Permanent melt-spinning

Elongational behavior is induced in the entrance of the spinning hole and in the transition region from backhole to actual capillary. In practice hardly any permanent orientation is built up in this way, however, because molecular relaxation is rapid. Spinning hole profiles are smoothened only to prevent the formation of vortices which would lead to extrudate distortion. Promoting orientation already in the spinning holes is not common for melt spinning. It could be beneficial for the orientation of melt-spun liquid-crystalline polymers, however, for example in the production of carbon fiber from pitch. 

The shape memory mechanism of the SMF can be illustrated as follows during melt spinning, at a temperature which is higher than T (222°C in the given ejqieriment), the fiber is extruded from a spinneret. Upon cooling to an ambient temperature, which is below T, the fiber is wound up and the permanent fiber shape is cast. 

PP/silver nanocomposite fibres were prepared with the aim of achieving permanent antibacterial activity in a common synthetic textile. The fibres were melt-spun by coextmsion of PP and PP/silver masteibatches using general conjugate spinning. Masteibatches were made up of a mixture of PP chips and nano-sized silver powder. The antibacterial efficacy of spun fibres was high when the masteibatch was used as the sheath rather than the core. The antibacterial activity of nano-silver in fibres was evaluated after a certain contact time and calculated by percent reduction of two types of bacteria. Staphylococcus aureus and Klebsiela pneumoniae. DSC and wide-angle X-ray diffraction were used for analysis of stractuie, thermal properties and crystallisation behaviour of the spun fibres. SEM was carried out in order to observe particle distribution on the nanocomposite fibres. 17 refs. (2nd International Conference on Polymer Fibres, Manchester, UK, July 2002)... 

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