ISSN:
1435-1536
Keywords:
New crystallization
;
β-modification of poly-propylene
;
β→α-modification transition
;
self nuclei
;
structural memory effect
;
spherulites
;
trans crystallization
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The new crystallization of β-modification of polypropylene (β-PP) was studied after melring as a function of the final temperature of fusion (T F ). The new crystallization, thermal characteristics, polymorphic composition, and structure of recrystallized samples were highly influenced by theT F level. As a function ofT F , three characteristic regions were outlined: Region I below the melting point of β-modification, region II between the melting points of β- and α-modifications, and region III above the melting point of α-modification. In the vicinity of the melting points of both modifications, two narrow transition regions are observed where the crystallization and structural characteristics changed abruptly withT F . AtT F values in region I, recrystallization of β-modification proceeded without any change in the modification. IfT F fell in region II, the sample crystallized newly into α-modification. The optically negative β-ring-spherulites were replaced by positive microclusters of α-modification and a marked structural memory effect was observed. In region III, the above characteristic became invariant withT F (region of blank melt). These observations may be interpreted by the role of self nuclei.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00657402
