2023, 37 (3):
1-6;
Abstract (
424 )
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70
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As a biodegradable material， PLA has poor impact toughness， resulting in a limitation of application. To address this problem， there have been many elastomer-filling schemes proposed for the toughening of PLA； however， most of these schemes cause the strength loss of PLA or the introduction of non-degradable components as compatibilizers. In this case， we developed a new processing method to solve this problem through filling PBAT and processing with a tri-screw extruder combined with cold-pressing with a roll-to-roll machine. Through the characterization of the compounding samples prepared with this processing method， there was an elongation effect of the roll-to-roll cold-pressing process on PBAT as observed from the SEM image， and the in-situ fibrillation induced by the elongation effect was noted. Meanwhile， the experimental results indicated that the elongation effect promoted the crystallization of PLA. The tensile experiments proved that the in-situ fibrillation and crystalline improvement played a role in the toughening and strengthening of PLA. The influence of this processing method on the thermal stability of the compounding samples was also evaluated through thermogravimetric analysis， and its toughening mechanism was analyzed. This work may provide a new methodology for the toughening of PLA.
2023, 37 (3):
7-12;
Abstract (
322 )
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43
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In this paper， fluoroelastomer-based composites were modified with carbon nanotubes， and the effects of carbon nanotube content on the physical properties， thermal properties， microstructure morphology， air permeability， and macroscopic mechanical properties of the modified fluoroelastomer composites were investigated. Aging experiments were conducted for the composites under simulated high-temperature and high-pressure conditions， and their hardness changes， the volume changes， tensile properties， tearing properties and compressive permanent deformation were evaluated and analyzed before and after the aging experiments. The results indicated that the modified fluoroelastomer composites presented an increase in tensile strength and tear strength with increasing the carbon tube content. Based on the observation for the brittle fracture surface and thermal weight loss section， a uniform dispersion of carbon nanotubes was confirmed at their high contents. A network structure was constructed in the composites by carbon nanotubes as a one-dimensional nanomaterial， which contributed to the gas barrier performance of the composites. According to a comparison between the performance data before and after experiments， the introduction of carbon nanotubes maintained the comprehensive properties of the fluoroelastomer composites after the aging experiments.
2023, 37 (3):
13-18;
Abstract (
284 )
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34
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In this paper， coir-fiber-reinforced epoxy composite geogrids were prepared by using coir fibers as a reinforcement material， and the effects of the content， length， and rib spacing of coir fibers on their performance were investigated through the tensile tests of multi rib grids. The results indicated that the tensile yield force of the composite geogrids presented an increase at first and then tended to decrease with an increase in the coir fiber content. The composite geogrids obtained maximum values in tensile properties at a coir fiber content of 1 wt%； however， their tensile performance was poorer than that of pure epoxy grid when the coir-fiber content exceeded 1 wt%. The tensile yield force of the composite geogrids also exhibited an increase at first and then decreased with increasing the coir fiber length， the tensile yield force of composite grid also increased first and then decreased. Their tensile yield force reached a maximum value at a fiber length of 1 cm， which was 34.33 % higher than that of pure epoxy grid. Compared to the fiber length and content， the rib spacing presented a more significant influence on the composite geogrids， whose tensile yield force reached a maximum at a rib spacing of 1 cm.
2023, 37 (3):
19-23;
Abstract (
246 )
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27
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In this paper， a coating was obtained through mixing a LiCl-dissolved chitosan solution with a polyvinyl alcohol glue solution （8 wt%）. Then， this coating was coated on the porous polyethylene film to form a heat transfer film. The effect of addition amount of the chitosan solution on the properties of the heat transfer film was investigated. The heat transfer film exhibited a high moisture permeability of 2 600 g/（m2·24 h） at a chitosan solution content of 80 wt%， indicating good water resistance. The heat exchange film was also cut and assembled into a heat exchange core. This heat exchange core showed a net fresh air supply rate of 95 % under an air volume of 100 m3/h as well as an enthalpy efficiency of 77.8 % under the heating condition. This suggests good energy-saving effect. A new fan with the heat exchange core was evaluated through a three-month operation. Compared to the data obtained before the new fan， there was no attenuation in the performance after the three-month operation.
2023, 37 (3):
24-29;
Abstract (
348 )
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40
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In this paper， the effects of the silica reinforcing material and coupling agent on the mechanical properties of conductive rubbers were investigated. The experiment results indicated that the addition of the silica reinforcing material and coupling agent could enhance the mechanical properties of conductive rubbers effectively， but there was little influence on their conductance. The conductive rubbers obtained optimal mechanical performance at a silica content of 15 wt% and a coupling-agent content of 0.7 wt%. In addition， the adaptability of conductive rubbers in high-temperature environments was evaluated. The results indicated that the conductive rubbers kept relatively stable mechanical properties and electrical conductance within 96 hours in high-temperature environments.
2023, 37 (3):
30-34;
Abstract (
305 )
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49
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Regenerated transparent PC sheets （RPC-SH） were prepared by using the waste transparent polycarbonate （RPC） selected from industrial solid wastes. The surface of RPC-SH was hardened using silicone （STC2000） and acrylic （SY-5223） transparent wear-resistant coatings to obtain hardened sheets， i.e. Si-RPC-SH and SY-RPC-SH. The coating stability， surface scratch resistance， transparency and mechanical properties of the three types of hardened sheets were investigated. The results indicated that the two types of coatings could be well combined with the surface of RPC-SH， and their adhesion grade reached Grade 1. This indicates a certain amount of resistance to hot water， acid， alkali， and salt corrosion. After the surface hardening treatment， the pencil hardness of RPC-SH increased from 5B to H and HB， and their weight loss after loading was smaller. However， their surface wear resistance and scratch resistance were improved significantly. Owing to a lower light refractive index of the coating， the light transmittances of Si-RPC-SH and SY-RPC-SH were slightly enhanced compared to RPC-SH， but their hazes were reduced. With the influence of organic solvent in the coating， the mechanical strength of the hardened RPC-SH was lower than that of the pristine RPC-SH.
2023, 37 (3):
35-41;
Abstract (
346 )
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30
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A series of poly（vinyl chloride） （PVC）/epoxy resin （E-12）/maleimaric anhydride （MPA） composite foaming materials were successfully prepared through melt blending and irradiation crosslinking. The chemical structure of MPA was characterized using Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy （1H-NMR and 13C-NMR）. The effects of curing content of E-12/MPA （EM） on the properties of the composite foaming materials were investigated by means of gelatin content， mechanical measurement， scanning electron microscopy， and water absorption tests. The results indicated that the composite foaming materials containing 10 wt% EM obtained a gelatin content of 42.3 wt%， which was 9.9 % higher than that before modification. Compared to pure PVC foaming material， the composite foaming ones showed an increase in tensile strength by 23.4 %，in compression strength by 26.7 %， and in compression modulus by 32.5 %. The elongation at break of the composite foaming materials decreased from 306.33 % to 220.68 %， and their water absorption increased from 1.5 % to 3.4 %. The composite foaming materials also exhibited a good cell structure.
2023, 37 (3):
42-51;
Abstract (
319 )
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24
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A separation membrane based on the environmental protection concept was developed in this work. In this membrane， covalent organic framework （COF） membrane materials presented unique advantages. At present， the studies on the two-dimensional structure of COF materials are relatively mature； however， there are few studies on three-dimensional COF materials （3D-COFs）. This paper introduced the synthetic and post-modification methods of 3D-COFs membrane materials and discussed the specific application of 3D-COFs membrane materials for CO2 capture. Finally， the future development direction of 3D-COFs membrane materials was prospected.
2023, 37 (3):
52-63;
Abstract (
523 )
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49
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This paper introduced the applications of polyl（actic acid） （PLA） antibacterial/antioxidant active packaging films in the food-packaging field and reviewed the research progress in their safety evaluation. The PLA antibacterial/antioxidant active packaging films were analyzed and summarized from the aspects of their application in food packaging and their safety evaluation for PLA materials. This paper may provide a reference for the research of the PLA antibacterial/antioxidant active packaging films.
2023, 37 (3):
64-70;
Abstract (
285 )
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36
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In this paper， five types of interface connection modes and their performance of fiber-reinforced composite （FRP）/concrete composite beams were analyzed and compared from the aspects of the perspectives of theory， experiment and field application. The mechanical characteristics， calculation models， and engineering applications of the FRP/concrete composite beams were discussed， and the improvement methods of various connection methods and the combination of multiple connections were introduced. These methods not only enhanced the interface connection performance of the composite beams but also optimized the beam structure.
2023, 37 (3):
71-76;
Abstract (
475 )
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36
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Aiming at optimizing the warpage deformation of PA6/GF30 intake manifold to improve the air intake performance of the manifold， a response surface experiment was designed by using Box-Benhnken， and then a random forest regression model was constructed. The data obtained from the response surface experiment were used as the original data for optimal prediction. The results indicated that the predicted values of the warpage deformation of the manifold exhibited a good fit with the actual values， suggesting that the random forest regression model was effective. The air intake process of the manifold was simulated by means of the Moldflow-Ansys joint simulation. The simulation results showed that the warpage deformation of the optimized manifold decreased from 1.413 mm to 1.032 mm， which was reduced by 27 %. The deviation rate and unevenness of the intake air flow decreased from 7.498 3 % to 4.242 8 % with ［-3.944?153?2 %， 3.554?111 %］ and ［-2.545?082?2 %， 1.697?694?7 %］， respectively， indicating a significant improvement in air intake performance.
2023, 37 (3):
77-82;
Abstract (
436 )
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31
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The effects of molding temperature， molding pressure， pressure holding time and clamping speed on the surface quality of carbon fiber/epoxy sheet molding compound molded products were investigated by means of an orthogonal test. The variance analysis indicated that the influencing factors on the surface roughness became more significant by the following order： molding temperature T > pressure holding time t > molding pressure P > clamping speed v. Through the multiple comparison of the Duncan’s test， the difference in average values between the different levels of various influencing factors was further discussed， and the relationship diagram of the measured average values of surface roughness corresponding to each factor was constructed. The molded products showed a slow increase in surface roughness at first， followed by a sharp increase with increasing the molding temperature. The effects of pressure holding time and molding pressure on the surface roughness were opposite. The surface roughness did not change significantly with an increase in clamping speed. The optimal process parameters were obtained as follows： molding temperature T=130 ℃， molding pressure P=600 kN， pressure holding time t=720 s， and clamping speed v=15 mm/s. The molding experiment indicated that under these optimal process parameters， the surface roughness was reduced by 19.3 % compared to the minimum value obtained from the orthogonal test. This result suggests that the surface quality of molded products was improved effectively.
2023, 37 (3):
83-87;
Abstract (
500 )
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37
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A mixture of nickel ion-containing metal organic frameworks （Ni-MOF） and piperazine pyrophosphate （PPAP） was incorporated into epoxy resin （EP） to form compounding EP thermosets， and their flame-retardant performance and smoke release behaviors were investigated by means of limiting oxygen index （LOI）， vertical burning test， and cone calorimeter （CONE）. The results indicated that the compounding EP thermosets achieved a UL 94 V-0 classification in the vertical burning test， and their LOIs reached 27.9 vol% with the addition of 6 % PPAP. However， the EP/PPAP/Ni-MOF compounding thermosets obtained a UL 94 V-0 classification together with a LOI of 29.3 vol% with the addition of 5 wt% PAPP/Ni-MOF at a mass ratio of 99∶1. These results demonstrated that the addition of a small amount of Ni-MOF effectively improved the flame retardancy for EP thermosets. Cone calorimetric test results indicated that the EP/PPAP/Ni-MOF compounding thermosets exhibited an obviously lower heat release rate， total heat release， smoke release rate and total smoke release than the EP/PPAP ones under the same loading of flame retardants. The addition of Ni-MOF inhibited the combustion intensity and smoke release of EP thermosets. Nickel ions in Ni-MOF could be cross-linked with the phosphoric acid and polyphosphoric acid generated from the thermal degradation of PPAP， which resulted in more phosphorus components remaining in the condensed phase. Consequently， sufficient char layers with good strength were formed to effectively inhibit the release of heat and smoke during combustion. This enhanced the fire safety performance of EP thermosets significantly.
2023, 37 (3):
88-93;
Abstract (
321 )
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33
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To explore the difference in the biodegradation performance of a new type of masks under two composting conditions： aerobic and anaerobic， the biodegradation rates of the masks were obtained through the measurement according to the internationally recognized standard methods. The statistical results indicated that this type of masks exhibited biodegradation rates of 66.4 % and 21.2 %， respectively， on the 90th day under the test conditions of ISO 14855?1 and ISO 15985. This indicated that the masks had much better biodegradation performance in aerobic conditions than that in anaerobic conditions. This new type of masks may be more suitable for disposal with aerobic industrial composting devices after discarded.
Wei-Jie /ZHANG
2023, 37 (3):
94-97;
Abstract (
509 )
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42
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The assessment method of the degree of pigment or carbon black dispersion in polyolefin pipes， fittings， and compounds based on the Chinese national standard GB/T 18251—2019 is the current standard method for measuring the dispersion of carbon black in plastic pipes. This paper mainly discusses the thickness range of samples， thickness measurement method， and the sample shape， width， and problems encountered in sample preparation through a slicing method in the process of carbon black dispersion measurement based on this standard. The thickness of the sample was an important parameter for the preparation of samples. The specific measurement method was not given in the current standard and therefore should be supplemented. The microscope measurement method was recommended for use. The thickness range （20±10） μm of carbon black dispersion sample presented in the standard is not suitable. It was found that the thickness of the sample used for the test should be less than 10 μm. The standard does not give the shape and width of the sample prepared by using a slicing method. A square sample with a width of 4 mm was recommended for use. During the slicing process， the sample could be cut to the specified thickness range. This encountered problem could be solved through cutting the sample after low?temperature freezing.
2023, 37 (3):
98-102;
Abstract (
319 )
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41
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A two-color injection mold was designed according to the structural characteristics and production requirements of the two-color key plastic parts. The main body of the plastic part was made of a PC material through one-step injection. In view of the difficulty in the filling of many thin-walled bone positions set on the plastic part structure as well as the problem of excessive injection pressure， a method of fine nozzle multi-point glue injection was adaptable for this mold to address these problems. The secondary injection was conducted using TPE soft glue on the appearance surface of the plastic part. A slider core-pulling mechanism was employed for the optimized design of the three-point fine nozzle to turn the back mold vertically to flip and overlap the bottom to inject glue. This operation was cooperated with the exhaust slot， exhaust needle and exhaust insert structure to solve the problems of the inability to inject glue on the appearance surface and the TPE material being prone to trap air， which led to flow marks， air lines， and bonding lines. The special floating plate structure of the rear mold solved the problem of the isolated island glue feeding of the letter R/e/o/a on the product and the closed middle annular ring. Through actual production verification， the complete filling injection pressure was reduced by 16 % during the first injection， and there were no flow marks， air lines and poor bonding lines found during the second injection. The molding quality of products was satisfactory， and the mold design could meet the requirement of practical production.
2023, 37 (3):
103-112;
Abstract (
521 )
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38
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This paper introduced the methods for regulating the degradation rate of biodegradable polyesters， such as the molecular structural design of polymers， blending modification of polymers， and composite formulation design. The questions and challenges in the regulation of degradation performance of biodegradable polyesters were analyzed， and the future prospect of performance regulation was prospected. It is expected to provide a theoretical basis for the preparation of biodegradable polymers with high performance and time-controllable degradation， and complete degradability.
2023, 37 (3):
113-122;
Abstract (
476 )
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54
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This paper introduced the preparation technologies of conductive polyurethane foams （PUFs） using different conductive fillers， which included carbon black， carbon nanotubes， graphite， metal， organic fillers， etc. summarized the preparation methods of composite foam with different and the effect of these types of conductive fillers on the properties of PUFs was analyzed， and their application in piezoresistive materials， microwave absorbing materials， electromagnetic shielding materials， and electrode materials was discussed. The analysis results indicated that the introduction of conductive fillers improved the anti-static and conductive phenomenon of PUFs and therefore broadened their application range.
