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2019, Volume 33 Issue 5 Publication date: 26 May 2019 Previous Issue Next Issue

Design and Preparation of PA6/PET Blends with Encapsulation Structure

2019, 33 (5): 1-6; DOI: 10.19491/j.issn.1001-9278.2019.05.001

Abstract ( 458 )

The polyamide 6 (PA6)/polyethylene terephthalate (PET) blends with an encapsulation structure were prepared by means of a twin-screw extruder combined with a high-pressure capillary rheometer, and the effect of viscosity ratio of two components on the encapsulation structure of the blends was investigated under different shear ratesin the extruding process. Polarized light microscopic and scanning electron microscopic observations showed that the PET phase could eventually migrate into the surface of the extrudate to encapsulate the PA6 phase. Raman spectroscopy indicated that the aggregation level of PET phase changed in the radial direction at the interface of two components, which ensured good interfacial properties of final products. In addition, the melt viscosity matching of two components was a necessary precondition for the formation of the encapsulation structure. Moreover, there was an optimal range of shear rate (or viscosity ratio range), and the encapsulation structure obtained in this processing condition is relatively perfect.

Microporous Structure and Properties of RPU/Amino-modified Graphene Oxide Foam Composites

2019, 33 (5): 7-13; DOI: 10.19491/j.issn.1001-9278.2019.05.002

Abstract ( 459 )

The graphene oxide (GO) was modified by an amidation reaction using polyetheramine and triethylenetetramine, and then its structure was characterized by Fourier-transform infrared spectroscopy and X-ray photoelectric spectroscopy. The two types of amino-modified GO were introduced into the rigid polyurethane (RPU) foams and their effects on the morphological structure, apparent density, compressive strength and the thermal conductivity of composite foams were comparatively investigated. The results indicated that, the addition of two types of amino-modified GO led to a smooth cell wall, uniform cell structure and small average pore size for the resulting RPU composite foams. The investigation of mechanical performance showed that the addition of amino-modified GO caused an improvement in the apparent density, compressive strength and modulus of composite foams, and however an opposite effect was achieved with the addition of GO virginal. The thermal conductivity of composite foams was found to increase slightly in an acceptable range due to the presence of any types of GO.

Preparation and Application of Melamine Methylphosphonate for Highly Efficient Flame Retardancy of Unsaturated Polyester

2019, 33 (5): 14-18; DOI: 10.19491/j.issn.1001-9278.2019.05.003

Abstract ( 401 )

Melamine methylphosphonate (MMP) was synthesized through a reaction of methylphosphonic acid with melamine, and its chemical structure was characterized by Fourier transform infrared spectroscopy.Thermogravimetric analysis (TG) indicated that MMP exhibited an initial thermal decomposition temperature of 228 ℃ and a char yield of 41.2 wt.% at 800 ℃, suggesting an excellent thermal stability and charring capability. MMP was used for flame retardancy of unsaturated polyester resin (UPR), and the resulting thermosetting compounds achieved a UL 94 V-0 classification in the vertical burning experiment and a limiting oxygen index of 38.5 vol.% when 21 wt.% MMP was incorporated. This result demonstrated that the synthesized MMP had a high efficient flame retarding effect on UPR. The TG results indicated the introduction of MMP could promote the decomposition and charring of UPR and thus improved its char formation and thermal stability at high temperature. Scanning electron microscopic observation confirmed the formation of a compact and expanded char layer for the compounds during combustion. It was believed that the formed char layer inhibited the mass and heat transfer and consequently protected the underlying materials from further degradation. As a result, the flame retardant performance of UPR compounds was enhanced.

Preparation and Electrical Response Behavior of PAAS/PVA Composite Hydrogels

2019, 33 (5): 19-24; DOI: 10.19491/j.issn.1001-9278.2019.05.004

Abstract ( 1268 )

A series of PAAS/PVA composite hydrogels with an interpenetrating network structure were prepared by using potassium persulfate as an initiator and N,N′-dimethylbisacrylamide as a crosslinking agent through a freeze-thaw cross-linking pathway, and their chemical structure and performance were characterized by means of Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy, thermogravimetric analysis (TG) and universal mechanical testing machine. FTIR characterization identified that the PVA was uniformly dispersed in the interpenetrating network-structured hydrogels. TG results indicated that the addition of PVA improved the thermal properties of the composite hydrogels. Moreover, the addition of PVA reduced the swelling rate and maximum swelling of the composite hydrogels, and incorporation of 14 wt.% PVA into PAAS led to a minimum swelling rate for the composite hydrogels. The introduction of PVA could significantly improve the mechanical properties of the composite hydrogels, and their elongation at break and tensile strength increased with an increase of PVA content. The electrical response experimental results indicated that the electrical response sensitivity of the composite hydrogels was improved due to the addition of PVA with an optimum content of 21 wt.% PVA.

Effects of Inorganic Silica Compound and Phosphananthrene-borate Molecular Hybridon Flame Retardant Properties of Epoxy Resin

2019, 33 (5): 25-29; DOI: 10.19491/j.issn.1001-9278.2019.05.005

Abstract ( 452 )

The flame retardant epoxy compounds were prepared by mixing phosphoheterophene-borate molecular hybrid (ODOPB-Borate) with organic modified montmorillonite (OMMT) and SiO2,the synergistic effect of silicon-containing halogen-free flame retardants consisting of OMMT, SiO2 and ODOPB-Borate on the flame retardant performance of epoxy resin was investigated by means of thermogravimetric analysis, limiting oxygen index (LOI) and cone calorimetry. The results indicated that a combination of OMMT, SiO2 and ODOPB-Borate could effectively improve the flame retardant effect on epoxy resin. When 4 wt% of binary-combined flame retardant was incorporated at the OMMT/ODOPB-Borate or SiO2/ODOPB-Borate mass ratio of 1/7, the resulting epoxy compound achieved an LOI of 38.5 vol%~38.8 vol% as well as a UL 94 V-0 classification in the vertical burning test. Based on the experimental results in this work, the introduction of OMMT and SiO2could reduce the heat release rate of epoxy/ODOPB-Borate compounding system, improve their barrier protection, and optimize the distribution of flame retardant effect in the gas phase and condensed phase. These results confirmed a synergistic flame retardant effect between OMMT, silicon dioxide and ODOPB-Borate.

Preparation and Properties of Flame-retardant Thermoplastic Polyurethane Composites

2019, 33 (5): 30-36; DOI: 10.19491/j.issn.1001-9278.2019.05.006

Abstract ( 516 )

Aluminum hypophosphite (AHP) and melamine cyanurate (MCA) were adopted as flame retardants to prepare a series of flame retardant thermoplastic polyurethane elastomer composites (FR-TPU) by a melt blending method. The thermal stability, flame retardant performance, combustion properties, mechanical properties and char morphology of the resulting FR-TPU were investigated by means of thermogravimetric analysis, limiting oxygen index (LOI) test, UL 94 vertical burning experiment, cone calorimetry, mechanical measurements and scanning electron microscopy. The results indicated that the combination of AHP and MCA could enhance the flame retardancy of TPU, and the FR-TPU containing 20 wt.% of AHP-MCA achieved a LOI of 30.5 vol.% as well as a UL 94 V-0 classification in the vertical burning test, and its peak heat release rate and total heat release were reduced to 436 kW/m2 and 55.5 MJ/m2, respectively. Moreover, the FR-TPU presented the tensile strength of 25.45 MPa and elongation at break of 588.3 %. Morphological observation demonstrated that the combination of AHP and MCA significantly enhanced the compactness of residual char for FR-TPU. In this case, the compact char layer could effectively inhibit the mass and heat transfer of combustion area, thus enhancing the fire safety of the composites.

Mechanical Properties of Polylactic Acid/Modified Particleboard Flour Wood-plastic Composites

2019, 33 (5): 37-42; DOI: 10.19491/j.issn.1001-9278.2019.05.007

Abstract ( 504 )

A chemical modification was conducted for particleboard flour (PBF)by using alkali (NaOH) and perhydrol (H2O2) or isocyanic acid (IPDI), and then the polylactic acid (PLA)/PBF composites were prepared by melt extrusion. The effects of chemical modification and PBF content on the mechanical properties of the composites were investigated extensively. The results indicated that the interfacial compatibility between the PLA matrix and PBF was improved after PBF was chemically treated with a mixture of NaOH with H2O2 or IPDI, therefore leading to an improvement in the mechanical properties of the composites. The flexural strength and tensile strength increased by 21.63 % and 19.53 %, respectively, for the composites containing 20 wt% of PBF. Based on the results in this work, the composites could achieve the optimum mechanical properties when 20 wt% of PBF treated with a mixture of NaOH with H2O2was incorporated.

Preparation and Properties of Polyurethane-based Soft Foams Grafted with Hydroxyl-modified Multi-walled Carbon Nanotubes

2019, 33 (5): 43-48; DOI: 10.19491/j.issn.1001-9278.2019.05.008

Abstract ( 442 )

The surface hydroxylation of multi-walled carbon nanotubes (MWCNT)was conducted and then grafted with polyurethane to prepare soft composite foams by in-situ polymerization. To improve the interfacial interaction between MWCNT and polyurethane, an ultrasonic treatment was carried out to make MWCNT well dispersed in polyether polyols. The results indicated that the pores of polyurethane foam kept a stable shape with a uniform distribution and small size at the content of MWCNT lower than 0.4 wt%. A membrane structure was observed between the reticular foam walls. The bubble became larger and even collapsed when the content of MWCNT is higher than 0.6 wt%, The resilience, tensile strength and elongation at break of the composite foams exhibited an increasing trend at first and then tended to decrease with an increase of MWCNT content. The adsorption capacity of the composite foams was also influenced by the introduction of MWCNT, and their adsorption molar mass of strong polar water decreased with an increase of MWCNT content. However, there was an opposite trend for the adsorption molar mass of non-polar petroleum ether.

Influence of Injection Molding Parameters on Pressure Distribution of Cavity

2019, 33 (5): 49-55; DOI: 10.19491/j.issn.1001-9278.2019.05.009

Abstract ( 833 )

Cavity pressure curve is a comprehensive index for product quality. In this paper, the effects of mold and melt temperatures and holding pressure on the pressure at each point in the cavity was discussed, and the coincidence rate of pressure curve at each point was investigated by using the time-pressure curve of each point. Furthermore, the relationship between the pressure distribution at different points in the mold cavity and the quality of final products was analyzed. The simulation and experimental results indicated that the closer the pressure curves at each point, the better was the uniformity of product quality. The simulation calculation was conducted with a Moldflow analysis software which was commonly used in the injection-molding machine industry. The results obtained in this work provided an important reference for studying the change of cavity pressure and monitoring product quality to ensure a good product consistency.

Effect of Extrusion Processing on Residual Stress Distribution of Polyethylene Pipe

2019, 33 (5): 56-60; DOI: 10.19491/j.issn.1001-9278.2019.05.010

Abstract ( 423 )

The high density polyethylene(PE-HD) pipes with different residual stress were extruded under different cooling conditions, and the effect of extrusion processing on the physical properties and residual stress in the inner and outer layers of PE pipes were investigated. The results indicated that the longitudinal reversion rate of PE-HD pipes increased gradually with an increase of cooling rate, but their hydrostatic failure time and failure time of resistance to slow crack growth decreased simultaneously. On the other hand, the residual stress of outer layer increased gradually with increasing the cooling rate and enlarging the hole depth, which presented a non-uniform distribution. However, the residual stress of inner layer was relatively smaller and the non-uniform distribution was undistinguishable. The validity of the hole-drilling method for the residual stress test of PE-HD pipes was also confirmed by the tensile test results on the different layers of PE-HD pipes.

Precise Shape Control Technology and Mechanism of Self-lubricating Functional Liquid Membrane-assisted In-mold Micro Assembly Molding Process

2019, 33 (5): 61-66; DOI: 10.19491/j.issn.1001-9278.2019.05.011

Abstract ( 399 )

Aiming at the difficulty in the precise control for thermal-fluid-structure coupling deformation of permolded micro-component in the in-mold micro assembly molding process, an innovative precise shape control technology was proposed for the high-speed self-lubricating functional liquid membrane-assisted in-mold micro assembly molding.The results indicated that the high-speed self-lubricating functional liquid membrane-assisted in-mold micro assembly molding could make the thermal-fluid-structure coupling deformation of permolded micro-component controlled within a precision of several tens of micron, thus leading to a high precision for the in-mold micro assembly molding of polymeric micro mechanical system, Through a comparative analysis between the high-speed self-lubricating functional liquid membrane-assisted in-mold micro assembly molding and the traditional molding, the shape-control mechanism was exploited for the high-speed self-lubricating functional liquid membrane-assisted in-mold micro assembly molding.

Influence of Winding Angle on Mechanical Properties of Carbon Fiber Reinforced Composites Transmission Tower

2019, 33 (5): 67-72; DOI: 10.19491/j.issn.1001-9278.2019.05.012

Abstract ( 457 )

In this paper, material selection and filament winding design were proposed to improve the mechanical properties of composite transmission towers. The stress and deformation of glass fiber-reinforced plastic (GFRP) towers and carbon fiber-reinforced plastic ones under a standard test load were analyzed by a finite element method. The results indicated that the stiffness of the composite towers was effectively improved by the addition of carbon fiber, and their maximum displacement decreased by 20 %. On the basis of these results, the design of yarn spiral wound combined with one-way cloth longitudinal winding was proposed, and the equivalent moduli of composite towers were calculated at different winding angles. The influence of fiber orientation on the mechanical properties of carbon fiber-reinforced plastic towers was analyzed. The optimum angle of filament winding designed in this work was determined as 20 ° for the longitudinal winding angle and 50 °~55 ° for the spiral winding angle.

Study on Compression Performance of 2.5D-curved Shallow-crossing Linking Woven Composites

2019, 33 (5): 73-81; DOI: 10.19491/j.issn.1001-9278.2019.05.013

Abstract ( 489 )

In this work,a fiber bundle geometry model was established on the basis of the distribution of fiber monofilament. The geometric model of fabric structure was also established by observing the cross section and orientation of the inner impregnated fiber bundle within 2.5D shallow-crossing bending fabrics. For the convenience of analysis, some repeatable representative units were selected for the fiber bundle and fabric structure geometry models. The characteristic properties of material and the directions of each element were defined by using a custom program (UMAT), and the embedded periodic boundary conditions ensured the continuous stress and displacement at the boundary surface of the element. A damage analysis was conducted in the gradual progress based on an improved damage criterion and stiffness reduction model. The initial elastic modulus, final compressive strength and damage mechanism of the material were deeply understood through the experimental research and finite element analysis, and the warp compression was found to show no brittle failure.

Study on Effect of Citric-acid Hyperbranched Polyamide Leaching Agent on Removal of Heavy Metal From Soil

2019, 33 (5): 82-88; DOI: 10.19491/j.issn.1001-9278.2019.05.014

Abstract ( 487 )

Citric-acid hyperbranched polyamide was successfully prepared by melt polymerization using alkanolamide as a core and citric acid as a monomer and its chemical structure was characterized by 1H-NMR and FTIR spectroscopy. The effects of citric-acid hyperbranched polyamide on the removal of Zn, Cd and Pb from soil were investigated by batch experiments. The results indicated that the removal efficiency of Zn, Cd and Pb from soil was improved with an increase of contact time. When citric-acid hyperbranched polyamide was used as a washing agent at an concentration of 1.0 wt%, the maximum removal efficiency was achieved for Cd and Zn at pH=3 and for Pb at pH=4.5. Citric-acid hyperbranched polyamide as a leaching agent exhibited a better removal effect on heavy metals compared to normal citric acid. Moreover, citric-acid hyperbranched polyamide presented the extraction efficiency on removal of target heavy metals in an order of Pb>Cd>Zn, and however it showed less effect on the basic physical-chemical properties of soil.

Effect of Two-component Decrosslinking Agent on Recycling and Reuse of Waste Polyurethane Rigid Foam

2019, 33 (5): 89-93; DOI: 10.19491/j.issn.1001-9278.2019.05.015

Abstract ( 384 )

The waste polyurethane (PU) rigid foam was degraded by an alcohol-amine method, and then the renewed PU rigid foam was prepared by using recycled oligomer polyol. The viscosity and hydroxyl value of the recycled oligomer polyols were evaluated, and the resulting foam samples were analyzed by means of Fourier-transform infrared spectroscopy, density, water absorption, thermogravimetric analysis and polarized light microscopy. The results indicated that the chemical structure of the degradation product was quite similar to that of polyether 4110, a raw material for PU, at a DEG/ETA mass ratio of 1/3. The renewed foam samples exhibited a density of 35 kg/m3, water absorption of 0.016 g/cm3, compressive strength of 0.23 MPa and thermal conductivity of 0.021 6 W/m·K, which met the requirement for the national standards regarding PU foam.

Regulation Difference Analysis of Plastic Food Contact Materials and Products among China, Europe and the United States

2019, 33 (5): 94-101; DOI: 10.19491/j.issn.1001-9278.2019.05.016

Abstract ( 591 )

This article focuses on the management requirements, compliance test and product information transfer of plastic food contact materials and products and presents a comparative analysis of the composition of authority regulations, raw material management, product management, recycled plastic management, food classification and food simulators, migration test conditions, area of food contact and volume ratio of food simulators, conformity statement, label identification of plastic food contact materials and products among China, Europe and the United States at the current stage. We also proposed four suggestions for the construction of our domestic regulations. The aim of this article is to provide references for the formulation and revision of plastic food contact material and product regulations in our country.

Design of Large and Hot Runner Injection Mold for Car Rear Door

2019, 33 (5): 102-107; DOI: 10.19491/j.issn.1001-9278.2019.05.017

Abstract ( 360 )

In this work, we designed a large and hot runner injection mold of car rear door according to its structural characteristics and technical requirements. A reasonable gating system was determined on the basis of the mold flow analysis. The shrinkage problem was well solved by controlling the diameter of hot nozzle gate. The drawing and casting problem of hot nozzle and the gate residue were solved through separating the cooling channels around the hot nozzle. The results indicated that the molding cycle was controlled within 60 s, and the efficiency was improved by about 8 %, confirming that the mold structure was reasonable and advanced.

Design of Mold with Angled-lift Split Three-time Core Pulling Mechanism for Bracket Box Cover

2019, 33 (5): 108-114; DOI: 10.19491/j.issn.1001-9278.2019.05.018

Abstract ( 395 )

Aimed at the difficulties in the layout and demolding of plastic parts, a three-plate mold with a three-time core pulling mechanism was designed. For the layout of plastic parts in the mold cavity, the handle was arranged in the XY plane layout of the mold. Four types of mechanisms were designed for automatic demolding of plastic parts, which includes a angled-lift split core-pulling mechanism for stationary mold, a split core-pulling mechanism for movable mold, an angled-lift split three-time core-pulling mechanism for movable mold and a demolding mechanism with a sleeve ejector. For the design of angled-lift split three-time core-pulling mechanism, the first local core pulling was performed by driving the angled-lift split with inclined guide pillar. The second time-delay core pulling was conducted by driving an inclined ejector pin, an inclined angle lifter and an inclined ejector sleeve with the spring on the angled-lift split. The third time-delay core pulling was realized by means of the tie bar to lever set on the slider. The fractional core-pulling demolding was well performed by these mechanisms, which effectively ensured the quality of products during the plastic molding and automatic injection molding production processes, simplified the mould structure, and reduced the cost of the mold manufacturing. This design can bring a good reference for the design of the mold with a similar structure.

Review on Poly(ether-ether-ketone) Appropriative Resin and Its Application Development

2019, 33 (5): 115-120; DOI: 10.19491/j.issn.1001-9278.2019.05.019

Abstract ( 338 )

This paper introduced the major brands and typical properties of poly(ether-ether-ketone) (PEEK)appropriative resin from oversea manufacturers and also reviewedits application development. This paper provided useful references for relevant domestic enterprises to seize the global development trend in PEEK.

Research Progress in Intrinsic Self-repairing Polyurethane Materials

2019, 33 (5): 121-129; DOI: 10.19491/j.issn.1001-9278.2019.05.020

Abstract ( 635 )

This article reviewed the research progress in the intrinsic self-repairing polyurethane materials prepared by the introduction of reversible Diels-Alder bonds, the thermal initiation of reversible covalent disulfide bonds and the photoinitiation of ultraviolet and infrared rays. The mechanism of intrinsic self-repair was also discussed, and the development direction of self-repairing polyurethane materials was prospected.

Research Progress in Optimization Design for Conformal Cooling Channel of Injection Mold Based on 3D Printing

2019, 33 (5): 130-137; DOI: 10.19491/j.issn.1001-9278.2019.05.021

Abstract ( 446 )

The paper reviewed the technological development in the conformal cooling channel of injection mold and also introduced its design methods and space structures based on the 3D metal printing technique. The research progress in optimization design of the conformal cooling channel was introduced in detail, and the research direction in future was proposed.