Thermoplastic Polyurethanes TPUs

If not available, a user could revert back to the thermoset innerliner compound based on halobutyl rubber, which might increase the cost of production and hurt tire performance. 

Tight Supply Situations in the Past and Future Supply Outlook 

There is insufficient supply history. However, ExxonMobil in 2006 did complete the doubling of its productive capacity for Exxpro (DIMS). 

Thermoplastic polyurethanes are growing in use worldwide growth was about 6% in 2010. Much of this growth is driven by new uses in the automotive and sporting goods markets. Approximately 500 million pounds per year of TPU are consumed worldwide. 

TPUs are manufactured in a manner similar to the way that castable two-part polyurethanes and millable polyurethanes are prepared, using a similar mix of feedstocks. This is discussed in more detail in the next chapter on polyurethanes. 

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Fig. 2 Compression set (elastic recovery under compressive deformation) at 70 °C for an ethyl-ene-LAO random copolymer, flexible polyvinylchloride (f-PVC) thermoplastic polyurethanes (TPUs), and thermoplastic vulcanizates (TPVs)...

The ability to make PE with properties that fall outside these limitations would lead to a tremendous expansion of uses for this polymer, for example replacing flexible polyvinylchloride (f-PVC), which cannot be incinerated or recycled, thermoplastic polyurethanes (TPUs), or thermoplastic vulcanates (TPVs). 

Polyurethane multiblock copolymers of the type described by Eqs. 2-197 and 2-198 constitute an important segment of the commercial polyurethane market. The annual global production is about 250 million pounds. These polyurethanes are referred to as thermoplastic polyurethanes (TPUs) (trade names Estane, Texin). They are among a broader group of elastomeric block copolymers referred to as thermoplastic elastomers (TPEs). Crosslinking is a requirement to obtain the resilience associated with a rubber. The presence of a crosslinked network prevents polymer chains from irreversibly slipping past one another on deformation and allows for rapid and complete recovery from deformation. 

The most common polymers used in FR wire and cable applications are PVC, polyolefins, fluoropolymers, and silicone polymers. Thermoplastic polyurethanes (TPUs) and other specialty polymers such as chlorosulfonated polyethylene also serve niche applications in wire and cable. The approaches to achieve flame retardancy in each of these polymer systems along with issues unique to wire and cable application are discussed in the following sections. 

Polyurethanes. Thermoplastic polyurethanes (TPUs) contain urethane groups, —O—CO—NH— in their structure obtained from the reaction of a diisocyanate (OCN—R—CNO) with a polyol. These polyurethanes are block copol3miers in which hard blocks formed by reaction of a diisocyanate with a short-chain diol alternate with soft blocks formed by reaction of a diisocyanate with a long-chain diol. 

Mishra, V. Murphy, C.J. Sperling, L.H. Interpenetrating polymer networks based on thermoplastic polyurethanes (TPUs) and cis-1,4 polyisoprene. J. Appl. Polym. Sci. 1994, 53, 1425-1434. 

Ho et al (1996) examined polyol or polysiloxane thermoplastic polyurethanes (TPUs) as modifiers in cresol-formaldehye novolac epoxy resins cured with phenolic novolac resin for computer-chip encapsulation. A stable sea-island dispersion of TPU particles was achieved by the epoxy ring-opening with isocyanate groups of the urethane prepolymer to form an oxazolidone. The flexural modulus was reduced by addition of TPU and also the Tg was increased due to the rigid oxazolidone structure. Mayadunne et al (1999) extended this work to a series of phenol- and naphthol-based aralkyl epoxy resins. 

Most TPEs fall in one of six categories, listed in order of increasing cost and performance styrenic block copolymers, polyolefin blends (TPOs), elastomeric alloys, thermoplastic polyurethanes (TPUs), thermoplastic copolyesters, and thermoplastic polyamides [3]. 

Flame retardant intumescent formulations have been developed using charring polymers PA6, thermoplastic polyurethanes (TPUs), and hybrid clay-PA6 nanocomposites as carbonisation agents. The advantage of the eoncept is to obtain FR polymers with improved mechanical properties and to avoid the problem of migration and solubility of the additives. 

Thermoplastic Polyurethanes (TPUs). The first commercial TPEs were the TPUs, which have the same block copolymer morphology as do the COPs. Their general structure is -A-B-A-B-, where A represents a hard crystalline block derived by chain extension of a diisocyanate with a glycol. The soft block, represented by B, can be derived from either a polyester or a polyether. Typical TPU structures, both polyester and polyether types, are represented here ... 

It is known that the potential monomers or pol5uner building blocks should have at least one (in the case of addition polymerization) or two double bonds in their structure (in the case of condensation pol5nnerization) to get thermoplastic materials. Therefore, triglycerides should be modified of fimctionalized before pol5nnerization. Nevertheless, there are some examples of thermoplastic biomaterials obtained from naturally functionalized castor oil with homogeneous composition and acceptable polymerization yields. The main thermoplastic materials already synthesized from vegetable oils are thermoplastic polyurethanes (TPUs), polyamides (PA), thermoplastic polyesters, polyesteramides and polyanhydrides. 

Figure 3.3 Morphology of thermoplastic polyurethanes (TPUs). The solid prisms illustrate the urethane linkages, which have been designated as the hard segments. The polyol soft segments are indicated as flexible strings. Note that a portion of hard...

Figure 3.4 Typical dependence of viscosity (rf) on molecular weight (M ) for thermoplastic polyurethanes (TPUs). The commonly encountered relationship between r) and M (rj M - ) is also shown, along with a sketch of the typical p versus M ...

To illustrate this relationship, consider a random ethylene copolymer of a density 0.856gcm" containing 19mol.% 1-octene comonomer. At room temperature, the material is elastic, or capable of recovering its size and shape after deformation. However, the copolymer loses the desirable properties of an elastomer at higher temperatures for example, the material has a compression set, a measure of a material s ability to recover its size after compression, of 100% at 70 °C (Figure 2). The ability to make PE with properties that fall outside these limitations would lead to a tremendous expansion of uses for this polymer, for example, replacing flexible polyvinylchloride (f-PVC), which cannot be incinerated or recycled, or more expensive thermoplastic polyurethanes (TPUs) or thermoplastic vulcanizates (TPVs). 

Figure 2 Compression set (elastic recovery under compressive deformation) at 70 °C for an E-LAO random copolymer, flexible polyvinylchloride (f-PVC), thermoplastic polyurethanes (TPUs), and thermoplastic vulcanizates (TPVs). Reproduced with permission from Wenzel, T. T. Arriola, D. J. Carnahan, E. M. et at. In Metal Catalysts in Olefin Poiymerization. Topics in Organometallic Chemistiy, Guan, I., Ed. Springer-Verlag Berlin, Germany, 2009 Vol. 26. ...

The interest in blending of thermoplastics with thermoplastic polyurethanes (TPUs) is equivocal some properties of TPUs, such as erosion and abrasion resistance are excellent [85,86], which already justify the blending efforts, but the urethane linkage (-NH-C0-0-) in TPUs is unstable at high temperatures. Isocyanate and hydroxyl groups form via reversible dissociation of the urethane bond, and they are very reactive with the usual functional groups (amine, epoxy. 

Dassin S, Dumon M, Mechin F and Pascault J-P (2002) Thermoplastic polyurethanes (TPUs) with grafted organosilane moieties A new way of improving thermomechanical behavior, Polym Eng Sci 42 1724-1739. 

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