral grooved barrel single screw extruders were analyzed and compared. Since the current melting scheme did not meet the requirements for the high output of these extruders, some solutions were analyzed in order to enhance the melting ability. The development trend of the grooved barrel single screw extruders was forecast.

Design of Injection Mould with Hot Runner for Face Recognizing Machine Cover

2012, 26 (12): 111-116; DOI: 10.19491/j.issn.1001-9278.2012.12.021

Abstract ( 419 ) PDF (0 KB)( 127 )

In this paper, the molding technology of face recognizing machine cover was analyzed and the design of a hot runner injection mold for this part was introduced. At first, Moldflow software was employed to analyze the flow in the mold, the optimal gate locations and number were determined. Subsequently the structure and size of the hot runner were designed through comparing with cold runner system. Besides, based on Moldflow analysis, an inverse-moving mold structure and a distance parting mechanism were designed to meet the requirements of molding precision, with the antidirection pushing-out realized. At last, the total mold assembling drawing was finished.