Study of bundle formation during crystallization in polymer blends

Abstract

The development of texture which exists in polymer spherulites grown from single phase melts containing an appreciable amount of noncrystallizable material was investigated. This texture generally consists of lamellar bundles separated by amorphous regions, both of which are typically 0.1–1 μm thick. A space–time finite element model previously developed by us was used to simulate the growth of a group of polymer lamellae. The model determines the impurity concentration field in the melt surrounding the growing lamellae and tracks the growth of each lamella. Important variables are the initial melt concentration of noncrystallizable material, the mass diffusion coefficient of noncrystallizable species, lamellar thickness, long period, and the rate of molecular attachment at the growth front. Under certain conditions, bundles did indeed develop during the simulations. These results were used to predict bundle thicknesses. The predictions of bundle texture were compared to actual textures observed in blends of syndiotactic and atactic polystyrene. It was found both experimentally and numerically that bundle thickness was a strong function of crystallization temperature and a relatively weak function of both the initial composition of noncrystallizable species and the degree of crystallinity of the lamellar stack. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 873–888, 1998

Crystallization kinetics and crystallization behavior of syndiotactic polystyrene/clay nanocomposites

“…These silicate layers of the clay (or clay/CPC) may be randomly but not evenly distributed in the sPS matrix, so the obtained n values do not follow any trends. This result is based on isolated bundles growing in a fixed direction in a two‐dimensional spacing between silicate layers and should hold for the initial stages of spherulitic crystallization where bundles first form 25 . t 1/2 decreases exponentially with an increasing clay content or a decreasing clay/CPC ratio, indicating that the crystallization rate is faster when unintercalated clay is added.…”

Analysis of the Multistep Solidification Process in Polymer Blends

“…An enrichment of the noncrystallizable materials at interlamellar, interfibrillar, and interspherulitic regions can occur. [18][19][20][21][22][23][24] Therefore, crystallization kinetics, including both nucleation and crystal growth, of the miscible PPG/PHMS blend is extremely sensitive to supercooling, in contrast to the immiscible PPG/PHMA blend. Although the details of individual crystallization mechanisms differ, there is little doubt that crystallization kinetics are slower in miscible blends as we have found.…”

“…The crystal growth rates of miscible blends are also retarded by the need to transport crystallizable materials to the crystal growth front and push the noncrystallizable material away from the growth front. , This leads to reduction in crystal growth rates and final degree of crystallinity. An enrichment of the noncrystallizable materials at interlamellar, interfibrillar, and interspherulitic regions can occur. − Therefore, crystallization kinetics, including both nucleation and crystal growth, of the miscible PPG/PHMS blend is extremely sensitive to supercooling, in contrast to the immiscible PPG/PHMA blend. Although the details of individual crystallization mechanisms differ, there is little doubt that crystallization kinetics are slower in miscible blends as we have found.…”

Effects of Crystallization Condition of Poly(butylene succinate) Component on the Crystallization of Poly(ethylene oxide) Component in Their Miscible Blends

“…It is noteworthy that the referred suggestion of inclusion of PEO component into the interlamellar region at high T IC,PBS and the exclusion of a part of the PEO component from the interlamellar region at low T IC,PBS seems to contradict the common sense. Many reports suggested that the position distribution and segregation in crystalline blends during the crystallization of one component can be predicted from diffusion length δ: − where D is the diffusivity of the noncrystallizable species in the blend and V is the velocity of the crystallization front. If the diffusion length δ is sufficiently small, the excluded component should reside in the interlamellar region.…”