Presentation to Dow Chemicals in Horgen

S F Bush, UMIST

Introduction: Work on Control of Fibre Structures

1. Rotating die extrusion of tubes with GF, in PP, PP and EDPM, PP and HDPE, HDPE.
2. Static die extrusion of sheet with PP and GF.
3. Theory of fibre orientation in changing flow fields.

Some Key Results and Concepts

1. Rate of orientation of fibres depends on lengths.
2. Criticial length/concentration gives semi-stable mat structures.
3. Cold-forming die always induces some loss of orientation.
4. Mat structures can be obtained with suitably designed static dies (i.e. passive control surfaces).
5. Cooling regime is important for a successful process.
6. Finish is dependent on mandrel temperature and coating.
7. Transverse moduli sharply increased by GF and active or passive control by flow field (rotation or static).
8. Transverse strengths can be increased by a factor of 2-3 with flow field control (best with matting).
9. Impact resistance sharply increased with matting especially in elimination of crack propagation.