Poly butylene Terephthalate

The polyester from 1,4-butane diol and terephthalic acid possesses good processability and excellent impact strength. The polymer is a competitor with polyacetals. 

A block copolymer of 60% poly(l,4-butanediol terephthalate) and 40% poly(butylene glycol) (molecular weight 1000) with a molecular weight of 25,000 g/mol is a thermoplastic elastomer. 

Major polymer applications composites, textiles, brush bristles, tire cords, electrical and electronics (connectors, circuit breakers, capacitor housings), automotive (distributor caps, mirror housings, door knobs), housewares, lighting, power tools, sporting goods, plumbing 

Important processing methods injection molding, extrusion, monofilament extrusion 

Typical fillers carbon fiber, glass fiber, aramid, mica, talc, calcinated kaolin, antimony trioxide, carbon black, zinc borate, glass spheres 

Auxiliary agents coupling agents used in composites 

Special methods of incorporation the process design should account for the much faster crystallization rates of filled materials 

Poly(butylene terephthalate) (PBT) (1) resins are semicrystalline thermoplastics used in a wide variety of applications, most commonly in durable goods that are formed by injection molding. Applications include electronic and communications equipment, computers, televisions, kitchen and household appliances, industrial equipment, lighting systems, gardening and agricultural equipment, pumps, medical devices, food handling systems, handles, power and hand tools, bobbins and spindles, and automotive parts in both under-the-hood and exterior applications. Additionally, PBT is very widely used to form electrical connectors. PBT, through its many blended products, can be tailored to suit numerous applications. 

PBT resin has been reviewed in many articles, often as part of a larger review of polyesters [1-3], A recent article provides an historic account of polyester development as an alternative to nylon fibers [4], while the review of Kirsch and Williams in 1994 gives a business perspective on polyesters [5], However, an understanding of PBT in the context of the more common polyester polyethylene terephthalate) (PET) is often overlooked. PET dominates the large volume arenas 

Modem Polyesters Chemistry and Technology of Polyesters and Copolyesters. Edited by J. Scheirs and T. E. Long 2003 John Wiley Sons, Ltd ISBN 0-471-49856-4 

The commercial application of PBT is at first glance very improbable. PBT is made of a more expensive raw material (1,4-butanediol vs. ethylene glycol for PET), is manufactured on a smaller scale than PET, has a lower melting point, and has slightly poorer mechanical properties than PET. 

PBT is made by reacting 1,4-butaiiediol (BDO) with terephthalic acid (TPA) or dimethyl terephthalate (DMT) in the presence of a transesterification catalyst. A number of different commercial routes are used for producing the monomers, as discussed below. 

Genopak, Genotherm Hoechst Poly( vinyl chloride) 

The expiry of the original poly(ethylene terephthalate) patents provided the catalysts for developments not only with poly(ethylene terephthalate) but also 

In the USA producers included Eastman Kodak (Tenite PTMT), General Electric Corporation of America (Valox), and American Celanese (Celanex). In Europe major producers by the end of the decade were AKZO (Amite PBTP), BASF (Ultradur), Bayer (Pocan) and Ciba-Geigy (Crastin). Other producers included ATO, Hiils, Montedison and Dynamit Nobel. With the total Western European market at the end of the decade only about 7000 tonnes other companies at one time involved in the market such as ICI (Deroton) withdrew. 

By 1998, however, the Western European market had grown to over 90 000 t.p.a., that for the United States to about 140 000 t.p.a. and that for Japan to just over 60 000 t.p.a. There are also about a dozen USA and Western European manufacturers. Statistics on capacity are somewhat meaningless, as the polymer can be made using the same plant as employed for the manufacture of the much larger tonnage material PET. It is, however, quite clear that the market for injection moulded PBT is very much greater than that for injection moulded PET. 

A large number of grades is available, one supplier alone offering about 40, including unreinforced, glass- and carbon-fibre reinforced, mineral filler reinforced, impact modified, elastomer modified, flame retardant and various combinations of the foregoing. 

As with poly(ethylene terephthalate) there is particular interest in glass-fibre-filled grades. As seen from Table 25.8, the glass has a profound effect on such properties as flexural modulus and impact strength whilst creep resistance is also markedly improved. 

12- dodecanedioate), aliphatic-aromatic random copolyesters have been prepared using 1,4-BD and different molar ratios of 1,12-dodecanedioc acid and terephthalic acid [32]. In particular, the copolymer containing 70 mol% of PBT repeating units notably improved the thermal and mechanical properties of poly( butylene 

12- dodecanedioate) towards those of PBT and maintained a very high thermal stability, however, the biodegradability of the polyalkylene dicarboxylate was lost. 

In another study, it has been demonstrated that the partial replacement of 1,4-BD by 2,3 4,5-di-0-methylene-galactitol resulted in PBT copolyesters with enhanced 

In all cases, degradation proceeded by splitting of the relatively weak ester group associated with the sugar moiety and without modification of the diacetal structure. 

The noteworthy conclusion is that whereas the incorporation of 2,3 4,5-di-0-methylene-galactitol units in PBT leads to copolyesters with controlled hydrodegradability, the incorporation of 2,3 4,5-di-0-methylene-galactarate units is a suitable option for obtaining rapidly hydrodegradable and biodegradable PBT copolyesters. 

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Chlorinated polyether Poly(butylene terephthalate) (PBT) talso called... 

Poly(butylene Terephthalate). Poly(butylene terephthalate) is prepared in a condensation reaction between dimethyl terephthalate and 1,4-butanediol and its repeating unit has the general structure... 

Low viscosity 30% glass-fiber reinforced Poly(butylene terephthalate) Poly(ethylene terephthalate) ... 

Uses. The largest uses of butanediol are internal consumption in manufacture of tetrahydrofuran and butyrolactone (145). The largest merchant uses are for poly(butylene terephthalate) resins (see Polyesters,thermoplastic) and in polyurethanes, both as a chain extender and as an ingredient in a hydroxyl-terminated polyester used as a macroglycol. Butanediol is also used as a solvent, as a monomer for vadous condensation polymers, and as an intermediate in the manufacture of other chemicals. 

Poly(ethylene terephthalate), the predominant commercial polyester, has been sold under trademark names including Dacron (Du Pont), Terylene (ICI), Eortrel (Wellman), Trevira (Hoechst-Celanese), and others (17). Other commercially produced homopolyester textile fiber compositions iaclude p oly (1,4-cyc1 oh exa n e- dim ethyl en e terephthalate) [24936-69-4] (Kodel II, Eastman), poly(butylene terephthalate) [26062-94-2] (PBT) (Trevira, Hoechst-Celanese), and poly(ethylene 4-oxyben2oate) [25248-22-0] (A-Tell, Unitika). Other polyester homopolymer fibers available for specialty uses iaclude polyglycoHde [26124-68-5] polypivalolactone [24937-51-7] and polylactide [26100-51-6],... 

Polyester sheet products may be produced from amorphous poly(ethylene terephalate) (PET) or partiaHy crystallized PET. Acid-modified (PETA) and glycol modified (PETG) resins are used to make ultraclear sheet for packaging. Poly(butylene terephthalate) (PBT) has also been used in sheet form. Liquid-crystal polyester resins are recent entries into the market for specialty sheet. They exhibit great strength, dimensional stabHity, and inertness at temperatures above 250°C (see Polyesters,thermoplastic). 

Butanediol. 1,4-Butanediol [110-63-4] made from formaldehyde and acetylene, is a significant market for formaldehyde representing 11% of its demand (115). It is used to produce tetrahydrofuran (THF), which is used for polyurethane elastomers y-butyrolactone, which is used to make various pyrroHdinone derivatives poly(butylene terephthalate) (PBT), which is an engineering plastic and polyurethanes. Formaldehyde growth in the acetylenic chemicals market is threatened by alternative processes to produce 1,4-butanediol not requiring formaldehyde as a raw material (140) (see Acetylene-derived chemicals). 

The white cell adsorption filter layer is typically of a nonwoven fiber design. The biomaterials of the fiber media are surface modified to obtain an optimal avidity and selectivity for the different blood cells. Materials used include polyesters, eg, poly(ethylene terephthalate) and poly(butylene terephthalate), cellulose acetate, methacrylate, polyamides, and polyacrylonitrile. Filter materials are not cell specific and do not provide for specific filtration of lymphocytes out of the blood product rather than all leukocytes. 

Small amounts of polymer-grade terephthaHc acid and dimethyl terephthalate are used as polymer raw materials for a variety of appHcations, eg, adhesives and coatings. They are also used to make high performance polymers or engineering resins. Poly(ethylene terephthalate) is itself an engineering resin, although one more widely used is poly (butylene) terephthalate, formed by reaction with 1,4-butanediol as the comonomer. 

Automotive appHcations account for about 116,000 t of woddwide consumption aimuaHy, with appHcations for various components including headlamp assembHes, interior instmment panels, bumpers, etc. Many automotive appHcations use blends of polycarbonate with acrylonitrile—butadiene—styrene (ABS) or with poly(butylene terephthalate) (PBT) (see Acrylonitrile polymers). Both large and smaH appHances also account for large markets for polycarbonate. Consumption is about 54,000 t aimuaHy. Polycarbonate is attractive to use in light appHances, including houseware items and power tools, because of its heat resistance and good electrical properties, combined with superior impact resistance. 

During the eady development of polycarbonates, many bisphenols were investigated for potential useftil products. Some of these monomers and polymers are hsted in Table 3. Despite this intensive search, however, no homopolycarbonates other than that of BPA have been produced. Copolymers and blends, on the other hand, have been quite successhil. Blends of polycarbonate with ABS and with poly(butylene terephthalate) (PBT in particular have shown significant growth since the mid-1980s. 

The principal polymers to be described are poly(butylene terephthalate) [26062-94-2] (PBT) poly(ethylene terephthalate [25038-59-9] (PET) poly(cyclohexanedimethylene terephthalate) [24936-69-4] (CHDMT), and mention will be made of poly(ethylenenaphthalene-2,6-dicarboxylate)... 

Noncrystalline aromatic polycarbonates (qv) and polyesters (polyarylates) and alloys of polycarbonate with other thermoplastics are considered elsewhere, as are aHphatic polyesters derived from natural or biological sources such as poly(3-hydroxybutyrate), poly(glycoHde), or poly(lactide) these, too, are separately covered (see Polymers, environmentally degradable Sutures). Thermoplastic elastomers derived from poly(ester—ether) block copolymers such as PBT/PTMEG-T [82662-36-0] and known by commercial names such as Hytrel and Riteflex are included here in the section on poly(butylene terephthalate). Specific polymers are dealt with largely in order of volume, which puts PET first by virtue of its enormous market volume in bottie resin. 

Hydroformylation. Hydroformylation of aEyl alcohol is a synthetic route for producing 1,4-butanediol [110-63-4] a raw material for poly(butylene terephthalate), an engineering plastic (qv) many studies on the process have been carried out. 

Polyesters. Polyesters (qv) are widely used as the matrix for conventional composites. Two resins of particular importance because of the large amounts used are (poly(ethylene terephthalate) [25038-59-9] (PET) and poly(butylene terephthalate) [24968-12-5] (PBT). Although polyesters can be made from diacids and diols by direct condensation. 

Alloys and blends are of great commercial significance. The archetype of "alloys" is the poly(phenylene oxide)—polystyrene resin discussed eadier. Important examples of blends based on immiscible resins are afforded by the polycarbonate—poly(butylene terephthalate) resins and polycarbonate—ABS blends. 

Engineering resins can be combined with either other engineering resins or commodity resins. Some commercially successhil blends of engineering resins with other engineering resins include poly(butylene terephthalate)—poly(ethylene terephthalate), polycarbonate—poly(butylene terephthalate), polycarbonate—poly(ethylene terephthalate), polysulfone—poly (ethylene terephthalate), and poly(phenylene oxide)—nylon. Commercial blends of engineering resins with other resins include modified poly(butylene terephthalate), polycarbonate—ABS, polycarbonate—styrene maleic anhydride, poly(phenylene oxide)—polystyrene, and nylon—polyethylene. 

Table 18. Properties of Polycarbonate—Poly(butylene terephthalate) Blends ...

The use of ABS has in recent years met considerable competition on two fronts, particularly in automotive applications. For lower cost applications, where demands of finish and heat resistance are not too severe, blends of polypropylene and ethylene-propylene rubbers have found application (see Chapters 11 and 31). On the other hand, where enhanced heat resistance and surface hardness are required in conjunction with excellent impact properties, polycarbonate-ABS alloys (see Section 20.8) have found many applications. These materials have also replaced ABS in a number of electrical fittings and housings for business and domestic applications. Where improved heat distortion temperature and good electrical insulation properties (including tracking resistance) are important, then ABS may be replaced by poly(butylene terephthalate). 

Other blends such as with poly (butylene terephthalate) and poly(phenylene sulphide) which are niche materials not further discussed in this chapter. 

With the expiry of the basic ICI patents on poly(ethylene terephthalate) there was considerable development in terephthalate polymers in the early 1970s. More than a dozen companies introduced poly(butylene terephthalate) as an engineering plastics material whilst a polyether-ester thermoplastic rubber was introduced by Du Pont as Hytrel. Polyfethylene terephthalate) was also the basis of the glass-filled engineering polymer (Rynite) introduced by Du Pont in the late 1970s. Towards the end of the 1970s poly(ethylene terephthalate) was used for the manufacture of biaxially oriented bottles for beer, colas and other carbonated drinks, and this application has since become of major importance. Similar processes are now used for making wide-neck Jars. 

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