a process for production of a monolithic article from a web of fibres of oriented polypropylene homopolymer or copolymer having a weight average molecular weight of at least 250 , 000 includes the steps of subjecting the web to elevated temperature and pressure sufficient to melt a proportion of the polymer and compact it , and thereby yielding an oriented phase and a matrix phase , and effecting a heat treatment selected from subjecting the compacted web to a retarded rate of cooling down to a lower temperature at or below the temperature a which the recrystallisation of the matrix is complete ; and annealing the compacted web at an annealing temperature within 15 ° c . of the temperature at which the matrix phase is completely melted . the resultant articles have good stiffness and strength , and acceptable ductility , yet corresponding articles made with polypropylene of lower m w are brittle .