USAXS/SAXS/XRD From HDPE plaques showing spherulitic (low-q), lamellar (intermediate-q) and crystallographic (high-q) features. Unified fit is also shown.
Crystalline Polymers: Current Funding, P&G Miami Valley Labs (50K/year), Quantum Chemical Corporation (21K/year).
Students: Shrish Rane, PhD Candidate
ranesy@email.uc.edu
Shrish Rane.html
C1: Nano-Structured, Semicrystalline Polymer Foams, Beaucage, G.; Aubert, J. H.; Lagasse, R. R.; Schaefer, D. W.; Rieker, T. P.; Ehrlich, P.; Stein, R. S.; Kulkarni, S.; Whaley, P. D. J. Polym. Sci., Part B: Polym. Phys. (1996), 34(17), 3063-3072.
C2: Isotatic Polypropylene Foams Crystallized from Compressed Propane Solutions, P. D. Whaley, S. Kulkarni, P. Ehrlich, R. S. Stein, H. H. Winter, G. Beaucage, Submitted Macromolecules 1997.
C3: Crystallinity of Fully Aromatic Thermotropic Polyesters of 3,3'-bis(Phenyl)-4,4'-Biphenol and 1, 1'-Binaphthyl-4,4'-Diol, P. K. Bhowmik, G. Beaucage, J. Polym. Sci., Part B: Polym. Phys., 32, 1023-31 (1994).
C4: A Bragg Analogy for Spherulitic-Crystalline Banding, G. Beaucage, Submitted J. Crystal Growth, 1997.
1) Chlorinated polyethylene/PE Metallocenes. Our efforts in studying the morphology of crystalline polymers began with a CRADA with Dow Chemical while at Sandia which dealt with the morphology of low crystallinity systems. The results of these studies showed that the nano-scale structure of low-crystallinity polymers can display rod-like features in scattering as opposed to lamellar features. One-dimensional regimes can be observed both in metallocene elastomers as well as in CPE systems. In CPE strong evidence for phase separation exists. Most of the details of these studies are proprietary.
2) Semi-crystalline Polymer Foams. Low-density polymer foams for application as battery electrodes and as fusion targets are formed from semi-dilute solutions and supercritically dried after a solvent exchange process. These materials were originally thought to display mass-fractal scaling. Our work in this area has revealed that the structure is actually lamellar on a nano-scale [C1, 2]. It is interesting that these lamellae do not correlate, so that a correlation peak is absent in the small-angle scattering regime. This work proposes that the correlation of lamellae may be related to entanglements present in the melt which are essentially absent when crystallization occurs in semi-dilute conditions.
3) HDPE/LDPE/LLDPE. Extensive studies (much proprietary) have been carried out aimed at correlating orientation in blown films with mechanical and transport properties. The most successful of these involves a direct and linear correlation between moisture vapor transmission and orientation of lamellae observed in SAXS for HDPE blown films. For this work, the Hermans orientation function was calculated from 2-D SAXS patterns.
4) Biosource Polyesters. We have been working for about 2 years on polyesters derived from biosources with P&G's MVL facility. Most of this work is proprietary. Interesting structural features have been observed by combining SALS, SAXS and XRD in these systems. Structures intermediate between spherulitc and lamellar sizes seems to govern mechanical features of these systems. This is evidenced in blends of tactic and atactic PHB for example [paper in preparation]. There is also a correlation between the goodness of banding in these materials and this sub-spherulitic structure. Comparison with electron microscopy has revealed that the sub-spherulitic structure is related to regular clusters of lamellae.
|
Aero-Sol-Gel Reactor (ASG) |
|
|
This Page |