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2012, Volume 26 Issue 06 Publication date: 26 June 2012 Previous Issue Next Issue

Research Progress in Preparing Methods of PVA/MMT Nano-composites

Qingqing JIA TIAN Huafeng Aimin XIANG

2012, 26 (06): 1-8 ; DOI: 10.19491/j.issn.1001-9278.2012.06.001

Abstract ( 1313 )

The preparing methods of poly(vinyl alcohol)/montmorillonite （MMT） nanocomposites were introduced, including the insitu polymerization intercalation, the solutionintercalation and the meltintercalation. MMT extended the path of gas molecules, limited the free volume of PVA molecules, and reduced the swelling and movement of PVA molecules, which promoted the water resistance, thermal stability, gas barrier property and mechanical properties of PVA/MMT composites. MMT in PVA matrix with the form of intercalated and exfoliated type, exfoliated type material had the better mechanics performance, while the intercalated type material had the better thermal stability and gas barrier property. In PVA matrix, sodium based MMT performed the better intercalating efficiency than organic modified MMT.

Research Progress in Factors Influencing Photoaging of Polypropylene

WANG Sibei JIN Yan KANG Peng WANG Jun JIANG Lu

2012, 26 (06): 9-15 ; DOI: 10.19491/j.issn.1001-9278.2012.06.002

Abstract ( 1740 )

The research progress in photoaging of polypropylene was reviewed. The effects of a series of factors in the photoaging of polypropylene, including radiation conditions, components, stress as well as crystallinity and processing methods, were discussed.

Research Progress in PTC Characteristics of Epoxy Resin-based Conductive Composites

2012, 26 (06): 16-21 ; DOI: 10.19491/j.issn.1001-9278.2012.06.003

Abstract ( 1643 )

The electric conduction mechanism of polymeric materials with positive temperature coefficient (PTC) was introduced. Recent development of epoxy resin-based PTC composites at home and abroad was summarized and factors affecting the PTC characteristics of the epoxy resin-based conductive composites were analyzed, including conductive fillers, epoxy matrix, the third matrix components, curing agent, curing temperature, and processing technology. At the same time, application and development direction of these materials were discussed.

Study on Preparation and Properties of Polyurethane/Epoxy Resin Foam

Wenbo ZHANG Wenli SHE Weixing DONG Yuefang ZHANG Dezhen WU

2012, 26 (06): 22-27 ; DOI: 10.19491/j.issn.1001-9278.2012.06.004

Abstract ( 1340 )

Polyurethane/epoxy resin foam was prepared by one step method with cyclohexane and water as the foaming agent. Universal testing machine was used to test the mechanical strengths, thermo-gravimetric analysis was used to analyze thermal properties and optical microscope was used to characterize the cell structure. Effects of polyethylene glycol, epoxy resin on the apparent density, mechanical property and thermal stability of the polyurethane foam were studied. With increasing contents of polyethylene glycol, compressive and impact strength of the foam both first increased and then decreased. When contents of the polyethylene glycol were 30 phr, both compressive strength and impact strength achieved the best level. Thermal stability of foam increased when added epoxy resin to the system. When epoxy resin were 15~20 phr, the overall mechanical properties of foam were the best. Maximum compressive and impact strength were obtained when the cyclohexane/water was 10/1.

Study on Properties of Hydrophobic Zinc Borate and Magnesium Hydroxide Synergistically Flameretarded EVA

QU Hongqiang

2012, 26 (06): 28-33 ; DOI: 10.19491/j.issn.1001-9278.2012.06.005

Abstract ( 1519 )

Hydrophobic zinc borate (Zn2B6O11·3H2O) was prepared via a onestep wet synthesis from zinc sulfate and sodium borate, with oleic acid as the surfactant. The morphology and hydrophobic property of the products were analyzed by means of Xray diffraction, Fourier transform infrared spectroscopy, contact angle analyzer, and scanning electron microscope. It indicated that the diameter and thickness of the products were 1～2 μm and 0.1 μm, respectively; the water contact angle was 105.1 °. The prepared hydrophobic zinc borate was introduced into EVA/Mg(OH)2 composites as a flame retardant. A synergetic effect was observed, the value of limited oxygen index reached 38.5 %, and the mechanical properties were only moderately decreased.

Synthesis and Characterization of Polyether-based Thermoplastic Polyether Polyurehtane Elastomers

Xuping YANG Hai JIANG Wenbin YANG Hui HUANG Shangbin LI

2012, 26 (06): 34-38 ; DOI: 10.19491/j.issn.1001-9278.2012.06.006

Abstract ( 1353 )

A new thermoplastic polyurethane elastomer, with tetrahydrofuran-ethylene oxide copolyether as its soft segments, 1,3-bis(isocyanatomethy)benzene and hydroquinone bis(2-hydroxyethyl)ether its hard segments has been synthesized, to which melt-prepolymerization method was adopted. FTIR,GPC,DMA,TG and the tensile test techniques were applied to make further characterization of the TPU. It was showed that the TPU with 45 % mass fraction of hard segment exhibited excellent integrate properties in terms of mechanical properties: the tensile strength was 17.37 MPa and the elongation at break was 559 %. A typical microphase separation was observed.

Crystallization Behavior of Poly(ε-caprolactone)/ Poly(vinyl methyl) Blends

李海东 LI Hai-Dong

2012, 26 (06): 39-43 ; DOI: 10.19491/j.issn.1001-9278.2012.06.007

Abstract ( 1391 )

Poly(ε-caprolactone)(PCL)/poly(vinyl methyl)(PVME) blends were prepared via solution mixing. Differential scanning calorimetry (DSC) was used to study the compatibility of the blends，and the wide-angle X-ray diffraction(WAXD) and polarizing microscope ( PLM ) was used to study the effect of PVME on the crystalline morphology and crystal structure of the blends. It showed that there was only one Tg peak in the DSC curve of the blends, suggested that the blends was a compatible system, and the presence of PVME did not change the crystal structure of PCL.

Expandable Polystyrene Nanocomposites Prepared by Styrene/Nanoinorganic Particle by Insitu Suspension Polymerization

2012, 26 (06): 44-49 ; DOI: 10.19491/j.issn.1001-9278.2012.06.008

Abstract ( 1255 )

Based on in situ radical suspension polymerization, polystyrene nanocomposites were prepared from styrene and nanoinorganic particle. Then, hexane was added to prepare expandable polystyrene nanocomposites (EPSNC). EPSNC were characterized by means of gel permeation chromatography, thermo gravimetric analyzer, and scanning electron microscope. It showed that at a suitable content of nanoinorganic particle, the molecular weight of EPSNC had a narrower distribution, the thermal stability of EPSNC was improved significantly. In addition, the nanoinorganic particle showed a nucleatio

Melt Grafting of Polypropylene with Maleic Anhydride Assisted by Styrene/Divinylbenzene

ZHU Baodong Jian WANG Hongling LI Weichao DONG Qun DONG

2012, 26 (06): 50-56 ; DOI: 10.19491/j.issn.1001-9278.2012.06.009

Abstract ( 1366 )

Maleic anhydride (MAH), styrene (St), divinylbenzene (DVB), and an initiator (DCP) were embedded into polypropylene (PP) via liquid-solid swelling process. The effect of the co-monomers on the melt grafting of maleic anhydride (MAH) onto PP backbone was studied. Structure and properties of grafts were analyzed using Fourier transform infrared spectroscopy, thermo gravimetric, and water contact angle. At the same time, the mechanism of grafting reaction was discussed. It showed that the grafting ratio of MAH and gel content of grafted products were 2.25 % and 1.56 % respectively when St was used alone. However, when DVB was used alone, these values increased to 3.06 % and 46.31 %, the thermal stability and polarity of grafts were improved in different degrees. Through analyzing the mechanism of grafting reaction, it indicated that the PP macro-radicals were first reacted with the co-monomers, followed by the grafting reaction, thus depressed degradation of PP. DVB possessed two double bonds per molecule, it could be more effective in grafting and coupling between PP macro-radicals.

Effects of Aluminate Coupling Agent Modified

Feng ZHAN Nanchun CHEN Bin HUANG Shengtian LU

2012, 26 (06): 57-61 ; DOI: 10.19491/j.issn.1001-9278.2012.06.010

Abstract ( 1249 )

Diatomite was modified with aluminate coupling agent in aqueous solution which was used to prepare PVC/diatomite composites. FTIR, TG, DMA, and micro hardness tester were used to investigate and analyze the effect of the modification of diatomite on the properties of the composites. It showed that with the surface of diatomite modified, the tensile strength, non-notched impact strength, and Vickers hardness of the composites increased by 20.1 %, 4.7 %, and 23.5 %, respectively, but bending strength and modulus decreased slightly. TG showed that aluminate coupling agent had an auxiliary role of thermo-stabilization on PVC/diatomite composites. After the modification, E', E'' and tan δ of composites were reduced and then increased with increasing temperature, and glass transition temperature increased by 1.77 ℃.

Combined Analysis of Rheological Properties and PVT Relationships of Polypropylene for Injection Molding

SUN Jin

2012, 26 (06): 62-66 ; DOI: 10.19491/j.issn.1001-9278.2012.06.011

Abstract ( 1760 )

The rheological properties and pressure-volume-temperature（PVT） relationships of polypropylene(PP) were studied using seven-parameter-Cross-WLF viscosity model and modified two-domain Tait state equation. Under defined molding conditions, the whole injection molding process could be described. The theoretical volumetric shrinkage of PP was calculated to be 5.58 %, which was approximate to the practical measured value of 5.46%.

Influence of Reactive Flame Laminable Additive on Flame Laminable Properties of Polyether Flexible Polyurethane Foams

LI Dongqiang LI Yan ZHANG Ruixin WANG Jianrong

2012, 26 (06): 67-70 ; DOI: 10.19491/j.issn.1001-9278.2012.06.012

Abstract ( 1417 )

Flame laminable additive, flame retardant, and polyester polyol were added to polyether flame bonding foam to improve the bonding strength and flame laminable properties. The mechanism of flame lamination was also investigated. The research showed that the reactive flame laminable additives provided excellent adhesion properties and bond strengths with no negative influences on the other physical and mechanical properties. It was also found that the types of additives and fabrics, flame intensity, TDI index had impact on the peeling strength.

Comparison Research on Residual Wall Thickness of Water-assisted and Gas-assisted Injection Molded Parts

CHEN Yinglong ZHOU Hua ZHANG Zengmeng KONG Huzi

2012, 26 (06): 71-75 ; DOI: 10.19491/j.issn.1001-9278.2012.06.013

Abstract ( 1470 )

In this paper, the characteristics of water and gasassisted injection molding technologies were analyzed. The formation mechanism and sizes of residual wall thickness of water and gasassisted injection molded parts were proposed based a plenty of experiments. It showed that the wall thickness of waterassisted injection molded parts was more uniform compared with that of gasassisted, which was produced by the mold with deflection runner. Waterassisted injection molding technology was more suitable for the parts with circle sections.

Study on Water Resistance of Polypropylene/Sisal Fiber Wood-plastic Composites

2012, 26 (06): 76-80 ; DOI: 10.19491/j.issn.1001-9278.2012.06.014

Abstract ( 1158 )

The PP/SF wood-plastic composites were prepared through masticating and melt-compounding. The effect of water immersion of SF on the mechanical properties, thermal properties and micro-structure of the wood-plastic composites was studied. When the SF content was 50 %, water immersion time was 8 d, the impact and flexural strengths of the wood-plastic composites decreased sharply, decreased by 33.74 % and 51.42 %, from 9.88 kJ/m2 and 21.02 MPa, respectively. The thermal stability of composites, crystallization rate and degree of crystallinity of PP were also decreased. All these changes were attributed to the water molecules diffused into the wood-plastic composites.

Extrusion Foaming of DCP Slightly Cross-linked High-density Polyethylene by Supercritical CO₂

2012, 26 (06): 81-86 ; DOI: 10.19491/j.issn.1001-9278.2012.06.015

Abstract ( 1369 )

High-density polyethylene(PE-HD) was slightly cross-linked by various contents of dicumyl peroxide (DCP). The melt strength and crystallization behavior of the resultants were characterized by Rheotens and DSC. It is shown that low contents of DCP leads to the decrease of melt strength of the resultant, but increases their crystallization rates and crystallization degree; while the contents of DCP was 0.5 phr，the melt strength of the resultant reaches its highest value, 0.127 N, and lowest crystallization degree. The resultants were extrusion foamed by supercritical nitrogen, and the resultant foams were observed by SEM and a density meter. The results showed that while the contents of DCP was 0.5 phr, the PE -HD foam was endowed with the best cell morphology with the smallest cell size and lowest density of 0.5853 g/cm3.

Synergistic Effects of Phosphorus-Silicon Flame Retardant with Magnesium Hydroxide in Halogen-free Flame Retarded EVA

YANG Li

2012, 26 (06): 87-90 ; DOI: 10.19491/j.issn.1001-9278.2012.06.016

Abstract ( 1451 )

A phosphorus-silicon flame retardant (EMPZR) and magnesium hydroxide [Mg(OH)2] was introduced into ethylene-vinyl acetate copolymers (EVA) as a composite flame retardant . It was found that the flame retardancy of the copolymer exhibited the best flame retardant performance when the content of the composite flame retardant [EMPZR: Mg(OH)2 =1:4] was 50 wt %, the limiting oxygen index reached 36.0 %. TGA showed that the char yield was 32.2 % at 600 ?C. The thermal mass loss rate of the composite decreased compared with neat EVA. All these suggested that there was a good synergistic effect between EMPZR and Mg(OH)2.

Study on Synthesis and Application of Organic Intumescent N/P Flame Retardants

LI Yuntao GUO Dandan HE Jing LIU Pei XUE Rong

2012, 26 (06): 91-95 ; DOI: 10.19491/j.issn.1001-9278.2012.06.017

Abstract ( 1360 )

An intumescent flame retardant was synthesized from phosphorus oxychloride, bisphenol A, and melamine via two steps. The suitable synthesis conditions were found as follows: in the first step, the molar ratio of phosphorus oxychloride/bisphenol A was 2.2, the reaction temperature was 70 ℃, and the reaction time was 5 h; in the second step, the molar ratio of intermediate product/melamine was 1/2，the reaction temperature was 100 ℃, and the reaction time was 3 h；the yield of the products reached 87.6 %. When 15 % intumescent flame retardant with 5 % ammonium polyphosphate were introduced into polypropylene, the obtained oxygen index was 33 %, and the vertical combustion performance reached V-0 level.

Analysis of Design Stress of Standards of Plastics Piping Systems for Hot and Cold Water Installations

2012, 26 (06): 96-102; DOI: 10.19491/j.issn.1001-9278.2012.06.018

Abstract ( 1152 )

The stress calculation method used in the international standards for plastic pressure piping systems for hot and cold water installation was introduced. Based on the calculation of the design stress for hot and cold water installation, the broken contribution probability for different materials was compared. The calculation examples showed that the formula used in the international standard were questionable. Further study in this field was necessary.

Determination of Lead and Chromium in ABS Using Microwave Digestion-atomic Absorption Spectrum

XUE Yan-Bo

2012, 26 (06): 103-106 ; DOI: 10.19491/j.issn.1001-9278.2012.06.019

Abstract ( 1507 )

A method was proposed to analyze the quantity of the lead and chromium in acrylonitrile-butadiene-styrene copolymer (ABS) using microwave digestion and atomic absorption spectrum. The pretreatment was optimized including temperature, digestion procedure and proportion of acids, in order to digest the materials completely. It was found that the detection limits for Pb and Cr were 0.03 and 0.02 mg/kg, respectively. The relative standard deviations for Pb and Cr were all less than 7 % and the recovery was between 93 % and 103 %.

Comparison of Mixing Performance of Three-screw Extruders with Twin-screw Extruders

PANG Junjian HE Yadong XIN Chunling YU Dongquan LI Qingchun

2012, 26 (06): 107-111 ; DOI: 10.19491/j.issn.1001-9278.2012.06.020

Abstract ( 1374 )

Mixing performance of triangle arrayed threescrew extruder and twinscrew extruder was compared using Polyflow. Threedimensional isothermal flow in the extruders was simulated through tracer particles method. Through statistical treatment of numerical results, mixing performance was characterized in terms of mixing index, area stretch, and the residence time distribution. Subsequently, experiments were carried out with the same condition as the simulation. It showed that the experimental data were in good agreement with the simulated results.

Effect of Wall Slipping and Microscale Effect on Micro-extrusion

FU Zhihong LUO Xintao

2012, 26 (06): 112-116 ; DOI: 10.19491/j.issn.1001-9278.2012.06.021

Abstract ( 1067 )

Micro-scale effect and wall slipping mechanism of polymer in microchannels were studied and analyzed using on Polyflow software. The effect of viscosity and wall slipping on polymer flow in microchannels was analyzed based on different boundary conditions. The effect of length of compressive section on deformation of the products was studied. It showed that with wall slipping, the resistances at flow of polymer melt decreased, velocity distribution became more uniform, and the deformation of the products reduced.

Design of Injection Mould for Two-component Cover of MP4 Player

Tangqing KUANG Zhi Yan Wei Fu

2012, 26 (06): 117-122 ; DOI: 10.19491/j.issn.1001-9278.2012.06.022

Abstract ( 1300 )

According to the coated structure of a two-component cover of a MP4, two-component injection molding machine with rotary plane was adopted to molding it. The runner system was a combination of hot runner and cold runner. Latent gate and fan gate were adopted to molding the inner part and outer part respectively. Based on the flow analysis of Moldflow, the gate location was optimized firstly, and then the fill pattern, air trap distribution, injection pressure, clamp force and the time of ejection were predicted. These results were helpful for the design of the mold structure and the choice of the injection machine. Finally, the structure and working process of the two-component injection mould were introduced in detail.