Microstructure and Crystal-Amorphous Interphases in Melt-Miscible Semicrystalline Polymer Blends. Ph.D. Thesis
Small-angle x ray scattering, differential scanning calorimetry, dielectric spectroscopy and dynamic mechanical thermal analysis were performed to study the microstructure of the semicrystalline polymers poly(etylene oxide) (PEO) and poly (epsilon-caprolactone) (PCL) as well as several melt miscible blends. Four amorphous polymers were blended with PEO: two which interact weakly with PEO poly(methyl methacrylate) (PMMA) and poly(vinyl acetate) (PVAc) and two which are considered strongly interacting due to the formation of hydrogen bonds with PEO (two random copolymers, one containing 50% styrene and 50% hydroxystyrene (50/50 ScHS) and another of ethylene with 55% methacrylic acid (EMA55)). Further, one of the weakly interacting amorphous polymers and one of the strongly interacting polymers was selected based on its relatively high T(sub g)s. The other amorphous polymers have relatively low T(sub g)s (i.e., at or below the crystallization temperature). The solid state microstructure of miscible blends containing a semicrystalline and an amorphous polymer is shown to be critically dependent on two factors: (1) the strength of interactions between the two copolymers; and (2) the mobility of the amorphous material at the crystallization temperature. The influence of interaction strength on the region of partial order at the crystal surface (the crystal-amorphous interphase) is demonstrated. The results are consistent with theoretical predictions that this region changes from pure crystallizable material to a mixture containing both the crystalizable and the amorphous components as chi becomes more favorable. In the blends which contain a high T(sub g) amorphous polymer and in those with strong intermolecular interactions, there were no observed changes in the microstructure with crystallization temperature. Apparently, in the high T(sub g) systems, the amorphous polymer is unable to escape the interlamellar zone since it has insufficient mobility.
- Research Organization:
- Pennsylvania State Univ., University Park, PA (United States). Davey Lab.
- OSTI ID:
- 237301
- Report Number(s):
- N--96-22620; NIPS--96-34115
- Country of Publication:
- United States
- Language:
- English
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