Study On The Preparation And Properties Of Polyurethane Coatings For Protection Of PMMA

PMMA is a kind of engineering plastics with excellent comprehensive performance, which is widely used in the field of high-end industrial products, aerospace, defense and other strategic. But because of the low surface hardness, it is easy to produce scratches and cracks in the using process. And under the complex environmental conditions (UV irradiation, high and low temperature and so on), it is prone to aging and deformation, which seriously restricts its service life and safety.Based on the demand of PMMA surface protection material which desired high transparency, high strength, good weather resistance and so on, a series of transparent polyurethane (PU) resin and coating materials were prepared from aliphatic diisocyanate (HMDI) and polyether polyol (PTMG1000, EP3600) by two step method. Through the relevant testing instrument, a series of tests were carried out on the PU elastomers and the coatings. The effects of raw materials and formulation parameters on the optical properties and mechanical properties of PU resin, as well as the effects of PU coatings on the water resistance, solvent resistance, wear resistance, UV resistance and other environmental tolerance properties of PMMA were studied. From analysis the following conclusions could be made.(1) Based on the research that effect of the raw materials on the optical properties and mechanical properties of the PU elastomers, isocyanates, chain extenders, polyether polyols, the relative molecular weight of polyol soft segment,-NCO cotents of pre polymers and the hard segment content of PU resin, which meeted the requirements of coating materials for PMMA surface protection, were selected. It showed that when using HMDI, PTMEG1000, EP3600 and TMP/BDO as the raw materials,the -NCO content was 8.0%, and the hard segment content was 39.83%, PU elastomers had the following properties:the transmittance was 92.4%, the haze was 0.32%, the hardness was 94 Shore A, tensile strength was 29.27MPa, elongation at break was 350%, and permanent deformation rate was 2.7%. The properties above could meet the performance requirements of high strength and high transparency.(2) According to the best formulation of PU resin, a series of transparent PU coatings were gained by adding solvents and other related additives. Through a variety of related test instrument, many properties of PU/PMMA and PMMA were tested, such as optical properties, surface morphology, water resistance, resistance to solvent, abrasion resistance, resistance to ultraviolet aging etc. The results showed that PU coating had good wear resistance, yellowing resistance and so on. With no effect on the basic performance of the PMMA samples, PU coatings significantly increased the environment tolerance performance of the PMMA. It not only achieved the purpose of surface protection for PMMA, but also laid a good foundation for further research.