A COMPARISON OF THE HOT-COMPACTION BEHAVIOR OF ORIENTED,HIGH-MODULUS,POLYETHYLENE FIBERS AND TAPES*

The purpose of this article is twofold. First, there is an account of the hot-compaction behavior of a new, highly oriented, high-modulus polyethylene (PE) tape with the trade name of Tensylon® (manufactured by Synthetic Industries, USA). This tape, produced by a melt spinning route, has mechanical properties comparable to those of commercially available gel-spun fibers. Unidirectional samples were produced for a range of compaction temperatures to determine the optimum compaction conditions to obtain the best mechanical properties of the resulting compacted sheets. Second, the mechanical properties of the best Tensylon sample, manufactured at a compaction temperature of 153°C, was compared with three other hot-compacted, highly oriented PE materials, based on Certran®, Dyneema®, and Spectra® commercial PE fibers. The results showed that the optimum compaction temperature was in most cases about 1°C below the point at which substantial crystalline melting occurred. At this optimum temperature, differential scanning calorimetry (DSC) melting studies showed that approximately 30% of the original oriented phase had been lost to bond the structure together. In the case of Dyneema, the properties of the fiber were not translated into the properties of a compacted sheet, and morphological studies showed that this was because melting did not occur on the fiber surfaces, but rather in the interior of the fiber due to a skin structure. The properties of the compacted Tensylon tapes were found to be exceptional, combining very high modulus and strength with interlayer bonding and good creep resistance. Moreover, the optimum temperature appeared to be about 2°C below the point at which complete melting occurred, giving a wider processing window for this material.