Poly(urethane-siloxane)s based on hyperbranched polyester as crosslinking agent: Synthesis and characterization

Abstract

A series of novel polyurethane crosslinked structures (PUs) was prepared from α,ω-dihydroxy-(ethylene oxide-poly(dimethylsiloxane)-ethylene oxide) (EO-PDMS-EO), 4,4’-methylenediphenyl diisocyanate and Boltorn® hyperbranched polyester of the third pseudo generation. The hydroxyfunctional hyperbranched aliphatic polyester with 26 end groups was used as crosslinking agent. In order to improve the compatibility of all reactants during the synthesis, PU samples were prepared by a step-growth polymerization in two stages in solution. The soft EO-PDMS-EO segment content was varied in the range from 15 to 40 wt.%. The influence of the EO-PDMS-EO content on the swelling behavior, crosslinking density, hardness, thermal and surface properties of the synthesized PUs was investigated. The structure of the synthesized polyurethanes was confirmed by the presence of specific bands in Fourier transform infrared spectra. Swelling studies were carried out to determine the crosslinking density and polyurethane networks with lower EOPDMS- EO content revealed higher crosslinking density. The glass transition temperature of the synthesized PUs, determined by differential scanning calorimetry, slightly increased from 50 to 58°C by decreasing EO-PDMS-EO content as a consequence of higher crosslinking density of samples. The increase of EO-PDMS-EO content leads to the better thermal stability, as it was confirmed by the value of the starting temperature of thermal degradation. The surface of the polyurethane networks became more hydrophobic with increasing EO-PDMS-EO content. The surface morphology of synthesized polyurethanes was analyzed by scanning electron microscopy

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

“…The large number of terminal hydroxyl groups present in Boltorn ® HBPs enables fast formation of networks that have good mechanical properties, as well as good resistance to chemicals [11][12][13][14], while the presence of PDMS contributes to the good thermal and surface properties, and to elasticity of the highly crosslinked materials. In our previous studies, we have investigated the influence of the content of !,"-dihydroxyethoxy propyl-poly(dimethylsiloxane) (EO-PDMS) and type of HBPs on the swelling behavior, morphological, thermal and thermomechanical properties of PU networks [15][16][17][18][19][20][21]. These results confirmed that physical and thermal properties are related to the crosslinking density, hydrogen bonding interactions, microphase separation and content of EO-PDMS soft segment.…”

“…Catalyst concentration was kept at 0.02 wt% [25][26][27]. The details for the synthesis of similar PU networks are given in our previously published papers [16][17][18][19][20][21]. Compositions of the synthesized PUs and weights of the reactants used for the synthesis of PUs are presented in Table 1.…”

Analysis of dynamic mechanical, thermal and surface properties of poly(urethane-ester-siloxane) networks based on hyperbranched polyester

“…Polyurethane networks based on PDMS macrodiols and Boltorn® HBPs appear to be promising candidates for different applications, especially in coatings, since such multicomponent system can link and combine various properties of all its constituents [18][19][20]. Large number of end hydroxyl groups in HBP is responsible for the fast curing and creation of the highly crosslinked system with good chemical resistance and mechanical properties, while PDMS provides good thermal and surface properties and elasticity in such highly crosslinked material, because of its low glass transition temperature.…”

Tough epoxy/cyanate ester resins with improved thermal stability, lower dielectric constant and loss based on unique hyperbranched polysiloxane liquid crystalline

“…Noting that, even there exist long carbon chains in the structure, LCPSi also exhibits relatively higher thermostability than the reported ones. For instance, the Y c of a poly(urethane‐siloxane) based on hyperbranched polyester is lower than 5 wt% at 700°C, while the Y c of a hyperbranched poly(siloxysilane) synthesized is lower than 5 wt% at about 600°C; therefore, LCPSi prepared herein shows certain advantages in terms of the thermal performance among hyperbranched polysiloxanes.…”