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2018, Volume 32 Issue 12 Publication date: 26 December 2018 Previous Issue Next Issue

Progress in Applications of Graphene for Anticorrosion Coatings

2018, 32 (12): 1-9; DOI: 10.19491/j.issn.1001-9278.2018.12.001

Abstract ( 607 )

This paper reviewed the most recent advances in the development of graphene and graphene oxide as modifiers for anticorrosion coatings, and the relevant anticorrosion mechanisms were also discussed. Moreover, the modification methods for graphene and graphene oxidewere introduced, which included in-situ modification for grapheme and electrochemical deposition and in-situ reduction methods for graphene oxide. The applications of organic modifier, inorganic modifier and microcapsule technology for modification of graphene oxide were also introduced extensively. Finally, a trend in the future research of graphene-modified anticorrosion coatingswas prospected.

Progress in biodegradation of poly(butylene succinate) and its copolyesters

2018, 32 (12): 10-15,33; DOI: 10.19491/j.issn.1001-9278.2018.12.002

Abstract ( 511 )

This paper overviewed the biodegradation and relevant influence factors of poly(butylene succinate) (PBS) and its copolyesters. The biodegradation behaviors were summarized with respect to microbial degradation, physiological environmental degradation and enzymatic degradation. Finally, the future direction for the research and development of degradation of PBS and its copolyesters was discussed and their applications were prospected.

Study on Foaming Behavior of PS/PTFE Blends

2018, 32 (12): 16-19,55; DOI: 10.19491/j.issn.1001-9278.2018.12.003

Abstract ( 446 )

PS/PTFE nanocomposites were prepared by a melt blending method, and the effects of PTFE content and morphology on the rheological behaviors and foaming behaviors of PS/PTFE blends were investigated. The results indicated that PTFE could be conducted by in-situ fibrillation to improve the rheological behavior of PS/PTFE blends significantly, thus enhancing the foamability of the blends. Meanwhile, PTFE could act as a highly effective nucleation agent to promote the cell nucleation and reduce cell size and reduced the foam density of the blends accor-dingly.

Influence of Distilled Water Content on Properties of Sandwich Polyurethane Foam

2018, 32 (12): 20-25; DOI: 10.19491/j.issn.1001-9278.2018.12.004

Abstract ( 481 )

A new type of sandwich foam composite was prepared by an integrated foaming-molding method using isocyanate and polyester polyol as raw materials and distilled water as a foaming agent. The pore diameter, density, thermal conductivity, thermal properties, and compression and three point bending performance were investigated for the rigid polyurethane foam with water contents of 0, 0.5 wt % and 1.0 wt % by means of thermogravimetric analysis and scanning electron microscopy. The optimum parameters were then achieved. The results indicated that the pore diameter and thermal insulation performance of rigid polyurethane foams increased with an increase of water content, but their foam density and thermal conductivity decreased. However, the compression and three-point bending performance of the foams exhibited a decline trend. Therefore, to achieve the reasonable cell structure and good mechanical properties for the foams, the optimum moisture content should be determined as 0.5 wt %.

Effect of Methyl Methacrylate-silicone-styrene Copolymer on Morphology and Stress Relaxation of PLA/PBAT Blends

2018, 32 (12): 26-33; DOI: 10.19491/j.issn.1001-9278.2018.12.005

Abstract ( 502 )

PLA/PBAT/methyl methacrylate-silicone-styrene copolymer (S-2001) blends were prepared by melt extrusion with a twin-screw extruder, and the effect of S-2001 content on the microstructure, rheological behavior and mechanical properties of the blends were investigated by using a scanning electron microscope, rotational rheometer and electronic universal testing machine. The results indicated that the addition of S-2001 reduced the size of dispersed particles but improved the interfacial adhesion between the PLA and PBAT phases. Furthermore, the storage modulus, loss modulus and complex viscosity of the blends were also improved, and their Marangoni stress relaxation was enhanced gradually. When the 9 phr of S-2001 was incorporated into the blends, the notched impact strength increased by 596.6 % from 5.8 kJ/m2 to 40.4 kJ/m2, suggesting that S-2001 acts as an impact modifier as well as a compatibilizing agent.

Study on Toughening and Compatibilizing Effect of SEBS Elastomer on PE-HD/PS Blends

2018, 32 (12): 34-40,68; DOI: 10.19491/j.issn.1001-9278.2018.12.006

Abstract ( 1684 )

The high-density polyethylene (PE-HD)/polystyrene (PS) blends were prepared by a HAAKE torque rheometer using poly(styrene-b-ethylene-butylene-b-styrene) (SEBS) elastomer as an impact modifier, and the compatibilizing effect of SEBS on this blending system was investigated by a scanning electron microscope, rotary rheometer, impact tester, thermogravimetric analyzer and differential scanning calorimeter. The results confirmed an effective compatibilizing effect of SEBS on the blending system. However, the aggregation was observed when the SEBS content was higher than 8 wt %, which led to a decrease in compatibility of the blending system. There is also no influence on the heat resistance of the blends from SEBS, whereas the melting point of PE-HD phase decreased slightly due to the introduction of SEBS. The notched Izod impact strength was improved significantly with an increase of SEBS content.

Preparation of Polystyrene/Highly Dispersed Graphene Composites by Non-covalent Modification

2018, 32 (12): 41-48; DOI: 10.19491/j.issn.1001-9278.2018.12.007

Abstract ( 610 )

The highlydispersed polystyrene/graphene composites were prepared by ultrasonic dispersion and suspension polymerization using styrene and industrial graphene (IGN) as raw materials, polyvinyl alcohol and tricalcium phosphate as dispersing agents, benzoyl peroxide as an initiator and polystyrene resin (PS) as a non-covalent modifier. The effects of ultrasonic dispersion time and PS content on the dispersion of IGN in the matrix were investigated. The experimental results indicated that the addition of PS could effectively improve the compatibility of IGN with styrene monomer. IGN achieved an optimum dispersion in the matrix when ultrasonic time was set as 30 min and PS content was set to 3 % in the monomer. With an increase of weight ratioof IGN/PS, the initial degrading temperature of the composites increased by 40 ℃, the glass transition temperature increase by 7.3 ℃maximally, and tensile strength increased by approximately 65 % from 43.5 MPa to 68.3 MPa.

Flame retardancy and high performance of polycarbonate/acrylonitrile-butadiene-styrene/hexaphenoxycyclotriphosphazene

2018, 32 (12): 49-55; DOI: 10.19491/j.issn.1001-9278.2018.12.008

Abstract ( 572 )

The flame-retardantcompounds based on polycarbonate (PC)/acrylonitrile-butadiene-styrene copolymer (ABS) alloys and hexaphenoxycyclotriphosphazene (HPCTP) were prepared by a melt extrusion method, and the effects of polyethylene grafted maleic anhydride (PE-g-MAH) and HPCTP on the thermal stability, flame-retardant performance and mechanical properties of PC/ABS alloys were investigated by thermogravimetric analysis, limited oxygen index (LOI), vertical burning experiment, cone calorimeter test, electronic universal testing machine and impact testing machine. Furthermore, the morphology of residual char was analyzed by scanning electron microscopy after combustion of PC/ABS alloys, and the relevant flame-retardant mechanisms were discussed. The results indicated that the flame retardant PC/ABS alloys achieved the optimum comprehensive properties by using PE-g-MAH as a compatibilizer when the mass ratio of PC/ABS was set to 7/3 and the content of HPCTP set as 15 wt %. In this case, the PC/ABS alloy obtained an LOI of 26.4 vol %. Furthermore, the PC/ABS alloys achieved the minimum values in heat release rate and total heat release as well as a V-0 classification in the vertical burning experiment. The alloys also gained the tensile strength of 55 MPa and the notched impact strength of 32.9 kJ/m2.

Chemical and Physical Properties of Heat-compression Film Materials for Medical Applications

2018, 32 (12): 56-60,117; DOI: 10.19491/j.issn.1001-9278.2018.12.009

Abstract ( 673 )

This paper investigated the physical and chemical performances of four main invisible align thermoplastic materials, including BiolonTM, ErkodurTM, ScheuTM and DR ProformTM. The mechanical and thermal properties of these four materials were analyzed by mechanical measurements and differential scanning calorimetry, while their chemical compositions and optical properties were characterized by FTIR spectroscopy and ultraviolet- visible spectrophotometry. The results indicated that the thicker materials exhibited a higher elasticity modulus and tensile strength when the material thickness was lower than 1.0 mm. Furthermore, the stresses of four materials relaxed with time under a 5 % displacement, and the Scheus stress relaxation ratio showed a lowest value. FTIR analysis confirmed that these four materials were composed of a novel copolyester based on PETG. DSC analysis identified that the four materials were amorphous polymers with a glass transition platform. The four materials exhibited the light transmittance above 80 % within a visible spectrum of 400~760 nm, indicating that these materials had excellent transparent performance for invisible orthodontics.

Synthesis and Properties of Waterborne Epoxy Resin Modified with P2O5

2018, 32 (12): 61-68; DOI: 10.19491/j.issn.1001-9278.2018.12.010

Abstract ( 686 )

In order to obtain waterborne epoxy resin with a high surface activity, the epoxy resin was modified by phosphorus pentoxide as a phosphorylation reagent, and the phosphorylation process was optimized. The effect of reaction conditions on the epoxy value, monoester content and diester content of resultant product was investigated with respect to the main influence factors such as reaction feed ratio, reaction time and temperature. The optimum reaction conditions were determined as an E20/P2O5 molar ratio of 1.2/1, a reaction temperature of 85 ℃ and reaction time of 3 h. The synthesized product achieved an epoxy value of 0.057 mol/100 g, a monoester content of 0.44 wt % and a diester content of 0.56 wt % under these conditions. The chemical structure of modified epoxy resin was characterized by Fourier-transform infrared spectroscopy and NMR spectrometer, and their thermal stability, viscosity-temperature, viscosity-concentration, particle size and surface activity were also investigated. The results indicated that there was partial breakage of epoxy bonds occurring in the molecular structure of the modified epoxy resin, followed by an appearance of monoester and diester functional groups of phosphoric acid. These results suggested that this new modified epoxy resin was synthesized successfully, and it exhibited a good thermal stability and a small average particle size in emulsion is smaller. When the mass fraction of emulsion was lower than 10 wt %, the epoxy resin showed a high surface activity and its viscosity was almost not influenced by the mass fraction. Moreover, the emulsion presented a minimum surface tension at a mass fraction of 0.5 wt %.

Study on Preparation and Properties of PA6/TiO₂-GO Composites

2018, 32 (12): 69-74; DOI: 10.19491/j.issn.1001-9278.2018.12.011

Abstract ( 517 )

In recent years, the problem of environmental pollution have become more and more serious. Photocatalytic technology plays an important role in treating sewage and purifying air. In this paper, the effect of different nano-TiO2 dosage on the thermal properties, mechanical properties, photocatalytic properties of PA6/TiO2-GO composite were studied by the differential scanning calorimeter, electronic universal tensile testing machine, visible spectrophotometer and other instruments. The results of the study show that: with the increase of nano-TiO2 content, the melting point of PA6/TiO2-GO composites gradually decreases, the crystallinity increases first and then decreases (the crystallinity of composites is greater than that of pure PA6). The breaking strength gradually decreases. The elongation at break gradually increases. The ability of nano-TiO2 to photocatalytic degradation of methylene blue solution becomes stronger and stronger. At the same TiO2 content, adding GO can effectively improve the photocatalytic degradation of TiO2, and the photocatalytic degradation capability can be improved by about 10%.

Preparation of polylactide/aluminum phenylphosphinate composites and its flame retardancy

2018, 32 (12): 75-79; DOI: 10.19491/j.issn.1001-9278.2018.12.012

Abstract ( 537 )

Aluminum phenylphosphinate (AlP) was synthesized by a co-precipitation method. A series of PLA/AlP composites were then prepared by melt blending, and the effect of AlP content on the thermal stability, flame retardant performance and combustion properties of the composites were investigated by thermogravimetric analysis, limiting oxygen index (LOI), vertical burning experiments and microscale combustion calorimeter (MCC). The results indicated that the incorporation of AlP enhanced the flame retardancy of PLA-matrix composites effectively, and the composites achieved a UL 94 V-0 classification as well as an LOI of 25.6 vol %. Thermal analysis showed that AlP improved the degradation temperature and residual char of the composites. MCC measurements demonstrated that the peak of heat release rate and the total heat release presented an increase at first and then decreased with an increase of AlP content.

Research on flexible substrate microneedle process parameters for micro-injection compression molding

2018, 32 (12): 80-85; DOI: 10.19491/j.issn.1001-9278.2018.12.013

Abstract ( 398 )

According to the requirement for the application of micro-injection compression molding technology in the field of thin-walled microscale plastic parts with flexible substrates, this paper reported a study on the preparation and process technology of microneedle arrays with a flexible substrate through micro-injection compression molding. On the basis of the design of laminated microneedle pyramid mold, polypropylene (PP) was used as an experimental material to explore the effect of process parameters on the molding quality of microneedle arrays. The experimental results indicated that the optimal height for microneedles was 329 μm. The injection speed, melt temperature and secondary clamping pressure were found to have a significant influence on the height of microneedles through a range analysis. A molecular orientation stress model was used to explain the trend of the curve from a microscopic viewpoint. The analysis of variance indicated that the injection rate of molding was taken as the greatest contribution rate, reaching 25.3 %.

Study on Rheological Behaviors of PE-LD Resins Used for Greenhouse

2018, 32 (12): 86-90,125; DOI: 10.19491/j.issn.1001-9278.2018.12.014

Abstract ( 417 )

The shear and extensional rheological properties of several types of PE-LD resins specially used for greenhouse were investigated intensively by using torque rheometer, capillary rheometer, melt extension rheometer and rotating rheometer. The results indicated that 2100-type and 1810D-type resins had a higher branching degree, lower processing load, higher shear sensitivity and better processability then the others. As for the 2100-type resin, its higher melt strength and more obvious strain hardening effect favored the stability of film bubble. The dynamic rheological experimental results showed that the molecular chain with long relaxation time gave melt strength and strain hardening, and the wide distribution relaxation spectrum provided good processing performance. Summarily, the 2100-type and 1810D-type resins exhibited optimum comprehensive performance among the selected resins.

Study on Preparation and Morphology of Poly(vinyl alcohol) Electrospun Nanofibers

2018, 32 (12): 91-96; DOI: 10.19491/j.issn.1001-9278.2018.12.015

Abstract ( 783 )

Poly(vinyl alcohol) (PVA) nanofibers were prepared by an electrospinning technology, and their process parameters such as spinning voltage, spinning distance and spinning solution concentration were adjusted by an orthogonal experiment. The effect of these process parameters on the diameter and its distribution and morphology of PVA nanofibers was also investigated. The results indicated that the main influence factors for fiber morphology followed an order of spinning solution concentration>spinning distance>spinning voltage. An optimum combination of process parameters was determined as a spinning voltage of 20 kV, a spinning solution concentration of 6 wt % and a spinning distance of 12 cm.

Study on Fabrication and Performance of TPU Composite Films

2018, 32 (12): 97-105,137; DOI: 10.19491/j.issn.1001-9278.2018.12.016

Abstract ( 507 )

A novel method was adopted to modify TPU with the nanohybrids consisting of two-dimensional graphene oxide nanoribbons (GONRs) and one-dimensional carbon nanotubes (CNTs). The GONRs-CNTs nanohybrids were obtained with a weight fraction of GONRs of 67 wt % through oxidative longitudinal unzipping for MWCNTs, followed by a modification with phenyl isocyanate. The functionalized GONRs-CNTs (pGONRs-CNTs)/TPU composite films were then prepared by a solution coating method using a coating machine. The effect of pGONRs-CNTs content on the barrier, tensile and degradation properties of the composite films was investigated. The results indicated that pGONRs-CNTs were well dispersed in the TPU matrix with a neat shape and low defect due to its strong interfacial adhesion with TPU. When 0.5 wt % of pGONRs-CNTs was incorporated into TPU, the composite films achieved the optimium barrier and tensile properties, in which the oxygen transmission rate decreased by 63.08 % and the tensile strength increased by 46.55 % compared to those of pure TPU film. In addition, the addition of pGONRs-CNTs also improved the serving time of the composite films.

Study on Thermal Degradation and Thermal Life of PP/MWCNTs Composites

2018, 32 (12): 106-111; DOI: 10.19491/j.issn.1001-9278.2018.12.017

Abstract ( 545 )

The thermal degradation behaviors of polypropylene (PP)/multi-walled carbon nanotubes (MWCNTs) composites were investigated by a thermogravimetric (TGA) method, and their thermal degradation mechanisms were studied by the Achars and Coats-Redferns methods. The Kissingers method was also used to obtain the related kinetic parameters and thermal life equation. The results indicated that there was a weightless stage in the TGA thermograms of the composites. Furthermore, the initial weight-loss temperature and maximum weight-loss temperature exhibited a maximum value at 1.5 wt % of MWCNTs, indicating an improvement in thermal stability of PP. The thermal degradation mechanism was ascribed to a one-dimensional diffusion reaction. The thermal life of the composites was also improved significantly due to the incorporation of MWCNTs. The composites showed an increasing trend in thermal life with an increase of MWCNTs content and achieved a maximum thermal life at the MWCNTs content of 1.5 wt %. The Kissinger methods was considered as a good solution to estimate the thermal life of materials.

Ammonium Polyphosphate/Organic Montmorillonite Compounds Flame-retardant Epoxy Resin

2018, 32 (12): 112-117; DOI: 10.19491/j.issn.1001-9278.2018.12.018

Abstract ( 552 )

An epoxy resin was modified with an intumescent flame-retardant system (IFR) based on poly(2-10-hydrogen-9-oxa-phosphaphenanthrenehydroquinone phenyl phosphate) (POPP) and ammonium polyphosphate (APP) at a weight ratio of 1/2,and then cured with m-phenylenediamine to form flame-retardant thermosets (FR-EP). Organic montmorillonite (OMMT) was incorporated into this IFR to obtain a synergistic flame-retardant and smoke-inhibiting effect at an OMMT content of 1.0 wt %. The combining effect of IFR and OMMT on epoxy resin was investigated by means of limiting oxygen index (LOI), vertical burning experiment, thermogravimetric analysis, cone calorimetry and scanning electron microscopy. The results indicated that the POPP/APP/OMMT-modified epoxy thermosets achieved a V-0 classification in the UL 94 vertical burning experiment as well as an LOI of 25.2 vol %. The initial decomposition temperature of the modified epoxy thermosets decreased slightly, but the residual char increased significantly. According to the cone test results, the heat release rate, total heat release and total smoke release all decreased dramatically. Moreover, the combination of POPP, APP and OMMT promoted the formation of a homogeneous and compact char layer on the epoxy thermoset during combustion. In addition, the OMMT was found to enhance the mechanical properties of the epoxy thermosets.

Effect of Citrate-based Mixed Solvents on PVDF Membrane by Supercritical CO₂-induced Phase Separation

2018, 32 (12): 118-125; DOI: 10.19491/j.issn.1001-9278.2018.12.019

Abstract ( 439 )

Acetylene tributyl citrate (ATBC) and triethyl citrate (TEC) were taken as ecologically friendly hydrophobic diluents to partially replace dimethyl formamide (DMF) and then used as a mixed solvent to fabricate poly(vinylidene fluoride) (PVDF) membrane through supercritical CO2-induced phase separation.The morphologies and structures of the prepared PVDF membranes were influenced significantly with the addition of ATBC or TEC.The membrane surface and cross section were found to become much rougher especially when the amount of ATBC or TEC was increased to 50 wt %.Such a phenomenon is quite different from the membrane prepared with pure DMF.Contact angel measurement proved that the hydrophobicity of the membrane was associated with the surface roughness.The thermodynamic properties of the membrane were not affected by the amounts of ATBC or TEC used for preparation.However, there was a crystal transformoccurred when the amount of ATBC or TEC reached 50 wt %, which resulted in the formation of more β-form crystals.

Detection and Risk Analysis of 18 PAHs in Children's Toys and Supplies

2018, 32 (12): 126-131; DOI: 10.19491/j.issn.1001-9278.2018.12.020

Abstract ( 669 )

This paper reported the detection and risk analysis of 18 types of polycyclic aromatic hydrocarbons (PAHs) in childrens toys and products, which were extracted by a self-established accelerating solvent extraction method. All of the specimens were purified by a solid phase extraction column based on silica gel, and an internal standard method was adopted to determine the concentration of PAHs in childrens toys and products using gas chromatography coupled with triple quadrupole mass spectrometry. The content of PAHs was measured from the samples collected in the circulation market in Suzhou, Jiangsu Province, and a risk analysis was performance according to the test results.

Evolution of Fluid-Projectile-Assisted Injection Molding Technology

2018, 32 (12): 132-137; DOI: 10.19491/j.issn.1001-9278.2018.12.021

Abstract ( 489 )

There have many limitations in the traditional fluid-projectile-assisted injection molding (FPAIM) process. Therefore, the evolution of the FPAIM technology was discussed in detail. The FPAIM molding for the pipes with ends openings, closed voids and branches were realized by adopting proper means. The pipes with variable cross-section, the efficient molding and the removal of projectile were achieved by selecting a proper projectile shape, projectile material and projectile formation method, the stable penetration of projectile. A stable penetration of projectile could be obtained by the modification of the mold, resulting in a uniform wall thickness. The application of FPAIM process and the functions of FPAIM parts could be expanded when this technology was used for the formation of elastic hollow pieces in combination with other processes.

Design of In-mold Decorated Injection Mold for Mobile Phone Protective Case

2018, 32 (12): 138-142; DOI: 10.19491/j.issn.1001-9278.2018.12.022

Abstract ( 516 )

Aiming at the defects of mobile phone protective case under the traditional production methods and taking a mobile phone case as an example, an in-mold decorated mold for the mobile phone protective case was designed according to the requirements of in-mold decoration injection molding process. To facilitate the continuous production and protection of injection-molded products, a flip-chip mold structure was adopted, and a side core pulling mechanism was designed by using slanting rejecting and block mechanisms. The appearance surface was protected by adopting a latent thimble for glue injection, and a pressure bar mechanism was designed to fix the position of pattern film more accurately.