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2019, Volume 33 Issue 2 Publication date: 26 February 2019 Previous Issue Next Issue

Study on Compatibilizing Modification of PLA/PPC Blends with Long-Chain Hyperbranched Polymer

2019, 33 (2): 1-7; DOI: 10.19491/j.issn.1001-9278.2019.02.001

Abstract ( 425 ) PDF (1499 KB)( 244 )

A grafting modification was performed for the hyperbranched polyester synthesized by a “one-step” method to obtain a sort of hyperbranched polymer with a large number of long-chain stearic acid at the end (LCHBP), and the chemical structure of LCHBP was characterized by Fourier-transform infrared spectroscopy, nuclear magnetic spectroscopy and hydroxyl value titration. The polylactic acid (PLA)/polypropylene carbonate (PPC) blends were modified with LCHBP through melt blending, and then their thermal performance, mechanical properties and morphologies of fracture surface were investigated by using differential scanning calorimeter, electronic universal testing machine and scanning electron microscope. The results indicated that the ΔTg of PLA/PPC/LCHBP blends decreased significantly with the addition of LCHBP, indicating an improvement in compatibility of PLA and PPC. Compared to PLA/PPC binary blends, the PLA/PPC/LCHBP ternary blends showed a remarkable increase in elongation at break and impact strength, whereas their tensile strength remained unchanged. The tensile strength of ternary blends increased by 61 % and their elongation at break increased by 367 % with the addition of 2.0 wt% LCHBP.

Study on Preparation and Properties of Flame-Retardant EVA Material

2019, 33 (2): 8-12,34; DOI: 10.19491/j.issn.1001-9278.2019.02.002

Abstract ( 862 ) PDF (1103 KB)( 274 )

The flame-retardant effect of the self-made piperazine intumescent flame retardant (IFR) on ethylene-vinyl acetate copolymer (EVA) was investigated by limited oxygen index (LOI) measurement, vertical burning experiment, smoke density, cone calorimetry and scanning electron microscopy. The results indicated that the flame-retardant EVA material achieved the LOI of 37 vol% with the addition of 30 wt% IFR and reached a V-0 classification in the UL 94 vertical burning experiment. The smoke density of flame-retarded EVA material was very low under the combustion conditions with flame and without flame, and their peak heat release rate decreased to 156 kW/m2, which was only equal to 21.8 % of the value for pure EVA. A dense expanded carbon layer was formed after combustion. The flame-retarded EVA material exhibits a low moisture absorption rate and good mechanical properties and therefore can meet the requirements of the RoHS environmental protection.

Study on Foaming Behavior and Slow Resilience Performance of Polyurethane/Coffee Ground Foams

2019, 33 (2): 13-17; DOI: 10.19491/j.issn.1001-9278.2019.02.003

Abstract ( 555 ) PDF (1032 KB)( 240 )

The slow resilient PU foams with high loadings of coffee grounds were prepared by a reactive blending method, and their slow resilience performance, mechanical properties, thermal insulation and foaming behaviors were investigated. The results indicated that the hydroxyl groups on coffee grounds could react with isocyanate groups of MDI, but the foaming reaction was inhibited, resulting in a decrease in the amount of foaming gas. In addition, the cellular structure and foaming properties of the PU foams were greatly influenced by the addition of coffee grounds. With the content of coffee grounds as high as 40 wt%, the open cell ratio of the PU foams decreased from 57 % to 15 %, whereas their tensile strength and moduli were improved to 0.15 MPa and 33.5 MPa, respectively. Moreover, the thermal conductivity of the PU foams decreased to 0.050 W/（m·K）, and their resilience time exceeded 3 s at 37 ℃. The addition of coffee grounds could generate a positive effect on the cellular structure and performance control of low-resilient PU foams.

Effect of Surface Modification on Properties of Coir-Fiber-Reinforced Polypropylene Composites

2019, 33 (2): 18-23; DOI: 10.19491/j.issn.1001-9278.2019.02.004

Abstract ( 460 ) PDF (3370 KB)( 221 )

The surface of coir fiber was treated with different concentrations of alkali solution, coupling agent or their mixture, and then the coir-fiber-reinforced polypropylene (PP) composites were prepared by a compression-molding technology. The effect of surface modification on the surface characteristics of coir fiber and the mechanical properties of composites were investigated. The results indicated that the combination of alkali and coupling agent was an optimum modification way to improve the mechanical properties of the composites. The tensile strength of the composites increased with the concentration of coupling agent at the same alkali concentration. The modification of coupling agent generated a more significant effect on the mechanical properties than that of alkali. Moreover, the modification of coupling agent also influenced the flexural strength of the composites remarkably, and the mechanical properties were found to increase linearly with the concentration of coupling agent.

Study of Preparation and Properties of POM/Sepiolite Fiber Composites

2019, 33 (2): 24-28; DOI: 10.19491/j.issn.1001-9278.2019.02.005

Abstract ( 513 ) PDF (1609 KB)( 236 )

Sepiolite-fiber-reinforced polyoxymethylene (POM) composites were prepared, and the effect of fiber surface modification with a silane coupling agent, KH550, on the mechanical and tribological properties of the composites were investigated. The mechanical and tribological properties of the composites were improved with an increase of sepiolite fiber content. When 5.0 wt% of sepiolite fiber was added, the composites gained optimum mechanical and tribological properties and achieved the tensile strength of 68.43 MPa, the flexural strength of 89.81 MPa, the flexural modulus of 3600.61 MPa and the impact strength of 285.5 kJ/m2, which increased by 28.6 %, 51.9 %, 79.1 % and 8.8 %, respectively, compared to pure POM. However, the composites presented a friction coefficient of 0.072 and a wear loss of 3.6 mg, which decreased by 65.9 % and 35.7 %, respectively.

Synergistic Effect of PLA/CaCO₃ on Properties of Polypropylene Compounds

2019, 33 (2): 29-34; DOI: 10.19491/j.issn.1001-9278.2019.02.006

Abstract ( 546 ) PDF (1600 KB)( 270 )

PP/PLA/CaCO3 compounds were prepared by a melt blending method, and the effects of PLA and CaCO3 nanoparticles on the mechanical properties, thermal property, rheological behavior and crystallization of compounds were investigated. The results indicated that the mechanical properties of compounds were improved with the addition of PLA due to the formation of a PLA continuous spatial network in the PP matrix. The compounds achieved optimum comprehensive mechanical performance when 20 wt% of PLA was introduced. Their tensile strength and impact strength increased by 5.1 % and 54.4 %, respectively, but the elongation at break decreases by 62.5 % compared to pure PP. A significant improvement in mechanical properties is ascribed to the “ball bearing” and nucleation effects of CaCO3 in the PP matrix. The CaCO3 nanoparticles were observed to be distributed in the PP/PLA matrix uniformly at a content of 15 wt%, leading to an optimum grain refining effect accordingly. The PP/PLA/CaCO3 ternary compounds obtained an increase in tensile strength by 15.2 %, in elongation at break by 2.7 % and in impact strength by 5.6 % compared to PP/PLA binary compounds.

Effect of Maleic Anhydride Grafted PS on the Foaming Behavior of PS/PLA Blends

2019, 33 (2): 35-39; DOI: 10.19491/j.issn.1001-9278.2019.02.007

Abstract ( 616 ) PDF (2195 KB)( 196 )

PS/PLA blends were prepared by melt blending, and the effects of PLA content and maleic-anhydride (MAH)-grafted PS on the solubility of CO2, rheological behavior, phase structure and foaming behavior of the blends were investigated. The results indicated that the solubility of CO2 in PS/PLA blends was effectively improved by PLA, and its solubility increased by 22 % with the addition of 25 phr PLA compared to that in pure PS. The addition of MAH-g-PS significantly enhanced the compatibility of PLA and PS, thus reducing the particle size of dispersed phase and the foam density of PS/PLA blends.

Study on Crystallization and Mechanical Properties of Continuous Carbon-Fiber-Reinforced PA66 Composites

2019, 33 (2): 40-46，61; DOI: 10.19491/j.issn.1001-9278.2019.02.008

Abstract ( 674 ) PDF (1920 KB)( 455 )

The prepreg tapes based on PA66 and carbon fiber (CF) were prepared by a melt-impregnation method, and the effect of CF content on their tensile properties and crystallization-melt behaviors were investigated by using universal material testing machine, diffractometer, differential scanning calorimeter, scanning electron microscope, dynamic thermomechanical analyzer and thermogravimetric analyzer. The results indicated that the introduction of CF led to a change in crystalline structure of α-form, which promoted the heterogeneous nucleation of PA66 and improved the crystallization temperature accordingly. The bimodal melting behavior of PA66 became more significant in the presence of CF, and its higher melting temperature tended to increase first and then to decrease. This may be due to the nucleation effect of CF, which induced and promoted the crystallization of PA66. Moreover, a grain refinement phenomenon was observed due to the huge amounts of crystal nucleus, thus resulting in a decrease of melting temperature. The increase of CF content could make nucleation saturated, which increased the number of nucleus and improved the melting temperature accordingly. The tensile strength, storage modulus and loss modulus of the prepreg tapes were improved with an increase of CF content.

Study on Flame-Retardant Modification of Polylactide with Znic Phenylphosphinate

2019, 33 (2): 47-51; DOI: 10.19491/j.issn.1001-9278.2019.02.009

Abstract ( 440 ) PDF (734 KB)( 295 )

Znic phenylphosphinate (ZnP) was synthesized by a coprecipitation method, and then a series of polylactide (PLA)/ZnP compounds were prepared by melt blending. The effect of ZnP on the thermal stability, flame retardancy and combustion characteristics of PLA/ZnP compounds were investigated by thermogravimetric analysis, limiting oxygen index (LOI), vertical burning experiment and microscale combustion calorimeter. The results indicated that the incorporation of ZnP improved the degradation temperature and char yield of the compounds, and the degradation temperature increased by 8 ℃ with the addition of 30 wt% ZnP compared to pure PLA. The compounds also achieved a char yield of 18.5 wt% at 750 ℃. Most of all, ZnP could enhance the flame retardancy of PLA, and a UL94 V-2 classification and an LOI of 24.0 vol% were achieved for the compound containing 30 wt% of ZnP. The peak heat release rate of the compounds was also reduced by 24.9 % compared to pure PLA, indicating a significant improvement in fire safety.

Preparation and Performance of Porous Polystyrene Microspheres for Adsorption

2019, 33 (2): 52-56，68; DOI: 10.19491/j.issn.1001-9278.2019.02.010

Abstract ( 610 ) PDF (740 KB)( 315 )

The polystyrene (PS) microspheres with a micro-mesoporous structure were synthesized by suspension copolymerization using maleic anhydride (MAH) as a comonomer, followed by a hyper-crosslinking reaction using dichloromethane as a crosslinking agent and anhydrous aluminum chloride as a catalyst. The resultant PS microspheres were further characterized to determine their chemical structure and morphology by specific surface area test, scanning electron microscopy, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Moreover, the water absorption and pentobarbital adsorption performance of the microspheres were measured. The results indicated that the specific surface area of the microspheres was significantly improved by the hyper-crosslinking reaction. The water absorption and pentobarbitol adsorption performance were also enhanced with an increase of MAH content. The microspheres achieved a maximum pentobarbital adsorption capacity of 91.90 % at the MAH content of 20 wt%.

Numerical Simulation of Two-stage Drawing Melt Electrospinning

2019, 33 (2): 57-61; DOI: 10.19491/j.issn.1001-9278.2019.02.011

Abstract ( 529 )

A finite element analysis software COMSOL was adopted to simulate the electrospinning electric field distribution according to the drawing mechanism of melt electrospinning, and the reliability of analysis results was verified by experiments. Mesh dividing was conducted for the model in the COMSOL software, and the simulation was carried out by using experimental data. Finally, the experimental verification was performed to confirm that the second-stage drawing could generate a better spinning effect, which was in good agreement with the simulation results.

Experimental Study of SLS Process Parameters Coupling of PS/PET/GF Ternary Composites

2019, 33 (2): 62-68; DOI: 10.19491/j.issn.1001-9278.2019.02.012

Abstract ( 399 ) PDF (2001 KB)( 267 )

To clarify the effect of selective laser sintering process parameters on the quality of sintered parts made from polystyrene (PS)/polyester fiber (PET)/glass fiber (GF) ternary composites, three process factors including thickness, scanning speed and distance were selected for the coupling experiment, and the variation law and reasons of dimensional accuracy and bending strength were analyzed and summarized. The size accuracy in the x and y directions of the sintering parts was seldom affected by the variation of process parameters, whereas there was a significant influence on the accuracy in the z direction. The bending strength was mainly influenced by the laser energy density during the forming process. The results indicated that the bending strength of the sintered parts decreased with an increase of dimensional precision. This result provides an experimental evidence for the selection of technological parameters to improve the quality of the sintered parts.

Experimental Study of Sink Mark of External Gas-Assisted Injection-Molded Parts with Ribs

2019, 33 (2): 69-74; DOI: 10.19491/j.issn.1001-9278.2019.02.013

Abstract ( 456 ) PDF (1211 KB)( 210 )

Experimental study on the depth of the sink marks caused by different ribs of parts during the external gas-assisted injection molding (EGAIM) process was performed on the basis of a laboratory-developed EGAIM system. The single factor method was adopted to investigate the effects of mold temperature, melt temperature, gas delay time, gas holding pressure and gas holding time on these sink marks. The results indicated that there were different effects on the sink marks of part with different ribs. The results from an orthogonal experiment demonstrated that the gas delay time and gas holding pressure were two main factors that influenced the depth of sink mark. The EGAIM process along with the optimal process parameters could well eliminate the sink marks by designing the aspect ratio of rib. The sink mark revealed a depth of 1.2 μm at an aspect ratio of rib width/part thickness up to 1.5, which was less than the value obtained at the conventional aspect ratio of 0.6. These results indicated that the optimized processing conditions of EGAIM could effectively eliminate the sink mark caused by the thicker ribs and improved the design freedom of the parts accordingly.

Synthesis and Preparation of Carboxylic-Acid-Type Waterborne Polyurethane Modified with Nano-Cellulose Whiskers

2019, 33 (2): 75-81; DOI: 10.19491/j.issn.1001-9278.2019.02.014

Abstract ( 406 ) PDF (2123 KB)( 215 )

The vegetable oil-based waterborne polyurethane (WPU) was synthesized by using castor oil, 2-2-bis(hydroxymethyl)propionic acid and isophorone diisocyanate polyurethane as raw materials (IPDI) and then was mixed with nano-cellulose whiskers (CNC) by acid hydrolysis under ultrasonication. The coating films of WPU/CNC composite were prepared through strong hydrogen bonding between the CNC filler and WPU matrix. The microstructure, morphology and properties of the coating films were investigated by Fourier-transform infrared spectroscopy, scanning electron microscopy, particle-size analysis, thermogravimetric analysis, differential scanning calorimetry and mechanical measurements. The results indicated that the coating films achieved good dispersibility and excellent performance when 0.25 wt% of CNC was added. The tensile strength of the composites was improved from 17.56 MPa to 27.96 MPa. Moreover, the thermal stability of coating films, the decomposition temperature of hard segment and the glass transition temperature of soft segment were also improved.

Study on Thermal Degradation and Flame Retardant Mechanisms of Aluminum Diethylphosphinate

2019, 33 (2): 82-85，130; DOI: 10.19491/j.issn.1001-9278.2019.02.015

Abstract ( 1901 )

This article reported an investigation on the chemical and physical evolutions during the thermal degradation process of aluminum diethylphosphinate (AlPi). The experimental results indicated that the phosphorus species were released to the gas phase through the sublimation of AlPi. On the other hand, the competitive thermal decomposition might reduce the flame-retarding efficiency by leaving phosphorus species in the solid phase. At the temperature close to a flaming temperature, the sublimated AlPi was further split into phosphorus atom, which could form the flame-retarding radical scavengers accordingly.

Study on Annealing of Polypropylene Controlled with Phosphate Sodium and Talc

2019, 33 (2): 86-90，108; DOI: 10.19491/j.issn.1001-9278.2019.02.016

Abstract ( 467 ) PDF (1906 KB)( 225 )

Polypropylene/Nucleating Agent Sodium Phosphate/Talc (PP/NA-40/Talc) system were prepared by extrusion blending method. The effects of annealing time and annealing temperature on mechanical properties, heat distortion temperature and crystallization properties of PP/NA-40/Talc system were studied. It is proved by DSC, XRD and FTIR that the annealing treatment can improve the crystallinity and mechanical properties of PP/NA-40/Talc system. The results show that the mechanical properties, the heat distortion temperature and the crystallization properties of PP/NA-40/Talc system are positively correlated with annealing time and annealing temperature. Especially after annealing at 120 ℃ for 2 h, the flexural modulus, the heat distortion temperature and the crystallinity reached 2516.0 MPa, 136.9 ℃ and 49.5 % respectively.

Preparation and Properties of MA-AMPS-AM Copolymer Scale Inhibitor for Circulating Water

2019, 33 (2): 91-96; DOI: 10.19491/j.issn.1001-9278.2019.02.017

Abstract ( 510 ) PDF (1307 KB)( 383 )

A maleic anhydride-co-2-acrylamide-2-methylpropanesulfonic acid-co-acrylamide copolymer was synthesized by radical polymerization using maleic anhydride (MAH), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and acrylamide (AM) as comonomers, and its structure was characterized by Fourier-transform infrared spectroscopy. This copolymer was used as a scale inhibitor for circulating water, and the effects of inhibitor concentration, water temperature and pH value on the inhibiting effect of the inhibition system were investigated. Moreover, the calcium scaling morphology was observed by scanning electron microscopy. The results indicated that this copolymer could act as a good scale inhibitor for CaCO3 and CaSO4 and achieved a scale inhibition rate of 93.8 % for CaCO3 at the concentration of 15 mg/L and 92.8 % for CaSO4 at the concentration of 18 mg/L. In addition, this copolymer exhibited high inhibition efficiency at a water temperature of 80 ℃, and it could destroy the regularity of calcium scale crystals, thus resulting in a large number of defects in the calcium scale crystals and giving a scale-inhibiting effect.

A New Measuring Device for Solubility of Supercritical Carbon Dioxide in Polymers

2019, 33 (2): 97-102; DOI: 10.19491/j.issn.1001-9278.2019.02.018

Abstract ( 496 ) PDF (1030 KB)( 231 )

A new device was designed for measuring the dissolution behavior of supercritical CO2 in polymers by means of a volume method, and its feasibility was verified by measuring the solubility and dissolution rate of supercritical CO2 in polystyrene in the temperature range of 443.15~463.15 K and in the pressure range of 7.5~9.5 MPa. The relative deviation between the experimental and calculated values was less than 20 %, and the diffusion coefficient calculated by the experiment was identical to the reported one in literature by the same order of magnitude, indicating that this new device could precisely measure the solubility of supercritical CO2 in polymers.

Mold Structure Design of Self-Lubricating Demolding Mechanism of Rotary Wheel Bevel Gear Based on CAE Analysis

2019, 33 (2): 103-109; DOI: 10.19491/j.issn.1001-9278.2019.02.019

Abstract ( 367 ) PDF (2444 KB)( 183 )

To meet the requirements of the formation of the pinion parts in the rotary disk of crushing machine, a CAE-aided analysis and a UG 3D design method were adopted to design the six-plate die point gate structured mold with one mold and two cavities. To realize the automotive production of injection-molded plastic parts, the mold structure was design by employing a five-point-open-type mold base and a one-half-open slider to perform the automatic demolding of plastic parts. In the case of mechanism design for the half slider, the traditional structure of half slider was modified to set a limiting hook below the half slider to ensure that two side slide blocks in the half slider mechanism could synchronously complete demolding within the plastic pieces of the outer wall on the side of the concave mould. Moreover, to realize the lining plastic helical characteristics on the core self-lubricating rotating demolding, the dynamic model on the side of twice ejection device performed two actions to complete demolding for the plastic parts. This could keep a good turn of the automotive production for injection-molded parts. The mould structure designed by this work is reasonable, and the mechanism is ingenious, which can provide a beneficial reference for the same type of injection molded parts.

Research Progress of Mesoporous Silica Materials in Hemostasis Applications

2019, 33 (2): 110-118; DOI: 10.19491/j.issn.1001-9278.2019.02.020

Abstract ( 567 )

The types of mesoporous silica materials and synthetic methods were introduced and the research status of hemostatic materials based on mesoporous silica was reviewed. These hemostatic materials included mesoporous silica materials, the combination of mesoporous silica and organic materials, the combination of mesoporous silica and metal ion materials, and they demonstrated the good hemostatic and antibacterial properties due to the use of mesoporous silica. Finally, the prospect in the application of mesoporous silica combined with other materials for hemostasis applications was discussed.

Application Status of Polymer Materials in the Field of Military Package

2019, 33 (2): 119-122; DOI: 10.19491/j.issn.1001-9278.2019.02.021

Abstract ( 600 ) PDF (1146 KB)( 352 )

This article introduced the composition characteristics and special application requirements of military materiel and analyzed various factors that may result in the performance degradation or damage of military materiel during shipment, handling, indeterminate storage and distribution to consignees worldwide. The preservation countermeasures were proposed, and meanwhile the application requirement and status of polymer materials in the field of military package were overviewed.

Research Progress in Flow-Induced Cylindrites of Semi-Crystalline Polymers

2019, 33 (2): 123-130; DOI: 10.19491/j.issn.1001-9278.2019.02.022

Abstract ( 359 ) PDF (1023 KB)( 293 )

This paper introduced the structures of the cylindrites formed by different processing parameters and equipments. The effects of material types including macromolecular structures and processing conditions on the formation of cylindrites were analyzed. Some suggests about how to improve the research progress in flow-induced cylindrites were proposed on the basis of the current research achievements.

Research Progress in Full-Notch Creep Test of Polyethylene Materials

2019, 33 (2): 131-137，143; DOI: 10.19491/j.issn.1001-9278.2019.02.023

Abstract ( 416 ) PDF (1424 KB)( 262 )

This paper introduced the research principles and standards of full-notch creep test (FNCT) as a rapid evaluation method proposed by foreign scholars for the long-term test of slow crack growth resistance of polyethylene (PE) pipe. The FNCT results were described in detail under the geometric shape, surfactant, tensile stress and temperature conditions, and the future development prospects for evaluation of PE gas pipelines with the FNCT technology was also discussed.

Preparation and application of expanded polytetrafluoroethylene

2019, 33 (2): 138-143; DOI: 10.19491/j.issn.1001-9278.2019.02.024

Abstract ( 1083 ) PDF (429 KB)( 578 )

This paper reviewed several preparation methods for expanded polytetrafluoroethylene (ePTFE), which included the stretching, pore-forming and spinning methods. The applications of ePTFE in chemical, textile, medical, mechanical and aerospace fields were introduced in detail, and their future direction of research and development was prospected.