Presenters Name:James Manikath
Employment Title: Technical Manager
Company: Luxury Paints, Darra, QLD
Biography: James is responsible for over all technical management and compliance at Luxury Paints, Queensland. Has extensive experience in industrial and academic research. He has worked at Nuplex Industries, PPG and Wattyl gaining formulation experience in polymer latexes and coatings. Before that he was a Research Fellow in School of Engineering at the University of Auckland.
Presentation Title: Stress Relaxation of Polymers and Its Impact on Paints and Coatings
Presentation Abstract: While developing a quick-drying paint with an excellent finish, mud cracks were observed after 24 hours or later. To address this issue, various polymers and blends were tested. However, softer polymers delayed the hardening process and caused blocking. In this context, I reviewed the research I conducted at the University of Auckland, School of Engineering, on stress relaxation in polymers used in plastic composites. Stress relaxation refers to the gradual decrease in internal stress within a material under constant strain. During the research, I found that incorporating wood fibres at various loading levels lowered the relaxation level. The fibres helped restrict stress relaxation and provided stability to the shape of the plastic object under load. Inspired by this, I used fibrous materials, including fibrous rheology modifiers, to address the mud cracking defect. This approach effectively resolved the issue. As a paint or coating dries and cures, the polymer chains transition from a liquid to a solid state. This process involves significant shrinkage, which can induce internal stresses within the film. Stress relaxation allows the polymer chains to rearrange, reducing these internal stresses. Various factors affecting the stress relaxation of coatings have been examined. The related property, known as creep in polymers, used in coatings, has also been reviewed, and valuable insights were gained. Stress relaxation is a crucial factor in the performance of paints and coatings. Understanding this phenomenon aids the development of defect free coatings with enhanced properties such as flexibility, durability, and adhesion. Stress relaxation and creep are often overlooked polymer properties. A deeper understanding of these phenomena can provide coating formulators with valuable insights to make informed decisions about polymer selection.
