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2017, Volume 31 Issue 12 Publication date: 26 December 2017 Previous Issue Next Issue

Research Progress in Element Hybrid Flame-retardant Polypropylene

2017, 31 (12): 1-8; DOI: 10.19491/j.issn.1001-9278.2017.12.001

Abstract ( 560 )

This paper briefly introduced elemental hybridization technologies for flame-retardant polypropylene (PP) and also discussed its combustion mechanism including heat, decomposition and ignition of PP and flame-retarding methods containing gas phase, condensed phase and interrupting heat exchange. Research progresses in elemental flame-retardant mechanisms, synergistic flame-retardant PP and bio-based flame retardants were overviewed. The paper also summarized problems in current researches of flame-retardant PP and proposed its direction of future development.

Research Progress in Modification of Polymeric Materials by Electron Beam Radiation

2017, 31 (12): 9-14; DOI: 10.19491/j.issn.1001-9278.2017.12.002

Abstract ( 817 )

This paper overviewed the development of electron beam irradiation and its application for radiation-resistant modification of polymeric materials, and its limitation in utilization for bulk irradiation resistant polymer materials was emphasized. This paper also introduced research results in incorporation of large electron cloud, hindered phenolic antioxidants, and effect of hindered amine light stabilizers on irradiation properties of polymeric materials as well as the use and effectiveness of other radiationresistant modifiers. It was concluded that the addition of hindered phenolic antioxidants and hindered amine light stabilizers could enhance the radiation resistance of polymeric materials to some extent, and combination of different stabilizers could achieve a much better radiation-resistant effect on polymeric materials. In this case, the development of highly efficient stabilizers will be an urgent issue for the preparation of radiation-resistant polymers.

Patent Situation Analysis of Transparent Polyimide Films

2017, 31 (12): 15-20; DOI: 10.19491/j.issn.1001-9278.2017.12.003

Abstract ( 491 )

This paper reported a statistical analysis of patent situation in the research and development of transparent polyimide films on the basis of multi-aspects, which includes numbers and development trends of patent applications, the level of technological focus, and the route for technology development. Marketing situation of transparent polyimide film industry in China and Japan was also analyzed.

Modification of Poly(propylene carbonate) by Halloysite Nanotubes

2017, 31 (12): 21-27; DOI: 10.19491/j.issn.1001-9278.2017.12.004

Abstract ( 451 )

To enhance the compatibility between halloysite nanotubes(HNTs) and poly(propylene carbonate)(PPC), HNTs were surface-modified by a silane coupling agent(KH-560). PPC/HNTs nanocomposites were prepared by melt blending and then characterized by Fourier-transform infrared spectroscopy, rheometer and thermogravimetric analysis. The results indicated that KH-560 was successfully grafted onto HNTs with a grafting rate of 26 wt %. HNTs achieved good dispersion in the PPC matrix due to the surface modification. The thermal degradation of PPC was suppressed in the presence of of surface-modified HNTs, indicating that its thermal stability was enhanced by HNTs. Moreover, the tensile strength of PPC was also significantly improved with the addition of surface-modified HNTs.

Preparation and Properties of Self-emulsifying Nonionic Epoxy Resin

2017, 31 (12): 28-33; DOI: 10.19491/j.issn.1001-9278.2017.12.005

Abstract ( 531 )

Poly(ethylene glycol)(PEG)-modified epoxy resin(PEGE) was synthesized through an addition reaction, and the effect of synthetic parameters on epoxy value of PEGE was evaluated. Chemical structure of PEGE was characterized by Fourier-transform infrared spectroscopy and NMR spectroscopy, and its thermal stability, water solubility, particle size and surface tension were investigated. The results indicated that, for the synthesis of PEGE, the optimum mole ratio of PEG/epoxy resin was set as 1.6/1, the optimum reaction temperature was set to 120 ℃, the optimum reaction time was set as 2 h, and the amount of primary amine catalyst was set as 0.5 wt %. The PEGE exhibits a good application prospect due to its high thermal stability, good water solubility, high surface activity, small particle size and homogeneous distribution.

Structure and Properties of a New Highly Branched Metallocene Polyethylene

2017, 31 (12): 34-38; DOI: 10.19491/j.issn.1001-9278.2017.12.006

Abstract ( 470 )

The branching composition distribution and melting-crystallization properties of very-low-density polyethylene PE-VLD with different chain lengths were investigated by means of 13C-NMR spectroscopy and differential scanning calorimetry. The polymerization characteristics of these PE-VLD samples were analyzed on the basis of mean sequence lengths, relative monomer distribution and monomer reactivity ratios, and their crystallization characteristics including lamellar thickness, relative branching degree and crystallinity degree were investigated by SSA thermal classification method. The results indicated that, in the case of PE-VLD with a density of 0.912 g/cm3 and a melt flow rate of 1.0 g/10 min, the sample synthesized by using a butylethylene comonomer exhibited a lower content of copolymerized segment and a lower branching degree than that using a butylene comonomer. However, it had higher crystallinity degree and thicker crystalline lamellas.

Properties and Thermal Decomposition Kinetics of Poly（propylene carbonate） and Poly（lactic acid） Blends

2017, 31 (12): 39-45; DOI: 10.19491/j.issn.1001-9278.2017.12.007

Abstract ( 582 )

Blends of poly(propylene carbonate)(PPC) and poly(lactic acid)(PLA) were prepared by a solution-casting method, and their properties were investigated by mechanical property test, Fourier-transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis and thermal degradation kinetics. The kinetic data were also analyzed by CoatsRedfern method. Tensile testing results indicated that the tensile strength of PPC was improved with the addition of PLA, whereas its elongation at break decreased. TGA results indicated that the thermal stability of PPC could be enhanced by addition of PLA. The characteristic temperature of PPC corresponding to 10 % weight loss was improved from 255 ℃ to 281 ℃ in the presence of PLA at a mass fraction from 10 wt % to 90 wt %, and its characteristic temperature corresponding to the maximum weight loss rate increased by 3.45, 15.51 and 41.58 ℃ at the PPC/PLA mass ratios of 90/10, 50/50 and 10/90, respectively. Coats-Redfern analysis indicated that the activation energy of PPC was improved by 12.72 % and 40.68 % when 12.72 wt % and 40.68 wt % of PLA were incorporated, respectively. This implicates an improvement in thermal stability of PPC by PLA.

Study on Flame Retardant Polystyrene Foamed by Supercritical Carbon Dioxide

2017, 31 (12): 46-50; DOI: 10.19491/j.issn.1001-9278.2017.12.008

Abstract ( 547 )

Polystyrene(PS) was modified with hexabromocyclododecane(HBCD) as a flame retardant and then was foamed by using supercritical CO2 as a foaming agent and hydrotalcite(HT) as a thermal stabilizer. The flame-retardant mechanism and foaming behavior of flame-retardant PS were studied. The results indicated that the thermal stability of HBCD could be improved by adding a proper amount of HT. However, the excessive amount of HT reduced the flame retardancy of PS. The thermal stability of HBCD was significantly influenced by the processing technologies and especially by shear flow field and processing temperature. The flame-retardant PS achieved a limiting oxygen index above 30 vol % through foaming with supercritical carbon dioxide.

Effect of Modified Sisal Fiber’s Content on Properties of Polypropylene

2017, 31 (12): 51-55; DOI: 10.19491/j.issn.1001-9278.2017.12.009

Abstract ( 433 )

Polypropylene(PP)/sisal fiber(SF) composites were prepared by using maleic anhydride-grafted polypropylene(PP-g-MAH) as an interfacial modifier, and the effect of fiber content on the flowability, combustion performance, and thermal and mechanical properties of the composites were investigated. The results indicated that the melt flow rates of the composites were reduced by 3.1 g/10 min with the addition of 30 wt % SF, but their Vicat softening points increased by 5.1 ℃, compared with pure PP. Moreover, their tensile strength and bending strength increased by 6.0 MPa and 20.7 MPa, respectively. In addition, there is a decrease in impact strength by 3.1 kJ/m2 for notched specimens and by 60 kJ/m2 for the unnotched ones.

Preparation and Properties of Silane-crosslinked Halogen-free Flame-retardant Polyethylene-octene Elastomer

2017, 31 (12): 56-61; DOI: 10.19491/j.issn.1001-9278.2017.12.010

Abstract ( 585 )

Silane-crosslinked halogen-free flame-retardant poly(ethylene-octene) elastomer(POE) compounds were prepared through a two-step melt-compounding method using Mg(OH)2 and Al(OH)3 as flame retardants, and its grafting rate was investigated in terms of different silanes and initiators. Mechanical properties, hot elongation performance, thermal decomposition behaviors and flame-retardant properties of the compounds were investigated by using a universal testing machine, a hot elongation tester, a thermogravimeter and a limiting oxygen index instrument. The results indicated that the silane-crosslinked POE initiated by dicumyl peroxide achieved a higher cross-linking degree than that by benzoyl peroxide. The crosslinking feasibility of POE with silane-crosslinking agents is in the order of vinyl trimethoxysilane>vinyl triethoxysilane>γ-methacryloxypropyltrimethoxysilane. The silane-crosslinked flame-retardant POE achieved a higher limiting oxygen index and better mechanical properties than uncrosslinked ones. Moreover, POE/Mg(OH)2 compound obtained a higher char yield than POE/Al(OH)3 ones. The silane-crosslinked flame-retardant POE also presented more residual mass than uncrosslinked ones.

Crystallization Behavior of Compatibilized Polylactide/Polycaprolactone Blends

2017, 31 (12): 62-65; DOI: 10.19491/j.issn.1001-9278.2017.12.011

Abstract ( 695 )

Polylactide(PLA)/polycaprolactone(PCL) blends were prepared by using lactide-caprolactone copolymer(LACL) through a solution-blending method. Morphologies and crystallization behavior of the resulting blends were characterized by scanning electron microscopy and differential scanning calorimetry. The results indicated the dispersed phase exhibited a dramatic decrease in size with the addition of 5 % LACL. The crystalline capability of PLA molecules was greatly enhanced by PCL, thus resulting in a decrease in crystallization temperature. The crystallization temperature of PLA domain in PLA/PCL/LACL ternary blends was further reduced due to compatibilizing effect of LACL. The crystallization activation energies of PLA domain presented a decrease due to the presence of PCL and LACL on the basis of the calculation results derived from Kissinger’s model.

Study on Modification of Poly(propylene carbonate) with Amino-terminated Hyperbranched Polymer

2017, 31 (12): 66-72; DOI: 10.19491/j.issn.1001-9278.2017.12.012

Abstract ( 519 )

Hyperbranched ethylene-diamine triazine polymer(HBP) was first prepared through a one-step synthetic method by using ethylenediamine and cyanuric chloride as raw materials, and then poly(propylene carbonate)(PPC) was modified with HBP through a melt blending method. The resulting compounds were characterized by differential scanning calorimetry, thermogravimetric analysis, tensile and impact measurements, rotational rheological test and scanning electronic microscopy. The results indicated that the modified PPC achieved an improvement in tensile strength by 50 % and in elongation at break by 55.4 % when 1.5 wt % of HBP was incorporated. The glass transition temperature and decomposition temperature of the modified PPC also increased in the precence of HBP. HBP was considered as an effective modifier for PPC.

Effect of Thermoplastic Poly(vinyl alcohol) on Structure and Properties of Poly(lactic acid)

2017, 31 (12): 73-77; DOI: 10.19491/j.issn.1001-9278.2017.12.013

Abstract ( 801 )

Poly(lactic acid)(PLA)/poly(vinyl alcohol)(PVA) blends were prepared by a melt blending method, and their structure and properties were investigated by tensile and impact tests, scanning electron microscopy and scanning electron microscopy. The results indicated that the blends achieved an optimum comprehensive properties when 2 wt % of PVA as an impact modifier was introduced. The impact strength, tensile strength, elongation at break, glass transition temperature and melting temperature of the blends reached 15.6 kJ/m2, 52.7 MPa, 4.2 %, 62.8 ℃ and 167.9 ℃, respectively.

Relationship between Cooling Rate and Relaxation Rate of PMMA During Micro Hot Embossing Process in Solid-like State

2017, 31 (12): 78-83; DOI: 10.19491/j.issn.1001-9278.2017.12.014

Abstract ( 521 )

This paper reported an investigation on the relationship between cooling rate and relaxation rate of poly(methyl methacrylate)(PMMA) during the micro hot embossing process in a solid-like state. A relaxation-rate-temperature index model was established on the basis of the experimental data of stress relaxation of PMMA at different temperature, and then the relaxation rate and relaxation time constants of PMMA at different temperatures were calculated. A relaxation stress ratecooling rate equation was determined for PMMA in an integral form, which could continuously obtain the relaxation stress rate at different cooling rates. A prism microstructural hot embossing experiment was conduced to verify the practicality of stress rate-cooling rate model through the comparison of the theoretical and experimental results. The results indicated that the relaxation stress rate became smaller with an increase of cooling rate, and the internal stress gained a more sufficient relaxation. This led to a higher molding accuracy for the microstructure.

Preparation of Poly(propylene carbonate)/Polytetrafluoroethylene Blends and Their Foaming Behaviors through Supercritical CO₂

2017, 31 (12): 84-89; DOI: 10.19491/j.issn.1001-9278.2017.12.015

Abstract ( 545 )

Poly(propylene carbonate)(PPC)/polytetrafluoroethylene(PTFE) blends were prepared by using an asymmetrical co-rotating twin-screw extruder. Dispersion of PTFE in the PPC matrix was analyzed. Then, the PPC/PTFE blending foams were prepared by using supercritical CO2 as a forming agent, and their foaming behaviors were studied. The results indicated that the dispersion of PTFE was improved significantly due to the utilization of such a new type of twin-screw extruders. PTFE could also act as a nucleating agent to reduce the cell size and increase the cell density remarkably when the blending foams were prepared. The blending foams containing 3 wt % PTFE achieved a minimum cell size of 2 μm and a maximum cell density of 4.75×107 cells/cm3.

Study on Tensile Properties of Glass Fiber-reinforced Polymer Bars Under Low-temperature Environment

2017, 31 (12): 90-93; DOI: 10.19491/j.issn.1001-9278.2017.12.016

Abstract ( 465 )

A tensile experiment was conducted at different temperatures for glass fiberreinforced polymer(GFRP) bars using glass fibers with diameters of 16 mm and 22 mm. The effects of environmental temperature, fiber diameter and constant temperature time on tensile properties of GFRP bars were investigated. The results indicated that the GFRP bars did not show a significant change in apparent failure characteristics under the lowtemperature environment, and their ultimate tensile strength increased with a decrease of temperature in the range of -20~0 ℃. Furthermore, the modulus of GFRP bars containing fibers with a diameter of 16 mm was reduced with a decrease of temperature, whereas that with a diameter of 22 mm maintained a stable value. However, these two types of GFRP bars presented little change in the temperature of 0~20 ℃. The mechanical properties of GFRP bars tended to be stable after being kept in a low temperature for 1 h. The constant temperature time almost showed no effect on the bars.

Study on Selfassembly Behavior of SIS in N-hexane Solution by Elastic Light Scattering Method

2017, 31 (12): 94-100; DOI: 10.19491/j.issn.1001-9278.2017.12.017

Abstract ( 450 )

This paper reported an investigation on the self-assembly behavior of styrene-isoprene-styrene triblock copolymer(SIS) in an n-hexane solvent by an elastic light scattering method. The results indicated that the peak light scattering intensity showed a concave trend with a variation of temperature, and the effective grain diameter increased from 30.1 nm to 943.4 nm with a decrease of temperature. The molecular chains of SIS presented different aggregation states in the solution at different temperature. The light scattering signal was related to the aggregation of SIS and therefore can be used to analyze the phase separation mechanism of SIS. This article provides a new method for the study of phase separation mechanism of block polymers.

Study of Pressure Characteristics of Pre-plastic Back Pressure Valves Based on AMESim

2017, 31 (12): 101-106; DOI: 10.19491/j.issn.1001-9278.2017.12.018

Abstract ( 466 )

This paper studied the back-pressure loops in the hydraulic system of an injection molding machine, and several models were established by an AMESim software through changing the damping hole and the damping ratio of relief valves. The back pressures of the pilot valve and main valve were analyzed under different conditions, which included spring stiffness, damping holes and its sizes. The simulation results indicated that a proper reduction in spring rate for the pilot valve could reduce the rise of pressure in the preplastic back pressure system. When the diameter of the damping orifice was reduced from 2 mm to 0.5 mm, the pressures of the upper and lower chambers in the pre-plastic back pressure valve varied within 0.02 MPa. The rise of pressure no longer took place. The damping hole not only reduced the rise of pressure in the back pressure valve but also improved the stability of the hydraulic control system.

Study on Encapsulation of Clay with Iron Tin Oxide Hydroxide and Its Application for Poly(vinyl chloride)

2017, 31 (12): 107-112; DOI: 10.19491/j.issn.1001-9278.2017.12.019

Abstract ( 500 )

Clay was encapsulated with iron tin oxide hydroxide［FeSnO(OH)5］ at different encapsulation ratios through a coprecipitation method. Effects of encapsulation ratio on the flame-retardant, tensile and thermal degradation properties of poly(vinyl chloride)(PVC) were evaluated, and the dispersibility of encapsulated clay was investigated. The results indicated that the addition of clay could not enhance the flame retardancy of PVC, and however, the dispersibility of clay in the PVC matrix could be improved at the loading of 10 phr, which led to a maximum mechanical performance of PVC. When the encapsulation ratio was set as 1∶5, PVC compounds achieved optimum flame retardancy and their tensile properties were also improved. The incorporation of encapsulated clay enhanced the char yield of PVC compounds at 800 ℃, reduced the initial decomposition temperature and maximum weight-loss peak temperature in the first stage, and increased the maximum weight-loss temperature in the second stage. These results suggested that the encapsulated clay could promote the thermal decomposition of PVC and make the decomposition products more stable in the first stage.

Application of Acid-resisting Ultramarine in PVC-U Profiles

2017, 31 (12): 113-116; DOI: 10.19491/j.issn.1001-9278.2017.12.020

Abstract ( 500 )

Ultramarine is an important pigment with a bright color, which is used for the shield of PVC-U profiles, and however, its molecular structure makes ultramarine especially vulnerable by acid. The development of acid-resisting ultramarine is necessary for improving the comprehensive performance of PVC-U profiles. This paper reported the acid-resistant tests for an acid-resisting ultramarine pigment by the addition of HCl and also presented the comparison results of extrusion test for different types of ultramarine pigments. An investigation was conducted for the effects of different types of ultramarine on the processing properties and weatherability, coloring property and glossy degree, and the obtained results might provide a reference for the use of ultramarine pertinent in PVC-U profiles.

Design of Demolding Mechanism and Injection Molds for iPad Brackets

2017, 31 (12): 117-123; DOI: 10.19491/j.issn.1001-9278.2017.12.021

Abstract ( 490 )

To overcome a demolding difficulty during the injection molding process for a stem-bracket part for iPads, three types of demolding mechanisms were designed. In these mechanisms, a bevel slider core pulling mechanism was adopted for a side simple structural feature, a small cylinder slide block core pulling mechanism was adopted for a deep hole feature, and a combined core pulling and demolding mechanism was adopted for the complicated central position. In the case of design of the combined mechanism, a die-bending pin-driving slider mechanism was combined with the three synchronous linkage slider core pulling mechanisms driven by a rear mould three-linkage cylinder. This demolding mechanism could conduct the core pulling at the corner and let out the mold motion space, and then the three-linkage mechanism could realize a synchronous linkage to internal contraction type three-slide block core pulling mechanism. The results indicated that the mechanism had a simple and practical structure.

Design of Three-plate Molds with Edge Gates

2017, 31 (12): 124-127; DOI: 10.19491/j.issn.1001-9278.2017.12.022

Abstract ( 1326 )

In general, the three-plate mold was only suitable for a point gate, and the artificial removal should be conducted for the freezing resin in the gating system of the two-plate mold with an edge gate. This paper reported a design of a three-plate mold with an edge gate for the partial gear on intermittent wipers. In this mold, the gate was designed as a short edge gate with a length of 2 mm and a tilt angle of 30 °. The mold opening was successfully performed in a correct order and distance through a design of the complex limiting mechanism with big and small pull rods. This mold design extends the applicable range of the three-plate mold and realizes the automatic separation of injection-mold parts with the freezing resin in the gating system, thus improving the production efficiency and saving the labor cost.