THESIS
1995
xi, 70 leaves : ill., photos. ; 30 cm
Abstract
This thesis aims to develop an optimum compaction processing conditions for the preparation of coherent precursors which can be used to produce high performance fibre structures. The low entanglement, ultrahigh molecular weight polyethylene (UHMWPE) "Nascent", reactor powder was processed below its melting temperature (~ 143 ℃). The influence of compaction pressure and processing speed on mechanical and thermal properties as well as chain mobility of precursors were investigated....[
Read more ]
This thesis aims to develop an optimum compaction processing conditions for the preparation of coherent precursors which can be used to produce high performance fibre structures. The low entanglement, ultrahigh molecular weight polyethylene (UHMWPE) "Nascent", reactor powder was processed below its melting temperature (~ 143 ℃). The influence of compaction pressure and processing speed on mechanical and thermal properties as well as chain mobility of precursors were investigated.
For compaction alone samples, it was observed that Young's modulus and toughness were in the range of 3 to 5 GPa and 2.5 to 5 kJ/m[cubed], respectively. Toughness measurements indicated a maximum value when the compaction pressure reaches 30 MPa, the pressure at which the highest chain mobility value was observed using solid state nuclear magnetic resonance (NMR). It was, therefore, concluded that the optimal compaction pressure is as 30 MPa.
A significant increase (~ 50 times) in toughness was observed by the flow of compacted material through a converging die with extrusion draw ratio (EDR) of 2.25. Little change in modulus was found and only a moderate value of orientation function P
2 was observed. Both orientation function measurement from X-ray diffraction technique and morphological results obtained on SEM show that the processing speed has little effect on structure.
Post a Comment