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2017, Volume 31 Issue 03 Publication date: 26 March 2017 Previous Issue Next Issue

Mechanism and Development Trend of Halogen-free Flame Retardants for Polycarbonate

2017, 31 (03): 1-6 ; DOI: 10.19491/j.issn.1001-9278.2017.03.001

Abstract ( 694 )

This article summarized the characteristics and mechanisms of halogen-free flame retardants commonly used for polycarbonate (PC) resin and also discussed the developing trend of flame-retarded PC compounds. These halogen-free flame retardants could be divided into phosphate ester, sulfonic acid salts, organic silicon, inorganic filler and phosphorus nitrile, and they exhibited their own advantages and limitations. It is believed that the development of new halogen-free flame retardants as well as the combination of different halogen-free flame retardants are main pathways to meet the new requirement of flame-retardant PC products.

Progress in Research on Selective Localization of Narnoparticles in Polymer Blends

2017, 31 (03): 7-14 ; DOI: 10.19491/j.issn.1001-9278.2017.03.002

Abstract ( 790 )

The article reviewed influencing factors and control techniques of selective localization of various nanoparticles in different polymer blends, and especially introduced the selective localization of various nanoparticles like carbon black, carbon nanotubes, SiO2, montmorillonite and graphene in polymer blends. The effects of selective localization of the nanoparticles on morphology, rheological behaviors, and electrical and mechanical properties of polymer blends were also discussed.

Processability and Mechanical Properties of Poly(vinyl chloride)/Diallyl Phthalate Compounds

2017, 31 (03): 15-18 ; DOI: 10.19491/j.issn.1001-9278.2017.03.003

Abstract ( 669 )

Processability of poly(vinyl chloride) (PVC)/diallyl phthalate (DAP) resin compounds was evaluated by a torque rheometer, and the effect of DAP loading on the processing performance of the compounds was investigated. The results indicated that the compounds had excellent processing properties due to the incorporation of DAP, and the plasticizing time, balance torques, maximum torques and balance temperature of the compounds were reduced significantly with increasing DAP content. A mechanical investigation indicated that the tensile strength and elongation at break of the compounds were also enhanced.

Relationship Between Structure and Performance of Copolymerized Polypropylene with Low Melt Flow Rate

2017, 31 (03): 19-22 ; DOI: 10.19491/j.issn.1001-9278.2017.03.004

Abstract ( 957 )

A comparative investigation was conducted on three types of copolymerized polypropylene (K8303, K8003 and EPS-30R) with a low melt flow rate. The relationship of structure and performance was evaluated by means of mechanical measurement and NMR characterizations, and the crystal morphology and phase structure were observed by polarizing microscope and scanning electron microscope, respectively. The results indicated that the spherulite size and the content of rubber phase influenced the balance between the stiffness and impact toughness significantly. The spherulite sizes of K8303 and K8003 are smaller than those of EPS-30R due to their higher content of rubber phase, and thus they exhibited much higher impact toughness.

Rheological Behaviors of Polycarbonate/1,2-Propylene Glycol Modified Copolyester Alloys

2017, 31 (03): 23-27 ; DOI: 10.19491/j.issn.1001-9278.2017.03.005

Abstract ( 658 )

Polycarbonate (PC) and self-made copolyester (PPET) modified by 1,2-propylene glycol were used as raw materials to prepare PC/PPET alloys by melt blending, and their rheological behaviors were studied by a capillary extrusion rheometer. The results indicated that the rheological experiment could not be implemented in the temperature of 240~255 ℃ due to the poor fluidity of PC. However, the PC/PPET alloys exhibited a good flowing property, indicating that the addition of PPET improved the fluidity of PC and thus made it processable at lower temperatures. The PC/PPET alloys present a pseudoplastic fluid in the above temperature range, and a decrease in viscous-flow activation energy in the beginning and then tended to increase with increasing PPET content. When the mass ratio of PC/PPET was set to 4/1 and 1/4, the temperature dependency of viscosity was more significant for the alloys, and the elevation of temperature was a suitable means to enhance the fluidity of the alloys.

Effect of Antistatic Agents on Electrical Properties of Soft Poly(vinyl chloride)

2017, 31 (03): 28-34 ; DOI: 10.19491/j.issn.1001-9278.2017.03.006

Abstract ( 609 )

The soft poly(vinyl chloride) (PVC) compounds containing dioctyl phthalate were prepared by melt blending with an antistatic agent (SAS93), an antistatic agent (SN), conductive carbon black and acetylene black. The mechanical properties, volume resistance, surface resistance and morphology of these compounds were evaluated. The results indicated that the volume and surface electrical resistance was reduced to 107~108 Ω when 0.5 phr SAS93 or SN was added into PVC. The antistatic agent SN had the same effect on the stiffness of PVC compounds with SAS93, but it exhibited a more significant effect on tensile properties. On the other hand, the addition of 20 phr conductive carbon black or acetylene black into PVC led to the volume and surface electrical resistance of 107~108 Ω, which could be further reduced to 103~104 Ω with the addition of 30 phr carbon black. It was deduced that the percolation threshold of carbon black for PVC was 20 phr.

Mechanical Behaviors and Morphology Evolution of Poly(lactic acid)/Thermoplastic Polyurethane Blends

2017, 31 (03): 35-39 ; DOI: 10.19491/j.issn.1001-9278.2017.03.007

Abstract ( 649 )

A series of poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends were prepared by melt compounding with a twin-screw extruder. A universal testing machine, impact testing machine, dynamic mechanical analyzer (DMA) and scanning electron microscope (SEM) were used to test the tensile property, impact strength, dynamic thermo-mechanical property and morphology of PLA/TPU blends, respectively. The results indicated that the elongation at break, impact strength and loss modulus of PLA/TPU blends increased distinctly with increasing TPU content, and the morphology of fracture surfaces present a change from droplets to thick fibers and thin fibers. Moreover, compared with pure PLA, the elongation at break and impact strength increased by 300 % and by a factor of 13.5 for the blend containing 40 wt % TPU, respectively.

Effect of Pretreatment on Properties of Hemp-hurd-powder-filled Natural Rubber/Tyrene-butadiene Rubber Composites

2017, 31 (03): 40-45 ; DOI: 10.19491/j.issn.1001-9278.2017.03.008

Abstract ( 607 )

Hemp hurd powders (HP) were used as a type of waste biobased fillers for the preparation of natural rubber (NR)/styrene-butadiene Rubber (SBR) composites, and the surfaces of HP were pretreated by means of several different methods before being used. The effect of pretreatment on curing characteristics, morphological structure, tensile properties，dynamic mechanical properties, abrasion resistance and fatigue resistance of NR/SBR composites was investigated. The results indicated that smallsized HP had litter influence on curing characteristics. Compared with pristine NR/SBR composites, the presence of HP led to an increase in tensile strength from 3.5 MPa to 10.6 MPa and an increase in tear strength from 22.9 kN/m to 32.9 kN/m. However, HP exhibited a negative effect on the abrasion and cyclic fatigue life of the composites. The pretreatments played an important role in improving physical properties of NR/SBR composites, and furthermore, latex coagulation treatment was a better method than the coupling agent one.

Mechanical Properties, Thermal Characteristics and Crystallization Behaviors of Polyoxymethylene/Surface-modified Silica Nanocomposites Compounds

2017, 31 (03): 46-52 ; DOI: 10.19491/j.issn.1001-9278.2017.03.009

Abstract ( 644 )

Polyoxymethylene (POM)-based nanocomposites with amino-group-modified nano-silica (RNS) and methyl-group-modified nanosilica (DNS) particles were prepared through melt compounding by a twin-screw extruder, and their mechanical and thermal properties, crystallization behaviors of the resulted nanocomposites were investigated. The results indicated that the tensile strength and notched impact strength of the two nanocomposites could be enhanced at low contents of RNS and DNS, and they could be further improved with increasing contents of the two nanofillers until the maximum values were achieved. Nevertheless, the Young’s modulus presented a continual increase with increasing the nanofillers content. The incorporation of RNS improved the thermal decomposition temperature of POM significantly, whereas the introduction of DNS showed little influence on the maximum decomposition temperature of POM. Both RNS and DNS demonstrated a strong heterogeneous nucleation capability. The presence of these two nanofillers increased the crystallization temperature but reduced the crystal size of POM.

Effects of Modified Wheat Straw Powders and Their Surface Polarity on Interface of Wood-plastics Composites

2017, 31 (03): 53-57 ; DOI: 10.19491/j.issn.1001-9278.2017.03.010

Abstract ( 576 )

Wheat straw powders (WSP) were surface-modified by grafting with styrene. Contact angles were measured by a capillary rise method for the WSP before and after surface modification, and then the surface free energy was evaluated by the Washburn equation according to Owens’ method. The results indicated that the modified WSP achieved 24.77 mN·m-1 in surface free energy as well as 19.79 mN·m-1 in its nonpolar part, whereas the pristine WSP only obtained 18.90 mN·m-1 and 3.75 mN·m-1 for these two parameters. This implicates that graft modification is a useful means for nonpolarization of WSP. Moreover, SEM observation confirmed that the modified WSP had better interfacial compatibility with thermoplastics.

Optimization Design of Injection Molding Based on Neural Network and Genetic Algorithm

,

2017, 31 (03): 58-63 ; DOI: 10.19491/j.issn.1001-9278.2017.03.011

Abstract ( 631 )

To minimize the fracture of lock springs during the use，a neural network model was developed to map the complex nonlinear relationship between the processing conditions and quality indexes of the lock springs, and a genetic algorithm was used to optimize the molding process parameters on the basis of the neural network model mentioned above. The results indicated that the combination of neural network and genetic algorithm method was feasible to improve the product quality, and the residual stress decreased by 16.02 %. Moreover, the sum of packing time and cooling time was shortened by 5.4 s. This suggested that the production time was reduced, and the production efficiency was improved when the lock springs were mass produced.

Moldflow Analysis and Process Optimization for Sequentially Injection-molded Auto Front Bumpers

2017, 31 (03): 64-68 ; DOI: 10.19491/j.issn.1001-9278.2017.03.012

Abstract ( 630 )

In order to study the sequential injection molding technique for injectionmolded auto front bumpers, Moldflow software combined with pneumatic sequence valve technology was used to simulate the injection and cooling systems, and the positions of cavitation and weld line were forecasted. The sequential injection molding through 10 pin-point gates was simulated by Moldflow software. It was found that a mould locking force of more than 1820 tons and a reynolds number of 1000 were required in this injection molding technique. The auto front bumpers were produced on the basis of the above simulation optimizations. The results indicated that the sequentially injection molded auto front bumpers exhibited a good injection balance, good appearance quality and high production efficiency.

Study on Foaming Behavior of Poly(lactic acid) and Poly(butylene succinate) Blends

2017, 31 (03): 69-75 ; DOI: 10.19491/j.issn.1001-9278.2017.03.013

Abstract ( 648 )

Poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) and PLA/PBS /compatibilizer (Cp) blends were prepared by a meltmixing method, and their foam samples were produced through batch foaming. Crystallization behavior, morphology, rheological performance and foaming behavior of the blends were investigated. The results indicated that the addition of PBS had little imfluence on cooling crystallization of PLA and resulted in a slight improvement in the melt elasticity. The variation of PBS content also had little impact on bubble morphology of PLA/PBS blends. As for the PLA/PBS/Cp blends, the introduction of Cp led to a significant improvement in the crystallization behavior of PLA. The melt elasticity was also improved significantly with increasing Cp content. This suggested that the presence of Cp could effectively improve the compatibility between PLA and PBS and the bubble morphology of PLA/PBS/Cp blends.

Formation Mechanism Analysis of Melt Sink Mark Defects Inside Mold Cavity for Large Thin-wall Plastic Parts and Parameters Optimization Model of Molding Process

2017, 31 (03): 76-81 ; DOI: 10.19491/j.issn.1001-9278.2017.03.014

Abstract ( 727 )

Based on the case study of air-conditioning plane frames, sink mark formation and evolutionary mechanism in a mold cavity were analyzed. Influence of bad thermal intersection and stress along the direction of wall thickness vertical to mold cavity on the formation of sink mark were achieved, and the vertical pressure difference between the both sides of cavity wall thickness was confirmed. It was found that the greater the pressure difference, the deeper was the sink mark. The studies indicated that, with a melt temperature of 191.5 ℃, a relative pressure maintaining pressure of 85.5 %, a mold temperature of 33.6 ℃ and injection time of 2.3 s, the optimum process parameters for the air-conditioning plane frame were achieved by using genetic algorithm and the minimum shrink mark index was calculated to be 1.352. Through a comparative investigation on injection experimental results and simulation values, and the exact value of sink mark depth and the sink mark index should be set to 0~0.05 mm and 0.38 %~1.43 % under the combination of optimized process parameters, respectively.

Preparation of an Anti-aging Agent for Polypropylene by Waste Polyacrylonitrile Fabrics

2017, 31 (03): 82-89 ; DOI: 10.19491/j.issn.1001-9278.2017.03.015

Abstract ( 504 )

Hydrolyzed polyacrylonitrile (HPAN) obtained from waste polyacrylonitrile fabrics was used as a raw material to prepare HPAN-g-TiO2(KH-550) through the chemical reaction between nano-TiO2 and HPAN with the aid of γ-aminopropyl triethoxysilane (KH-550). The resultant products were characterized by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis, and then an artificially accelerated aging test was performed toward polypropylene (PP)/HPAN-g-TiO2(KH-550) and PP/TiO2 compounds by a QUV accelerated weathering tester. Furthermore, a comparative investigation was conduced in the mechanical strength and rheological properties of the compounds before and after accelerated aging tests. The results indicated that the introduction of HPAN-g-TiO2(KH-550) reduced the aging degradation of PP effectively through preventing its macromolecular chains from breaking. Meanwhile, PP could also be reinforced with the addition of HPAN-g-TiO2(KH-550), and the compound achieved 24.963 MPa in tensile strength at the PP/HPANgTiO2(KH550) weight ratio of 92/8.

Preparation of Hexahydrophthalic Acid Metal Salts and Their Application as a Nucleating Agent for Polypropylene

, ZHANG Yue-Fei,

2017, 31 (03): 90-93 ; DOI: 10.19491/j.issn.1001-9278.2017.03.016

Abstract ( 707 )

As a type of novel high-efficient nucleating agent for polypropylene (PP), a series of hexahydrophthalic acid (HHPA) metal salts was prepared by hexahydrophthalic anhydride and different metal salts. Chemical structure of the resultant products was characterized by fourier transform infrared spectroscopy (FTIR), and their effect on the crystallization and melting behaviors of PP was analyzed by differential scanning calorimetry (DSC). The moisture absorption of HHPA metal salts was also evaluated. The results indicated that HHPA metal salts could act as a highly efficient α-crystal nucleating agent for PP, and the peak crystallization temperature of nucleated PP was improved significantly when 0.3wt % of HHPA metal salt was incorporated into PP. It was also found that the sodium salt of HHPA (HHPA-Na) had the best nucleating effect, and the peak crystallization temperature of nucleated PP increased by 12.1 ℃ compared with pure PP. In addition, the HHPA metal salts exhibited a low hygroscopicity, which is advantageous for preservation of this nucleating agent and the relevant molded parts.

Screening of Degrading Strain and Its Degradation on Poly (butylenes succinate) Films

2017, 31 (03): 94-99 ; DOI: 10.19491/j.issn.1001-9278.2017.03.017

Abstract ( 530 )

A strain, LSU1601, with a degradation activity for poly(butylenes succinate) (PBS) was isolated from activated sludge. The strain was identified as Acidovorax delafiedii by thallus morphology analysis, colonies characterization, physiological reaction, biochemical reaction and 16S rDNA analysis. This strain exhibited a high production capability for PBS-degrading enzymes when the cultivation temperature was set to 30 ℃, the initial acidity was set to pH 6.8, the cultivation time was set to 48 h, and the shaking speed was set to 120 r/min. The percentage of biodegradation reached 48.2 % when the cultivatable time was 84 h, the cultivatable temperature was 30 ℃, and the initial acidity of culture medium was pH 6.8. The electron microscopic observation of the degraded PBS films showed that the film surfaces presented distinct erosion, and the erosion became more significant with an increase of degradation time. The degradation products of PBS films were assayed as 1, 4-butylene, 1, 4-succinate and butylene-succinate, but no other oligomers were found.

Design of Multi-cavity Injection Molds with Automatic Thread Demolding Function for Pen Tip Parts

2017, 31 (03): 100-103 ; DOI: 10.19491/j.issn.1001-9278.2017.03.018

Abstract ( 672 )

An injection mold was designed in the cavity layout and internal thread demolding modes for a pen tip part. The mold action consists of the thread sleeve rotation, rotation block and linear translation along the axis of part, which realized a whole internal thread in the pen tip part. Moreover, the four-columns and multi-rows layout and gear transmission were selected for this multi-cavities injection mold when designing, thus making this mold more compact. On the basis of this design idea, an injection mold with 24 cavities for the pen tip part was designed and manufactured. The practical production indicated that the assembly line has a high automation by using this mold and also exhibited a high efficiency in mass production.