Specific bismaleimide compounds are made, and curable compositions are made that include at least one of these bismaleimides and at least one specific polyimide. A process is developed for the manufacture of these curable compositions, and crosslinked polymers are obtainable by this process. A process is developed for the manufacture of a composite material by curing a mixture of a fibrous or particulate reinforcement and the curable composition or the crosslinked polymer as well as the obtained composite material.

There is provided a method for the production of a packaging material comprising a substrate and a gas barrier layer based on polyvinyl alcohol (PVOH), said method comprising the steps of applying a coating composition of said PVOH dissolved in a first solvent onto said substrate to form a coating subjecting the coating to a first drying step to form a dried PVOH-based coating on said substrate, contacting the dried PVOH-based coating with a crosslinking solution comprising a crosslinking agent in a second solvent, to effect crosslinking of the PVOH-based coating, and subsequent to the contact with the crosslinking solution, subjecting the PVOH-based coating to a second drying step, forming the PVOH-based barrier layer on said substrate, with the proviso that if the crosslinking solution comprises PVOH, the amount of PVOH added by the crosslinking solution is less than 20% (by weight), such as less than 10% (by weight), of the amount of PVOH added by the coating composition.