No abstract

The tensile and thermal properties of linear poly(styrene-b-isobutylene-b-styrene) (L_SIBS) and styrenic copolymers with a dendritic polyisobutylene core (D_SIBS) filled with 10 – 30 wt% of organophilic montmorillonite nanoclays (Cloisite(®)-20A) via solution blending were investigated. D_SIBS polymers were successfully reinforced by the clays without additional compatibilizers to show increase in both modulus and ultimate tensile strength. The clay platelets were well dispersed in the polymer matrix as determined by transmission electron microscopy (TEM). However, L_SIBS composites displayed decreasing tensile strength with increasing clay loading. TEM found clay agglomerates in L_SIBS composites that can act as “hotspots” for premature failure of the material. D_SIBSs loaded with 60 phr (37.5 wt%) carbon black (N234) also showed significant reinforcement. Interestingly, a D_SIBS with 17 wt% hard phase content reinforced with 60 phr carbon black exhibited an increase in the glass transition temperature of the hard phase from 116 °C to 126 °C. This will make steam sterilization of the material possible for biomedical applications.

Poly(aliphatic/aromatic-ester) (PED) multiblock copolymers belong to the class of thermoplastic elastomers (TPEs), characterized by a physical network of semi-crystalline hard segments. The PEDs were modifi ed with e-beam to create an additional network structure. Polymers were evaluated using SEC, WAXS, DSC and quasi-static tensile tests. E-beam irradiation induced a signifi cant increase of molecular weight and tensile strength of the PEDs. This effect, together with the diminished degree of crystallinity can be explained by the formation of chemical crosslinks, which are located in the hard phase segments.