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Monday, 23 September 2019
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Raw materials & technologies, Applications

Degradability of polyurethane refinish coatings against biological materials

Monday, 22 February 2016

In a study the effect of bird droppings and tree gums on two different polyurethane refinish coatings has been investigated.

The biological resistance of two polyurethane refinish coatings were investigated. Source: Gordon Bussiek/Fotolia.com

The biological resistance of two polyurethane refinish coatings were investigated. Source: Gordon Bussiek/Fotolia.com

To this end, Arabic gum and pancreatin were used as simulated tree gum and bird dropping, respectively. These substances were applied on coatings exposed to UV radiation and moisture for different exposure times.

Studying the appearance of the coatings

Various techniques were used to study the appearance of the degraded coatings. Structural analysis of samples was done by FTIR spectroscopy. Surface free energy and thermo mechanical characteristics of refinish coatings were studied by contact angle measurement and DMTA respectively. All experiments were carried out before and after degradation process.

Arabic gum causes wrinkle-like damages on clearcoats

In general, it was revealed that while pancreatin degraded the coatings chemically, Arabic gum affected it mechanically and chemically, leading to wrinkle-like deformations on the coating surface. It was also concluded that the cross-linking density and surface free energy have vital roles in the degradation of automotive refinish coatings. It was demonstrated that low cross-linking density and Tg of polyurethane system created a dynamic system which can be post-cured during experiment, leading to enhanced biological resistance.

According to this finding, it was also revealed that coating history before bio attack is an important factor in the biological performance of polyurethane systems.

The study is published in: Progress in Organic Coatings, Volume 93, April 2016, Pages 1-10.

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