Porous fiber bonding

Water-Holding Capacity (WHC). AU polysaccharides are hydrophilic and hydrogen bond to variable amounts of water. HydratabUity is a function of the three-dimensional stmcture of the polymer (11) and is kifluenced by other components ki the solvent. Fibrous polymers and porous fiber preparations also absorb water by entrapment. The more highly crystalline fiber components are more difficult to hydrate and have less tendency to sweU. Stmctural features and other factors, including grinding, that decrease crystallinity or alter stmcture, may iacrease hydratioa capacity and solubUity. 

In order to overcome some of the drawbacks associated with the fiber bonding preparation, a solvent-casting and particulate-leaching technique was developed [32], With appropriate thermal treatment porous constructs of synthetic biode-... 

The filaments are deposited on a cicular drum equipped with a porous cover or on a horizontal moving forming belt. Vacuum is applied to the inside of the drum or xmder the belt to collect the primary hot air and the entrained cool air. The combination of fiber entanglement and fiber-to-fiber bonding generally produces enough web cohesion so that the web can be readily handled on a winder without bonding. 

Overall, fiber bonding is a very simple technique and allows the fabrication of highly porous scaffolds, although there is low control over porosity and pore size. The physical properties of the polymers (melting temperature, immiscibility), together with the solvent choice, greatly limit the appUcability of this technique to other synthetic polymers. ... 

Non-woven A porous web or sheet produced by mechanically, chemically or thermally bonding together polymers, fibers or filaments. 

Several SP materials have been used for the extraction of FRs from aqueous samples, plasma and milk (Table 31.7). Similar materials have been used for all FRs. Typical SP materials include Ci8 and Cg bonded to porous silica, highly cross-linked poly(styrene divinylbenzene) (PS-DVB), and graphitized carbon black (GCB). It is also possible to use XAD-2 resin for extraction of various FRs, pesticides, and plastic additives from large volumes of water (100 1). The analytes can then be either eluted from the resin by acetone hexane mixture, or Soxhlet extracted with acetone and hexane. For a specific determination of diphenyl phosphate in water and urine, molecularly imprinted polymers have been used in the solid phase extraction. The imprinted polymer was prepared using 2-vinylpyridine as the functional monomer, ethylene glycol dimethacrylate as the cross linker, and a structural analog of the analyte as the template molecule. Elution was done with methanol triethylamine as solvent. Also solid phase microextraction (SPME) has been applied in the analysis of PBDEs in water samples. The extraction has been done from a headspace of a heated water sample (100°C) using polydimethylsiloxane (PDMS) or polyacryl (PA) as the fiber material. ... 

Sepharose and LH-20 [165-167] have been used as supports for SPS. Both are synthetic dextran polymer beads composed of fibers in a porous network. The fragile nature and acid lability of the glycosidic bonds of the dextran are serious limitations to the use of these materials as solid supports. However, they are perfectly compatible with aqueous buffers and can be used in combined chemoenzymatic syntheses [167]. 

C-C/Cu-Clad-Mo Joints The microstructure of the composite/braze interface (Fig. I) reveals braze infiltration of the inter-fiber regions to several hundred micrometer distance in 5 min. This is consistent with the sessile-drop wettability test results [10] on Cu-Ti/porous C in which the sessile drop volume continuously decreased due to the reactive infiltration of open porosity in graphite, and sessile drops of high Ti content (e.g., Cu-28Ti) rapidly and completely disappeared into the graphite substrate. The reaction of carbon with Ti in the braze forms the wettable compound titanium carbide which facilitates self-infiltration and sound bonding. 

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