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2017, Volume 31 Issue 04 Publication date: 26 April 2017 Previous Issue Next Issue

Progress in Intrinsic Thermally Conductive Thermoplastics

2017, 31 (04): 1-5 ; DOI: 10.19491/j.issn.1001-9278.2017.04.001

Abstract ( 585 )

This article reviewed the latest progresses in intrinsic thermally conductive thermoplastic polymers and specially analyzed the effects of molecular chain, crystallinity, orientation, hydrogen bonding, temperature and processing methods on thermal conductivity of thermoplastic polymers. Numerous studies indicated that thermal conductivity could be enhanced by improving the order of polymer microstructures, reducing the phonon interface scattering and extending the average free path of phonon transfer. The future development of intrinsic thermally conductive polymers was also proposed.

Influence of Coupling Agents on Thermally Conductive Properties of Polyamide 6/Boron Nitride Composites and Optimization for Their Preparation Technology

2017, 31 (04): 6-10 ; DOI: 10.19491/j.issn.1001-9278.2017.04.002

Abstract ( 556 )

Polyamide 6 (PA6)/boron nitride (h-BN) composites with a high thermal conductivity were prepared via melt compounding. A silane coupling agent, KH 550, and a titanate coupling agent, TM-P, were used to enhance the interfacial adhesion between PA6 and h-BN and also improve the thermal conductivity. An orthogonal experiment was conducted to investigate the effects of the particle size of h-BN, the loading of h-BN and the amounts of coupling agents on the thermally conductive performance of composites. The results indicated that the optimum amounts of coupling agent used were 2.5 wt % and 1 wt% for KH550 and TM-P, respectively, when the loading of h-BN was set to 20 vol %. TM-P exhibits a better modification effect than KH 550, thus leading to a higher thermal conductivity. The thermal conductivity of composites showed an increase at first and then began to decline with an increase of h-BN loading, but the yield strength tend to decrease. The composites achieved much better mechanical properties when using TM-P as a coupling agent. An optimum processing condition was obtained as follows: the content of h-BN was set to 25 vol % and the particle size of h-BN was determined as 10~15 μm. Under this condition, the composites achieved a thermal conductivity of 2.446 W/(m·K).

Study on Structures and Properties of Extruded Polystyrene Foam Board by a Two-procedure Foaming Technique

2017, 31 (04): 11-16 ; DOI: 10.19491/j.issn.1001-9278.2017.04.003

Abstract ( 432 )

An extruded polystyrene foaming board was manufactured through a two-procedure foaming technique by using a combined blowing agent composed of ethanol, carbon dioxide and trans-1,3,3,3-tetrafluoroprop-1-ene ［HFO-1234ze（E）］. The effects of soaking time and temperature on the structures and properties of the foaming board were investigated. The results indicted that the bulk density of the foaming board decreased by about 10 % but its dimension stability was improved significantly by use of the two-procedure foaming technique. However, there were few effects on the other properties. In addition, the foaming board prepared by using a CO2/EtOH combined blowing agent exhibited a foaming behavior similar to that by the CO2/EtOH/HFO-1234ze（E） combined blowing agent.

Study on Thermal Aging Properties of Bamboo Fiber-reinforced Polycaprolactone

2017, 31 (04): 17-23 ; DOI: 10.19491/j.issn.1001-9278.2017.04.004

Abstract ( 407 )

Polycaprolactone (PCL)/bamboo fiber (BF) composites were prepared through a compression molding method and their thermal aging properties were studied. The effects of thermal aging time and temperature and the content of BF on the thermal aging properties of the composites were evaluated by mechanical tests, Fourier-transform infrared spectroscopic analysis and rheological analysis. The results indicated that the decrement in mechanical properties of PCL/BF composites after aging decreased as the content of BF increased initially and increased afterwards. The mechanical properties also decreased with increasing thermal aging temperature and time. The occurrence of thermal oxidation may lead to the decomposition of macromolecular groups inside the composites as well as the hydrolysis of the hydrophilic groups in PCL. In addition, the storage modulus and loss modulus of the composites tended to increase with an increase of thermal aging temperature and time.

Study on Preparation and Properties of Carbon Fiber-reinforced Polypropylene

2017, 31 (04): 24-29 ; DOI: 10.19491/j.issn.1001-9278.2017.04.005

Abstract ( 464 )

Polypropylene (PP)-based composites reinforced by three different carbon fiber (CF) were prepared by melt extrusion and their mechanical properties, melt fluidity, hardness and thermal stability were investigated. The results indicated that the composites achieved much higher tensile strength, flexural strength and impact toughness when using the CF with a length of 7 mm compared with the other two types of CF. However, the incorporation of these three types of CF reduced the melt fluidity of the composites. The higher the content of CF, the lower the melt fluidity. However, higher CF content resulted in greater hardness. The thermal stability was also improved with the addition of CF. Moreover, the presence of CF did not affect the melting temperature of the composite but improved their crystallization temperatures.

Study on Structural Characterization and Crystallization Property,Thermal Performance of PPET Copolyesters

2017, 31 (04): 30-34 ; DOI: 10.19491/j.issn.1001-9278.2017.04.006

Abstract ( 416 )

A series of co-polyesters ［poly(propylene-co-ethylene terephthalate), PPET］ were synthesized by adding various contents of 1,2-propylene glycol (PG) through a direct esterification method. Their structures were characterized systematically and their crystallization property and thermal performance were investigated. Gel permeation chromatography analysis indicated that the PPET has a number average molecular weight of over 29000 and a molecular weight distribution of 1.9~2.1. Nuclear magnetic resonance (NMR) spectroscopic characterization suggested that the weight fraction of PG remained in macromolecular chains was lower than its feed ratio, indicating that PG was more difficult to be introduced into the macromolecular chain than EG. Differential scanning calorimetry analysis demonstrated that the crystallization capability of PPET was reduced in comparison with poly(ethylene terephthalate) (PET), and their melting point also decreased by 24 ℃ when 20 wt % PG was incorporated. In addition, PPET exhibited a thermal stability similar to the conventional PET polyester according to thermogravimetric analysis.

Study on Preparation and Properties of a Novel Toughened Phenolic Insulation Material

2017, 31 (04): 35-39 ; DOI: 10.19491/j.issn.1001-9278.2017.04.007

Abstract ( 369 )

A phenolic foam was prepared by using a mixture of p-toluenesulfonic acid, sulfuric acid and muriatic acid as a curing agent, and the effects of polyethylene glycol, foam stabilizer, curing agent and the content of foaming agent on the structure and properties of the foam were investigated. The results indicated that the structure and properties of the foam could be optimized when the foaming temperature was set to 60 ℃ and the contents of PEG, foaming agent, curing agent and surfactant were set as 10 %, 15 %, 8 % and 5 wt %, respectively.

Effect of Lacquer-seed-shell-fiber Content on Mechanical and Tribological Properties of Polyoxymethylene/Basalt Fiber Composites

2017, 31 (04): 40-44 ; DOI: 10.19491/j.issn.1001-9278.2017.04.008

Abstract ( 347 )

Polyoxymethylene (POM)/basalt fiber (BF)/lacquer seed shell fiber (LSSF) composites were prepared through a melt blending method, and their mechanical properties, tribological performance and microstructure were investigated. The results indicated that the LSSF and BF were homogenously dispersed in POM matrix with good compatibility. The impact toughness, fluidity and friction performance of the ternary composites are improved in comparison with POM/BF composites. The fluidity of POM/BF/LSSF composites increased by 68 % when 10 wt % of LSSF was added. The impact performance was improved by 225 % with the addition of 15 wt % LSSF. Moreover, the composite showed a reduction in friction coefficient by 23 % and in wear loss by 70 %, respectively, at the LSSF content of 5 wt %. The worn mechanism is attributed to abrasive wear for the composites at low contents of LSSF but to abrasive wear and adhesive wear at the high contents of LSSF.

Study on Non-isothermal Crystallization Kinetics of Polyoxymethylene/Polypropylene Blends Used for Catalytic Skim Binder of Metal Powder Injection Molding

2017, 31 (04): 45-50 ; DOI: 10.19491/j.issn.1001-9278.2017.04.009

Abstract ( 570 )

By utilizing the rapid degradation reaction characteristics of polyoxymethylene (POM) under an acidic atmosphere and the corrosion resistance of polypropylene (PP), POM/PP blends were employed as a major component of catalytic skim binder for metal powder injection molding. Crystallization behavior of POM/PP blends was investigated by DSC under the non-isothermal process, and their crystallization kinetics was studied by Jeziorny, Ozawa and Mo methods. The results indicated that the width of crystallization peak became broad and the crystallization peak temperature (Tc) decreased gradually with an increase of cooling rate. Tc of the blends was lower than that of pure POM at the same cooling rate. Jeziorny and Mo methods could well describe the non-isothermal crystallization of POM/PP blending system. However, Ozawa method is not applicable due to the occurrence of secondary crystallization. Moreover, the introduction of PP led to a decrease in crystallization rate but an increase in half crystallization time. This also resulted in a change in the nucleating and growing mechanism of POM domain, thus retarding its crystallization.

Study on Compatibility of Poly(lactic acid)/Poly(butylene adipate-co-terephthalate) Blends

2017, 31 (04): 51-56 ; DOI: 10.19491/j.issn.1001-9278.2017.04.010

Abstract ( 1093 )

Poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) blends were prepared by a melt-blending method, and the effect of tetrabutyl titanate (TBT), benzoyl peroxide (BPO) and acetyl tributyl citrate (ATBC) content on compatibility of PLA/PBAT blends at a weight ratio of 50/50 were investigated by mechanical measurements, differential scanning calorimetry and scanning electron microscopy. The results showed that the introduction of BPO and TBT improved the compatibility of PLA/PBAT blends. The tensile strength of the blends reached a maximum value of 39 and 40 MPa when 0.5 phr of BPO and ATBC was added, respectively. The presence of BPO and ATBC also improved the stiffness but showed no influence on impact toughness. However, the impact toughness can be improved by addition of TBT, and meanwhile, the elongation at break increased by 263 % at 0.5 phr TBT.

Study on Forming Process of Plastic Tubes with Ring-like Micro Capillaries

2017, 31 (04): 57-62 ; DOI: 10.19491/j.issn.1001-9278.2017.04.011

Abstract ( 429 )

Based on a homemade extrusion platform designed for the fabrication of thermoplastic parts with micro capillaries, a novel plastic micro tube with 24 capillaries was first proposed all over the world (Micro Capillary Tube, MCT). These 24 capillaries are orderly located in the circular wall of a tube with a larger hollow channel. The effects of three processing parameters, i.e. injection air pressure, draw ratio and air gap distance, on the quality of the parts were investigated in the extrusion process with conditions of injection air pressures: 0.21~0.36 kPa, air gap distance: 35~110 mm and draw ratio: 2.4~14.1. The results indicated that larger draw ratio could result in a smaller outer and capillary diameter, and there was a negative correlation between the sizes of MCT and draw ratio. However, the draw ratio did not show any influence on the dimensional proportions of cross section of MCT, and a similar trend could be observed in the air gap distance. In contrast, the injection air gap severely damaged the dimensional proportions and changed the shape and size of micro capillary, but it did not change the external size.

Study on Mechanical Behavior of New Type of High Strength Cables Under Combined Load

2017, 31 (04): 63-69 ; DOI: 10.19491/j.issn.1001-9278.2017.04.012

Abstract ( 297 )

A new type of high-strength resin/fiber composite cables with hollow multilayered structure was proposed. The theoretical model of the high-strength cable was established based on the micro mechanics of composite materials and its applicability was further verified by a horizontal tensile test. Finally, the stress strain behavior of the cable was analyzed by using the theory and numerical methods. The results indicated that the effect of different boundary conditions on the analysis results was insignificant under a relative error of about 3.12 %. The axial elongation, radial contraction and axial torsion angle were greatly influenced by suspension mass, whereas the internal pressure exhibited few effects on the axial extension rate and axial twist angle. On the other hand, the relative growth rate of the radial deformation increased by 12.32 % with an each additional increase of 5 MPa in internal pressure. The use of small angle winding scheme can improve the tensile stiffness of the cable, but there was a stress fluctuation appearing between the layers of the cable, which leads to an internal instability. The high-strength cable can meet the requirements of production under the normal conditions with a suspension quality of 10 t and an internal pressure of 15 MPa.

Research and Application of Middle- and High- Pressure Connection Technology for Steel Wire Mesh Skeleton Polyethylene Composite Pipes

2017, 31 (04): 70-74 ; DOI: 10.19491/j.issn.1001-9278.2017.04.013

Abstract ( 488 )

This article briefly introduced the current situation of connection technology and applications in steel wire mesh skeleton polyethylene composite pipes and also analyzed their technical developments in the middle- and high-pressure connection technology. Taking the water supply pipeline project in the Enshi mountain area of Hubei Province as a typical example, the successful application of this high-pressure connection technology was introduced. This project promoted the application of steel wire mesh skeleton polyethylene composite pipes in the construction of middle- and high-pressure pipelines.

Effect of Rapid Prototyping Technique on Mechanical Properties of Plastic Parts Through FDM Process

2017, 31 (04): 75-80 ; DOI: 10.19491/j.issn.1001-9278.2017.04.014

Abstract ( 353 )

Taking ABS-M30, PPSF and Ultem 9085 3D printing materials as three typical cases, the plastic parts were formed through a fused deposition modeling (FDM) method, and the effect of raw materials, setting angles and printer nozzles on the mechanical properties of the parts were investigated. The results indicated that the tensile and impact strength increased at first and tended to decrease afterwards when the setting angels of printer varied from 0 ° to 90 °, and they achieved maximum values at the setting angel of 45 °. The flexural strength increased with an increase of setting angel. Moreover, the plastic parts formed by T16-type printer nozzle gained better mechanical properties than that formed by T12-type nozzle at the same position angle.

Effect of Crystallization and Melting Behaviors of Polypropylene Modified with CaSO4 Whiskers/TMB-5 Combined Nucleating Agent

2017, 31 (04): 81-84 ; DOI: 10.19491/j.issn.1001-9278.2017.04.015

Abstract ( 484 )

A surface modification of calcium sulfate whiskers was performed by using a KH-550 silane coupling agent, and their structures before and after the surface modification were investigated comparatively by Fourier-transform infrared spectroscopy. The crystallization and melting behaviors of polypropylene (PP) nucleated with β-nucleating agent (TMB-5), surface-modified CaSO4 whiskers(K-CSW), and a mixture of CaSO4 whiskers and TMB-5 were studied by differential scanning calorimetry, and the nucleating effects of these three nucleating agents were compared. The results indicated that the K-CSW could effectively promote the formation of β-crystals and it also exhibited a synergistic nucleating effect with TMB-5, thus resulting in an improvement in crystallinity of PP. When 0.2 wt % of TMB-5 and 2 wt % of K-CSW were incorporated into PP, the relative content of β-crystals in PP reached 90.1 %, and the peak crystallization temperature of nucleated PP increased to 127.2 ℃ from 122.3 ℃ of pure PP.

Effects of Test Parameters on Determination of Nano-indentation Hardness for Polymer Resins

2017, 31 (04): 85-90 ; DOI: 10.19491/j.issn.1001-9278.2017.04.016

Abstract ( 464 )

The effects of maximum load, load time and hold time on the determination of nano-indentation hardness for polymer resins were investigated in this paper. The results indicated that the maximum load and load time had few influences on the test result of nano-indentation hardness, but the hold time exhibited a significant effect. The test results decreased gradually with an increase of hold time.

Improvement of Gas-assisted Injection Molds and Process Optimization for Car Door Handles

2017, 31 (04): 91-96 ; DOI: 10.19491/j.issn.1001-9278.2017.04.017

Abstract ( 476 )

Eccentric penetration, inadequate empty, and surface defects were found in a car door handle produced by a gas-assisted injection mold during the tooling test. CAE technology was adopted to discover the causes of these problems. The adjustment of gate location, gas injection location and overflow port location were adjusted, which could effectively eliminate the eccentric gas penetration and surface defect. CAE technology was also used to optimize the processing parameters including the shot size of the melt, gas pressure, gasinjection delay time, mold temperature and melt temperature. As a result, a good gas penetration was achieved. This study confirmed that the CAE technology was a necessary means that can ensure a reasonable design for the gasassisted injection mold as well as optimizes the processing parameters.

Innovation Design of Injection Molds for Military Telescope Shells Based on Intersectional Slider Threaded Core-pulling Mechanism

2017, 31 (04): 97-101 ; DOI: 10.19491/j.issn.1001-9278.2017.04.018

Abstract ( 432 )

In view of the problems that there are multiple threaded core-pulling mechanism and the intersection of slide blocks in military telescopes, the structure of their plastic parts was first analyzed, and then a motor which drives the gear core-pulling mechanism was adopted and multiple limit switch controllers were also used to design the relevant injection mold. Such a design made the mold work in good order and also resolved the demolding difficulty. The fabricated mould exhibited a stable run cycle and an ordered motion for various sliders during the demolding process. This mould has been used for mass production, and the obtained parts gain a good quality with a process yield over 98 %.

Design of Gas-assisted Injection Molds for Car Interior Door Handles

2017, 31 (04): 102-105 ; DOI: 10.19491/j.issn.1001-9278.2017.04.019

Abstract ( 551 )

An injection mould for a car interior handle was designed by using an inverse blowing gas-assisted molding technology in a full injection mode. When designing the groove structure for melt overflow, cut-off valve and hot runner nozzle were introduced into the mould so as to improve the efficiency of melt overflow and also to overcome the defects appearing in the inverse blowing gas-assisted molding. With the use of a horn-shape latent gate and the reasonable setting of ejection position, the aspects without any gate and ejector marks were guaranteed for the injection-molded parts. This mould has been used for the production of parts, and the products exhibit a good appearance as well as a lightweight feature with a reduction in weight by 20 % compared with the similar products.