A real-time study of homogeneous nucleation, growth, and phase transformations in nanodroplets of low molecular weight isotactic polypropylene using AFM

Macromolecules (Impact Factor: 5.93). 01/2007; 40:7223-7230. DOI: 10.1021/ma070861t
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    ABSTRACT: Ellipsometry is used to measure the crystallization and melting temperature of a bidisperse blend of a crystalline-amorphous diblock copolymer. Binary blends of sphere-forming poly(butadiene-ethylene oxide) (PB-PEO) of two different molecular weights are prepared. The two PB-PEO diblocks that are used share the same amorphous majority PB block length but different crystalline PEO minority block length. As the concentration of higher molecular weight diblock in the blend is increased, the size of the PEO spherical domains swell, providing access to the full range of domain sizes between the limits of the two neat diblock components. The change in domain size is consistent with a monotonic change in both the crystallization and melting temperatures. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011
    Journal of Polymer Science Part B Polymer Physics 04/2011; 49(10):712 - 716. · 2.22 Impact Factor
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    Polymer 07/2013; 54(16):4059-4077. · 3.77 Impact Factor
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    ABSTRACT: Thin films of isotactic polypropylene (iPP) are of great economical importance and their production is quite challenging due to the need of very fast uniaxial or biaxial expansion. During the expansion, critical problems usually arise, like structure disruption, shear thinning, causing material, energy and time losses. This work aims to study the surface morphology and compare the thermal, mechanical properties of PP films irradiated by gamma ray in an acetylene atmosphere after uniaxial expansion. PP films were made by compression molding at 190 °C with cooling in water at room temperature and irradiated by gamma ray, at (5, 12.5 and 20 kGy) under acetylene atmosphere. After irradiation the samples were submitted to thermal treatment at 90 °C for 1 h and then stretched out at 170 °C using an Instron machine. The surface of PP films, pristine and modified, (i.e., irradiated), was studied using optical microscopy (OM) and scanning electron microscopy (SEM). The changes in morphology, crystallinity and tensile parameters, like yield stress, rupture stress and elongation strain of the PP with irradiation dose were investigated. The results showed some evidences of gel formation due to crosslinking and/or long chain branching induced by radiation.
    Radiation Physics and Chemistry 01/2010; · 1.38 Impact Factor


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May 26, 2014