In this study, plasticization of polylactide (PLA) with PEG-PPG-PEG triblock copolymers was examined. Two different copolymers were utilized, with molecular weight of 1100 and 1900 g mol À1 , and with PEG contents of 10 and 50 wt %, respectively. A PPG plasticizer with molecular weight of 1000 g mol À1 , close to that of PPG block in the copolymers, was also used for comparison. Melt blends containing 10 and 15 wt % of the plasticizers were prepared. Thermal properties, mechanical properties, and structure of quenched and annealed films of the blends were studied. The crystallization driven phase separation occurred in all the annealed blends but led to different structures depending on the plasticizer used. Distinct inclusions of the plasticizer were visible under the scanning electron microscope only in PLA with PPG but not in the blends of PLA with the copolymers. The drawability of the plasticized systems was improved when compared with neat PLA. In the quenched and annealed blends, elongations at break at the level of 5 and 0.7, respectively, were reached.
ABSTRACT:The process for the compatibilized blending of recycled poly(ethylene terephthalate) and recycled highdensity polyethylene with ethylene/glycidyl methacrylate copolymer was enlarged to the scale of a pilot plant. The addition of a compatibilizer effectively reduced the size of dispersed inclusions with better bonding to the matrix. The optimum contents of the compatibilizer were found to be around 4 pph. The extrusion and orientation of films from the blend were developed on an industrial scale, and the structure and properties of the obtained films were characterized. The crystalline phase of poly(ethylene terephthalate) in oriented films assumed a strong texture resulting from the plane-strain state of the deformation of the films on the industrial machinery. The origin of the texture was mostly strain-induced crystallization. The chain segments in the amorphous phase were oriented along the machine direction, but there was significant anisotropy of the chain packing in the amorphous phase in the plane perpendicular to the drawing direction, the pseudohexagonal packing of chain fragments being in register over the whole film. Such a texture of an oriented amorphous phase of poly(ethylene terephthalate) is reported here for the first time. The nonoriented and oriented films obtained with the industrial machinery showed good mechanical properties, with strengths up to 120 MPa and elongations to break of 40%.
L 6 d i , Poland
SYNOPSIST h e blends of high-density polyethylene ( H D P E ) with atactic polystyrene (PS) were deformed plastically by plane-strain compression in a channel die. The samples were deformed up t o the true strain 1.8 (compression ratio 6) in three temperature regimes: below, near, and above the glass transition temperature of polystyrene component. T h e morphology and the texture of crystalline component in the deformed blend samples were investigated by means of scanning electron microscopy and wide angle X-ray diffraction (pole figures technique). It was found t h a t the deformation process in the blend of immiscible H D P E and PS does not differ markedly from the deformation of the one-component system from the point of view of the deformation mechanisms involved. T h e crystalline textures of the blend samples are qualitatively the same as in the plain H D P E deformed under similar conditions. T h e active deformation mechanisms are the same in deformation of both the plain H D P E and H D P E / P S blend. T h e mechanism identified are crystallographic slips: (100)[001], (100)[010], a n d (010[001] supported by the interlamellar slip. T h e presence of PS in blends modifies t o some extent the deformation process and resulting orientation of the crystalline component of H D P E by modification of the stress distribution within H D P E matrix around PS inclusions. This influence is much stronger a t low deformation temperatures, when PS is in a glassy state, t h a n at temperatures above Tg of PS. 0 1996 John Wiley & Sons, Inc.
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