Disclosed herein are containers useful for holding fluids, e.g. photographic processing materials, in photographic film units. Such containers have strong seals along certain marginal areas and relatively weak seals along other marginal areas. Such weak seals are designed to open and distribute fluid over a sheet of film or paper when pressure is applied to the container in a camera. Each weak seal is formed from a sealing composition comprising a copolymer of (a) at least about 50 percent, by weight, of a polymerizable monomer having the formula (I): ##STR1## wherein n is an integer of from 0 to 3; R.sup.1 is hydrogen or alkyl; and R.sup.2 is hydrogen, alkyl or phenyl; with (b) a copolymerizable monomer having the formula (II): ##STR2## wherein R.sup.3 is alkyl. This copolymer has a glass transition temperature of at least about 80.degree. C.