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2018, Volume 32 Issue 11 Publication date: 26 November 2018 Previous Issue Next Issue

Progress in Thermally Conductive Polymers/Graphene Composites

2018, 32 (11): 1-6,70; DOI: 10.19491/j.issn.1001-9278.2018.11.001

Abstract ( 513 )

This article reviewed the latest research progress in thermally conductive polymers/graphene composites and emphatically discussed the influence factors on thermal conductivity of reinforced polymers, which included the structure and surface functionalization of graphene, the core-shell structural composites or hybrids with graphene as well as their synergistic effect, graphene foams and their processing technologies. Moreover, the current problems in the industrialization of thermally conductive polymers/graphene composites were summarized and their development direction in future was prospected.

Research Progress in Bioactive Enhancement of Polyetheretherketone by Surface Modifications for Hard Tissue Implants

2018, 32 (11): 7-18; DOI: 10.19491/j.issn.1001-9278.2018.11.002

Abstract ( 617 )

Polyetheretherketone (PEEK) is a prominent candidate for hard tissue implants to replace traditional biomedical metallic materials due to its outstanding biocompatibility and elastic modulus analogous to the human cortical bone. However, there is insufficient bioactivity for PEEK, thus resulting in a difficulty in application for hard tissue implants. This paper reviewed the research progress in bioactive enhancement of PEEK by surface modification. At first, the surface coating of hydroxyapatite and titanium dioxide for PEEK was considered as primary modification techniques such as plasma spraying and spin coating, which could endow PEEK with bioactivity. Moreover, the direct surface modification strategies were also widely adopted to enhance the bioactivity of PEEK. These strategies included plasma immersion ion implantation, laser treatment and chemical surface wetting. Bacterial infection was broadly recognized as one of the main causes of implant failure. Therefore, the enhancement of the bioactivity and antibacterial capability of PEEK implants by surface modification has become the hot topics in recent years. This paper introduced the recent research status of these surface modification techniques for bioactive enhancement of PEEK and also prospected its development direction in future.

Effect of TPU on Fused Deposition Modeling Performance of ABS/TPU Compounds

2018, 32 (11): 19-23,60; DOI: 10.19491/j.issn.1001-9278.2018.11.003

Abstract ( 782 )

The 3D printing filaments based on ABS/thermoplastic polyurethane (TPU) blends were prepared by a melt blending method. These 3D printing filaments were subsequently processed to the standard test samples by fused deposition modeling (FDM), and their modeling performance, mechanical properties, microstructure and rheological properties were investigated. The results indicted that the introduction of TPU improved the modeling performance of ABS. With the addition of 20 wt % of TPU into ABS, the warp shrinkage disappeared in the modeling process. At this weight fraction, the molded sample obtained the enhanced notched impact strength of 18.81 kJ/m2 and the declined tensile strength of 32.92 MPa, which increased by 95.94 % and decreased by 8.5 %, respectively, compared to those of pure ABS. Morphological observation indicated that the molded sample presented ductile fracture at a weight fraction of TPU over 20 wt %. Moreover, the roughness of the impact fracture surface with an increase of TPU content and some holes were observed. The rheological investigation indicated that there was good compatibility between ABS and TPU, and the increase of TPU content enhanced the diffusion capability of macromolecular chains for these two polymers.

Study on Weld Line Strength of Talc-filled ABS Compounds

2018, 32 (11): 24-28; DOI: 10.19491/j.issn.1001-9278.2018.11.004

Abstract ( 676 )

The talc-filled ABS compounds were prepared by melt blending, and the effects of talc content and size as well as lubrication on their weld line strength were investigated. The micromorphology of the interface between weld line and dispersed fillers was observed with scanning electron microscope. The results indicated that the weld line strength of the compoundsdecreased due to the barrier effect on diffusion and fusion of macromolecular chains by talc sheets. Theweld line strength of ABS could be improved effectively by incorporation of talc at a low content, mixture of talc and wollastonite, or amide lubrication with polar groups. The ABS compounds achieved the weld mark strength of 33.4 MPa when 5 wt % of talc, 5 wt % of wollastonite and 1 wt % of modified amide lubrication were added.

Effect of Fluoropolymer on Processing Properties of Metallocene Polyethylene

2018, 32 (11): 29-34; DOI: 10.19491/j.issn.1001-9278.2018.11.005

Abstract ( 517 )

Four types of polyphthalamide (PPA) resins were incorporated into metallocene polyethylene (mPE) at four different weight fractions to modify its processing properties. As a result, the main engine load and die pressure of twin-screw extruder or film blower were reduced effectively during the extrusion process. The effect of PPA on the mechanical, optical and rheological properties of mPE was investigated. The results indicated that the modification effect of PPA was not only related to the weight fraction of PPA resins but also related to the content and type of dispersant. The critical shear rate of mPE powders was found to increase from 281 s-1 to 1 400 s-1 with addition of PPA, suggesting a significant improvement in processability. Moreover, the introduction of PPA affected the tensile properties, dart impact strength and optical properties of mPE films. The haze of the film decreased to 12.4 % in the presence of PPA-4, whereas the mPE achieved the dart impact strength of 71 g due to the addition of PPA-3. The optimum additive amount of PPA is strongly dependent on the practical requirements.

Study on Aging Behavior of Flame-retardant PVC Flexible Wire at Critical Temperature

2018, 32 (11): 35-41; DOI: 10.19491/j.issn.1001-9278.2018.11.006

Abstract ( 570 )

This paper reported an investigation on the effect of thermal oxygen aging on the physical and chemical properties of flameretardant PVC insulation materials (ZR-BVR) used for flexible wire. A critical ambient temperature of 70 ℃ was selected as the aging temperature for ZR-BVR wire, and the aging behavior of the flexible wire was tested and then analyzed by using scanning electron microscope, Fouriertransform infrared spectrometer, microcomputercontrolled electronic universal testing machine and thermogravimetric analyzer. The results indicated that the physical and chemical properties of the aged ZR-BVR were changed during the heat and oxygen aging treatments. Some blisters were observed on the surface of tested specimens, and the absorbance of absorption peak corresponding to the methyl bending vibration decreased when the aging treatment was carried out for 20 days. Some cracks appeared on the surface of test specimens after aging for 40 days. The thermal stability of ZR-BVR decreased gradually, and meanwhile the risk of pyrolysis and combustion seemed to increase gradually. The electrical trees were generated after aging for 60 days. The elongation at break also decreased to 61.78% after aging for 80 days compared to its original value of 244%.

Study on Chain Extension and Microcellular Foaming Behaviors of Poly (butyleneadipate-co-terephthlate)

2018, 32 (11): 42-48; DOI: 10.19491/j.issn.1001-9278.2018.11.007

Abstract ( 885 )

The chainextended poly(butyleneadipate-co-terephthlate)(PBAT) was prepared by use of different amounts of chain extender through reactive melt blending. An investigation indicated that the torque, gel fraction and crystallization temperature of chain-extended PBAT were improved with an increase of weight fraction of chain extender. However, its melting temperature kept stable, followed by a modification of viscosity, whereas its degree of crystallinity decreased. The micro-foaming PBAT materials were prepared by using supercritical CO2 as a physical foaming agent. The structural characterizations and performance evaluation indicated that the cell size of PBAT foams decreased with an increase in weight fraction of chain extender, but their cell density was improved.When the weight fraction of chain extender was set as 0.8, the PBAT foams achieved a cell size of 4.4 μm and a cell density of 1.65 × 1010 cells/cm3.

Study on Properties and Adhesion Strength of Sulfonic-2-hydroxypropane Starch/Polyacrylate Composite Films

2018, 32 (11): 49-53; DOI: 10.19491/j.issn.1001-9278.2018.11.008

Abstract ( 529 )

A series of sulfonic-2-hydroxypropane corn starch (SHPS) as acidconverted cornstarch were prepared by a reaction of corn starch with an etherifying agent, 3-chloro-2-hydroxypropanesulfonic acid sodium salt.The surface morphology of SHPS granules was observed by scanning electron microscope, and the effect of sulfonic-2-hydroxypropane modification on properties of SHPS/polyacrylate composite films was investigated. Moreover, the effect of modification reaction degree on the properties of the composite films was also evaluated. The results indicated that the modification reaction improved the elongation at break of the composite films butreduced their tensile strengths, and a toughening effect was observed. In addition, thesulfonic-2-hydroxypropane modification not only enhanced the adhesion strengths of the composite films to cotton and polyester roving but also improved their degree of swelling. With the increase of modification level, the composite films achieved an increase in elongation at break by 29 % but presented a slight decrease in tensile strength. This indicates a gradual increase in toughening effect. Moreover, the adhesion strengths also increased gradually with an increase in modificationlevel.

Electrospinning Preparation and Analysis of PAN/TiO₂-GO Hybrid Fiber Membrane

2018, 32 (11): 54-60; DOI: 10.19491/j.issn.1001-9278.2018.11.009

Abstract ( 595 )

Polyacrylonitrile (PAN)/titanium dioxide (TiO2)-grapheneoxide (GO) hybrid fiber membranes were prepared by an electrospinning method, followed by calcination. The morphology, crystallization behaviors, thermal properties and photocatalytic performance of the hybrid fibers were investigated by scanning electron microscopy, X-ray diffraction, thermogravimetic analysis and spectrophotometry. The results indicated that tetrabutyltitanate hydrolysateswerewell converted to anatase TiO2 after calcinations. The fiber diameter decreased gradually to a minimum value of 25 nm with an increase of tetrabutyltitanate content.Moreover, the addition of tetrabutyltitanate improved the thermal stability of the fibers. In addition, a methine blue degradation experiment confirmed that the photocatalytic activity of the fibers was improved due to the addition of tetrabutyltitanate. Summarily, the PAN/TiO2-GO hybrid fiber membranes developed by this work can be used as a photocatalyst.

Effects of Molding Method and Processing Technology on Optical Performance of MCOC Light Guide Plate with Different Structures

2018, 32 (11): 61-65; DOI: 10.19491/j.issn.1001-9278.2018.11.010

Abstract ( 449 )

Aiming at the concern about light performance of light guide plate (LGP) and taking light transmittance and haze as optical indices, the effects of molding method, process parameters and product structure on the optical performance of the LGP made from metallocene cycloolefin copolymer (MCOC) were investigated. The results indicated that the light transmittance of injection-compression molded LGP was normally higher than that of the ones molded by other methods. The injection-compression molding method made the LGP the highest value of 93.73 % with a haze lower than other molding methods. With an increase in mold temperature, the haze tended to increase for all of the LGP products, and there was no remarkable change found in melt temperature. The light transmittance of thin-wall LGP was found to be higher than that of the thick wall one. Moreover, the light transmittance of the dot-slot structural LGP was higher than the groove structural one, but its haze was much lower.

Study on Mechanical Properties of Quaternized and Octenylsuccinylated Starch/PVA Blend Films

2018, 32 (11): 66-70; DOI: 10.19491/j.issn.1001-9278.2018.11.011

Abstract ( 563 )

To overcome the rigid and brittle defects in starch films,quaternized and octenylsuccinylated starch (QAS) was prepared and then mixed with poly(vinyl alcohol) (PVA) to prepare blend films. The crystallinity of the blend films was measured by X-ray diffractometer, and their surface morphology was observed with scanning electron microscope. The effects of QAS/PVA weight ratio and PVA structure on the mechanical properties of the blend films wereinvestigated. The results indicated that the degree of crystallinity of blend films was lower than that of pure QAS film. The elongation at break of blend films decreased gradually with an increase of QAS content,but their breaking strength decreased with the QAS content at first and then tended to increase. The blend films exhibitedminimum breaking strength at the QAS/PVA weight ratio of 50/50. Moreover, the breaking strength and elongation at break both increased with the increase of polymerization and alcoholysis degrees of PVA.

Online Measurement Method of Repeat Accuracy of Injection Weight

2018, 32 (11): 71-75,83; DOI: 10.19491/j.issn.1001-9278.2018.11.012

Abstract ( 493 )

Based on control and error analysis theory, the accuracy of injection weight in the injection-molding process was studied by an online measurement method, and their influence factors were investigated for the samples with different sizes using statistical error algorithm, followed by a comparative analysis. To ensure a real-time efficiency and high accuracy for this test method, the sampling capacity was taken as 5, 10 and 15 for three sets of experiments, and the sampling cycle points were updated successively and recursively. The test and calculation methods were further verified by a modified experimental equipment. The optimal sample size was determined to be 10, and the optimum algorithm was confirmed as the standard deviation one. The research results indicated that the measurement method developed by this work could provide an effective evaluation for the quality accuracy of injection products on the basis of online measurement of ultrasonic melt density, and the test accuracy was in the range of 0.50 %~1.50 %, verifying the feasibility of this measurement method.

Effect of Processing Parameters on Quality and Micromorphology of WAIM Pipes Based on Polypropylene/Polyamide 6 Blends

2018, 32 (11): 76-83; DOI: 10.19491/j.issn.1001-9278.2018.11.013

Abstract ( 354 )

A water-assisted injection molding (WAIM) experiment was carried out for polypropylene (PP)/polyamide 6 (PA6) blends on a lab-developed WAIM experimental platform. The experimental and theoretical methods were combined to investigate the effect of processing parameters on the residual wall thickness (RWT), surface quality and mechanical properties of the pipe obtained from WAIM. The results indicated that the RWT decreased gradually with increasing the melt temperature, mold temperature and water injection pressure, and however it increased with an increase in water injection delay time. Moreover, the tensile strength of the pipe increased gradually with the increase of mold temperature and water injection delay time. Nevertheless, when the melt temperature and water injection pressure were improved, the tensile strength tended to decrease gradually. The processing parameters affected the temperature field and therefore influencedthe nucleation and crystal growth as well as the final crystallinity. The higher the degree of crystallinity, the higher was the tensile strength of the pipes.

Simulating Analysis of Internal Cooling Process for Rotational Molded Pallet

2018, 32 (11): 84-88; DOI: 10.19491/j.issn.1001-9278.2018.11.014

Abstract ( 383 )

To investigate the effects of the distance between air inlet and outlet in pallet, the number and layout of air inlets and outlets, and the diameter of air outlet on internal cooling time, a numerical simulation was carried out for the internal cooling process of rotational molded pallet by use of the Fluent software. The results indicated that the increase of the distance between air inlet and outlet led to a decrease in internal cooling time. In order to obtain a better internal cooling effect, the total area of air inlets should be larger than that of air outlets. In the cases of one air inlet and one air outlet, the internal cooling time was shortest when the outlet diameter was reduced to 79 % of the inlet diameter. However, the internal cooling time increased dramatically if the outlet diameter was smaller than this value.

Transient Flow Analysis of Flow Field in 6I-tpye Rotor Internal Mixer

2018, 32 (11): 89-95; DOI: 10.19491/j.issn.1001-9278.2018.11.015

Abstract ( 416 )

The flow field and rotor of 6I rotor internal mixer were analyzed by a transient analysis method, and the velocity vector diagram, shear rate cloud map, velocity and pressure curves at specific points were obtained at different time. The flow lines at different positions were also analyzed. The results indicated that the mixing effect of flow field in the middle mixing zone was not only influenced by the extrusion of the top of edge, but also promoted by the propelling flow from the front of edge. The discharge of the long edges resulted in bending deformation of edge, which greatly affects the stress distribution in the rotor edge. The axis position of rotor and the stress distribution at the root were greatly influenced by the shape of the top of rotor. Although the axial discharge of the long and short edges was disadvantageous to the formation of the drag and drop flow, the discharge generated a positive effect on the overall mixing flow. Most of spiral upwelling was produced at the middle edge, which could gather a large number of fluids and guide the axial flow at any positions.

Study on Variation Law of Corrosion Behavior of Plastics Used in Non-metal Pressure Vessel

2018, 32 (11): 96-101; DOI: 10.19491/j.issn.1001-9278.2018.11.016

Abstract ( 378 )

Thermoplastics have been widely used in petroleum, chemical, construction,urban gathering and transportation systems due to their superior performance. This work focuses on the corrosive behaviors of linear low-density polyethylene (PE-LLD) and polypropylene (PP) against sulfuric acid, nitric acid, hydrochloric acid, sodium hydroxide and sodium chloride solution.The research results indicate that the impact strength of PP was found to show a loss rate of 23.9 % after corrosion ina 10 wt % NaOH solution for one week, whereas the loss rate for PE-LLD was 22.6% after corrosion in a 10 wt% HCl solution for two weeks. The effect of H2SO4 solution with a concentration of 10 wt% on the melting enthalpy of PE-LLD was very noticeable, and the enthalpy value decreased by 54.4% after immersion corrosion for 6 weeks.

Preparation of High Rigid and High Heat-resistant Polypropylene by Combination of Sodium Phosphate and Talc

2018, 32 (11): 102-108; DOI: 10.19491/j.issn.1001-9278.2018.11.017

Abstract ( 475 )

The polypropylene (PP)/Talc compounding system and polypropylene/sodium phosphate nucleating agent (NA-40)/Talc compounding system were prepared by a melt mixing method, and the effect of Talc content on the mechanical properties, heat resistance, flow properties and crystallization temperature of two compound systems was investigated.The reasons for improvement in mechanical properties of compounding systems were analyzed by a dynamic method.The results indicated that the compounds achieved the flexural modulus of 2 316 MPa, a heat distortion temperature of 120 ℃ and a crystallization temperature of 132.9 ℃ when 0.2 wt % of NA-40 and 10 wt % of Talc were added into PP. Meanwhile,the flow properties of the compounds seemed not to change. These results meetthe requirements of PP for high rigidity and high heat-resistance.

Additive

Influences on the Synthesis of Lanthanum nicotinate and Its Thermal Stabilizing Effect on PVC

2018, 32 (11): 109-115; DOI: 10.19491/j.issn.1001-9278.2018.11.018

Abstract ( 477 )

Lanthanum iso-nicotinate was synthesized by using nicotinic acid, lanthanum nitrate and sodium hydroxide as raw materials, and its structure and composition were analyzed and characterized. The effect of lanthanum iso-nicotinate on the thermal stability and discoloration of poly(vinyl chloride) (PVC) was studied by means of the Congo red and high temperature aging methods. A comparative investigation on heat stability was also performed for the PVC compounds stabilized with different heat stabilizers including lanthanum stearate, zinc stearate, calcium stearate and pentaerythritol. The results indicated that lanthanum iso-nicotinate could not generate an ideal and long-term heat-stabilizing effect on PVC when used alone, and the anti-discoloration capability was also not good. The PVC compounds achieved the stability time of 22 min at a stabilizer loading of 2.5 wt% when the weight ratio of lanthanum iso-nicotinate/zinc stearate/pentaerythritol was set to 3/1/1. The stabilization mechanism of lanthanum iso-nicotinate could be attributed to the absorption of the HCl released by decomposition of PVC, resulting in the production of LaCl3. This reduced the catalytic effect of HCl on the decomposition of PVC and thus inhibited its degradation.

Degradation Properties of Poly(propylene carbonate)/Poly(lactic acid) Blends Under Natural Light Irradiation

2018, 32 (11): 116-124; DOI: 10.19491/j.issn.1001-9278.2018.11.019

Abstract ( 537 )

The degradation properties of poly(propylene carbonate) (PPC)/poly(lactic acid)(PLA) blends were studied under natural light irradiation, andthevariations in mechanical properties, weight loss, surface microstructure of the blends were investigated.The results indicated that the weight-loss rate of the blends were 34.89 wt%，40.50 wt%，39.38 wt%，29.6 wt% and 6.24 wt% at the PPC/PLA mass ratios of 100/0, 70/30, 50/50, 30/70 and 0/100, respectively, after irradiation for 56 days. The blends lost almost all of their mechanical properties after irradiation for 14 days. There were obvious cracks and holes found on the surface of pure PPC and PPC/PLA blends at a mass ratio of 50/50 after irradiation for 56 days, and however there was no change found on the surface of pure PLA.It was also observed that the longer the irradiation time, the coarser the surface of blends, and the greater was the degree of degradation. The hydroxyl index and carbonyl index of the blends were found to increase continuously at the first 21 days, especially within the first 14 days.The relative molecular weight and polydispersityindex of the blends decreased, which made the molecular weight distribution narrowed after irradiated for 56 days accordingly. Moreover, the blends presented an increase in thermal decomposition temperature and weight loss temperature (Tp) at a maximum rate, whereaspure PPC showed a decrease in TP after irradiation.

Design of Combined Cavity Injection Mold for Small-size Plastic Parts

2018, 32 (11): 125-130; DOI: 10.19491/j.issn.1001-9278.2018.11.020

Abstract ( 504 )

This paper reported the design of a combined cavity injection mold with four small injection components for a smallsize thermoplastic electric product. The structural characteristics of each component were firstly analyzed, and then an optimized non-natural balance gating system was designed for this combined cavity mold on the basis of filling analysis results using the Moldflow Insight software. Afterward,the gating system, molding parts, demolding system and its operation procedure, cooling systems and structurewere designed. The experimental results indicated that the design methodology developed by this work could provide guidance and solutions for the design of small-size combined cavity injection mold and lead to a significant improvement in product quality for injection-molded parts.

Reverse Engineering Modeling and Mold Design of Handle Back Cover of Hair Dryer

2018, 32 (11): 131-135; DOI: 10.19491/j.issn.1001-9278.2018.11.021

Abstract ( 533 )

This paper reported a reverse engineering modeling method as well as amold design for the handle back cover of a hair dryer. A multiple scan was firstly carried out for this plastic back cover using a scanner to obtain point cloud, and then the geometric model was reconstructed. The design schemes of mold cooling and pouring systems were analyzed by using the Moldflow software to gain the optimal design proposal. A suitable formwork was selected, and the structure of the outlet was also designed. The overall structure of the mold wasdesigned successfully. The whole design process in this workcan provide useful guidance for the design of similar molds with complicated structures.

Structural Design of Pressure-injection Mould for a BMC Thermosetting Tripod

2018, 32 (11): 136-141; DOI: 10.19491/j.issn.1001-9278.2018.11.022

Abstract ( 375 )

Aimed at the requirement for thermosetting plastic injection molding process, a two-plate pressure injection mould with a layout of one mold and two cavities was designed. An edge type gate was designed as the sprue gate, and a column was used to perform pressure-injection, where the injection pressure was controlled in the range of 7~32 MPa. The injection chamber was heated by an electric heating system, and the molding parts were heated by using FYD350 heat conduction oil. The temperatures of the upper die inserts and lower mould inserts were controlled in the ranges of 153~156 ℃ and 148~151 ℃, respectively. Three kinds of exhaust modes were adopted to exhaust the cavity. According to the characteristics of side holes, three side-core pulling slider mechanisms were designed to demould the die, and a two-sided pin resetting mechanism was designed to reset the ejecting mechanism earlier. The design of this mould structure is reasonable, and its mechanism designed by this work is simple. Such a design can be used as a reference for the design of injection molds of similar plastic parts.