Component Stress−Strain Behavior and Small-Angle Neutron Scattering Investigation of Stereoblock Elastomeric Polypropylene

Abstract

Elastomeric polypropylene (ePP) produced from unbridged 2-arylindene metallocene catalysts was studied by uniaxial tensile and small-angle neutron scattering (SANS) techniques. The ePP can be separated into the following: a low tacticity fraction soluble in ether (ES), an intermediate tacticity fraction soluble in heptane (HS), and a high tacticity fraction insoluble in heptane (HI). Tensile properties of ePP were compared to its solvent fractions, and the role of each solvent fraction residing within ePP was investigated by blending 5 wt % deuterated fraction with ePP. The tensile properties of each fraction vary considerably, exhibiting properties from a weak gum elastomer for ES, to a semicrystalline thermoplastic for HI. The intermediate tacticity HS fraction exhibits elastic properties similar to the parent elastomer (ePP). In the melt at 160 °C, SANS shows that all deuterated fractions are homogeneously mixed with ePP. Slow cooling from the melt to 25 °C causes the low tacticity fraction to preferentially segregate in amorphous domains due to different crystallization temperatures and kinetics although, despite its low crystallinity (≤2%), the low tacticity fraction can cocrystallize with the matrix. The dES-ePP shows little or no relaxation when held under strain and recovers readily upon the release of stress. The high tacticity component (dHI-ePP) retains its plastic properties in the blend.

A Rheo-Optical FTIR Spectrometer for Investigating Molecular Orientation and Viscoelastic Behavior in Polymers

“…In situ birefringence and X-ray scattering data for ePP show a crystalline-to-mesomorphic microstructural transformation as the film is tensile drawn, similar to sPP [77][78][79][80] . In addition to confirming the presence and orientation behavior of iPP crystal morphs and mesomorphs (as observed with rheo-birefringence, small-angle, and wide-angle X-ray scattering), the rheo-FTIR spectrometer will provide equivalent information for the amorphous atactic segments simultaneously.…”

Soft Matter Sample Environments for Time-Resolved Small Angle Neutron Scattering Experiments: A Review

“…Th situation when the materials are unclamped and allowed to molecularly rela ation of isotopic blends of linear polyethylene and ethylene copolymers w hexyl was studied, but due to the relatively small amount of material in the n (intrinsic to this type of deformation experiments), data could only be obtai time intervals. An extensive discussion on how the anisotropy manifests its ing patterns, due to the molecular and domain orientation induced by apply mation, can be found in experiments of elastomeric polypropylene [70].…”

Partially bio-based thermoplastic elastomers by physical blending of poly(hydroxyalkanoate)s and poly(ethylene-co-vinyl acetate)

“…These results indicate good elasticity and rubbery characters of the blends. Meantime, the PHBM/EVA90 blends exhibit notable stress-strain hysteresis which is a characteristic feature of thermoplastic elastomers [23] The lower content of the EVA90 the more remarkable hysteresis. It is also noticed that the hysteresis mainly occurs in the first hysteresis stress-strain cycle since the second and third cycles are close to each other (the 3 rd cycle is not shown here to make the curves more readable).…”