Fibrous absorbents

Some fibrous absorbents contain a proportion of acrylamide or other synthetic polymeric fiber. They frequently enhance the absorptive performance and give body to the fleece thus improving fluid retention and avoiding squeeze out which is caused by fleece collapse after wetting. 

Delany, M.E., Bazley, E.N., 1971. Acoustical properties of fibrous absorbent materials. Appl. Acoust. 3,105—116. 

An inherent limitation of fibrous absorbent cores is that the bulk of the fluid is weakly held in the capillary structure and can escape (leak) upon squeezing. Such flowback leaks are minimized by the inclusion of superabsorbent polymer in the absorbent matrix. In the modern disposable diaper, the absorption burden is shared almost equally between the superabsorbent polymer and the fibrous matrix. In addition to acting as a fluid repository, the fibrous matrix has the critical functions of accepting and transporting the absorbed urine throughout the absorbent core. Interactions between the components in an absorbent product and between the components and the absorbed fluid must be considered in product design. 

Attenborough K. Acoustical characterization of rigid fibrous absorbents and granular media. J. Acoust. Soc. 

Other fibrous and porous materials used for sound-absorbing treatments include wood, cellulose, and metal fibers foamed gypsum or Pordand cement combined with other materials and sintered metals. Wood fibers can be combined with binders and dame-retardent chemicals. Metal fibers and sintered metals can be manufactured with finely controlled physical properties. They usually are made for appHcations involving severe chemical or physical environments, although some sintered metal materials have found their way into architectural appHcations. Prior to concerns regarding its carcinogenic properties, asbestos fiber had been used extensively in spray-on acoustical treatments. 

Acoustical Louvers. Acoustical louvers are used in building mechanical systems when exterior walls are penetrated for fresh air intake, exhaust, or rehef air, in situations where the impact of HVAC noise is of concern in the surrounding environment. The louvers consist of a series of hoUow sheet metal blades. The bottom faces of the louver blades are perforated and the blades are filled with fibrous sound-absorbing material. Typical acoustical louvers are 20 cm (8 in.) to 30 cm (12 in.) in depth. The amount of insertion loss they provide is limited. 

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. 

Dust can be said to be a solid broken down into powder, and the form that it takes will have different effects on the body. Fibrous dusts can attack tissue directly while others may be composed of poisons, which are absorbed into the bloodstream. For the purpose of this chapter, fumes can be regarded as very small particles resulting from the chemical reaction or condensation of vapor, which can have the same two effects. It is not necessary for plant engineers to have an in-depth knowledge of pathology, only that they must be aware of the possible results of exposure to dusts and fumes. 

In vivo biocompatibility was assessed through subcutaneous implantation in Sprague-Dawley rats. PLGA was used as a control polymer. PGS and PLGA implants with the same surface area/volume ratio were implanted in dorsal subcutaneous pockets. A fibrous capsule around PGS (45 pm thick after 35 days implantation) appeared later than that around PLGA (140 pm thick after 14 days implantation). After 60 days of implantation, the implant was completely absorbed with no signs of granulation or scar formation. ... 

The reduction of blood loss during or after surgical procedures where suturing or hgature is either impractical or impossible can often be accomphshed by the use of sterile, absorbable haemostats. These consist of a soft pad of sohd material packed around and over the wound which can be left in situ, being absorbed by body tissues over a period of time, usually up to 6 weeks. The principal mechanism of action of these is the ability to encourage platelet fiacture because of their fibrous or rough surfaces, and to act as a... 

This is composed of the sodium and ealeium salts of alginic add formed into a powder or fibrous material and sterilized by autoelaving. It aids clotting by forming a sodium-caldum alginate complex in contact with tissue fluids, acting principally as a mechanical haemostat. It is relatively slowly absorbed and some residues may occasionally remain in the tissues. 

When extensively exposed to air (as a thin film, or absorbed on fibrous or porous solids), it may ignite. 

Organic materials, particularly if fibrous with adsorbed or absorbed moisture present, may char or ignite in contact with the stabilised liquid form because of the very high heat of hydration (2.1 kJ/g) and formation of hot oleum which then functions as an oxidant. 

The experience of application of various efferent methods of endotoxin elimination has led to the idea of creating selective anti-LPS hemosorbents with Polymyxin B as the bioUgand. The covalently immobilized Polymyxin B does not cause side effects characteristic of free Polymyxin B and keeps its therapeutic effects. G.W. Duff in 1982 demonstrated for the first time the sorption efficiency of Polymyxin B-immobilized sorbent in vitro [9]. In 1984 K. Hanasawa with co-workers developed PMX-F - a fibrous polystyrene based hemosorbent with immobilized Polymyxin B that could be used directly for blood perfusion [10]. In 1994 PMX-F sorbent was officially approved for patient treatment in Japan. Currently, there are several polymyxin immobilized (PMX-F) sorbents produced commercially for clinical use, such as Alteca - LPS Absorber (Sweden), Toray Industries hic. (Japan), etc. However these sorbents have poor hemocompatibility and are very expensive. 

---