Methylene glycol physical properties

Physical properties are related to ester-segment structure and concentration in thermoplastic polyether-ester elastomers prepared hy melt transesterification of poly(tetra-methylene ether) glycol with various diols and aromatic diesters. Diols used were 1,4-benzenedimethanol, 1,4-cyclo-hexanedimethanol, and the linear, aliphatic a,m-diols from ethylene glycol to 1,10-decane-diol. Esters used were terephthalate, isophthalate, 4,4 -biphenyldicarboxylate, 2,6-naphthalenedicarboxylate, and m-terphenyl-4,4"-dicarboxyl-ate. Ester-segment structure was found to affect many copolymer properties including ease of synthesis, molecular weight obtained, crystallization rate, elastic recovery, and tensile and tear strengths. 

These data show that urethane elastomers based on MDI type prepolymer cured with 1,4-butanediol exhibit equivalent or even better physical properties, such as tensile strength, compression set, resilience, tear strength and elongation when compared to elastomers extended with methylene bis (2-chloroaniline), trimethylene glycol di-p-aminobenzoate or hydroquinone bis(2-hydroxyethyl) ether in MDI or TDI system (at equal hardness). Other advantages for 1,4-butanediol curative are low toxicity, liquid state at room temperature, ease of handling and lower cost than other well-known curatives. 

These chemical reactions have a significant influence on the physical properties of the solution and on the phase equilibria. The formaldehyde, which would normally be expected preferably in the vapor phase, behaves now like a component with a similar vapor pressure as water and methanol. To create a model, the reactions listed above have to be taken into account, at least to an extent where significant amounts of the higher methylene glycols or hemiformals are formed. 

In the chapter dealing with the state of dissolved formaldehyde (Chapter 3), it has been pointed out that formaldehyde is hydrated and pai tially polymerized in aqueous solutions, being pre. t. as an equilibrium mixture of the monohydrate, methylene glycol, and polymeric hydrates, polyo> y-methylene glycols. The physical properti of formaldehyde solutions are such as would be expected in the light of this situation. They hehave like solutions of a comparatively non-volatile glycol they d<.> not Ijchave like solutions of a volatile gas. 

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