This invention relates to plastic containers hermetically sealed with a peelably heat-sealable plastic film comprised of a polymeric mixture comprised of 1-99 parts by weight (pbw) of an impact-resistant polystyrene resin and 99-1 pbw of a copolymer consisting essentially of:p1) 20-90 weight % methyl methacrylate, ethyl methacrylate or a mixture thereof;p2) 10-80 weight % of at least one monomer of formula (I): ##STR1## and where R.sub.1 represents an alkyl group with 3-24 C atoms; andp3) 0-10 weight %, preferably 1-8 weight %, of a monomer which is copolymerizable with and different from the monomers (p1) and (p2).