Compounding of Short Fiber Reinforced Phenolic Resin by Using Specific Mechanical Energy Input as a Process Control Parameter

Abstract

For a newly developed thermoset injection molding process, glass fiber-reinforced phenolic molding compounds with fiber contents between 0 wt% and 60 wt% were compounded. To achieve a comparable remaining heat of the reaction in all compound formulations, the specific mechanical energy input (SME) during the twin-screw extruder compounding process was used as a control parameter. By adjusting the extruder screw speed and the material throughput, a constant SME into the resin was targeted. Validation measurements using differential scanning calorimetry showed that the remaining heat of the reaction was higher for the molding compounds with low glass fiber contents. It was concluded that the SME was not the only influencing factor on the resin crosslinking progress during the compounding. The material temperature and the residence time changed with the screw speed and throughput, and most likely influenced the curing. However, the SME was one of the major influence factors, and can serve as an at-line control parameter for reactive compounding processes. The mechanical characterization of the test specimens revealed a linear improvement in tensile strength up to a fiber content of 40–50 wt%. The unnotched Charpy impact strength at a 0° orientation reached a plateau at fiber fractions of approximately 45 wt%.

Development of an Injection Molding Process for Long Glass Fiber-Reinforced Phenolic Resins

“…After leaving the extruder, the compound was cooled and granulated by using a cutting mill (Hosokawa Alpine, Augsburg, Germany). The method for controlling the energy input into the phenolic resin during the compounding, which was developed by the authors, is described in detail in the publication [ 56 ]. In publication [ 56 ], the detailed screw layout and the barrel temperature profile are presented.…”

“…The method for controlling the energy input into the phenolic resin during the compounding, which was developed by the authors, is described in detail in the publication [ 56 ]. In publication [ 56 ], the detailed screw layout and the barrel temperature profile are presented. For the LGF, the direct roving 111AX11 with a filament diameter of by 3B Fibreglass was used.…”

“…The results themselves are not published yet. The publication [ 56 ] describes the process development for the twin screw extruder compounding of the short glass fiber-reinforced phenolic molding compounds. The compounds that were manufactured according to this method constitute the basis for the new experimental investigations and process data analyses that are presented here.…”

Experimental Investigation of the Uncertainty of Disordered Fiber-Reinforced Injection-Molded Components

“…In addition, scattering of the fiber length occurs because the fibers break during the process, which also affects the component properties [6]. In [1], a fiber volume dependence of the fiber length was also observed. With a higher fiber volume content, the fibers are shorter on average.…”

“…As a result, the components possess a scatter in their mechanical properties due to the local scatter in fiber length, fiber orientation and fiber volume content. In this paper, we investigate the scatter of mechanical properties and fiber orientation of a glass fiber-reinforced phenolic resin with a fiber mass content of 37.5 wt% manufactured by a thermoset injection molding process [1]. Rectangular plates of 2 and 3 mm thickness and a size of 190 x 480 mm² were manufactured.…”