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2018, Volume 32 Issue 01 Publication date: 26 January 2018 Previous Issue Next Issue

Research Progress of Self-reinforced Plastic Pipes

2018, 32 (01): 1-6; DOI: 10.19491/j.issn.1001-9278.2018.01.001

Abstract ( 673 )

This article reviewed the research progresses in self-reinforced piping materials based on pipes of poly(vinyl chloride), polypropylene, high density polyethylene and ultra high molecular weight polyethylene. Definition, principles and superiorities of self-reinforcement of piping materials were introduced in detail, and application prospects of self-reinforced thermoplastic piping materials were described.

Progress in Poly(Propylene Carbonate)/Poly(Lactic Acid) Blends

2018, 32 (01): 7-14; DOI: 10.19491/j.issn.1001-9278.2018.01.002

Abstract ( 494 )

This paper reported an overview for the research progress in poly(propylene carbonate) (PPC)/poly(lactic acid) (PLA) blends. The compatibility, mechanical properties, thermal stability and degradability of PPC/PLA blends were introduced, and their degradation mechanisms were briefly presented. Application prospects and characterization methods of PPC/PLA blends were also recommended.

Research Progress in Crystallization Behavior of Polymers by Online Method Using Rotating Rheometers

2018, 32 (01): 15-20; DOI: 10.19491/j.issn.1001-9278.2018.01.003

Abstract ( 728 )

This paper overviewed the recent research progresses in crystallization behaviors of polymers by an online method using a rotary rheometer. Operation principle of this method was introduced and its application prospects were also presented.

Study on Non-isothermal Crystallization Kinetics of PE-HD/PE-UHMW Blends

2018, 32 (01): 21-26; DOI: 10.19491/j.issn.1001-9278.2018.01.004

Abstract ( 665 )

Nonisothermal crystallization behaviors of PE-HD/PE-UHMW blends were investigated by differential scanning calorimetry, their crystallization kinetics were analyzed by Jeziorny’s and Mo’s methods, and their crystallization activation energy was evaluated by Kissinger’s and Takhor’s methods. The results indicated that PE-UHMW could act as a nucleating agent to provide more activated nuclei for the crystallization of PE-HD and thus enhance its crystallinity through heterogeneous nucleation. As a result, the crystallization onset temperature, crystallization peak temperature and crystallization rate of PE-HD were improved. It was also found that the blend containing 10 wt % PE-UHMW achieved a minimum value in crystallization activation energy but a maximum value in crystallization rate.

Study on Properties of Antibacterial Polymeric Composites Based on PBS and Extracts from Cassia Occidentalis L

2018, 32 (01): 27-33; DOI: 10.19491/j.issn.1001-9278.2018.01.005

Abstract ( 590 )

In this paper, we prepared a type of antibacterial polymeric blends based on poly(butylene succinate) (PBS) and extracts from Cassia occidentalis L, and effect of the extract content on comprehensive properties of blends was extensively investigated. The results indicated that elastic modulus of the blends was improved significantly when 5 wt % and 7 wt % of the extracts were incorporated into PBS, and the blend containing 5 wt % of the extracts achieved a maximum water contact angle. There was no distinct influence observed on the thermal stability with a variation of extract content, and however, crystallization behaviors of the blends were improved in presence of the extracts. Biodegradation of the blends was investigated by using cutinase as a biocatalyst, and the results indicated that the blend containing 5 wt % of the extracts achieved a high degradation rate of 92.2 %. The blends also exhibited a significant antibacterial effect on Staphylococcus aureus, but there was no antibacterial effect found from them on Escherichia coli.

Structure and Tensile Properties of PE-HD/MWCNTs Composites Prepared by Submerged Friction Stir Processing Method

2018, 32 (01): 34-38; DOI: 10.19491/j.issn.1001-9278.2018.01.006

Abstract ( 536 )

In this paper, we reported the preparation of high-density polyethylene (PE-HD)/multi-walled carbon nanotubes (MWCNTs) composites through a submerged friction stir processing method, and effects of rotation speed and content of MWCNTs on morphologies and properties of the composites was investigated. The results indicated that MWCNTs were homogeneously dispersed in the matrix in the form of a “cloud”. For the case of the composites containing 1 wt % and 2 wt % of MWCNTs, the tensile strength increased at first and then tended to decrease with an increase of rotational speed. However, the composite containing 4 wt % of MWCNTs exhibited a continuous increase in tensile strength with an increase of rotational speed. A differential scanning calorimetric investigation indicated that the degree of crystallinity of PE-HD was reduced with an increase of the content of MWCNTs.

Effect of Calcium Pimelate Preparted by Different Methods on Crystallization and Melting Behaviors of Polypropylene

2018, 32 (01): 39-43; DOI: 10.19491/j.issn.1001-9278.2018.01.007

Abstract ( 723 )

Three types of calcium pimelate, D-CaPi, N-CaPi and S-CaPi, were prepared by a meta-decomposition reaction, a neutralization reaction and physical compounding of pimelic acid with calcium stearate, respectively, and the effect of different types of calcium pimelate on crystallization and melting behaviors of polypropylene (PP) were investigated. The chemical structure of calcium pimelate was confirmed by Fourier-transform infrared spectroscopy, and the crystallization and melting characteristics of PP/calcium pimelate compounds were determined by differential scanning calorimetry. The results indicated that these three types of calcium pimelate exhibited a nucleation capability for the crystallization of PP, which leads to an increase in crystallization temperature by 4.9 ℃ for PP/D-CaPi and PP/N-CaPi compounds and 6.5 ℃ for PP/S-CaPi compound. Moreover, S-CaPi was found much easier to induce β-form crystals for PP than D-CaPi and N-CaPi, and it could result in the formation of 84.5 % β-crystals for PP.

Study on Flame-retardant Synergy of Polycarbonate with RDP and Cucurbituril

2018, 32 (01): 44-50; DOI: 10.19491/j.issn.1001-9278.2018.01.008

Abstract ( 576 )

Flame-retardant polycarbonate (PC) compounds were prepared by combination of resiorcinol bis(diphenyl phosphate) (RDP) and cucurbituril (CB), and their flame-retardant performance was evaluated by limiting oxygen index, UL 94 vertical burning experiment and cone calorimetry. Moreover, their thermal behaviors were investigated by thermogravimetric analysis, and the morphology of their residual char was determined by SEM. The results indicated that the compounds obtained an optimum flame-retardant effect at the RDP/CB mass ratio of 6/2 and achieved an limited oxygen index of 32.5 vol %, a UL 94 V-0 classification and a heat release rate of 266 kW/m2. The combination of RDP and CB improved the thermal stability of PC and enhance its char formation effectively. The morphological observation confirmed that a dense and compact intumescent char layer was formed due to a synergy between RDP and CB, consequently enhancing the flame retardancy upon PC.

Effect of Shell Composition on Pyrolysis Kinetics Characteristics of Core-shell Structured Bamboo Plastic Composites

2018, 32 (01): 51-58; DOI: 10.19491/j.issn.1001-9278.2018.01.009

Abstract ( 458 )

This paper reported an investigation on pyrolysis characteristics of core-shell structured bamboo-plastic composites (BPC) prepared by a co-extrusion processing method. These BPC were constituted by a core layer of high-density polyethylene (PE-HD)/bamboo residue fiber composite and four types of shells including pristine PE-HD/bamboo pulp fiber composite, PE-HD/nano-CaCO3 compound and PE-HD/white mud composite. The pyrolysis characteristics of BPC were evaluated by thermogravimetric analysis at different heating rates, and their pyrolysis kinetics was analyzed by Coats-Redferm‘s and Flynn-Wall-Ozawa‘s models. The results indicated that the thermal stability of BPC was improved in the presence of PE-HD/nano-CaCO3 and PE-HD/white mud shells, however, the formation of PE-HD/bamboo pulp fiber shell exhibited few effects on their thermal stability. Moreover, the apparent activation energy of BPC presented a slight change with addition of 10 wt % bamboo pulp fiber, nano-CaCO3 and white mud into their shell.

Preparation and Properties of Silane-crosslinked Halogen-free Flame Retardant Polypropylene/Poly(ethylene-1-octene) Compounds

2018, 32 (01): 59-66; DOI: 10.19491/j.issn.1001-9278.2018.01.010

Abstract ( 572 )

Silane-crosslinked halogen-free flame-retardant polypropylene(PP)/poly(ethylene 1-octene(POE) composites were prepared by a two-step melt extrusion method using magnesium hydroxide(MH) and aluminum hydroxide（ATH）as flame retardants. The graft ratio of silane, mechanical properties, thermal performance and flame retardancy of the resulting compounds were extensively investigated. The results indicated that the compounds achieved a creep elongation lower than 25 % and an eternal deformation ratio lower than 4 % at the PP/POE/MH/ATH/silane weight ratio of 50/50/95~47.5/0~47.5/3. The limiting oxygen index of the compounds was improved slightly with increasing ATH content at a fixed content of the flame retardants. The compounds containing MH exhibited a higher thermal stability than those containing MH and ATH. The decreasing smoke release rate was also found to show a variation trend in an order of PP/POE/ATH compounds>PP/POE/MH/ATH compounds>PP/POE/MH compounds.

Preparation and Performance of Poly(vinyl alcohol)/Sulfated Chitosan Hybrid Membrane for Alkali Recovery

2018, 32 (01): 67-72; DOI: 10.19491/j.issn.1001-9278.2018.01.011

Abstract ( 536 )

In this paper, hybrid membranes containing SiO2 particles were prepared by a crosslinking reaction of poly(vinyl alcohol) with sulfonated chitosan in the sol-gel process, and the effect of sulfonated chitosan content on the structure and performance of hybrid membranes was investigated by Fourier-transform infrared spectroscopy, scanning electron microscopy, dynamic mechanical analysis, ion-exchange capacity, water uptake and linear expansion. The results indicated that the hybrid membranes presented water-uptake amounts of 10 wt %~15 wt %, linear expansion rates of 10 %~15 % and ion-exchange capacities of 0.10~0.65 mmol/g. The hybrid membranes prepared exhibited an excellent OH- ion transport property and acceptable selectivity, and their dialysis coefficient and separation factor of alkali recovery were in the range of 0.0135~0.0160 m/h and 15.6~26.9, respectively.

Preparation and Characterization of Poly(styrene-co-butyl acrylate)/Fe₃O₄ Composites

2018, 32 (01): 73-76; DOI: 10.19491/j.issn.1001-9278.2018.01.012

Abstract ( 445 )

Poly(styrene-co-butyl acrylate) (PSb)/Fe3O4 nanocomposites were prepared via in-situ polymerization. Microstructure and properties of the nanocomposite were characterized by Fourier-transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction and physical performance measurements. The results indicated that Fe3O4 nanoparticles had a diameter around 9 nm, and they were uniformly dispersed in the PSb matrix without any aggregation. These nanocomposites were found to exhibit a super paramagnetism feature. The incorporation of Fe3O4 nanoparticles into PSb could enhance the thermal stability of the nanocomposites.

Study on Pressure Variation of PE-HD Pipes for Nuclear Power Plants in Hydrostatic Test

2018, 32 (01): 77-83; DOI: 10.19491/j.issn.1001-9278.2018.01.013

Abstract ( 596 )

The stress relaxation normally occurs during the hydrostatic test of PE-HD due to the viscoelasticity, which leads to a change in internal pressure. This work focused on a study on the law of pressure variation during the hydrostatic test of PE-HD on the basis of the relaxation modulus equation of PE-HD, the long-term mechanical model of pipes and the state equation of water. The effects of the constraint types of clamp and the pressure holding time and temperature on pressure variation were also investigated. The results indicated that there was no effect from the constraint types on the pressure, but the increase of pressure holding time could effectively suppress the pressure decrease and decline rate. As a result, the test stability was improved. The pressure in the hydrostatic test of PE-HD was reduced with an increase in temperature, and there was a linear relationship observed between the temperature and the decline rate of pressure.

Effect of Viscoelastic Characteristics on Thermal-fluid-structure Coupling Deformation in In-mold Micro Assembly Molding Process

2018, 32 (01): 84-89; DOI: 10.19491/j.issn.1001-9278.2018.01.014

Abstract ( 533 )

In order to solve the key scientific problems in control difficulty of thermal-fluid-structure coupling deformation in mold micro assembly process, a theoretical model was established to describe mechanisms of thermal-fluid-structure coupling deformation in polymer in-mold micro assembly molding process on the basis of the influence of environmental impact on secondary molding viscoelastic melt filling flow. A finite element numerical simulation was also conducted to investigate the effect of secondary molding melt viscosity on the thermal-fluid-structure coupling deformation during the mold micro assembly process. The results indicated that the driving force of the micro shaft deformation induced by the thermal-fluid-structure coupling effect was derived from the thermal-fluid-structure coupling pressure and viscous friction drag shear stress on the micro assembly surface. However, the elastic normal stress of secondary molding viscoelastic melt filling flow showed a restraining effect on the coupling deformation. The thermal-fluid-structure coupling load and micro shaft coupling deformation increased with increasing secondary molding melt viscosity, which reduced the viscosity of secondary molding melt. This is beneficial to the improvement in processing accuracy of the micro assembly.

A Simplified Heat Transfer Model for Heating Phase in Rotational Molding Process

2018, 32 (01): 90-96; DOI: 10.19491/j.issn.1001-9278.2018.01.015

Abstract ( 572 )

A simplified heat transfer model for heating phase in rotational molding process was established upon the heating stage from the initial heating of mold to the initial melting of powders. The heat transfer coefficient between the inner mold wall and internal mixture was obtained from the unsteady heat conduction equation when the inner mold wall contacted the internal mixture. The differential equations for the model were solved with the aid of MATLAB software. This model was validated by comparing the experimental results with the calculated temperature of internal air. The effects of heating temperature inside the chamber, outer heat transfer coefficient and the thickness of plastic part on heating time and heating efficiency were investigated by use of this model. The results indicated that the heating efficiency increased with an extension of time, and it was higher for thicker plastic parts.

Effect of Mixing Characteristics of Drum-type Rotors on Residual Fiber Length in Silicone Rubber/Carbon Fiber Composites

2018, 32 (01): 97-101; DOI: 10.19491/j.issn.1001-9278.2018.01.016

Abstract ( 460 )

In this paper, a new drum-type rotor was designed on the basis of characteristics of carbon-fiber-reinforced silicone rubber composites, and its mixing behavior and effect on the residual fiber length in the silicone rubber/carbon fiber composites were analyzed by a numerical simulation software and then verified by experimental results. The results indicated that the rotor configuration, rotor speed and mixing time were major factors determining the residual fiber length, and the DR-I type rotor was found to damage the fiber more seriously. The fiber damage became more serious with increasing rotational speed and mixing time, thus leading to a decrease in residual fiber length.

Analysis of Effect of Injection-molding Process Parameters on Warpage Deformation of Printer Plastic Parts Based on CAE

2018, 32 (01): 102-107; DOI: 10.19491/j.issn.1001-9278.2018.01.017

Abstract ( 529 )

The orthogonal experiment was conducted for a printer plastic part with metal inserts under different injection-molding conditions by using a CAE numerical simulation. The results indicated that the mold temperature, holding pressure and holding exhibited a minor effect on x-, y- and z- directional warp distortion, and the holding pressure, mold temperature and mold temperature also showed the significantly factors on x-, y- and z-directional warp distortions. x-, y- and z-directional warp distortions could be reduced by manufacturers through optimizing and adjusting the process parameters.

Preparation of Hollow-structure Zinc Stannate Using Carbon Spheres as Template and Its Application in Flame-retardant PVC

2018, 32 (01): 108-113; DOI: 10.19491/j.issn.1001-9278.2018.01.018

Abstract ( 540 )

The hollow-structured zinc stannate (Zn2SnO4) was prepared by using tin tetrachloride and zinc nitrate as raw materials and carbon spheres as a template via a hydrothermal-calcination method. This method was expected to be applied for the disposal and reuse of heavy metal ions in waste water. The chemical structure of Zn2SnO4 and its flame-retarding effect on PVC were characterized by limiting oxygen index, transmission electron microscopy, cone calorimetry, scanning electron microscopy and X-ray diffraction measurements. The results indicated that the limiting oxygen index of the flame-retardant PVC achieved a limiting oxygen index of 31.4 vol % when 10 g of Zn2SnO4 were added, which increased by 6.5 % compared with the blank PVC. However, the flame-retardant PVC exhibited the similar elongation at break of 241 % to the blank one. The results obtained from cone calorimetry indicated that the introduction of Zn2SnO4 effectively reduced the total heat release by 30.6 % and the total smoke release by 54.3 % during the combustion process of the flame-retardant PVC.

Lubrication Characteristics and Mechanism of Polyethylene Waw and Calcium Stearate for Poly(vinyl chloride)

2018, 32 (01): 114-119; DOI: 10.19491/j.issn.1001-9278.2018.01.019

Abstract ( 830 )

Lubrication characteristics of polyethylene wax and calcium stearate (CaSt2) for poly(vinyl chloride) (PVC) were investigated by measuring plasticizing time with a torque rheometer. The results indicated that polyethylene wax acted an effective primary resin external lubricant for PVC, and CaSt2 acted as an effective secondary resin external lubricant. There was a significant synergistic effect when these two lubricants were combined. The external lubricating performance of polyethylene wax and its combination with CaSt2 was enhanced with an increase of total amount of two lubricants, in which the fraction of polyethylene wax was fixed as 1 phr. The lubrication mechanisms can be deduced as follows: when the lubricant is used alone, polyethylene wax can spread over and wet the PVC particles to prevent them from contacting directly and friction with each other, but CaSt2 cannot wet PVC particles due to the formation of agglomerations and reverse micelles. On the other hand, the combination of these two lubricants can make CaSt2 dissolved slightly in polyethylene wax and then absorbed on the interface between PVC particles and polyethylene wax. As a result, the direct contact and friction between the PVC particles can be prevented effectively.

Parametrical Design of Counter-rotating Twin-screws Based on SolidWorks API

2018, 32 (01): 120-124; DOI: 10.19491/j.issn.1001-9278.2018.01.020

Abstract ( 871 )

In this paper, an investigation was performed on the formation and correction method of the cross section curves of counter-rotating twin screws with two tips. The parametrical design and 3D modeling of counter-rotating twin screws were conducted by using SolidWorks API on the basis of this investigation. This program provided a useful tool for further finite element analysis and computer-aided simulation. This method makes 3D modeling easier for counter-rotating twin screws and thus enhances the operation efficiency.

Analysis and Modification of Warpage Deformation in Guide Rails of Vehicle Storage Boxes

2018, 32 (01): 125-130; DOI: 10.19491/j.issn.1001-9278.2018.01.021

Abstract ( 544 )

Warpage deformation easily occurs in guide rails of vehicle storage boxes during the injection molding process. This paper reported an analysis and a modification method for the local warpage of the guide rail on the basis of its injection-molding characteristics. Using a Moldflow software for numerical simulation, the orthogonal design method was adopted to deduce the optimal process parameters for the injection molding of the guide rails by using polyoxymethylene as a raw material. In this orthogonal design, mould temperature, injection time, packing pressure and cooling time were taken as experimental factors, and the warpage deformation was taken as an experimental target. The guide rail was injection-molded with these optimized process parameters, and its warpage was controlled with 0.5 mm in the x and z directions. This result well met the requirement of production.

Design of Injection Molds for a Two-color Cup with Handles Based on Conformal Cooling Technology

2018, 32 (01): 131-136; DOI: 10.19491/j.issn.1001-9278.2018.01.022

Abstract ( 571 )

A two-color injection mold with a half-slider structure is designed for a two-color cup with a handle. The mold is mounted in an injection molding machine with a turntable plate. Hot runner technology is adopted in the mold to remove the condensed material and realize the production automation. The cooling system is built with conventional cooling channels in the cavities and a conformal cooling channel in the core. The simulation results shown that the cooling configuration can effectively improve the cooling effect and improve the cooling efficiency. The insert and core with a conformal cooling channel can be obtained with a foundation support machined and the top part forming via a 3D printing technology of metal powder selective laser sintering. The parting of the sliders is driven by compression springs and T buckles. The two-color injection mold is reasonable in structure and reliable in operation.