Morphology of Highly Textured E/EP Diblock Copolymers
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMICAL ENGINEERING
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A series of semicrystalline triblock copolymers EEPE, of polyethylene E and polyethylene-propylene EP were subjected to high levels of plane strain compression using a channel die. The processing was carried out at 150 deg C, a temperature which lies well above both the E block melting points 99-103 deg C and the quiescent order-disorder transitions ca. 106 deg C for these samples. The lamellar orientation relative to the specimen boundaries was determined using two dimensional small-angle X-ray scattering. Using a 2.4 MPa applied stress on the channel die, the lamellae orient parallel to the plane of shear, while processing at an applied stress of 8.0 MPa causes the lamellae to orient perpendicular to the plane of shear. Gas permeability coefficients P for He and carbon dioxide were measured at 25 deg C for EEPE 255025 specimens and compared to modeling predictions. The upper bound lamellae aligned in parallel with respect to the permeation direction and lower bound series lamellar alignment models were compared to experimental permeation data on the corresponding oriented triblock specimens.
- Polymer Chemistry
- Manufacturing and Industrial Engineering and Control of Production Systems