polytetrafluoroethylene polyvinylidene fluoride or a copolymer of tetrafluoroethylene with perfluoroalkyl vinyl ether hexafluoropropylene ethylene or trifluorochloroethylene application_number US 41032482 A description first stretched porous resin fragments or particles are prepared from stretched porous polypropylene resin stretched porous polyethylene resin stretched porous polytetrafluoroethylene resin etc in the case where stretched porous polytetrafluoroethylene resin is used for the stretched porous resin fragments stretched porous polytetrafluoroethylene resin fiber or film is prepared according to the process as disclosed in u s pat no 3 953 566 the fiber thus prepared is cut into 0 5 to 20 mm chips and from the film thus prepared circular fragments 0 5 to 50 mm in diameter are punched or the film is cut into triangular rectangular or polygonal fragments having a side of 0 5 to 5 mm stretched porous resin fragments thus prepared are mixed into a resin matrix in an amount of 3 to 80 by volume to prepare reinforced plastics this mixing is accomplished as follows in the case where the resin matrix is polytetrafluoroethylene resin or tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin the proper quantity of stretched porous resin fragments made of polytetrafluoroethylene resin is mixed into a dispersion of polytetrafluoroethylene resin and the mixture is stirred by a coagulator or mixer so that the stretched porous resin fragments coagulate in the secondary particles of polytetrafluoroethylene resin this coagulated mixture is incorporated with a liquid adjuvant in an amount from 10 to 200 by weight to prepare a pasty mixture the liquid adjuvant includes hydrocarbon oils such as solvent naphtha and white oil aromatic hydrocarbon oils such as toluene and xylene alcohols ketones esters silicone oil fluorocarbon oil surface active agent or mixtures thereof or mixtures composed mainly thereof the pasty mixture thus prepared is formed.