Effect of the initial morphology of isotactic polypropylene on the characteristics of its structural rearrangement during extension in liquid media

Shmatok, Ye.A.; Kalinina, S.V.; Аржакова, О.В.; Yaysheva, L.M.; Волынский, А. Л.; Bakeyev, N.F.

doi:10.1016/0032-3950(90)90180-e

Cited by 1 publication

(2 citation statements)

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“…In contrast to amor phous polymers, PP is able to undergo both modes of solvent crazing and the mode of solvent crazing depends on the type of crystalline structure of the ini tial polymer [11]. As was shown in [12][13][14], isotactic PP with its highly disordered smectic crystalline struc ture (initial PP) undergoes deformation in the pres ence of adsorptionally active liquid environments (AALE) via classical solvent crazing. Annealing of iso tactic PP increases its degree of crystallinity and assists its gradual transition into the monoclinic crystalline modification [15].…”

Section: Resultsmentioning

confidence: 99%

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Visualization of structural rearrangements during annealing of solvent-crazed isotactic polypropylene

et al. 2009

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Structural rearrangements taking place upon the annealing of solvent crazed isotactic PP are studied by the direct microscopic method. Independently of the type of its crystalline structure, solvent crazed PP undergoes shrinkage in a wide temperature interval, starting even from room temperature and up to its melting temperature. This shrinkage is a result of the structural processes in crazes and proceeds via shutting down of the walls of individual crazes. This low temperature shrinkage of solvent crazed PP is assumed to have an entropy nature. This process involves the contraction of extended polymer chains and their transition into thermodynamically favorable conformations. This contraction is allowed because, upon annealing, the entropy contracting force increases. As a result, the crystalline framework of oriented PP melts down (amorphization), extended chains appear contracted, stored stresses relax, and subsequent recrystalli zation in the unstressed state takes place.

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Section: Resultsmentioning

confidence: 99%

“…The above structural rearrange ments of PP entail concomitant changes in the mech anism of its deformation in AALE. Annealed PP [12][13][14] is characterized by its relatively high degree of crystallinity and experiences so called delocalized sol vent crazing [11].…”

Section: Resultsmentioning

confidence: 99%