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2018, Volume 32 Issue 07 Publication date: 26 July 2018 Previous Issue Next Issue

Research Progress in Chlorine-oxidation Resistance of Plastic Pipes

2018, 32 (07): 1-9; DOI: 10.19491/j.issn.1001-9278.2018.07.001

Abstract ( 681 )

This paper reviewed the research progress in chlorineoxidation resistance of plastic pipes and also introduced the advantages and disadvantages of different chlorine disinfection methods for drinking water. Moreover, the several evaluation methods of chlorineoxidation resistant performance of plastic pipes were introduced in detail and their oxidation mechanisms were discussed.

Research Progress of Polymer/Biomass Composites

2018, 32 (07): 10-20; DOI: 10.19491/j.issn.1001-9278.2018.07.002

Abstract ( 604 )

The articles reviewed the research progress in polymer/biomass composites with several biomass materials like rice husk, wheat straw, bamboo and peanut shell, and also briefly introduced the main components and interface modification of these composites. Moreover, the application prospects of polymer/biomass composites were discussed.

Application Progress of Polyethylene-based Special-purpose Materials for Gas Pipe

2018, 32 (07): 21-27; DOI: 10.19491/j.issn.1001-9278.2018.07.003

Abstract ( 455 )

This article reviewed the application progress of plastic pipe in the field of gas transport and distribution. The development history of key technologies for preparation of polyolefin was introduced briefly, and the difference of performance requirements for polyethylene (PE) compounds was analyzed by comparing GB 15558.1—2015 with GB 15558.1—2003. Moreover, the difference of performance requirements between the international standard ISO 4437 and European standard EN 1555 was also analyzed. The highperformance characteristics and development processes of PE80, PE100, PE100RC grad PE materials were particularly discussed, and the suggestion for the development of PE125 grad PE material was proposed.

Preparation and Application of Microencapsulated Ammonium Polyphosphate with Phenyl Polysiloxane Shell for Flame Retardancy of Polypropylene

2018, 32 (07): 28-32; DOI: 10.19491/j.issn.1001-9278.2018.07.004

Abstract ( 545 )

Phenyl polysiloxane microencapsulated ammonium polyphosphate (MAPP) was prepared by a sol-gel method using phenyltrimethoxy silane as a precursor. MAPP was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and thermogravimetric analyzer (TGA). The results showed that ammonium polyphosphate (APP) was successfully encapsulated with phenyl polysiloxane. The thermal stability and hydrophobicity of MAPP were significantly better than that of APP. MAPP and pentaerythritol (PER) were used together to improve the flame retardancy of polypropylene (PP). The results of limiting oxygen index (LOI) test demonstrated that the flame retardant property of PP/MAPP/PER composites were better than that of PP/APP/PER composites at the same loading. And the PP/MAPP/PER composites reached the UL-94 V-0 level. Moreover, the addition of flame retardant and carbon forming agent could promote the crystallization behavior of PP.

Effect of Emulsifying Conditions on Emulsion Properties of Self-emulsifying Polyethylene Wax

2018, 32 (07): 33-39; DOI: 10.19491/j.issn.1001-9278.2018.07.005

Abstract ( 733 )

The selfemulsifying polyethylene wax was prepared by saponifing polyethylene wax grafted with maleic anhydride (PEW-g-MAH), and the effects of solid content and emulsifying conditions on the selfemulsifying capability of selfemulsifying polyethylene wax and the appearance, dispersion, stability and particle size of the resulting polyethylene wax emulsion were investigated. The results indicated that the solid content of polyethylene wax emulsion is the main influence factor for the emulsifying capability of selfemulsifying polyethylene wax. Only when the solid content is higher than 30 %, the polyethylene wax emulsion could achieve a excellent dispersion, longterm stability and uniform particle size. The emulsion conditions like temperature, time and stirring rate also presented some influences, and however the effect of emulsion temperature on the emulsion properties of selfemulsifying polyethylene wax was more significant. The overhigh or overlow emulsion temperature was disadvantageous to the dispersion and stability of polyethylene wax emulsion. The optimum emulsion temperature for the selfemulsifying polyethylene wax was determined as 130 ℃ when prepared by saponifing PEWgMAH.

Preparation and Properties of Epoxy/Zinc Acrylate Latent Curing Systems

2018, 32 (07): 40-46; DOI: 10.19491/j.issn.1001-9278.2018.07.006

Abstract ( 546 )

A epoxybased latent curing systems were prepared by using bisphenolA type epoxy resin as a raw material and zinc acrylate (ZDA) as a latent curing agent. The molecular structure of this curing system was characterized by Fouriertransform infrared spectroscopy, and the effect of ZDA content on its curing behavior and properties were investigated by differential scanning calorimetry in the nonisothermal process. Furthermore, the apparent activation energy of curing reaction was calculated by Kissinger's and Ozawa's method. The activation energy of curing reaction was found to decrease with an increase of ZDA content, indicating an easier reaction for this curing system. Thermogravimetric analysis results indicated that the thermal stability of the epoxy thermosets decreased with increasing the ZDA content. The thermoset containing 15 phr of ZDA achieved a maximum value in flexural strength, flexural modulus and tensile strength, which were 89.25 MPa, 2.68 GPa and 48.21 MPa, respectively. Scanning electron microscopic observation demonstrated that there was a brittleductile transition occurring with the gradual increase of curing agent, thus enhancing the impact toughness of the thermosetting materials.

Effect of Bamboo Fiber Due to Alkali Treatment on the Structure and Properties of EVA

2018, 32 (07): 47-51; DOI: 10.19491/j.issn.1001-9278.2018.07.007

Abstract ( 642 )

Bamboo fibers were treated with NaOH solution and the ethylene-vinyl acetate copolymer/ bamboo fiber (EVA/BF) composites were prepared by a twin screw extruder and injection molding, and analyzed by IR, SEM, DSC, XRD, TG, MFI and mechanical testing. The results demonstrated that BF had heterogeneous nucleation effect on crystallization of EVA. The compressive modulus and strength of EVA increased significantly with the addition of BF, and the tensile strength of EVA/30-40% BF were close to or higher than that of pure EVA. Relatively higher thermal stability of EVA/BF composites during the melt processing results from the removal of the cementing materials of BF during alkali treatment, better interfacial adhesion betweed EVA and BF, and lower melt processing temperature of EVA.

Preparation,Microstructure and Performance of PLA/PBAT/OMMT Nanocomposites

2018, 32 (07): 52-57; DOI: 10.19491/j.issn.1001-9278.2018.07.008

Abstract ( 360 )

The poly(lactic acid) (PLA)/poly(butylene adipatecoterephthalate) (PBAT)/organic montmorillonite (OMMT) nanocomposites were prepared by melt blending on a torque rheometer, and their crystallization and melting behaviors, morphology, microstructure and rheological properties were investigated by differential scanning calorimetry, polarized optical microscopy, scanning electron microscopy, rotational rheometer and Fouriertransform infrared spectroscopy. The results indicated that the presence of PBAT and OMMT improved the crystallization rate and density of crystal nucleus of PLA. The addition of chain extender could enhance the compatibility of PLA with PBAT, thus leading to an increase in storage modulus and an enhancement in melt elasticity.

Preparation and Characterization of Low-density Polyethylene/Functionalized Graphene Nanocomposite Films

2018, 32 (07): 58-65; DOI: 10.19491/j.issn.1001-9278.2018.07.009

Abstract ( 667 )

Graphene oxide was modified with γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH-560) via a surface grafting method, followed by a reduction reaction with hydrazine hydrate to form functionalized graphene. The lowdensity polyethylene (PE-LD)based nanocomposite films were prepared by melt blending with functionalized graphene as well as the pristine one, followed by hollow blow molding, and their structures, morphologies, optical performance, and thermal and mechanical properties were characterized. The results indicated that the silane coupling agent, KH-560, was successfully grafted onto graphene. Compared to pristine graphene, the functionalized graphene exhibited an increase in disorder, and its interlayer space increased by approximately 80 %, which resulted in a better distribution in PE-LD matrix and a decrease in aggregation. Moreover, the thermal stability and mechanical properties of nanocomposite films were improved by functionalized graphene more significantly in comparison with pristine graphene. However, pristine graphene could enhance the optical and barrier properties more effectively. Compared to pure PE-LD films, the nanocomposite film containing 0.5 wt % of functionalized graphene presented an increase in crystallinity degree by 8.4 % and in Young's modulus by 63.9 %.

Preparation and Properties of Porous Functional PLA/Nano-cerium Oxide Composite Fiber

2018, 32 (07): 66-71; DOI: 10.19491/j.issn.1001-9278.2018.07.010

Abstract ( 526 )

The PLA-based nanocomposite fibers with different contents of CeO2 were prepared by an electrospinning method, and the effect of CeO2 content on the properties of electrostatic spinning liquid, voltage, fiber diameter and the propagation of membrane cells were investigated systematically. The results indicated that the surface tension of electrospinning solution decreased gradually with an increase of CeO2 content, but the conductivity increased gradually. Scanning electron microscopic observation demonstrated that the diameter of electrospun PLA fiber increased with an increase of the voltage at first and then tended to decrease, and the higher the voltage, the wider was the distribution of fiber diameter. The addition of CeO2 could effectively reduce the diameter of PLA fibers, and however the overloading of CeO2 resulted lead to an increase in fiber diameter as well as a wider distribution in diameter. DSC results indicated that the incorporation of CeO2 promoted the crystallinity of PLA significantly, thus resulting in a transformation of crystallization behavior from multiple melting peaks into the single one. Moreover, the PLA/CeO2 nanocomposite membranes exhibited good biocompatibility, and the increase of CeO2 content enhanced the propagation of membrane cells more significantly.

Study on Non-isothermal Crystallization Kinetics of Polypropylene Matrix Composites with Maleic Anhydride-grafted Polypropylene and Waste Printed Circuit Boards Nonmetallic Powders

2018, 32 (07): 72-77; DOI: 10.19491/j.issn.1001-9278.2018.07.011

Abstract ( 481 )

The nonisothermal crystallization behaviors and kinetics of polypropylene (PP) matrix composites with maleic anhydridegrafted PP (PP-g-MAH) and waste printed circuit boards (PCB) nonmetallic powders was studied with the Avrami equation using differential scanning calorimetry. The modified Avrami theories from Jeziorny's and Mo Zhi-shen's equations were adopted to analyze the DSC data. The results indicated that waste PCB powders exhibited a heterogeneous nucleation effect on the crystallization of PP. With increasing the crystallization temperature of PP, the nucleation rate became faster, the grain size distribution became narrower, and the crystallization rate was also improved. However, due to increasing of viscosity of composites, the waste PCB powders also prevented the PP matrix from crystallization at a high loading due to the increase of viscosity of composites.

Thermal Degradation Kinetics of PMMA/MWCNT Composites

2018, 32 (07): 78-82; DOI: 10.19491/j.issn.1001-9278.2018.07.012

Abstract ( 734 )

The composites based on poly(methyl methacrylate) (PMMA) and multiwalled carbon nanotubes (MWCNT) were prepared by a solutionblending method, and their thermal degradation processes under different atmosphere were investigated by a thermogravimetric method. The kinetic parameters of thermal degradation were obtained by the Flynn-Wall-Ozawa’s, Kissinger’s and Friedman’s methods. The results indicated that the initial degradation temperature of composite containing 3 wt % increased by 54.62 ℃ in nitrogen and 70.4 ℃ in oxygen in comparison with pure PMMA, and its maximum heat loss rate was also improved to some extent. It was concluded that the introduction of MWCNT could effectively improve the lowtemperature thermal stability of PMMA, especially in an aerobic environment. However, the improvement in hightemperature thermal stability was not so significant. The values of activation energy (Ea) calculated by Kissinger's, flyn-wall-ozawa's and Friedman's methods were in good agreement with each other. The composites achieved a maximum improvement in Ea when 3 wt % of MWCNT was added into PMMA. In addition, the order of reaction (n) deduced by the Friedmans method for the composites was approximately 1.5 in nitrogen and 0.9 in oxygen.

Effect of Mixing Equipment Structure on Residual Length of GF and Mechanical Properties of PP/GF Composites

2018, 32 (07): 83-89; DOI: 10.19491/j.issn.1001-9278.2018.07.013

Abstract ( 395 )

The polypropylene (PP) matrix composites reinforced with 20 wt % glass fiber (GF) were prepared by a melt blending method using a twinrotor continuous mixing extruder and an intermeshing corotating twinscrew extruder, and the residual GF length and mechanical properties of composites were investigated to determine the effect of mixing equipment structure with different mixing characteristics. The results indicated that the mechanical properties of PP/GF composites were improved significantly with an increase of residual GF length in the composites. The twinrotor continuous mixing extruder exhibited a better effect on preserving a longer fiber length than intermeshing corotating twinscrew extruder. A proper decrease in rotor speed and dispersibility of twinrotor continuous mixing extruder could preserve a longer residual length of glass fiber in the composites, thus enhancing the mechanical properties more effectively.

Experimental Study on Dynamic and Quasi-static Split Tension of Rigid Polyurethane Foam

2018, 32 (07): 90-99; DOI: 10.19491/j.issn.1001-9278.2018.07.014

Abstract ( 340 )

The quasistatic split tests of rigid polyurethane foams (RPUF) with densities of 0.54 and 0.62 g/cm3 were carried out on a universal test machine equipped with a strain analysis measuring system. Meanwhile, the dynamic split tests of RPUF with a density of 0.62 g/cm3 were performed by the method of splitHopkinson pressure bar. The influence factors of strain rate, density and aspect ratio are mainly considered in the experimental study. The results indicated that the tensile strength and elastic modulus of RPUF increased with an increase of strain rate in the quasistatic splitting tests, but decreased with an increase of aspect ratio. Moreover, the tensile strength was relative with the density. The greater the material density, the higher was the tensile strength. For the RPUF with a higher density, the variation of tensile strength was no longer significant material when the strain rate reached a certain value. In dynamic splitting tests, the DIF value of RPUF was improved remarkably with an increase of strain rate, and it also tended to increase nonlinearly. However, the tensile strength and elastic modulus decreased with an increase of aspect ratio.

Bonding Behavior Between GFRP Bars and Concrete Under Cyclic Loading Condition

2018, 32 (07): 100-104; DOI: 10.19491/j.issn.1001-9278.2018.07.015

Abstract ( 376 )

A series of drawing tests were carried out for the standard bonding specimens of GFRP bars with a diameter of 16 mm when embedded in depths of 4d, 5d and 8d under the monotonic loading and cyclic loading conditions, and the variations of the bondingslipping relation, the relationship between embedded depth and bonding strength, and the evolution law of bonding stiffness and slip of loading end with the cycle number. As a result, the evolution law of hysteresis curve under cyclic loading was obtained. The results indicated that fewer cycle times almost had no effect on bonding strength and the amount of slip. The bonding strength did not degenerate significantly but tended to increase to some extent when the test specimen was subjected to cyclic loading with a low stress level and less cycle time. The degradation of bonding strength between GFRP bars and concrete was significant when the test specimen was subjected to cyclic loading under a high stress level. This research result can provide an evidence for further study on fatigue properties of the concrete structures reinforced with GFRP bars.

Lifespan Prediction of Polyethylene Pipe Based on BP Neural Network Algorithm

2018, 32 (07): 105-108; DOI: 10.19491/j.issn.1001-9278.2018.07.016

Abstract ( 440 )

The influence factors for the lifespan of polyethylene (PE) pipe in practical application were analyzed, and the controllable factors were selected to conduct a lifespan prediction. A lifespan prediction model was established according to the experimental results, and the changeable variables of model were designed by reference to the experimental variables using MATLAB software. For the experimental design, a certain numerical gradient was selected according to the hydrostatic tests. The experimental design was according to the hydrostatic tests. Select the experimental temperatures, the effective chlorine contents in the experimental water, and the experimental pressures for totally 192 groups of experiments and 384 test samples. The PE pipe was simulated in the practical use of water distribution systems. In the computational modeling process, the BP neural network fatigue equation model with threefactor variables was selected for life prediction. The obtained results indicated that the BP neural network has a scientific significance to calculate the service lifespan of PE pipe, and the goodness of fit, R2, was up to 0.87 in probability according to this network model. Compared to the conventional algorithms of PE pipe, the prediction results have superiority in calculation simplification, specimen expansion, model threshold and importance variability.

Three-dimensional Numerical Simulation of Unbalanced Shear-flow Phenomenon on Geometric Equilibrium Runner

2018, 32 (07): 109-115; DOI: 10.19491/j.issn.1001-9278.2018.07.017

Abstract ( 517 )

Considering an inertial effect, a dynamic simulation for internal and external unbalanced shear flow phenomena on the geometrical equilibrium runner was performed by using the layered refining runner mesh technique, and the influence of technological factors on internal and external flow imbalance was investigated by an orthogonal experiment. The results indicated that flow rate presented a significant effect on the internal and external flow imbalance, and the internal and external imbalance index decreased with an increase of flow rate. The influence of melt temperature and injection pressure on the internal and external imbalance index was completely different, presenting an opposite trend.

Heat-stabilizing Effect of Dicarboxylic Acid Monoester Metal Salts on PVC Law and Mechanism of Performance Evolution

2018, 32 (07): 116-121; DOI: 10.19491/j.issn.1001-9278.2018.07.018

Abstract ( 495 )

The effects of calcium, strontium, barium, zinc and cadmium salts of monobutyl malonate, succinate and maleate on the heat stability of poly(vinyl chloride) (PVC) were determined by an oven discoloration method. The results indicated that the discoloration rate of PVC stabilized with dicarboxylic acid monoester metal salts decreased with an increase of the positive electricity of carbon atom in carbonyl groups and the polarization force of metal ions in the molecules. However, PVC stabilized with dicarboxylic acid monoester metal salt containing a dienophilic structure presented a weaker coloring effect. It was deduced that the reduction mechanism of discoloration rate for PVC by dicarboxylic acid monoester metal salts was attributed to the electrophilic reactions of carbon atom in carbonyl groups and metal ions with PVC. Moreover, the DielsAlder cycloaddition reaction led to the weak coloring effect on PVC when stabilized with dicarboxylic acid monoester metal salt containing a dienophilic structure.

Investigation on Preparation and Properties of Synergistic Flame Retardant TPU with Triazine Intumescent Flame Retardant/Magnesium Silicate

2018, 32 (07): 122-125; DOI: 10.19491/j.issn.1001-9278.2018.07.019

Abstract ( 586 )

The flameretardant polyurethane (TPU) compounds were prepared by using triazine charringfoaming agent (CFA) and ammonium polyphosphate (APP) as intumescent flame retardants (IFR) and magnesium silicate (MgSiO3) as a synergistic flame retardant. The flame retardant performance, mechanical properties, thermal decomposition behaviors and morphologies of the char layers were investigated. The results indicated that the limiting oxygen index of pure TPU was only 22.0 vol %, leading to flammability in the air. The flameretardant TPU compounds achieved an limiting oxygen index of 37.1 vol % with the addition of 28 wt % IFR and 5 wt % MgSiO3, and they also reached a V-0 rating according to the UL 94 classification. However, their tensile strength and elongation at break decreased significantly due to the incorporation of these flame retardants. TGA results indicated that the thermal decomposition temperature and maximum thermal degradation rate of flameretardant TPU compounds were reduced with the addition of flame retardants, but the residual char content was improved significantly.

Structure and Properties of Poly(lactic acid)/Acetyl Tributyl Citrate Blend Films Modified with Poly(ethylene glycol)

2018, 32 (07): 126-131; DOI: 10.19491/j.issn.1001-9278.2018.07.020

Abstract ( 598 )

Poly(lactic acid) (PLA)/acetyl tributyl citrate (ATBC)/poly(ethylene glycol) (PEG) blend films were prepared by solution blending, and their structure and properties were characterized by Fouriertransform infrared spectroscopy, thermal analysis, X-ray powder diffraction, scanning electron microscopy (SEM) and tensile experiments. The results indicated that the tensile strength increased from 29.52 MPa to 33.40 MPa and the elongation at break increased from 262 % to 292 % after the PLA/ATBC blend films were modified with a proper amount of PEG. As a result, the flexibility of the films was enhanced. The terminal hydroxyl groups in PEG could interact with the carbonyl of PLA to form hydrogen bonds, which improved the thermal stability and crystallinity of blend films. SEM micrographs demonstrated that there was no crack on the surfaces of the PLA/ATBC/PEG blend films after aging for 90 days, suggesting that the service lifespan of films was extended. Moreover, the compatibility and processability of blend films were improved with the addition of small amounts of N,N′-ethylenebis(stearamide).

Design and Process Optimization of Stack Injection Mould for Balance Ring of Washing Machine Based on Moldflow Software

2018, 32 (07): 132-136; DOI: 10.19491/j.issn.1001-9278.2018.07.021

Abstract ( 530 )

A stack injection mold was designed according to characteristics of the balance ring of washing machine. The Moldflow software was used to simulate the filling, packing and warpage deformation processes of injectionmolded parts. Through the simulation of mold filling process, the number of gate and the size of runner were optimized, and the flow balance was achieved. The optimal control method and parameters of packing process were obtained by comparison of the results from the packing and warpage deformation processes with different packing parameters. The results indicated that the molding and assembling requirements for balance ring could be well met by the stack mold designed in this work.

CAE Optimization Design of Injection Molding of Automobile AB Column Interior Trim Panel Based on LM-BP Neural Network

2018, 32 (07): 137-145; DOI: 10.19491/j.issn.1001-9278.2018.07.022

Abstract ( 445 )

Taking the injection molding of an automotive interior A and B column trim panel as an example, the injection molding process was optimized, which included the optimization of different gating systems, molding quality and molding process parameters for three processes. For the optimization of molding technology, the traditional BP neural network was modified on the basis of the LM algorithm. The improved LMBP neural network was used to optimize the process pathway through an orthogonal test, and a better prediction for thinning and optimizing process path was achieved. The optimized injection molding process parameters are obtained through auxiliary selection with the LMBP neural network. These process parameters could be used for the practical injection molding to obtain ideal injectionmolded parts. This work provides a good guidance for the injection molding of automotive plastic parts.