小麦蛋白质的流变行为及蛋白质塑料的结构与性能

基于作者在对小麦蛋白质溶液动态流变行为、增塑小麦蛋白质等双轴拉伸流变行为、小麦蛋白质塑料制备与性能等研究的最新结果,阐述了pH、温度等对小麦蛋白质溶液动态流变行为的影响;根据Hybrid模型,考察了醇溶蛋白分子的旋转运动、弯曲运动、高频耗散等对流变行为的贡献;分析了形变速度、蛋白质含量、网络形成时间与增塑蛋白质等双轴拉伸流变行为的关系,阐明了分维蛋白质网络的形成机制;探讨了采用热压方法制备小麦蛋白质塑料的工艺参数、交联、化学改性等对微观形态与宏观性能的影响.     

聚甲基乙烯基硅氧烷/炭黑复合体系的电阻弛豫行为

考察了聚甲基乙烯基硅氧烷/炭黑(CB)复合交联体系在恒定压应力作用下以及完全卸载后的导电行为,发现电阻在恒定压应力作用下及完全卸载后均随时间非线性下降,呈现典型的电阻弛豫行为.根据电阻弛豫时间以及最大电阻弛豫幅度,分析了导电网络结构变化与电阻弛豫之间的关联,讨论了炭黑含量对电阻弛豫的影响.结果表明,在恒定压应力2~4MPa下,电阻弛豫具有两个与CB含量无关的弛豫时间,对应不同尺寸导电网络的结构变化.完全卸载后,基体形变回复造成导电网络发生结构弛豫,弛豫时间随CB含量增大而延长.     

加工工艺对炭黑填充聚合物双基体复合材料导电性能的影响

制备了炭黑(CB)填充高密度聚乙烯(HDPE)/乙烯-醋酸乙烯酯共聚物(EVA)双基体复合材料,研究了加料顺序、混合时间对复合材料导电性能的影响.结果表明,CB主要分布在HDPE相中;采用CB首先填充EVA然后与HDPE混合,或采用EVA/HDPE共混物与CB混合的加工策略,均可获得导电性较优的导电复合材料.然而,混合过程显著影响CB填充双基体复合材料的导电性.采用EVA/HDPE共混物与CB混合法加工复合材料,导电性受相形态演化影响较小.     

Novel poly(methyl methacrylate)-based ionomers used as multifunctional aids to modify poly(vinyl chloride)

Poly(methyl methacrylate)(PMMA) based ionomers with different lanthanum(La(Ⅲ)) contents(PMMA-XLa) synthesized by free radical solution polymerization were applied to poly(vinyl chloride)(PVC) resins as a kind of multifunctional aids, and their performances were evaluated by measuring the static stability time, initial discoloration, transparency, fusion behavior and tensile strength of the modified PVC. The ionomers with proper lanthanum(La(Ⅲ)) contents show a better thermal stability efficiency in comparison with traditional stabilizer lanthanum stearate. Meantime, they can accelerate PVC plasticization more efficiently than PMMA. The rigid PVC products stabilized with the ionomers present good transparency and enhanced tensile strength.     

Facile regulation of glutaraldehyde-modified graphene oxide for preparing free-standing papers and nanocomposite films

Colloidal suspensions of glutaraldehyde (GA) crosslinked or grafted graphene oxide (GO) sheets were fabricated by simply tailoring the feed sequence. The different structures were confirmed by Fourier transform infrared spectra and X-ray diffraction. As demonstration of the utilities, the different colloidal suspensions were used to prepare free-standing papers by flow-directed filtration and poly(vinyl alcohol) (PVA)-based nanocomposite films by casting. Free-standing papers from GA crosslinked GO sheets exhibited better mechanical properties than unmodified GO paper, while nanocomposite films from GA grafted GO exhibit higher tensile strength and Young’s modulus.     

Rheological properties of wheat gliadins in aqueous propanol

Rheological properties of wheat gliadins in 50%(V/V) aqueous propanol were carried out as a function of gliadin concentration c and temperature.The solutions at 20 g L 1 to 200 g L 1 behave as Newtonian fluids with an flow activation energy of 23.5 27.3 kJ mol 1.Intrinsic viscosity [η] and Huggins constant k H are determined according to Huggins plot at c ≤ 120 g L 1.The results reveal that gliadins are not spherical shaped and the molecular size tends to increase with temperature due to improved solvation.     

单轴压力对高密度聚乙烯/碳黑导电复合材料电阻特性的影响

研究了高密度聚乙烯/炭黑导电复合材料在单轴压力作用下电阻的变化规律.结果表明,在低压力下,复合材料电阻随压力增加而降低;而在较高压力下则随压力增大而升高,分别呈现出所谓的“电阻负压力系数”和“电阻正压力系数”效应.电阻的压力依赖性以及由压缩引起的电阻不可回复性,被认为与外力作用下导电网络的重组与破坏有关.由此提出了导电复合材料单轴压力作用-电阻相互关系的唯象模型.     

炭黑填充聚甲基乙烯基硅氧烷硫化胶的阻温特性与电阻弛豫

研究了炭黑填充硅橡胶硫化胶的热循环以及热处理过程中的导电行为,发现在热循环中阻温关系曲线逐渐向低电阻方向移动,而在恒温下发生电阻弛豫现象;分析了硫化胶的导电机制,讨论了阻温关系发生移动的原因.     

高斯链网络模型与橡胶交联网络的差异

“橡胶弹性”是《高分子物理》中联系长链分子构象统计和高分子材料力学性能的重要章节之一。现行《高分子物理》教科书中有关内容多以Rehner-Flory“四链模型”为基础,从Gaussian单链熵、单链熵加和恒体积仿射形变角度推导Gaussian链网络构象熵和收缩力,而很少提及Gaussian链网络模型化过程所涉及的诸多近似,更不提及有关学术争议。基于现行《高分子物理》教程,不少学生认为硫化胶具有类似Gaussian链网络的交联结构,不少技术人员基于所谓理想网络结构来设计所谓大应变可逆变形柔性电子等前瞻性器件,在理论和实践上走了不少弯路,得出不少误导性结论。本文回顾Gaussian链网络模型化所涉及的基本理论、近似和争议,以便让读者认识到Gaussian链网络模型仅是具有一系列约束条件的“模型”,而与橡胶交联结构相差甚远。     

Mechanical and thermal properties of nanosized titanium dioxide filled rigid poly(vinyl chloride)

Nano-sized rod-like titanium dioxide (TiO2) filled rigid poly(vinyl chloride) (PVC) nanocomposites were prepared by using injection-molding method. Vicat, Charpy impact and tensile tests as well as thermogravimetric and dynamic mechanical analyses were used to characterize the structure and properties of the nanocomposites. The results showed that nano-TiO2 could improve Vicat softening temperature and also improve thermal stability of PVC during the stages of dehydrochlorination and formation of carbonaceous conjugated polyene sequences, which can be ascribed to restriction of the nanoparticles on the segmental relaxation as being evidenced by raises in glass transition and β-relaxation temperatures of PVC upon filling TiO2. Addition of TiO2 nanoparticles less than 40 phr (parts per hundreds of resin) could significantly improve impact strength of the composites while the TiO2 agglomeration at high contents leads to a reduction in impact toughness.