Polyhedral oligomeric silsesquioxanes (POSS) as functional additives to modify mechanical, rheological and thermal properties of carboxylated butadiene-acrylonitrile rubber/poly(ε-caprolactone)/blend XNBR/PCL

Carboxylated nitrile rubber/poly(ε-caprolactone) XNBR/PCL blends with various XNBR-to-PCL weight ratios were prepared by melt mixing method. The poly(ε-caprolactone) PCL phase influenced the complex viscosity η* of XNBR/PCL blends, and the processing at 100 °C was facilitated. Poly(ε-caprolactone) PCL acted as a reinforcement, and static and dynamic mechanical properties of XNBR/PCL blend were improved. The increased values of the tensile strength TS and the storage modulus G′ were reported as PCL content increased. Changes of the glass transition T_g of both phases, XNBR and PCL, indicated the strong interfacial adhesion between both components of blend. Carboxylated nitrile rubber/poly(ε-caprolactone) XNBR/PCL blend with 80:20 weight ratio of XNBR to PCL was selected and modified by the polyhedral oligomeric silsesquioxanes POSS to enhance mechanical properties. For this purpose, three various functional groups of POSS able to form interactions with carboxylic groups of nitrile rubber XNBR were selected: trisilanolisooctyl-POSS (HO-POSS), aminopropylisobutyl-POSS (Amine-POSSS), glycidyl-POSS (Gly-POSS). For all selected POSS, the plasticizing effect at 100 °C was determined, and the complex viscosity η* decreased. Reinforcing impact of POSS was observed. The increase of storage modulus G′ resulted from interphase polymer/filler interactions. Glycidyl-POSS (Gly-POSS) almost double enhanced tensile strength TS of XNBR/PCL blend, from 1.14 ± 0.05 to 2.26 ± 0.29 MPa. Incorporation of POSS influenced the glass transition temperature T_g of PCL phase. The better thermal stability of the blend modified by glycidyl-POSS up to temperature of 250 °C and lower weight loss were observed. Negative impact of selected POSS on the degree of crystallinity of PCL phase was detected.