Polyethers polyurethanes

Fig. 3. Effect of density on compressive modulus of rigid cellular polymers. A, extmded polystyrene (131) B, expanded polystyrene (150) C-1, C-2, polyether polyurethane (151) D, phenol—formaldehyde (150) E, ebonite (150) E, urea—formaldehyde (150) G, poly(vinylchloride) (152). To convert...

Figure 27.8. Typical load-deflection curves for (a) latex, (b) flexible PVC, (c) polyester polyurethane (curve C) and polyether polyurethane foams (curve D). Shell Chemical Co.)...

Certain fillers are commonly added to protect the urethane backbone from oxidative degradation. Carbon black and titanium dioxide are commonly used in conjunction with antioxidants to protect polyether polyurethanes in exterior adhesive applications that may be exposed to oxygen and light (Fig. 12). 

Abrasion-resistant duties may involve abrasion in an aqueous phase or abrasion by dry particulate materials. The selection of the polyurethane type is most important to obtain the best results. Polyester-based polyurethanes perform best in dry abrasion due to their low hysteresis properties and excellent resistance to cut initiation and propagation. However, polyester polyurethanes are susceptible to hydrolytic degradation, and therefore polyether polyurethanes are normally used for aqueous abrasion duties. 

Polyether polyurethanes are often based on a quasi prepolymer/diol blend reacted with a carbodiimide modified M.D.I. suitable for automatic mix-dispensers. 

Miller J.A., Lin S.B., Hwang K.K.S., Wu K.S., Gibson P.E., and Cooper S.L. Properties of polyether-polyurethane block copolymers Effect of hard segment length distribution. Macromolecules, 18, 32, 1985. 

Figure 19 Free volume plot for co(polyether)polyurethane membranes at 37°C for model drugs. D is the diffusion coefficient in cm2/sec, and H is the hydration expressed as (wet volume — dry volume)/wet volume. (Reproduced with permission from Ref. 59.)...

Despite the popularity of the chlorination-Hercosett route, it is clear that AOX problems will often enforce the adoption of alternatives, many of which have already been developed. Non-AOX polymers include polyethers, polyurethanes, polysiloxanes, polyquaternary compounds and multifunctional epoxides. 

Multiblock copolymers are synthesized by step polymerization using prepolymers containing specific end-groups (Eq. 14). Polyester- and polyether-polyurethanes and polyether-polyesters are multiblock copolymers of commercial interest. Step polymerizations has advantages over living polymerization. There is a... 

Thermoplastic elastomeric behavior requires that the block copolymer develop a microheterogeneous two-phase network morphology. Theory predicts that microphase separation will occur at shorter block lengths as the polarity difference between the A and B blocks increases. This prediction is borne out as the block lengths required for the polyether-polyurethane, polyester-polyurethane, and polyether-polyester multiblock copolymers to exhibit thermoplastic elastomeric behavior are considerably shorter than for the styrene-diene-styrene triblock copolymers. 

The nature of the hard domains differs for the various block copolymers. The amorphous polystyrene blocks in the ABA block copolymers are hard because the glass transition temperature (100°C) is considerably above ambient temperature, i.e., the polystyrene blocks are in the glassy state. However, there is some controversy about the nature of the hard domains in the various multiblock copolymers. The polyurethane blocks in the polyester-polyurethane and polyether-polyurethane copolymers have a glass transition temperature above ambient temperature but also derive their hard behavior from hydrogen-bonding and low levels of crystallinity. The aromatic polyester (usually terephthalate) blocks in the polyether-polyester multiblock copolymer appear to derive their hardness entirely from crystallinity. 

Table X. Mechanical Properties of Polyether—Polyurethane Propellant" after Accelerated Aging...

Composition (wt. %) NH4CIO4 67 aluminum 17 CuO202, a burning rate accelerator 0.1 sulfur, stabilizer 0.1 N-phenylnaphthylamine, stabilizer 0.1 Fe(AA)3 0.015 HAA 0.009 polyether-polyurethane binder containing 25% isodecyl pelar-gonate 15.68%. 

FIGURE 4.5 Extraction of Bromothymal Blue from water by a hydrophobic polyether polyurethane, indicating little or no extraction. 

El Shahawi et al. studied the use of polyurethane for the extraction of pesticides and similar compounds from water. In a 1993 paper, tliey reported investigations of the extraction of Dursban, Karphos and Dyfonate by activated charcoal and a polyether polyurethane foam. The first part of the study focused on isotherms. Weighed portions of carbon and polyurethane were placed in standard solutions of the pesticides and after a period of soaking and agitation, the concentrations of organics in the supernatant solution and in the extractant were measured. Table 4.3 summarizes their data. 

To further explore the effect of the polarity of the molecule on its extractability, we studied the extraction of a water-soluble dye molecule by polyether polyurethane (hydrophobic) and a hydrophilic polyurethane (HPUR). The dye was bromothymol 2005 by CRC Press LLC... 

An activated carbon (Nuchar RGC Powder, 879-R-02) was supplied by the Chemical Division of Westvaco, Covington, VA. A slurry of the carbon was made in water and emulsified with a TDI-based hydrophilic polyurethane prepolymer (Hypol 2002, Dow Chemical, Midland, MI). Immediately after mixing, the emulsion was grafted to a 30-ppi polyether polyurethane (Crest Foam T-30, Monachie, NJ.). The amount of carbon was determined gravimetrically to be 29% by weight. 

In practice, up to 90% of polyurethanes are used in compression, a few percent in torsion, and very little in tension. There is considerable data on the tensile stress against tensile strain (elongation) for polyurethanes. Most polyurethane specification sheets provide this data. Figure 7.3 and Figure 7.4 show typical stress-strain curves for both polyester and polyether polyurethanes. 

The second heat-related effect normally under dry conditions starts at temperatures higher than 80°C. Above 80°C, there is a gradual decrease in properties over time, and the rate increases with more elevated temperatures. Figure 7.11 shows the effect of dry heat aging on a typical polyether polyurethane. 

Polyether polyurethanes are less stable to higher temperatures than the polyester-based materials. The ether linkage in the soft segment is attacked... 

The mechanism is believed to be that a hydrogen atom next to the ether linkage is attacked. This radical reacts with oxygen from the air to form a peroxide radical, which in turn takes another hydrogen atom from the backbone of the chain to form a hydroperoxide. This hydroperoxide breaks down into two more radicals (see Figure 7.12). When polyether polyurethanes are heated in an atmosphere of nitrogen, this thermal degradation does not take place and the material retains its properties. 

A 10-year long-term study was carried out in Panama on diamine cure polyether polyurethanes to examine their long-term resistance in wet humid conditions. The 10 years of exposure was found to have little effect on the samples that had been stored in the sea, jungle, soil, sun, and in a hut. The samples exposed to the direct sun had the greatest loss of properties. Those in the sea had minimal loss in properties after the barnacles had been removed (Cumberland, 1960-1985). 

Two series of polyether polyurethanes (PU) based on hydroquinone bis (P-hydroxyethyl) ether (HQEE) or 1,4-butanediol (BDO) as a chain extender were prepared by the one step bulk polymerisation process. By varying the mole ratio of poly tetra methylene oxide (PTMO) extender (with Mn = 1000 and Mn = 2000) and 4,4 -diphenylene methane diisocyanate (MDI) the two series of HQEE (PUlOOOHj, PU 1000H2, PU2000Hj,... 

Nakajima-Kambe, T., Shigeno-Akutsu, Y., Nomura, N., Onuma, F. Nakahara, T. (1999). Microbial degradation of polyurethane, polyester polyurethanes and polyether polyurethanes. Applied Microbiology and Biotechnology, 51, 134-40. 

Laminating adhesive (solvent-based MDl-based polyether polyurethane 2.5 g/m containing 1-5% 4,4 MDI)... 

N. Grittner, W. Kaminsky and G. J. ObsL Fluid bed pyrolysis of anhydride-hardened epoxy resins and polyether-polyurethane by the Hamburg process. J. Anal. Appl. 

Polybutadiene, polyisoprene Polyesters, polyurethanes, polyamides (nylons) Polyacetals, polycarbonates Polytirethanes, polyesters, nylons Polyether-polyurethane... 

A Polyester and a Polyurethane. A segmented polyether-polyurethane sample (UET46-1) was synthesized in one step from 4-4 diphenyl methane diisocyanate, 1-4 butanediol and poly(tetra-methylene ether)glycol ... 

Figure 4. Measured e spectra at 24°C for O, a segmented polyether-polyurethane (UET46-1) and , a segmented polyether-polyester (H49). Measurements were made with the steady-state response dielectric spectrometer.

---