Thermocapillary Effect in a Thermal Rheological Jet

The process of die swell in polymer jets is an important feature within polymer processing and can be explained through a study of its rheological effects. The existence of a thermocapillary effect, driven by the gradient of its surface tension, should be considered when examining a thermal jet that has a non-uniform temperature distribution on its free surface, as in various polymer processings. Both the rheological effect and thermocapillary effect on die swell can be studied numerically through a finite element method as used on a two-dimensional and unsteady model, in which a Coleman-Noll second-order fluid model is employed. The results show that the expanding angle depends on both the rheological property of the fluid and the pressure at the vessel exit. Although both the thermocapillary and the rheological effects contribute to the cross-section expansion of the fluid jet, the latter is more important in determining the expansion.

关于Müller冷度理论的几点注记

<正> 1.引言自六十年代初Coleman-Noll 的开创性工作以来,连续介质热力学蓬勃发展,其中一项重要进展就是冷度(coldness,中译见文,郭仲衡译)概念的引入.西德学者I.Müller 首先提出,人们通常广泛采用(包括Coleman-Noll 的工作)的经典熵流表达式(?)=(?)/T(θ) (1)其中(?)为热流向量,θ为经验温度,T(θ)为绝对温度,可能只适用于热静力学或最简单物质.在热动力学情形,对更一般的介质,熵流(?)应设为待定本构量,因而应当与其他本构函数一样由本构限制(特别是熵不等式)来导出其可能的形式,而没有任何特殊理由先验地

含氯聚合物和乙烯-醋酸乙烯酯共聚物共混体系的红外光谱研究

关于氯化聚乙烯(CPE)或聚氯乙烯(PVC)与乙烯—醋酸乙烯酯共聚物(EVA)共混体系相容性的研究,已有不少报道,其中Coleman等人运用FTIR方法研究了含VA45％的EVA与CPE、PVC的共混体系,测定了该体系的低临界共溶温度(LCST)。一般认为,如果VA含量更低,由于EVA本身的结晶,共混体系将变得难以