Elastomers polyester-based

Among the polyurethane, polyester, and polyamide thermoplastic elastomers, those with polyether-based elastomer segments have better hydrolytic stabihty and low temperature flexibiUty, whereas polyester-based analogues are tougher and have the best oil resistance (43). Polycaprolactones and aUphatic polycarbonates, two special types of polyesters, are used to produce premium-grade polyurethanes (12). 

Polyester-based thermoplastic polyurethane elastomers (Section 27.4). 

Thermoplastic polyurethane elastomers have now been available for many years (and were described in the first edition of this book). The adipate polyester-based materials have outstanding abrasion and tear resistance as well as very good resistance to oils and oxidative degradation. The polyether-based materials are more noted for their resistance to hydrolysis and fungal attack. Rather specialised polymers based on polycaprolactone (Section 25.11) may be considered as premium grade materials with good all round properties. 

Fatty acids, both saturated and unsaturated, have found a variety of applications. Brassilic acid (1,11-un-decanedicarboxylic acid [BA]), an important monomer used in many polymer applications, is prepared from erucic acid (Scheme 2), obtained from rapeseed and crambe abyssinica oils by ozonolysis and oxidative cleavage [127]. For example, an oligomer of BA with 1,3-butane diol-lauric acid system is an effective plasticizer for polyvinylchloride. Polyester-based polyurethane elastomers are prepared from BA by condensing with ethylene glycol-propylene glycol. Polyamides based on BA are known to impart moisture resistance. 

The most important physical characteristics of polyurethane elastomers are their elasticity, low permanent set, high tear strength, and good abrasion resistance. Polyester-based elastomers have higher tear strength than polyether-based analogues. Polyether-based elastomers have better recovery. Important chemical characteristics include stability when exposed to the elements and resistance to oil and grease. 

Several polymer-related uses of brassylic acid (BA) have been investigated. For example, a BA/l,3-butanediol/lauric acid oligomer is an effective plasticizer for poljrvinyl chloride,[6] BA/ethylene glycol and BA/propylene glycol polymers function as polyester based polyurethane elastomers,[7] and BA has been patented as a cross-linker for glycidyl methacrylate copolymer powder coatings.[8] However, the most detailed studies have involved polyamides selected data from these studies are summarized in Table I. 

Chemigum Polyester-based polyurethane (elastomer) Goodyear... 

Comparison of Polymers 14 and 15 in Figure 9 shows fairly similar polymerizations up to the point of shortstop addition. The control, Polymer 5, was slower but alive and growing at 18 minutes of polymerization time, reaching a final torque value of 660 meter-grams. Its steady intermediate polymerizarion rate is seen to be characteristic of uncatalyzed thermoplastic polyurethane elastomer polymerizations based on low acid number PTAd while Polymers 14 and 15 formed faster than usual from such a low acid number polyester glycol component. 

Phase I The properties of the phase I elastomers are shown in Tables I and II. The mechanical properties of all the elastomers, both polyether based (Table III) and polyester based (Table IV) were, in general, comparable with conventionally chain extended MDI-based polyurethane elastomers (3). 

HER is an effective chain extender for MDI-based polyurethane elastomers, with both polyether and polyester-based prepolymers. Good overall properties and green strengths resulted. 

Polycarbodlmlde Polymers containing-N=C=N- linkages in the main chain, typically formed by catalyzed polycondensation of polyisocyanates. They are used to prepare open-celled foams with superior thermal stability. Sterically hindered polycarbodimides are used as hydrolytic stabilizers for polyester-based urethane elastomers. 

Third the chain extension through reacting with chain extenders such as 1,6-hexamethylene diisocyanate (HDl) was also developed. Such strategy has resulted in cross-linked urethane-doped polyester elastomers (CUPEs) based on POC [19], cross-linked urethane-doped BPLP (CUBPLP)... 

Chem. Descrip. Isocyanate-terminated polyester-based PU prepolymer Uses Urethane prepolymer yielding cured elastomers with load bearing capacity, high abrasion and tear resistance for caster wheels, sheet goods, solid tires, abrasion-resistant coatings, seals, related engineering applies. 

Segmented polyurethane elastomers, prepared from diisocyanates, macrodiols and chain extenders, are frequently used in the construction of implantable medical devices, such as cardiac pacemakers, heart valves, catheters, and heart assist devices, because of their excellent mechanical properties and haemocompatibility. Polyether macrodiols, such as poly(tetramethylene oxide) (PTMO), are used to prepare polyurethanes for implant, since they offer an increased resistance to enzymatic hydrolysis compared with polyester-based polyurethanes. 

Classification Thermoplastic elastomer Definition Polymer consistg. of hard segments embedded in a soft, elastomeric polyol phase exc. abrasion/impact resist. high str. wide working temp, range good hydrolytic stability two types polyether- or polyester-based Properties Solid... 

Polyester-based PU elastomers contain hard and soft domains. It is desirable to characterise the molecular level interactions giving rise to the two domains, and to use this information to monitor chemical changes. The 2D correlation method provides a means by which the spectral information arising from the two domains can be resolved using thermal perturbations (95). 

It is well known that conventional polyester-based urethane elastomers extended with butanediol can withstand continuous use temperatures of about 80 °C. At higher temperatures, a reduction in the physical and mechanical properties is seen due to degradation of the material. The thermal stability of the polyurethanes is related to the nature of the starting materials such as the aromatic diisocyanate and diol chain extender. The hard segment of the urethane elastomer is primarily responsible for temperature resistance, and the soft segment determines the material s performance at low temperature. 

Dow Plastics Pellethane t TPU elastomers are based on both polyester and polyether soft segments. ... 

It is useful to note that individual polyurethane elastomer classes are truly compatible with only specific plasticizer classes. Polyether-based urethanes are compatible with phthalate ester plasticizers such as dioctyl-phthalate (DOP) and its analogues, whilst polyester-based urethanes are only compatible with benzoate ester-type plasticizers. 

The use of catalysts in the manufacture of urethane elastomers is to be treated with caution as the hydrolytic stability of the final product is usually adversely affected, especially when it is polyester-based. Trace amounts of catalysts are usually present in raw-material manufactured polyesters and polyethers and these must be considered by either their removal or neutralization, otherwise the balance between chain extension, crosslinking and hydrolytic stability will be disturbed. 

The principal of formation of this type of polyurethane elastomer medium, based on a cationic urethane latex, is where an isocyanate-terminated prepolymer derived from either a polyester or polyether diol and toluene diisocyanate is first chain-extended with an alkyl diethanolamine to yield a relatively low molecular weight urethane capable of further chain-extending reactions. Emulsification occurs when the partially extended urethane is added with high-speed mixing to 3% aqueous acetic acid. Curing of the latex takes place either by reaction of water with the terminal isocyanate groups or by reaction with water-soluble diamines. 

Spectra of elastomers obtained by this technique are shown in Fig. 11.3 (polyester-based elastomer) and Fig. 11.4 (polyether-based elastomer). 

---