Raw material preparation
The main materials of rubber products are raw rubber, compounding agents, fiber materials and metal materials. Raw rubber is the basic material; compounding agents are auxiliary materials added to improve certain properties of rubber products; fiber materials (cotton, hemp, wool and various artificial fibers, synthetic fibers) and metal materials (steel wire, copper wire) It is used as the skeleton material of rubber products to enhance mechanical strength and limit product variations.
In the raw material preparation process, the ingredients must be accurately weighed according to the formula. In order to make the raw rubber and the compounding agent evenly mix with each other, some materials need to be processed:
The raw rubber should be softened in a 60-70C drying room, and then cut and broken into small pieces;
The bulk compound such as paraffin, stearic acid, rosin, etc. must be crushed;
If the powdery compound contains mechanical impurities or coarse particles, it needs to be removed by screening;
Liquid compounding agents (pine tar, coomarone) need to heat, melt, evaporate moisture, and filter impurities;
The compounding agent should be dried, otherwise it is easy to agglomerate, it cannot be dispersed evenly during mixing, and air bubbles are generated during vulcanization, which affects the product quality;
Raw rubber is elastic and lacks the necessary properties (plasticity) during processing, so it is not easy to process. In order to improve its plasticity, it is necessary to plasticize the raw rubber; in this way, the compounding agent is easy to be uniformly dispersed in the raw rubber during mixing; at the same time, it also helps to improve the permeability of the rubber (infiltration) Fiber fabric) and molding fluidity. The process of degrading the long-chain molecules of raw rubber to form plasticity is called plasticizing. There are two types of raw rubber plastic smelting: mechanical plastic smelting and thermoplastic smelting. Mechanical plasticizing is to reduce the degradation of the long-chain rubber molecules by the mechanical extrusion and friction of the rubber hose production line at a not too high temperature, and change from a highly elastic state to a plastic state. Thermoplastic smelting is the introduction of hot compressed air into the raw rubber. Under the action of heat and oxygen, the long-chain molecules are degraded and shortened to obtain plasticity.