POLY(4-METHYLPENTENE-1) HYDROGENATED OLIGO(CYCLOPENTADIENE) BLENDS - MISCIBILITY, TENSILE STRESS-STRAIN, AND DYNAMIC-MECHANICAL BEHAVIORS

This article discusses the influence of the oligomeric resin, hydrogen ated oligo (cyclopentadiene) (HOCP), on the morphology, and thermal an d tensile mechanical properties of its blends with isotactic poly(4-me thylpentene-1) (P4MP1). The P4MP1 and HOCP are found not miscible in t he melt state. P4MP1/HOCP blends after solidification contain three ph ases: the crystalline phase of P4MP1, an amorphous phase of P4MP1, and an amorphous phase of HOCP. From optical micrographs obtained at 150 degrees C, it is found that the solidified blends show a morphology co nstituted by P4MP1 microspherulites and small HOCP domains homogeneous ly distributed in intraspherulitic regions. DSC and DMTA results show that the blends present two glass transition temperatures (T-g) equal to the T(g)s of the pure components. The tensile mechanical properties have been investigated at 20, 60, and 120 degrees C. At 20 degrees C both the HOCP oligomer and the amorphous P4MP1 are glassy, and it is f ound that all the blends are brittle and the stress-strain curves have equal trends. At 60 degrees C the HOCP oligomer is glassy, whereas th e amorphous P4MP1 is rubbery. The tensile mechanical properties at 60 degrees C are found to depend on blend composition. It is found that t he Young's modulus, the stresses at yielding and break points slightly decrease with HOCP content in the blends and these results are relate d to the decrease of blend crystallinity. The decrease of the elongati on at break is accounted for by the presence of glassy HOCP domains th at act as defects in the P4MP1 matrix, hampering the drawing. At 120 d egrees C both the amorphous phases are rubbery. It is found decreases of Young's modulus, stresses at yielding and break points. These resul ts have been related to the decrease of blend crystallinity and to the increase of the total rubbery amorphous phase. Moreover, it is found that the blends present elongations at break equal to that of pure P4M P1. This constancy is attributed to: (a) at 120 degrees C the HOCP dom ains are rubbery and their presence seems not to disturb the drawing o f the samples; (b) a sufficient number of the tie-molecules and entang lements of P4MP1 present in the blends. In fact, although the numbers of tie-molecules and entanglements decrease in the blends, increasing the HOCP oligomer, they seem to be enough to keep the material interla ced and avoid earlier rupture. (C) 1997 John Wiley & Sons, Inc.