Polyethers Polypropylene oxide

In reaction injection moulding (RIM), two monomers are injected into a mould, where polymerisation and crosslinking occur. It is used mainly with polyurethanes to make large automotive panels. The chemistry of polyurethanes was described in Chapter 4. Other systems used include a block copolymer between a crystalline polyamide (nylon 6) and a rubbery polyether (polypropylene oxide). In principle, any polymerisation reaction that can be substantially completed after about 30 s in the mould is a candidate for RIM. 

TDA-derived polyols are made by alkoxylation. Polypropylene oxide adducts of I DA (14) and TDA-initiated polyether polyols (13,15) are used in rigid polyurethane foams and continue to be included in new formulations (62) as well as older appHcations. 

Is)max as shown in the diagrams of Figures 17-19 for the three prepolymer types discussed before (polyester, polyether, and polybutadiene). In the examples shown (Is)m ax is about equal for a poly ether (all polypropylene oxide) and a polyester (ca. 49 parts poly (neopentyl glycol) azelate, 35 parts poly (tripropylene glycol) azelate, 10 parts bis (2-ethyl-hexyl) azelate, 6 parts glycerolmonoricinoleate), and about 2 points higher for a polybutadiene binder (ca. 75 parts polybutadiene and 25 parts of a saturated hydrocarbon as plasticizer). 

Polyethers. Polyethers such as polyethylene oxide (PEO) and polypropylene oxide (PPO) have been used for ESI-MS calibration [10,11,19]. The predominant ions for these calibrants are cation attachments, and sodium attachment is frequently observed, due to traces of sodium in solvents and glassware. The positive-ion ESI mass spectra of PEO and PPO are characterized by abundant [M + nNa]n+ and some [M + ] + species. Macrocyclic polyethers and crown ethers were also used as ESI-MS calibrants [11]. In general, nonderivatized polyethers show the following drawbacks when used as calibrations solutions (1) they are difficult to flush out of the ion source, (2) they generate complex mass spectra resulting from the presence of several different cation sources, and... 

Polyethers are typically products of base-catalyzed reactions of the oxides of simple alkenes. More often than not, ethylene oxides or propylene oxides and block copolymers of the oxides are used. A polypropylene oxide-based polymer is built and then capped with polyethylene oxides. An interesting aspect of this chemistry is the use of initiators. For instance, if a small amount of a trifunctional alcohol is added to the reactor, the alkylene oxide chains grow from the three alcohol end groups of the initiator. Suitable initiators are trimethylol propane, glycerol or 1,2,6 hexanetriol. The initiator is critical if one is to make a polyether foam for reasons that we will discuss shortly. 

The most well-known member of this class is the polyether, polyethylene oxide, whose complexes with lithium perchlorate have been used commercially in lithium batteries.60-62 The good solvating power of polyethylene oxide is attributed to an optimal spacing of the electron-donating ether oxygens along a flexible backbone that allows multiple contacts between the polymer backbone and cations. When this distance is decreased, as in polymethylene oxide, chain flexibility is greatly reduced when it is increased, as in 1,3-polypropylene oxide, the distance between... 

IPDI-based prepolymer. This is an aliphatic prepolymer formed by the reaction of IPDI with polyether polyol (3000 molecular weight PPO-based triol) (PPG = polypropylene oxide). The NCO group content of such systems is about 3.4%, and the viscosity about 15 000 CP at 20°C. Solid content is typically 98%-100%. The general reaction is given in Figure 2.22. This prepolymer may typically be used in two-part elastomer systems. 

Prepolymer Process. Semi-prepolymers are prepared mostly by the reaction of TDI and a polyol to obtain a free NCO content of 5 to 10%. The polyols employed for the prepolymers are generally branched amine-or glycol-initiated polypropylene oxide-based polyether polyols having a molecular weight of ca. 600 to 4,000. Polyesters having molecular weights of about 1,000 to 2,000 can also be used. 

In practice, it is very important to obtain a high primary hydroxyl content with minimum EO quantity. A high EO content leads to turbid polyether polyols because longer poly[EO] chains are insoluble in liquid polypropylene oxide. The flexible PU foams made with highly ethoxylated polyols have poor humidity/ageing/degradation characteristics and a lower compression strength. 

During the storage of PO, the formation of a high MW polypropylene oxide) with a MW of 50,000-400,000 daltons and in very small quantities, as a consequence of the contact of liquid PO with the metal walls (carbon steel) of the storage tanks, was observed. The formation of this high MW polyether is explained by the co-ordinative anionic polymerisation of PO, catalysed by the oxides of aluminium, chromium, iron and nickel existing on the metallic surfaces. 

This high MW polypropylene oxide) (PPO) is a very dangerous contaminant. The polyether polyols obtained by using a PO with a content of high MW PPO (higher than 0.3-1 ppm), lead in the foaming process to very undesirable phenomena the foam collapse with a low foam rise and substantial blow hole formation. 

Unambiguous testing of the soft segment only, that is, the polyether part, by the same procedure was more difficult, but important information was obtained. Each of the polyethers studied—poly(tetramethylene oxide) (PTMO), polypropylene oxide) (PPO), and p ly(ethylene oxide) (PEO)—are partially crystalline in the form of dry, a, oo diols after deposition on the bead surfaces from organic solvents. 

The isolated polyether matrix was modeled using polypropylene glycol (2000 MW) and isotactic polypropylene oxide. The polypropylene glycol was degassed and placed over molecular sieves to remove residual water present in the polyol. The isotactic polypropylene oxide was isolated by repeated crystallization from acetone (9). Inherent viscosity was 1.85 in benzene (0.5% concentration) at 25°C. Films of the isotactic polypropylene oxide were cast onto glass plates (cleaned as described previously) from a 6% solution of the polymer in N,N-dimethylformamide, dried in a forced air draft oven for 1 h at 75°C, and then placed in a vacuum desiccator (0.1 mm mercury) for 24 h to insure complete removal of residual solvent. 

Details A liquid with a characteristic smell of natural gas/ether/benzene, and an epoxide. It is used to produce polyether polyols and the polymer polypropylene oxide (polypropylene glycol) and used as a preservative, and in thermobaric weapons (also called high-impulse thermobaric weapons or fuel-air explosives). 

As a result of increase in molecular weight of prepolymer from 1400 (SPU-1) to 2100 (SPU-4) or partial replacement of MOCA by polypropylene oxide diol (SPU-2) the amount of hard segments and common density of network decreased. But the equilibrium swelling in plasticizers increases (Table 10.15). The SPU modulus of elasticity decreases. The increase in the number of oxygen atoms in a polyether chain (SPU-4) results in decreased swelling in less polar plasticizers (TO, DOS, DOP). The elasticity modulus of the material in these plasticizers varies slightly. A large value for polyurethane SPU-5... 

Polyester PUs have good material properties, but they are susceptible to hydrolytic cleavage of the ester linkage while polyether based urethanes have relatively high resistance to hydrolytic chain scission. Polyethylene oxide (PEO) based materials exhibit poor water resistance due to the hydrophilic nature of the ethylene oxide. Although the PUs mechanical properties obtained with polypropylene oxide (PPO) are not as good as those made from PTMO, PPO has also been widely used because of its low cost and reasonable hydrolytic stability [2]. 

Polyester polyurethanes display greater oxidative stability than do polyether polyurethanes. Among polyether polyurethanes, polyethylene oxide and PTMO are more resistant than polypropylene oxide. Metal impurities, such as iron and copper, will catalyze the oxidation of polyurethanes. Copper is found to be particularly detrimental. ... 

Bakker D, et al. Biocompatibility of a polyether urethane, polypropylene oxide, and a polyether polyester copolymer. A qualitative and quantitative study of three alloplastic tympanic membrane materials in the rat middle ear. J Biomed Mater Res 1990 24(4) 489-515. 

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