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2017, Volume 31 Issue 06 Publication date: 26 June 2017 Previous Issue Next Issue

A Review of Applications and Research Progresses in Flame-retardant Polymeric Nanocomposites

2017, 31 (06): 1-7 ; DOI: 10.19491/j.issn.1001-9278.2017.06.001

Abstract ( 381 )

This paper introduced the applications of nano flame retardants in composites, especially in resinmatrix composites and analyzed the types and characteristics of nano flame retardants with high efficiency, low smoke, low toxicity and good physical properties. The paper also reviewed the current status of layered silicates, carbon nanotubes, polyhedral oligomeric silsesquioxanes and graphene nanosheets at home and abroad. Moreover, the future research directions in this issue were prospected.

Research Status and Hot Spots of Polymer Materials Based on Literature Metrology

2017, 31 (06): 8-15 ; DOI: 10.19491/j.issn.1001-9278.2017.06.002

Abstract ( 409 )

On the basis of the circulation of academic papers in the field of polymer materials which were published in 2011—2015 by representative countries and institutions, references with the top 10 % high citations, and numbers of average citations and total citations, research and development status of polymer materials were investigated by a bibliometric method using the Scopus database and SciVal research evaluation tool. The hot spots of studies were analyzed according to the key words in global academic journals on polymer science and materials. Moreover, this paper also explored situations of international collaborations in China and the competitive advantages in the cross disciplinary researches in fields of polymer science and engineering.

Hygrothermal Aging Behaviors of Poly(hexamethylene terephthalamide)

2017, 31 (06): 16-21 ; DOI: 10.19491/j.issn.1001-9278.2017.06.003

Abstract ( 405 )

A hygrothermal aging experiment was conducted for polyhexamethylene terephthalamide (PA6T) at 20, 90 and 150 ℃, and effect of aging time on physical and mechanical properties of PA6T specimens was investigated. The results indicated that water absorption of PA6T increased with an increase of aging time, and its diffusion coefficient and equilibrium moisture absorption were also improved as the aging temperature increased. There was no change in intrinsic viscosity observed from of PA6T specimens at 20 and 90 ℃. However, the intrinsic viscosity decreased evidently at 150 ℃ because of the hydrolysis of PA6T. The impact strength of PA6T was enhanced due to the increase of activity of its molecular chains. Furthermore, hydrogen bonding between water and amide groups led to an increase in tensile modulus.

Preparation and Properties of Poly (butylene succinate) Hydrophobic Film

2017, 31 (06): 22-27 ; DOI: 10.19491/j.issn.1001-9278.2017.06.004

Abstract ( 443 )

In this work, a type of biodegradable polybutylene succinate (PBS) film with strong hydrophobicity was designed and prepared through a microphaseseparation method by using chloroform as a solvent and anhydrous ethanol as a nonsolvent. The effects of PBS concentration and nonsolvent content on wettability, crystallinity, adhesion and surface morphology of the prepared PBS film were investigated. The results indicated that different surface microstructures were obtained by changing the PBS concentration and nonsolvent content. The water contact angle increased with an increase of nonsolvent content and achieved a maximum value of 142.5 °, which was higher than that of untreated PBS by approximately 60 °. The crystallinity of PBS film exhibited a positive relationship with hydrophobicity, and the higher the degree of crystallinity, the greater the water contact angle of PBS film. The hydrophobic film demonstrated a roselike hydrophobic surface with high adhesion.

Preparation and Properties of Castor-oil-based Polyurethane Modified by Polyether-polysiloxane Polyols

2017, 31 (06): 28-35 ; DOI: 10.19491/j.issn.1001-9278.2017.06.005

Abstract ( 334 )

Plant-oil-based waterborne polyurethanes were synthesized by using polyether-polysiloxane polyols (PEPSO) and castor oil as raw materials. In the synthetic process, different amount of PEPSO was introduced into polyurethane molecular chains through a chemical reaction between NCO groups and OH groups of PEPSO, which resulted in a series of polyurethane emulsions with different contents of PEPSO soft segments. Chemical structures, particle size, thermal stability, mechanical properties and surface hydrophobicity of the prepared polyurethanes were extensively characterized. The results indicated that PEPSO segments were successfully incorporated into polyurethane backbones, and the resultant polyurethanes exhibited an enhanced thermal stability in the presence of PEPSO segment. However, the glass transition temperature and particle size of polyurethanes were reduced with increasing content of PEPSO segment. With the addition of small amount of PEPSO, the tensile strength and hydrophobicity of polyurethanes was improved to some extent.

Study on Stress-oscillation Behavior of Poly(ethylene terephthalate) During Tensile Test

2017, 31 (06): 36-40 ; DOI: 10.19491/j.issn.1001-9278.2017.06.006

Abstract ( 339 )

This paper reported a study on the effect of molecular weight on stressoscillation behavior of poly(ethylene terephthalate) (PET) during the tensile experiment. Tensile test, differential scanning calorimetry and scanning electron microscopy were performed to investigate the stress-oscillation behavior, crystallinity, and macroscopic and microscopic morphologies in different regions of PET specimen. The results indicated that the stress-oscillation behavior of PET specimen was dependent on the relative molecular weight of PET resin and the tensile rate. Inhomogeneous voids observed inside the PET specimen were derived from the stress oscillation and considered as a microscopic result. The occurrence of stress oscillation was due to the difference of crystallinity degree within the bright-dark alternating bands during the process of stretch-induced crystallization.

Preparation and Properties of Reinforced POM/TPU Composites with Potassium Hexatitanate Whiskers

2017, 31 (06): 41-45 ; DOI: 10.19491/j.issn.1001-9278.2017.06.007

Abstract ( 463 )

Reinforced thermoplastic polyurethane elastomer (TPU)/polyoxymethylene (POM) composites with potassium hexatitanate whisker (PTW) were prepared by a melt mixing method. Effect of PTW content on mechanical properties of TPU/POM composites was studied, and impact fracture morphologies of the composites were investigated by scanning electron microscopy. The results indicated that the impact toughness of POM was significantly improved by the addition of TPU. The notch impact strength of the composites increased by a factor of 2.5 times compared with that of pure POM when 10 wt % TPU was incorporated. Nevertheless, the tensile and flexural strength showed a decrease in the presence of TPU. Mechanical properties of the composites at TPU/POM weight ratio of 10/90 could be significantly improved by the introduction of PTW. With the addition of 15 wt % PTW, the composites achieved optimum mechanical properties, in which the tensile strength, tensile modulus, elongation at break, flexural strength, flexural modulus, and notched impact strength reached 35.91 MPa, 248.32 MPa, 24.17 %, 144.94 MPa, 12.26 GPa, and 112.1 kJ/m2, respectively. Compared with those of TPU/POM composite, the tensile modulus, flexural modulus and notched impact strength of the POM/TPU/PTW composite increased by 14.7 %, 54.2 % and 9.2 %, respectively.

Preparation and Properties of High Modulus and High Impact Polypropylene Composites

2017, 31 (06): 46-53 ; DOI: 10.19491/j.issn.1001-9278.2017.06.008

Abstract ( 414 )

This paper reported a study of effects of ethylene-octene copolymer (POE), talc, and high-density polyethylene (PEHD) contents on mechanical properties, crystallization behavior, thermal decomposition behavior, and morphology of polypropylene (PP) composites. Impact toughness of the composites tended to increase with a decrease in the PP/POE viscosity ratio. The optimum mechanical properties were gained for the composites with PP/POE/talc/PE-HD weight ratio of 13/4/12/3. Compared with pure PP, the composites achieved an increase in flexural modulus by 60.1 % and in impact strength by 435.9 %, whereas their tensile strength and flexural strength were reduced by 27.4 % and 17.4 %, respectively. The interface interaction between PP and POE phases was enhanced due to the presence of PE-HD, thus improving the impact toughness of the composites. The introduction of talc or PE-HD into the composites also resulted in an improvement in initial decomposition temperature and the temperature at the maximum weightloss rate and, therefore, enhanced the thermal stability of the composites.

Effect of Epoxy Chain Extender on Rheological Behavior and Mechanical Properties of Poly(lactic acid)

2017, 31 (06): 54-58 ; DOI: 10.19491/j.issn.1001-9278.2017.06.009

Abstract ( 370 )

Ploy(lactic acid) (PLA) was chain-extended by an epoxy chain extender (ADR4370F) through melt extrusion, and then its rheological behavior and mechanical properties were investigated. The rheological evaluation indicated that the storage modulus, loss modulus, complex viscosity, relaxation time, and relaxation modulus of PLA were improved due to the chain extension by ADR4370F. Moreover, the elastic response became faster with the addition of ADR4370F but viscous dissipation became weaker. PLA exhibited a gel-like behavior when 1.0 wt % of ADR4370F was incorporated. Cole-Cole plots exhibited a branched structure formed by chain extension, and meanwhile vGP plots further predicted a star-like topological structure within the chain-extended PLA. The mechanical tests showed that the notched impact strength of PLA were improved with the addition of ADR4370F, and however there was almost little effect on tensile strength. With the addition of 1.0 wt % ADR4370F, the notched impact strength of PLA was improved to 6.0 kJ/m2, presenting an increase by 65.75 % compared with that of pristine PLA.

Study on Interface Modification of Coir-reinforced Poly(butylene succinate) Composites

2017, 31 (06): 59-64 ; DOI: 10.19491/j.issn.1001-9278.2017.06.010

Abstract ( 355 )

Effects of fiber surface treatment and compatibilizers on mechanical properties and interface adhesion of polybutylene succinate (PBS)/coir composites were investigated, and mechanism of interfacial modification was discussed. The results indicated that a proper surface treatment as well as the addition of compatibilizers improved the tensile properties of the composites significantly. Scanning electron microscopic observation confirmed the enhancement of interfacial adhesion between the coir and PBS matrix, which resulted in an improvement in the mechanical properties of the composites.

Preparation and Properties of Polycaprolactone/Silica Nanocomposites

2017, 31 (06): 65-70 ; DOI: 10.19491/j.issn.1001-9278.2017.06.011

Abstract ( 345 )

Polycaprolactone (PCL)-based nanocomposites with different contents of SiO2 nanoparticles were prepared by a melt-blending method, and effects of SiO2 content on morphology, rheological behavior, static and dynamic mechanical properties, and biodegradability of PCL/SiO2 nanocomposites were investigated. The results indicated that the fraction of small particles as the second phase tended to increase gradually with an increase of SiO2 content. However, the second phase particles presented a serious aggregation when the SiO2 content exceeded 3 wt %. As the SiO2 content and temperature increased, the PCL/SiO2 nanocomposites showed a decrease in their linear viscoelastic region. The nanocomposites also exhibited a rheological percolation in the range of 7 wt %~9 wt %. When the SiO2 content varied from 0 to 9 wt %, the tensile strength and Young's modulus of the nanocomposites presented an increasing trend at first and then decreased. The nanocomposites achieved the maximum tensile strength and Young's modulus at the SiO2 contents of 3 wt % and 7 wt %, respectively. The degradation rate of the nanocomposites was improved gradually with increasing the SiO2 content, and the degradation occurred from the specimen surface in a layer-etching mode.

Formation Mechanisms and Solutions of Defects in Microfluidic Chips During UV-curing Injection Molding

2017, 31 (06): 71-78 ; DOI: 10.19491/j.issn.1001-9278.2017.06.012

Abstract ( 335 )

This paper reported a new method for the formation of microfluidic chips through UV-curing microinjection molding. Because UV-curable materials were liquid at room temperature and the curing process is performed by chemical reactions, there were a number of differences between UV-curing microinjection molding and conventional microinjection molding. The results from injectionmolding experiments indicated that the bubbles appearing near the “cross” of micro channel as well as the whole surface of microfluidic chips were considered as a major defect in the forming process. Such a defect showed a negative effect on the use of microfluidic chips. Formation causes of this defect were analyzed through a visible experiment, and effects of injection pressure, vacuum, injection mode and illumination mode on the defect were investigated, and solutions for elimination of the defect were explored. The results indicated that the injection mode and illumination mode determined the formation of bubbles near the “cross” and on the whole surface of microfluidic chips, respectively. The defect could be eliminated completely by adopting suitable injection and illumination modes.

Numerical Study on Uniformity of Surface Temperature of Slide-shaped Moulds in Rotational Molding Process

2017, 31 (06): 79-83 ; DOI: 10.19491/j.issn.1001-9278.2017.06.013

Abstract ( 331 )

Uniformity of surface temperature of slideshaped moulds inside cylindrical ovens for rotational molding was studied theoretically by numerical simulation with the aid of a Fluent software. The energy conservation principle was adopted to obtain the analytical solution of average air temperature inside the oven. By comparing the numerical solution with the analytical one, the theoretical model of heat transfer and method of numerical computation were proved to be correct. The effects of the temperature and velocity of incoming air flow and the circumferential locations of inlets and outlets at the oven on the uniformity of surface temperature of slideshaped mould were also investigated. The results indicated that the uniformity of surface temperature became worse with an increase of the temperature of incoming air flow, and however it could be improved by increasing the speed of incoming air flow. Furthermore, the uniformity of surface temperature could also be improved by making the circumferential locations of inlets and outlets more close to the horizontal boundary lines between the upper and lower half of the cylindrical oven wall.

Study on Numerical Simulation of Mixing Process for Active Pharmaceutical Ingredient During Hot-melt Extrusion

2017, 31 (06): 84-89 ; DOI: 10.19491/j.issn.1001-9278.2017.06.014

Abstract ( 282 )

This paper reported a study on the numerical simulation for the mixing process of acetaminophen as an active pharmaceutical ingredient and poly(ethylene oxide) as a carrier during hot-melt extrusion by a Polyflow software using particle size, mixing index, separation scale and time-average mixing efficiency as characterization parameters. The influences of rotation speed and the gap between discs on the mixing process were investigated. The results indicated that the dispersion mixing and distribution mixing during hot-melt extrusion were enhanced by increasing the rotating speed and decreasing the gap between discs. Meanwhile, the particle sizes of the active pharmaceutical ingredient were obtained as preliminary data for the analysis of its dissolution mechanism.

Analysis of Key Factors for Microstructure Filling During Injection-compression Molding for Thin-wall Products

2017, 31 (06): 90-94 ; DOI: 10.19491/j.issn.1001-9278.2017.06.015

Abstract ( 279 )

Influences of temperature and technical parameters of injection compression molding on microstructure filling effect in three different positions of thin-wall products were investigated by an orthogonal experiment and an injection-compression molding method. The results indicated that the different distances from the sprue gate of microstructure generated different influences on the filling. Compared with the temperature as a factor, technical parameters of compression process played a pivotal role on the microstructure filling. The effects of open distance and compression speed on the filling in the three microstructures were much greater than others in the technical parameters. A smaller open distance value and a larger compression speed value were advantageous to the microstructure filling.

Influence of UV Crosslinking on Properties of Insulation Materials Used for Low-smoke Halogen-free Flame-retardant Cables

2017, 31 (06): 95-99 ; DOI: 10.19491/j.issn.1001-9278.2017.06.016

Abstract ( 312 )

This paper reported an investigation on the effect of ultraviolet (UV) crosslinking on thermal elongation, mechanical properties and flame retardancy of an insulation material used for low-smoke halogen-free flame-retardant cables. The thermal stability and aging behavior of the insulation material were also studied by thermogravimetric analysis. The results showed that the thermal elongation of insulation material decreases gradually with an increase in UV irradiation time, and its mechanical properties, heat resistance, and flame retardant and electrical performance were greatly enhanced due to UV crosslinking. The tensile strength of the insulation material was improved from 10 MPa to 13 MPa after UV crosslinking. With a thermal aging test at 158 ℃, both the tensile strength and elongation at break achieved a retention rate above 90 %, and the limiting oxygen index also increased from 33.5 % to 35.0 %. Moreover, the volume resistivity and dielectric strength were improved to 7.8×1012 Ω·m and 36.0 MV/m from 1.1×1013 Ω·m and 33.0 MV/m before UV crosslinking, respectively

Preparation and Characterizations of a Twin-monomer-grafted Polypropylene Modifier

2017, 31 (06): 100-104 ; DOI: 10.19491/j.issn.1001-9278.2017.06.017

Abstract ( 417 )

A twin-monomer-grafted polypropylene (PP)-based modifier was prepared by using N-vinyl pyrrolidone (NVP) and poly(ethylene glycol methacrylate) (PEGMA) as monomers through a melt grafting method. The resulting graft copolymer was characterized by elemental analysis, Fourier-transform infrared (FTIR) spectroscopy, protein adsorption experiment and contact angle test. FTIR analysis indicated that the two monomers were grafted onto PP successfully. The grafting rate of NVP on PP could be improved by the addition of a small amount of PEGMA, and the graft copolymer achieved a grafting rate of 21.36 wt % for NVP and 3.82 wt % for PEGMA. The graft copolymer exhibited good hydrophilicity, and its water contact angle decreases from 105 ° to 53 °. The graft copolymer also can restrain the adsorption of protein effectively, so the membrane made from this graft copolymer is expected to have a good anti-pollution capability.

Synthesis and Characterizations of Pentaerythritol Phosphate Melamine Salt

2017, 31 (06): 105-110 ; DOI: 10.19491/j.issn.1001-9278.2017.06.018

Abstract ( 712 )

Pentaerythritol phosphate melamine salt (PPMS) as an expansion-type flame retardant was synthesized through a two-step pathway by using pentaerythritol, melamine and phosphoric acid as raw materials, and its chemical structure was characterized by Fourier-transform infrared spectroscopy. The effects of raw material ratio, the time and temperatures for esterification and saltforming reactions on the molecular structure of the product were investigated. The results indicated that the optimum synthetic condition was determined as a molar ratio of pentaerythritol/phosphoric acid/melamine at 1∶3∶1.09, an esterification temperature of 100 ℃, a reaction time of 1.5 h, a salt-forming temperature of 80 ℃, and a salt-forming reaction time of 6 h. The resultant PPMS achieved an expansion degree of 25.5 cm3/g and a char yield of 54.3 % while being synthesized at such an optimum condition.

Experimental Study on Plasticizing Properties of a Single-screw Extruder with Grooved Barrels

2017, 31 (06): 111-117 ; DOI: 10.19491/j.issn.1001-9278.2017.06.019

Abstract ( 356 )

In this article, an experimental platform based on a single-screw extruder with a split barrel was employed to analyze the onset melt temperature, melting duration, temperature and pressure of polymer melt and output of products. The effect of different materials on plasticizing performance of the single-screw extruder was comparatively investigated under different processing conditions. The results indicated that the actual melting duration increased with increasing screw speed or barrel temperature, but it was almost not affected by the onset melt temperature. Moreover, there was no significant change in the temperature and pressure of melting zone in the grooves with an increase of screw speed. However, the output was improved linearly as the screw speed increased. This implicates a good extrusion feature.

Design of Metal Injection Mould for Bases of Orthodontic Appliances

张维合 allenzhang

2017, 31 (06): 118-122 ; DOI: 10.19491/j.issn.1001-9278.2017.06.020

Abstract ( 378 )

This paper reported a design of precision injection moulds for metal injection molds (MIM) for bases of orthodontic appliances. A mixture of stainless steel powders and ABS resin at a weight ratio of 6.5/3.5 was used as the fed material. In this mould, a push rod, a fixed distance parting mechanism with an internal and external combined structure, and a cooling water pipe with a diameter of 10 mm were adopted in the side core-pulling mechanism. The experimental results indicated that such a design provided a good solution for the problems of difficulties in feeding, demoulding and cooling during MIM process.