Polybutylene terephthalate properties

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. 

In addition to the desired polymerization reaction, the dialcohol reactants can participate in deleterious side reactions. Ethylene glycol, used in the manufacture of polyethylene terephthalate, can react with itself to form a dialcohol ether and water as shown in Fig. 24.4a). This dialcohol ether can incorporate into the growing polymer chain because it contains terminal alcohol units. Unfortunately, this incorporation lowers the crystallinity of the polyester on cooling which alters the polymer s physical properties. 1,4 butanediol, the dialcohol used to manufacture polybutylene terephthalate, can form tetrahydrofuran and water as shown in Fig. 24.4b). Both the tetrahydrofuran and water can be easily removed from the melt but this reaction reduces the efficiency of the process since reactants are lost. 

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. 

How do polyethylene terephthalate and polybutylene terephthalate differ from one another chemically How do these differences affect their properties ... 

What properties of polybutylene terephthalate make it amenable to injection molding processing ... 

Figure 6.2 The polyesteramide structure proposed by Gaymans and co-workers E, ester group A, amide group [21]. Reprinted from Polymer, 38, van Bennekom, A. C. M. and Gaymans, R. J., Amide-modified polybutylene terephthalate structure and properties, 657-665, Copyright (1997), with permission from Elsevier Science...

C.M. Benson and R.P. Burford, Morphology and properties of acrylate styrene acrylonitrile/polybutylene terephthalate blends,. Mater. Sci.,... 

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. 

Hahgenated polymers, both brominated and chlorinated, have been developed to yield better polymer compatibility, improve physical properties, and long-term-aging characteristics in many thermoplastic resins, particularly the high-performance engineering thermoplastics, such as nylon, polybutylene terephthalate (PBT) and polyethylene terephthalate (PET). These materials still use antimony oxide as a synergist to achieve the desired flame resistance (31). 

Apart from ZHS and ZS, little work has generally been undertaken on tin-based Are retardants in nonhalogen polymer systems. However, certain tin(II) compounds have shown excellent flame-retardant and smoke-suppressant properties when incorporated at levels of 20-30% into aromatic polyesters, specifically polybutylene terephthalate (PBT). Hence, tin(ll) oxide, tin(II) oxalate, and tin(II) phosphate have been shown to markedly increase flame retardancy in PBT, whereas, interestingly, tin(IV) oxide is almost totally ineffective in the same polymeric substrate. 

Moldability of aryl polyesters have also been improved by the use of polybutylene terephthalate (PET) instead of PET or by the use of blends of PET and PET. PET under the trade name of Celanex, Valox, Gafite and Versel is being produced at an annual rate of 25 thousand tons. Copolymers of carbonate and aryl esters, acrylics and aryl esters, and imide and aryl esters as well as physical blends of polyesters and other polymers are available. These aryl polyesters are being used for bicycle wheels, springs, and blow molded containers. The properties of typical aryl polyesters are as follows ... 

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. 

PET/PBT (polyethylene terephthalate/polybutylene terephthalate) good colorabUity, excellent surface aesthetics, gloss, chemical resistance, impact, and electrical properties. Apphcations include appliances, electrical apphcations, building and construction. 

Linear aliphatic chols are widely used as raw materials for polymers. Polymers synthesized from even-carbon diols tend to show excellent polymer properties. 1,4-Butanediol is very important as raw material for various polymers such as urethanes and polybutylene terephthalate (PBT), which is an engineering plastic. Since Celanese Corporation described a PBT resin in 1970, the demand for PBT resin, which is mainly used for automotive, electrical, and electronic equipment parts, has been expanding rapidly [1]. THF is also a major 1,4-butanediol derivative as a raw material for poly(tetramethylene ether) glycol used for artificial leather and elastic fibers in addition to being a high-performance solvent. Significant growth in demand for these 1,4-butanediol derivatives is expected in Asia, primarily in China. 

Thermoplastic polyesters include polybutylene terephthalate (PBT), which possesses good slip and wear properties, resists chemicals and hydrolysis, and has excellent dimensional stability. Mechanical parts in drug delivery and filter systems are preferably made of PBT. 

The popular thermoplastic polyesters are polybutylene terephthalate (PBT) and polyethylene terephthalate (PET). TP polyesters are in a family of polyesters that has widely varying and important range of properties. There are the two major groups of the TPs (with comparatively high melting points) and the TSs (which are usually typified by a cross-linked structure). TP polyesters are often called saturated polyesters to distinguish them from unsaturated polyesters that are the TSs. 

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 ... 

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. 

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