The effect of some disiloxane chain extenders on the thermal and mechanical properties of cross-linked poly(siloxane-urethane)s

Abstract

Abstract. Poly(siloxane-urethane) (PSiU) networks based on a bis(hydroxyorgano) disiloxane chain extender, a trifunctional polyether polyol as a cross-linker, methylene-diphenyl diisocyanate and #,$-hydroxyethoxyethyl polydimethylsiloxane were synthesized in butyl acetate solution. The effect of the chain extenders and the cross-link density was investigated by using thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), swelling, hardness and tensile strength measurements. Isotherm thermogravimetric analyses were carried out for selected polymer compositions at 120 and 170°C and also the changes in tensile strength were followed. The different chain extenders have a strong effect on the hard segment structure, thus on the thermal and mechanical behaviour. The phase separation of the soft and hard segments was indicated by the two or three well distinguished tan% peaks, the maxima of which range within wide intervals depending on the polymer composition. The polymers of high cross-link density showed a very good thermal stability, high tensile strength (up to 68.7 MPa) and hardness (80-95 Shore A) even of high 13-36% dimethyl siloxane content. Changing the siloxane soft segment ratio and the cross-link density the physical properties can be adjusted.

Poly(ε‐caprolactone) and Pluronic Diol‐Containing Segmented Polyurethanes for Shape Memory Performance

“…It is noteworthy that tailoring the properties of PUs via various chain extenders is under spot of interest nowadays. [ 35 ] AT-FTIR and 1 H NMR results supported the PU "segmenting" for which a reaction pathway was proposed. Crosslinking was evidenced in swelling and in DMA.…”

“…Chain extension by PLU and PEG yielded higher tensile mechanical data (E‐modulus, strength, and even elongation at break) than only PEG/or PLU variants. It is noteworthy that tailoring the properties of PUs via various chain extenders is under spot of interest nowadays . AT‐FTIR and 1 H NMR results supported the PU “segmenting” for which a reaction pathway was proposed.…”

Poly(urethane-dimethylsiloxane) copolymers displaying a range of soft segment contents, noncytotoxic chemistry, and nonadherent properties toward endothelial cells

“…They are clinically employed as medical devices for short‐ and long‐term use and drug delivery systems . The versatility of these materials arises from the relative ease of varying their hard (HS) and soft segments (SS), their compositions and molecular weights . Segmented TPUs typically exhibit a two‐phase morphology due to the incompatibility between their hard and soft segments.…”

“…1 The versatility of these materials arises from the relative ease of varying their hard (HS) and soft segments (SS), their compositions and molecular weights. [2][3][4][5][6] Segmented TPUs typically exhibit a two-phase morphology due to the incompatibility between their hard and soft segments. Hard/soft segment segregation in TPUs is generally incomplete, depending on the specific hard/soft segment chemical structure and composition, processing conditions, and other thermal treatments.…”

Surface and thermomechanical characterization of polyurethane networks based on poly(dimethylsiloxane) and hyperbranched polyester

“…The synthesized samples based on PDMS have two T g s in comparison with the control sample and therefore possess microphase separated structure. The network homogeneity of each of the PU networks was analyzed by comparing the width of the mechanical loss factor curves [14,40,41]. The width of the tan ) peak for samples PUS2-15 and PUS2-30 was slightly lower in comparison with PUS1-15 and PUS1-30 samples.…”