Irradiation melt-spinning

A comfortable pathway for improvement of the crystallization of poly(3-hydroxybutyrate) in a melt-spinning process is the use of nucleating agents like electron-beam irradiated PHB [28] or the reactive extrusion with peroxide [29]. 

PVDF and PP sutures have very similar melting temperatures (165-175°C), but distinctively different level of crystallinity. PVDF has a level of crystallinity 59% 7%,whilePPhas43% 3%. Because ofthe lack ofan a alkyl group, PVDF could be sterilized by the conventional /-irradiation method, while PP requires the use ethylene oxide gas. Thus, PVDF could take advantage of the effidenqr and convenience of /-irradiation sterilization. like PP sutures, PVDF sutures should not have any Oj element in their chemical structure. However the surface of PVDF and PP sutures showed oxidation products as confirmed by electron spectroscopy for chemical analysis. The amounts of O2 element on the surface of PVDF and PP sutures were 7.4% and 7.9%, respectively. However, bulk FUR data failed to reveal such oxidation products. This suggests that oxidation of PVDF and PP is introduced during melt spinning of fibers and is mainly restricted to the surface of suture fibers. 

Rather hydrophobic hoUow-fiber membranes are produced by melt spinning from blends of isotactic and atactic PMMA starting from the pure MMA monomers, or copolymerized with small amounts of p-styrene sodium sulfonate, dissolved in dimethylsulfoxide. Symmetric, almost homogeneous, PMMA membranes for HD, HF and TA are commercially available that are all sterilized by "y-ray irradiation. Their adsorptive properties have been reported to cause platelet adsorption with fibrin formation, possibly leading to high residual blood volumes in the filter (LocateUi et al., 2000) and one reported case of anaphylactic reaction (Hoenich, 1998). 

Other complexities are revealed when frozen solutions of spin trap in methanol are irradiated, and the solution is then melted. The proportions of spin adducts are markedly dependent on radiolysis temperature. One contributory factor is undoubtedly the reaction of MeO with neighbouring methanol in the solid matrix, to produce HOCH2, before diffusion to reach spin-trap molecules is possible. 

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