ISSN:
0098-1273
Schlagwort(e):
Physics
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
Melt crystallization of isotactic polypropylene (iPP), poly(ethylene oxide), poly(butene-1), and polycaprolactone in contact with various substrates (mostly polymeric) has been studied by hot stage polarizing microscopy. Nucleating abilities of surfaces have been characterized qualitatively by examining the substrate-induced morphologies of the crystallizing polymer. These morphologies have been classified into three groups, depending on whether the substrate is very active (transcrystallinity), moderately active, or inactive as a nucleating agent. The morphologies observed are temperature-dependent, changing from transcrystalline to spherulitic upon increase of the crystallization temperature. At intermediate temperatures, mixed surface morphologies (transcrystalline plus spherulitic) are observed.The concentration of titanium and aluminum catalytic residues in isotactic polystyrene (iPS) samples can be reduced by two methods, i.e., (a) fractionating the polymer and (b) chelating Ti and Al with acetylacetone. The high nucleating ability of iPS samples in the crystallization of iPP has been shown to be due to the polymer (iPS) itself, and not to Ti and Al residues. Apart from iPS, other polymers (low energy surfaces) have also been found to induce transcrystallinity.From a survey of 43 substrate-crystallizing polymer pairs, conclusions have been drawn which are relevant to the following potential factors in heterogeneous nucleation processes: (a) chemical structure, (b) crystallographic unit cell type, (c) lattice parameters, (d) crystallinity of substrate, and (e) surface energy of substrate.
Zusätzliches Material:
5 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pol.1975.180131211
