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A scheme was developed to cross-link poly(p-phenyleneterephthalamide) (PPTA or Kevlar) in order to modify its macroscopic properties. The method is based on incorporating XTA, a benzocyclobutene-modified derivative of terephthalic acid, into the polymer backbone and then inducing crosslinking by heat treatment after the fiber is formed. PPTA-co-XTA copolymers with various XTA contents exhibited lyotropic nematic liquid crystalline behavior and could be spun into fibers by dry-jet wet spinning techniques. As-spun fibers were heat-treated at intermediate temperatures (200-300 °C) to increase crystallinity and orientation and at higher temperatures (above 320 °C) to trigger cross-linking. Wide angle X-ray diffraction confirmed high molecular orientation in the fibers before and after cross-linking. The mechanical properties of these fibers were studied as a function of XTA content and conditions of heat treatment. Cross-linked copolymer fibers generally showed an improvement in tensile modulus over as-spun fibers. For the PPXTA homopolymer, however, the tensile strength and toughness tended to decrease with increasing length and temperature of the heat treatment. FTIR and ESR spectroscopic studies suggested this resulted from a degradative chain scission process. Compressive properties of these fibers were investigated through elastica and recoil tests, and through measurement of the fiber critical strain to kinking in a beam bending geometry. The strain to induce kinking in cross-linked PPXTA fibers is approximately twice that of the un-cross-linked material. The copolymer fibers also exhibited increased resistance to creep and lateral deformation after heat treatment.

A new thermally reactive monomer has been designed and synthesized that brings novel crosslinking chemistry to high-performance polymers. This monomer (XTA) is a derivative of terephthalic acid and was based on the thermal chemistry of benzocyclobutene. Various model compounds have been synthesized to investigate substituent effects on benzocyclobutene reactivity. Irreversible reaction exotherms around 350°C were observed in these model compounds using differential scanning calorimetry. Based on these studies, polyaramid and poly(aryl ether ketone) XTA copolymers were synthesized. The formation of an insoluble network resulted after heat treatment of these polymers.

The hydroformylation of seed oil based fatty acid methyl esters leads to aldehyde intermediates that can be hydrogenated to give novel seed oil based monomers. In this study, the seed oil based monomers were polymerized with low molecular weight diols to produce novel aliphatic polyester polyols with very low viscosities. The seed oil polyester polyols provide environmentally friendly (green) coating formulations with low volatile organic compound emissions which lead to coatings with superior physical properties, such as exceptional hydrolytic resistance and flexibility. From these polyester polyols, waterborne polyurethane dispersions were also developed with excellent stability resulting in coatings with superior physical properties (i.e., good toughness and abrasion resistance), and exceptional hydrolytic and acid resistance.

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