Composition of natural rubber and its effect on processing performance

1. Ingredients and what they do

When latex is used to make NR, some non-rubbery hydrocarbon components remain in solid NR. In general, non-rubbery hydrocarbon components account for 5% ~ 8% of solid natural rubber, as shown in Table 1-2. Rubber hydrocarbons account for 92% ~ 95%. Fresh latex contains two kinds of proteins, alpha protein and rubber protein. Protein is easy to absorb moisture, mold, make the electrical insulation decreased,

Increase thermogenesis, making some people who contact it allergic; Protein decomposition products promote vulcanization and delay aging; Granular protein has enhanced effect. Acetone extract refers to the part of NR that can be dissolved in acetone, which is composed mainly of lipids and their decomposition products. The lipids in fresh latex are mainly composed of

Fat, wax, sterols, sterol esters, and phospholipids. After adding ammonia to latex, some components of lipids decompose to produce fatty acids such as stearic acid and oleic acid. Therefore, in addition to the non-rubbery hydrocarbon contained in the latex, there are fatty acids in NR. Some acetone extracts play a dispersive role in mixing and a promoting role in vulcanization,

When used, it plays an anti-aging role. Here, it is particularly important to point out that phospholipid is insoluble in acetone, so it does not belong to acetone extract, its decomposition products have choline, can promote vulcanization. There are mainly calcium phosphate and magnesium phosphate in ash, and a small amount of iron, copper, manganese and other variable metal compounds that will promote rubber aging.

For them to limit the content. For example, the American standard glue stipulates that the copper content is less than 0.00082% and the manganese content is less than 0.0010%.

2. Protein allergy

Natural latex usually contains protein with a mass fraction of 0.01 ~ 0.02, which can cause allergy in people exposed to natural latex products. Due to the increasing use in recent years, allergic events occur frequently, and the proportion of allergy is 12.5%, of which 2.5% have allergy and 10% produce antibodies in the blood. The main cause of allergy is latex products

In the residual soluble (extracted) protein, studies have shown that natural latex products in the residual soluble protein mass fraction less than 110x10-6, basically do not occur allergic symptoms. However, the residual soluble protein mass fraction in the latex and its products concentrated by centrifugation is much greater than 110x10-6.

The protein content of latex can be effectively reduced by enzyme, radiation and multiple centrifugation washing. Low protein latex with a residual soluble protein fraction of 10-6 (minimum of 35.7x10-6) has been produced in China, which meets the requirements of soluble protein fraction less than 50x10- according to the quality standard of Food and Drug Administration of the United States.

At present, only a few countries have successfully developed low-protein latex and its products and put them into production, among which Malaysia is the main low-protein latex production country.