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2018, Volume 32 Issue 08 Publication date: 26 August 2018 Previous Issue Next Issue

Research Progress in Photodegradation of Polyolefins

2018, 32 (08): 1-6; DOI: 10.19491/j.issn.1001-9278.2018.08.001

Abstract ( 675 )

This paper reviewed the recent progress in the photodegradation mechanism and influence factors, photodegradation additives and photodegradation controllability of polyolefins and also discussed the development trend in the photodegradation of polyolefins. The photodegradable performance of polyolefins was found to be associated with the chemical composition, functional groups, additives and environmental conditions like stress. To achieve a controllable degradation for polyolefins, it is vital to select suitable photodegradants and relevant stabilizers as well as their coordination in the resin. In this field, the main attention will be focused on the development of special photodegradants and relevant compounding products and the improvement of photodegradation rate. Moreover, it is also of importance for the development of photodegradation-controllable polyolefins in an ecologically friendly way with a reduced cost.

Research Progress in DOPO-Based Flame Retardants for Polymers

2018, 32 (08): 7-13; DOI: 10.19491/j.issn.1001-9278.2018.08.002

Abstract ( 1363 )

This article reviewed the research progresses in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-type flame retardants and their applications in polymeric materials like epoxy resins, polyesters and polypropylene and also pointed out their future development direction. At the present, the development of DOPO-based flame retardants used for polymer are mainly focused on the direction toward low addition, multi-elemental flame-retardant synergy and no side-effect on the flame-retarded polymers. This type of flame retardants exhibit exhibits a good application prospect.

Research Progress in Radio-resistant Modification of Poly(vinyl chloride) for Medical Use

2018, 32 (08): 14-18; DOI: 10.19491/j.issn.1001-9278.2018.08.003

Abstract ( 1219 )

This paper reviewed the radio-resistant modification mechanisms for poly(vinyl chloride) (PVC) by using thermal stabilizers, antioxidants and light stabilizers, and the synergetic effects from these additives were also discussed. Moreover, the research progress in the radio-resistant modification of PVC was summarized, and the future development of radio-resistant PVC materials was also prospected.

Influence of EMAA-Na Ionomer on Morphology and Rheological Behavior of PE-HD/Al₂O₃ Composites

2018, 32 (08): 19-24; DOI: 10.19491/j.issn.1001-9278.2018.08.004

Abstract ( 553 )

High-density polyethylene (PE-HD)/aluminum oxide (Al2O3) composites were prepared by melt blending with sodium ionomer (EMAA-Na) as a compatibilizer. The cross-section structure of the composites was observed by scanning electron microscopy, and steady and dynamic rheological properties were investigated by a plate rheometer and capillary rheometer. The results indicated that the interfacial adhesion between PE-HD and Al2O3 was improved with the addition of EMAA-Na, leading to disappearance of the gap between the matrix and fillers. The steady-shear viscosity and elongational viscosity were improved with increasing the content of EMAA-Na, and PE-HD/Al2O3/EMAA-Na composites showed a shear-thinning and strain-hardening behavior. Dynamic rheology measurement indicated that the incorporation of EMAA-Na improved the interaction between different components, thus enhancing the elasticity of composite.

Effect of Nano-SiO₂ Wrapping on Microcrystalline Cellulose on the Properties of PLA /PBS Composites

2018, 32 (08): 25-32; DOI: 10.19491/j.issn.1001-9278.2018.08.005

Abstract ( 609 )

A type of bio-degradable thermoplastic composites was prepared by melt blending PLA and PBS with the nano-SiO2 particles encapsulated with microcrystalline cellulose (MCC). The effect of nanoSiO2 on the mechanical property, thermal stability and crystallinity of the composites was investigated by SEM, TGA, DSC and DMA. The experimental results indicated that the encapsulation of nano-SiO2 with MCC enhanced the dispersion of nano-SiO2 particles in the matrix due to an improvement in interfacial compatibility between the matrix resins and fillers by MCC. Compared to the PLA/PBS/MCC compounds containing 5 % MCC, the PLA/PBS/nano-SiO2-MCC composite with 5 % MCC exhibited an increase in storage modulus, impact strength and crystallinity degree by 13.04 %, 11.70 % and 71.92 %, respectively.

Study on Preparation and Properties of High-flowing, High-modulus and High-impact Polypropylene Composites

2018, 32 (08): 33-39; DOI: 10.19491/j.issn.1001-9278.2018.08.006

Abstract ( 617 )

The effects of POE, talc, EBS on the mechanical properties, melt flow index, crystallization temperature, thermal stability and fracture morphology of PP matrix composites were investigated. The incorporation of 25 phr POE into this PP resulted in a completely brittle-ductile transition. The composites achieved a melt flow index of 22.9 g/10 min, flexural modulus of 1887.7 MPa and notched impact strength of 31.2kJ/m2 at a PP/POE/talc weight ratio of 80∶20∶40. Compared to pure PP, the composites gained an increase in flexural modulus by 102.2 %, in notched impact strength by 217.8 % and flexural strength by 2.6 %, and however they showed a decrease in tensile strength by 15.1 %. Both the melt index and notched impact strength of the composites tended to increase with the addition of 1phr EBS.

Study on Evaluation Criterion of Formation of Polypropylene Cylindrical Crystal by Co-injection Molding

2018, 32 (08): 40-45; DOI: 10.19491/j.issn.1001-9278.2018.08.007

Abstract ( 415 )

Co-injection molded isotactic polypropylene specimens were made at three different core injection rates of 20, 40,60 mm/s. The microstructure of the molded specimens was observed by polarizing optical microscopy. On the basis of the numerical and experimental results, the temperature field, shear rate field, and shear stress filed at the selected locations were calculated and a formation criteria equation for cylindrulite was established in terms of energy variation. Most of all, a quantitative criterion was established for the formation of polypropylene cylindrulite during the processing, which suggested that the cylindrulite could be formed in the range of ［170, 222］ and ［252, 458］.

Study on Mechanical and Absorbent Properties of Poly(lactic acid)/Wheat Straw Fiber Composites

2018, 32 (08): 46-51; DOI: 10.19491/j.issn.1001-9278.2018.08.008

Abstract ( 667 )

The poly(lactic acid) (PLA)/wheat straw fiber (WSF) composites were prepared by a melt-blending process. The effects of coupling agent, γ-aminopropyltriethoxysilane (KH550), on the mechanical properties, moisture absorption and interface performance of the composites were investigated. Moreover, the chemical structure of WSF was characterized by FTIR, and the morphology of the composites was detected by SEM. The results indicated that the reaction between the WSF and KH550 reduced the surface polarity of WSF, and the composites exhibited a decreasing trend in mechanical properties with an increase of WSF content. The mechanical properties of the composites were improved due to the modification of WSF with KH550, and their water absorption was also reduced after the WSF were modified by KH550. The SEM observation suggested that the interfacial compatibility of PLA with WSF was enhanced due to the surface treatment of WSF with KH550.

Effect of PS on Mechanical Properties and Precision of SLS Sintered Parts with PS/CF Composite

2018, 32 (08): 52-57; DOI: 10.19491/j.issn.1001-9278.2018.08.009

Abstract ( 632 )

Polystyrene/carbon fiber (PS/CF) composite powders were prepared by using polystyrene (PS) as matrix material, and then the SLS parts were prepared with this composite powders at a preheating temperature of 80 ℃ with a laser power of 30 W and a delamination thickness of 0.25 mm. The effects of particle size and content of matrix material on the mechanical properties and precision of SLS parts were studied intensively. The results indicated that the particle size of the composite powders met the requirement of SLS technology. When the mean particle size was 75 μm and the PS/CF mass ratio is 9∶1, the fusion effect between PS and CF was optimal. The bending, tensile and impact strength of the sintered parts reached 6.88 MPa, 2.97 MPa and 2.98 kJ/m2, respectively, and meanwhile their absolute dimensional deviations were only 0.8 %, 0.22 % and 1.6 % in x, y and z directions, respectively. Compared to the sintered parts made from pure PS under the same condition, the sintered parts made from the composite exhibited an increase in bending strength by 62.06 %, in tensile strength by 74.29 % and in impact strength by 83.95 %, and their dimensional accuracy increased by 5.44 %, 69.44 % and 81.34 % in x, y and z directions, respectively.

Preparation and Applications of Polyhedral Pigments with Metallic Effect

2018, 32 (08): 58-64; DOI: 10.19491/j.issn.1001-9278.2018.08.010

Abstract ( 536 )

In this work, with the help of magnetron sputtering coating process, the deposition of aluminum on the surface of micron-sized silica powders was carried out by using aluminum target as a sputtering source to achieve a new type polyhedral metallic pigment on a large scale. The differences between the polyhedron metallic pigments and traditional aluminum pigments were analyzed, which were mainly focused on the flow lines and weld lines in plastic parts. The results indicated that the polyhedron metallic pigments presented a better metallic texture in comparison with the traditional aluminum ones. Furthermore, the flow lines in the relevant parts almost disappeared completely, and the weld lines were also reduced significantly. The reasons for the differences between the flow and weld lines were further analyzed and explained theoretically. The effect of polyhedron metallic pigments on the physical properties of plastic parts was investigated, and meanwhile the effect of processing technology on the appearance of polyhedral pigments was also evaluated. The free-spraying parts with no flow lines could be directly injection molded by using a mixture of the polyhedral metallic pigments and thermoplastics. This processing procedure is more cost-effective and more ecologically friendly. The free-spraying parts have been approved by consumers due to a great commercial success.

Preparation and Characterization of Polyhexyl Ester/Nano-ZnO Electrospun Antibacterial Membranes

2018, 32 (08): 65-71; DOI: 10.19491/j.issn.1001-9278.2018.08.011

Abstract ( 450 )

Poly(ε-caprolactone) (PCL)/nano-ZnO composite microfibers were prepared by electrospinning, and the effects of electrospinning voltage and ZnO content on the diameter, thermal and crystallization properties of the composite fibers were investigated by scanning electron microscopy and differential scanning calorimetry. The antibacterial performance of the composite fibers was evaluated by an antibacterial experiment. The results indicated that the diameter of composite fibers increased at first and then tended to decrease with an increase of voltage, and their melt temperature (Tm) and lamellar thickness of crystals (Lc) exhibited the same variation trend. However, their diameter, Tm and Lc increased gradually at different voltages when the amount of ZnO increased. The composite fibers achieved an optimal antibacterial property at a ZnO content of 2 wt %, and such an antibacterial property was well maintained up to 60 days.

Study on PC/ABS Alloy with Low Odor and Volatile Organic Compounds Content

2018, 32 (08): 72-78; DOI: 10.19491/j.issn.1001-9278.2018.08.012

Abstract ( 768 )

PC/ABS alloys were prepared by melt blending and the effects of adsorbents and extractants on the mechanical performance and the odor and volatile organic compounds (VOC) contents of the resulting alloys were investigated by mechanical tests and thermal desorption gas phase/mass spectrometry analysis. The results indicated that the odor of the alloys increased with increasing the amount of adsorbents and extractants, but the total VOC content decreased. Furthermore, there was no side-effect found on the mechanical properties of the alloys. In addition, the hygroscopicity of the alloys became worse due to the increase of the amount of adsorbents. With the addition of 5 wt % adsorbents, the water absorption of the alloys increased by a factor of 1.7 after naturally stored for 480 h. When the dosages of adsorbent and extractant were 0.5 and 1.5 wt %, respectively, the alloy achieved the optimum comprehensive performance, the odor intensity reached level 3, the comfort level was improved up to level 0, and the total VOC was reduced by 57.9 % compared to the pure PC/ABS alloy. The ecological friendly performance of the alloy by using extractant was better than that by adsorbent, but a combination of them could generated a much better effect than the individuals.

Mechanisms of Normal Stress Difference Induced Interfacial Distortion for Viscoelastic Multiphase Stratified Flows

2018, 32 (08): 79-85; DOI: 10.19491/j.issn.1001-9278.2018.08.013

Abstract ( 524 )

A relevance theory among the interfacial deformation-secondary flow-second normal stress difference was established by computational simulation, and the mechanisms of interfacial deformation induced by the second normal stress difference driven secondary flow was proposed. The investigation indicated that the interfacial morphology evolved from concave downward to concave upward when the Giesekus model parameter alpha increased from 0.1 to 0.45. However, in the side wall region, the second normal stress difference of the melt along the interface became negative. If the absolute value of the second normal stress difference at the lower layer was greater than that of the upper melt, the secondary flows were all downward movement along the die wall, where a downward concave interface deformation were induced. Oppositely, the secondary flows are all upward movement along the die wall, where an upward concave interface deformation was induced. The absolute value of the second normal stress difference for the upper melt increased with an increase of alpha, whereas the melt of the lower layer increased at first and then tended to decrease. This lead to the downward movement of the secondary flow. The upward movement of the secondary flow was resulted by a value of alpha less than 0.25. However, when alpha was greater than 0.25, the positive and negative evolution of the interface deformation was induced definitely.

Finite Element Analysis of Buried Polyethylene Gas Pipeline Near Impact-loading Zone

2018, 32 (08): 86-91; DOI: 10.19491/j.issn.1001-9278.2018.08.014

Abstract ( 444 )

To analyze the effect of impact load on the safe operation of buried polyethylene gas pipelines near the impact loading zone, a finite element analysis software ABAQUS was used to analyze the stress variation of polyethylene pipe with the pipe-soil interaction finite element model. The variation of stress and deformation was analyzed with different polyethylene pipe material models, soil properties and impact velocity. The results indicated that the impact velocity of polyethylene pipeline did not show any change due to the impact with relatively short time. There was a significant protective effect on the pipeline from the soil properties and reasonable burying depth. The polyethylene pipeline exhibited an increase in maximum stress with an increase of internal pressure of the pipe, which has an approximately linear relationship. The area near the impact zone was found to reach a failure limit easily for polyethylene pipe.

Co-curing Manufacturing Process for Composite Fuselage and Beam of Small-sized Unmanned Aerial Vehicles

2018, 32 (08): 92-95; DOI: 10.19491/j.issn.1001-9278.2018.08.015

Abstract ( 597 )

This paper introduced the fuselage structure and traditional manufacturing process of unmanned aerial vehicle (UAV) as well as the problems appearing in the processing procedure. Furthermore, this paper also introduced a pressure-pad manufacturing process for the small-sized UAV and a co-curing process for the composite honeycomb sandwich plate with a load beam, which could be applied in the manufacture of the frame-beam honeycomb sandwich structure. Compared to the traditional process, this method can reduce the manufacture cost, improve the surface quality of composite parts and shorten the manufacture cycle of UAV.

Study on Application of Genetic Algorithm in Parameters Fitting of Dynamic Viscoelastic Model

2018, 32 (08): 94-104; DOI: 10.19491/j.issn.1001-9278.2018.08.016

Abstract ( 389 )

To study the effect of the elastic deformation of polymeric materials on the deformation of microstructured products, a computational simulation was conducted to investigate the hot rolling press of a TOPAS-COC polymer. Moreover, based on the data fitting of the viscoelastic generalized-Maxwell model for the TOPAS-COC polymers, an improved genetic algorithm was proposed. By comparing the genetic algorithm and least-squares fitting results, it was found that the improved genetic algorithm was superior to the least-square method to accurately obtain model parameters of dynamic viscoelastic model. In addition, the principle of translation was used to obtain the master curve at a reference temperature, and the model parameters were input into Abaqus finite element software for simulation. The effects of the process parameters were analyzed on the basis of orthogonal experimental design, and the results indicated that the elastic recovery of the microstructure due to the elastic deformation could be reduced by improving temperature or reducing the preloading amount and rolling speed decreases with higher temperature, lower preload amount and the rolling speed.

Preparation and Evaluation of Surface Grafting of Maleic Anhydride onto Ultra-high Molecular Weight Polyethylene Powder

2018, 32 (08): 105-110; DOI: 10.19491/j.issn.1001-9278.2018.08.017

Abstract ( 542 )

In this study, a chemical graft of maleic anhydride (MAH) was performed onto the surface of ultra-high molecular-weight polyethylene (PE-UHMW) powders by free-radical co-polymerization, and benzoyl peroxide (BPO) was used as an initiator in this reaction. The effects of reaction time and initiator and MAH concentrations on the grafting co-polymerization were studied. The chemical properties and morphology of MAH-grafted PE-UHMW powders were investigated by ATR-FTIR, XPS, SEM and TGA. The results indicated that the MAH molecule was successfully grafted onto the surface of PE-UHMW powders, and the graft ratio and crosslinking degree of the MAH-grafted PE-UHMW increased significantly due to an increase in reaction time and initiator concentration. However, with increasing the MAH concentration, its graft ratio increased but the crosslinking degree decreased. This suggests that the increase of MAH concentration might suppress an improvement in crosslinking degree partly. A maximum graft ratio of 1.62 wt % and a maximum crosslinking degree of 69 wt % were achieved for the PE-UHMW powders.

Study of Trimellitic Acid Polyester for PVC Plasticizer

2018, 32 (08): 111-115; DOI: 10.19491/j.issn.1001-9278.2018.08.018

Abstract ( 459 )

In this study, an ecological-friendly and biodegradable trimellitic acid polyester (P-Gl-TMAI) plasticizer was synthesized by the esterification and polycondensation reactions between trimellitic anhydride (TMA) and glycerin (GI). The as-prepared P-GI-TMAI was introduced into poly(vinyl chloride) (PVC) resin, and then the compatibility, mechanical properties and migration résistance of the resulting compounds were investigated. Moreover, the dioctyl phthalate (DOP) plasticizer as a reference was also used for a comparative investigation. Compared to DOP, P-GI-TMAI exhibited some small holes on the surface of test panel, indicating that P-GI-TMAI was more compatible with PVC. The PVC compound plasticized by P-GI-TMAI achieved the tensile strength of 18.99 MPa and elongation at break of 454.89 %. The results obtained from volatility and extraction tests indicated that there were only 3.02 % and 15.31 % of mass-loss rate for the compounds plasticized by P-GI-TMAI, indicating much better impact and migration resistance that those by DOP.

Synthesis and Properties of Novel Multifunctional Antioxidants

2018, 32 (08): 116-121; DOI: 10.19491/j.issn.1001-9278.2018.08.019

Abstract ( 416 )

A novel type of macromolecular antioxidant HACP with a P-N structure and six new functional hindered phenol branches was synthesized in a two-step procedure. An amine terminated-cyclotriphosphazene intermediate was first synthesized by using six 4-hydroxy phenyl acetamide and hexachlorocyclotriphosphazene as the raw materials, and then HACP was synthesized sucessfully through the amidation condensation reaction of this intermediate with β-(3,5-diterbutyl-4-hydroxyphenyl) propionyl chloride. The chemical structure of HACP was analyzed by FTIR and NMR spectra, and a comparative investigation on the thermal and oxidation resistance properties of modified polypropylene (PP) by HACP and Irganox 1010 were performed. The TGA results indicated that the HACP-modified PP achieved a better thermal stability by presenting a higher characteristic temperature at the weight loss of 5 wt %. The HACP and Irganox 1010-modified PP compounds well preserved their mechanical properties after 2-week aging, whereas the mechanical properties of pure PP decreased a lot. Compared to pure PP, the HACP-modified PP showed a decrease in tensile strength by 11.6 %, whereas the Irganox 1010-modified one presented a more significant decrease by 11.6 %.

Degradation Properties of Poly（Propylene Carbonate）/ Poly（Lactic Acid）Blends in Marine Environment

2018, 32 (08): 122-130; DOI: 10.19491/j.issn.1001-9278.2018.08.020

Abstract ( 509 )

This paper reported an investigation on the degradation properties of poly(propylene carbonate) (PPC)/poly(lactic acid) (PLA) blends in a marine environment. The mechanical properties, surface microstructure, chemical structure, weight loss, thermal properties and crystalline properties of the blends were evaluated by means of mechanical measurements, scanning electron microscope, attenuated total reflection infrared spectroscopy. The results indicated that the tensile strength of the blends at the PPC/PLA mass ratio of 10/90, 30/70, 50/50 and 70/30 increased continuously with an increase of degradation period, and however their elongation at break decreased drastically after a degradation period of 30 days and then kept a stable value. There were clear pores and defects found on the surface of pure PPC and PLA resins after they were placed in a marine environment for 240 days, whereas the blends at a PPC/PLA mass ratio of 50/50 did not exhibit any pores and defects. Both pure PPC and pure PLA exhibited an increasing trend in hydroxyl index, carbonyl index and lactic acid index, and such a trend become more significant at the first 30-day degradation period, whereas the blends at a PPC/PLA mass ratio of 50/50 showed no change. The weight loss of the blends mainly took place at the first 30-day degradation period, which resulted in a weight loss rate of less than 10 wt %, indicating the degradation of blends was not significant. Moreover, the blends showed an increase in characteristic temperature at a weight loss of 5 wt %, whereas their characteristic temperature at the maximum weight-loss rate did not change any more.

Simulation of Mixing Performance of Co-rotating Twin-screw Elements for Solid Propellants

2018, 32 (08): 131-136; DOI: 10.19491/j.issn.1001-9278.2018.08.021

Abstract ( 509 )

In this work, four types of screw elements were designed for the extrusion process of solid propellants, and the rheological properties of solid propellant slurry was investigated. Furthermore, the flow fields of the four screw elements were simulated by the Polyflow software. The shear rate, weight-average shear stress, mean reflux coefficient and cumulative residence time distribution were analyzed to characterize the mixing performance and flow field characteristics of screw elements. The dispersive and distributive mixing performance was comparatively investigated for these four screw element. The results indicated that the KB and SE elements had good comprehensive mixing performance, which favored the mixing process of solid propellants.

Optimization Design of Micro Injection Mold Based on CAE

2018, 32 (08): 137-142; DOI: 10.19491/j.issn.1001-9278.2018.08.022

Abstract ( 457 )

The structure of micro injection mold was optimized on the basis of the CAE analysis, and the feed system, venting system and temperature control system were optimized according to rheological data of polymer by the Autodesk Moldflow Insight software. These results were used as a reference to conduct the design of micro mold. The μIM parts were molded successfully to verify the accuracy of optimization process, and the experimental results obtained compared with short shot micro parts was in good agreement with those from the CAE ones. The melt shape appearing at the flow front seems to be flush due to the micro-sizing effect.