The kinetics of melt grafting acrylic acid （AA） onto linear low density polyethylene （LLDPE） by using reactive extrusion was investigated. The polymeric peroxides （POOP and POOH） generated by electron beam irrad...The kinetics of melt grafting acrylic acid （AA） onto linear low density polyethylene （LLDPE） by using reactive extrusion was investigated. The polymeric peroxides （POOP and POOH） generated by electron beam irradiation were used to initiate the graft reaction. The samples taken out from the barrel at five ports along screw axis were analyzed by FTIR. The spectra show that both the graft copolymerization and homopolymerization proceed in two stages： the graft degree （or mass of homopolymer） increases linearly with the reaction time in the initial stage, and then gradually in the second stage. The rate of graft copolymerization Rg is always faster than that of homopolymerization Rh in the present system and the activation energy is 131 kJ · mol^-1 for graft copolymerization and 127 kJ · mol^-1 for homopolymeirzation. These results were interpreted in terms of solubility and diffusion of monomer, as well as the reactivity and the concentration of reactive species. The relationships between reaction rate and monomer concentration and peroxide concentration were found to be： Rg ∞ [M]^1.46[POOP＋POOH]^0.53 and Rh ∞ [M] ^1.08[POOH]^0.51, which indicate that the addition of monomer to polymeric radicals is a slow step for the graft copolymerization.展开更多
In this study, we present a method to synthesize styrene-butadiene copolymer, using anionic polymerization in a co-rotating closely intermeshing twin-screw extruder. The weight content of polybutadiene in these copoly...In this study, we present a method to synthesize styrene-butadiene copolymer, using anionic polymerization in a co-rotating closely intermeshing twin-screw extruder. The weight content of polybutadiene in these copolymers was above 50% although in the past studies it had been possible to accomplish levels higher than 30%. ^1H-NMR and GPC show that the molecular structure of the two polymers is different due to different feeding method. In terms of the structure of the polymerized products, the mechanism of polymerization in the bulk polymerization is discussed. TEM and DMA show that two phases in the block copolymer are completely incompatible, leading to sharp phase separation, while the case is complicated in the copolymer through the mixture feeding. Traditionally, styrene-butadiene rubber is mainly synthesized by solution polymerization. Reactive extrusion in this paper provides a possibility to synthesize these products in an environmentally friendly way.展开更多
In situ, compatibilization of low density polyethylene (LDPE) (30%) and nylon-6 (70%) blends through one-step reactive extrusion using t-BuOOH as an initiator and low molecular weight interfacial agents as compatibili...In situ, compatibilization of low density polyethylene (LDPE) (30%) and nylon-6 (70%) blends through one-step reactive extrusion using t-BuOOH as an initiator and low molecular weight interfacial agents as compatibilizers was studied. The compatibilizer contained a long chain hydrocarbon, double bond and two polar functional groups which was capable of reacting with both LDPE and nylon-6 in the presence of initiator to form a copolymer at the interface of the two polymer phases. The extruded blends exhibited significant enhancement in their compatibility based on morphological, thermal analysis and mechanical studies. The effect of the hydrocarbon chain length and structure of the functional group of the compatibilizer was also examined. It was found that blends prepared by using the compatibilizer containing longer hydrocarbon chain and amide group had better mechanical properties.展开更多
This paper presents the implementation of two multicriteria optimization methods based on different approaches, namely, Rough Set Method (RSM) and Net Flow Method (NFM), to the manufacture by reactive extrusion of lin...This paper presents the implementation of two multicriteria optimization methods based on different approaches, namely, Rough Set Method (RSM) and Net Flow Method (NFM), to the manufacture by reactive extrusion of linear thermoplastic polyurethanes (TPUs), appropriate for medical applications. A preliminary study allowed determining the process operating conditions for which the polymerization time and the average residence time of the reactants in the extruder are of the same order of magnitude. Prior to the optimization, a neural network model able to predict with acceptable accuracy the effect of the operating conditions on the output process variables, was constructed and validated. This model was then used to determine, using Pareto’s concept, a set of non-dominated solutions constituting Pareto’s domain. These solutions were then ranked according to the preferences of a decision maker using NFM and RSM. This allowed providing the 10% highest ranked solutions of Pareto’s domain and proposing a set of optimal operating conditions for the production, with the lowest energy consumption, of TPUs with targeted properties and high purity. Experimental validation runs carried out under similar operating conditions gave rise to criteria values confirming the su- perior performance of NFM, without rejecting, at the same time, the values obtained using RSM.展开更多
A "reaction-extrusion process" has been developed to prepare Zn4Sb3 bulk materials with high thermoelectric performance.The synthesis,densification,and shape-forming of Zn4Sb3 bulk materials were realized si...A "reaction-extrusion process" has been developed to prepare Zn4Sb3 bulk materials with high thermoelectric performance.The synthesis,densification,and shape-forming of Zn4Sb3 bulk materials were realized simultaneously in one hot-extrusion process,and the resulting extrudates had high density with single β-Zn4Sb3 phase.A large extrusion ratio and a small punch speed are advantageous to enhance thermoelectric performance.The extruded Zn4Sb3 materials exhibited excellent thermoelectric performance,for example,the dimensionless thermoelectric figure of merit is 1.77 at 623 K,which is 36% higher compared to conventional hot-pressed materials.On the other hand,the incorporation of 1% SiC nanosized particles into Zn4Sb3 matrix leads to improvements in both thermoelectric and mechanical properties.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.50390090).
文摘The kinetics of melt grafting acrylic acid （AA） onto linear low density polyethylene （LLDPE） by using reactive extrusion was investigated. The polymeric peroxides （POOP and POOH） generated by electron beam irradiation were used to initiate the graft reaction. The samples taken out from the barrel at five ports along screw axis were analyzed by FTIR. The spectra show that both the graft copolymerization and homopolymerization proceed in two stages： the graft degree （or mass of homopolymer） increases linearly with the reaction time in the initial stage, and then gradually in the second stage. The rate of graft copolymerization Rg is always faster than that of homopolymerization Rh in the present system and the activation energy is 131 kJ · mol^-1 for graft copolymerization and 127 kJ · mol^-1 for homopolymeirzation. These results were interpreted in terms of solubility and diffusion of monomer, as well as the reactivity and the concentration of reactive species. The relationships between reaction rate and monomer concentration and peroxide concentration were found to be： Rg ∞ [M]^1.46[POOP＋POOH]^0.53 and Rh ∞ [M] ^1.08[POOH]^0.51, which indicate that the addition of monomer to polymeric radicals is a slow step for the graft copolymerization.
基金financially supported by the National Natural Science Foundation of China for the Major Program(No.50933002)the National High Technology Research and Development Program of China(863 Program,No.2012AA040306)Shanghai Leading Academic Discipline Project(No.B502)
文摘In this study, we present a method to synthesize styrene-butadiene copolymer, using anionic polymerization in a co-rotating closely intermeshing twin-screw extruder. The weight content of polybutadiene in these copolymers was above 50% although in the past studies it had been possible to accomplish levels higher than 30%. ^1H-NMR and GPC show that the molecular structure of the two polymers is different due to different feeding method. In terms of the structure of the polymerized products, the mechanism of polymerization in the bulk polymerization is discussed. TEM and DMA show that two phases in the block copolymer are completely incompatible, leading to sharp phase separation, while the case is complicated in the copolymer through the mixture feeding. Traditionally, styrene-butadiene rubber is mainly synthesized by solution polymerization. Reactive extrusion in this paper provides a possibility to synthesize these products in an environmentally friendly way.
文摘In situ, compatibilization of low density polyethylene (LDPE) (30%) and nylon-6 (70%) blends through one-step reactive extrusion using t-BuOOH as an initiator and low molecular weight interfacial agents as compatibilizers was studied. The compatibilizer contained a long chain hydrocarbon, double bond and two polar functional groups which was capable of reacting with both LDPE and nylon-6 in the presence of initiator to form a copolymer at the interface of the two polymer phases. The extruded blends exhibited significant enhancement in their compatibility based on morphological, thermal analysis and mechanical studies. The effect of the hydrocarbon chain length and structure of the functional group of the compatibilizer was also examined. It was found that blends prepared by using the compatibilizer containing longer hydrocarbon chain and amide group had better mechanical properties.
文摘This paper presents the implementation of two multicriteria optimization methods based on different approaches, namely, Rough Set Method (RSM) and Net Flow Method (NFM), to the manufacture by reactive extrusion of linear thermoplastic polyurethanes (TPUs), appropriate for medical applications. A preliminary study allowed determining the process operating conditions for which the polymerization time and the average residence time of the reactants in the extruder are of the same order of magnitude. Prior to the optimization, a neural network model able to predict with acceptable accuracy the effect of the operating conditions on the output process variables, was constructed and validated. This model was then used to determine, using Pareto’s concept, a set of non-dominated solutions constituting Pareto’s domain. These solutions were then ranked according to the preferences of a decision maker using NFM and RSM. This allowed providing the 10% highest ranked solutions of Pareto’s domain and proposing a set of optimal operating conditions for the production, with the lowest energy consumption, of TPUs with targeted properties and high purity. Experimental validation runs carried out under similar operating conditions gave rise to criteria values confirming the su- perior performance of NFM, without rejecting, at the same time, the values obtained using RSM.
文摘A "reaction-extrusion process" has been developed to prepare Zn4Sb3 bulk materials with high thermoelectric performance.The synthesis,densification,and shape-forming of Zn4Sb3 bulk materials were realized simultaneously in one hot-extrusion process,and the resulting extrudates had high density with single β-Zn4Sb3 phase.A large extrusion ratio and a small punch speed are advantageous to enhance thermoelectric performance.The extruded Zn4Sb3 materials exhibited excellent thermoelectric performance,for example,the dimensionless thermoelectric figure of merit is 1.77 at 623 K,which is 36% higher compared to conventional hot-pressed materials.On the other hand,the incorporation of 1% SiC nanosized particles into Zn4Sb3 matrix leads to improvements in both thermoelectric and mechanical properties.
