TIT# SAXS Investigation of Structure-Property Relationship of
     Polypropylene/Montmorillonite Nanocomposites During Load-Cycling
AUT# Zeinolebadi, Ahmad; Stribeck, Norbert; Vuluga, Zina; Schloen, Christoph;
     Botta, Stephan; Ganjaee Sari, Morteza;
SOU# Polym. Adv. Technol. (2013), 24(8), 693-704
LOC# xv137
CLA#
COM# in print 130401 DOI: 10.1002/pat.3132
APP#
MAT#
ABS# Polypropylene (PP) can hardly be reinforced by the layered silicate
     montmorillonite (MMT), but the materials fatigue appears somewhat reduced.
     The probable reason is amplified competitive nucleation of the PP by MMT
     dust -- a fall-out of mechanical exfoliation. Utilizing small-angle X-ray
     scattering (SAXS) from synchrotron we investigate the nanostructure
     evolution of the PP in straining experiments from neat PP and
     compatibilized nanocomposite materials. The compatibilizer is a
     styrene-ethylene-butylene-styrene copolymer (SEBS). Oriented
     injection-molded test bars are studied. The discrete SAXS probes
     variations of sizes and distances among those crystalline domains that
     are not placed at random. Crystallite dimensions and distances are
     documented for modelling purposes. The nanoscopic strain is computed from
     the distance variation and compared to the macroscopic strain. Differences
     between macroscopic and nanoscopic strain are observed. They require to
     postulate regions with statistical placement of crystallites (poorly
     arranged region, PAR) in addition to the SAXS-probed well-arranged
     entities (WAE). The extensibility of WAEs must be different from that of
     the PARs. In neat PP the observed WAEs are well developed and stronger
     than the PARs. In the composites the WAEs are made from thin and less
     extended crystalline domains. They are weaker than the PARs that appear
     reinforced. Thus, enclosing each MMT layer a PARs is formed and the WAEs
     generated farther away remain imperfect. Consequently, in the composites
     the narrow crystalline domains from the WAEs do not break into even
     smaller pieces and the fatigue of the composites is lower than that of
     the neat PP.