[Study on visible-light curing soft resins consisting of fluoropolymers. (3) Application of low molecular weight fluoropolymer].

New experimental visible-light cured soft resins were prepared by combining a low molecular weight vinylidene fluoride/hexafluoropropylene copolymer (2-6 FL), or vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene copolymer (2-4-6 FL) with 2,2,3,3-tetrafluoropropyl alpha-fluoroacrylate (4 FFA), or 2,2,3,3,4,4,5,5-octafluoropentyl alpha-fluoroacrylate (8 FFA). Some properties of the resins prepared were measured to determine whether they would be candidate material for a soft denture liner. Water contact angle was 90-92 degrees with 4 FFA, and 90-94 degrees with 8 FFA. The resins combined with 2-4-6 FL were sufficiently soft: 42-46 (JIS A hardness) in 4 FFA, and 33-39 in 8 FFA. Generally the hardness decreased by 5-10 with the use of a low molecular weight of fluoropolymer. Water sorption after 10 weeks was 0.8-1.2% in 2-6 FL/4 FFA, 1.3-1.7% in 2-6 FL/8 FFA, about 1% in 2-4-6 FL/4 FFA, and about 2% in 2-4-6 FL and 8 FFA. Solubility was 0.4-0.5% in 2-6 FL/4 FFA, 0.3-0.4% in 2-4-6 FL/4 FFA, 1.5-1.9% in 2-6 FL/8 FFA, and 1.1-1.5% in 2-4-6 FL/8 FFA. Amount of residual monomer was very low, and the maximum was 0.1%. Tensile strength of the resins was reduced to 40-70% of that of the similar resins obtained in the previous study. Thus softer resins could be prepared by using lower molecular weight fluoropolymers.