| abstract |
Injection moulded articles consist essentially of polyethylene terephthalate having a crystallinity of at least 25%, the crystals being not more than 5 microns in size and the polyethylene terephthalate having a relative viscosity of at least 1.65 determined at 25 DEG C. in a solution of 1 gram of polyester in 100 grams of m-cresol. The articles preferably contain 0.001 to 0.5% by weight of a solid nucleating agent having a particle size of not more than 2 microns, e.g. titanium dioxide, graphite, carbon black, magnesium oxide, calcium carbonate, calcium sulphate, finely divided copper or antimony, talcum powder, glass powder or antimony trioxide. These nucleating agents may be added during or after the manufacture of the polyester. To improve their crystallinity, the injection moulded articles may be treated with an organic liquid e.g. benzene, toluene, chlorinated hydrocarbons, nitromethane, acetone or lower alcohols. |