Glycol-chain-extender component

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. 

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). 

Synthesis and Modification. A series of polyurethanes and polyurethane-ureas of varying degress of hydrophilicity and hydrophobicity and mechanical property were synthesized. The polymers were prepared by a solution polymerization method and consisted of three components a polyether, a diisocyanate, and a chain extender. In our studies, polyurethanes (Table I) were based on a carbowax (polyoxyethylene glycol), MDI (methylene bis-4-phenyl isocyanate) and 1,5-pentanediol. Polyurethane-ureas (Table II) were obtained by substituting the chain extender from a diol to a diamine. The polyurethane-ureas (Table II) were obtained by changing the chain extender from a diol to a more reactive diamine. The polyurea-urethanes (Table III) were obtained by using a diamine terminated polyether instead of the carbowax. 

In most of our studies, modification of the synthetic route was limited to only one variable, the chain length of the polyether component. The same molar ratio of polyether/chain extender disocyanate (MDI) and chain extender (diethlene glycol) were used. The molecular weight of the polyether component of J-20, J-9 and J-6 was 2,000, 1,000 and 600 respectively. A wide range of properties was obtained from this series of polyurethanes. Properties intermediate between J-20 and J-9 were also obtained by... 

Chain Extenders and Cross-linkers. In addition to the two principal components of most urethane coatings, isocyanate and polyol components, a number of di- or polyfunctional, active hydrogen components may be used as chain extenders or cross-linkers. The most important classes of compounds for this use are diols or polyols (monomers or oligomers), diamines, and alkanolamines. Typical examples of diols are ethylene, dlethylene, dlpropylene glycol, 1,4-butanedio1, 1,5-hexanediol, neopentyl glycol,... 

It is already well known that the PUs are obtained by reacting a diisocyanate (I) with a macrodiol (MD) of a polyesteric or polyetheric type, and with a glycol as a chain extender (CE). The simplest approach seems to be the simultaneous mixing of the three components on approaching the one shot synthesis route ... 

The most important intermediates in the preparation of polyurethanes elastomers are the polyols and the diisocyanates. Also influencing properties are chain extenders such as glycols and amines. The effect of varying these components on the properties of the elastomers has been widely studied and reported (e.g. Saunders and Frisch, 1%2) and only a brief summary will be given here. 

The viscoelastic properties of semi-IPNs based on a thermoplastic polyurethane (TPU) and a chemically crosslinked polyurethane (PU network) formed in the TPU solution, as well as of the same semi-IPNs filled with " (-Fe203 powder have been studied by Brovko et al. [27]. The TPU (molar mass 40000 g/mole) was synthesized from poly (1,4-butylene) glycol adipate (molar mass 1000 g/ mole), 4,4 -methylenebis(phenyl isocyanate) and 1,4-butane diol as a chain extender. The PU network was based on a vinyl chloride/vinyl acetate/vinyl alcohol terpolymer with an adduct of 1,1,1-trimethylolpropane and 2,4-toluene diisocyanate the appropriate for crosslinking NCO/OH ratio was chosen to be 0.55. The non-filled semi-IPNs exhibited only one situated between those of TPU and PU network. Therefore, the components of the semi-IPNs may be assumed to be compatible. It was found that the semi-IPNs filled with a small amount of >Fe20g (up to 1.4 vol%) exhibited one shifted toward higher... 

In this respect, the ATR spectra taken from the surface of films provide even more reliable information. Upon consideration of the processes of complex formation, one should take into account that the oligoether fragments include electron-donor groups and complex formation by M(AcAc) can also take place with the glycol component of the macrochain. UV spectroscopic data for the system PU-19 Fe(AcAc)3 confirm this assumption, since variations in the intensity of electron absorption spectra are observed by the increase of the oligoether concentration, i.e., complex formation takes place. Thus, the nature of the metal atom and the structure of the chain extender determine to a great extent the character of complex formation in polyurethane systems. 

---