Aliphatic polyols

Example 5. Glycolysis of Polyurethanes with Propylene Oxide after Pretreatment with Ethanolamine.55 A rigid polyurethane foam (ca. 100 g) was dissolved in 30 g ethanolamine by heating. Excess ethanolamine was stripped, leaving a clear solution. Infrared and GPC analysis indicated that the clear solution obtained contained some residual polyurethane, aromatic polyurea, aliphatic polyols, aromatic amines, and N,N -bis(f -hydroxyethyljurea. Next the mixture was dissolved in 45 g propylene oxide and heated at 120°C in an autoclave for 2 h. The pressure increased to 40 psi and then fell to 30 psi at the end of the 2-h heating period. The product was a brown oil with a hydroxyl number of485. 

Glycidyl Ethers of Aliphatic Polyols. Glycidyl ether epoxy resins based on polyols provide greater flexibility and lower softening temperatures for the final cured epoxy system. The polyol is reacted with epichlorohydrin to produce these resins. These resins are generally not used alone because of water sensitivity and overall lack of toughness. However, they serve as modifiers for DGEBA-based epoxy resins. An idealized structure for a flexible resin based on this chemistry is shown in Fig. 2.9. 

Other products that may be epoxidized in this way include dihydric and trihydric phenols, aliphatic polyols such as glycerol, and simple alcohols such as butanol or alyl alcohol. These products, especially the monofunctional glycidyl ethers, are used at relatively low percentages to reduce the viscosity of formulations containing DGEBA resins. In this way, they act as reactive diluents. 

Glycidyl ethers of aliphatic polyols based on polyglycol, glycerin, and other polyols are flexible epoxy resins. They are used as reactive diluents and flexibihzers for solvent-free epoxy resin formulations. Epoxy-polyglycol resins that are produced from the reaction of epichlorohydrin and polyester polyols based on ethylene or propylene oxide are the most common of these types of flexible epoxy resins. Examples of typical commercial aliphatic epoxy resins are shown in App. C. 

The rate of reaction depends on the structure of both the polyol and the isocyanate. Aliphatic polyols are more reactive than aromatic and more stable. Polyurethanes are described as any polymer chain that has been extended by reaction with di- or polyisocyanate. The isocyanate group (-NCO-) can react with most compounds containing an active hydrogen atom. 

Clearly, the carboxyl and carbonyl functional groups act as transmitters of unpaired electron spin density through the n system, because immediate broadening is observed in many cases, especially on use of Mn ". However, the selective line-broadening observed in the aliphatic polyol chain should provide qualitative information about any metal-ion binding-site. 

Polyphenolic compounds occur widely distributed in nature and may possess a variety of interesting biological properties, e. g. antibiotic, antiviral and antitumor activity. The synthesis and further elaboration of these compounds often requires the selective protection or deprotection of specific phenolic hydroxy groups. To achieve this goal, the methods highlighted above for the various aliphatic polyols can also be applied successfully. 

Of course the thermal stability and char yield depend on the polyol structure too and the aromatic polyols are superior to aliphatic polyols from this point of view. This is the reason for the extremely rapid growth of aromatic polyester polyols, of low functionality, low viscosity and low cost. 

Thus, the polyol nature has a marked effect on the fire resistance, which is in fact the order of thermostability. The most thermostable polyols lead to polyurethanes with improved fire resistance. Thus, polyesters are superior to polyethers in so far as the fire resistance of the resulting polyurethanes is concerned. Cycloaliphatic polyols (for example polyols based on carbohydrates, such as sucrose or alkyl glucosides) produce polyurethanes with superior fire resistance as compared to the simple aliphatic polyols (for example polyether based on glycerol or on pentaerythritol). 

Polyurethane. Polyurethanes are formed by mixing liquid aliphatic polyols with liquid aromatic polyisocyanates, which react readily. These mixes gel in several minutes at room temperature, but often benefit from final heat cure. Most polyurethanes are foamed by introducing and expanding gas bubbles when the reacting liquids have reached the optimum viscosity, then the cross-linking reaction is completed to stabilize the foam structure. 

XU) or resorcinarenes, cyclophosphazenes (XLIII), gluddic precursors, aliphatic polyols (XXXI, XXXII), adamantane-based cores, dendrimers, and metallic cores... 

Conventional polyurethane foams are prepared from aromatic diisocyanates and aliphatic polyols. For manufacturing rigid foams, a high excess of isocyanate may be used for creating cyclic isocyanurate structures in the presence of the suitable... 

Epoxy resins n. Plastic or resinous materials used for strong, fast-setting adhesives, as heat resistant coatings and binders, etc. Cross-linking resins based on the reactivity of the epoxides group. One common type is the resin made from epichlorohydrin and bisphenol A. Aliphatic polyols such as glycerol may be used instead of the aromatic bisphenol A or bisphenol F. 

Aliphatic polyols such as glycerol [36], 2,5-bis(hydroxymethyl)tetra-hydrofuran [37], and chlorinated butenediol [38,39] have been reported to be used to give epoxy compounds. More recently it has been reported that epichlorohydrin and methylepichlorohydrin can be reacted with polymercaptonaphalene to give glycidylthioethers for use as curable epoxy resins [40]. 

Plouvier V 1963 Distribution of aliphatic polyols and cyclitols. In Swain T (ed) Chemical plant taxonomy. Academic Press London, 313-336... 

The role usually enacted by dendritic polyesters, like most aliphatic polyols, is to provide a... 

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