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2016, Volume 30 Issue 11 Publication date: 26 November 2016 Previous Issue Next Issue

Progress in Research of Element-hybrid Flame Retardant Polystyrene

2016, 30 (11): 1-7 ; DOI: 10.19491/j.issn.1001-9278.2016.11.001

Abstract ( 533 )

The article reviewed the recent progress in the research of flame retardant effect of phosphorus, nitrogen and silicon elements and their synergistic effect on polystyrene (PS), and also introduced the element-hybrid techniques of blending, copolymerization and organic modification for flame-retardant PS. Problems in development of flame-retardant PS were summarized, and the future technique for flame-retardant PS was prospected.

Application of Hydrotalcite in Soft Poly(vinyl chloride) Compounds

2016, 30 (11): 8-12 ; DOI: 10.19491/j.issn.1001-9278.2016.11.002

Abstract ( 761 )

This article reported the effects of epoxidized soybean oil, Phosphite, βdiketone and hydrotalcite as auxiliary heat stabilizers as well as a Ca/Zn-type primary heat stabilizer on thermal stability, mechanical properties and smoke density of soft poly(vinyl chloride) (PVC) compounds. The investigating results indicated that the soft PVC achieved a long-term thermal stability and low smoke density by compounding hydrotalcite with Ca/Zn-type heat stabilizer in comparison with other auxiliary heat stabilizers.

Enhanced Radiation Crosslinking of SBS/PE-LD Blends with Multifunctional Monomers

2016, 30 (11): 13-18 ; DOI: 10.19491/j.issn.1001-9278.2016.11.003

Abstract ( 524 )

A series of compounding materials were fabricated by blending styrene butadiene copolymer (SBS) with low-density polyethylene (PE-LD) and then crosslinked by γ-ray in the presence of multifunctional monomers. The crosslinking degree, tensile strength and elongation at break of the crosslinked blends were investigated. The results indicated that multifunctional monomers exhibited an enhancement effect on the crosslinking degree of SBS/PE-LD blends. The crosslinking degree was improved with increasing content of multifunctional monomer as well as the radiation dose. In addition, the crosslinked blends exhibited a well-defined shape-memory behavior.

Analysis of Electrical Conductivity and Viscosity in Phase Inversion Process of Ester Microemulsion

2016, 30 (11): 19-24 ; DOI: 10.19491/j.issn.1001-9278.2016.11.004

Abstract ( 644 )

A series of microemulsions with various ester contents and emulsifier ratios were prepared by lauric acid polyoxyethylene esters and polyethylene oleic acid diester as emulsifiers and oleic acid ester as an oil phase, and the effect of emulsion concentration on the electrical conductivity and viscosity of the resulting microemulsions was investigated. The results indicated that these microemulsions exhibited a phaseinversion process from oil in water to water in oil with an increase of emulsion concentration. There is a correlation between the electrical conductivity and viscosity as follows: the increase of conductivity up to a stable stage corresponds to the slowly rising stage of viscosity, which results in an oil-in-water (O/W) microemulsion; the drastic decrease in conductivity corresponds to the mutation stage of viscosity, which caused the coexistence of O/W and water-in-oil (W/O) microemulsions; the gradual decrease in conductivity from a low value corresponds to the slow decline stage of viscosity, which leads to a W/O microemulsion. In addition, the viscosity of microemulsions was significantly reduced by polyether-type surfactants in the phase inversion process, and the isomeric polyether alcohol exhibited an optimum reducing effectiveness for viscosity.

Preparation and Properties of Polycaprolactone/Poly(lactic acid)/Bamboo Fiber Composites

2016, 30 (11): 25-31 ; DOI: 10.19491/j.issn.1001-9278.2016.11.005

Abstract ( 575 )

Polycaprolactone (PCL)/poly(lactic acid) (PLA)/bamboo fiber (BF) composites were prepared by compression molding. The effects of PCL/PLA mass ratio, contents of BF and silane coupling agent on mechanical properties of the composites were investigated. The results indicated that the composites achieved the maximum values of 11.26 kJ/m2, 12.68 MPa and 5.2 % in impact strength, tensile strength and elongation at break, respectively, at a PCL/PLA mass ratio of 1∶1 with 40 wt % of BF. The composites also gained the optimal values of 15.11 kJ/m2, 13.15 MPa and 5.8 % in impact strength, tensile strength and elongation at break, respectively, when BF was modified with 1.0 wt % of silane coupling agent. In addition, the composites obtained the optimal values of 15.11 kJ/m2, 13.15 MPa and 5.8 % in impact strength, tensile strength and elongation at break, respectively, when compression molding was carried out at 150 ℃.

Effect of Intercalation Conditions on Montmorillonite/Azodicarbonamide Composite Foaming Agent and Its Applications

2016, 30 (11): 32-36 ; DOI: 10.19491/j.issn.1001-9278.2016.11.006

Abstract ( 513 )

A composite foaming agent composed of montmorillonite (MMT) and azodicarbonamide (AC) was prepared by intercalating AC into MMT in supercritical CO2 medium, and then was characterized by Fourier-transform infrared spectroscopy, thermogravimetric analysis, powder X-ray diffraction and scanning electron microscopy. An optimum condition of 40 ℃, 20 MPa and 100 r/min for the supercritical intercalation was obtained on the basis of the investigation of intercalating effect and morphology of the ACintercalated MMT. The agglomeration structure of MMT was improved at this condition. The MMT/AC composite foaming agent could be directly used for the foaming process of polypropylene (PP) without any other additives. PP foams achieved a cell size of about 250 μm and a uniform size distribution at an injection molding temperature of 190 ℃.

Preparation and Flame-retardant Properties of Flame-retarded Poly(butylenes succinate) Composites

2016, 30 (11): 37-41 ; DOI: 10.19491/j.issn.1001-9278.2016.11.007

Abstract ( 618 )

Flame-retardant poly(butylene succinate) (PBS) composites were prepared by incorporating aluminum hypophosphite (AHP) and melamine cyanurate (MC) through a melt blending method, and their flame-retardant properties and thermal stabilities were evaluated by limiting oxygen index (LOI), UL 94 vertical burning test, microscale combustion calorimeter and thermogravimetric analysis (TGA). The investigation results indicated that AHP could enhance the flame retardancy of PBS significantly, and a combination of AHP with MC could further improve the nonflammability of PBS. The flame-retardant PBS composites reached a UL 94 V-0 rating with a LOI of 29 vol % when 20 wt% AHP-MC complex flame retardant was added. The TGA characterizations demonstrated that the AHP-MC complex flame retardant could increase the initial decomposition temperature and thermal stability at high temperatures effectively. Key words:poly(butylene succinate); aluminum hypophosphite; melamine cyanurate; flame retar-dant; thermal stability

Preparation and Performance of Poly(acrylic acid)/Graphene Oxide Self-healing Hydrogels

2016, 30 (11): 42-47 ; DOI: 10.19491/j.issn.1001-9278.2016.11.008

Abstract ( 935 )

In this work, graphene oxide (GO) was first prepared by an improved Hummers method, and then self-healing hydrogels based on poly(acrylic acid) (PAA) and GO were synthesized through in-situ polymerization with Fe3+ as a crosslinking agent. Effects of GO, Fe3+ and H2O contents on the swelling and mechanical properties of self-healing hydrogels were investigated, and the self-healing performance of the hydrogels was evaluated. The results indicated that the self-healing hydrogels achieved optimum mechanical properties with tensile strength of 743.5 kPa and elongation at break of 2940.5 % when Fe3+, GO and H2O contents were set to 0.5 mol%, 0.5 wt% and 80 wt%, respectively. The self-healing hydrogels obtained the maximum water absorption at the GO content of 0.25 wt%. PAA/GO hydrogels developed by this work exhibited excellent self-healing properties.

Study on Preparation and Properties of Poly(lactic acid)/Basalt Fiber Composite

2016, 30 (11): 48-52 ; DOI: 10.19491/j.issn.1001-9278.2016.11.009

Abstract ( 478 )

In order to improve the interfacial penetration and adhesion between polymeric matrix and reinforcing fiber, the composites based on poly(lactic acid) (PLA) and basalt fiber (BF) were prepared by using a needled felting method of PLA fiber and BF, followed by laminating the resulting needled felt with PLA matrix. Mechanical properties of the composites were evaluated through an orthogonal experiment in terms of several influence factors including the PLA fiber content in the needled felt, laminating pressure and laminating temperature. The results indicated that the hybrid composite technology favored the improvement of mechanical performance of the composites and the mechanical properties increased linearly with an increase of hybrid fiber content. The increase of laminating pressure was beneficial to the improvement of mechanical properties. There were different effects of laminating temperature on mechanical properties between hybrid composite technology and the traditional one. Furthermore, the excessively high laminating temperature is disadvantageous for the improvement of mechanical properties when the hybrid composite technology was employed.

Flame-retardancy of Glass-fiber-reinforced Polyamide 6 Composites with Melamine Cyanurate/Antimony Oxide/Graphene

2016, 30 (11): 53-56 ; DOI: 10.19491/j.issn.1001-9278.2016.11.010

Abstract ( 386 )

This article reported the flame-retardant effect of melamine cyanurate (MCA)/antimony oxide (Sb2O3)/graphene on glass-fiber-reinforced polyamide 6 (PA6) composites. The introduction of MCA and Sb2O3 enhanced the compatibility of PA6 and glass fiber (GF) at a weight ratio of 70/30, and the mechanical strength, rigidity and flame-retardant properties of the composites were improved significantly with addition of 30 phr of MCA/Sb2O3 mixture. The addition of graphene almost did not affect the mechanical performance of the composites but enhanced their flame-retardant properties remarkably. The composites achieved a limiting oxygen index of 30.1 vol% and UL94 V-0 classification with addition of 0.3 phr of graphene, which promoted both carbonization and foaming action during the combustion of the composites.

Effect of Molding Process Based on UV-curing Injection on Microstructure of Microfluidic Chips

2016, 30 (11): 57-62 ; DOI: 10.19491/j.issn.1001-9278.2016.11.011

Abstract ( 368 )

A UV-curing injection molding prototype was developed, and the replication accuracy for the microstructure of a microfluidic chip was investigated. The results indicated that the filling ability and replication accuracy were improved with increasing hold pressure. Moreover, the intensity of UV irradiation was found to have little influence on the replication of microstructure because there were few effects on total shrinkage by UV irradiation. The low viscosity of the resin mixture was advantageous to the precise molding of microstructure. However, too low viscosity generated serious shrinkage, thus resulting in a decrease in replication degree. Compared with traditional injection molding, the UV-curing injection molding exhibits a much higher replication degree.

Simulation of Film Posting of Vehicle Instrument Panels and Its Global Optimization of Process Parameters

2016, 30 (11): 63-68 ; DOI: 10.19491/j.issn.1001-9278.2016.11.012

Abstract ( 468 )

The finite element method is adopted to simulate the film posting process of outside mold decoration (OMD) by using polycarbonate (PC) as a film material. The distribution of the film thickness and the film deformation contours in x and y directions were derived from this simulation, and the influence factors of film molding were analyzed. In order to achieve a minimum standard deviation in average film thickness and x and ydirectional deformation, an optimal latin hypercube sampling method was adopted to establish the approximate model, and the process parameters of film molding was analyzed by a global optimization model. The results indicated that the uniform distribution of film thickness and high deformation accuracy were achieved on the basis of such a global optimization model.

Crack Analysis and Modification Method for Polytetrafluoroethylene Sealing Rings in One-way Valves of Oxygen Systems

2016, 30 (11): 69-75 ; DOI: 10.19491/j.issn.1001-9278.2016.11.013

Abstract ( 480 )

This article introduced the major molding processes of polytetrafluoroethylene (PTFE) sealing rings used for the one-way valve of oxygen systems in the space engine. The reasons for the occurrence of cracks in the PTFE seal ring were analyzed in terms of the macroscopic aspect and microscopic morphology. The results indicated that the internal gaps within PTFE seal rings could be effectively eliminated when being prepared by use of sieved PTFE powder under an exhaust condition during the cold-pressing per-molding. The tensile properties of PTFE seal rings were improved significantly as a result of this modification, and hence the reliability of PTFE seal rings was enhanced to meet the requirement of aerospace areas for the one-way valve of oxygen systems.

Study of Molding Process and Application of 3D Printing Technology

2016, 30 (11): 76-83 ; DOI: 10.19491/j.issn.1001-9278.2016.11.014

Abstract ( 493 )

This article analyzed the current technical feature, equipment principle and implementation process of several mainstream 3D-printing technologies, which was started from the principle of additive manufacturing(AM). Based on the industrial-scale 3D printer (Dimension Elite) as a research platform, a deposition modeling (FDM) process was adopted for the rapid prototyping of parts with complicated cavity and transmission-component structures. Through a series of practical exploration for 3D modeling, data conversion, slicing process, process parameter selection, model package calculation and postprocessing etc., the technical principle and application procedure of FDM molding process were confirmed. The 3D-printed models were fabricated successfully by using ABS resin. The results indicated that the 3D-molded parts achieved optimum precision and printing efficiency when the slice thickness of complicated cavity parts and transmission components were set to 0.254 and 0.178 mm, respectively.

Fitness Study of Forming Process of Air Conditioner Deflectors Based on Kriging Model

2016, 30 (11): 84-87 ; DOI: 10.19491/j.issn.1001-9278.2016.11.015

Abstract ( 456 )

A wind deflector of air conditioners was taken as a typical example for injection molding in this paper. Based on the different processing parameters of air conditioner deflectors, three different kernel functions were adopted to figure out the fitness examination, and mold temperature, melt temperature, packing time, cooling time, pressure, pressure time was selected as significant factors. The Kriging model was constructed on the basis of Gaussian, generalized exponential and exponential kernel functions, and then the fitness function was established. The results suggested that the Gaussian function was the most appropriate kernel one for the simulation of forming process of air conditioner deflectors.

Heat Stabilization of Organotin Dicarboxylates on Poly(vinyl chloride)—Progressive Change Law of Performance and Mechanism

2016, 30 (11): 88-92 ; DOI: 10.19491/j.issn.1001-9278.2016.11.016

Abstract ( 601 )

The heat-stabilizing effect of several dialkyltin dicarboxylates on poly(vinyl chloride) (PVC) was investigated by an oven discoloration method. The results indicated that the heat-stabilizing function of dialkyltin dicarboxylates toward PVC was improved with an increase of the positive electricity of carbonyl carbon atom in their carboxylate groups. If there were dienophilic structural units in the molecules of dialkyltin dicarboxylates, the discoloring test specimens of PVC stabilized with them showed a lighter color until the specimens were blackened finally. On the basis of the molecular structural characteristics of dialkyltin dicarboxylates as well as the gradually varying regularity of thermal stability for PVC stabilized with them, the stabilization mechanisms are attributed to the electrophilic reaction with PVC through the carbonyl carbon atoms of dialkyltin dicarboxylates and/or dialkyltin ions as a electrophilic center (referred to electrophilic reaction mechanism). If there are dienophilic structural units in the molecule, PVC is stabilized with dialkyltin dicarboxylates in terms of the electrophilic reaction and Diels-Alder reaction mechanisms synchronously. The former plays a primary role and the latter acts as the auxiliaryone.

Modification of Recycled Polyethylene by Isomeric Crosslinking Method

2016, 30 (11): 93-99 ; DOI: 10.19491/j.issn.1001-9278.2016.11.017

Abstract ( 567 )

In this work, crosslinked polyethylene (PE) was first prepared by a silane-crosslinking method, and then was melt-blended with the recycled PE obtained from the water-separated waste PE films. There was a change in aggregation structure observed from the fracture surfaces of blending samples by scanning electronic microscopy, Which indicates the formation of decentralized isomeric structure due to the incorporation of crosslinked PE into the recycled one. The effects of crosslinked PE content on mechanical and rheological properties were evaluated, and differential scanning calorimetry and X-ray diffraction were conducted to investigate the crystallinity and crosslinking degree of the blending sample containing 15 wt% of crosslinked PE. The results indicated that the tensile strength and impact toughness of the recycled PE were improved significantly due to the decentralized isomeric structure, whereas the elongation at break and melt flow rate showed a decline to some extent. The blend sample containing 15 wt% of the crosslinked PE was found to achieve an optimum performance and also exhibit the best crystallinity at a crosslinking degree of 33.5 %.

The sturcture and mold design of plastic flexible wheel

2016, 30 (11): 100-104 ; DOI: 10.19491/j.issn.1001-9278.2016.11.018

Abstract ( 697 )

In view of the problems of materials and manufacturing cost for a steel harmonic gear, a harmonic reducer was fabricated by engineering thermoplastics instead of traditional steel in this work. The structure and relevant parameters of a plastic flexspline were designed to meet the requirement of the transmission, and the corresponding injection mold was also designed. In such a mold design, a computer aided engineering (CAE) method was adopted to confirm that no stagnation phenomenon appeared in the gating system designed. This design also ensured that the deformation of flexspline inner diameter is less than 0.3 mm in the cooling system so as to meet the requirement of the flexspline.