Prediction of the morphology of heterogeneous plastic blends during single-screw extrusion

热塑性塑料有多种加工方法。这种潜力是由于它们的加工温度低，易于修改，以实现特定应用的性能，例如，通过添加添加剂或功能成分来产生共混物。在塑料的复合和加工中，均匀性，即塑料熔体中各组分的混合，是产品质量最重要的标准。分布和分散混合工艺可用于均匀化熔融状态下的聚合物共混物。为此，在复合和加工过程中，使用单螺杆和双螺杆挤出机可以使用各种各样的混合元件，可以控制混合效率。一个主要的挑战是这些混合几何形状的正确设计和相关工艺设置的选择，这最终对产品质量产生重大影响。对于混合几何形状和相关工艺设置的设计和改进，塑料熔体的数值模拟提供了显着减少这些设计步骤。然而，为此目的，必须模拟非混相塑料共混物均匀化所需的伸长率和剪切变形，以便能够指定动态混合器的设计标准和工艺设置。这就是研究项目的由来，通过捆绑和扩展申请人研究单位的专业知识，预测异质塑料混合物的混合效率。目的是开发一个通用模型，将分散混合描述为破碎和聚结过程的函数，同时考虑到不同类型变形和粘合促进剂的强度。该模型还应考虑非牛顿粘性流动特性。为此，必须首先开展基础研究，以便对塑料熔体中液滴作为不同类型变形的函数的行为有更深入的了解。一个特殊的库埃特流变仪将被构建和各种几何研究，以诱导不同的流场，从而在塑料熔体不同的变形。基于这些结果，该模型将被开发并应用于实际的塑料加工操作中，其中单螺杆挤出机的混合区进行了模拟。

Thermoplastics are processed in a wide range of converting methods. This potential is due to their low processing temperatures and their easy modifiability to achieve application-specific properties, e.g. by adding additives or functional components to generate blends. In plastics compounding and processing, homogeneity, i.e. the mixing of the components in the plastic melt, is the most important criterion for product quality. Distributive and dispersive mixing processes can be used to homogenize the polymer blends in the molten state. For this purpose, a wide variety of mixing elements are avail-able during compounding and processing by using single- and twin-screw extruders, which can con-trol the mixing efficiency. A major challenge is both the correct design of these mixing geometries and the selection of the as-sociated process settings, which in the end have a significant influence on product quality. For the design and improvement of the mixing geometries and the associated process settings, the numeri-cal simulation of plastic melts offers to significantly reduce these design steps. For this purpose, however, the elongation and shear deformations required for the homogenization of immiscible plas-tic blends must be simulated in order to be able to specify design criteria and process settings for dynamic mixers. This is where the research project comes in, by bundling and extending the know-how of the appli-cant's research unit for predicting the mixing efficiency of heterogeneous plastic blends. The aim is to develop a general model that describes dispersive mixing as a function of break-up and coalescence processes, taking into account the intensity of different types of deformation and adhesion promot-ers. This model should also take into account non-Newtonian viscous flow behavior. To this end, basic research must first be developed in order to obtain an advanced understanding of the droplet behavior in a plastic melt as a function of different types of deformation. A special Couette rheometer is to be constructed and various geometries investigated that induce different flow fields and thus different deformations in a plastic melt. Based on these results, the model will be developed and ap-plied and validated for realistic plastics processing operations in which the mixing zone of a single-screw extruder is simulated.