The human touch: Synchronous communication in web-based learning

Moulding composition in particulate form comprising at least one prepolymer containing urethane groups and having the structure R3OOR3 ¦HH PARALLEL PARALLEL HH¦ H2C=C-X-N-R1-NC-O-R2-O-C-N-]n R1 N-X-C=CH2 and hereinafter referred to as the vinyl-ended prepolymer, in which R1 and R2 are each divalent organic groups at least one of which contains at least one cyclic group in the chain and are such that in said structure there are not more than 20 atoms in the chain between each cyclic group, n is a whole number of from 1 to 20, and when n is one and only R2 contains a cyclic group in the chain there are no more than 20 atoms in the chain between the cyclic group in R2 and the nitrogen atom attached to the group X, R3 is hydrogen or a hydrocarbyl group and X is a divalent group are useful in forming articles such as films.