Coating of polymethylmethacrylate with transparent SiO2 thin films by a sol-gel method
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In order to improve the surface characteristics of polymethylmethacrylate (PMMA), oxide thin-film coatings were applied using the sol-gel dip-coating technique. The Si(OC2H5)4 (TEOS), CH3Si(OC2H5)3 (MTES) or Ti(O-i-C3H7)4 (TIP) was used as a starting material for SiO2 or TiO2 coating. The hardness of the alkoxy-derived oxide-coated PMMA was increased from 200 MPa for non-coated PMMA with increasing film thickness. By optimizing the heating conditions and the hydrolysis conditions, and by repeating the dip-coating/heating processes, a hardness as high as 325 MPa was achieved in the PMMA triply coated with the TEOS-derived SiO2 film using the withdrawal velocity of 0.30 mms−1 and heat treatment at 80°C. The increase in hardness with the thickness of coating film was saturated before reaching that of bulk silica-dried gel (ca. 500 MPa), which may be due to the increased porous nature of the thick films.
KeywordsTiO2 SiO2 PMMA Polymethylmethacrylate Coating Film
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