单螺杆挤出过程中固体粒子的变形、取向与熔融Ⅲ固体粒子熔融过程的理论与计算

Deformation,Orientation and Melting of Solid Particle in Single Screw Extrusion Ⅲ. Theory and Calculation of Solid Particle Melting Process

采用带有在线显微观察和摄影系统的全程透明视窗单螺杆挤出机为实验装置 ,在对LDPE物料固体粒子的熔融过程进行实验观察和分析的基础上 ,提出了固体粒子熔融的物理模型和数学模型 ,并对有关模型进行了数学计算。研究结果表明 ,螺槽表层粒子熔融过程不发生熔体迁移的假设与实际情况差异较大 ,而存在熔体迁移的模型与实验现象较为接近 ;而螺槽心层粒子的封闭球壳结构模型与实际情况也存在一定的差异。研究结果进一步指出 ,螺槽心层粒子的熔融前期可以认为不发生熔体迁移 ,但在熔融后期将存在较明显的熔体迁移现象 ;对于固体粒子熔融过程的精确计算既要考虑不同模型的差别 ,还要考虑到粒子形状、粒子运动与变形等因素的影响。

The experiments are carried out on the single screw extruder with online microscopical and photograph systems as well as the transparent glass windows. On the basis of the experimental observations and analysis on the melting process of the LDPE solid particles, the theoretical models for the particulate melting process are proposed and calculated. The comparison of the theoretical predictions with the experimental data shows that the model prediction with melt migaration for the solid particle on the surface of the screw channel is in accordance with the experimental process, that the model prediction without melt migaration for the solid particle on the surface of the screw channel differs from the experimental process, and that core-shell model for the solid particle in the middle of the screw channel has some limitations in its applications. It is reasonable to consider that at the early stage the solid particle in the middle of the screw channel melts without melt migaration, but at the later stage the melt migaration takes place for it. It is necessary that the effects of particulate shape, movement, and deformation should be take into consideration in orde to get the precise model and accurate result.\;