POLYUREA-URETHANE

Chicago, II., 26th-29th Sept. 1995, p.253-60. 43C6 RECYCLING OF POLYUREA-URETHANE RIM Kresta J E Xiao H X Suthar B Baeten L Li X H ... 

The polyether-PDMS soft segments in segmented polyurea-urethanes have been synthesized to combine the good mechanical properties of PUs and the excellent blood-contacting properties of PDMS. The most widely recognized material in this category is Avcothane [Arkles BC, Med Device Diagn Ind 3 30(1981)], which is characterized as a block copolymer of aromatic polyether urethane and PDMS. 

Phthalimidoglutaric acid (18), readily prepared from glutamic acid and phthalic anhydride, has served as a precursor for the preparation of several interesting condensation polymers (76MI1110l). For example, it is readily transformed (Scheme 7) into diisocyanate (19), which was utilized for the preparation of a number of optically active polyureas (by reaction with diamines), polyurethanes (by reaction with diols) and polyurea-urethanes (by reaction with amino alcohols). 

Recently Sulzer, working with Grace Davison [35,59] and using polyimide, polysiloxane or polyurea urethane membranes, and ExxonMobil [60], using Nation or cellulose triacetate membranes, have described processes to separate sulfur compounds from various refinery streams. 

R.C. Schucker, Highly Aromatic Polyurea/Urethane Membranes and Their Use of the Separation of Aromatics from Non-aromatics, US Patent 5,063,186, 5,055,632 and 4,983,338 and many others. 

The very slow rate of reaction between an orfho-substituted isocyanate and an ortho-substituted amine in the cure of polyurea-urethanes based on tolylene diisocyanate has been considered to be of significant importance in the final cure of such polymers [180]. 

Careful studies of polyurea formations are generally quite difficult. Low-molecular-weight disubstituted ureas have such low solubility in most solvents that precipitation causes experimental difficulties the problem is even worse with many polyureas. In addition the rather limited thermal stability of polyureas at temperatures of about 200°C has detracted from what otherwise might have been a significant interest in these polymers for fibres. The major commercial interest has not been in pure polyureas, but rather in polymers containing polyurea blocks, as in water-blown polyurethane foams and in polyurea—urethane elastomers. The complexity of these commercial systems, which are nearly always crosslinked, has made kinetic studies difficult. 

An unusually valuable study of the kinetics of polyurea—urethane formation from systems normally used to prepare water-blown polyurethane foams was described by Hartley et al. [195]. Some typical systems were found to consist of a single phase initially, while certain others were complicated by the existence of two phases, with phase inversion occurring. Studies included measurements of the rate of heat evolution, gas evolution and viscosity increase, as well as analysis for the presence of reaction products after intervals of time. 

They found the heat of reaction for 80 20 TDI and water to be 38.3 1.74 kcal mole", and that for 80 20 TDI and a poly(oxy-propylene)triol to be 42.5 0.76 kcalmole" (with two equivalents of NCO per mole in each case). Both separate reactions gave data which fit second-order kinetics up to 50% reaction. Preliminary attempts at calculating kinetic coefficients for both reactions during polyurea—urethane foam formation were given. It is believed that further efforts along this line will be needed to clarify the kinetics satisfactorily, however. 

Table IV shows a breakdown by hard segment level for these different materials - mainly for isocyanate based polyurethanes and polyurea urethanes. ...

In 1968, Ontario Research Foundation developed a series of segmented polyether polyurethanes as polymer membrane materials for reverse cosmosis, ultrafiltration and hemodialysis. The elastomers of recent implant studies are polyurea-urethanes( .) with modification of the synthesis limited to only one variable— the chain length of the polyether component. 

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. 

Markus, A. Linder, C. Polyurea/urethane encapsulated essential oils for controlled release. WO 2004098767, 2004. 

Supramolecular networks based on linkages containing adjacent urea groups have recently been studied. Ni and coworkers examined polyurea-urethane networks connected by H-bonding between triuret and tetrauret blocks [162]. 

Yang CZ, Li C, Cooper SL. Synthesis and characterization of polydimethylsUoxane polyurea-urethanes and related zwitterionomers. J Polym Sci Part B Polym Phys 1991 29(l) 75-86. 

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