Design of Polymer Additive Solvent Coatings for Enhancing Drying

Abstract

Polymeric coatings are composed of polymeric materials and can be applied to a variety of surfaces by different methods. Polymeric coatings should provide good adhesion to the substrate as well as environmental protection. Residual solvent needs to be minimized since its presence impacts the properties of coatings such as glass transition temperature and causes coating defects. Residual solvent is one of the important factors in polymeric coatings also because the solvents used can be harmful to the environment and consumers. Waterborne coatings are biodegradable, non-inflammable, non-toxic, and show low environmental impact but have issues of high residual solvent along with long preparation time. There is a need to alleviate their drying. Additives enhance the drying properties of the films. A lot of literature is available on the use of plasticizers and surfactants for various purposes. However, there is a dearth of literature on the role of modifiers in enhancing drying of thin polymeric films. In the present work, the coatings were prepared by solution casting method. In the first part of the work, waterborne coatings of PVA-PEG6000-water, PVA-PEG400-water, PVA-FS-water, and PVA-TPP-water systems were considered. For PVA-PEG6000-water coatings, the maximum drop in the residual solvent was 87% at 0.50 wt% PEG6000 loading in the coating of initially 5% PVA and 1000 and#956;m thickness. The effect of doubling the initial wet thickness from 500 and#956;m to 1000 and#956;m was first examined. The minimum residual solvent significantly reduced from 1.30% to 0.59%, and occurred at the same PEG6000 loading of 0.50 wt%. SEM results also revealed that at the optimum PEG6000 loading a smooth and dense coating was obtained. TGA/DTG and DSC studies exhibit thermal stability. Films with good mechanical properties were obtained.