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Oil and chemical resistance of polyurethane 1

Views: 160 Update date: Apr 08,2020

Oil resistance and chemical resistance generally refers to the generalized oil resistance including solvent resistance, which is in principle suitable for the swelling equilibrium formula proposed by Flory et al. That is to say, only expansion occurs and only swelling equilibrium occurs. Chemical resistance or chemical reagents can be understood as the stability of water and inorganic drugs. It includes not only the expansion process of polymer, but also the chemical reaction between polymer and chemical drugs (usually the aqueous solution of inorganic drugs), leading to the aging and cracking of polymer, as well as the decomposition, dissolution and extraction process of coordination agent. 


Polyurethane elastomers have good resistance to oil and non-polar solvents, and increase with the increase of polar groups, cross-linking density and intermolecular force. Therefore, it is not difficult to conclude that the grease resistance of polyester type is better than that of polyether type. In the polyester type, the concentration of ester group increased and the oil resistance increased. For the same soft segment, the grease resistance of polyurethane elastomer increases with the increase of the rigid segment and the hard segment content, that is, the higher the hardness of the elastomer, the better the oil resistance.

 

The chemical resistance of polyurethane elastomer is also good. The hardness of the elastomer increases. At room temperature, in 20% acetic acid and 50% NaOH solution, the polyε - caprolactone type, PTMG type and PPG type showed a certain resistance. However, in 50% sulfuric acid and 20% nitric acid solution, the two polyether types cannot withstand the erosion of sulfuric acid and nitric acid, only the poly ε - caprolactone type shows better resistance. This is because the hydrogen on the α - carbon atom of ether group is easily oxidized and cracked.




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