Ultraviolet-curable Silicone/Urethane Elastomer and Its Selective Modulus Enhancement

Department of Chemical EngineeringThermosets usually have brittle structure, but thermosetting polyurethane (PU) is classified as elastomer due to its urethane linkage in the backbone. Polyurethanes are used in many areas in a form of foam, adhesive and especially as an elastomer. To utilize elastomers in various applications without being fractured, various methods to control the mechanical properties of elastomers have been investigated such as incorporating fillers and additives or creating multiple networks. In this study, ultraviolet-curable silicone containing polyurethane acrylate was synthesized from poly(tetrahydrofuran) (PTH), hydroxy-terminated poly(dimethyl siloxane) (PDMS) and isophorone diisocyanate. The polyurethane chain was terminated with acrylate to fabricate modulus tunable and rapidly crosslinkable silicone/urethane composite elastomer. By adding 3-(trimethoxysilyl)propyl acrylate to the silicone/urethane elastomer network, the mechanical properties of silicone/urethane elastomer can be enhanced by creating additional covalent bonds at elevated temperature. The mechanical properties of the silicone-contained PUA elastomer can be enhanced even after complete photopolymerization, and local modulus enhancement is also possible by heating only desired area of the elastomer. We believe that the silicone/urethane elastomer can be used to fabricate flexible devices, force sensor, etc.clos

Hydrogen bonded supramolecular elastomers : correlating hydrogen bonding strength with morphology and rheology

A series of six low molecular weight elastomers with hydrogen bonding end-groups have been designed, synthesised and studied. The poly(urethane) based elastomers all contained essentially the same hard block content (ca. 11%) and differ only in the nature of their end-groups. Solution state 1H NMR spectroscopic analysis of model compounds featuring the end-groups demonstrate that they all exhibit very low binding constants, in the range 1.4 to 45.0 M-1 in CDCl3, yet the corresponding elastomers each possess a markedly different nanoscale morphology and rheology in the bulk. We are able to correlate small variations of the binding constant of the end-groups with dramatic changes in the bulk properties of the elastomers. These results provide an important insight into the way in which weak non-covalent interactions can be utilized to afford a range of self-assembled polyurethane based materials that feature different morphologies

Thermally activated foaming compositions Patent

Storage stable, thermally activated foaming compositions for erecting and rigidizing mechanisms of thin sheet solar collector

Adhesive for cryogenic temperature applications

Adhesive, which bonds a metal liner to a filament wound composite structure used for cryogenic pressure vessels, prevents the metal liner from buckling under depressurization. The adhesive consists of adducts of urethane and epoxy resins

Isohexide and sorbitol-derived, enzymatically synthesized renewable polyesters with enhanced Tg

Sugar-based polyesters derived from sorbitol and isohexides were obtained via solvent-free enzymatic catalysis. Pendant hydroxyl groups, coming from the sorbitol units, were present along the polyester backbone, whereas the two isohexides, namely, isomannide and isoidide dimethyl ester monomers, were selected to introduce rigidity into the polyester chains. The feasibility of incorporating isomannide as a diol compared to the isoidide dimethyl ester as acyl-donor via lipase-catalyzed polycondensation was investigated. The presence of bicyclic units resulted in enhanced Tg with respect to the parent sorbitol-containing polyester lacking isohexides. The different capability of the two isohexides to boost the thermal properties confirmed the more flexible character provided by the isoidide diester derivative. Solvent-borne coatings were prepared by cross-linking the sugar-based polyester polyols with polyisocyanates. The increased rigidity of the obtained sugar-based polyester polyols led to an enhancement in hardness of the resulting coatings.Peer ReviewedPostprint (author's final draft

In vivo testing of crosslinked polyethers. II. Weight loss, IR analysis, and swelling behavior after implantation

As reported in Part I (In vivo testing of crosslinked polyethers. I. Tissue reactions and biodegradation, J. Biomed. Mater. Res., this issue, pp. 307-320), microscopical evaluation after implantation of crosslinked (co)polyethers in rats showed differences in the rate of biodegradation, depending on the presence of tertiary hydrogen atoms in the main chain and the hydrophilicity of the polyether system. In this article (Part II) the biostability will be discussed in terms of weight loss, the swelling behavior, and changes in the chemical structure of the crosslinked polyethers after implantation. The biostability increased in the order poly(POx) < poly(THF-co-OX) < poly(THF) for the relatively hydrophobic polyethers. This confirmed our hypothesis that the absence of tertiary hydrogen atoms would improve the biostability. On the other hand, signs of biodegradation were observed for all polyether system studied. Infrared surface analysis showed that biodegradation was triggered by oxidative attack on the polymeric chain, leading to the formation of carboxylic ester and acid groups. It also was found that in the THF-based (co)polyethers, α-methylene groups were more sensitive than β-methylene groups. For a hydrophilic poly(THF)/PEO blend, an increase in surface PEO content was found, which might be due to preferential degradation of the PEO domains

Application of Finite Elastic Theory to the Deformation of Rubbery Materials

The purpose of this discussion, then, is to show how the nature of the strain energy function can be deduced from experiments on rubbery materials

Low-cost hot-air solar collector

System has only three components per cell. Cell parts are fabricated from readily available materials and, following a construction procedure which requires use of only simple handtools, can be mounted in place by one person

Modified polyurethane foams for fuel-fire Patent

Modification of polyurethanes with alkyl halide resins, inorganic salts, and encapsulated volatile and reactive halogen for fuel fire contro