Synthesis and characterization of water-thinnable thermosetting acrylic resins for low-cure surface coatings

摘要

Among the various binders used for industrial finishes,thermosetting acrylics (TSAs) are gaining importance.There are two main reasons for this;firstly they possess inherently superior properties;such as water clear appearance,colour retention,good durability,low pigment reactivity,excellent chemical resistance and excellent flexibility.Secondly,thermosetting acrylics provide greater formulation latitude as they can be tailor made to suit specific applications.Presently,thermosetting acrjdics are commonly used in the two major forms:(a) Solvent soluble thermosetting acrylics for conventional solids coatings.(b) Thermosetting acrylics for high solids coatings.In the present work,water-thinnable acrylic resins have been developed wherein water is used in place of volatile organic solvent which is the main source of VOC emission.Water-thinnable thermosetting acrylics are getting more prominence day after day because of their eco-friendly nature,cost effectiveness and superior films performance.However,ordinary water-thinnable thermosetting acrylic resins cure at high temperature (approx=120-150°C) and hence involve high energy consumption.Through this work,efforts have also been directed towards developing such water-thinnable thermosetting acrylic resins which can be cured at lower temperature to yield low-cure surface coatings.For achieving this,a series of TSAresins were prepared by reacting 2-hydroxy ethyl methacrylate (HEMAj and acrylic acid (AA) as monomers in butanol as solvent in presence of benzoyl peroxide as initiator.The prepared TSA resins were made water soluble by neutralizing with ammonia solution.The coating films were then baked at 90°C for 30 minutes to effect film cure.Cured films were evaluated for their various optical,mechanical and chemical resistance properties to ascertain the commercial utility of low-temperature curable water-thinnable TSA resins.