2023, 37 (7):
1-8;
Abstract (
358 )
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A type of foaming materials based on poly（lactic acid） （PLA）/poly（butylene adipate-co-terephthalate） （PBAT） blends modified with an epoxy-type chain extender （ADR） was prepared through a hot press foaming process using azodicarbonamide as a foaming agent and nano-silica （SiO2） as a nucleating agent. The chain extension reaction of ADR with PLA and PBAT was confirmed by FTIR. The experimental results from melting flow tests indicated that the addition of ADR improved the melt strength of the foam precursor effectively. The cell morphology of the foaming materials was studied by SEM. When 0.3 phr of ADR and 2 phr of SiO2 were added， the cell average diameter of the foaming materials decreased to 48.63 μm and their cell density increased to 3.717×106 cells/cm3. Moreover， their bulk density decreased from 1.156 to 0.75 g/cm3 compared to that of pure PLA. The DSC， XRD， and DMA test results indicated that the addition of PBAT and SiO2 improved the crystallinity of PLA effectively， providing a better environment for the foaming process. The mechanical test results indicated that the addition of PBAT and ADR improved the tensile properties of the foaming materials， and the presence of bubbles improved their impact properties. The foaming materials presented impact strength of 25.94 kJ/cm2， which was 23.52 % higher than that of pure PLA.
2023, 37 (7):
9-15;
Abstract (
241 )
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40
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In this work， an intensive investigation was carried out to determine an optimal mean particle size of less than 100 μm for the powder electrostatic spraying process of polyoxymethylene （POM） powders through comparing the performance of powder coatings made from POM powders with different average particle sizes. Polypropylene and polyurethane were then incorporated to pure POM powders to improve the impact resistance of POM powder coatings. The performance of the resultant composite coating samples were evaluated by characterizing their thickness， hardness， thickness， impact strength， chemical resistance， morphology， and wear resistance. The results indicated that all of the coating samples exhibited good appearance， acid and alkali resistance， and salt resistance together with a uniform thickness and a smooth surface. There was no shrinkage orange peel and cracking phenomena. Their adhesion grades reached above grade 1 and their friction coefficients were as low as 0.261. All of these can meet the requirement of application standards for good mechanical properties and excellent friction resistance. Moreover， the composite coatings obtained impact strength of 4.42 and 5.12 N·m when 3 wt% PP and 15 wt% TPU were incorporated， respectively. With such a modification， the impact resistance of the composite coatings was greatly improved to meet the requirement for practical applications in the specific areas.
2023, 37 (7):
16-21;
Abstract (
241 )
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66
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In this study， poly（butylene succinate） （PBS） and ST-CE37B were used as a matrix and an chain extender， respectively， to prepare chain extended PBS samples through melt blending. Furthermore， the open-cell PBS foams were prepared by using a supercritical CO2 foaming method. The results indicated that the addition of chain extender increased the storage modulus of PBS by one order of magnitude and resulted in an increase in its crystallization temperature by 7.69 ℃. When the foaming temperature was 100 ℃ and the foaming pressure was 20 MPa， the open cell content and adsorption capacity for CCl4 of the CPBS foam reached 96.58 % and 31.76 g/g， respectively. Moreover， CCl4 and cyclohexane in water were both removed quickly by the CPBS foam.
2023, 37 (7):
22-26;
Abstract (
182 )
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34
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In this paper， a type of high-temperature-resistant polyimide （PI） resins terminated with phenylethynyl groups was prepared by using 2，3，3'，4'-diphenyl ether tetracarboxylic acid dianhydride and 9，9-bis（4-aminophenyl） fluorene as raw materials. The relationships between the chemical structure of the as-prepared products and their solubility， curing properties， and heat resistance were investigated by using Fourier-transform infrared spectroscopy， differential scanning calorimetry， and thermogravimetric analysis， and the relevant influencing mechanisms were studied. The results indicated that the oligomers had high solubility in organic solvents. The as-prepared PI resin samples exhibited a maximum glass transition temperature of 356 ℃， which increased by 41 oC with increasing the fluorenyl content. The cured PI resins presented a high thermal stability with a 5 wt% thermogravimetric temperature of above 520 ℃ in nitrogen， and their residual char yields were as high as 60 wt% at 800 ℃. The thermoset PI resins gained an improvement in temperature resistance and were expected to be applied in marine engineering equipments， national defense， military industry， and other fields.
2023, 37 (7):
27-33;
Abstract (
258 )
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27
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To improve the hygro-thermal resistance of polyurethane （PU） sealants for high-speed railway， a two-component PU sealant was prepared by using inorganic CaCO3 as a filler， and its mechanical performance， adhesion property， and thermal stability were examined to investigate the performance changes of the sealant after hygro-thermal aging tests. The corresponding aging mechanism was studied by using Fourier-transform infrared spectroscopy and scanning electron microscopy. The results indicated that hygro-thermal aging reduced the tensile strength of the PU sealant， and its elongation at break was enhanced at the initiate aging stage. The CaCO3 filler could inhibit the decay of mechanical properties， adhesion properties and thermal stability for the PU sealant. Microscopic analysis indicated that hygro-thermal aging resulted in the swelling and fracture of the chain segments of the PU sealant， leading to cracks in the PU sealant as well as a decrease in mechanical properties. The incorporation of the CaCO3 filler could prevent the cracks in the PU sealant and therefore improve its hygro-thermal resistance.
2023, 37 (7):
34-40;
Abstract (
283 )
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25
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A type of controlled-release drug hydrogels was prepared with curcumin as an original drug and polyvinyl alcohol as a carrier. The structure and performance of the as-prepared drug hydrogels were characterized by using balanced swelling and Fourier-transform infrared spectroscopy. The effects of drug-loading of the hydrogels were investigated by using the single factor and response surface methods， and the controlled-release properties of the drug hydrogels were evaluated through a standard curve. The experimental results indicated that the hydrogels obtained a maximum swelling rate of （171.53±0.21） % at 40 oC under the same conditions. Based on the single-factor method， the drug-loading of the hydrogels reached a maximum of （43.43±0.243 2） mg/g at 40 oC for 1.5 h under the initial curcumin concentration of 70 μg/mL. The results from the response surface analysis indicated that the initial concentration of curcumin generated the most significant effect on the drug-loading， followed with temperature. However， the adsorption time only had a relatively small effect on the drug-loading. In the phosphate buffered solution， the cumulative release rate of curcumin reached 88.1 %， indicating a certain controlled-release effect of the drug hydrogels.
2023, 37 (7):
41-46;
Abstract (
301 )
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28
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The chemica-resistant and antibacterial polycarbonate （PC）/polyurethane elastomer （TPU） blends were prepared through melt blending using PC， TPU， and antibacterial agents as raw materials. The effects of the amount， hardness， type of TPU and type of antibacterial agent on the properties of the blends were systematically studied. The results indicated that the processing fluidity， notched impact strength and chemical resistance of the blends increased with an increase in the TPU content. Compared to the polyether?type TPU， the polyester?type TPU with a high hardness is more advantageous to improving the notched impact toughness and chemical stability of the blends. When 0.6 wt% active ZnO was added， the PC/TPU blends obtained an antibacterial rate of over 99.9 % against Escherichia coli and Staphylococcus aureus.
2023, 37 (7):
47-52;
Abstract (
289 )
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27
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Polyimide （PI）/glass powder composite films were prepared through a two-step thermal imidization polymerization process using pyromellitic dianhydride （PMDA） and 5-amino-2-（4-aminophenyl） benzoxazole （BOA） as monomers and glass powders as a filler， and their structure and thermal and mechanical properties were investigated. The as-prepared composite films were fully imidized by showing a yellowish brown color. The composite films exhibited excellent thermal properties with a 5 wt% weight loss temperature between 556 and 565 °C， and their residual char yields were more than 60 wt%. Moreover， the composite films present a glass transition temperature of above 410 °C and a low thermal expansion coefficient of less than 5.3 ppm/K. Their tensile strength was determined to be 164~242 MPa， their tensile modulus ranged from 4.7 to 7.5 GPa， and their elongation at break was higher than 6.0 %. This indicates excellent mechanical performance of the composite films.
2023, 37 (7):
53-61;
Abstract (
263 )
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33
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A heat transfer model was established for rotational molding process heated electrically in heating phase based on static bed model to simulate temperatures at mold surface and inside mold in three cases by means of FLUENT software， and simulated results were compared with experimental results. At first， heating power was assumed to be constant in entire heating phase， and then in the improved model， the intensity of internal heat source at outer surface of mold was set as the one during temperature?increasing stage and the one during temperature?holding stage respectively to simulate variation of heating power. Meanwhile the temperature inside mold was equal to the mass?average temperature of powder and air inside mold before the start of powder melting， and the temperature of air inside mold after the moment. It was indicated that simulating accuracy for temperatures at mold surface by the improved model was higher than that for temperatures inside mold. For the thickness of hydrogen cylinder no more than 10 mm， root?mean?square relative errors of simulated temperatures with tested temperatures at mold surface and inside mold were both within 10 % in entire heating phase. These two root?mean?square relative errors were 5.1 % and 14.1 % respectively for hydrogen cylinder with thickness of 12 mm. In addition， the variation of liquid fraction of plastic layer with time was also obtained from simulated results in three cases.
2023, 37 (7):
62-67;
Abstract (
224 )
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44
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With an improvement in the manufacturing capacity of molds and injection molding machines， the demand for large injection molding parts becomes constantly emerging， especially in aerospace， new energy vehicles， large household appliances， transportation， and other fields. However， the technical difficulties in large injection molding parts cannot be ignored. In this paper， the difficulties in the injection molding process of large plastic parts with a thick wall were discussed， the relevant reasons were analyzed， and the countermeasures and practical effects were put forward. Finally， some suggestions for the future development of large-format plastic parts were proposed.
2023, 37 (7):
68-73;
Abstract (
322 )
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45
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In this work， we analyzed the factors affecting the tensile experimental results of thermoplastic polyethylene pipes， which included the ambient temperature and tensile test speed. The results indicated that the tensile performance of the pipes was greatly influenced by the test speed and the test ambient temperature. The test was conducted in strict accordance with the standard conditions to minimize personnel and environmental change factors that affect the test results. Through multi?group test and data analysis， the influence of test temperature and standard test temperature of the PP pipe are presented.
2023, 37 (7):
74-79;
Abstract (
412 )
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38
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In this work， a split molding process involving injection molding， extrusion， and welding was proposed to effectively reduce the molding difficulty of the inner liner of type-IV hydrogen storage bottle. A hot-melt welding experiment was conducted to evaluate the effects of heating temperature， welding time， and unit area welding pressure on the quality of the welding line of the samples. The tensile and impact properties of the samples on the welding line were measured， and the microstructure of the fracture surface of the welding line was investigated using scanning electron microscopy. The results indicated that the plastic fracture was the main form for weld failure， and the tensile strength on the weld line was essentially the same as that of the base material. Furthermore， the impact strength became higher. The experiments also identified the optimal welding process parameters as a heating temperature of 240 ℃， a welding time of 60 s， and a unit area welding pressure of 0.10 N/mm2. Under this process condition， the optimal mechanical properties were obtained for the welding line.
2023, 37 (7):
80-86;
Abstract (
299 )
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29
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A novel flame retardant （TDK） containing nitrogen， phosphorus， and silicon elemetns was synthesized by using 9，10-dihydro-9-oxa-10-phosphoxanthophosphor-10-oxide （DOPO）， 1，3，5-three glycidyl different melamine urea acid ester， and gamma-ammonia ethyl ammonium propyl silane as raw materails. The resultant TDK was blended with ammonium polyphosphate （APP） and melamine pyrophosphate （MPP） to prepare intumescent-flame-retardant polypropylene， and its performance was compared with the traditional intumescent-flame-retardant PP/APP/MPP/dipentaerythritol （Di-PE） composite. The structure and composition of TDK were verified by FTIR， 31P solid-state NMR， and elemental analysis. Thermogravimetric analysis indicated that PP began to degrade at 329.0 ℃ when 30 phr of IFR was added. On the other hand， the carbonization reaction of the PP/APP/MPP/TDK composite was earlier than that of PP matrix， and its decomposition temperature was 273.8 ℃. Moreover， the carbon residue rate of the PP/APP/MPP/TDK composite was 13.8 % higher than that of pure PP. In addition， the PP/APP/MPP/TDK composite presented a limiting oxygen index of 30.5 wt%， and its flame retardant classification reached V-0 level classification in the vertical combustion. Its heat release rate was reduced by 86 %， its smoke production rate was reduced by 78.8 %， and its mechanical properties were better than those of the PP/APP/MPP/Di-PE composite. The flame retardant performance and corresponding mechanism of the developed composite were further analyzed by using scanning electron microscopy， infrared spectroscopy， and energy dispersion spectroscopy. The results indicated that there was a synergistic effect of phosphorus， nitrogen and silicon on the flame retardancy of PP in the condensed phase.
2023, 37 (7):
87-97;
Abstract (
229 )
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25
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With the increasingly serious problems in plastic pollution， degradable plastics have been receiving attention gradually. However， the rapid and accurate detection of the effectiveness and safety of degradable plastics becomes a crucial issue. In this paper， several techniques for the rapid detection of degradable plastic structures， such as spectroscopic analysis and nuclear magnetic resonance spectroscopy， were reviewed. The purpose of this review was to provide assistance for the rapid structural detection of degradable plastics and also to facilitate market regulation. In the future of rapid detection technology， it is necessary for degradable plastics to improve the accuracy and sensitivity of detection and also to develop more practical and environmentally friendly detection methods to provide an effective technical support for the production， applications， and post?treatment of degradable plastics.
2023, 37 (7):
98-103;
Abstract (
324 )
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37
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The problems in the detection of carbon black content of ash-containing PE materials were analyzed by thermogravimetry from the view point of standardization and production technology. It should be pointed out that the current detection method of carbon black content was unreasonable due to the unreasonable setting of calcination conditions as well as the difference in the ash content of PE materials existed before and after calcination. Such a difference leads to the shortage of deviation in the test results of carbon black content. A new method was proposed to adjust the calcination conditions and reduce the calcination temperature and the quality change of ash before and after calcination， and eliminate the significant influence of the existence of ash on the test results of carbon black content of PE materials. These can meet the practical requirement for the detection of the carbon black content of ash-containing PE materials.
2023, 37 (7):
104-109;
Abstract (
226 )
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27
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To realize the recycling and reutilization of polytetrafluoroethylene （PTFE） materials， the suppressed and unsintered PTFE arc extinguishing nozzle blank was preprocessed， and then its scrap was collected to obtain recycled PTFE （R-PTFE） powders. The R-PTFE/MoS2/glass fiber （GF） composite were obtained by incorporating 5 wt% MoS2 and 15 wt% glass fiber into the R-PTFE） powders. Based on the particle size and scanning electron microscopic analysis results， the R-PTFE powders exhibited a fine particle size after crushing three times. The mechanical test results indicated that the R-PTFE/MoS2/GF composite obtained optimal mechanical performance when incorporating 300-mesh glass fiber powders into the R-PTFE powders after crushing three times， and its tensile strength and elongation at break were 13.17 MPa and 352.58 %， respectively.
2023, 37 (7):
110-114;
Abstract (
230 )
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33
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According to the structural characteristics of A-pillar guard board of a vehicle， a large injection mold was designed. The problem in the melt filling of large thin-walled plastic parts was solved by using a sequential valve gating hot runner. The bending and fracture of inclined pushrod problems were solved by using a double inclined push rod and guide rod inclined push rod lateral core-pulling mechanism. The mold was contrasted through the combination of diaphragm water wells， inclined water pipes， and straight-through water pipes. Through using such a nearly conformal waterway of temperature control system， the forming cycle was controlled within 30 s， decreasing by about 10 % in comparison to conventional molds. The molded plastic parts obtained a dimensional accuracy of MT3.
2023, 37 (7):
115-121;
Abstract (
299 )
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46
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In this paper， an opposite type of bi-color stacking injection mold was designed for a bi-color grille mask of a certain car. The bi-color mold was composed of two pairs of sub-mold， which were installed back to back. The moving part of the two sub-moulds was fixed on the central-rotating platform. A flip mold structure was adopted for the mold. A transparent part was injection molded for the first color， and then the black part was molded for the second color. This avoids the problem of inclined-top trace lines on the surface A of the transparent part. To ensure that the transparent part was located on the side of the cavity and avoid the plastic part falling off during the rotating process， a rotating-fixing mechanism was designed to clamp the transparent part. Aiming at solving the problem of buckle of black part， a slider mechanism and an inclined-top core-pulling mechanism were designed to accomplish the demolding of the buckle area. The bi-color mold can run stably and reliably according to practical verification to meet the requirement for production.
2023, 37 (7):
122-128;
Abstract (
297 )
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49
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This review paper focused on the metal compounds-based flame-retardant synergists with various specific microstructures， such as layered double hydroxides， metal-organic frameworks， core-shell structural compounds， and nanoscale metal compounds， and the applications of these synergists in polymers were reviewed. In addition， the application system based on the microstructure-synergy efficiency-synergy mechanism was prospected.
