A new kind of high performance composite resin matrix PEEK/PES, PEEKK/PES block copolymers have been prepared from the corresponding oligomers via a nucleophilic aromatic substitution reaction. The different propertie...A new kind of high performance composite resin matrix PEEK/PES, PEEKK/PES block copolymers have been prepared from the corresponding oligomers via a nucleophilic aromatic substitution reaction. The different properties of the copolymers are investigated by differential scanning calorimetry (d. s. c), thermogravimetric analysis (t. g. a) and dynamic mechanical analysis (d. m. a). The results show that the relationship between Tg and the compositions of the copolymers approximately follows the formula 1/Tg=W1/Tg1 +W2/Tg2 for PEEKK/PES block copolymers, and Tg=Tg1W1 +Tg2W2 for PEEK/PES block copolymers. The PES content and the segment length of the copolymers have a significant influence on their melting point. The thermal properties and dynamic mechanical behaviour of the copolymers are also studied. The introduction of PES segment into the molecular main chain increases the glass transition temperature of poly aryl ether ketones and decreases their melting temperature, that is to say it decreases their melting processing temperature. The block copolymers keep the high temperature stability and solvent resistance of poly aryl ether ketones. They are expected to be a new kind of high performance composite resin matrix.展开更多
For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the inte...For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the interfacial adhesion between wood fiber and matrix. WPCs were prepared from wood fiber up to 60 wt.% and modified PP/PE was blended by extrusion. The rheological properties were studied by using dynamic measurement. According to the strain sweep test, the linear viscoelastic region of composites in the melt was determined. The result showed that the storage modulus was independent of the strain at low strain region （〈0.1%）. The frequency sweep resuits indicated that all composites exhibited shear thinning behavior, and both the storage modulus and complex viscosity of MAH modified composites were decreased comparing to those unmodified. Flexural properties and impact strength of the prepared WPCs were measured according to the relevant standard specifications. The flexural and impact strength of the manufactured composites significantly increased and reached a maximum when MAH dosage was 1.0 wt%, whereas the flexural modulus after an initial decreased, also increased with MAH dosage. The increase in mechanical properties indicated that the presence of anhydride groups enhanced the interracial adhesion between wood fiber and PP/PE blends.展开更多
为了筛选适宜塞外红苹果冷藏的保鲜袋,研究了在0~0.5℃的贮藏条件下,0.01、0.02、0.04mm厚度的PE(聚乙烯,polyethylene)保鲜袋结合1-甲基环丙烯(1-methylcyclopropene,1-MCP)缓释剂处理对果肉硬度、可溶性固形物含量、可滴定酸含量、外...为了筛选适宜塞外红苹果冷藏的保鲜袋,研究了在0~0.5℃的贮藏条件下,0.01、0.02、0.04mm厚度的PE(聚乙烯,polyethylene)保鲜袋结合1-甲基环丙烯(1-methylcyclopropene,1-MCP)缓释剂处理对果肉硬度、可溶性固形物含量、可滴定酸含量、外观及风味以及原果胶含量、可溶性果胶含量、纤维素含量、乙醇含量、乙醛含量、总抗氧化能力、过氧化氢含量等品质指标的影响。结果表明,与CK相比,不同厚度的保鲜袋结合1-MCP缓释剂处理均能有效延缓塞外红果肉硬度、可溶性固形物含量、可滴定酸含量的下降速度,抑制原果胶含量的降低和可溶性果胶含量的升高,延缓乙醇、乙醛高峰的出现时间,维持果实总抗氧化能力在较高的水平。综合比较认为:0.02 mm PE袋+1-MCP缓释剂和0.01 mm PE袋+1-MCP缓释剂2个处理的贮藏保鲜效果相对较好,贮藏120 d及货架5 d期间,能保持果实较好的硬度、外观及风味,有效延缓果实的衰老;0.04 mm PE保鲜袋贮藏的果实果皮出现褐变,而且果肉有异味,不适宜用于塞外红果实冷藏。展开更多
文摘A new kind of high performance composite resin matrix PEEK/PES, PEEKK/PES block copolymers have been prepared from the corresponding oligomers via a nucleophilic aromatic substitution reaction. The different properties of the copolymers are investigated by differential scanning calorimetry (d. s. c), thermogravimetric analysis (t. g. a) and dynamic mechanical analysis (d. m. a). The results show that the relationship between Tg and the compositions of the copolymers approximately follows the formula 1/Tg=W1/Tg1 +W2/Tg2 for PEEKK/PES block copolymers, and Tg=Tg1W1 +Tg2W2 for PEEK/PES block copolymers. The PES content and the segment length of the copolymers have a significant influence on their melting point. The thermal properties and dynamic mechanical behaviour of the copolymers are also studied. The introduction of PES segment into the molecular main chain increases the glass transition temperature of poly aryl ether ketones and decreases their melting temperature, that is to say it decreases their melting processing temperature. The block copolymers keep the high temperature stability and solvent resistance of poly aryl ether ketones. They are expected to be a new kind of high performance composite resin matrix.
文摘For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the interfacial adhesion between wood fiber and matrix. WPCs were prepared from wood fiber up to 60 wt.% and modified PP/PE was blended by extrusion. The rheological properties were studied by using dynamic measurement. According to the strain sweep test, the linear viscoelastic region of composites in the melt was determined. The result showed that the storage modulus was independent of the strain at low strain region （〈0.1%）. The frequency sweep resuits indicated that all composites exhibited shear thinning behavior, and both the storage modulus and complex viscosity of MAH modified composites were decreased comparing to those unmodified. Flexural properties and impact strength of the prepared WPCs were measured according to the relevant standard specifications. The flexural and impact strength of the manufactured composites significantly increased and reached a maximum when MAH dosage was 1.0 wt%, whereas the flexural modulus after an initial decreased, also increased with MAH dosage. The increase in mechanical properties indicated that the presence of anhydride groups enhanced the interracial adhesion between wood fiber and PP/PE blends.
文摘为了筛选适宜塞外红苹果冷藏的保鲜袋,研究了在0~0.5℃的贮藏条件下,0.01、0.02、0.04mm厚度的PE(聚乙烯,polyethylene)保鲜袋结合1-甲基环丙烯(1-methylcyclopropene,1-MCP)缓释剂处理对果肉硬度、可溶性固形物含量、可滴定酸含量、外观及风味以及原果胶含量、可溶性果胶含量、纤维素含量、乙醇含量、乙醛含量、总抗氧化能力、过氧化氢含量等品质指标的影响。结果表明,与CK相比,不同厚度的保鲜袋结合1-MCP缓释剂处理均能有效延缓塞外红果肉硬度、可溶性固形物含量、可滴定酸含量的下降速度,抑制原果胶含量的降低和可溶性果胶含量的升高,延缓乙醇、乙醛高峰的出现时间,维持果实总抗氧化能力在较高的水平。综合比较认为:0.02 mm PE袋+1-MCP缓释剂和0.01 mm PE袋+1-MCP缓释剂2个处理的贮藏保鲜效果相对较好,贮藏120 d及货架5 d期间,能保持果实较好的硬度、外观及风味,有效延缓果实的衰老;0.04 mm PE保鲜袋贮藏的果实果皮出现褐变,而且果肉有异味,不适宜用于塞外红果实冷藏。
