The effect of chain length and content of flexible oligo(oxyethylene) segments on some properties of copoly(ester-ether)s.
Part II. Mechanical propertie
In a broad range of temperature (from -100°C to +200°C) the dynamical mechanical (DMTA) properties, namely hardness (H), yield stress (as), tensile strength (or) and permanent set (e) of thermoplastic copoly(esterether) (KPEE) elastomers composed of rigid oligo(tetramethylene terephthal-ate) segments and soft oligo(oxyethylene) segments were investigated. The mass contentand molecular weight of flexible segments in the investigated KPEEs was varied. The number average molecular weight, M„, of flexible segments was in the range of 400—6000. The effect of M„ and mass content (Ws) of flexible segments and content of crystalline phase on the investigated properties was characterized. The crystallizability of flexible segments increases with an increase in the molecular weight and a practical effect of the crystallization of these segments is the increase in storage modulus, loss modulus, hardness, yield stress and permanent set of KPEEs. In the temperature range above the melting points of flexible segments and glass transition point of rigid segments (about 49°C) and below the range of melting point of rigid segments, the above mentioned mechanical properties of KPEEs (except of permanent set) are independent of the molecular weight of flexible segments.
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