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Title: The Effect of Filler-Polymer Interactions on Cold-Crystallization Kinetics in Crosslinked, Silica Filled PDMS/PDPS Copolymer Melts.

Abstract

Crystallization in a series of variable crosslink density poly(dimethyl-diphenyl) siloxanes random block copolymers reinforced through a mixture of precipitated and fumed silica fillers has been studied by Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), and X-ray Diffraction (XRD). The silicone composite studied was composed of 94.6 mol% Dimethoylsiloxane, 5.1 mol% diphenylsiloxane, and 0.3 mol% methyl-vinyl siloxane (which formed crosslinking after a peroxide cure). The polymer was filled with a mixture of 21.6 wt. % fumed silica and 4.0 wt. % precipitated silica previously treated with 6.8 wt. % ethoxy-endblocked siloxane processing aid. The base composite was characterized by a molecular weight between crosslinks in the polymer network of {approx}24 kDa and an overall molecular weight (including the influence of the silica fillers) between crosslinks of {approx}11 kDa. Molecular weight between crosslinks and filler-polymer interaction strength were then modified by exposure to {gamma}-irradiation in either air or vacuum. The unirradiated material exhibited crystallization at -80 C as measured by DSC with a 16% crystallization as measured by XRD. Isothermal DMA experiments illustrated that crystallization at -85 C occurred over a 1.8 hour period in silica-filled systems and 2.2-2.6 hours in unfilled systems. The onset of crystallization typically occurred after amore » 30-minute incubation/nucleation period. The crystallization kinetics were dependent on crosslink density. Changes in molecular weight of a factor of two did not, however, change the amount of crystallization. Irradiation in vacuum resulted in faster overall crystallization rates compared to air irradiation for the same crosslink density, likely due to a reduction in the interaction between the polymer chains and the silica filler surface. Modulated differential scanning calorimetry contrasted the crystallization and melting behavior of pure PDMS versus the PDMS/PDPS base copolymer and helped determine which component of the composite was the origin of the crystallization phenomena.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
897925
Report Number(s):
UCRL-JRNL-220857
TRN: US200706%%128
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Journal of Polymer Science, Part B: Polymer Physics, vol. 44, no. 13, July 1, 2006, pp. 1898-1906
Additional Journal Information:
Journal Name: Journal of Polymer Science, Part B: Polymer Physics, vol. 44, no. 13, July 1, 2006, pp. 1898-1906
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; CALORIMETRY; COPOLYMERS; CRYSTALLIZATION; FILLERS; IRRADIATION; KINETICS; MELTING; MIXTURES; MOLECULAR WEIGHT; ORIGIN; PEROXIDES; POLYMERS; PROCESSING; SILICA; SILICONES; SILOXANES; X-RAY DIFFRACTION

Citation Formats

Chien, A, DeTeresa, S, Thompson, L, Cohenour, R, Balazs, B, and Maxwell, R S. The Effect of Filler-Polymer Interactions on Cold-Crystallization Kinetics in Crosslinked, Silica Filled PDMS/PDPS Copolymer Melts.. United States: N. p., 2006. Web.
Chien, A, DeTeresa, S, Thompson, L, Cohenour, R, Balazs, B, & Maxwell, R S. The Effect of Filler-Polymer Interactions on Cold-Crystallization Kinetics in Crosslinked, Silica Filled PDMS/PDPS Copolymer Melts.. United States.
Chien, A, DeTeresa, S, Thompson, L, Cohenour, R, Balazs, B, and Maxwell, R S. Fri . "The Effect of Filler-Polymer Interactions on Cold-Crystallization Kinetics in Crosslinked, Silica Filled PDMS/PDPS Copolymer Melts.". United States. https://www.osti.gov/servlets/purl/897925.
@article{osti_897925,
title = {The Effect of Filler-Polymer Interactions on Cold-Crystallization Kinetics in Crosslinked, Silica Filled PDMS/PDPS Copolymer Melts.},
author = {Chien, A and DeTeresa, S and Thompson, L and Cohenour, R and Balazs, B and Maxwell, R S},
abstractNote = {Crystallization in a series of variable crosslink density poly(dimethyl-diphenyl) siloxanes random block copolymers reinforced through a mixture of precipitated and fumed silica fillers has been studied by Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), and X-ray Diffraction (XRD). The silicone composite studied was composed of 94.6 mol% Dimethoylsiloxane, 5.1 mol% diphenylsiloxane, and 0.3 mol% methyl-vinyl siloxane (which formed crosslinking after a peroxide cure). The polymer was filled with a mixture of 21.6 wt. % fumed silica and 4.0 wt. % precipitated silica previously treated with 6.8 wt. % ethoxy-endblocked siloxane processing aid. The base composite was characterized by a molecular weight between crosslinks in the polymer network of {approx}24 kDa and an overall molecular weight (including the influence of the silica fillers) between crosslinks of {approx}11 kDa. Molecular weight between crosslinks and filler-polymer interaction strength were then modified by exposure to {gamma}-irradiation in either air or vacuum. The unirradiated material exhibited crystallization at -80 C as measured by DSC with a 16% crystallization as measured by XRD. Isothermal DMA experiments illustrated that crystallization at -85 C occurred over a 1.8 hour period in silica-filled systems and 2.2-2.6 hours in unfilled systems. The onset of crystallization typically occurred after a 30-minute incubation/nucleation period. The crystallization kinetics were dependent on crosslink density. Changes in molecular weight of a factor of two did not, however, change the amount of crystallization. Irradiation in vacuum resulted in faster overall crystallization rates compared to air irradiation for the same crosslink density, likely due to a reduction in the interaction between the polymer chains and the silica filler surface. Modulated differential scanning calorimetry contrasted the crystallization and melting behavior of pure PDMS versus the PDMS/PDPS base copolymer and helped determine which component of the composite was the origin of the crystallization phenomena.},
doi = {},
journal = {Journal of Polymer Science, Part B: Polymer Physics, vol. 44, no. 13, July 1, 2006, pp. 1898-1906},
number = ,
volume = ,
place = {United States},
year = {2006},
month = {4}
}