The synthesis and characterization of hyperbranched polyester （HBP） with different molecular weight are studied. The effect of HBP on the modification of epoxy resins cured with anhydride is mainly discussed. The ch...The synthesis and characterization of hyperbranched polyester （HBP） with different molecular weight are studied. The effect of HBP on the modification of epoxy resins cured with anhydride is mainly discussed. The characteristics of HBP and the morphologies of cured system are determined by nuclear magnetic resonance spectroscopy （NMR）, gel permeation chromatography （GPC） and scanning electron microscope （SEM）. The impact strength of cured system is detected and Fourier transform infrared （FTIR） measurements were used to pursue the curing process. The investigation shows that HBP can improve the toughness by forming copolymer networks between epoxy resins, HBP and anhydride. Moreover, when the molecular weight of HBP is 1342g/mol the toughening effect is the best, and the changes of toughness are small with the increase of molecular weight of HBP to 3500 g/mol.展开更多
An epoxy-terminated hyperbranched aromatic polyester (P3) was synthesized from a hyperbranched aromatic polyester containing carboxylic acid end groups (P1), which was derived from the condensation polymerization of t...An epoxy-terminated hyperbranched aromatic polyester (P3) was synthesized from a hyperbranched aromatic polyester containing carboxylic acid end groups (P1), which was derived from the condensation polymerization of the AB(2) monomer, 5-acetoxyisophthalic acid. Polymer P1 was converted into the polymeric acid chloride by reaction with thionyl chloride. The acid chloride was reacted with ethanol and glycidol to form a poly(ethyl ester) (P2) and an epoxy terminated material (P3), respectively. The reaction conditions in each step of these processes had to be controlled very carefully to avoid unwanted cross-linking reactions. The characterization of products and intermediates, including molecular weight distributions and thermal properties, are reported.展开更多
Bamboo based biocomposites were made with woven bamboo mats and epoxy/unsaturated polyester (UPE) resins. The effects of pre-impregnation on the mechanical and water resistant properties of composites were studied. An...Bamboo based biocomposites were made with woven bamboo mats and epoxy/unsaturated polyester (UPE) resins. The effects of pre-impregnation on the mechanical and water resistant properties of composites were studied. An alkaline treatment was used to enhance the fiber wetting so as to achieve complete pre-impregnation with epoxy and unsaturated polyester resins. A combined treatment of alkali and dilute epoxy/polyester gives the best result. Bending strength, modulus of elasticity, tensile strength, tensile modulus, impact strength, water absorption were evaluated and compared for all composites. Scanning electron microscopy (SEM) studies of the composites tensile fracture surface also indicated that there is an improved adhesion between fiber and matrix. The mechanical as well as water resistant properties of the biocomposites improved after pre-impregnation treatment.展开更多
A new corona protection varnish was prepared by using epoxy/montmorillonite nanocomposite and pure epoxy resin as adhesives respectively.The adhesive with different amounts of organic montmorillonite（OMMT） was mixed...A new corona protection varnish was prepared by using epoxy/montmorillonite nanocomposite and pure epoxy resin as adhesives respectively.The adhesive with different amounts of organic montmorillonite（OMMT） was mixed with 1200 mesh silicon carbide（Si C） by different weight ratios.The surface states of the varnishes with various adhesives were observed by powerful optical microscope.Some properties of the varnishes were analyzed during the enduring time under 5kV/cm DC,such as the relation of change in nonlinear coefficient,natural surface resistivity,and surface temperature variation.The results showed that the amounts of OMMT had little effect on the natural surface resistance of the varnish but had important influence on the nonlinear property of the varnish.When the range of the OMMT content was 2wt% to 6wt%,the nonlinear coefficient of all materials with epoxy/OMMT nano-composite adhesive was higher than that with pure epoxy resin adhesive.The surface temperature of the varnish with epoxy/OMMT nanocomposite adhesive was all lower than that with the pure epoxy resin adhesive under high electrical field strength.展开更多
A liquid crystalline block copolymer (BCPE) was synthesized from bis phenol A epoxy oligomer and liquid crystalline polyester (PBHT) which was prepared from polyhexamethylene bis (4 oxybenzoates) and terephthaloyl dic...A liquid crystalline block copolymer (BCPE) was synthesized from bis phenol A epoxy oligomer and liquid crystalline polyester (PBHT) which was prepared from polyhexamethylene bis (4 oxybenzoates) and terephthaloyl dichloride by solution polymerization.The intrinsic viscosity ( η inh ) of the polymers was determined using an ubbelohde viscometer in phenyl hydroxide/1,1,2,2 tetrachloroethane mix solvent (1:1) at 30℃, and the results showed that the η inh values of PBHT and BCPE are 0.16 dL/g and 0.46 dL/g respectively. FTIR analysis identified the reaction between bis phenol A epoxy oligomer and PBHT. The crystalline properties of polymers were investigated with DSC and WAXD, and the results found that the crystallinity of BCPE is inferior to that of PBHT due to addition of amorphous epoxy. Thermotropic liquid crystalline nematic phase textures of polymers were observed under a polarizing microscope with hot stage.展开更多
文摘The synthesis and characterization of hyperbranched polyester （HBP） with different molecular weight are studied. The effect of HBP on the modification of epoxy resins cured with anhydride is mainly discussed. The characteristics of HBP and the morphologies of cured system are determined by nuclear magnetic resonance spectroscopy （NMR）, gel permeation chromatography （GPC） and scanning electron microscope （SEM）. The impact strength of cured system is detected and Fourier transform infrared （FTIR） measurements were used to pursue the curing process. The investigation shows that HBP can improve the toughness by forming copolymer networks between epoxy resins, HBP and anhydride. Moreover, when the molecular weight of HBP is 1342g/mol the toughening effect is the best, and the changes of toughness are small with the increase of molecular weight of HBP to 3500 g/mol.
基金The project is supported by the EPSRC and the Youth Science Foundation of Shanghai Higher Education.
文摘An epoxy-terminated hyperbranched aromatic polyester (P3) was synthesized from a hyperbranched aromatic polyester containing carboxylic acid end groups (P1), which was derived from the condensation polymerization of the AB(2) monomer, 5-acetoxyisophthalic acid. Polymer P1 was converted into the polymeric acid chloride by reaction with thionyl chloride. The acid chloride was reacted with ethanol and glycidol to form a poly(ethyl ester) (P2) and an epoxy terminated material (P3), respectively. The reaction conditions in each step of these processes had to be controlled very carefully to avoid unwanted cross-linking reactions. The characterization of products and intermediates, including molecular weight distributions and thermal properties, are reported.
文摘Bamboo based biocomposites were made with woven bamboo mats and epoxy/unsaturated polyester (UPE) resins. The effects of pre-impregnation on the mechanical and water resistant properties of composites were studied. An alkaline treatment was used to enhance the fiber wetting so as to achieve complete pre-impregnation with epoxy and unsaturated polyester resins. A combined treatment of alkali and dilute epoxy/polyester gives the best result. Bending strength, modulus of elasticity, tensile strength, tensile modulus, impact strength, water absorption were evaluated and compared for all composites. Scanning electron microscopy (SEM) studies of the composites tensile fracture surface also indicated that there is an improved adhesion between fiber and matrix. The mechanical as well as water resistant properties of the biocomposites improved after pre-impregnation treatment.
基金Funded by the Major State Basic Research Development Program of China(No.2010CB736208)the Planning Project of Hei Longjiang Province for Science and Technology(No.GC10A203)
文摘A new corona protection varnish was prepared by using epoxy/montmorillonite nanocomposite and pure epoxy resin as adhesives respectively.The adhesive with different amounts of organic montmorillonite（OMMT） was mixed with 1200 mesh silicon carbide（Si C） by different weight ratios.The surface states of the varnishes with various adhesives were observed by powerful optical microscope.Some properties of the varnishes were analyzed during the enduring time under 5kV/cm DC,such as the relation of change in nonlinear coefficient,natural surface resistivity,and surface temperature variation.The results showed that the amounts of OMMT had little effect on the natural surface resistance of the varnish but had important influence on the nonlinear property of the varnish.When the range of the OMMT content was 2wt% to 6wt%,the nonlinear coefficient of all materials with epoxy/OMMT nano-composite adhesive was higher than that with pure epoxy resin adhesive.The surface temperature of the varnish with epoxy/OMMT nanocomposite adhesive was all lower than that with the pure epoxy resin adhesive under high electrical field strength.
文摘A liquid crystalline block copolymer (BCPE) was synthesized from bis phenol A epoxy oligomer and liquid crystalline polyester (PBHT) which was prepared from polyhexamethylene bis (4 oxybenzoates) and terephthaloyl dichloride by solution polymerization.The intrinsic viscosity ( η inh ) of the polymers was determined using an ubbelohde viscometer in phenyl hydroxide/1,1,2,2 tetrachloroethane mix solvent (1:1) at 30℃, and the results showed that the η inh values of PBHT and BCPE are 0.16 dL/g and 0.46 dL/g respectively. FTIR analysis identified the reaction between bis phenol A epoxy oligomer and PBHT. The crystalline properties of polymers were investigated with DSC and WAXD, and the results found that the crystallinity of BCPE is inferior to that of PBHT due to addition of amorphous epoxy. Thermotropic liquid crystalline nematic phase textures of polymers were observed under a polarizing microscope with hot stage.
