Adhesives from rigid polyols

Nowadays, the trend of research in this field is toward new reaction routes to establish the linking process among polyol and isocyanates obtained from biopolymers to synthesize hybrid PUs and, thus, reach to overcome thermal and mechanical properties of these materials. Also other important parameters such as functionality of diols, isocyanate type, and chain extenders are relevant in PU synthesis [13]. In these materials, the molecular structure varies from rigid cross-linked to linear or highly extensible elastomers hence, their applications are versatile, such as coating or membranes in medical devices, materials in construction engineering, automotive parts, foams and adhesives. 

Propylene oxide is produced from the chlorohydrination of propene similar to the process used to make ethylene oxide (see Ethene). A major use of propylene oxide involves hydrating propylene oxide to produces propylene glycol, propylene polyglycols, and other polyether polyols. These products are used to produce both rigid and flexible polyurethane foams, but they are also used to produce polyurethane elastomers, sealants, and adhesives. 

Lignin by-products from kraft and sulfite pulping were found to constitute useful raw materials for polyols for polyurethane products. Their employment in the manufacture of semi-rigid polyurethane foams as well as polyurethane adhesives and coatings... 

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