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2017, Volume 31 Issue 11 Publication date: 26 November 2017 Previous Issue Next Issue

Research Progresses in Supercritical Fluid Foaming of Polymer/Nanoparticles Composites

2017, 31 (11): 1-9; DOI: 10.19491/j.issn.1001-9278.2017.11.001

Abstract ( 472 )

This paper reviewed applications of nanoparticles in supercritical fluid foaming process for polymer nanocomposites as well as their effects on forming mechanisms of the nanocomposites. Effect of nanoparticles on bubble nucleation and growth of polymer foaming were discussed, and factors for the foaming process of polymer-based nanocomposites were analyzed. The trend in development of polymer nanocomposite foams was prospected.

Research Progress in Polymer Die Extrusion Process Using Finite Element Method

2017, 31 (11): 10-19; DOI: 10.19491/j.issn.1001-9278.2017.11.002

Abstract ( 556 )

This paper overviewed research progresses in numerical simulation of extrusion die application in the recent decade. Research findings in the numerical simulation of extrusion die, gas-assisted extrusion and co-extrusion were introduced in detail. The complex flow channel structure was considered as a difficulty for the design of profile dies, and a significant progress in the design of complex dies was achieved with the aid of Polyflow software. Compared with traditional extrusion, gasassisted extrusion and gas-assisted co-extrusion had more advantages for reducing die-swell ratio. Simulation of gas-assisted extrusion only provided a theoretical evaluation, and however, it was still in shortage of enough applications in large-scale industrialization. Polyflow software could approximately predict the location of interfaces for extrudates during simple die extrusion.

Research Progress in Blending Toughening Modification of PVC

2017, 31 (11): 20-26; DOI: 10.19491/j.issn.1001-9278.2017.11.003

Abstract ( 574 )

This article reviewed the recent research of blending toughening modification system of poly(vinyl chloride)(PVC) resin, including PVC/elastomer and PVC/rigid particle blends, and development of blending toughening modification of PVC was prospected.

Preparation and Performance of PBS-PBT-PDMS Copolymers

2017, 31 (11): 27-34; DOI: 10.19491/j.issn.1001-9278.2017.11.004

Abstract ( 377 )

An oligomer was prepared by the reaction of succinic acid with butyl glycol, and a series of copolymers were synthesized by use of the digomer, dimethyl terephthalate and silanol through melt polycondensation. Chemical structure, crystallization-melting behavior, thermal performance, morphology and mechanical properties of the resultant copolymers were characterized by 1H-NMR, 29Si-NMR, differential scanning calorimetry, thermogravimetric analyzer, scanning electronic microscopy and universal testing machine. The results indicated that the copolymers were constituted by PBS as a main chain, silane segments as a chain extender and tougher and PBT bulk as a reinforcement. They not only achieved a liner molecular structure with a high molecular weight but also obtained an improvement in mechanical properties and thermal stability. Moreover, the copolymers exhibited imperfect spherulites due to the fast crystallization rate and lower crystallinity. Owing to a highly flexible silane segment and a rigid PBT segment, the copolymers achieved an increase in tensile strength by a factor of 1.4～2.1, an increase in impact strength by a factor of 4～7, and an increase in elongation at break by a factor of 2～4.

Effect of Filler Shape on Thermal Conductivity of Polyamide

2017, 31 (11): 35-40; DOI: 10.19491/j.issn.1001-9278.2017.11.005

Abstract ( 546 )

Thermally conductive polyamide 6 (PA6)-based composites were prepared through a melt-blending method by use of expanded graphite (EG), boron nitride (BN), Al2O3, and zinc oxide whiskers (T-ZnOW) as functional fillers, and effect of filler shape on thermal conductivity of the composite was investigated. Furthermore, EG was used as a major thermally conductive filler to compound respectively with BN, Al2O3 and T-ZnOW so as to confirm the role of filler type in the improvement of thermal conductivity of the composites. The results indicate that EG had a better enhancing effect on the thermal conduction of PA6 matrix than the other three. As a small-size filler, Al2O3 can help to open the layers of the lamellar EG, thus forming a more perfect thermally conductive network and leading to a better synergistic effect accordingly. PA6-matrix composites achieved a maximum thermal conductivity of 3.05 W/(m·K) by 7.5 vol % of BN, 3.10 W/(m·K) by 5 vol % of Al2O3 and 2.84 W/(m·K) by 2.5 vol % of T-ZnOW in the mixed fillers with a total volume fraction of 20 vol %.

Performance of Polypropylene Modified by Ground Tire Rubber Through Mechanochemical Shearing Devulcanization

2017, 31 (11): 41-47; DOI: 10.19491/j.issn.1001-9278.2017.11.006

Abstract ( 410 )

Blends of polypropylene (PP) with devulcanization ground tire rubber (DGTR) were prepared by melt blending, and their impact performance, rheological properties and crystallization behaviors was investigated. Furthermore, reaction mechanisms between PP and DGTR were analyzed. The blend containing 15 wt % DGTR achieved maximum Izod impact strength of 8.5 kJ/m2, which was increased by 49.1% compared with that of pure PP. Based on the analysis of X-ray powder diffraction patterns, there are some β-type crystals of PP in the blends, and the amount of β-type crystals reached 11.2 % for the blend containing 30 wt % of DGTR. The change in morphology of the powder caused by desulphurization, which promotes the formation of β-type crystals.

Preparation and Properties of Superconductive Carbon Black/Poly(lactic acid) Antistatic Composites

2017, 31 (11): 48-52; DOI: 10.19491/j.issn.1001-9278.2017.11.007

Abstract ( 515 )

Superconductive carbon black (CB)/poly(lactic acid) (PLA) antistatic composites were prepared by a solution-blending method using PLA as a matrix, superconductive CB as a antistatic agent and chloroform as a solvent. The effect of CB content on the antistatic performance, thermal stability and mechanical properties of the composites were investigated by volume resistivity tests, thermogravimetric analysis and tensile tests. The results indicated that there was a percolation at CB content of 2 wt % for the composites, which resulted in a transformation from insulator to semiconductor. This complied with the antistatic requirement for the composites, whereas there was a slight decrease in mechanical properties. Meanwhile, the crystallinity and thermal stability of the composites were improved with the addition of superconductive CB, and their start degradation temperature was increased by 20.5 ℃ when 4 wt % of CB was incorporated.

Effect of Epoxybased POSS on Foaming Behavior of PLA/PBAT Blends

2017, 31 (11): 53-59; DOI: 10.19491/j.issn.1001-9278.2017.11.008

Abstract ( 350 )

Poly(lactic acid) (PLA)/poly(butyleneadipate-co-terephthalate) (PBAT)/polyhedral oligomeric silsesquioxane (POSS) composites and their foams were prepared by a melt-mixing method and a supercritical CO2 solid state foaming method, respectively. Thermal behavior, rheological property, and foaming behavior of the composites were studied. The results confirmed the plasticization effect of POSS particles on the composites. The rheological results indicated that melt elasticity of the composites was improved with the addition of POSS. As a result, cellular structure of the composites foams was enhanced. Cell density and foaming expansion ratio of the composite foams increased with an increase of POSS content. The composite foams achieved a cell density of 8.25×107 cell/cm3 and an expansion ratio of 13 at the POSS content of 7 phr. POSS was found to have a positive effort on controlling the cellular structure of the composite foams.

Preparation and Properties of Modified Polypropylene for Microfoamed Materials

2017, 31 (11): 60-65; DOI: 10.19491/j.issn.1001-9278.2017.11.009

Abstract ( 421 )

Expandable polypropylene (PP)-based resin was prepared for microfoam sheets by using homopolypropylene (PP-H) and block-copolymerized polypropylene (PP-B) through a melt-blending method, and effects of PP-H content on mechanical properties of microfoam sheets were investigated. In addition, foaming modifier and nucleating agents (calcium carbonate and talcum powder) were used to modify microfoaming behavior of PP resin, and effects of contents of foaming modifier and nucleating agents on foaming behavior of PP were also studied. The results indicated that the tensile strength of microfoam sheets decreased but their flexural strength increased with an increase of PP-H content. The foaming modifier improved the melt strength of PP. The density of microfoam sheets decreased but their cell density increased with increasing contents of nucleating agents. As an appropriate amount, 0.5 phr of nucleating agent was recommended for the microfoam sheets. The modified PP exhibited an increase in shear viscosity and extrusion expansion ratio, and however, its molecular weight distribution almost did not changed. These microfoam sheets were found to have a cell diameter less than 50 μm and a cell density up to 106 cell/cm3.

odification of Phenolic Foam with Epoxy Resin

2017, 31 (11): 66-71; DOI: 10.19491/j.issn.1001-9278.2017.11.010

Abstract ( 388 )

Phenolic foam (PF) was prepared by using thermosetting phenolic resin as a raw material, p-toluenesulfonic acid as a curing agent and epoxy resin as a modifier. Effect of the amount of epoxy resin on the properties of PF was investigated. The results indicated that the apparent density, compression strength, thermal conductivity and pH value of PF were all improved due to the modification of epoxy resin. When the amount of epoxy resin was increased from 2 wt % to 8 wt %, the modified PF exhibited a decreasing trend in apparent density, thermal conductivity and degree of powder but an increasing trend in thermal stability and pH value. However, its compression strength increased at first and then tended to decrease. The modified PF achieved the maximum comprehensive properties when 6 wt % of epoxy resin was introduced.

Properties and Preparation of Poly(lactic acid)/Straw Powder Composites

2017, 31 (11): 72-77; DOI: 10.19491/j.issn.1001-9278.2017.11.011

Abstract ( 406 )

Poly(lactic acid) (PLA)/corn straw powder composites was prepared by a solution casting method using PLA and corn straw powder as raw materials. Effects of raw material ratio and coupling agent type and content on chemical structure, interfacial compatibility, thermal stability and mechanical properties of the composites were investigated. The results indicated that mechanical properties of the composites increased at first and then tended to decrease with an increase of the content of corn straw powders. The composites achieved the maximum mechanical properties at the corn straw content of 20 wt %. The addition of silane (KH550) or titanate coupling agent could improve the compatibility between the corn straw powders and PLA and enhance the bonding between two materials, thus improving the thermal stability and mechanical properties of the composites but reducing their water absorption. The composites gained the optimum properties with the addition of 1.5 wt % of KH550 or 3 wt % of titanate coupling agent.

Preparation and Properties of Poly(vinyl chloride) Grafted with Dibutyl Maleate

2017, 31 (11): 78-83; DOI: 10.19491/j.issn.1001-9278.2017.11.012

Abstract ( 381 )

Poly(vinyl chloride) grafted with dibutyl maleate (PVC-g-DBM) was synthesized by using maleic anhydride grafted PVC (PVC-g-MAH) as a raw material and n-butanol as an esterification catalyst, and then PVC/PVC-g-DBM compounds were prepared by melt blending. Esterification conditions of PVC-g-MAH and properties of the compounds were investigated. The results indicated that dibutyl maleate had a plasticization effect on PVC. When the mole ratio of alkyd was set to 2.15, the weight fractions of catalyst and dehydrating agent were set to 3 wt %, and the reaction time was set to 4 h, the esterification rate of PVC-g-MAH could reach 91.07 %. Compared with pristine PVC, PVC/PVC-g-DBM compounds achieved an improvement in thermal stability, low temperature resistance, migration resistance, processing performance and mechanical properties.

Properties of Flameretardant and Smokesuppressive PBS Composites

2017, 31 (11): 84-89; DOI: 10.19491/j.issn.1001-9278.2017.11.013

Abstract ( 484 )

Flame-retardant poly(butylene succinate) (PBS) composites were prepared by melt blending using intumescent flame retardant (IFR) and modified basic magnesium sulfate whisker (MHSH), and their mechanical performance, flame-retardant properties and smoke suppression were investigated. The results indicated that the incorporation of MHSH could enhance the mechanical performance and flame retardancy of the composites. When the contents of IFR and MHSH were set as 23 wt % and 2 wt %, respectively, the composites achieved a LOI value of 39.8 vol % and UL 94 V-0 classification. Their tensile strength, bending strength and impact strength also increased by 33.33 %, 6.65 % and 21.80 %, respectively, compared with those of the composites only containing 25 wt % of IFR. The addition of MHSH could effectively reduce the total smoke release amount and the release rate of carbon monoxide and carbon dioxide for the composites due to its synergistic effect, thus reducing the fire risk of the composites.

Improved Design of Gas-assisted Co-extrusion Dies for Polymer Profile and Its Experimental Investigation

2017, 31 (11): 90-94; DOI: 10.19491/j.issn.1001-9278.2017.11.014

Abstract ( 385 )

This article reported a numerical simulation for the gas-assisted co-extrusion process of profiles with an L shape by a finite element method under the consideration of the gas layer as an actual flow. The simulation results indicated that the gas groove on the surface of the extrudates could be avoided when the gas entry location of the die was reasonably designed regardless of a high gas pressure. The gas-assisted co-extrusion die with an L-shaped profile was designed based on the previous studies and simulation results, and then an experimental investigation was carried out by use of the improved co-extrusion die. The experimental results confirmed that the gas groove on the surface of the extrudates could be avoided when the gas entry was located at a 5 mm position after the two melts converged. The experimental results were in good agreement with simulation results and also verified the rationality of the structure for this improved die accordingly.

Chain Extension of Poly(butylene succinate) and Its Foaming Behavior

2017, 31 (11): 95-101; DOI: 10.19491/j.issn.1001-9278.2017.11.015

Abstract ( 421 )

Poly(butylene succinate) (PBS) was modified by chain extension through reactive melt mixing in a torque rheometer using ADR-4370S as a chain extender. Molecular structure and thermal and rheological properties of the modified PBS samples were investigated by torque rheometer, gel content test, differential scanning calorimetry, and rotational rheometer. PBS foams were prepared by using supercritical carbon dioxide as physical blowing agent in an autoclave. Foaming properties of PBS foams were characterized by scanning electron microscopy and densimeter. The results indicated that there was structural change in PBS macromolecules from linear to branched or cross-linking structure due to the chain extension. The branched PBS foam could obtain an optimum cell morphology with the addition of 1.5 phr chain extender at foaming temperature of 105 ℃.

Liquefaction Behavior of PET Catalyzed by ［Pmim］OH Salt Ionic Liquids

2017, 31 (11): 102-107; DOI: 10.19491/j.issn.1001-9278.2017.11.016

Abstract ( 400 )

PET was degraded by using ionic liquid as a catalyst in a glycol solvent, and effects of reaction temperature, reaction time, catalyst dosage, and ethanediol/PET ratio on degradation reaction were investigated. The results indicated that the ionic liquid based on 1-butyl-3-methyl imidazole hydroxide (［Pmim］OH) could well catalyze the degradation reaction of PBS, and an optimum alcoholysis condition could be achieved for the degradation reaction at a reaction temperature of 195 ℃, a catalyst dosage of 2.5 wt %, an ethanediol/PET ratio of 4∶1 and reaction time of 3.5 h. Structures of the degradation products were also characterized by Fourier-transform infrared spectroscopy and mass spectroscopy, which was identified as 2-hydroxyethyl methyl terephthalate.

Additive

Preparation of Micabased Flame Retardants and Their Application in Polypropylene

2017, 31 (11): 108-113; DOI: 10.19491/j.issn.1001-9278.2017.11.017

Abstract ( 412 )

The encapsulated mica with zinc stannate(ZS/Mica) was prepared by a coprecipitation method, and then the resultant ZS/Mica was modified by KH550/paraffin wax and KH550/sebacic acid to form two types of mica-based flame retardants(P-ZS/Mica and S-ZS/Mica). X-ray powder diffraction, scanning electronic microscopy and electron energy spectroscopy were conducted to confirm the successful encapsulation of zinc stannate on the surface of mica particles. Such mica-based flame retardants were used to replace Sb2O3 in bromide-antimony flame-retardant polypropylene(PP) system. The results indicated that flame retardancy of the flame-retardant PP maintained unchanged but its thermal stability increased when half amount of Sb2O3 was substituted by P-ZS/Mica. However, the elongation at break, impact strength and flexural strength of the flame-retardant PP increased by 55 %, 32 % and 30 %, respectively. Moreover, the flame-retardant PP also showed a little change in peak value of heat release rate but gained a significant reduction in the amount of released smoke.

Preparation of Brominated Styrenebutadiene Rubber and Its Flame Retardant Effect on Polystyrene

2017, 31 (11): 114-118; DOI: 10.19491/j.issn.1001-9278.2017.11.018

Abstract ( 384 )

Brominated styrene-butadiene rubber (BSBR) was prepared by using dichloroethane as a solvent, SbCl3 as a catalyst and BrCl as a brominating agent. The effect of BrCl dosage on the bromine content of BSBR was investigated. Subsequently, BSBR was mixed with polystyrene by a solution method, and the effect of the bromine content of BSBR on the flame-retardant properties of PS composites was investigated by thermogravimetric analysis, limiting oxygen index (LOI) and cone calorimeter. The results indicated that BSBR achieved a maximum bromine atom percentage of 33.17 % when the dosage of BrCl was set as 70 mL. The introduction of BSBR could effectively improve the flame retardancy of PS. The higher the bromine content in BSBR, the better the flame-retardant effect on PS. As a result, a maximum LOI of 30.8 vol % was achieved for the flame-retardant PS. Moreover, LOI of the flame-retardant PS increased with an increase of BSBR content, but the total heat release of the combustion decreased. In addition, the release amount of CO increased due to incomplete combustion.

Study on Correlation of Natural Exposure and Artificial Accelerated Aging for Spray-free Polypropylene Material and Its Weathering Factors

2017, 31 (11): 119-124; DOI: 10.19491/j.issn.1001-9278.2017.11.019

Abstract ( 478 )

A comparative investigation was conducted on degradation behaviors of a spray-free polypropylene material between outdoor exposure at four national standard natural exposure places and indoor accelerated weathering under three typical artificial conditions. The correlation between the above two weathering behaviors was studied and the weathering factors were analyzed. The results indicated that there was no correlation observed in the color difference between the 12 month natural exposure at four testing places and the artificial accelerated weathering. However, a change in gloss for the tested specimens obtained from Qionghai and Lhasa indicated a good correlation with artificial accelerated weathering under the condition 1, and furthermore, the result from the natural exposure at Qionghai presented a much better correlation. The acceleration rate of laboratory weathering under the condition 1 was double in comparison with that from the outdoor exposure at Qionghai. UV irradiation and water were found to play critical roles in the weathering of spray-free polypropylene materials.

Effects of 3D Printing Parameters on Tensile Performance of PLA Printed Specimens

2017, 31 (11): 125-129; DOI: 10.19491/j.issn.1001-9278.2017.11.020

Abstract ( 517 )

The paper reported a study on the effect of key 3D printing parameters such as filling density, layer height, shell thickness and printing temperature on tensile strength and elongation at break of 3D-printed (PLA) specimens. The tensile strength and elongation at break of the printed specimens were found to increase with the increase of filling density. However, the elongation at break began to drop at a filling density of 100 %, because there was a structural transformation from space grid structure to the entity one for the printed specimens. Moreover, the elongation at break of the printed specimens increased with an increase of layer height, but their tensile strength trend to decrease. On the other hand, their tensile strength and elongation at break increased with an increase in shell thickness and shell thickness. When the print thickness was 1.2 mm, the elongation at break point began to decrease due to the entity structure of cross section in the printed specimens. The printed specimens achieve optimal mechanical properties when being printed in the temperature range of 210～220 ℃.

Structure Design of Core-pulling Mechanisms and Injection Moulds for Axle Covers

2017, 31 (11): 130-136; DOI: 10.19491/j.issn.1001-9278.2017.11.021

Abstract ( 375 )

This paper reported a structural design for point gate plate moulds with four times of mould parting and two times of ejection according to structure characteristics of the shaft sleeve cover cylinder plastic pieces with a ring groove on the inside and lateral convex ribs on the outside, which could realize the automatic injection-molding production. Furthermore, a differential driving inner core-pulling mechanism with an annular groove in the hexahedral T-shaped slot was designed according to the structure characteristics of ring grooves. The relationship between the geometric parameters of mechanism motion was modeled, and the equations for these movement parameters were given. For the convex rib composition on outer ring buckle, a “toggle-type” inclined top mechanism with guide block oriented by T-shaped slots and driven by the push rod was designed. The results indicated that structure of the designed mould was reasonable and the design of the mechanism was simple and reliable.