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2011, Volume 25 Issue 02 Publication date: 26 February 2011 Previous Issue Next Issue

Research Progress in Modification Methods of Polyimide Pervaporation Membranes

2011, 25 (02): 7-12 ; DOI: 10.19491/j.issn.1001-9278.2011.02.002

Abstract ( 1806 )

The recent research progress in modification methods of polyimide pervaporation membranes was reviewed. Five methods were discussed including copolymerization (main chains and side groups), filling (inorganic and organic), crosslinking, blending, and surface modification. The mechanism of reaction, designing methods, and influence on separation performance and structure of polyimide pervaporation membranes were analyzed. The advantages and disadvantages of these modification methods were summarized by comparing different research results. Based on the above, the foresight developments of modification methods of polyimide pervaporation membranes were also illustrated.

Research Progress in Mechanical Properties of POSS Modified Polymer Composites

Binbin FAN

2011, 25 (02): 13-18 ; DOI: 10.19491/j.issn.1001-9278.2011.02.003

Abstract ( 2336 )

Different types of polyhedral oligomeric silsesquioxane(POSS) and POSS modified polymer composites were introduced. The systems based on conventional polymers（polyolefins，epoxy resins， polyacrylates，and polyurethanes，etc）were reviewed. In the end, the development trend of POSS modified polymers were predicted.

Research Progress in Cyclic Phosphate Flame Retardant

2011, 25 (02): 19-23 ; DOI: 10.19491/j.issn.1001-9278.2011.02.004

Abstract ( 2598 )

The recent development of bispirocyclic pentaerythritol phosphate flame retardant was reviewed, including improvement in the synthetic methods, synergistic effect with other flame retardants, and the application in polypropylene, epoxy resin, and other engineering plastics and textiles. Improvement in the synthetic methods were mainly achieved by adding the catalyst and acid-binding agent resulting in reduction in temperature, reaction time, and costs. Synergistic effect of the flame retardancy was realized between bispirocyclic pentaerythritol phosphate and P-N, P-Si systems.

Preparation of PA6 Particles by Syntheses Phase Separation Method

2011, 25 (02): 24-27 ; DOI: 10.19491/j.issn.1001-9278.2011.02.005

Abstract ( 2052 )

In this paper, PA6 particles were prepared by phase separation methods by either nonsolvent or cooling. The particles by nonsolvent possessed a loose surface structure and a good dispersibility, and those by cooling gave a compact surface structure and a poor dispersibility. When prepared with a combined method of above two, the particles showed both a compact surface structure and a good dispersibility.

Study on Melting Grafted Polypropylene with High Fluidity

2011, 25 (02): 28-32 ; DOI: 10.19491/j.issn.1001-9278.2011.02.006

Abstract ( 1887 )

PP was grafted with N-phenyl maleimide(N-PMI) and diphenylmethyene bismaleimide (BMI) in order to enhance its polarity. Infrared spectrum (FTIR) confirmed the grafting. The contacting angle of DI water on samples changed from 109 o for neat PP to 97 o for 2 phr N-PMI grafted and to 99 o for 1 phr BMI grafted. At processing temperature, the phthalimide(PTI) could be dissolved into grafted PP to enhance its flow ability, and at reduced temperature, PTI was phase separated and thus to improve the heat distortion temperature and impact strength. With 2 phr N-PMI, 1 phr BMI, and 1 phr PTI, the melt flowing rate of the resultant system was 2 times higher than that of neat PP while the heat distortion temperature increased 12 ℃, impact strength and flexural strength increased 20 % and 10 % , respectively.

Investigation on Preparation and Properties of mPE/PE-LD/CB Electric Composites

Wen-Long ZHANG WU Wei-Ju

2011, 25 (02): 28-42 ; DOI: 10.19491/j.issn.1001-9278.2011.02.007

Abstract ( 1730 )

Blends of metallocene polyethylene / low-density polyethylene / carbon black (mPE/PE-LD/CB) composites were prepared in a rheometer mixer. The effect of blending temperature, speed, and other process factors on rheological properties of mPE/PE-LD/CB composite was studied and the crystallinity and morphology of the composite was studied by differential scanning calorimetry and scanning electron microscopy, while the surface resistance, volume resistance and mechanical properties of the composite were tested. When the mixer speed was 30 r/min, temperature was 180 ℃, mixing time was 10 min, the crystallinity, electrical conductivity, and mechanical properties of the composite increased with increasing mPE content.

Surface Free Energy Promotion of Poly(monochloro-p-xylylene) Film Modified via In-situ Grafting Polymerization

GAO Liude

2011, 25 (02): 33-37 ; DOI: 10.19491/j.issn.1001-9278.2011.02.008

Abstract ( 2145 )

The surface free energy of poly(monochloro-p-xylylene) film was enhanced through a surface grafting polymerization. The surface of poly(monochloro-p-xylylene) film was first activated using the sodium-naphthalene complex to induce free radicals, and the surface polymerization was initiated in a solution of the of MMA. The surface chemical composition and morphological structure of the grafted samples were characterized using Fourier transform infrared spectroscopy(FTIR), X-ray diffraction, and microscopy. The emergency of the -C=O group on the FTIR and increasing of -CH2 characteristic absorption peak of the grafted film suggested the grafting polymerization on the surface. After the modification, the surface free energy increased from 28.6 mJ/m2 to 54.1 mJ/m2 and tensile strength increased from 150.5 kPa to 222.5 kPa.

Research on the Properties of CPVC/ASA Blends

WANG Yan-fang Bao-liang XU

2011, 25 (02): 43-46 ; DOI: 10.19491/j.issn.1001-9278.2011.02.009

Abstract ( 2329 )

The mechanical and rheological properties, heat resistance, and microscopic structure of CPVC/ASA blends were studied. With increasing ASA contents, the tensile strength and heat resistance of the blends decreased, however, the cantilever notched impact strength increased, in addition reduced the balance torque in the plasticizing testing. At an ASA content of 30 phr, the impact strength was 11.18 kJ/m2，the tensile strength was 48.64 MPa, Vicat softening point was 105.4 ℃, balance torque was 21.4 N·m, which was 7 N·m lower than that of neat CPVC.

Study on the Crystallization Kinetics of Self-crosslinking Low-density Polyethylene at Room Temperature

FANG Jia-Mei

2011, 25 (02): 47-51 ; DOI: 10.19491/j.issn.1001-9278.2011.02.010

Abstract ( 1793 )

Crosslinked PE-LD was prepared through a two-step method: silane grafting and room temperature self-crosslinking. Both grafted and crosslinked PE-LD was studied using FTIR and differential scanning calorimeter. It was found that the crystallization behavior of PE-LD was greatly affected by the silane grafted reaction and self-crosslinking, the values of Avrami index of PE-LD was 2.52, while it increased to 3.8～6.0 when PE-LD was grafted or cross-linked. The values of Avrami index increased to the maximum and then decreased with increasing loading of initiator, while decreased with increasing loading of catalyst. Compared with neat PE-LD, the velocity constant of the crystallization of silane grafted PE-LD became higher, while that of cross-linked PE-LD became smaller.

Research on Non-isothermal Crystallization Kinetics of In-situ Compatibilized PA6/PE-HD Blends

2011, 25 (02): 52-59 ; DOI: 10.19491/j.issn.1001-9278.2011.02.011

Abstract ( 1742 )

The non-isothermal crystallization kinetics of in-situ compatibilized PA6/PE-HD blends was studied by means of differential scanning calorimetry(DSC). Its non-isothermal crystallization data was analyzed using Jeziorny modified Avrami equation and Mo method. It showed that the above equation and method could well describe the nonisothermal crystallization of PA6 and PA6/PE-HD blends. At primary crystallization stage, there existed both heterogeneous and homogeneous nucleations. In the secondary crystallization stage, the growth was one-dimensional mode. The addition of PE-HD played a role of heterogeneous nucleation, which promoted the growth of the nuclei. Additionally, the relationship between the activation energy of nonisothermal crystallization of PA6/PE-HD blends and temperature was obtained from Vyazovkin method.

Research on Resistivity-temperature Characteristics of PE-HD/MWCNTs and PE-HD/CB Composites

2011, 25 (02): 60-64 ; DOI: 10.19491/j.issn.1001-9278.2011.02.012

Abstract ( 2158 )

PE-HD/MWCNTs composties and PE-HD/CB composites were prepared by solution blending and ultrasonic dispersion. It was found that PE-HD/MWCNTs composites possessed lower resistivity at room temperature, higher positive temperature coefficient (PTC) intensity, and lower negative temperature coefficient (NTC) effect, when compared with PE-HD/CB composites. The analysis of the whole resistivity-temperature curve of PE-HD/MWCNTs composites illustrated that the PTC effect was resulted from both the diffusion of MWCNTs to crystalline areas and the volume expansion of the matrix; while NTC effct was caused by contacting between MWCNTs due to their thermal motion, rather than the agglomeration of particles.

Study on the Effect of Post Processing on Selective Laser Sintering PC Parts

WANG Yan

2011, 25 (02): 65-67 ; DOI: 10.19491/j.issn.1001-9278.2011.02.013

Abstract ( 2027 )

In this paper, epoxy resin (EP) was used to post processing PC selective laser sintering (SLS) parts, and the effect of post processing on the mechanical properties of PC SLS parts was studied. After the post processing by EP, PC SLS parts was changed from porous parts into full density parts and the tensile strength, tensile modulus, and impact strength of PC parts were greatly improved. The tensile strength of PC parts increased from 0.39～2.29 MPa to 40 MPa, tensile modulus increased from 2.19～17.13 MPa to around 500 MPa, impact strength increased from 0.92～3.13 kJ/m2 to around 7 kJ/m2.

Optimization of Wall Thickness Distribution of Hollow Industrial Parts by Parison Temperature Difference Method

2011, 25 (02): 68-71 ; DOI: 10.19491/j.issn.1001-9278.2011.02.014

Abstract ( 2107 )

A complicated hollow part was selected as the research object in this paper. The method of parison temperature difference was proposed for optimizing the wall thickness distribution uniformity of hollow parts according to the principles of polymer rheology. Before the blowing up of the parison, the locations on the parison that would be largely deformed was pre-cooled with air or water, and a temperature gradient was formed on the parison before the mold closed. By this method the standard deviation of the wall thickness of a fuel tank decreased from 0.7249 to 0.4475 and 0.4582, and the uniformity of the wall thickness was raised obviously.

Effect of MDI on Melt Rheological Behavior of Poly(propylene carbonate)

2011, 25 (02): 72-78 ; DOI: 10.19491/j.issn.1001-9278.2011.02.015

Abstract ( 2087 )

In this study, poly(propylene carbonate) (PPC) was chain extended with 4,4-diphenylmethylene diisocyanate（MDI）via melt reaction. On the FTIR spectra, the absorption bands observed at 1600 and 1535 cm-1 were attributed to the vibration of benzene ring and -N-H (amide Ⅱgroups), respectively, suggesting the occurrence of chain extend reaction. The dynamic rheological tests showed that MDI-modified PPC had higher storage and loss moduli and complex viscosity than unmodified PPC. Moreover, modified Cole-Cole plots revealed that the MDI-modified PPC samples possessed higher elasticity, broader molecular weight distribution, longer stress relaxation time than neat PPC.

Devulcanization of Ground Tire Rubber Through High Stress-induced Reaction and Its Effect on Mechanical Properties of PP Dynamic Vulcanized Thermoplastics Elastomer

2011, 25 (02): 79-84 ; DOI: 10.19491/j.issn.1001-9278.2011.02.016

Abstract ( 2095 )

The devulcanization reaction of ground tire rubber (GTR) through melt extrusion was studied. When alkyl phenol disulfide and/or 2-butyl alcohol were used as promoter, the gel content in GTR was decreased, content of C=C double-bond in the sol was increased. After the devulcanization at 240 ℃ and 1000 r/min, GTR was blended with PP and POE forming a thermoplastic elastomer with a tensile strength of 11.2 MPa and an elongation at break of 123.2 %.

Compound Principles of Ester-tin and Its Application Development in PVC

ZHANG Shuhua Wenjun GAN Qiang LI Bo FANG Xinyu GONG

2011, 25 (02): 85-91 ; DOI: 10.19491/j.issn.1001-9278.2011.02.017

Abstract ( 2178 )

The thermal stabilization mechanism and compound principles of ester-tin in PVC were discussed based on its structure. The mechanisms for ester-tin could inhibit the degradation of PVC including: (1) substituting unstable chloride; (2) reacting with HCl forming thiol, which may be added onto the conjugate structure of PVC. The ester-tin showed excellent synergistic effect with thiols, some antioxidants such as bisphenol a, β-diketone compounds, and HLDs, and its thermal stability was increased by composing with these compounds. The product's quality, unsafe of its production, and shortage of its thermal and toxic mechanism research, and shortage of its environmental assessment were the urgent problems to be solved in the domestic industry of ester-tin.

Thermal Property and Flame Retardancy of Hybrid of Epoxy Resin/Silicon-phosphorus Hybrid Cured Blends

LIU Weiqu

2011, 25 (02): 92-95 ; DOI: 10.19491/j.issn.1001-9278.2011.02.018

Abstract ( 1943 )

A silicon-phosphorus hybrid was synthesized thhrough the reaction between 3-glycidoxypropyl trimethoxysilane and phosphoric acid, which was used introduced into a cured epoxy system containing bisphenol-A type epoxy resin and 4,4'-diaminodiphenylmethane. Thermogravimetric analysis, differential scanning calorimetry, and limited oxygen index testing were carried out to characterize the cured products. It was found that the glass transition temperature(Tg) of the cured blends was higher than that of neat epoxy resin, and the thermal stability of the cured blends was lower at low temperature, however, the char yield at 700 ℃of the cured blends was much higher. When the content of silicon-phosphorus hybrid was 30 phr the char yield at 700 ℃ of the curd blends 34.1 %, the Tg was 169 ℃, limited oxygen index was 27.1 %, higher than those of neat epoxy resin by 77.8 %, 9 ℃ and 28 %, respectively.

Recent Advances in International Standards for Plastic Pipes

SUN Hui

2011, 25 (02): 96-103 ; DOI: 10.19491/j.issn.1001-9278.2011.02.019

Abstract ( 2320 )

The present paper briefly introduces the 20th annual meeting of technical committee 138 on plastic pipes, fittings and valves for the transport of fluid, International Organization for Standards (ISO/TC138) and summarizes the recent advances in international standards for plastics pipes as reflected during the meeting. This paper aims to provide reference information for the drafting or revising of China national standards for plastic pipes and for the development of China's plastic pipe sector, with the ambition to enable China to participate actively and effectively in the standardization of plastic pipes in the international community.

Application of Pro/E Layout in the Construction of Standard Mould Base Library of Injection Moulds

2011, 25 (02): 104-107 ; DOI: 10.19491/j.issn.1001-9278.2011.02.020

Abstract ( 2154 )

The national standards for injection mould bases were compared with the earlier editions. The way to establish standard mould base library based on layout file was mainly introduced. Firstly, the layout file and the parts library for injection mould base were established. Then the corresponding parts were declared to the layout file so that a set of mould base could be converted to a series to call easily.

Mixing Effect of Screw Configuration on the PP/PET Blends

2011, 25 (02): 108-111 ; DOI: 10.19491/j.issn.1001-9278.2011.02.021

Abstract ( 2281 )

Statistic analysis was applied on the flow field of two configurations of kneading blocks. Based on the flow field simulation of the two configurations in different rotational speeds, simulated the maximum shear rate distribution, RTD and strain distribution. Meanwhile an experiment was made to validate the analysis result. Results showed that the dispersive configuration made the tensile strength of PP/PET blend better. The diameters of PET particles affect the impact strength in the PP/PET blend. Too small diameters of PET particles made low impact strength.