NUCLEATION PHENOMENA IN POLYMERS.
The effects of nucleating agents on the physical strength properties of selected thermosetting polymer systems were experimentally investigated with emphasis on modified polyamides and specially synthesized ordered epoxy polymers. Nucleating agents such as sodium phenyl phosphinate added in the order of 1 wt. % based on the polymer weight, substantially enhance tensile strength etc. of both Nylon 6 and Nylon 66 polyamides. Morphologically the spherulites formed on cooling from the nucleated polymer melts were very much smaller with overall crystallinities essentially unchanged. With suitable experimental conditions chemical and irradiation crosslinking of such nucleated polymers does not materially lower the level of the strength properties attained by nucleation. The use of glass fiber reinforcements such as, for example, 181 type cloth, not unexpectedly tends to mask the increased strength properties of nucleated crosslinked polyamides. A number of ordered cross linkable epoxy type polymers and copolymers were synthesized using catalyst systems such as ferric chloride propylene oxide complexes and zinc alkyls. Butadiene monoxide containing copolymers have proven of particular interest because of their residual vinyl unsaturation which permits subsequent cross linking via peroxides, irradiation etc. Remarkably high strength properties were obtained with such nucleated and mechanically oriented crosslinked copolymer films etc. These compositions should be further investigated as high strength binders for structural plastic compounds. (Author).
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