Journal ArticleDOI
Model networks of end‐linked polydimethylsiloxane chains. XII. Dependence of ultimate properties on dangling‐chain irregularities
Anthony L. Andrady,M. A. Llorente,M. A. Sharaf,R. R. Rahalkar,James E. Mark,J. L. Sullivan,C. U. Yu,James Robert Falender +7 more
TLDR
In this paper, the tetra-functional end-linking agent Si[OSi(CH3)2H]4 was used in varying amounts smaller than that corresponding to a stoichiometric balance between its active hydrogen atoms and the chain vinyl groups.Abstract:
Elastomeric networks were prepared by end-linking vinyl-terminated polydimethylsiloxane (PDMS) chains having number-average molecular weights of 11.3 × 103 g mol−1. The tetra-functional end-linking agent, Si[OSi(CH3)2H]4, was used in varying amounts smaller than that corresponding to a stoichiometric balance between its active hydrogen atoms and the chain vinyl groups. The number of dangling-chain irregularities thus introduced into the networks was directly determined by iodometric titration for unreacted vinyl groups. The (unfilled) PDMS networks thus obtained were studied in elongation to their rupture points at 25°C (a temperature sufficiently high to prevent complications from strain-induced crystallization), and in swelling equilibrium in benzene at room temperature. Small to moderately large proportions of dangling chains were found to have less of an effect on the elongation modulus than might be expected, and similarly a relatively small effect on the degree of equilibrium swelling. Most importantly, comparisons of constant values of the high deformation modulus show that dangling-chain irregularities decrease both the maximum extensibility of a network and its ultimate strength.read more
Citations
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Book ChapterDOI
The use of model polymer networks to elucidate molecular aspects of rubberlike elasticity
TL;DR: In this article, the authors used highly selective cross-linking reactions instead of the usual indiscriminate joining of chain segments (such as occurs in sulfur or peroxide cures or in high energy irradiations) to investigate the dependence of a variety of elastomeric properties on network structure.
Journal ArticleDOI
Cross-Link Density Estimation of PDMS Networks with Precise Consideration of Networks Defects
TL;DR: In this article, a series of randomly cross-linked poly(dimethylsiloxane) (PDMS) networks with systematically varying and well-defined dangling chain and defect content were investigated by 1H double-quantum low-field NMR (DQ NMR), equilibrium swelling, and high-resolution magic-angle spinning NMR experiments in order to obtain information about the absolute molecular weight of the polymer chains between two cross-links, Mc, and its distribution.
Journal ArticleDOI
Segmented organosiloxane copolymers: 2 Thermal and mechanical properties of siloxane—urea copolymers
TL;DR: In this article, Amino-propyl terminated poly(dimethylsiloxane) oligomers were reacted with various diisocynates to form segmented copolymers with urea linkages.
Journal ArticleDOI
Some Recent Theory, Experiments, and Simulations on Rubberlike Elasticity
TL;DR: In this article, some unusual types of elastomers described include (i) networks having known structures (model elastomer), (ii) network having bimodal distributions of network chain length, (iii) reversibly cross-linked materials (thermoplastic elastoms), and (iv) elastome cross linked in solution.
Reference BookDOI
Coatings Materials and Surface Coatings
TL;DR: Athey, Jr. as mentioned in this paper proposed the use of surface coatings for the 21st century and showed that they can be applied to a wide range of applications, such as automotive, medical, and industrial.
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