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Trans ‐ and Dimethyl quinacridone nucleation of isotactic polypropylene
Author(s) -
Sterzynski T.,
Calo P.,
Lambla M.,
Thomas M.
Publication year - 1997
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.11842
Subject(s) - materials science , nucleation , tacticity , polypropylene , phase (matter) , spherulite (polymer physics) , composite material , polymer , polymer chemistry , thermodynamics , polymerization , chemistry , organic chemistry , physics
Isotaclic polypropylene (iPP) was nucleated specifically for structural and mechanical studies, especially of impact resistance. Nucleation was accomplished by two red pigments: a linear trans ‐quinacridone dye (as β‐phase nucleator) and a dimethyl quinacridone resulting in the formalion of a pure α‐phase structure. This procedure allowed the comparison of both the crystal structure and the morphology of the polymer. For the β‐nucleated iPP, by means of the WAXS measurements in the transmission mode, a maximum of the k‐value (fraction of β‐phase) was found for a concentration of 5 × 10 −5 wt% of the trans‐quinacridone. By means of polarized light microscopy (PLM), the mold temperature and pigment concentration dependent spherulites distribution on the cross section of the samples was observed. DSC permitted confirmation of the WAXS measurements, giving a characteristic double melting peak for the β polypropylene. By isothermal WAXS measurements the temperature of 135°C as the upper limit of the β phase was detected. For both nucleating agents (linear trans ‐quinacridone and dimethyl quinacridone) the dependence of the mechanical properties (modulus of elasticity and brittleness by impact resistance) on the pigment concentration was observed. For the β‐phase iPP the highest ductility by impact testing corresponds to the highest values of the k parameter. The explanation is based on the SEM observations, which permitted the detection of spherulites with cross‐hatched lamellae (for the α‐spherulites) and with simple radial growth lamellae for the β‐spherulites.