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2018, Volume 32 Issue 09 Publication date: 26 September 2018 Previous Issue Next Issue

Research Progress on Inorganic Flame Retardants

2018, 32 (09): 1-8; DOI: 10.19491/j.issn.1001-9278.2018.09.001

Abstract ( 652 )

This paper reviewed the research progress in inorganic flame retardants. Based on the classification of inorganic flame retardants which were divided into metal hydroxide, carbon-, phosphorus-, nitrogen-, silicon-and boron-containing flame retardants and the other ones, the mechanism, current research status, advantages, disadvantages and applications of each type of flame retardants were introduced extensively. Finally, the future trends in the development of inorganic flame retardants were prospected.

Research Progress in Toughening Modification of Polyimides

2018, 32 (09): 9-16; DOI: 10.19491/j.issn.1001-9278.2018.09.002

Abstract ( 816 )

This paper overviewed the recent research progress in the toughening modification of polyimides at home and abroad and also summarized the toughening modification methods including the hyperbranching toughening, toughening with flexible groups, diamine or dianhydride and structural modification. Hyperbranched polymers can reduce the entanglement of molecular chains due to a large number of end groups and highly branched 3D structure, and their flexible groups can improve the flexibility of molecule chains. Both of the molecular features can enhance the toughness of polyimides. The toughness of polyimides can also be improved by the new-designed diamine and dianhydride. Moreover, the change in structure of the original molecular chains can reduce the conjugates between molecular linkages and enhances the toughness of polyimides accordingly. Finally, the further research direction and development trend were prospected. The synergistic toughening method was highly recommended for polyimides by a combination of hyperbranched polymer and flexible groups with hyperbranched polymer and diamine, dianhydride.

Research Progress in Graphene-based Flame-retardant Polymers

2018, 32 (09): 17-24; DOI: 10.19491/j.issn.1001-9278.2018.09.003

Abstract ( 557 )

This paper reviewed the recent research progresses in polymers/graphene, polymers/modified graphene and polymers/graphene/flame retardant nanocomposites and also introduced their flame retardance mechanisms. The effect of graphene on the mechanical properties of polymers was discussion, and the future development direction in the flame retardancy of polymers with graphene was prospected.

Preparation and Thermal Conduction Performance of Poly(vinylidene fluoride)/Graphite Composites as Heat-exchanger Sheet Materials

2018, 32 (09): 25-31; DOI: 10.19491/j.issn.1001-9278.2018.09.004

Abstract ( 641 )

Poly(vinylidene fluoride) (PVDF)/graphite composites were prepared by a solution-blending method, and the effects of graphite content and compounding process on the thermal conductivity of composites were studied. The results indicated that there was a clear increase trend observed in thermal conductivity of the composites with the graphite content increasing over 40 wt %. The thermal conductivity of composite reached 20.92 W/（m·K） when 70 wt % of graphite was added, which is 110 times as much as that of pure PVDF. The thermal conductivity reached a maximum value at the graphite weight ratio of 1∶9 with the particle sizes of 270 and 106 μm, respectively. The higher thermal conductivity could also be achieved for the composites by using laminated rotor than by using drum-shaped rotor. Moreover, the thermal conductivity was slightly affected by rotor speed and mixing time. The plate heat exchanger plate based on the PVDF/graphite composite was designed and prepared to verify the feasibility of experimental production.

Study on Extrusion Swell Behavior of Highly Filled Polypropylene Nanocomposites

2018, 32 (09): 32-35; DOI: 10.19491/j.issn.1001-9278.2018.09.005

Abstract ( 463 )

Three types of highly filled polypropylene (PP) nanocomposites were investigated by a capillary rheometer, and the effects of die temperature, shear rate, melt pressure, nano-particle filling ratio and morphology of nanoparticle on the melt-extrusion swell ratio of PP nanocomposites were studied. The results indicated that these three types of PP nanocomposites presented a decrease in melt extrusion swell ratio with an increase of die temperature by a linear relationship. The melt extrusion swell ratio also increased with an improvement of shear rate but decreased with an increase of filler filling ratio. However, it increased with an increase in melt pressure and melt pressure. There was a retarded decreasing trend observed in melt extrusion swell ratio with an increase of filling ratio. The flake nanoMg (OH)2 filling system exhibited the smallest melt extrusion swell ratio in the three composite systems at the same volume fraction and temperature, but the spherical nano-CaCO3 filling one presented the greatest value.

Effect of Temperature on Mechanical Properties of Polyurethane Solidifying System

2018, 32 (09): 36-41; DOI: 10.19491/j.issn.1001-9278.2018.09.006

Abstract ( 2534 )

To explore the adaptability of polyurethane (PU) solidified ballast bed at different ambient temperatures, the effect of temperature on the tensile, adhesive and mechanical properties of PU solidifying system were investigated. The results indicated that the tensile modulus, tensile strength, and cohesive strength of the PU-solidified material increased gradually with a decrease of ambient temperature from -60 ℃ to 70 ℃. The breakage occurred in the middle point of tensile bar. The glass transition temperature (Tg) was about -50 ℃. The loss factor of the solidified material at the ambient temperature is close to Tg is higher than that at the other ambient temperatures, and the deformation performance is also better around Tg. The PU solidifying system presented more excellent performance under a low-temperature environment. The Tg of the solidified material decreased with an increase of molecular weight of polyether polyol. This type of PU-solidified material could be used in different temperature environments. On the other hand, the high molecular-weight polyether polyols are more suitable for the use of PU solidified ballast bed under a low-temperature environment.

Preparation and Properties of Wood Plastic Composites Based on PE-LD and Eucalyptus Flour Powders

2018, 32 (09): 42-48; DOI: 10.19491/j.issn.1001-9278.2018.09.007

Abstract ( 491 )

The PE-LD/eucalyptus flour powders wood plastic composites were prepared by a twin-screw extruder and an open-type refine machine using PE-LD-g-MAH a compatibilizer, and the effects of molding temperature, molding time, PE-LD-g-MAH concentration and preparation methods on the tensile strength and notched impact strength of the composites were investigated. The morphology and chemical structure of the composites were characterized by SEM and FTIR. The results indicated that the optimum molding temperature and time is 160 ℃ and 10 min for the preparation of composites, and the use of the open-type refine machine and PE-LD-g-MAH led to the excellent mechanical properties for the composites due to a better dispersion and interface bonding strength of eucalyptus flour powders. The tensile strength of composites increased from 16.53 MPa to 24.46 MPa, and their notched impact strength increased from 2.04 kJ/m2 to 4.58 kJ/m2. The improvement in mechanical properties was due to the enhanced interface-bonding strength derived from the esterification reaction between PE-LD-g-MAH and the hydroxyl groups on the surface of eucalyptus flour powders.

Preparation and Properties of High-toughness and High-strength Polyketone/Polyamide 66 Blends

2018, 32 (09): 49-52; DOI: 10.19491/j.issn.1001-9278.2018.09.008

Abstract ( 671 )

The polyketone (PK)/PA66 blends were prepared by a melting extrusion method and their morphology, crystallization behaviors and mechanical properties were investigated by scanning electron microscopy, differential scanning calorimeter and mechanical performance measurements. The results indicated that the PA66 domain dispersed in the matrix exhibited a small particle size and uniform distribution at a low content. The impact strength of the blends is 29.5 kJ/m2 at the PK/PA66 weight ratio of 80/20 in a dry state but 4 times as much as that of pure PK in the wet state. Moreover, the strength and modulus of the blends were also improved significantly. However, when the PA66 content was relatively high, the domain size of PA66 phase increased remarkably, followed by a decrease in impact strength. The introduction of PA66 reduced the crystallinity of PK significantly.

Preparation of Hydrophobic Intumescent Flame Retardant Polypropylene and Its Flame-resistant Synergistic Effect with La₂O₃

2018, 32 (09): 53-56; DOI: 10.19491/j.issn.1001-9278.2018.09.009

Abstract ( 554 )

Pentaerythritol and ammonium polyphosphate were surface-modified with tetraethoxysilane to prepare a series of intumescent flame retardants (IFR). The surface modification effect was confirmed by FTIR and TGA analysis. Nano Lanthanum Oxide (La2O3) were added into the modified flame retardants as a synergistic additive for flame retardancy and then melt blended with polypropylene (PP) to prepare the hydrophobic flame-retardant PP. The modification technology, the flame retardant and mechanical properties of polypropylenes were investigated. The results indicated that the hydrophobic properties of the modified PP were improved, and their flame-retardant and mechanical properties were improved considerably with the addition of La2O3.

Preparation and Properties of TPU/Reduced Graphene Oxide-poly(p-phenylenediamine) Composite Films

2018, 32 (09): 57-63; DOI: 10.19491/j.issn.1001-9278.2018.09.010

Abstract ( 492 )

Graphene oxide (GO) was prepared by a Hummer's method, and then the in-situ polymerization of polyparaphenylene diamine (PPDA) was performed on the surface of GO. The resulting GO was further reduced by hydrazine hydrate to obtain a RGOPPDA hybrid. Furthermore, the TPU/RGO-PPDA composite films were prepared by a solution coating method, and their structure and performance were characterized by FTIR, XRD, SEM, TEM, XPS, oxygen permeation meter and high resistance meter. The results indicated that the in-situ polymerization of PPDA onto GO significantly improved the lipophilicity of GO, which favors the dispersion of GO in DMF. With this reason, the RGO-PPDA achieved a uniform dispersion in the TPU matrix. When 0.98 wt % of RGO-PPDA was added, the oxygen transmission rate of the composite film decreased by 73.28 % compared to pure TPU film, and its electrical conductivity increased by a factor of 8, indicating good barrier and antistatic properties.

Study on Relationship Between Structure and Melt Viscosity of Polyolefin Elastomer

2018, 32 (09): 64-70; DOI: 10.19491/j.issn.1001-9278.2018.09.011

Abstract ( 566 )

The chain structure of several polyolefin elastomer (POE) samples was characterized by GPC and NMR, and their melt flow stability at high extrusion rate and their melt viscosities at various shear rates and temperatures were investigated by capillary rheometer. The relationship between the chain structure and melt viscosity were further analyzed. The results indicated that there was an unstable flow in the polymer melt with higher molecular weight with an increase of shear rate, and the surface of the melt extrudate became distorted. The critical shear rate also becomes lower if the molecular weight and co-monomer content were higher and the temperature was lower. The shear viscosity of POE was greatly influenced by the molecular weight and was almost not related to the co-monomer content. The polymer melts with various molecular weights and their compositions have the approximately same viscous flow activation energy around 2.8×10^4 J/mol. Based on the Carreau Equation, Cross Equation and Arrhenius Equation, the semi-model correlated with the zero shear viscosity, weight-average molecular weight and temperature and the semi-model related to correlated with the melt apparent viscosity, zero shear viscosity and shear rate were established. Both of the two equations are available to predict the melt viscosity of POE in the temperature range of 130~190 ℃, in the shear rate range of 10~2 000 s-1, in the weight-average molecular weigh range of 4.2×10^4 ~1.24×10^5 g/mol.

The Effect of Cross-linking Processing Condition on Performance of Seaweed Residue Mulch Film

2018, 32 (09): 71-77; DOI: 10.19491/j.issn.1001-9278.2018.09.012

Abstract ( 485 )

This paper reported an investigation on the effects of three different cross-linking methods, i.e. CaCl2-crosslinking, HCl-crosslinking and mixed CaCl2+HCl-crosslinking, on the mechanical and physical properties of seaweed residue mulch film. The results indicated that the seaweed residue mulch film achieved the tensile strength of 15.87 MPa and maximum elongation at break of 8.220 % at the crosslinking time of 15 min when a mixture of CaCl2 and HCl was used at the concentrations of 1.5 and 0.5 wt%, respectively. Meanwhile, the seaweed residue mulch film obtained a water vapor permeability of 1.454×10-9 g·m/m2·h·Pa and maximum transmittance of 7.556 %. The seaweed residue mulch film was found to gain the optimal comprehensive properties in this condition.

Study on Preparation and Performance of Thermal Conductive Graphene Oxide/ Polybenzoxazine Composites

2018, 32 (09): 78-84; DOI: 10.19491/j.issn.1001-9278.2018.09.013

Abstract ( 529 )

Silane-functional benzoxazines (B-TES) were synthesized by a Mannich condensation method using aminopropyltriethoxysilane, bisphenol.A and paraformaldehyde as precursors. The resulting B-TES was introduced into the composite system containing the graphene oxide (GO) and bisphenol-A-aniline-based monomeric benzoxazine (BA-a), and then the thermal curing process of this composite system was investigated by Fourier-transform infrared spectroscopy, differential scanning calorimetry and rheological analysis. The thermal conductivity of poly(BA-a/B-TES)/GO composites were measured with a “laser flash” technique. The results indicated that the thermal conductivity increased from 0.29 W/（m·K） to 0.56 W/（m·K） when the content of GO/B-TES increased from 1 wt % to 6 wt %. The thermal boundary resistance (Rb) between the GO and poly(BA-a) matrix was theoretically predicted according to the Maxwell-Garnett effective medium approximation, and the calculated Rb decreased from 150×10-9 m2· K/W to 130×10-9 m2· K/W due to the bridge connection of the B-TES. In addition, the poly(BA-a/B-TES)/GO composites also exhibited a high thermal stability and low surface energy.

Study on Deterioration Model of Mechanical Properties of GFRP Bars in Alkaline Solution

2018, 32 (09): 85-89; DOI: 10.19491/j.issn.1001-9278.2018.09.014

Abstract ( 432 )

To study the deterioration law of mechanical properties of glass fiber reinforced composite (GFRP) bars in an alkaline solution, tensile tests were carried out using 20 mm and 25 mm GFRP bars for 30 days, 90 days and 180 days to obtain the mechanical properties such as ultimate tensile strength and elastic modulus after different corrosion time in the alkaline solution were obtained. Meanwhile, a comparative study on the mechanical properties of GFRP bars with the same diameters was conducted in saline solution for 180 days. The residual tensile strength degradation model was established for the GFRP bars in the alkaline solution. The results indicated that the deterioration degree of mechanical properties of GFRP bars in the alkaline solution was worse than that in the saline solution at the same corrosion age. The tensile strength of GFRP bars tended to decrease with an increase of soaking time in the alkaline solution, and their corrosion rate in the early stage was faster than that in the later stage.The modified residual strength degradation model of GFRP bars was in a good agreement with the test results.

Study on Melting and Mixing Mechanism of Indomethacin in Hot-melt Extrusion

2018, 32 (09): 90-95; DOI: 10.19491/j.issn.1001-9278.2018.09.015

Abstract ( 605 )

The insoluble drug indomethacin (INM) and poloxamer 188 was used as a model drug and a carrier, respectively, and a solid dispersion of indomethacin and poloxamer 188 was prepared by a twin rotor mixer. The effect of rotor speed ratio on the melt transition and mixing process of INM was studied in terms of the two aspects of numerical simulation and experimental investigation. The results indicated that the distribution, dispersion mixing and melt diffusion of INM in the carrier could be enhanced by increasing the rotor speed ratio, and the dissolution process of INM was also accelerated.

Research on Correlation of Strain Hardening Modulus and Crack Growth Rate of Polyethylene Pipes

2018, 32 (09): 96-101; DOI: 10.19491/j.issn.1001-9278.2018.09.016

Abstract ( 622 )

Slow crack growth (SCG) is one of the main reasons for the brittle failure of polyethylene (PE) pipes. The SCG resistance of PE pipes should be evaluated strictly before formally service. In this paper, the strain-hardening modulus and crack growth rate of different types of PE pipe specimens (PE100) were obtained from strain-hardening and cone tests, respectively, and their correlation was studied to verify the validity of strain-hardening test for the evaluation of slow crack growth resistance of PE pipes. The results indicated that the crack growth degree of PE pipe specimens increased with an increase of test time, and the strain-hardening test results for different PE pipe specimens were identical to the cone test ones. The validity of strain-hardening test method for the evaluation of slow crack growth performance of PE pipes was also confirmed. The strain-hardening test not only had a small error but also made the subtle differences of slow crack growth resistance distinguished from different brands of PE100 pipes. The strain-hardening test results were more reliable than those of the cone ones.

Low-velocity Impact and Damage Detection on Stitched Carbon Fiber Foam Sandwich Composites

2018, 32 (09): 102-107; DOI: 10.19491/j.issn.1001-9278.2018.09.017

Abstract ( 580 )

In this paper, the effect of lowvelocity impact on the impact properties and damage for the stitched and unstitched carbon fiber foam sandwich composites was investigated. An impact test was first carried out on the stitched and unstitched sandwich composite panels by using a drop hammer impact tester at impact energy of 10 and 20 J, and the plots of the impact force and displacement as a function of time were obtained. Then, an immersion ultrasonic scanning imaging system was used to detect the damage of the composite panels after impact test, and the internal damage information of the panels was achieved. The results indicated that the impact force of the stitched composite panel was larger than that of the unstitched one under the same impact energy, whereas its punch contact time was shorter. Moreover, the damage area of the stitched composite panel was smaller than that of the unstitched one. This indicates that the delamination damage area was reduced and the impact resistance of the composite panel was improved, because the stitching could effectively inhibit the damage diffusion inside the composite panels under the impact load. The effect of stitching on the inhibition damage is significant in the impacted surface and innermost layers but that is normal in the middle ones.

Study of Effect of Warpage on FDM 3D Printing Plastic Parts

Lin-Fang DU

2018, 32 (09): 108-112; DOI: 10.19491/j.issn.1001-9278.2018.09.018

Abstract ( 665 )

A warpage mathematical model was established for warpage defects in the FDM 3D printing process, and the effect and variation trend of layer thickness, printing temperature, plate temperature and product thickness on the warpage of the printed parts were analyzed by an orthogonal experiment. The experimental results were verified by the mathematical model. The results indicated that there was a significant effect of layer thickness on the warpage and the printing temperature also affected the warpage considerably. However, the effects of plate temperature and wall thickness of the parts were not remarkable. The printing precision was improved significantly by 44.4 % with optimizing the FDM process parameters.

Preparation and Properties of Poly (vinyl alcohol) Films with Urea/ Formamide Complex Plasticizers

2018, 32 (09): 113-117; DOI: 10.19491/j.issn.1001-9278.2018.09.019

Abstract ( 981 )

A series of poly(vinyl alcohol) (PVA) films with urea/formamide complex plasticizers were prepared by a melt processing method, and their structure and properties were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry and mechanical measurement. The results indicated that the urea/formamide complex plasticizer affected the ordered structure of PVA molecular chains by destroying their inter/intra hydrogen bonds, thus improving the melt processing performance of PVA and decreasing its crystallinity degree.Furthermore, the toughness of the films was enhanced effectively.

Preparation and Performance of Castor-oil-based Polyurethane Modified with Organosilicone

2018, 32 (09): 118-123; DOI: 10.19491/j.issn.1001-9278.2018.09.020

Abstract ( 563 )

A series of plant-oil-based waterborne polyurethane (WPU) samples were synthesized using hydroxypropyl-terminated polydimethylsiloxane (HP-PDMS) and castor oil as raw materials by a prepolymer method. The different content of HP-PDMS was introduced into the polyurethane molecular chains to obtain the HP-PDMS/WPU hybrid composites through the chemical reaction between the OH groups on HP-PDMS and the NCO groups on IPDI. The hydrophobicity, thermal stability and mechanical properties of the composites were investigated by FTIR, TEM, thermal analysis, static contact angle and tensile experiment. The results indicated that the modified nanocomposites were synthesized successfully and their thermal degradation characteristic temperature at 5 % weight loss was enhanced from 225 ℃ to 248.5 ℃ due to the incorporation of HP-PDMS. Both the tensile strength and hydrophobicity of the composites could be fairly enhanced with the addition of small amounts of HP-PDMS.

Synthesis and Properties of Heat- and Migration-resistant Green Plasticizer and Its Plasticizing Effect on PVC

2018, 32 (09): 124-129; DOI: 10.19491/j.issn.1001-9278.2018.09.021

Abstract ( 687 )

Poly(1,4-cyclohexane dimethyl glutarate) was synthesized by a polycondensation method using tetra-n-butyl titanate as the catalyst, cyclohexane as dehydrating agent, 2-propylheptyl alcohol as a capping agent, and 1,4-cyclohexanedimethanol and glutaric acid as raw materials. The chemical structure of the resulting polyester was characterized by FTIR、1H-NMR and gel permeation chromatography, and its molecular structure was found to contain six-membered alicyclic, linear carbon chains and multi-functional groups including ester groups. The resultant polyester used as a plasticizer was incorporated into poly(vinyl chloride) (PVC) to form a plasticizing sample. This sample achieved the elongation at break of 677.15 %, whereas the PVC specimen plasticized with DOP obtained the one of 693.82 %. Compared to the specimen plasticized with DOP, the sample prepared in this work exhibited an increase in heat resistance by 158 ℃ and a decrease in migration of carbon by 16 %. This new plastizied PVC sample also presented a higher thermal stability and better extraction resistance.

Lightweight Design of Injection Molded Products Based on Multi-scale Co-simulation

2018, 32 (09): 130-134; DOI: 10.19491/j.issn.1001-9278.2018.09.022

Abstract ( 512 )

Aiming at the breakage of automobile engine mount bracket, a multi-scale co-simulation technology was analyzed in comparison with the traditional simulation one, and their reliability was verified.A reasonable improvement plan was proposed on the basis of the overall stress distribution of the mount bracket. The overall stress level could be distributed within the safe range when the maximum stress was reduced by 32.57 %, and meanwhile the mass was reduced by 7.27 %. This lightweight design was successful for the automobile engine mount bracket.

Injection Mould Structure of Elbow Joint with Special Elbow Pulling Core Mechanism

2018, 32 (09): 135-141; DOI: 10.19491/j.issn.1001-9278.2018.09.023

Abstract ( 520 )

According to the molding requirements of plastic part for a bent pipe joint of pump pipe, a single-cavity single point gate injection mould was designed, The demoulding of the inner product in the cavity was divided into two cases, i.e. the demoulding of the outer wall and the demoulding of the inner wall. Three conventional demoulding mechanisms was used for the demoulding of the outer wall, whereas a demoulding mechanism of complex bend pipe was adopted for the inner wall. The demoulding mechanism structure consists of a side core pulling mechanism, a special cylinder driving and oblique core pulling off module mechanism with a telescopic sliding block, and a variable form rod pushing mechanism. The design of the mechanism of the core pulling out of the mold with a telescopic sliding block of the cylinder drive was especially carried out. The inner core of the pipe was arranged skillfully by a linear core pulling method. Such a design could avoid the problems of complex mechanism design and difficult movement control caused by the traditional rotary core pulling method in the bend pipe section of the inner wall. This design could also save the size of die holder and reduced the cost of mould manufacture. The reasonable layout of die structure could provide a useful reference for the similar products.