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2019, Volume 33 Issue 1 Publication date: 26 January 2019 Previous Issue Next Issue

Study on Foaming Properties of Thermoplastic Polyolefin Elastomer with Supercritical CO₂

2019, 33 (1): 1-5; DOI: 10.19491/j.issn.1001-9278.2019.01.001

Abstract ( 888 ) PDF (1425 KB)( 478 )

Thermoplastic polyolefin elastomer (POE) foams were prepared by a batch kettle microcellular foaming technology using supercritical CO2 as a physical foaming agent. The effects of foaming temperature and saturation pressure on the apparent structure and morphology of POE foams were investigated by scanning electron microscopy. The results indicated that the foaming temperature and saturation pressure were the main factors that affected the structure and properties of the foams. The POE foams exhibited a low apparent density and a high expansion ratio when the saturation pressure was set as 10 MPa and the foaming temperature was set at 65 ℃. Under this condition, the POE foams achieved a large internal cell density and a uniform cell distribution.

Study on Synergistic Mechanisms of Flame-retardant ABS with Combination of Phosphate and Phenolic Resin

2019, 33 (1): 6-10; DOI: 10.19491/j.issn.1001-9278.2019.01.002

Abstract ( 997 ) PDF (1064 KB)( 501 )

The flame-retardant ABS was prepared by combination of phenolic resin (PF) with several types of phosphates such as triphenyl phosphate (TPP), bisphenol A bis(diphenyl phosphate) (BDP) and isopropylated triphenyl phosphate (IPPP). The effects of the type and dosage of phosphates on the flame retardant properties of ABS were investigated, and the flame retardant mechanisms were studied by FTIR and SEM. The results indicated that phosphates could affect the flame retardancy of ABS by physical interference at different loading but by chemical interference with different types. The chemical interference had a strong catalytic effect on physical interference.

Study on Morphology and Properties of Polypropylene/Liquid-Nitrogen-Cryogenic Rubber Powder Compounds

2019, 33 (1): 11-16; DOI: 10.19491/j.issn.1001-9278.2019.01.003

Abstract ( 548 ) PDF (1196 KB)( 482 )

The polypropylene (PP)-based compounds with liquid-nitrogen-cryogenic rubber powders (LNCRP) were prepared by melt extrusion, and their mechanical properties and morphologies were investigated. The result indicated that the addition of LNCRP resulted in a decrease in mechanical properties but an increase in notched impact strength. The incorporation of compatibilizer could lead to an improvement of mechanical properties. The notched impact strength and compatibility of the compounds were also improved with the addition of polyolefin thermoplastic elastomer (POE) and EPDM grafted with maleic anhydride. In addition, the impact resistance of the compounds could be further improved by using high-density polyethylene and POE as impact modifiers.

Study on Preparation and Crystallization of Polyoxymethylene/Poly(ethylene glycol)-Grafted Multiwalled Carbon Nanotubes Composites

2019, 33 (1): 17-23; DOI: 10.19491/j.issn.1001-9278.2019.01.004

Abstract ( 861 ) PDF (1051 KB)( 538 )

Poly(ethylene glycol) (PEG) was grafted onto multiwalled carbon nanotubes (MWNTs) by atom transfer radical polymerization, and its structure and performance of MWNTs-PEG was investigated with scanning electron microscopy,transmission electron microscopy,infrared spectroscopic and thermogravimetric analysis. The POM/MWNTs-PEG composite films were prepared by heat compression, and their crystallizations behaviors and non-isothermal crystallization kinetics were studied by differential scanning calorimetry using Jeziorny's and Mo's methods. The effect of MWNTs-PEG on the performance of composites was also investigated. The results indicated that PEG was successfully grafted onto MWNTs, and the presence of MWNTs-PEG generated a heterogeneous nucleation effect on the crystallization of POM. As a result, the crystallization temperature and crystallization rate were improved, and the crystallization time was shortened accordingly. The crystallization kinetic investigation indicated that the crystallization rate constant of POM/MWNTs-PEG composites increased but the F(T) value decreased. Moreover,the effective crystallization activation energy was reduced, suggesting a promoting effect of MWNTs-PEG on the crystallinity of POM.

Preparation and Flame-Retardant Properties of Flame-retarded PLA Composites

2019, 33 (1): 24-28; DOI: 10.19491/j.issn.1001-9278.2019.01.005

Abstract ( 1039 ) PDF (618 KB)( 535 )

Aluminum diethylphosphinate (ADP) was introduced into polylactide (PLA) to prepare a series of flame-retardant PLA composites (FR-PLA) by a melt-blending method. The effect of ADP on the thermal stability, flame retardancy and combustion property of FR-PLA were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning experiment and microscale combustion calorimetry (MCC). The flame-retardant test results indicated that the addition of ADP effectively enhanced the flame retardancy of FR-PLA, and a UL 94 V-0 classification and an LOI of 31.6 vol % were achieved when 30 wt % of ADP was added into PLA. TGA results revealed that the incorporation of ADP reduced the degradation temperature of FR-PLA but improved their char yields. MCC analysis showed that the addition of ADP reduced the peak heat release rate (PHRR) of FR-PLA significantly. The FR-PLA containing 30 wt % of ADP presented a PHRR value of 290 W/g, which decreased by 37.1 % compared to pure PLA. This result implied a significant decrease in the fire hazard of FR-PLA.

Study on Preparation and Performance of Thermoplastic Cross-linked Polyethylene

2019, 33 (1): 29-32; DOI: 10.19491/j.issn.1001-9278.2019.01.006

Abstract ( 708 ) PDF (298 KB)( 476 )

A new type of thermoplastic cross-linked polyethylene (TPEX) was prepared by crosslinking of PE-HD and PERT blends. This method not only maintained the thermoplasticity of PERT but also improved its heat resistance and creep resistance close to PEX due to partial crosslinking. TPEX gained the optimum comprehensive properties at a melt flow rate of 1~2 g/10 min and a crosslinking degree of (2±1) %, which met the requirement for processing and applications. TPEX also exhibited good heat resistance with a Vicat softening point of 126.1 ℃. The thermal strength and tensile creep properties of TPEX were characterized by thermal tensile strength at a given elongation and dynamic mechanical analysis. The results indicated that TPEX had higher thermal strength than PERT and PEX but similar creep resistance with PERT and PEX.

Preparation and Flame-retardant Performance of Cellulose/Graphene Oxide Composite Aerogels

2019, 33 (1): 33-39; DOI: 10.19491/j.issn.1001-9278.2019.01.007

Abstract ( 721 ) PDF (1909 KB)( 497 )

To improve the flame retardancy of cellulose aerogels, graphene oxide (GO) nanosheets were employed as a flame retardant to prepare cellulose/GO composite aerogels by a simple freeze-drying method. Scanning electron microscopy implied that the optimum dosage of GO was 5 wt %in cellulose mucus, and GO was well dispersed in cellulose to form ordered three-dimensional porous aerogels under this condition. X-ray photoelectron spectrometry confirmed that the interaction between GO and cellulose was due to hydrogen bonding. The composite aerogels were well flame-retarded by GO at an optimum dosage of 5 wt %, and their combustion rate decreased to 0.57 mm/s from 5.67 mm/s of pure cellulose aerogel. Micro cone calorimetric resultsindicated that the peak heat release rate of the composite aerogelsdecreased by 57.7 % at the optimum dosage of GO compared to that of pure cellulose aerogel, suggesting a good flame-retardant effect. Theresidual char of the composite aerogels was found to become denser than that of cellulose aerogel, and their graphitization degree was enhanced due to the incorporation of GO nanosheets. In summary, the char yield of the composite aerogels was improved and their density and degree graphitization were enhanced due to the physical barrier effect and the catalytic charring capability of GO. As a result, the flame retardancy of the cellulose aerogels was improved effectively.

Effect of Structure Feature of Poly(VAc-DBM-AA-AMPS) Emulsion on Mechanical Properties of Cement Mortars

2019, 33 (1): 40-47; DOI: 10.19491/j.issn.1001-9278.2019.01.008

Abstract ( 444 ) PDF (1630 KB)( 488 )

The effect of poly(VAc-co-DBM-co-AA-co-AMPS) emulsion on the mechanical properties and durability of cement mortars were investigated by compression and tensile experiments. The results indicated that the salt tolerance of emulsion film was improved significantly by introduction of AMPS functional monomer. Meanwhile, the compressive strength of cement mortars was influenced greatly by the dosage of AMPS, and the cement mortars achieved a maximum value in compressive strength when poly(VAc-co-DBM-co-AA-co-AMPS) emulsion contained 2.0 g of AMPS. The salt resistance and freeze-thaw resistance of the modified cement mortar was improved remarkably compared to ordinary concrete. SEM observation indicated that the incorporation of polymeric emulsion could modify the pore-size distribution of cement mortars, and a network structure was formed to improve the interfacial zone between cement paste and aggregate accordingly.

Development and Research of Fused Deposition Modeling 3D Printer Based on Conical Screw Extrusion Unit

2019, 33 (1): 48-52; DOI: 10.19491/j.issn.1001-9278.2019.01.009

Abstract ( 556 ) PDF (1238 KB)( 498 )

In this paper, a desktop fused deposition modeling (FDM) 3D printer based on the conical screw extrusion unit was successfully developed. A conical screw was adopted to prepare the polymer melts and strips for the formation of 3D printed products by cooperating with the movement of printing platform. The extrusion performance of the printer was investigated by using PLA and PE-HD, and the effects of impulse frequency, filament spacing and layer thickness on the properties of PLA tensile specimen were investigated. The results indicated that the home-made FDM printer exhibited good printing performance, and suitable parameters can provide good apparent qualities and tensile properties for the printed parts. Nevertheless, the larger filament spacing reduced the tensile strength by about 20%.

Study on Effect of Mold Temperature on PP-Foam Injection-Molded Products Based on Moldex3D Analysis

2019, 33 (1): 53-58; DOI: 10.19491/j.issn.1001-9278.2019.01.010

Abstract ( 601 ) PDF (2243 KB)( 495 )

The PP-foamed injection-molded products were processed by a microcellular foaming injection-molding method, and the effect of mold temperature on the mechanical properties and cell structure of the products were investigated by scanning electron microscopy, bending strength, impact strength and surface roughness. The results indicated that the cells of the products became denser with an increase of mold temperature, which led to an improvement in bending and impact performance but a decrease in surface roughness. The average diameter, density and dimensional standard deviation of the cells were simulated by a Moldex3D software, and the simulation results indicated that the standard deviation of cell size decreased with an increase of mold temperature, and the cell distribution also became more uniform. Moreover, the simulation also confirmed that that the trend in variation of mold temperature and weight loss ratio of cell was in a good agreement with the experimental results.

Study on Preparation and Properties of Polypropylene/Carbon Nanofiber Composites by Mircocellular Injection Molding

2019, 33 (1): 59-64; DOI: 10.19491/j.issn.1001-9278.2019.01.011

Abstract ( 676 ) PDF (2459 KB)( 409 )

The polypropylene (PP)/carbon nanofiber(CNF) composites were prepared by a melt-blending method, followed by microcellular injection molding, and the effect of CNF on the properties of the composites. The results indicated that the microporous size decreased significantly with an increase of CNF content, but themicroporous density increased. Moreover, the tensile strength and modulus of conventional injection-molded composite samplesdecreased slightly in the presence of CNF, but the microcellular injection-molded ones seemed to present an opposite trend.

Study on Movable Characteristics of Micro-Mechanical Rotating Motion Pairs for In-Micro Mold Assembly

2019, 33 (1): 65-71; DOI: 10.19491/j.issn.1001-9278.2019.01.012

Abstract ( 387 ) PDF (1968 KB)( 460 )

The cooling and shrinkage induced self tightening contact characteristics of polymer micro-mechanical rotating motion pairs made by in-micro mold assembly plays a key role in controlling the factor of their movable performance. The prediction and accurate control of self-tightening contact characteristics is a technical key for in-micro mold assembly.Based on the thermo-viscoelastic-plastic constitutive relation obtained from experiments,a simulation method was established for the micro assembly interfacial self-tightening thermal viscoelastic-plastic contact characteristics of the motion pairs during the molding process.The simulation results indicated that the maximum magnitude of interference, the clearance magnitude and the driving friction resistance torque of the micro assembly interface had a linear positive correlation with the secondary molding injection temperature. The reduction of the secondary molding injection temperature effectively improved the micro assembly interfacial fitting precision of micro mechanical motion pairs and also greatly reduced the minimum driving friction resistance torque to make the micro mechanical rotating pairs achieve the movable performance. When the secondary molding injection temperature decreased from 503 K to 463 K, the driving friction resistance torque of motion pairs decreased by 34.9 % from 3.61 N·mm to 2.35 N·mm.

Preparation of Light-Diffusing Polycarbonate for Lighting LED Lampshades and Lamp Tubes

2019, 33 (1): 72-77; DOI: 10.19491/j.issn.1001-9278.2019.01.013

Abstract ( 486 ) PDF (825 KB)( 629 )

Silicone crosslinked microspheres were prepared and their optimal preparation technology was developed. A type of light-diffusing polycarbonate (PC) resin for LED lampshades and lamp tubes was prepared by compounding PC with the resulting microspheres through directly melt blending and melt blending with masterbatch, and its performance was investigated. The results indicated thatthe haze of PC was improved but its high light transmittance was maintained when 0.15 wt % of light diffusing agent was added. However, its impact strength decreased due to the presence of light diffusing agent.Moreover, the masterbatch process was found to be more effective than the direct melt-blending method. The anti-aging property of light-diffusing PC was significantly enhanced due to the presence of UV absorber.

Effect of Anti-aging Agent on Thermal Aging Properties of PCL/WF Composites

2019, 33 (1): 78-86; DOI: 10.19491/j.issn.1001-9278.2019.01.014

Abstract ( 545 ) PDF (1364 KB)( 545 )

The effects of antioxidants, anti-hydrolytic agents and heat stabilizers on the thermal aging properties of PCL/white poplar fiber (WF) composites were investigated by mechanical property measurements, infrared spectroscopy, SEM observation and XRD analysis. The results indicated that the addition of antioxidant (BHA), anti-hydrolytic agent and heat stabilizers could effectively retard the thermal aging of PCL/WF composites. The optimum contents of additives could be determined as 4 wt % of antioxidant, 4.5 wt % of anti-hydrolytic agent and 2 wt % of heat stabilizer. A synergistic anti-aging effect was achieved in the presence of more than one anti-aging agent.

Effects of Hydrotalcite Dispersant on Particle Size and Core Loading of Thermal Expansion Microcapsules

2019, 33 (1): 87-92; DOI: 10.19491/j.issn.1001-9278.2019.01.015

Abstract ( 525 ) PDF (1247 KB)( 632 )

Thermal expansion microcapsules based on an n-hexane core and a polymeric shell were synthesized through suspension polymerization with hydrotalcite as a dispersant. The thermal expansion effect could be obtained from the evaporation of core materials after the microcapsules were heated to soften the shell. The morphology, particle size and selling properties of microcapsules were characterized by scanning electron microscopy, thermogravimetric analysis and static thermal analyzer, andthe effect of hydrotalcite content on the particle size and core loading of microcapsules were investigated. The results indicated that the microcapsules exhibited a regular morphology with a smooth surface and an average particle size of 11 μm when 5 wt % of hydrotalcite was added. The microcapsules also achieved an improved thermal expansion property with a dmax value of 750 μm when 16 wt % of foaming agent was loaded.

Interface Control and Performance of Polylactide/Graphene Oxide Nanocomposites

2019, 33 (1): 93-97; DOI: 10.19491/j.issn.1001-9278.2019.01.016

Abstract ( 529 ) PDF (1041 KB)( 471 )

Graphene oxide (GO) was firstly modified with ethylenediamine (EDA), dodecylamine (DA) and octadecylamine (ODA), and then functionalized graphene oxide (FGO) / poly (lactic acid) (PLA) nanocomposite films were prepared by hot pressing. The effects of GO-g-EDA, GO-g-DA and GO-g-ODA on the interfacial properties, mechanical properties, thermal stability and oxygen resistance of nanocomposites were studied. The results show that the combination property of composites is mainly depended on the chain length of the grafted molecular. the performance of composite filled with GO-g-ODA is superior to that filled with GO-g-EDA and GO-g-DA fillers . With addition of 0.5wt% GO-g-ODA loading, the tensile strength and elongation at break reach a maximum of 88.52MPa and 9.68%; the oxygen permeability coefficient decreased from 4.21×10-13 to 1.172×10-14 cm3cm/(cm2?s?Pa), about 97.2% decline. In addition, the thermal stability of PLA is also improved with the presence of functionalized graphene oxide.

Design of Injection Mold Base on Hot Runner for Energy Saving Rings

2019, 33 (1): 98-101; DOI: 10.19491/j.issn.1001-9278.2019.01.017

Abstract ( 541 ) PDF (2007 KB)( 344 )

According to the structural features of the plastic part and the molding characteristics of a combination of “metal powders + ABS”, an injection mold based on hot runnerwas designed for energy saving rings. The reasonable mold structure was determined on the basis of the investigation on the formed part, gating system, side-core pulling mechanism and temperature control system, Through the use of a hot runner gating system, and a cooling water channel based on straight pipe and septate well, the part achieved a dimensional tolerance within a basic dimension of±0.4 %, and their tolerance of angle and surface roughness reached 0.5° and Ra0.8 μm, respectively.

Design of IMR Injection Mould for Notebook Computer Cover

2019, 33 (1): 102-107; DOI: 10.19491/j.issn.1001-9278.2019.01.018

Abstract ( 845 ) PDF (2654 KB)( 561 )

An in-mould reprint (IMR) injection mould with hot runner was designed for the notebook computer cover on the basis of the analyses of the IMR process and cover structure. A set of film positioning, sealing, adsorption and mobile mechanisms were designed according to the analysis of the IMR technology. Moreover, a reasonable mould structure was determined in terms of the analyses of the molded parting surface, gating system, side core-pulling mechanism, and exhaust and cooling systems. The characteristic design for the moving and fixed mould flip-mold structure, hot runner, offset fan gate and slanted ejector pin not only increased the product quality and production efficiency, but also reduced the production cost. The design reported by this work provides a good reference for the similar mould design.

A Design and Analysis of Rotationally Molded Water Storage Tank in Free Drop

2019, 33 (1): 111-115; DOI: 10.19491/j.issn.1001-9278.2019.01.020

Abstract ( 581 ) PDF (1391 KB)( 516 )

To realize a supply of drinking water and oil for field forces and emergent rescuers, this article reported a design and development of rotation molding technology for a water storage tank in free drop. A type of liquid storage equipment with a free-dropping and easy-carrying capability was designed and then a reasonable scheme including the structure, shape, materials and molding process design was proposed to meet the requirement of practical applications. The feasibility and reasonability of the scheme were verified by theoretical analysis and practical airdrop test. The results indicated that the structure, materials, technology and performance of the rotation-molded water storage tank in free drop met the requirement of free drop for liquid, and there is no leakage of liquid for normal use of airdrop. It is concluded that the water storage tank in free drop developed by this work is a new type of practical, convenient and economical airdrop equipment that is suitable for practical use.

Research Progress in Pultrusion of Fiber-reinforced Resin-based Composites

2019, 33 (1): 116-123; DOI: 10.19491/j.issn.1001-9278.2019.01.021

Abstract ( 716 ) PDF (1736 KB)( 1338 )

This article reviewed the research progress in the pultrusion process and technology of fiber-reinforced thermosetting and thermoplastic composites, and also introduced the types of polymers suitable for pultrusion. The research progress in theoretical modeling and process optimization of pultrusion with mathematical simulation was discussed in detail. In addition, several novel pultrusion technologies, including braiding-winding-pultrusion and bending pultrusion, were introduced. With the advantages of reusability and recyclability, the continuous fiber-reinforced thermoplastic composites exhibit good development prospect in the field of pultrusion.

Research Progress in Polyethylene Microcellular Foams

2019, 33 (1): 124-132; DOI: 10.19491/j.issn.1001-9278.2019.01.022

Abstract ( 865 ) PDF (1443 KB)( 745 )

This paper reviewed the basic theory and research progress in the preparation of polyethylene microcellular foams, which included the dissolution and diffusion processes, rheological properties, and bubble nucleation and bubble growth processes. Taking the application for insulation materials as an example, some suggestions were proposed to improve the performance of insulation materials through the materials selection and bubble control.

Organic Modification of MMT and Its Applications in PLA

2019, 33 (1): 133-146; DOI: 10.19491/j.issn.1001-9278.2019.01.023

Abstract ( 687 ) PDF (6016 KB)( 413 )

This paper introduced the primary organic modification andsecondary organic modification of montmorillonite (MMT), and the applications of modified MMT in poly(lactic acid) (PLA) were highlighted. A number of studies indicated that the secondary modification could effectively improve the dispersion of organically modified MMT (OMMT) in the PLA matrix and alsomake it possible to form an exfoliation structure. The addition of OMMT could also effectively enhance the crystallization performance, tensile modulus, impact strength, thermal stability, barrier properties and rheological behavior of PLA.