Structure and deformation of an elastomeric propylene–ethylene copolymer

Abstract

The elastic behavior of a propylene-ethylene copolymer was investigated. An initial ''conditioning'' tensile extension up to 800% strain resulted in an elastomer with low initial modulus, strong strain hardening, and complete recovery over many cycles. Structural changes that occurred in the low crystallinity propylene-ethylene copolymer during conditioning, and that subsequently imparted elastomeric properties to the conditioned material, were investigated. Thermal analysis, wide and small angle X-ray diffraction, and atomic force microscopy measurements were performed at various strains during the conditioning process. Conditioning transformed crystalline lamellae into shish-kebab fibers by melting and recrystallization. The fibers, accounting for only 5% of the bulk, were interconnected by a matrix of entangled, amor-phous chains that constituted the remaining 95%. It was proposed that the shish-kebab fibers acted as a scaffold to anchor the amorphous rubbery network. Entanglements of the amorphous chain segments acted as network junctions and provided the elastic response. The stress-strain response of materials conditioned to 400% strain or more was described by the classical rubber theory with strain hardening. The extracted value of M c , the molecular weight between network junctions, was intermediate between the entanglement molecular weights of polypropylene and polyethylene.

Enzymatic Synthesis and Chemical Recycling of Novel Polyester-Type Thermoplastic Elastomers

“…The degree of crystallinity decreases with increasing content of soft segments; thus, the polymer changes from a rigid plastic to a soft elastomer [1][2][3].…”

Neuronal Differentiation of Embryonic Stem Cell Derived Neuronal Progenitors Can Be Regulated by Stretchable Conducting Polymers

“…Strain hardening of the SEBS leads to further increase in the stiffness of the substrates upon application of strain, the surface of elastomeric polymer SEBS is quite stiff (*2 MPa) in comparison to the natural environment in which neurons grow. 31,50 The changes in the stiff CP and pristine SEBSsubstrates do not lead to large variations in the formation and maturation of focal adhesion complexes which are primary effectors of cytoskeletal arrangement and other downstream signaling events like cell adhesion and differentiation. CP SEBS substrates allow potential development of implantable electrodes by providing a mechanical environment whose surface conductance can be modulated by application of strain.…”

Quantitative probing the interfacial structure of TPO/CPO blends by transmission electron microscopy via EDX

“…The crystalline lamellae traverse the iPP and EB9 phases and appear to remain in registry as they cross these domains. Both Bates et al [23] and Hiltner et al [24] have reported this type of phenomenon previously for blends of iPP with metallocene polyethylene (mPE) copolymer. They attributed the strength of the bond between the two components to the formation of entanglements at the iPP/mPE crystal/crystal interface.…”