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Abstract
Small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) were used to probe the final morphology of linear and novel branched poly(ethylene terephthalate) (PET) samples having undergone shear‐induced crystallization. The branched PET samples were produced via a reactive extrusion process designed to increase the melt strength of PET and to broaden the processing options available to include extrusion blow molding and thermoforming. The highest molar mass, and, therefore, the most branched samples exhibited highly anisotropic final SAXS morphologies indicating that the semicrystalline lamellas were preferentially oriented perpendicular to the flow direction. The lower molar mass samples all displayed isotropic final SAXS morphologies indicating that chain relaxation had occurred prior to crystallization. For the high molar mass samples, chain entanglements slow the relaxation time after exposure to shear and the chain orientation induced by the shear produced an enhanced nucleation effect for the subsequent crystallization leading to faster crystallization kinetics.
Ruthenium tetroxide (RuO2) was employed successfully to provide a lamellar scale contrast for analyzing PET crystals by TEM. Long string‐like crystals were observed for all of the samples regardless of their orientation with respect to the flow direction. These crystals often displayed a significant degree of orientation over the short range. Analysis using Fourier transforms on filtered TEM images produced d‐spacings generally comparable to those obtained from the SAXS analysis, in the 100–200 Å range.
Dedicated, to Professor John L. Stanford on the occasion of his 60th birthday.
Acknowledgments
Our thanks go to the Materials Characterization staff (ME&S) at ANSTO for help with TEM data collection, in particular to Darren Attard and to Dr. David Mitchell for useful imaging discussions. We are grateful also to Visy Industries for conducting the IV testing and to the CRC for Polymers for providing the samples and for conducting the GPC and MFR tests. Access to the BM26b DUBBLE CRG beamline at the ESRF was supported by the Access to Major Research Facilities Program, grant number 03/04‐S‐27.
P. Wanrooij is grateful to ANSTO for hosting his M.Sc. degree research internship. P. Wanrooij expresses his appreciation to Dr. Ir. Jetse C. Reijenga for organizing the exchange program.
Use of the ChemMatCARS sector 15 at the Advanced Photon Source was supported by the Australian Synchrotron Research Program (grant number 03/04‐CM‐43), which is funded by the Commonwealth of Australia under the Major National Research Facilities Program. The ChemMatCARS Sector 15 is principally supported by the National Science Foundation/Department of Energy under grant number CHE0087817 and by the Illinois Board of Higher Education. The Advanced Photon Source is supported by the U.S. Department of Energy, Basic Energy Sciences, Office of Science, under Contract No. W‐31‐109‐Eng‐38.
Notes
Dedicated, to Professor John L. Stanford on the occasion of his 60th birthday.