NR latex

Consumption of NR Latex. The total world consumption of natural mbber latex was 585,000 t in 1993, more than double that of 10 years earlier. The proportion of total natural mbber used as latex concentrate also increased from 7% in 1983 to 11% in 1993. Malaysia remains the dominant latex concentrate producing country in the world (Table 12). Its decline in exports during the 1980s and early 1990s has been partly compensated by an increase in consumption within the country (Table 13). Since the 1970s there has been a gradual shift in latex consumption from the traditional consumers in Europe and the United States to Asian countries. In 1994 Malaysia consumed 175,000 t of latex, more than the combined consumption of Western Europe and the United States (see Table 13). 

NR latex grades are described by the method of concentration used. Evaporation, creaming and centrifuging are the most common methods used in the industry. 

The main characteristics of NR latex are as follows high gel content high molecular weight high cohesive strength high self tack and high rubber content. 

Recently a lot of attention is being given to the field of latex-based nanocomposites. Various organoclays as well as pristine clays have been intercalated in aqueous medium with NR latex, SBR latex, NBR latex, as well as carboxylated nitrile mbber (XNBR) latex [184—187], to achieve a good degree of dispersion. 

Polymeric materials are commonly used for bonding materials. Impact or contact adhesives are mainly based on highly crystalline polychloroprene (Neoprene), NR latex is used as a flexible adhesive very suitable for use with fabrics. Rigid adhesives based on materials such as polystyrene cement, epoxy resin or cyanoacrylates are suitable for bonding of rigid materials. The bond is provided by intramolecular forces between the adhesive and the adherend. Adiabatic... 

Occupational health and safety in the rubber industry is discussed with reference to UK, US and European legislation. The review covers both natural and synthetic rubber industries. The first section outlines the laws affecting health and safety in the industry and the remainder presents specific health and safety issues of interest to employers and employees. Industrial safety is examined with reference to equipment, fire and explosions, solvents, epidemiology, NR latex allergy, skin irritations and dermatitis, dust and fume control, work-related musculoskeletal disorders, nitrosamines, 1,3-butadiene, and handling of rubber chemicals. 484 refs. 

Pressure-sensitive tape (Scotch tape) consisting of a coating of a solution of a blend of NR and an ester of glycerol and abietic acid (rosin) on cellophane was developed over a half century ago. More recently, NR latex and SR have been used in place of the NR solution. 

Fig. 39 Plots showing the effect of surface area factor on the extent of property improvement. Symbols represent experimental values, and the lines are their apparent fitting. Encircled data points are taken from unpublished research work on NR latex-based NA nanocomposites. Vertical dotted line indicates the critical point...

NR latex contains about 35wt% natural rubber hydrocarbon as particles that are about 1 pm in diameter and about 5% non-rubber components... 

PETRI c, Making NR latex nitrosamiue free and skin friendly with StruktoT, Indian Rubber Journal, 2003 75 28. 

The worldwide demand for elastomers was estimated to be 19.44 million metric tons for 2008, excluding NR latex materials. Of this demand, 55% are synthetic elastomers of various kinds. Depending on their use elastomers have been classified into general purpose and speciality. The major general purpose elastomers are natural rubber, SBR rubber, PB rubber, isoprene rubber, and ethylene-propylene rubber. These rubbers are used in tires, mechanical goods, and similar applications. Specialty elastomers provide unique properties such as oil resistance or extreme heat stability. Although this differentiation is rather arbitrary, it also tends to classify the polymers according to the volumes used. About 74% of the rubbers used consist of SBR, butadiene rubber (BR), and ethylene-propylene rubber. 

Deprotenized mbber (DPNR) — this is very useful when low water absorption is wanted, vulcanizates with low creep are needed, or more than ordinary reproducibility is required. Normally NR has between 0.25 and 0.5% nitrogen as protein DPNR has only about 0.07%. A drawback is that since protein matter in the mbber accelerates cure, DPNR requires more acceleraticm. DPNR is made by treating NR latex with bioenzyme, which hydrolyzes the proteins to water-soluble forms. A protease like Bacillus subtilis is used at about 0.3 phr. When the enzymolysis is completed the latex is diluted to 3% total soUds and coagulated by adding a mixture of phosphoric and sulfuric acid. The coagulated mbber is then pressed free of most of the water, cmmbed, dried, and baled. 

Bulk-Aid 30. [Grefco] Perlite, fused sodium potassium, aluminum silicate inert filler, processing aid, dusting agent for NR, latexes, resins. 

NC. mar Latex] NR latex for extruded thread, carpet backing, latex foam, dipped goo coatings, medical qipli-catkms, textil adhesives. 

Although foamed rubber and foamed urethanes have many similar properties, the processes by which they are made differ radically. In a simple process a solution of soap is added to natural rubber (NR) latex so that a froth will result on beating. Antioxidants, cross-linking agents, and a foam stabilizer are added as aqueous dispersions. 

When making a large article such as a mattress, a metal mold may be filled with the foamed latex and heated by steam at atmospheric pressure. After removing the foamed rubber article from the mold, it may be dewatered by compressing it between rolls or by centrifuging and by drying with hot air in a tunnel dryer. In foamed rubber formulation a part of the NR latex can be replaced by a synthetic rubber latex. One such combination is shown in Table 2.3. 

The passage of viral-sized particles through ostensibly intact NR latex films has been directly observed in the laboratory (Carey et ah, 1992 Kiernan, 1996), and indirectly observed in the field (The New York Times, 1994). Evidence for such flaws in NR comes from microscopic observations (Arnold et al., 1988), as well as water absorption measurements, wherein the initial rapid uptake suggests the existence of capillary channels (Gazeley et al., 1988). 

NR latex is a suspension of NR particles with diameter from 0.05u to about 3.0 u in water. It also contains a smaller number of easily deformable bodies (lutoid), which consist essentially a viscous aqueous solution of non rubber particles, surrounded by a breakable membrane. NR latex which freshly- tapped from Hevea Brasiliensis containing about 367i dry rubber and 3V. non rubber materials (protein, fats, phospholipid, carbohydrate and nitrogen compound). 

Table 3.Trace of Cl in NR film prepared from irradiated NR latex, sensitizer CCl 10 mg/g NR, n—BA lO mg/g NR...

The addition of monofunctional monomers on NR latex also influences the rate of crosslinking. A number monofunctional monomers (acrylates) had been investigated, but only normal butyl acrylate (n-BA) which much increasing the rate of cross1 inking. Combination of n-BA and CCl markedly increased the rate of crosslinking (Fig.2). 

Physical effect of crosslinking is shown in the increase of tensile strength up to a maximum value. Maximum tensile strength was achieved in the range of crosslink density 14-18x10 c. 1/ml (Fig.3). For NR latex added with 1 phr of CCl and 1 phr of n-BA, the maximum tensile strength was achieved at dose of about 3 Mrad while using 4 phr of CCl the dose was about 5 Mrad... 

A study on application of radiation vulcanized NR latex already be done. The most possible application is for production of rubber dipped goods rubber gloves, condom etc. Unfortunately the consumption of latex for producing these materials are relatively very low. Consumption of NR latex in Indonesia is about 6,000 tonnes annually, mainly for the production of rubber foam, and only a small amount is for producing dipping rubber goods. 

One of the drawback of radiation crosslinking of NR latex is the poor ageing property of the film. This poor ageing property may be coming from two causes natural antioxidant degrade under radiation and autoxidation due to the presence of trapped radical in NR matrix. 

Effect of irradiation and sensitizer (CCl. n-BA and EA) on crosslink density of NR film prepared fron irradiated NR latex. 

By adding an antioxidant into the irradiated NR latex, the ageing property of the film was much improved. Some researchers investigated the best antioxidant for irradiated NR latex. Antioxidant 2,2 methy1ene-bis(4-methy1-6-ter-buty1 phenol) was found to be a good antioxidant for irradiated NR latex (trade name ... 

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