DETERMINATION OF THE QUANTITY OF RESIDUAL DOUBLE BONDS IN DENTAL POLYMERS

摘要

A series of 20 experimental monomers mixtures of different compositions has been prepared from the aromatic (Bis-GMA)_(0-2) superior oligomers, (modified Bis-GMA)_(0-2) superior oligomers, Bis-DMA monomer and the diluting aliphatic monomers, triethyleneglicol dimethacrylate (TEGDMA), mono-ethyleneglicol dimethacrylate (EGDMA) and respectively, hidroxyethyl methacrylate (HEMA). The monomers mixtures have been used to obtain copolymers by chemical, respectively by photochemical initiation of polymerization. The copolymers have been investigated by IR spectroscopy method in order to evaluate the quantity of the residual double bonds (RDB). The quantity of unreacted methacrylate groups has been determined in percents of the methacrylate groups originally present in the unpolymerized material. The RDB ranged between 23 % for the light cured copolymer originating from the monomer mixture containing 30% (Bis-GMA)_(0-2) and 70% TEGDMA, and 45 % for the polymer originating from (Bis-GMA)_(0-2) oligomers. The obtained results pointed out as a general conclusion, the obtaining of a smaller quantity of residual double bonds in the case of light cured copolymers than in the case of chemical cured materials, as well as the increasing of RDB with the increasing of the aromatic oligomers amount in the mixture.