The molecular structure of fatty acid esters also affects the compatibility.
The changes in mass, volume and mechanical properties
of NBR decrease with the increase of carbon chain length, while
increase with number of double bonds in the esters. The mechanical
properties of NBR immersed in methyl ester experienced
slightly larger decrease than that immersed in ethyl ester. The fatty
acid methyl ester with shorter carbon chain and double bonds has
higher solvent power.
Thus, the composition of biodiesel could be modified and optimized
during the production process through the adoption of new
techniques or using appropriate mix of feedstocks to improve its
compatibility with an elastomer.