Applying Digital Image Correlation to perform dilatometry analyses of PTFE during sintering

• Grant number: 24/05869-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: July 01, 2024
• End date: June 30, 2026
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal Investigator: Vinicius Fiocco Sciuti
• Grantee: Taissa de Barros Fregate
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil

Abstract

Polytetrafluoroethylene (PTFE) is a polymer with many applications. Its high viscosity in the molten state prevents the production of parts via traditional routes of thermoplastic polymers, such as injection. Alternatively, the pellets are cold pressed and sintered. The high cost of the raw material motivates studies to simulate the processing steps of PTFE by numerical models. During the sintering stage, dilatometry tests are essential to follow the volume variation caused by thermal expansion, relaxation of residual stresses from the pressing stage, void closure and changes in the degree of crystallinity. However, conventional dilatometry techniques use physical contact and measure expansion/contraction in only one direction per experiment. The use of the Digital Image Correlation (DIC) offers measurement of displacement and deformation fields of the photographed face without physical contact. This scientific initiation project aims to apply DIC to measure the volume variation of PTFE specimens during their sintering. The specimens will be produced in a way that all the volume variation can be attributed to reversible thermal expansion and to the change of crystallinity degree. This is a case of reduced complexity that fits a scientific initiation. The student will learn the entire chain of activities, from the production of specimens to the analyses of the images via DIC. The obtained dilatometry curves will benefit initial finite element models for PTFE sintering.