Usually we say natural rubber, refers to the natural latex collected from the rubber tree in Brazil, after solidification, drying and other processing processes made of elastic solid. Natural rubber is a kind of natural polymer compound with polyisoprene as the main component, the content of rubber hydrocarbon (polyisoprene) is more than 90%, but also contains a small amount of protein, fatty acid, sugar and ash.
Acquisition method and process
Under normal circumstances, natural rubber trees can collect latex after 5 to 7 years of planting, and can collect for 25 to 30 years. Latex is found in the roots, stems, leaves, flowers and fruits of natural rubber, but it is usually stored in the latex ducts that receive cambium in the rubber bark, especially in the lower part of the trunk and the surface. The most suitable time for cutting glue is before and after sunrise in the morning, because at this time the air humidity is high, the transpiration of the gum tree is extremely slow, and the turgor pressure in the milk duct is high. When cutting glue, an incision with a tilt of about 30 degrees is cut at the trunk about one meter higher from the ground, and an aluminum groove (commonly known as glue tongue) is placed at the lower part of the incision.
Variety classification and quality standard
According to the form of natural rubber can be divided into two categories: solid natural rubber (film and granules) and concentrated latex. In daily use, solid natural rubber occupies the majority proportion. Film according to the manufacturing process and shape of the different, can be divided into smoke film, air dry film, white wrinkle sheet, brown wrinkle sheet.
Cigarette film is the most representative variety of natural rubber, once was the largest amount, the most widely used a rubber. Cigarette film is generally graded according to its appearance, which is divided into six levels, including super grade, first grade, second grade, third grade, fourth grade and fifth grade. Those less than grade five are classified as equal outer adhesive.
Granular adhesive (that is, standard adhesive SMR, also known as technical grading rubber TSR) is graded according to the international standard physical and chemical properties, indicators. These physical and chemical properties include impurity content, plastic initial value, plastic retention rate, nitrogen content, volatile content, ash content and color index, among which impurity content is the dominant index.
Properties of natural rubber
(1) Physical properties of natural rubber
Natural rubber has high elasticity at room temperature, slightly plastic, has very good mechanical strength, small hysteresis loss, low heat generation in multiple deformation, so the flexure resistance is also very good. Because it is non-polar rubber, it has good electrical insulation performance.
(2) Chemical properties of natural rubber
Because of the unsaturated double bond, natural rubber is a kind of material with strong chemical reaction ability. Light, heat, ozone, radiation, bending deformation and other metals such as copper and manganese can promote the aging of rubber. The aging resistance is the fatal weakness of natural rubber.
Natural rubber with antioxidant added, sometimes in the sun for two months, still not much change. After 3 years in the warehouse, it can still be used as usual.
The main uses of natural rubber
Natural rubber has a wide range of uses. For example, rain shoes, warm water bags and elastic bands used in daily life; Of course, also used in children’s toys, is also very excellent environmental protection, soft surface with cute animal shape, is the perfect choice for children’s toys ~
At present, there are more than 70,000 items in the world made partly or entirely of natural rubber. Natural rubber and steel, oil and coal and known as the four industrial raw materials, is related to the national economy and people’s livelihood of important strategic materials.