Influence of soft segment molecular weight on the mechanical hysteresis and set behavior of silicone-urea copolymers with low hard segment contents

Effect of polydimethylsiloxane (PDMS) soft segment molecular weight (Mn = 3200, 10,800 and 31,500 g/mol) and urea hard segment content (2.0–11.4% by weight) on the hysteresis and permanent set behavior of segmented silicone-urea (TPSU) copolymers were investigated. In spite of very low hard segment...

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Bibliographic Details
Published in:Polymer (Guilford) 2011-01, Vol.52 (2), p.266-274
Main Authors: Yilgor, Iskender, Eynur, Tugba, Bilgin, Sevilay, Yilgor, Emel, Wilkes, Garth L.
Format: Article
Language:English
Subjects:
Applied sciences
composite polymers
Copolymers
Creep (materials)
Elastomer
Exact sciences and technology
Hysteresis
Inorganic and organomineral polymers
Mechanical hysteresis
mechanical properties
Molecular weight
Physicochemistry of polymers
Properties and characterization
Segments
silicone
Silicone resins
Silicone-urea
urea
Ureas
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Summary:Effect of polydimethylsiloxane (PDMS) soft segment molecular weight (Mn = 3200, 10,800 and 31,500 g/mol) and urea hard segment content (2.0–11.4% by weight) on the hysteresis and permanent set behavior of segmented silicone-urea (TPSU) copolymers were investigated. In spite of very low hard segment contents, all copolymers formed self-supporting films and displayed good mechanical properties. When the mechanical hysteresis and set behavior of the silicone-urea copolymers with similar hard segment contents (around 7.5% by weight) but based on PDMS-3K, PDMS-11K and PDMS-32K were compared, it was very clear that as the PDMS molecular weight increased, hysteresis and instantaneous set values decreased significantly. Copolymers based on the same silicone soft segment (PDMS-11K or PDMS-32K) but with different hard segment contents showed a linear increase in hysteresis and a slight decrease in the instantaneous set as a function of hard segment content. Constant initial stress creep experiments also showed lower creep as the PDMS segment molecular weight increased for copolymers with similar urea contents. Since the critical entanglement molecular weight (Me) of PDMS is stated to be 24,500 g/mol, our results tend to suggest important contribution of chain entanglements on the hysteresis and instantaneous set of these silicone-urea copolymers. [Display omitted]
ISSN:0032-3861
1873-2291
DOI:10.1016/j.polymer.2010.11.040