Performance comparison of rubber seals

Rubber Overview

（1） The natural properties of rubber. What we usually refer to as natural rubber are solid substances made from natural rubber latex collected from rubber trees and processed through solidification, drying, and other processes. Natural rubber is a natural polymer compound mainly composed of polyisoprene, with a molecular formula of (C5H8) n. Its rubber hydrocarbon (polyisoprene) content is over 90%, and it also contains small amounts of protein, fatty acids, sugar, and ash.

The physical properties of natural rubber. Natural rubber has high elasticity and slight plasticity at room temperature, with excellent mechanical strength, low hysteresis loss, and low heat generation during multiple deformations. Therefore, its flexural flexibility is also good, and because it is non-polar rubber, its electrical insulation performance is good. The chemical properties of natural rubber. Due to the presence of unsaturated double bonds, natural rubber is a substance with strong chemical reactivity. Light, heat, ozone, radiation, flexural deformation, and metals such as copper and manganese can all promote the aging of rubber. Aging resistance is the fatal weakness of natural rubber. However, natural rubber with added anti-aging agents may not show much change even after being exposed to sunlight for two months, and can still be used as usual after being stored in a warehouse for three years. The medium resistance properties of natural rubber. Natural rubber has good alkali resistance, but is not resistant to strong acids. Due to the non-polar nature of natural rubber, it can only withstand some polar solvents and swells in non-polar solvents. Therefore, its oil and solvent resistance is poor. Generally speaking, hydrocarbons, halogenated hydrocarbons, binary char, ethers, higher ketones, and higher fatty acids all dissolve natural rubber, but their solubility is affected by the degree of plasticization. Lower ketones, lower vinegars, and alcohols are non solvents for natural rubber.

（2） Variety classification and quality standards: Natural rubber can be divided into two categories based on its morphology: solid natural rubber (film and granular rubber) and concentrated latex. In daily use, solid natural rubber accounts for the vast majority of the proportion. Film can be divided into cigarette film, air dried film, white wrinkled film, brown wrinkled film, etc. according to different manufacturing processes and shapes. Smoke sheet rubber is the most representative variety of natural rubber, and has always been a widely used and widely used type of rubber. Smoke sheet rubber is generally classified according to its appearance, divided into six levels: special grade, first grade, second grade, third grade, fourth grade, and fifth grade. If it does not reach the fifth grade, it is classified as an outer grade rubber. Particle glue (i.e. standard glue) is classified according to internationally unified physical and chemical properties and indicators, including impurity content, initial plasticity value, plasticity retention rate, nitrogen content, volatile matter content, ash content, and color index. Among them, impurity content is the main leading indicator, and it is divided into five levels according to the amount of impurities, including 5L, 5, 10, 20, and 50. The delivery levels of natural rubber contracts on the Shanghai Futures Exchange are domestic first grade standard rubber SCR5 and imported cigarette adhesive RSS3. Among them, domestic first grade standard rubber SCR5 is usually also known as No. 5 standard rubber, which complies with the various quality indicators of natural rubber GB/T8081-1999 version issued and implemented by the State Administration for Technical Supervision. Imported cigarette adhesive RSS3 follows the "International Quality and Packaging Standards for Natural Rubber Grades" (Green Book) (1979 edition) established by the International Rubber Quality and Packaging Conference. （3） The main use of rubber is due to its series of physical and chemical properties, especially its excellent resilience, insulation, water resistance, and plasticity. After appropriate treatment, it also has valuable properties such as oil resistance, acid resistance, alkali resistance, heat resistance, cold resistance, pressure resistance, and wear resistance, making it widely used. Such as rain boots, warm water bags, and elastic bands used in daily life; Surgical gloves and blood transfusion tubes used in the healthcare industry; Various tires used in transportation; Conveyor belts, transport belts, acid and alkali resistant gloves used in industry; Irrigation hoses and ammonia bags used in agriculture; Sounding balloons used for meteorological measurements; Sealing and shock resistant equipment used in scientific experiments; Aircraft, tanks, cannons, and gas masks used in national defense; Even becoming an indispensable raw material for high-precision scientific and technological products such as rockets, artificial Earth satellites, and spacecraft. Currently, there are over 70000 items in the world that are partially or completely made of natural rubber.