Adaptation of the Direct Reaction Injection Molding Process for Production and Processing of Long FiberReinforced Thermosets (LFD-Injection Molding Process) to the use of carbon fibers instead of glass fibers

纤维增强酚醛模塑树脂是最古老的工程聚合物之一，由于其优越的性能而具有非常广泛的用途。除了良好的热机械性能外，它们还具有优异的耐介质性和高尺寸稳定性。它们通常是通过注塑加工的。与热塑性塑料相比，由酚醛模塑化合物制成的部件具有低的断裂伸长率和低的冲击强度。这些不利的材料特性限制了纤维增强酚醛树脂在许多应用中的使用。“LFD注塑成型工艺”项目研究了通过增加成型零件中的纤维长度可以在多大程度上缓解这些缺点。当前项目的范围是找出如何通过使用长碳纤维(LCF)代替长玻璃纤维(LGF)来进一步改善长纤维增强酚醛模塑料的性能。这将通过向注塑过程中可变地喂入低碳纤维来实现。为了实现这一点，需要确定LGF和LCF在纤维的切割、喂入和均化方面的差异。同时，已经建立的玻璃纤维分析方法将适用于碳纤维增强酚醛树脂。在项目范围内，将选择合适的碳纤维和酚醛树脂用于LFD工艺，并通过双螺杆挤出复合成短纤维模塑化合物。借助量热法(DSC)、流变学(振荡流变学)和典型的在线质量保证方法(孔口流动测试OFT)，将确保化合物的可成型性。为了可靠地评估不同材料和工艺参数对纤维长度分布的影响，需要一种有效且可重复性的测量方法。因此，为玻璃纤维开发的测量方法也将适用于并验证碳纤维。该方法基于基质的热解去除，随后是对含水纤维悬浮液的自动图像评估。现有的LFD工艺技术将在尽可能少的变化下适应碳纤维的使用，从而使玻璃和碳纤维的工艺设计具有可比性。碳纤维与酚醛树脂的结合质量将通过评估(不想要的)纤维缩短和(所需)纤维分散的相反效果来表征。为此，将使用纤维长度测量和计算机断层成像评估。最后，该项目的目的是汇总以前工作的结果，并推导出所生产的模塑化合物和组件的工艺-结构-性能关系。

Fiber reinforced phenolic molding resins are among the oldest engineering polymers and are very versatile due to their advantageous properties. In addition to good thermo-mechanical properties, they have excellent media resistance and high dimensional stability. They are typically processed by injection molding. In contrast to thermoplastics, components made from phenolic molding compounds exhibit a low elongation at break and a low impact strength. These disadvantageous material properties restrict the use of fiber-reinforced phenolic resins in numerous applications. The project "LFD injection molding process" investigated the extent to which these disadvantages can be mitigated by increasing the fiber length in the molded part. The scope of the current project is to find out how the property profile of long fiber reinforced phenolic molding compounds can further be improved by using long carbon fibers (LCF) instead of long glass fibers (LGF). This will be realized by a variable feeding of the LCF into the injection molding process. To achieve this, the differences between LGF and LCF in terms of cutting, feeding and homogenization of the fibers are to be determined. In parallel, analysis methods already established for glass fibers will be adapted to carbon fiber-reinforced phenolic resins.Within the scope of the project, suitable carbon fibers and phenolic resins will be selected for the LFD process and compounded to short fiber molding compounds by twin screw extrusion. The moldability of the compounds will be ensured with the aid of calorimetric (DSC), rheological (oscillatory rheology) and typical at-line quality assurance methods (Orifice Flow Test OFT). To reliably evaluate the effects of different material and process parameters on the fiber length distribution, a valid and reproducible measurement method is required. For this reason, a measurement method that was developed for glass fibers will be adapted and validated for carbon fibers as well. The method is based on the pyrolytic removal of the matrix, followed by automated image evaluation of an aqueous fiber suspension. The existing LFD process technology will be adapted to the use of carbon fibers with as little changes as possible , so that the process designs for glass and carbon fibers will be comparable. The incorporation quality of the carbon fibers into the phenolic resin will be characterized by evaluating the opposing effects of (undesired) fiber shortening and (required) fiber dispersion. Fiber length measurements and computer tomographic evaluations will be used for this purpose. Finally, the aim of the project is to draw together the results of the previous work and to derive the process-structure-property relationship for the molding compounds and components produced.