Consolidation of Composites by Using Monoextruded Fibres or Tapes

7 Consolidation of Composites by Using Monoextruded Fibres or Tapes 

While early studies by the group at the University of Leeds focused on melt-spun UHMWPE fibres, the hot compaction process was also subsequently applied to commercial UHMWPE gel-spun fibres [124,125]. It was reported that for some PE fibres, the optimum hot compaction temperature was only 1-2 C less than the temperature at which substantial crystalline melting occurred [117]. At these temperatures, approximately 30% of the oriented fibre content could be lost to melting, and so would be expected to strongly affect the mechanical properties of the final composite. A comparison of the hot compaction of different commercial UHMWPE assemblies, such as fabrics and felts, with commercial UHMWPE laminates was later presented by Morye et al. [126] and Puente Orench et al. [127]. 

Ratner et al. [132] reported the creatirai of UHMWPE composites formed via a similar hot compaction route, and also describe the affect of a chemical crosslinking pretreatment on commercial UHMWPE fibres. This crossUnking treatment was shown to increase the mechanical properties of the final composite constructs and may also enhance interfibrillar bonding. The use of crossUnking to enhance the mechanical properties of hot compacted PE fibres was also reported by Ward and Hine, although in this case, crosslinking was achieved by gamma irradiation in an atmosphere of acetylene [33]. 

Interestingly, Rojanapitayakom et al. reported a change in transparency from relatively transparent at lower compaction temperatures to opaque at higher compaction temperatures, and identified that this optical transparency, combined with high impact strength, could be advantageous in a protective coating application. 

Although deviating slightly from the idea of self-reinforced polymer composites, Hine et al. later reported the incorporatiOTi of carbon nanofibres ( 20% weight) into these PP precursor tapes to enhance the mechanical properties [145], While the expected increase in mechanical properties was observed, the use of maleic anhydride-dispersed carbon nanofibres resulted in an eightfold increase in inteifa-cial strength, as measured by peel resistance, although it is not clear how much of this increase could be attributed to the addition of maleic anhydride or to the carlxMi nanofibres themselves. 

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