Adhesive gels

The most common use of curing agents is with carboxylic latices. Isocyanates and melamines can be used but zinc oxide is the most common curing agent. Zinc oxide cross-links carboxylated latices and improves bond strength by ionomer formation [78]. Carboxylated polychloroprene reacts slowly with zinc oxide in dispersed form, causing a gradual increase in adhesive gel content. This can lead to restricted adhesive shelf life. Resin acid sites compete with the polymer acid sites for Zn(II). The more resin acid sites, the more stable the adhesive. 

Adhesive Gel point (kGy) Curing dose (kGy) Volume shrinkage (%)... 

Adhesive gels may provide greater bioavailability by allowing a longer residence time than solutions. Adhesive gels may be preferred for local therapy [54,55]. 

Excessive apphcation of tissue adhesive, gel-coated slides, or the use of albumin when preparing cytospins may contribute to background stain. The use of charged slides (Fisher Superfrost/Plus, Fisher Scientific, Pittsburgh, PA) can eliminate this problem. 

During reverse osmosis and ultrafiltration membrane concentration, polarization and fouling are the phenomena responsible for limiting the permeate flux during a cyclic operation (i.e., permeation followed by cleaning). That is, membrane lifetimes and permeate (i.e., pure water) fluxes are primarily affected by the phenomena of concentration polarization (i.e., solute build up) and fouling (e.g., microbial adhesion, gel layer formation, and solute adhesion) at the membrane surface [11]. 

This chapter describes the initial results of converting waste sawdust into phenolics through fast pyrolysis employing a vortex reactor and a very fast heat transfer to depolymerize biomass into monomeric and oligomeric components. The pyrolysis method and the chemical fractionation employed to isolate the phenolic-rich fraction used in the subsequent adhesive gel testing are described. Results of an economic evaluation of the process are presented as well as the characterization of the phenolic-rich material. A novolak and a resol were successfully prepared with these compounds. 

Conventional vaginal delivery systems include tablets, foam gels, suspensions, and pessaries. Muco-adhesive gel formulations based on polycarbophil have been reported to remain 3-4 days at the vaginal tissue, providing an excellent vehicle for the delivery of progesterone and non-oxynol-9. ... 

The adhesive and binding power is particularly important in tabletting (wet granulation, dry granulation, direct compression). This property is also useful in film coatings and adhesive gels. 

Because of their excellent adhesion and physiological safety, povidone K 30 and povidone K 90 are used as adhesives on the skin or mucous membranes. Examples include transdermal systems, oral adhesive gels, buccal adhesive patches or tablets [511,546,547,559,573,574], contact gels for electrocardiograph or electroencephalograph electrodes and adhesives for colostomy bags. Table 107 shows a formulation for a contact gel developed on a laboratory scale for ultrasonic scanning. 

A relatively concentrated, e.g. 20-30%, clear solution of povidone K 90 is adequate as the basis for adhesive gel formulations for application in the mouth or for colostomy bags [375]. 

The mucociliary escalator functions when inhaled particles between 2 to 10 pm are deposited on the sticky mucous lining of the tracheobronchial tree and are propelled upward by the movement of this mucous layer in response to the beat of the cilia on the ciliated epithelial cells. This phenomenon is made possible because the mucous layer is biphasic, consisting of a watery solution in direct contact with the epithelia cells in which the cilia are free to beat. This watery solution is covered by a stickier, more adhesive gel layer that can trap and hold inhaled particles. The cilia beat in the wall layer at a rate between 1000 and 1500 strokes per minute such that at the point of their maximum upward velocity, the tips of the cilia come in contact with the gel layer to propel it upward. All recovery strokes subsequently occur in the water layer. This mechanism moves the mucus upward at a rate between 1 and 3 cm/minute. Ultimately, the mucus reaches the pharynx, where it is swallowed. Disease states that either alter the mucus-producing properties of cells in the tracheobronchial tree or decrease ciliary activity will obviously have a deleterious effect on this important clearance mechanism. 

Add items 4-6. A clear colorless adhesive gel is obtained. Addition of sodium chloride changes consistency. 

In thixotropic adhesive gels based on polyvinylalcohol, plasticizers are selected to maintain optical clarity of gel. " In some processes, plasticizers are nsed to process the... 

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