Maertens Robert, Liebig Wilfried V, Weidenmann Kay A, Elsner Peter
Karlsruhe Institute of Technology (KIT), Institute for Applied Materials-Materials Science and Engineering (IAM-WK), Engelbert-Arnold-Str. 4, 73161 Karlsruhe, Germany.
Fraunhofer Institute for Chemical Technology ICT, Joseph-von-Fraunhofer-Str. 7, 76327 Pfinztal, Germany.
Polymers (Basel). 2022 Jul 16;14(14):2890. doi: 10.3390/polym14142890.
Glass fiber-reinforced phenolic resins are well suited to substitute aluminum die-cast materials. They meet the high thermomechanical and chemical demands that are typically found in combustion engine and electric drive train applications. An injection molding process development for further improving their mechanical properties by increasing the glass fiber length in the molded part was conducted. A novel screw mixing element was developed to improve the homogenization of the long fibers in the phenolic resin. The process operation with the mixing element is a balance between the desired mixing action, an undesired preliminary curing of the phenolic resin, and the reduction of the fiber length. The highest mixing energy input leads to a reduction of the initial fiber length = 5000 μm to a weighted average fiber length of = 571 μm in the molded part. This is an improvement over = 285 μm for a short fiber-reinforced resin under comparable processing conditions. The mechanical characterization shows that for the long fiber-reinforced materials, the benefit of the increased homogeneity outweighs the disadvantages of the reduced fiber length. This is evident from the increase in tensile strength from = 21 MPa to = 57 MPa between the lowest and the highest mixing energy input parameter settings.
玻璃纤维增强酚醛树脂非常适合替代铝压铸材料。它们满足了内燃机和电动传动系统应用中常见的高热机械和化学要求。开展了一项注塑工艺开发，通过增加模制部件中的玻璃纤维长度来进一步改善其机械性能。开发了一种新型螺杆混合元件，以改善长纤维在酚醛树脂中的均匀化。使用混合元件的工艺操作是在所需混合作用、酚醛树脂不希望的预固化以及纤维长度减少之间取得平衡。最高的混合能量输入导致模制部件中初始纤维长度L0 = 5000μm减少到加权平均纤维长度Lw = 571μm。这比在可比加工条件下短纤维增强树脂的Lw = 285μm有所改善。力学表征表明，对于长纤维增强材料，均匀性增加的益处超过了纤维长度减少的缺点。这从最低和最高混合能量输入参数设置之间拉伸强度从σt = 21MPa增加到σt = 57MPa中可以明显看出。
