Nucleation and orientation of linear polymers

Abstract

Abstract Additions of small amounts of fine particle size specialized monoclinic inorganic crystals to otherwise relatively pure polyalkylene terephthalate molding compounds increases the rate and extent of crystallization and the specific gravity of the polyalkylene terephthalate molded part. Both low and high molecular weight polyalkylene terephthalates are improved with regard to physical properties and dimensional stability through addition of these small quantities of these specialized monoclinic materials. Under controlled conditions of injection and forming, anisotropic properties may be obtained as a consequence of the effect and extent of the crystallization of the polyalkylene terephthalates which has been promoted by these strongly active nucleating agents. In addition to the improvement of the physical properties of the molded article, the use of these specialized nucleating agents in suitable particle size yields a significant shortening of the retention time of the injection molded material in the mold, this being an item of economic significance. An important aspect of the invention is the added capability of polyalkylene terephthalate crystal orientation by controlled application of magnetic forces to these nucleated compositions, and particularly (a) when such nucleating agents are ferromagnetic in themselves and (b) whether ferromagnetic or not, the preferred nucleating agents are more forcibly aligned into a desired direction (thus promoting crystallization of the polyalkylene terephthalate also in the desired direction) by the action of magnetic fields of force applied to the composition in the molding cycle in the presence of sweeping agents of fibrous and/or acicular nature taken from the class of non-metallic and/or metallic ferromagnetic materials. Not only are the specialized monoclinic nucleating agents useful for promoting crystallization of polyalkylene terephthalates when such nucleating agents are useful in small percentage, but in much larger percentages they can be used as mineral fillers to yield high strength, dimensionally stable, clean surface parts obtained with a molding cycle time of short duration.

Inventors

• 👤 Eugene Wainer

Bibliographic Details