Incorporation of hydrogen bonding for high performance waerborne coatings.

Abstract

Over the past few decades, with the aim of reducing the VOC emissions and produce more sustainable coatings and adhesives, solventborne products are being replaced by water-based products. However, the mechanical properties of waterborne systems are typically not as good as those of solventborne ones because of differences in the film formation process and this has limited the widespread use of waterborne polymers in some demanding applications that require mechanical strength. Industrially, this issue is often avoided by crosslinking the polymer chains after film formation to achieve mechanical resistance. However, the high reactivity of the functional groups utilized for the chemical crosslinking reactions (e.g. isocyanates, aziridines) often results in limited pot-life of the products and many chemistries are progressively being prohibited because of concerns about their toxicity. In this context, the use of physical interactions like hydrogen bonding to crosslinking the polymer chains arises as a potential alternative to conventional crosslinking chemistries because they avoid the use of toxic chemicals while still creating a network structure.The aim of this PhD thesis is to explore the use of hydrogen bonding for the physical crosslinking of waterborne polymers and the mechanical reinforcement of the films cast from waterborne dispersions. In this thesis, systems with different geometries are designed and compared (e.g. blends of functional particles with complementary H-bonding groups or blends of polymer particles with water-soluble crosslinkers) to understand the effect of the position of the functional groups on the final performance of the materials. In addition, the influence of the nature and strength of the H-bonds on the final properties is analyzed.