Fibers from Film

Fiber fibrillation Production of fiber from film. 

Starch pyrodextrins and British gums have the abiUty, in aqueous dispersion, to form films capable of bonding like or unlike materials. Thus, they have uses as adhesives for envelopes, postage stamps, and other products. These dextrins are used in glass-fiber siting to protect the extmded fiber from abrasion, and as binders for metal core castings, water color paints, briquettes, and many other composite materials (qv). 

With the renewed interest in environmentally friendly products, ceUulose esters are being re-evaluated as a natural source of biodegradable thermoplastics. CeUulose acetates are potentiaUy biodegradable (152). Films prepared from a ceUulose acetate with a DS of 2.5 were shown to require only a 10—12 day incubation period for extensive degradation in an in vitro enrichment assay. Similarly, films prepared from a ceUulose acetate with a DS of 1.7 saw 70% degradation in 27 days in a wastewater treatment facUity, whereas films prepared from a ceUulose acetate with a DS of 2.5 required approximately 10 weeks for similar degradation to occur. The results of this work demonstrate that ceUulose acetate fibers and films are potentiaUy environmentally nonpersistant. 

Two approaches to the attainment of the oriented states of polymer solutions and melts can be distinguished. The first one consists in the orientational crystallization of flexible-chain polymers based on the fixation by subsequent crystallization of the chains obtained as a result of melt extension. This procedure ensures the formation of a highly oriented supramolecular structure in the crystallized material. The second approach is based on the use of solutions of rigid-chain polymers in which the transition to the liquid crystalline state occurs, due to a high anisometry of the macromolecules. This state is characterized by high one-dimensional chain orientation and, as a result, by the anisotropy of the main physical properties of the material. Only slight extensions are required to obtain highly oriented films and fibers from such solutions. 

In particular, it has been shown that the most important factor determining the drawing conditions of fibers and films of i-PP is the structure (a or mesomorphic) which characterize the yarn or the film obtained by extrusion. The drawing from mesomorphic samples requires, indeed, a lower tension and, generally, higher draw ratios are obtained [125,126],... 

The distance of each reflection from the center of the pattern is a function of the fiber-to-film distance, as well as the unit-cell dimensions. Therefore, by measuring the positions of the reflections, it is possible to determine the unit-cell dimensions and, subsequently, index (or assign Miller indices to) all the reflections. Their intensities are measured with a microdensitometer or digitized with a scanner and then processed.8-10 After applying appropriate geometrical corrections for Lorentz and polarization effects, the observed structure amplitudes are computed. This experimental X-ray data set is crucial for the determination and refinement of molecular and packing models, and also for the adjudication of alternatives. 

P-plastomers provide a unique combination of ease of processing, such that conventional thermoplastic-processing routines and arid equipment can be adapted to this polymer as weU as for a final fabricated product that is elastic. This combination of properties leads to the easy fabrication of elastic materials such as fibers and films, which traditionally have only been made inelastic by the use of thermoplastics. This advance opens the pathway to the introduction of desirable elastic properties to a host of fabrication processes very different from either the conventional rubber-processing equipment or the conventional rubber products, such as tires. P-plastomers and their fabricated products are not only soft, but also elastic. 

We can use density gradient columns to measure the density of all manner of polymer samples, from fibers and films to specimens cut from molded parts. 

Silk fibers or monolayers of silk proteins have a number of potential biomedical applications. Biocompatibility tests have been carried out with scaffolds of fibers or solubilized silk proteins from the silkworm Bombyx mori (for review see Ref. [38]). Some biocompatibility problems have been reported, but this was probably due to contamination with residual sericin. More recent studies with well-defined silkworm silk fibers and films suggest that the core fibroin fibers show in vivo and in vivo biocompatibility that is comparable to other biomaterials, such as polyactic acid and collagen. Altmann et al. [39] showed that a silk-fiber matrix obtained from properly processed natural silkworm fibers is a suitable material for the attachment, expansion and differentiation of adult human progenitor bone marrow stromal cells. Also, the direct inflammatory potential of silkworm silk was studied using an in vitro system [40]. The authors claimed that their silk fibers were mostly immunologically inert in short and long term culture with murine macrophage cells. 

Surface Modification of Cellulose and PVA Films. Cellulose, as well as PVA,is known to be a typical non-ionic, hydrophilic polymer possessing hydroxyl groups. As this group has a high reactivity,chemical modification of these polymers is relatively easy and, in fact, has been the subject of extensive research. However, so far as we know, no work has been reported concerned with reactions occurring only at the surface of films or fibers from these polymers. 

The second method, applicable only to CNTs, consists in drawing a fiber from an array of aligned CNTs by taking advantage of the van der Waals forces between neighboring CNTs in the array to withdraw them continuously from the substrate [63]. The drawing process forms a low density film that has to be twisted or densified with liq-... 

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