High-speed extrusion

The silk production process must have some built-in temporal, mechanical, and chemical flexibility. This is evident in the ability of the animal to switch from long-duration storage of the proteins (in an aqueous solution state) to high-speed extrusion spinning (into an insoluble fiber with... 

Fridman ML (1970) Rheological properties and high-speed extrusion of polypropylene. Summary of the thesis, INHS, Ac. Sci. USSR, Moscow... 

An examination is made of past and future trends in extrusion tooling. Trends in high speed extrusion, inexpensive tooling, flexible tooling, dual extrusion, flow simulation, bypass rheometry, melt homogenisation, process documentation and customer education. 

A branched macromolecule forms a more compact coil than a linear polymer with the same molecular weight, and the flow properties of the two types can differ significantly in the melt as well as in solution. Controlled introduction of relatively long branches into diene rubbers increases the resistance of such materials to flow under low loads without impairing processability at commercial rates in calenders or extruders. The high-speed extrusion of linear polyethylene is similarly improved by the presence of a few long branches per average molecule. 

Crompton has introduced Mark 2000 organotin stabilisers for PVC window frames, to overcome processing problems in high-speed extrusion lines. The company also markets a sulfur-free tin stabiliser called Mark 2289, specifically for PVC window profiles that are subject to intense simshine, as in desert areas of the United States. It is said to protect against heat and UV to some extent as well. 

The small volume of the HS-SSE also results in short residence times. The mean residence time ranges from approx. 5 to 10 seconds. In conventional SSE the residence times are substantially longer typically between 50 to 100 seconds. Since HS-SSE can run at relatively low melt temperatures, the chance of degradation is actually less in these extruders. There is ample evidence in actual high-speed extrusion operations that the plastic is less susceptible to degradation in these operations. 

P. Rieg, Latest Developments in High-Speed Extrusion, Plastic Extrusion Asia Conference, Bangkok, Thailand, March 17-18, (2008) also presented at Advances in Extrusion Conference, New Orleans, December 9-10 (2008)... 

Note that the low shear rate Mooney viscosity test does not show any advantage, and indeed in this instance suggests the reverse yet in a Mgh-shear high-speed extrusion test through a 2 mm diameter die obvious advantages are apparent for the process aid. 

PO materials look increasingly set to enter some important new markets just as the number of established end-uses has begun to mature. The technologies for the production of high tenacity yarns and the high speed extrusion of relatively fine PP fibres and filaments, as well as nonwoven processes such as melt blowing, create opportunities for further development and exploitation of the many valuable properties of these and related classes of materials [39, 115, 131, 767-777]. 

Applications Clear sheathing, high voltage insulation, optical fibre insulation, telecoms, automotive, high speed extrusion. 

In previous paper [8], we reported that a small amount of PP could obviously decrease the orientation of ethylene butene copolymer (EBM) in melt spinning. In this study, the phase morphology development of PP/EBM blends in extrusion and melt spinning is studied. The dispersed PP droplets were also found to form encapsulation layer in both high speed extrusion and melt spinning. The encapsulation phase morphology was found to affect the birefringence of the blends. 

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