Why Can’t Synthetic Rubber Fully Replace Natural Rubber?
Evolution of natural rubber:
The significance of rubber in human history is profound. Notably, the invention of the wheel drastically changed human life, and the advent of the tire enhanced the wheel’s usability and comfort, revolutionizing human mobility and goods transportation, thus significantly boosting work efficiency. The emergence of the tire enabled the widespread use of wheels.
The discovery and widespread use of rubber propelled the development of the tire and automotive industries, marking a crucial milestone in human civilization. However, the primary source of natural rubber is the rubber tree, which thrives in tropical regions such as Brazil and Southeast Asia. Meanwhile, the main usage areas for rubber are concentrated in economically developed regions, leading to a significant imbalance in rubber supply and demand. Notably, during World War I, Germany cut off rubber supplies; in World War II, Japan occupied Southeast Asia, the main natural rubber-producing region, limiting rubber supply to Europe and the United States. Hence, scientists began experimenting with synthetic rubber, achieving significant breakthroughs. Synthetic rubber production, unaffected by weather and geography, rose from 23,000 tons in 1939 to 885,000 tons in 1944.
With the end of the war and the stabilization of natural rubber supplies, coupled with the post-war boom in automotive and related industries, the demand for rubber soared, keeping natural rubber prices high. Consequently, synthetic rubber partially replaced natural rubber in certain applications and fields, stabilizing at about 60% market share. As of 2021, global natural rubber production was 13.812 million tons, while synthetic rubber production was about 15.81 million tons, indicating similar production levels for both.
Despite continual advancements in technology and synthetic rubber performance, why hasn’t it completely replaced natural rubber? This perplexing and crucial question arises even as each synthetic rubber manufacturer touts their product’s superior performance, claiming it far surpasses natural rubber. This indicates that natural rubber still has many irreplaceable comprehensive performance advantages.
Natural rubber, a product of nature, has a molecular chain structure and chemical composition far more complex than industrially synthesized products, a level of complexity current technology cannot fully replicate.
Key advantages of natural rubber include:
- Larger molecular weight and more complex structure: Natural rubber’s superior elasticity and wear resistance are primarily attributed to its longer and more complex molecular chain structure. These large molecular chains intertwine tightly, providing excellent strength, wear resistance, and tear resistance. Under external force, these molecular chains compress and then return to their original structure, exhibiting outstanding elasticity.
- More uniform molecular chain structure: The main component of rubber, polyisoprene, has various isomers in its polymer chain. In natural rubber, 100% is the cis-1,4 structure, offering stable and uniform performance. In contrast, artificially synthesized rubber cannot achieve this level of molecular internal structure uniformity.
- Positive effects of unknown components: Besides rubber molecules, natural rubber contains proteins, fatty acids, sugars, and other components. Although these are present in small quantities, they may positively impact rubber’s properties. For example, natural rubber usually withstands low temperatures, but ordinary synthetic rubber might harden and become brittle in cold environments, losing elasticity.
The complementarity of natural and synthetic rubber:
In summary, natural rubber exhibits exceptionally high mechanical strength, excellent elasticity, fatigue resistance, wear resistance, corrosion resistance, insulating properties, air tightness, waterproofing, and thermal insulation capabilities. However, not all properties of natural rubber surpass those of synthetic rubber. The greatest advantage of synthetic rubber lies in its malleability. Depending on the application and required properties, specific formulations can be used to enhance certain characteristics of the rubber. For example, polyurethane rubber, a synthetic variant, shows excellent oil resistance, addressing natural rubber’s weakness in this area. Moreover, styrene-butadiene rubber (SBR) performs better in chemical corrosion resistance, butadiene rubber (BR) excels in cold resistance, wear resistance, and elasticity, chloroprene rubber is good for oil, flame, oxidation, and ozone resistance, and nitrile rubber (NBR) has good oil and aging resistance.
In practical applications, natural and synthetic rubber complement each other well. Take car tires, for instance; they are typically made from multiple layers of rubber containing both natural and synthetic varieties. Hence, at the current level of technology, it’s impossible for synthetic rubber to completely replace natural rubber. However, in certain applications, synthetic and natural rubber can substitute for each other, and the choice often depends more on their price. Natural rubber trees have a long cultivation cycle and limited production capacity, making their cost relatively fixed and usually higher than synthetic rubber. However, the price difference between the two is generally not significant, as synthetic rubber is also a capital-intensive industry with high equipment costs, long investment recovery periods, and prices closely related to upstream raw materials like oil and natural gas.
Currently, the major types of synthetic rubber with substantial global production include styrene-butadiene rubber (SBR), butadiene rubber (BR), and isobutylene-isoprene rubber (IIR). The main raw material for these rubbers is butadiene, with about 70% of global butadiene used in synthetic rubber production. Butadiene primarily comes from by-products of oil and natural gas production, so its production capacity is not particularly stable, and its price fluctuates with oil and natural gas prices. Of course, the prices of natural and synthetic rubber also affect each other.
In conclusion, both from performance and price perspectives, natural and synthetic rubber exhibit strong complementarity. Neither can fully replace the other, and with continuous advancements in new processes and technologies, their respective performance is also constantly improving. For instance, DEF Rubber, deeply rooted in the natural rubber industry, has developed unique formulations and processes that make its natural rubber sheet products focus on the high-end market. These products have distinct advantages in wear and oil resistance in wet grinding environments, making them especially suitable for use as rubber linings in various wear-resistant equipment, water-absorbent and wear-resistant strips for floor cleaning machines, and industrial wear-resistant timing belts.
