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2019, Volume 33 Issue 8 Publication date: 26 August 2019 Previous Issue Next Issue

Preparation and Electromagnetic Interference Shielding Performance of Polyphenylene Sulfide/Graphene Nanoplates Composites with Segregated Structure

2019, 33 (8): 1-5; DOI: 10.19491/j.issn.1001-9278.2019.08.001

Abstract ( 572 )

The graphene nanoplates (GNPs) were used as a type of conductive filler and coated onto the surface of polyphenylene sulfide (PPS) granules through high-speed mixing, and then the PPS/GNPs composites with a segregated structure were fabricated by compression molding. The morphology, electrical properties and electromagnetic interference shielding performance of the composites were investigated by use of optical microscope, scanning electron microscope, electrometer and vector network analyzer. The results indicated that there was a perfect segregated structure formed within the composites. With such a segregated structure, the composites exhibited outstanding electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE). The composites achieved an electrical conductivity of 25.6 S/m and a high EMI SE of 41.0 dB when 3.0 wt% GNPs was incorporated.

Preparation and Properties of PP/Bronze Powder Composites

2019, 33 (8): 6-11; DOI: 10.19491/j.issn.1001-9278.2019.08.002

Abstract ( 653 )

The silane coupling agent K570, liquid paraffin, PP, bronze powder were blended and granulated by a screw extruder, and dumbbell-like splines of different bronze powder contents were prepared by an injection molding machine. The thermal properties, morphology, mechanical properties and dielectric properties of the spline were analyzed by differential scanning calorimeter, field emission scanning electron microscope, universal strength machine and dielectric constant meter. The results show that with the increasing content of bronze powder, the crystallinity, breaking strength and elongation at break increase first and then decrease. When the content of bronze powder is 1.5 %, the breaking strength reaches a maximum of 49.98 MPa; when the content is 2 %, the elongation at break rises to the highest point of 426.3 %; in the ultrashort wave frequency range of 3.1×108~4.1×108 Hz, when the amount of bronze powder is 2 %, the real part of the dielectric constant of the spline is highest.

Study on Enhancement of Heat Resistance for PMMA Resin with α-methylstyrene

2019, 33 (8): 12-17; DOI: 10.19491/j.issn.1001-9278.2019.08.003

Abstract ( 852 )

A series of poly(MMA-co-AMS) copolymers were synthesized with different proportions of methyl methacrylate (MMA) and α-methylstyrene (AMS) by free radical polymerization at 130 ℃. The composition, molecular weight, heat resistance and thermal stability of the obtained products polymer were investigated by means of nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis. The effect of AMS monomer on the copolymerization composition, molecular weight, heat resistance and thermal stability of poly(MMA-co-AMS) copolymer was also evaluated. The results indicated that the poly(MMA-co-AMS) copolymer with a high molecular weight and narrow molecular weight distribution could be synthesized by free-radical polymerization at high temperatures. The addition of AMS comonomer could improve the heat resistance of PMMA resin significantly. The copolymer containing 10.7 wt% of AMS segment achieved a glass transition temperature of 132.6 ℃ with addition of. The addition of the AMS comonomer could also decrease the temperature for open-chain depolymerization and lead to deterioration in the thermal stability of PMMA resin.

Comparative Study on Properties of Waste Paper/Wheat Straw-reinforced PE-HD Composites

2019, 33 (8): 18-23; DOI: 10.19491/j.issn.1001-9278.2019.08.004

Abstract ( 601 )

The high-density polyethylene (PE-HD)/waste paper (WP) and PE-HD/wheat straw (WF) composites were prepared by an injection molding method. The effects of contents of WP, WF and silane coupling agent (KH570) on the properties of the composites were investigated, and the mechanical, water absorption and interfacial properties of the composites were also analyzed comparatively. The results indicated that the mechanical properties of the composites increased first and then tended to decrease with the addition of WP and WF, and the optimum contents of WP and WF were 20 wt% nd 30 wt%, respectively. The addition of KH570 improved the interfacial compatibility and mechanical properties of the composites, but there was a decrease in water absorption performance. The optimum content of KH570 for PE-HD/WP and PE-HD/WF composites were 1 wt% and 2 wt%, respectively. The aspect ratios of WP and WF were determined as 24.2/1 and 12.5/1, respectively. When 20 wt% of WP and WF was incorporated, the mechanical properties, water absorption and interface properties of the PE-HD/WP composites were better than those of the PE-HD/WF composites.

Study on Branch Structure of Polyethylene Specially Used for Geomembranes

2019, 33 (8): 24-31; DOI: 10.19491/j.issn.1001-9278.2019.08.005

Abstract ( 604 )

Two commercial high-density polyethylene (PE-HD) materials specially used for geomembranes, TR131 and DQTG3912, were investigated comparatively in terms of their mechanical properties and chain structure. The HT 13C-NMR characterization result demonstrated that DQTG3912 had more short chains than TR131. The crystallinity of TR131 was analyzed by means of temperature rising elution fraction and successive self-nucleation and annealing, and the results indicated that TR131 had a lower degree of crystallinity. TR131 was found to have a higher relative content of low temperature fractions that DQTG3912, indicating a higher content of short-chain branching (SCB). DQTG3912 has less SCB at the low molecular weight parts but more SCB at the high molecular weight parts, which facilitated the formation of tie molecules and therefore improved its mechanical properties and resistance to environmental stress crack. The mechanical characterization results of DQTG3912 show good agreement with the analysis of its chain structure.

Preparation and Mechanical Properties of Polyamide 6 Composites Co-reinforced with Inorganic Particles and Carbon Fiber

2019, 33 (8): 32-37; DOI: 10.19491/j.issn.1001-9278.2019.08.006

Abstract ( 443 )

To understand the effect of inorganic particles (IP) on the mechanical properties of polyamide 6/carbon fiber (CF) composites, the polyamide 6/IP and polyamide 6/IP/CF composites were prepared by melt-extrusion and laminated molding, respectively. The effects of morphology and content of IP on the properties of the composite were investigated by means of field-emission scanning electron microscope and universal testing machine. The results indicated that the composites achieved optimum mechanical properties at the talcum content of 10 wt%, and their bending strength, shear strength and impact strength reached 374.6 MPa, 58.7 MPa and 76.9 kJ/m2, respectively. The composites also obtained excellent mechanical properties at the content of glass beads of 15 wt%, and their bending strength, shear strength and impact strength reached 404.4 MPa, 66.7 MPa and 86.5 kJ/m2, respectively. Compared to talcum powders, glass beads could generate a much better reinforcement effect and resulted in better comprehensive mechanical properties for the composity.

Influence of Wall Thickness on Hoop Tensile Strength of PVC Pipes

2019, 33 (8): 38-43; DOI: 10.19491/j.issn.1001-9278.2019.08.007

Abstract ( 657 )

In this paper, the hoop tensile strength of rigid polyvinyl chloride (PVC-UH) pipes was measured by a hoop tensile experiment, and the effect of thick wall on the hoop tensile strength of the PVC-UH pipes with a large diameter. The results indicated that there was a great effect of wall thickness on the PVC-UH pipes with the large diameter in the range of 19.5~45.9 mm. The results obtain from this work can give a guide for determination of the hoop tensile strength of PVC-UH pipes with different large diameters. Moreover, the influence factors for the hoop tensile strength of PVC-UH pipes were also discussed.

Synthesis of Melamine Polyphosphate Hybrid and Its Application for Flame Retardancy of Polyamide 6

2019, 33 (8): 44-48; DOI: 10.19491/j.issn.1001-9278.2019.08.008

Abstract ( 633 )

Melamine phosphate hybrid (CNMP) was synthesized by liquid phase reaction using melamine, phosphoric acid and graphitic carbon nitride (g-C3N4) as raw materials, and then a solid phase thermal condensation reaction was conducted for CNMP to obtain final product, melamine polyphosphate hybrid (CNMPP). The structure and thermal properties of the final product were characterized. The flame retardant polyamide 6 (FRPA6) was prepared by using CNMPP, and its flame retardant performance of FRPA6 was evaluated by vertical burning test, limiting oxygen index (LOI) test and glow-wire test. The results indicated that CNMPP achieved a better thermal stability than melamine polyphosphate (MPP). CNMPP obtained an increase in initial decomposition temperature at a weight loss of 5 wt% by 8.5 ℃, and its char yield was also improved from 34.1 wt% to 60.2 wt% at 650 ℃. The hybridization of MPP with g-C3N4 further improved the flame retardant performance of polyamide 6. With the addition of 30 wt% CNMP with a low hybridization level, the resulting FRPA6 achieved shorter self-extinguishing time than that with MPP. The FRPA6 also achieved a UL 94 V-0 classification rating, and its LOI value was improved from 24.2 vol% to 29.5 vol%. Moreover, the glow-wire ignition temperature of FRPA6 increased as well. However, the flame retardant performance of FRPA6 became deteriorated when the CNMPP with a high hybridization level was incorporated.

Analysis of Shrinkage Optimization of UNCRIMS Materials Based on Moldflow

2019, 33 (8): 49-55; DOI: 10.19491/j.issn.1001-9278.2019.08.009

Abstract ( 838 )

The Moldflow software usually cannot be used to simulate the shrinkage of the UNCRIMS (uncorrected residual stress) materials. In this work, we took the 19-inch LCD front frame made of UNCRIMS as an example for case study. In general, 0.5 % of shrinkage rate was adopted for design of the injection mold in accordance to the normal design experience. However, the serious surface shrinkage of the product was observed during the molding test. The shrinkage of injection-molded part can be solved by modifying holding parameters. When the size of parts is too large to meet the assembly requirements, and the mold will be invalidated. In order to ensure a success for redevelopment of mold, four pressure-holding programs were taken by the Moldflow software to find a method for calculating the shrinkage rate of UNCRIMS materials. By comparing the analysis of these programs comprehensively, the reasons for the failure of development of mold were found. In this case, a new program was taken, and the optimum shrinkage rate of the part was obtained. The CAE simulation was successful, and the injection-molded parts obtained from the redeveloped mold were found to be qualified.

Effect of Tensile Force Field on the Morphology and Properties of Polypropylene/Graphene Nanoplatelets Nanocomposites

2019, 33 (8): 56-62; DOI: 10.19491/j.issn.1001-9278.2019.08.010

Abstract ( 529 )

In this work, two kinds of extruder heads were designed to produce different processing force fields. The morphology and electrical and thermal conductivity of polypropylene (PP)/graphene nanoplatelets (GNPs) nanocomposites were investigated, and the effect of distribution of GNPs in the PP matrix on the performance of the nanocomposites was also studied. The results indicated that the tensile force field generated by the convergent flow channel had a peeling and dispersing effect on GNPs and therefore reduced the agglomeration of GNPs. The chaotic mixing force field generated by use of a static mixer further improved the dispersion uniformity of GNPs in the matrix, which facilitated the construction of an electrically conductive and thermally conductive network. As a result, the electrical and thermal conductivity of the nanocomposites was improved. For the nanocomposites containing 6 wt% of GNPs prepared by using a static mixer in the extrusion head, the conductivity was improved by 5 orders of magnitude and the thermal conductivity was improved by 24.1 % compared to the nanocomposites prepared without a static mixer.

Simulation Study on Temperature Uniformity of Air and Mould Wall Inside an Oven of Rotational Molding

2019, 33 (8): 63-68; DOI: 10.19491/j.issn.1001-9278.2019.08.011

Abstract ( 545 )

In this work, two heat transfer models were established for an oven of rotational molding with adjustable vanes inside its inlet. One was the so-called “model without mould”, in which there was no mould inside the oven. The purpose for establishing this model was to theoretically study the relation of temperature uniformity of air inside the oven with turning angles of vanes. The other one was so called “model with a mould”, in which the size and rotation of mould were considered. The purpose for establishing this model was to theoretically study the relation of temperature uniformity of mould wall with turning angles of vanes. Based on these two heat transfer models, the heating process of rotational molding was simulated numerically by means of the FLUENT software. It was concluded that the temperature uniformity of air inside the oven was optimum when both lower and upper vanes were set at the horizontal direction, and the temperature uniformity at the wall of 2 m long mould was optimum when the turning angles of upper and lower vanes were set as 0 ° and 20 ° respectively. In addition, the simulation study also demonstrated how the temperature uniformity of mould wall varied with the mould length when both the lower and upper vanes were set at the horizontal direction.

Study on Dispersion Performance Prediction of Pigment Based on BP Neural Network

2019, 33 (8): 69-75; DOI: 10.19491/j.issn.1001-9278.2019.08.012

Abstract ( 520 )

Based on the orthogonal experiment, the influence factors of color difference of plastic products were analyzed and discussed, and the data-prediction function of BP neural network was utilized to construct the prediction model of pigment dispersion performance. The results indicated that the factors affecting the color difference of plastic products were listed in an order of rotor speed > mixing time > mixing temperature. The increase of rotor speed could facilitate the dispersion and distribution of pigment particles in the plastic matrix, and the coloring quality of the product was improved accordingly. The relative error predicted by the BP neural network model did not exceed 10 %, and therefore this model could predict the dispersion performance of pigments in the plastic coloring process.

Preparation of Calcium/Zinc Triglycol Ester Acid Maleate Heat Stabilizer and Its Effect on Thermal Stability of PVC Products

2019, 33 (8): 76-82; DOI: 10.19491/j.issn.1001-9278.2019.08.013

Abstract ( 572 )

Triglycol ester acid maleate as an intermediate product was prepared by using five-ring maleic anhydride and triethylene glycol as raw materials and then reacted with calcium/zinc acetate to obtain a functional monomer with multifunctional groups. There are ester groups, carbonyl groups, ether bond and conjugated double bond in the molecules of maleic acid monotriethylene glycol ester. Afterward, a heat stabilizer was obtained by mixing maleic acid monotriethylene glycol ester with calcium/zinc salt. The content of metal ions was determined by titration with a standard solution of edetate disodium, and the chemical structure of the heat stabilizer was characterized by FTIR spectroscopy, and its thermal stabilizing effect on PVC was investigated by means of a thermal oven aging method, Congo red test, conductivity test and thermogravimetric analysis. Moreover, the synergetic stabilizing effect of this thermal stabilizer with β-diketone (Stearoyl benzoylmethane) was also evaluated. The results indicated that there was a good synergistic effect on enhancement of thermal stability when the mass ratio of calcium/zinc triglycol ester acid maleate was set to 1.5/1. The initial whiteness of the specimen could maintain 50 min, and the static thermal stability time reached 29 min, indicating that the heat stabilizer developed by this work has a better stabilizing effect than the normal calcium/zinc stearate one. An optimum stabilizing effect was achieved when 10 wt% of β-diketone added was added into this heat stabilizer.

Study on Pavement Performance of Rubber Powders-modified Asphalt Mixture

2019, 33 (8): 83-88; DOI: 10.19491/j.issn.1001-9278.2019.08.014

Abstract ( 444 )

The waste rubber powder-modified Asphalt can not only improve the pavement performance of the asphalt pavement, but also can solve the environmental pollution problem caused by waste tires. In the paper, the effects of three different factors such as rubber powder content, rubber powder number, and hydrogen peroxide on the pavement performance of the mixture are systematically investigated through a rutting test and freeze-thaw splitting test. The experimental results indicated that the high-temperature stability and water stability of the rubber powders-modified asphalt mixture can be enhanced by increasing the content and fineness of rubber powders; however the performance of the road is only improved little or even reduced after incorporating the excessive amounts of rubber powders. An optimum content of 21 % and optimum fineness of 250 μm are recommended for the rubber powders used. Moreover, hydrogen peroxide is also able to improve the high-temperature stability and water stability of the rubber powders-modified asphalt mixture.

Study on Effect of Recycled Materials on Properties of Polyethylene Raw Material Specially Used for Pipes and Its Products

2019, 33 (8): 89-94; DOI: 10.19491/j.issn.1001-9278.2019.08.015

Abstract ( 587 )

In this paper we investigated the differences of physical properties between the virgin and recycled polyethylene raw material specially used for pipe, and the effect of recycled PE on the properties of pipes was also studied. The results indicated that melt flow index, ash content, oxidation induction time and metal element content could be considered as effective indicators for identifying the virgin/recycled PE materials for pipes. Moreover, a mixing experiment was performed to prepare the compounds with different contents of typical recycled PE materials. The mechanical properties, antioxidant performance, metal contents and rheological behaviors of the compounds were evaluated intensively. The investigation showed that the presence of recycled PE material in the pipes or raw materials could be effectively distinguished by detecting the content of iron and calcium. The research results obtained from this work can be used for the revision of the standard specification for polyolefin plastic pipeline and will also make a contribution to the development of plastic pipeline industry.

Determination of Short Chain-chlorinated Paraffin in Plastic Toys

2019, 33 (8): 95-100; DOI: 10.19491/j.issn.1001-9278.2019.08.016

Abstract ( 589 )

A study on short chain-chlorinated paraffins (SCCPs) in plastic toys was conducted by means of a GC-MS detection technique, and the extraction temperature, procedure and solvent were optimized. The total ion current confirmation, qualitative and quantitative ion analyses and GC-MS detection for the content of SCCPs in plastic toys were also carried out. The results indicated that there was a good linear relationship for SCCPs, and its linear correlation coefficient for the calibration curves reached 0.999 9. The detection limit was in the range of 0.052 4~0.197 mg/L, and the recover rate reached 85.4 %~90.9 %. The chromatographic analysis for the SCCPs with three different chlorine contents could be used for the confirmation of chlorine species in SCCPs. This method is simple, rapid, highly sensitive and quantitatively accurate. The results indicated that this method could be used for the measurement of plastic toys contained 24.42~52.46 mg/kg of SCCPs.

Rapid Identification of Sole Materials with Mid-infrared Visible Spectroscopy

2019, 33 (8): 101-105; DOI: 10.19491/j.issn.1001-9278.2019.08.017

Abstract ( 568 )

In this paper, a model for identifying the type of common sole materials was established by means of mid-infrared analysis technology and chemometrics. This model can provided an effective new method for identification of the material type of soles. A hierarchical cluster analysis was conducted and a K-nearest neighbor model was set up on the basis of the infrared spectral matrix data of soles. The results indicated that 43 samples could be divided into 7 categories in the K-nearest neighbor model, which is consistent with the categorizing result that the average distance between groups was 8 in the hierarchical clustering. Under the K-nearest neighbor condition, the samples were distributed in five aggregation regions, among which H, G and K samples exhibited an obvious distribution. Compared to the class A, the distribution of class E was relatively concentrated, and the degree of convergence was larger. The class L and M were split into the class E and A, respectively. The total identification accuracy of the model reached 95.35 %, indicating an ideal categorizing result. In addition, one sample of each category was selected and analyzed with spectrogram. The main components of them were achieved as butadiene rubber, ethylene-vinyl acetate copolymer, polyurethane, isoprene rubber, polyvinyl chloride and styrene-butadiene-styrene block copolymer. In summary, the mid-infrared analysis technology combined with chemometrics can realize a non-destructive, rapid and accurate identification for common sole materials.

Design of Injection Mould for Outside Handle Cap of Right Front Door

2019, 33 (8): 106-111; DOI: 10.19491/j.issn.1001-9278.2019.08.018

Abstract ( 432 )

The structural manufacturability of the outside handle cap of right front door was analyzed, and the critical technical points and design ideas of the key mechanism of injection mould were introduced. According to the product structure, the gating system, forming parts, ejection mechanism, side core-pulling mechanism and cooling system of this mould are designed. In particular, the two-stage slide core-pulling mechanism is used to reasonably solve the technological problems in forming and core-pulling of the inclined holes. The mould is compact in structure and reliable in action, which can provide a reference for the design of injection moulds with a similar structure.

Design of Hot Runner Injection Mold for Controller Support Based on UG and NC Machining of Molding Parts

2019, 33 (8): 112-117; DOI: 10.19491/j.issn.1001-9278.2019.08.019

Abstract ( 622 )

Aimed at the requirements for bracket plastic parts forming, a design for their mold structure and part processing were carried out by the UG software under the integration of CAD. The layout of one mold and one cavity were adopted for the mold structure. The function action includes one times opening, two times ejection and four side-core pulling. The combination of hot runner and cold runner are adopted so as to meet the requirement of thin-walled area filling. A balanced piping system is used to ensure the temperature control of mold cavity. During the structural design of the mold, in the case of the demolding process with difficult demolding characteristics, four outer walls were driven by an integral double guide pillars slider mechanism for short-distance core-pulling demolding. As for the inner wall, an integral double-ejector oblique ejector block was used for core-pulling demolding. In the case of the screw column, the ejector tube is used for complete. Moreover, the ejector pin is used for complete demolding of the plastic parts. A second ejection control mechanism was designed for the ejection plate to realize the opening and closing of the two ejection plates by the movement of sliders. The errors caused by the transfer of intermediate data in the mold processing can be reduced by means of the integrated CAD design based on the UG software. This is advantageous for improving the accuracy of mold processing, effectively reducing the cost of mould production and shortening the manufacturing cycle of mold.

Design of Secondary Core-pulling Mechanism and Simplified Four-time Opening Three-platemould for Slider in Medicine Transit Box

2019, 33 (8): 118-126; DOI: 10.19491/j.issn.1001-9278.2019.08.020

Abstract ( 552 )

According to the structural characteristics of plastic parts, a simplified three-plate die with double parting surface and four-point gate was designed. On the basis of optimizing the ejection mode of plastic parts and optimizing the gating system of plastic parts with CAE, the mold cavity layout adopts one mold and one cavity. To solve the problem of difficult demoulding of plastic parts, a four-sided core-pulling compound mechanism was designed to realize automatic demoulding of plastic parts. With the opening action of the template, a compound four-sided core-pulling mechanism was designed to realize complete demoulding of plastic parts. When demoulding, the core-pulling of the core insert is separated from the plastic part by the opening action of the moving template and the fixed template under the ejection of the pneumatic ejection. At the same time, the core-pulling of the vertical core-pulling insert is driven by the slider of the central tunnel driven by the oblique T-groove, and then the side core-pulling of the vertical core-pulling insert is carried out downward by four sliders driven by two cylinders. At the same time, the plastic part is also assisted by the pneumatic ejection. When the part is pulled out, the plastic part is left on four downward core-pulling sliders. In the following four downward side core-pulling sliders, because the four sliders are driven by their respective oblique guide pillars, the side core-pulling is done synchronously, and the plastic part is automatically separated from the four side sliders, thus realizing the automatic demoulding of the plastic part. The mechanism design is ingenious and the die mechanism design is reasonable, which can provide useful reference for the die design of similar plastic parts.

Research Progress in Polymer Matrix Composites with Highly Thermally Conductive Network

2019, 33 (8): 127-135; DOI: 10.19491/j.issn.1001-9278.2019.08.021

Abstract ( 889 )

The thermally conductive mechanism of polymeric materials was introduced, and the current research status of thermally conductive polymer-based composites at home and abroad was reviewed. The type of thermally conductive polymers, including intrinsic-type thermally conductive polymers and filled-type thermal conductive polymers, were also analyzed. The filling methodology includes the single filler filling, mixed filler filling and double percolation structure filling methods. Finally, the types and methods of construct the thermally conductive network of polymer materials were introduced, and their future development was prospected.

Research Progress in Performance Evaluation Methods of Continuous Glass Fiber-reinforced Thermoplastic Composite Pipes

2019, 33 (8): 136-143; DOI: 10.19491/j.issn.1001-9278.2019.08.022

Abstract ( 746 )

This paper reviewed the development status of reinforced thermoplastic composite pipe (GFT-RTP) and also introduced their structure and application requirements in various fields. The failure modes and failure mechanisms of GFT-RTP were analyzed in the aspects of force, medium and time. The corresponding test items were given to support the healthy development of the GFT-RTP industry.