Poly(L-lactic acid)(PLLA)-based composites exhibit wide applications in many fields.However,most of hydrophilic fillers usually accelerate the hydrolytic degradation of PLLA,which is unfavorable for the prolonging of ...Poly(L-lactic acid)(PLLA)-based composites exhibit wide applications in many fields.However,most of hydrophilic fillers usually accelerate the hydrolytic degradation of PLLA,which is unfavorable for the prolonging of the service life of the articles.In this work,a small quantity of poly(methyl methacrylate)(PMMA)(2 wt%-10 wt%)was incorporated into the PLLA/carbon nanotubes(CNTs)composites.The effects of PMMA content on the dispersion of CNTs as well as the microstructure and hydrolytic degradation behaviors of the composites were systematically investigated.The results showed that PMMA promoted the dispersion of CNTs in the composites.Amorphous PLLA was obtained in all the composites.Largely enhanced hydrolytic degradation resistance was achieved by incorporating PMMA,especially at relatively high PMMA content.Incorporating 10 wt%PMMA led to a dramatic decrease in the hydrolytic degradation rate from 0.19%/h of the PLLA/CNT composite sample to 0.059%/h of the PLLA/PMMA-10/CNT composite sample.The microstructure evolution of the composites was also detected,and the results showed that no crystallization occurred in the PLLA matrix.Further results based on the interfacial tension calculation showed that the enhanced hydrolytic degradation resistance of the PLLA matrix was mainly attributed to the relatively strong interfacial affinity between PMMA and CNTs,which prevented the occurrence of hydrolytic degradation at the interface between PLLA and CNTs.This work provides an alternative method for tailoring the hydrolytic degradation ability of the PLLA-based composites.展开更多
In this work,a series of molybdovanadophosphoric heteropoly acid quaternary ammonium salts H_（3＋x）PMo_（12 -x）V_xO40-T were synthesized and employed as a reaction inhibitor in the selfpolymerization of methyl meth...In this work,a series of molybdovanadophosphoric heteropoly acid quaternary ammonium salts H_（3＋x）PMo_（12 -x）V_xO40-T were synthesized and employed as a reaction inhibitor in the selfpolymerization of methyl methacrylate（MMA）.The polymerization inhibition effect of H_（3＋x）PMoPMo_（12 -x）V_xO40-T）with different number of vanadium atoms and reaction dosages was investigated using differential scanning calorimetry（DSC）.It shows that the inhibitory effect was improved with the increasing dosages of H_（3＋x）PMoPMo_（12 -x）V_xO40-T）,and the polymerization inhibition was also affected by the number of vanadium atoms in the H_（3＋x）PMo_（12 -x）V_xO40-T .Furthermore,cyclic voltammograms（CV）was used to probe the mechanism of the inhibition reaction with H3＋xPMo12xVxO40-T.The result of CV indicates that the inhibition reaction is an oxidation–reduction reaction.H_（3＋x）PMo_（12 -x）V_xO40-T can react directly with the MMA monomer radicals,which eliminated the MMA monomers,and therefore the self-polymerization of the MMA can be effectively inhibited by H_（3＋x）PMo_（12 -x）V_xO40-T.展开更多
We prepared and characterized a form-stable composite phase change material （PCM） with higher thermal conductivity. Capric acid（CA）-myristic acid（MA） eutectic as core, poly-methyl methacrylate （PMMA） as suppor...We prepared and characterized a form-stable composite phase change material （PCM） with higher thermal conductivity. Capric acid（CA）-myristic acid（MA） eutectic as core, poly-methyl methacrylate （PMMA） as supportive matrix and modified graphite （MG） powders serving as the thermal conductance improver were blended by bulk- polymerization method. The composite PCMs with different MG mass fraction （2%, 5%, 7%, 10% and 15%） were characterized by FT-IR, SEM, DSC technique and mechanical tests. Thermal conductivities of the composites were measured by transient hot-wire method. The results indicate that MG powders have been successfully inserted into the CA-MA/PMMA matrix without any chemical reaction with each other. The MG/CA-MA/PMMA composites maintain good thermal storage performance while the thermal conductivity has been enhanced significantly. The composite PCM added with 15 wt% MG powders increases approximately as 195.9% in thermal conductivity. Moreover, the thermal conductivity improvement of the composite PCMs is also verified by the melting-freezing experiment, which is profitable for the heat transfer efficiency in latent heat thermal energy storage system.展开更多
A series of fatty acid/poly methyl methacrylate(PMMA) shape-stabilized phase change materials(PCMs) have been prepared by bulk polymerization method.In the composite,fatty acid(capric acid,stearic acid,and their eutec...A series of fatty acid/poly methyl methacrylate(PMMA) shape-stabilized phase change materials(PCMs) have been prepared by bulk polymerization method.In the composite,fatty acid(capric acid,stearic acid,and their eutectic mixture) acts as core material and PMMA serves as matrix,which coats the fatty acid to prevent the leakage of melted fatty acid.The prepared shape-stabilized PCMs were characterized on the morphology,phase change behavior,chemical characterization and thermal properties.The results indicate that the composites with proper phase change temperature and latent heat are able to keep solid morphology in macro level during thermal storage process.Thermal cycling test also indicates that the composite PCMs have good thermal reliability.Moreover,thermal conductivity and thermal performance are investigated and the results show that the shape-stabilized PCMs have the higher thermal conductivity than fatty acid and exhibited good thermal performance in controlling the atmosphere temperature.展开更多
Soap-free poly（methyl methacrylate-ethyl acrylate-methacrylic acid） latex particles with narrow size distribution were synthesized by seeded emulsion polymerization, and the porous particles were created by a stepwi...Soap-free poly（methyl methacrylate-ethyl acrylate-methacrylic acid） latex particles with narrow size distribution were synthesized by seeded emulsion polymerization, and the porous particles were created by a stepwise alkali/acid treatment method. Effects of acid treatment conditions on the particle morphology were investigated. Results show that one to three pores were formed inside most of particles after post-treatment. At pH 7.0, when the treatment temperature was lower than 70℃, the size of particles and the volume of pores remained almost unchanged, and these two values increased significantly when the temperature was higher than 70℃. Both the particle size and the pore volume decreased with the increase of initial pH value and treatment time in the acid treatment. As the pH was below 4.0 and the treatment time was longer than 180 min, the particles shrunk in size.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 51473137)the International Science and Technology Cooperation Project of Sichuan Province (No. 2017HH0066)+1 种基金the International Science and Technology Cooperation Project of Chengdu (No. 2016-GH0200097-HZ)the Fundamental Research Funds for the Central Universities (2682019JQ04)
文摘Poly(L-lactic acid)(PLLA)-based composites exhibit wide applications in many fields.However,most of hydrophilic fillers usually accelerate the hydrolytic degradation of PLLA,which is unfavorable for the prolonging of the service life of the articles.In this work,a small quantity of poly(methyl methacrylate)(PMMA)(2 wt%-10 wt%)was incorporated into the PLLA/carbon nanotubes(CNTs)composites.The effects of PMMA content on the dispersion of CNTs as well as the microstructure and hydrolytic degradation behaviors of the composites were systematically investigated.The results showed that PMMA promoted the dispersion of CNTs in the composites.Amorphous PLLA was obtained in all the composites.Largely enhanced hydrolytic degradation resistance was achieved by incorporating PMMA,especially at relatively high PMMA content.Incorporating 10 wt%PMMA led to a dramatic decrease in the hydrolytic degradation rate from 0.19%/h of the PLLA/CNT composite sample to 0.059%/h of the PLLA/PMMA-10/CNT composite sample.The microstructure evolution of the composites was also detected,and the results showed that no crystallization occurred in the PLLA matrix.Further results based on the interfacial tension calculation showed that the enhanced hydrolytic degradation resistance of the PLLA matrix was mainly attributed to the relatively strong interfacial affinity between PMMA and CNTs,which prevented the occurrence of hydrolytic degradation at the interface between PLLA and CNTs.This work provides an alternative method for tailoring the hydrolytic degradation ability of the PLLA-based composites.
基金supported by the Research and Development Fund for the postdoctoral researchers of Heilongjiang Province (2012)
文摘In this work,a series of molybdovanadophosphoric heteropoly acid quaternary ammonium salts H_（3＋x）PMo_（12 -x）V_xO40-T were synthesized and employed as a reaction inhibitor in the selfpolymerization of methyl methacrylate（MMA）.The polymerization inhibition effect of H_（3＋x）PMoPMo_（12 -x）V_xO40-T）with different number of vanadium atoms and reaction dosages was investigated using differential scanning calorimetry（DSC）.It shows that the inhibitory effect was improved with the increasing dosages of H_（3＋x）PMoPMo_（12 -x）V_xO40-T）,and the polymerization inhibition was also affected by the number of vanadium atoms in the H_（3＋x）PMo_（12 -x）V_xO40-T .Furthermore,cyclic voltammograms（CV）was used to probe the mechanism of the inhibition reaction with H3＋xPMo12xVxO40-T.The result of CV indicates that the inhibition reaction is an oxidation–reduction reaction.H_（3＋x）PMo_（12 -x）V_xO40-T can react directly with the MMA monomer radicals,which eliminated the MMA monomers,and therefore the self-polymerization of the MMA can be effectively inhibited by H_（3＋x）PMo_（12 -x）V_xO40-T.
基金Founded by the National Mega-Project of Scientific&Technical Supporting Programs during the 11th Five-year Period(No.2006BAJ04A04)the Foundation of Liaoning EducationalCommittee(No.L2012225)
文摘We prepared and characterized a form-stable composite phase change material （PCM） with higher thermal conductivity. Capric acid（CA）-myristic acid（MA） eutectic as core, poly-methyl methacrylate （PMMA） as supportive matrix and modified graphite （MG） powders serving as the thermal conductance improver were blended by bulk- polymerization method. The composite PCMs with different MG mass fraction （2%, 5%, 7%, 10% and 15%） were characterized by FT-IR, SEM, DSC technique and mechanical tests. Thermal conductivities of the composites were measured by transient hot-wire method. The results indicate that MG powders have been successfully inserted into the CA-MA/PMMA matrix without any chemical reaction with each other. The MG/CA-MA/PMMA composites maintain good thermal storage performance while the thermal conductivity has been enhanced significantly. The composite PCM added with 15 wt% MG powders increases approximately as 195.9% in thermal conductivity. Moreover, the thermal conductivity improvement of the composite PCMs is also verified by the melting-freezing experiment, which is profitable for the heat transfer efficiency in latent heat thermal energy storage system.
基金Key Projects in the National Science & Technology Pillar Program during the Eleventh Five-Year Plan Period (No.2006BAJ04A04)Liaoning Scientific Research Program of Colleges and Universities,China (No. 2008S190)
文摘A series of fatty acid/poly methyl methacrylate(PMMA) shape-stabilized phase change materials(PCMs) have been prepared by bulk polymerization method.In the composite,fatty acid(capric acid,stearic acid,and their eutectic mixture) acts as core material and PMMA serves as matrix,which coats the fatty acid to prevent the leakage of melted fatty acid.The prepared shape-stabilized PCMs were characterized on the morphology,phase change behavior,chemical characterization and thermal properties.The results indicate that the composites with proper phase change temperature and latent heat are able to keep solid morphology in macro level during thermal storage process.Thermal cycling test also indicates that the composite PCMs have good thermal reliability.Moreover,thermal conductivity and thermal performance are investigated and the results show that the shape-stabilized PCMs have the higher thermal conductivity than fatty acid and exhibited good thermal performance in controlling the atmosphere temperature.
基金The research was supported by the National 863 Project of China(No.2001AA242041).
文摘Soap-free poly（methyl methacrylate-ethyl acrylate-methacrylic acid） latex particles with narrow size distribution were synthesized by seeded emulsion polymerization, and the porous particles were created by a stepwise alkali/acid treatment method. Effects of acid treatment conditions on the particle morphology were investigated. Results show that one to three pores were formed inside most of particles after post-treatment. At pH 7.0, when the treatment temperature was lower than 70℃, the size of particles and the volume of pores remained almost unchanged, and these two values increased significantly when the temperature was higher than 70℃. Both the particle size and the pore volume decreased with the increase of initial pH value and treatment time in the acid treatment. As the pH was below 4.0 and the treatment time was longer than 180 min, the particles shrunk in size.
