Latex Collection

Latex is obtained from the tree by a process called tapping. Near the cambium layer in the bark are the latex vessels, a network of capillary tubes that occur in all parts of the tree but are concentrated in the bark. Here the plant food is changed into rubber hydrocarbon. A cut is made into the thin lay of lactiferous vessels, the cambium lay being carefully avoided. Latex exudes from this cut and is collected. 

Tapping is done in the early morning hours when flow is at a maximum. After about 5 hours, the flow rate decreases, the cut latex vessels start to choke with coagulated latex, and the flow stops. At the time of tapping, a small amount of ammonia is placed in the cup to prevent premature coagulation. 

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Root latex collection and root surface extraction, and the use of LC-MS and HPLC to identify root chemicals. Freshly harvested roots of Tanzania and New Kawogo varieties were broken in two by hand, which ensures maximum flow of latex, as opposed to cutting using a sharp knife which seems to inhibit the flow. The... 

NR can also be exported as concentrated latex. Fresh field latex consists of 30-40% dry rubber content (DRC), the other 60-70% being mainly water-containing non-rubber substances. The non-rubber components, e.g. proteins, carbohydrates, lipids and inorganic salts, vary according to clones, season and age of rubber tree. The latex collected from the plantation is preserved with ammonia (NH3) and then undergoes continuous centrifugation to produce the... 

Latex continues to drip after the initial collection and coagulates naturally in the cup to form cup lump. Coagulum which forms as a film of latex on the tapped cut, called tree lace, or from latex that has dripped onto the ground, called earth scrap, is collected the next day along with the cup lump. Some smallholders may not collect the latex at all, but allow it to coagulate in the cup and collect it as cup lump. AH these methods produce mbber known as field coagulum. 

TSR L, TSR L is a color-specified mbber, and the light amber color is produced by selecting clones with a low carotenoid content. After collection, the field latex is preserved with a mixture of ammonia and boric acid and subsequendy treated using 0.05% sodium metabisulfite to inhibit... 

Membrane-retained components are collectively called concentrate or retentate. Materials permeating the membrane are called filtrate, ultrafiltrate, or permeate. It is the objective of ultrafiltration to recover or concentrate particular species in the retentate (eg, latex concentration, pigment recovery, protein recovery from cheese and casein wheys, and concentration of proteins for biopharmaceuticals) or to produce a purified permeate (eg, sewage treatment, production of sterile water or antibiotics, etc). Diafiltration is a specific ultrafiltration process in which the retentate is further purified or the permeable sohds are extracted further by the addition of water or, in the case of proteins, buffer to the retentate. 

Guayule, potentially a source of natural mbber, is an unusual crop in that it has been an article of commerce in the past. Guayule grows wild in northern Mexico and the southwestern United States. When the leaves are milled in water, a latex is released that coagulates into natural mbber worms. These can easily be collected and relatively easily refined to give a product that is almost identical to the natural mbber from southeast Asia. During World War II there were several thousand acres of guayule planted in California and a small plant estabUshed to extract the mbber for military use. After the war. 

Natural rubber is harvested as latex by tapping trees in a manner similar to maple syrup. Tree latex contains about 35 wt% rubber solids, as well as small quantities of carbohydrates, resins, mineral salts and fatty acids. Ammonia should be immediately added to the latex to avoid coagulation by these other ingredients and to prevent bacterial degradation. After collection, the latex can be concentrated to 60-70% solids if the latex product is required for end-use. Otherwise, the latex is coagulated, washed, dried, and pressed into bales for use as dry rubber. 

Originally from China, Rhus vernicefera has been under cultivation in Japan since the sixth century AD. The latex is collected in the same way as the rubber plant Hevea brasiliensis. The product is known as urushiol, which consists mostly of dihydric phenols of structures (Fig. 6) and is used as lacquers. 

Ny lon-6 (108 g) carpet backed with calcium-carbonate-filled latex and polypropylene was charged to a 1000-mL three-neck round-bottom flask (equipped with a condenser) with 6 mL of 85% phosphoric acid. Superheated steam was injected continuously during a 45-min period. The vapor temperature of the reaction medium was 250-300°C. The volume of distillate collected was 1065 mL. The distillate contained 1.9% e-caprolactam (as determined by GC), which corresponded to a crude yield of 37.5%. The distillate was fractionated in a distillation column and the nonaqueous phase removed. The remaining aqueous phase was treated with 2% potassium permanganate at 40-50°C for 2 h. Evaporation of... 

FIGURE 19.8 Collecting latex from a rubber tree in Malaysia, a principal producer of latex. 

The rubber industry has a long and colorful history. Natural rubber is produced from latex, a milky fluid found in cells that lie between the bark and the wood of many plants. You may have seen latex flow from the broken stalks of milkweed plants, but the source of commercial rubber is the Hevea tree, a native of Brazil. When the bark of this tree is slashed, its milky white sap oozes out and can be collected in cups mounted on the tree s trunk. The people of the Amazon jungle made bouncing balls, shoes, and water Jars out of rubber, and Portuguese explorers sent waterproof boots and a rubber-coated coat back to their king. The first commercial exports included some rubber shoes shipped to Boston in 1823. 

The s.a.n.s. experiments were carried out using the D17 camera at the I.L.L., Grenoble. Data were collected at two wavelengths, 0.8 and 1.4 nm at a sample to detector distance of 1.8 m. The overlapping spectra were combined to give a sufficiently wide Q range to enable the data to be numerically inverted to obtain the density distributions. The latex dispersions were prepared at a solids concentration of 4% and polymer solution concentrations between 200 and 300 ppm. 

Colloidal particles, foams used to collect and separate, 12 22 Colloidal powders, 23 55-56 Colloidal silica, 22 380, 382, 384 applications of, 22 394 modification of, 22 393-394 preparation of, 22 392-393 properties of, 22 391-392 purification of, 22 393 Colloidal silica gels, 23 60 Colloidal solids, 7 293-294 Colloidal stability, 7 286-291 10 116 22 55 Colloidal stabilizers, in polychloroprene latex compounding, 19 857 Colloid mills, 8 702 10 127 Colloids, 7 271-303 23 54. See also Polymer colloids analysis, 7 296 applications, 7 292-296 conducting, 7 524... 

The main path of the research employed both methods of synthesis in turn. At first, the graduate students Yenwo and Pulido explored the use of sequential IPN s based on castor oil urethanes and polystyrene (12-16). At the same time, the graduate student Devia, working in Colombia, explored an alternate synthetic route using latex technology (17). Since nothing was known about the behavior of such materials, their collective objective was to provide a map upon which further efforts could be intelligently based. This effort has now been reviewed (18). 

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