Polybutylene terephthalate applications

Polyesters, which are a class of engineering thermoplastics, are found in a wide variety of applications including carbonated drink bottles, fibers for synthetic fabrics, thin films for photographic films and food packaging, injection molded automotive parts, and housings for small appliances. In this chapter, we svill explore the synthesis of this class of polymers. We will also look at the typical properties and end uses for the most common of these resins, polyethylene terephthalate and polybutylene terephthalate, which are commonly known as PET and PBT, respectively. 

Polyethylene terephthalate is most often extruded into films or fibers, or blow molded into bottles. Polybutylene terephthalate is primarily found in injection molded parts. Such parts are highly crystalline, which makes them opaque. Polybutylene terephthalate is often modified with glass fibers or impact modifiers. Table 24.1 contains applications by processing method and resin. 

Table 24.1 Applications of polyethylene terephthalate and polybutylene terephthalate by processing method...

Typically, polyester resins are used for high-end applications that require excellent electrical and thermal resistance. When dimensional stability under load is more critical, glass fibers are incorporated to increase the heat distortion temperature and the stiffness of the part. Examples of glass fiber reinforced parts include electrical housings, electrical adapters, computer components, telephone housings, and light bulb sockets. When impact modified, polybutylene terephthalate can be injection molded to make car bumpers. 

Polyesters exhibit excellent high temperature strength and electrical properties making them a good choice for many demanding applications. They also are physiologically inert allowing them to be used in food contact applications. The two common polyesters, polyethylene terephthalate and polybutylene terephthalate, are both used in injection molded products. Polyethylene terephthalate is often used in both extrusion and blow molded processes also. 

The most recent entrant-to the. club of commodity chemicals is 1,4-butanediol (BDO), a petrochemical used in some of the more specialized applications such as chemical intermediates for the production of tetrahydro-furane and gama-butyrolactone, polybutylene terephthalate, and the more familiar polyurethanes. Traditionally, the Reppe process was the primary route to BDO, based bn acetylene and formaldehyde feeds. More recently, the share of BDO from butane and propylene oxide based production has grown rapidly. 

PTT is used in apparel, upholstery, specialty resins, and other applications in which properties such as softness, comfort stretch and recovery, dyeability, and easy care are desired. The properties of PTT surpass nylon and PET in fiber applications, and polybutylene terephthalate and PET in resin applications such as sealable closures, connectors, extrusion coatings, and blister packs (14). 

For conventional technical applications aromatic polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) are widely used. But these polymers are biologically inert and thus not directly applicable as biodegradable plastics. Combining both the excellent material properties of aromatic polyesters and the potential biodegradability of aliphatic polyesters has led to the development of a number of commercially available aliphatic-aromatic co-polyesters over the last decade or so. 

Aliphatic polyesters like polycaprolactone (PCL) or polybutylene adipate (PBA) are readily biodegradable, but because of their melting points of 60 °C are unsuitable for many applications. On the other hand, aromatic polyesters like polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) have high melting points above 200 °C and very good material properties, but are not biodegradable. 

The most important commercial blends of BPA-PC are poly(acrylonitrile-butadiene-styrene) (PC/ABS) and polybutylene terephthalate (PC/PBT) or polyethylene terephthalate (PET). Commercial grades of PC/ABS include CYCOLOY (GE), Bayblend (Bayer), and PULSE (Dow). PC/ABS blends exhibit improved flow and processability and enhanced low-temperature impact strength in comparison to PC (Fig. 3). These blends are widely used in applications requiring enhanced impact resistance, such as interior automotive parts and computer and electronics applications such as computer housings and cell phones. Non-halogenated flame-retardant PC/ABS blends are widely available. Poly(acrylic-styrene-acrylonitrile) (PC/ ASA) blends (GELOY , GE Luran , BASF) provide improved weatherability for outdoor applications such as exterior automotive parts, but exhibit reduced impact performance at low temperatures in comparison to PC/ABS. PC/PBT or PET blends (XENOY , GE Makroblend , Bayer) provide enhanced chemical resistance and weatherability for applications such as lawn and garden equipment and automotive bumpers and fasdas. 

Reinforced PET- Thermoplastic polyesters based on polyethylene terephthalate. Closely related in terms of chemistry, properties, and areas of application to reinforced polybutylene terephthalate (PBT) compounds. Key distinguishing features are higher strength properties and higher use temperatures. 

A commercial blend of SMA and polybutylene terephthalate (Table 15.8) was also offered for applications requiring solvent resistance, which the crystalline PBT provided. This blend lacked adequate compatibility and hence its impact strength is relatively poor. 

Plastics find extensive use in several areas of fiber optic cables. Buffer tubes, usually extruded from high-performance plastics such as fluoropolymers, nylon, acetal resins, or polybutylene terephthalate (PBT) are used for sheathing optical fibers. A blend o PVC and ethylene vinyl acetate (EVA) polymer, such as Pantalast 1162 of Pantasote Incorporated, does not require a plasticizer, which helps the material maintain stability when in contact with water-proofing materials. PVC and elastomer blends, Carloy 6190 and 6178, of Cary Chemicals are also used for fiber optic applications (Stiffening rods for fiber optics are either pultruded epoxy and glass or steel. Around these is the outer jacketing, which is similar to conventional cable.)... 

The high impact strength, dimensional stability and optical clarity (low crystallinity) of bisphenol-A polycarbonate (PC) together with its low dielectric loss have led to a range of applications embracing optical components, CD-ROMs, film capacitors and safety-related products Subsequent market demands for enhanced physical properties has stimulated the development of a range of commercial blends of which rubber-modified bisphenol-A polycarbonate (PC) with polybutylene terephthalate (PBT) or polyethylene terephthalate (PET) are amongst the more successful ... 

To summarize, many fibre-reinforced thermoplastics are not suitable for extended exterior exposure where the maintenance of appearance is important unless their surface is protected. Some unprotected applications that are found include car door handles, rear-view mirror housings and body panels (for all of which polyamides, polyethylene terephthalate and polybutylene terephthalate are used), as well as parts for caravans, boats and snowmobiles. 

Polybutylene terephthalate (PBT) is one of the engineering thermoplastic polyesters that offers excellent performance for a variety of applications. Compounding of PBT with PO provides impact modification depending upon the type of PO used and the suitability of the compatibiliser [22-28]. 

Let us first review various thermoplastics used in automotive applications. These include nylon 6,6-based blends (e.g., nylon 6,6-PPO), glass-filled nylon 6,6 with without impact modifiers, homo- and copolymers of PP, polybutylene terephthalate (PBT), polyethylene (PE), bis-phenol A polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), PC-ABS blends, glass-filled PP, and ABS. 

The electrical properties of LCPs and polybutylene terephthalate (PBT) resins are comparable although LCPs offer at least a few advantages over PBT in electric applications, i.e., low mold shrinkage, fast cycling time, ease of molding thin parts, low moisture regain, and excellent chemical and mechanical properties. 

Polybutylene terephthalate (PBT) is different from PET with the substitution of four ethylene repeat units rather than the two in PET. This feature imparts additional flexibility to the backbone and reduces the polarity of the molecule, resulting in mechanical properties similar to those of PET. PBT blends such as PBT/ASA (acry-lonitrile/styrene/acrylic ester) are popular in automotive exterior and under-hood applications. 

It is known that, the polybutylene terephthalate (PBT) is one of the perspective and universal thermoplastic polymers belonging to polyesters. It is produced industrially in wide scale and has different applications as a constructional material. The growing world wide... 

Chapter 7, Polybutylene Terephthalate, from LG Chem, describes the science and technology of PBT blends, compounds, and composites. The chapter offers details on the advantages of different polymer blends, types of fiber, and mineral and fiber-mineral hybrid reinforcements as well as chemical and hydrolysis resistance, flammability, and other PBT attributes. The author states that the most important apphcations of PBT are automotive and electrical, electronics and telecommunications, as well as precision engineering and general mechanical engineering, and concludes that the ability to modify for various applications, combined with a range of reinforcement and blend, has enabled PBT as one of the most widely used engineering polymers. ... 

Engineering thermoplastic resins (ETP) are those whose set of properties (mechanical, thermal, chemical) allows them to be used in engineering applications. They are more expensive than commodity thermoplastics and generally include polyamides (PA), polycarbonate (PC), linear polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyphenylene ether (PPE) and polyoxymethylene (POM). Specialty resins show more specialized performance, often in terms of a continuous service temperature of 200°C or more and are significantly more expensive than engineering resins. This family include fluoropolymers, liquid crystal polymers (LCP), polyphenylene sulfide (PPS), aromatic polyamides (PARA), polysulfones (P ), polyimides and polyetherimides. 

Polybutylene terephthalate 30% carbon fiber reinfOTced Ultra-high-strength and -stiffness applications... 

Xenoy PC/PBT blends are mainly characterized by the partial miscibility of blsphenol A polycarbonate and polybutylene terephthalate, stabi lization and impact modification technology being applied to upgrade properties to the need of the applications. 

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