BACKGROUND: The objective of this work was to decellularize artificial tissue without using surfactant solutions. For this purpose, supercritical carbon dioxide was used as the extraction medium.

Several types of polyester fibers, i.e. high speed spun (HSS) fibers, partially oriented yarns (POY), and fully oriented yarns (FOY), were subjected to the supercritical CO 2 fluid treatment (SFT) at 120℃, 20MPa for 1 h and structural modifications were investigated. Large shrinkage and not a small amount of oligomer deposition on the fiber surface were observed for POY and FOY. On the contrary, as for HSS fibers produced at a spinning speed of 6 km/min the shrinkage was suppressed within 2 % as compared with an initial fiber length and the oligomer deposition could hardly be observed. The shrinkproof property for HSS fibers seems to be closely related to the well developed fibrous structure. Such structure can be easily confirmed via the alkaline etching. The oligomer migration can be lowered by accelerating the orientation-induced crystallization rate on the high speed spinning line and disordering the molecular orientation in amorphous regions. In addition ultra-crystallites formed in amorphous regions during SFT will also be effective for the suppression to the oligomer migration. The disordered macromolecules and the ultra-crystallites formed in amorphous regions will develop a network-like structure that suppresses the oligomer migration. Therefore, a novel polyester fiber suitable for the supercritical CO 2 fluid dyeing is producible by controlling the fibrous structure and designing the amorphous regions using the high speed spinning process.

Summary: Spin‐drawing yarn (SDY) and high‐speed spun (HSS) fibers were produced from recycled poly(ethylene terephthalate) pellets, and the oligomer deposition on the surface of fiber in supercritical carbon dioxide fluid was compared. The oligomer deposition was obvious for SDY, which corresponded to the fact that the amount of imperfect small crystallites generated in amorphous regions through s‐CO2 treatment was much smaller for SDY as compared to that with HSS. The imperfect small crystallites generated in amorphous regions will work as a barrier to the oligomer migration. In order to suppress the deposition of oligomer for SDY, the combination of a heatset treatment and an alkaline etching was useful. At a heatset process, the oligomer migration to the surface layer tends to occur, and the layer becomes rich in oligomer. The following topochemical hydrolysis reaction at alkaline etching removes such layer. Accordingly, the total content of oligomer in etched fiber is reduced. As a result, the oligomer deposition in s‐CO2 treatment becomes not so serious. In addition, the heatset treatment gives the shrinkproof property to SDY, and the property is still retained after the alkaline etching. magnified image

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PET and PE fishing net wastes were compression molded into sandwich-type boards, which were evaluated mechanically by three point bending test. The PET and PE fishing nets were knitted beforehand, then molded into PE/PET/PE laminates with three layers and PE/PET/PE/PET /PE laminates with five layers. The process was controlled so that only the PE layers were melted by the infrared heaters, and air was trapped in the non-melted core PET layers. As a result, a flexible, heat insulating board was achieved. The molding method described herein shows promise in contributing toward the recyclability of cord-type waste materials, such as fishing nets.