Insights on the Molecular Behavior of Polypropylene in the Process of Ultrasonic Injection Molding

Abstract

Product miniaturization is a constant trend in industries that demand ever-smaller products that can be mass produced while maintaining high precision dimensions in the final pieces. Ultrasonic micro injection molding (UMIM) technology has emerged as a polymer processing technique capable of achieving the mass production of polymeric parts with micro-features, while still assuring replicability, repeatability, and high precision, contrary to the capabilities of conventional processing technologies of polymers. In this study, it is shown that the variation of parameters during the UMIM process, such as the amplitude of the ultrasound waves and the processing time, lead to significant modification on the molecular structure of the polymer. The variation of both the amplitude and processing time contribute to chain scission; however, the processing time is a more relevant factor for this effect as it is capable of achieving a greater chain scission in different areas of the same specimen. Further, the presence of polymorphism within the samples produced by UMIM is demonstrated. Similarly to conventional processes, the UMIM technique leads to some degree of chain orientation, despite the fact that it is carried out in a relatively small time and space. The results presented here aim to contribute to the optimization of the use of the UMIM process for the manufacture of polymeric micro parts.

Evaluating the Injection Moulding of Plastic Parts Using In Situ Time-Resolved Small-Angle X-ray Scattering Techniques

“…The sections taken through each SAXS pattern reveal a peak in the scattering, which corresponds to the scattering from the lamellar stacks with amorphous material between the lamellar crystals. The position of the maximum intensity, | Q 0 |, can be converted to the long period Lp using the following equation [ 26 ]. Lp = 2π/| Q 0 | …”

Recent progress in flow‐induced polymer crystallization

“…Consequently, the melt may begin to crystallize during filling due to the enhanced FIC kinetics, thus causing surface replication quality problems. [195][196][197][198] Hou et al 195 recently employed open-mold microcellular injection molding (MOMIM) and talc as a nucleating agent to the surface quality control of parts at the appropriate mold temperature.…”