How does rubber degrade

Natural rubber polyisoprene and other isoprene polymers, on the other hand, are susceptible to chain scission. These types of rubber are developed using polymerisation, which entails bonding multiple identical molecules — or monomers — to form a polymer. As such, their polymer main chain is liable to degrade, which is the act of chain scission, and leads to the softening of the rubber material. Some other polymers like EPDM can undergo crosslinking and chain scission.

However, crosslinking reactions tend to dominate, leading to a greater likelihood of hardening over time. FEA stress analysis illustrates whether a proposed design will function to design specifications prior to manufacturing a mould tool. This can help to prevent rubber deterioration in the long-term and provide significant cost-savings. Once you have taken delivery of your rubber products, they should generally be stored in cold, dark, dry and oxygen-free conditions to slow the effects of rubber degradation.

If you have any rubber components, particularly rubber seals, that are beginning to show signs of deterioration, fear not. Damage or weathering need not necessarily spell the end of life for a rubber seal or product, which can be costly and sometimes difficult to replace. From our own experience the natural rubber is not easily soluble in organic solvents, that is the methods of NR degradation applied for NR in latex are easier carried out in the laboratory.

Oligomers of different functionalities were obtained from natural rubber and characterized; such polymers as polyureas, crosslinked polyurethanes, polyurethane foams based on these oligomers have been synthesized and studied.

These oligomers were used for modification of the epoxy network and thermoplastic PVC polymers as well. Abrir menu Brasil.

Abrir menu. Alexander Fainleib Renata V. Pires Elizabete F. Lucas Bluma G. Soares About the authors. Degradation; depolymerization; natural rubber. Keywords: Degradation, depolymerization, natural rubber. Introduction In the current scenario, when the socio-environmental issues are the focus of lawmakers and major polluting industries, recycling of materials, especially waste, has been constantly discussed among the public, private and academia in the search for alternatives for sustainable development.

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Instead, these polymers degrade by chain scission caused by disproportionation and hydrogen abstraction. The aging of a rubber due to oxidation and heat is greatly accelerated by stress, and exposure to other reactive gases like ozone. Besides embrittlement chain hardening or softening chain scission other visible changes such as cracking, charring, and color fading is observed.

Although the general mechanism of autooxidation is well understood, the actual chain scission and crosslinking steps are often unknown. They depend on the composition of the rubber including concentration of accelerators, activators, and fillers as well as on the temperature and composition of the atmosphere.

Two possible mechanisms of thermal oxidation with subsequent chain scission or crosslinking are shown below. The process is very complex and involves several intermediates and side reactions. In general, the type of degradation chain hardening or softening depends on the chemical composition of the polymer. For example, crosslinking dominates in polybutadiene and its copolymers such as BR, SBS, NBR and in many diene rubbers with less active double bonds due to electron-withdrawing groups such as halogen e.

This includes natural rubber NR , polyisoprene IR , isobutylene isoprene rubber IIR , and any other unsaturated polymer with electron donating groups.

However, often crosslinking reactions dominate so that these rubbers harden over time. The resistance to oxidative degradation depends on many factors, including chemical composition, molecular weight, crosslink density, and type of cross-links.

Diene elastomers that have electron-donating groups attached to the diene are usually the least stable rubbers NR, IR , i. The stability of an elastomer is also affected by other ingredients in the rubber compounding formulation.

For example, under certain conditions residual cross-linkers and accelerators confined in the elastomer can decrease the thermal stability because they easily undergo thermal decomposition at elevated temperature producing radicals that are capable of accelerating thermo-oxidative degradation of the network.