Glycols chain extenders

Hard Segments. The hard segments are the linear reaction products of the diisocyanate component and the third monomer type in the TPU elastomer recipe, the small glycol-chain-extender component. In Figure 5 we see a typical TPU hard-segment structure which is formed from MDI and 1,4-BDO (1,4-butanediol). 

Several types of diisocyanates (aromatic, aliphatic, cyclo aliphatic) and many different glycol-chain extenders (open-chain aliphatic, cyclo aliphatic, aromatic aliphatic) can be used to produce TPU-elastomer hard segments. In the more conventional and practical formulations only a single diisocyanate component is used to make a TPU, so the diisocyanate is common to both the hard and soft segments. The polymer chemist makes his diisocyanate and glycol-chain-extender component selections based on such considerations as desired TPU mechanical properties, upper service temperature, environmental resistance, solubility characteristics, and economics. 

C. Ethylene Glycol Chain Extender Effects. Figure 6 shows the polymerization viscosity-time-temperature relations for a thermoplastic poly(ester-urethane) elastomer, Polymer 10, made from monomers VII, IV, and XI (Table I). VII is low acid number PTAd (0.15) and XI is ethylene glycol chain extender. The polymerization charge also contained 0.25% (on charge) of Irganox 1010 antioxidant. 

The polymerization of Polymer 10 reached its maximum torque in 7 minutes (390 meter-grams) then died and began to degrade with loss of melt viscosity, even at this low polymer melt viscosity level and familiar polymerization temperature. Ethylene glycol chain extended polymers have been anomalous polymerizations and polymers in our experience due, we believe, to abnormal chemistry that can occur during their preparation. 

With PUR, a chemical reaction between the mixed liquid components, polyol chain extender, and isocyanate takes place inside the mold after each shot, enabling the properties of the moldings to be predetermined and controlled. Depending on the mix, the cycle times can be reduced. In the past ten years, cycle times for typical PUR-RIM or PUR-RRIM have been reduced from 3 min. to about 30 s because of the development of a faster reaction speed (glycol chain extenders were replaced by amine chain extenders). 

Hexamethylene glycol Neopentyl glycol Polypropylene glycol Tripropylene glycol chain extender, PU elastomers Hydroquinone bis (2-hydroxyethyl) ether 4,4 -Methylenebis (3-chloro-2,6-diethylaniline) 4,4 -Methylenebis 2,6-diethylaniline 4,4 -Methylenebis 2,6-diisopropylaniline 4,4 -Methylenebis 2-isopropyl-6-methylaniline Resorcinol di (P-hydroxyethyl) ether Resorcinol di (P-hydroxypropyl) ether chain growth, ethylene longer chain aluminum alkyls... 

However it is also established that the commonly used diphenylmethane and naphthalene diisocyanate-based elastomers are frequently chain-extended with glycols. Table 3.12 contrasts the effects of diamine and glycol chain extenders with a toluene diisocyanate/polyether-based prepolymer, Adiprene LI00. With the unsymmetrical diisocyanates, such as TDI and MDI, polyol chain extenders give elastomers of poorer properties than diamines, and it is usually desirable to introduce additional crosslinking into diol-extender elastomers by the use of a proportion of a triol such as... 

The effect of different glycol chain extenders is given in Table 3.14, which shows the effect of the nature of these diol chain extenders. Note the low compression set obtained with ethylene glycol. 

More recently, polyoxyalkylene polythioalkylene polyols have been claimed to be useful for improving the heat resistance in polyurethanes. Studies with model compounds have also shown that the structure of the glycol chain extender may also influence the thermal stability. Ethylene glycol-based materials were found to be less stable than compounds prepared from butanediol. 

In the 1940s ICI introduced a material marketed as Vulcaprene made by condensing ethylene glycol, adipic acid and ethanolamine to a molecular weight of about 5000 and then chain extending this with a diisocyanate. This rubbery material found some use as a leathercloth and is dealt with further in Chapter 25. 

The resulting prepolymer can then be chain extended with water, glycols or amines by linking cross terminal isocyanate groups (Figure 27.4). 

More recently, storage systems based on MDI have become available which pose less of a health hazard than MDI/MOCA systems. Both polyethers and polyesters are used, with glycols being the usual chain extenders. 

Similar reactions occur when an amine is used instead of a glycol as chain extender ... 

A chain extender could be selected from the following compounds ethylene glycol, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol, neopentanediol, hexanediol, methyl-dihydroxylethyl amine (MDEA) [9], etc. These should be as dry as possible. 

Scheme 4.5 Examples of glycol and amine chain extenders. (Unilink is a registered trademark of UOP LLC.)...

A series of poly(ester-urethane) urea triblock copolymers have been synthesized and characterized by Wagner et al/ using PCL, polyethylene glycol, and 1,4 diisocyanatobutane with either lysine ethyl ester or putrescine, as the chain extender. These materials have shown the elongation at break from 325% to 560% and tensile strengths from 8 to 20 MPa. Degradation products of this kind of materials did not show any toxicity on cells. 

Segmented poly(ether urethanes) were synthesized from polypropylene glycol (PPG) and 4,4 methylene-bis(phenyl-isocyanate) (MDI), using l,l -bis(B-aminoethyl)ferrocene (1) and 1,1 -bis(B-hydroxyethyl)-ferrocene (2) as chain extenders. 

Sugar fermentation and ther- Propylene glycol SolvenL chain extender in... 

The chain-extended, linear poly(ester urethanes) so obtained can now be crosslinked in a second stage, involving reaction with - water - or glycols - or diamines. 

Most of these polymers have multi-functional character, which results in cross-linked heterogeneous products. In contrast, monomethoxy polyethylene glycol (PEG) presents only one reactive terminal group per polymer chain. Once PEGy-lated with these compounds, the protein acquires a brush-like shape, with the hydrophilic PEG chains extended from the protein to the solvent. 

Tg for a linear, high-molecular-mass PPO, which was prepared from a polypropylene glycol precursor (with a molecular mass of 4000 g/mol) using a chain extender with a chemical structure similar to that of the crosslinker, is -62.5 °C. The Tg was determined from DMA measurements performed at 0.215 Hz [43]. 

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