Melt-spun synthetic

Type 2 is ductile crack propagation with the crack opening to form a V-notch. Finally, the crack becomes catastrophic. It is found in nylon and other melt-spun synthetics. Classical illustrations of this type are readily available (3, 4). However, variations can occur. Figures la and lb show a polyester fiber subjected to tensile stress in which, after the V-notch formed, failure continued along a plane parallel to the fiber axis before eventually crossing the fiber. Thus, a split-level transverse break had occurred. 

Polyamide monofilament sutures show smooth surhices wifti a circular cross-section before implantation (see Fig. lb). No fibrous tissue cqisule was observed on the suture surface or around the knot post implantation. This is contributed to its smooth surface characteristic. However a closer examination of the opened knot shows flattening of the knot region (see Fig. 7). This is attributed to the ductile structure of polyamide sutures. It shows permanent deformation due to lateral forces exerted during loading. The rupture of the melt-spun synthetic fibres like polyamide is dominated by yield. Plastic yield of material causes the crack to open into a V-notch, vduch propagates steadily into the specimeiL This typical ductile fixture was seen at the broken ends, alter tmisile tests, both before and er implantation (see Fig. 8). 

Fracture Fatigue Defects Cracks Cotton Wool Melt-spun synthetics Solution-spun fibres... 

The general picture of the stress-strain response in the melt-spun synthetics is thus one of elastomeric extension of a rubbery network, which is constrained by being tied to the crystallites, as well as by internal bonding, up to stresses that cause a plastic disruption of the structure by further yielding of crystalline regions. 

Monofilament Synthetic Nonabsorbable Sutures. Monofilament synthetic nonabsorbable sutures are made from thermoplastic resins melt-spun to form monofilaments. Spinnarets of different capillary diameter are used to make a range of suture sizes. 

PP/silver nanocomposite fibres were prepared with the aim of achieving permanent antibacterial activity in a common synthetic textile. The fibres were melt-spun by coextmsion of PP and PP/silver masteibatches using general conjugate spinning. Masteibatches were made up of a mixture of PP chips and nano-sized silver powder. The antibacterial efficacy of spun fibres was high when the masteibatch was used as the sheath rather than the core. The antibacterial activity of nano-silver in fibres was evaluated after a certain contact time and calculated by percent reduction of two types of bacteria. Staphylococcus aureus and Klebsiela pneumoniae. DSC and wide-angle X-ray diffraction were used for analysis of stractuie, thermal properties and crystallisation behaviour of the spun fibres. SEM was carried out in order to observe particle distribution on the nanocomposite fibres. 17 refs. (2nd International Conference on Polymer Fibres, Manchester, UK, July 2002)... 

Flat-sheet asymmetric-skinned membranes made from synthetic polymers (also copolymers and blends), track-etched polymer membranes, inorganic membranes with inorganic porous supports and inorganic colloids such as Zr02 or alumina with appropriate binders, and melt-spun thermal inversion membranes (e.g., hollow-fiber membranes) are in current use. The great majority of analytically important UF membranes belong to the first type. They are usually made of polycarbonate, cellulose (esters), polyamide, polysulfone, poly(ethylene terephtha-late), etc. 

Polyester is mainly melt-spun into fibers. A smaller quantity is used for very thin films for the electrical industry. Higher molecular weight poly(ethylene terephthalate) with added nucleating agents (salts of carboxylic acids) can also be used as thermoplastic synthetics. A definite disadvantage of polyester fiber is that it yellows in light. The mechanism for this process... 

The latest addition to the synthetic absorbable suture materials is TephaFLEX which is thermally melt-spun from poly-4-hydroxybutyrate, a member of the class of absorbable biomaterials known as polydroxyal-kanoates, or PHA (FDA, 2007 Martin and Williams, 2003). Studies have shown that TephaFLEX is both biocompatible and noninflammatory. Their biodegradation occurs through normal processes and the products of the breakdown are metabolites that already exist in the body. 

Saran is the generic name for fibers made from synthetic copolymers that are greater than 80% vinylidene chloride. The fiber is formed through emulsion copolymerization of vinylidene chloride with lesser amounts of vinyl chloride using a free radical catalyst, and the precipitated copolymer is melt spun into the fiber ... 

Poly(lactic acid), produced by Nature Works LLC, is another example for a hybrid process, in which the monomer, lactic acid is produced by fermentation of com using lactobacilli. The subsequent polymerization is accomplished either by anionic ring-opening polymerization of the lactide dimer, or more recently by an azeotropic dehydration condensation, a chemical process. Cargill Dow now has shown that the polylactic acid produced by it s subsidiary NatureWorks LLC, is fully competitive with its synthetic counterparts, and fibers can also be melt-spun from this polymer. These Ingeo fibers are world s first man made fiber made from 100% atmually renewable resources. [12]. 

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