POLYACETALS. I.E. HOMOPOLYMERS OF FORMALDEHYDE OR OF TRIOXANE OR COPOLYMERS OF TRIOXANE WITH MONOFUNCTIONALLY REACTING COMPOUNDS SUCH AS CYCLIC ETHERS OR CYCLIC ACETALS AND POSSIBLY POLYFUNCTIONALLY REACTING COMPOUNDS CAN BE PROTECTED BY ADDITION OF STABILIZERS AGAINST THE ACTION OF HEAT AND OXYGEN. THEY CAN, HOWEVER, BE DEGRADED BY THE ACTION OF ULTRA-VIOLET LIGHT IF THEY CONTAIN LIGHT SENSITIZERS, FOR EXAMPLE ANTHRONE. THE POLYACETALS ARE SUITABLE FOR THE MANUFACTURE OF SHAPED ARTICLES, ESPECIALLY SHEETS.