A new shear technique: Semi Continuous Shear Flow (SCSF) in medium and ultra high molecular weight Polyhydroxybutyrate blends

In MMWT/UHMWT PHB blends (99.5/ 0.5), (99/1), (98/2) and (97/3) we demonstrate that by applying our new shear technique, ‘‘semi continuous shear flow’’, copious fibre formation is guaranteed, irrespective of the ultra high molecular weight composition. The shishes formed via this technique are extremely stable being able to maintain their stability for at least 5–10 min. When this technique was applied to MMWT/UHMWT PHB blends of compositions (95/ 5), (90/10) and (85/15) disorientated fibres were observed in the flow direction. On increasing the UHMWT component, distinct unordered and intertwining of fibres resulted and with severe shearing orientation occurred, however shish formation was limited. We propose the optimum conditions for shish formation and the critical molecular weight necessary for entanglement.