Coagulum types

The structure of gels depends on the components and the process parameters. Proteins containing over 30% hydrophobic residues form coagulum-type gels, e.g., hemoglobin and egg white albumin. The gelling-type proteins contain less hydrophobic residues and are represented by some soybean proteins, ovomucoid, and gelatin. 

TSR 5. Within the Malaysian scheme SMR 5 is restricted to mbber derived from sheet material prepared by conventional processes, ie, ribbed smoked sheet (RSS), air-dried sheet (ADS), and unsmoked sheet (USS) and presented in small bale form. Other countries may source different raw materials, eg, Indonesia produces SIR 5 from thin latex coagulum (14). SMR 5 prepared by pressing dry-sheet material into standard bales must be identified by the type of sheet material, eg, SMR 5RSS, on the test certificate as well as on the wrapping. 

Whey is the fluid obtained by separatiag the coagulum from cream and/or skim milk, and is a by-product of either caseia or cheese manufacture. The composition of whey is determined by the method of curd formation, curd handling practices, and methods of handling whey as it is separated from the curd. Dried acid whey contains ca 12.5 wt % proteia (total nitrogea x6.38), 11.0 wt % ash, and 59 wt % lactose, whereas sweet whey contains 13.5 wt % proteia, 1.2 wt % fat, 8.4 wt % ash and 74 wt % lactose. The composition varies with the type of acid used (7). 

This is a type of natural plantation rubber made by flocculating formaldehyde-preserved latex. Formaldehyde is added to the latex as soon as possible after tapping, dirt is allowed to settle out the latex is bulked, flocculated with acid and the floccs coalesced by steam heat. The coagulum is... 

Blanket crepes are of lower quality and are made from wet slabs obtained usually from small landholders. These are creped. dried, and baled. Other types of crepe are made from coagulum left in collection cups and from dried skin remaining from the tapping incision. In addition to collecting latex, a tapper collects all dried and coagulated rubber that remains from die previous round, usually as skin m the cup or on the tapping panel. 

The formation of coagulum is observed in all types of emulsion polymers (i) synthetic rubber latexes such as butadiene-styrene, acrylonitrile-butadiene, and butadiene-styrene-vinyl pyridine copolymers as well as polybutadiene, polychloroprene, and polyisoprene (ii) coatings latexes such as styrene-butadiene, acrylate ester, vinyl acetate, vinyl chloride, and ethylene copolymers (iii) plastisol resins such as polyvinyl chloride (iv) specialty latexes such as polyethylene, polytetrafluoroethylene, and other fluorinated polymers (v) inverse latexes of polyacrylamide and other water-soluble polymers prepared by inverse emulsion polymerization. There are no major latex classes produced by emulsion polymerization that are completely free of coagulum formation during or after polymerization. 

The coagulum formed in a latex can be divided into three main types (i) coagulum formed during polymerization and recovered from the latex afterwards by filtration or sedimentation ... 

Whey is the liquid obtained by separating the coagulum from milk, cream, and/or skim milk in cheese making. Whey obtained from the process in which a significant amount of lactose is converted to lactic acid or obtained from the curd formed by direct acidification of milk is known as acid-type Whey. Whey obtained from the process in which there is insignificant conversion of lactose to lactic acid is known as sweet-type Whey. The acidity of Whey may be adjusted by the addition of safe and suitable pH-adjusting ingredients. The final product is pasteurized and is available as a liquid or dry product. 

When protein solutions are shaken, insoluble protein is often seen to separate out (Bull and Neurath, 1937). The coagulation occurs at the interface and may be observed when protein is allowed to adsorb from solution at a quiescent interface (Cumper and Alexander, 1950) or when spread protein monolayers are compressed (Kaplan and Frazer, 1953). This is an interesting type of phase separation in which a three-dimensional coagulum is formed from the two-dimensional monolayer, once a certain critical value of the interfacial pressure is exceeded. The concentration of protein in the monolayer when the critical pressure is reached may be thought of as the solubility in the interface under those conditions. When this concentration is exceeded, precipitation occurs. A simple model may help to illustrate how free energy considerations govern the coagulation. 

Four types of coagulum are collected in the field, namely cup lump, tree lace, earth scrap and smallholders lump. Cup lump is the coagulated material found in the collection cup formed from residual latex after the latex was collected from a previous tapping. It is a cleaner material than the other three. Tree lace is the coagulum strip that the tapper peels off from the previous cut before making a new cut. It is often contaminated by manganese from the bark and... 

A major dry natural rubber type is ribbed smoked sheet. For this the coagulum is passed between pairs of even-speed steel rollers that squeeze the water out. The final set of rollers has channels cut in them so that the sheet emerging from them has a ribbed surface. The ribbed surface facilitates drying. This rubber is dried in smokehouses. The ribbed sheets are hung over poles mounted on trolleys. Rubber tree wood fires produce the smoke, which dries the rubber and gives the rubber some age resistance from its components such as cresols. Drying takes 48 to 96 hours, with entrance temperatures at about 40 °C and exit temperatures at about 60 °C. Some ribbed sheet rubber is dried in hot air out of contact with smoke. This produces a lighter colored rubber, which commands a premium and is referred to as air-dried sheets. 

Coagulum is formed in many emulsion polymerizations, from the smallest laboratory size to the largest production reactors. It is observed in many forms, from a single lump of polymer with little or no fluid latex to tiny sand-like grains suspended in an otherwise stable latex. Usually, it is found as lumps in the latex or deposited on the reactor surfaces. The type and amount of coagulum formed depends upon the polymer system and the polymerization recipe and technique. Two mechanisms are proposed for the formation of coagulum (i) a failure of the stability of the latex, giving rise... 

The formation of coagulum is observed in all types of emulsion polymers (i) synthetic rubber latexes such as butadiene-styrene,... 

Coagulum is almost invariably formed when the monomer used in emulsion polymerization contains dissolved polymer the coagulum comprises not only the dissolved polymer but also part of the monomer as well (10). The first experiments (11) comprised the addition of polystyrene of MW 3.5x10 to styrene monomer and its polymerization in capped 4-oz bottles at 70° using a 32 68 styrene-water ratio (2.8-oz charge), and 0.37% sodium lauryl sulfate emulsifier, 0.40% potassium persulfate initiator, and 0.46% sodium bicarbonate buffer, all based on water. Two types of coagulum were formed a hard, glassy lump and a soft paste which dried to a pow-... 

There are several visually graded latex NRs, including ribbed smoked sheets (RSS) and crepes such as white and pale, thin and thick hrown latex, etc. Two types of raw NR are field latex and raw coagulum, and these two types comprise all NR ( downstream )... 

Caoutchouc began to appear in large compilations of chemical knowledge such as J. Murray s A System of Chemistry [6]. It was noted that the tree sap from the Hevea guianensis (a type of Euphorbia) could be separated into a firm elastic coagulum and a watery liquid. The specific article on caoutchouc contains a clear declaration The most remarkable physical property of which this substance is... 

Deep peels are not typically performed in Fitzpatrick skin types IV-VI, but can be done successfully by experienced physicians. Rullan Karam found deep peels to be particularly effective for the treatment of challenging acne scars. These require taping the face for 24 hours, removal, debridement of the coagulum, and application of a bismuth subgallate powder mask. This mask is left in place for about 7 days and then is carefully removed. The vast majority (99%) of patients are over 95% reepithehalized by the 8 day following the peel. 

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