XNBR
An improved version of Nitrile Butadiene Rubber NBR is Carboxylated Nitrile Butadiene Rubber (XNBR). In this execution there are beside the sulfur bridges also carboxyl groups R-COO- on the double bond of the butadiene part. These groups will make ionic cross links with zinc Zn++ to give improved physical properties as compared to a non-carboxylated Nitrile rubber. These ionic crosslinks are formed along with sulfur links. The carboxyl groups which are needed for these extra links are distributed randomly and are present at levels of 10% or less.
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