Enhancing the air impermeability of a biobased poly(di-isoamyl itaconate-co-isoprene) elastomer via the cocoagulation of latex and natural layered silicates

The gas-barrier properties of elastomer are of particular importance, especially for airtight applications. Poly(di-isoamyl itaconate-co-isoprene) (PDII) is a newly invented and respectable biobased elastomer, but the barrier properties of PDII and its composites with carbon black and silica are not satisfying at all. Because there are abundant ester groups in PDII macromolecules and these groups can contribute to the homogeneous dispersion of layer silicates, we applied layered silicates, including montmorillonite (MMT) and rectorite (REC), into the PDII matrix to improve the air impermeability. MMT/PDII and REC/PDII composites were prepared by a cocoagulation method, and the air impermeability of the PDII elastomer was highly improved. The smallest gas permeability index reached 1.7 × 10^-17 m² Pa^-1 s^-1 at an REC content of 80 phr; this implied a reduction of 85.5%. A comparison of the two types of silicate/PDII composites showed that the MMT/PDII composites had better properties at low filler contents, whereas the REC/PDII composites had better mechanical and gas-barrier properties at high filler contents. Other structures and properties of the composites were investigated by X-ray diffraction, transmission electron microscopy, and dynamic mechanical rheology.