Process Variability Effects on Tensile Response in Injection Molded, Fluorinated Thermoplastics

Technical Report · Mon Sep 25 04:00:00 EDT 2023

DOI:https://doi.org/10.2172/2386905· OSTI ID:2386905

Wilcox, Douglas R. ^[1]; Shepherd, Rebekah ^[1]; Brown, Geoffrey W. ^[2]; McCollum, Jena M. ^[1]

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1. Univ. of Colorado, Colorado Springs, CO (United States)
2. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

The mechanical properties of fluorinated thermoplastics (i.e., tensile strength and elongation) can vary with changes in injection molding processing parameters. Four fluoropolymers are examined: poly(vinylidene fluoride) (PVDF) and random poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) with three CTFE concentrations. Dog bones were manufactured with various cylinder dwell times and mold cooling times to assess the manufacturing sensitivity to the tensile response. Dwell and cooling times increasingly impact mechanical performance as CTFE concentration increases. Specimens exhibit higher tensile strength as a function of injection order. The first injected specimen exhibits the lowest tensile strength and highest elongation in all copolymers. This trend becomes more pronounced among fluoropolymers with higher CTFE concentration and lower weight-averaged molecular weight. Parallel plate rheology was used to obtain the zero-shear viscosity as a function of material type, process, and injection order. We found that in the copolymers, the first injected sample exhibited a lower zero-shear viscosity than the next, which indicates a lower molecular weight in the first injected specimen. This phenomenon was not present for the PVDF homopolymer. Copolymer mechanical uncertainties are hypothesized to result from the shorter molecular weight chains extruding out of the specimens’ sides as a flash due to higher mobility with CTFE segments.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• DOE Contract Number: 89233218CNA000001
• OSTI ID: 2386905
• Report Number(s): LA-UR--23-23303
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
copolymers
mechanical properties
molding
structure-property relationships manufacturing
thermoplastics