Nonlinear influences of process parameters on mechanical properties of physically foamed, fiber‐reinforced polypropylene parts

Abstract

The importance of foam injection molded components in industrial applications increases, above all driven by sustainability concerns. In practice, their applicability almost exclusively depends on their mechanical behavior, which is still difficult to predict based on their microstructure. This work aims to present an approach based upon phenomenological observations. From a processing perspective, the objective is to describe the direct processing‐properties‐relationship. Therefore, this work focuses on the effects of different processing parameters on selected final mechanical properties of foam injection molded components using glass fiber‐reinforced polypropylene. A full factorial, central composite design allows for the detection of nonlinear effects, the application of response surface methodology, and the creation of contour plots. Considering three important process parameters (mold temperature, degree of foaming, delay time) and—for the automotive industry—highly important mechanical properties in bi‐ and uniaxial bending, the results show a detailed picture of individual dependences, but also two‐dimensional interactions between the different process parameters. Improvements of more than 140% in absorbed energy and flexural stiffness were obtained at constant part weight. Modulus and strength were increased by 37 and 44%, respectively.

High-Performance of a Thick-Walled Polyamide Composite Produced by Microcellular Injection Molding

“…The appropriate fiber orientation, documented in an earlier article [ 22 ] and confirmed by additional SEM and FEM analysis, is also of great importance for the obtained properties. Therefore a slight decrease in mechanical properties was observed, which is in agreement with other researches [ 12 , 14 , 17 ]. It has been shown that the MuCell ® technology enables the manufacturing of thick-walled polyamide moldings with strength properties similar to those of aluminum alloys.…”

“…However, reinforced polyamide material is a popular technical polymer used, among others, in the automotive industry and other important market segments. Unfilled [ 15 , 16 ] or glass fiber reinforced polyolefins [ 17 , 18 , 19 ], as well as PP blends [ 15 ], are usually applied in scientific tests. A wall thickness of examined molded parts with standard and original geometry do not exceed 4 mm in most cases.…”

Microstructure and Properties of Glass Fiber-Reinforced Polyamide/Nylon Microcellular Foamed Composites

“…According to the classical nucleation theory, the increased melt temperature was also beneficial to improve the cell nucleation rate and thus achieve a finer cell structure [ 33 , 34 ]. As shown in Figure 2 c,d, the cell structure was improved when the temperature was increased by 20 °C.…”

The Microcellular Structure of Injection Molded Thick-Walled Parts as Observed by In-Line Monitoring

“…Polymers and Fillers Molded Part Thickness, mm [4,7,8,11,13,16,22,23] PP GF20; PP/LDPE blends; PP + GF + Talc; PP-TPU; PP CF20; PP CF30; PP + EPDM + TALC 2.4-4.0 [6,9,15,17] PA66 GF 30 1.5-4.0 [7,24] PLA/PHBV; PLA/PTFE (fibril) 3.3-4.0 [10,12] PC; PC/ABS 1.7-4.0 [14,25] PS 3.0…”

“…Llewelyn et al presented in their review article the significant development in different aspects of microcellular injection molding [3]. The obtained foamed parts have less weight, improved impact strength, maintained toughness, and insulating properties [3][4][5][6].…”