Interlayer Films for Safety Glasses

Poly(vinyl acetal) (PVAL) based formulations are used as interlayer films for laminated glass, as binders for ceramic forming, as binder for ink or paint and as thermally processable photographic materials (36). 

Important issues are improved waterproofness and the compatibility with a plasticizer. For example, when laminate glass is exposed to high humidity for a long time, it may face problems in that water may penetrate into it through its edges and it may whiten as its compatibility with plasticizer is not good. Special formulations have been developed to overcome these drawbacks. 

When the PVAL is used for interlayer films for laminated glass, a plasticizer may be added to it. A preferred plasticizer is triethylene 

The plasticizer may be added from 30-50 parts by weight. If the amount of the plasticizer added is smaller than 20 parts by weight, the interlayer films formed for laminated glass will be too tough and they could not be readily cut. However, if the added amount is larger than 100 parts by weight, the plasticizer may bleed out (36). 

The backbone structure of the PVAL is crucial for the compatibility with the plasticizer. The poly(vinyl alcohol) must contain from 1-3 mol % of 1,2-glycol bond. If the 1,2-glycol bond content of PVAL is too small or too high, then the compatibility of the PVAL type becomes insufficient. 

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Its key characteristics are its excellent optical and adhesive properties. It is used as the interlayer film for safety glass. 

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