Amorphous polyarylates

This polyester class comprises amorphous high-Tg copolyesters, known as amorphous polyarylates, and semicrystalline polyesters that often exhibit anisotropic hquid crystalline (LC) melts. Liquid crystalline polyesters are often termed as polyester LCPs. 

Although many other monomers have been utilized, the typical commercial amorphous polyarylate is a polyester containing bisphenol-A units and nearly equal proportions of isophthalate and terephthalate units (Formula 2.1).6... 

Amorphous polyarylates are light-amber transparent materials which exhibit mechanical properties comparable to that of unfilled PET in terms of tensile or flexural strength and modulus (Table 2.13) but are notably superior in terms of heat resistance (HDT = 174°C vs. 85°C for PET) and impact strength. 

Numerous blend formulations with amorphous polyarylate as one of the components have been described6 and are generally claimed to exhibit improved UV and weather resistance, improved molding performance characteristics, and... 

Blend formulations, with amorphous polyarylates, 47-48 Block copolyesters, 18 Block copolymers, 6, 20... 

Figure 19.12 Relationship between the heat distortion temperature (HDT) (at 1.82 MPa) and Tg for the amorphous polyarylates of HBA/Ph-HQ or fBu-HQ/HQ/ BB and the crystalline polyarylate of Ph-HQ/BB [33]...

The authors of Ref. [21] supposed, that in orientational drawing process of poly(metyl methacrylate) (PMMA) the following structure changes occur the transition to more equilibrium structure owing to molecular package improvement and internal stresses relaxation. The quantitative structural model absence not allows the authors of Ref [21] to give direct proofs of their suppositions. In Ref [22] such treatment was fulfilled on the example of extruded amorphous polyarylates DV and DF-10 with the cluster model of polymers amorphous state structure using [12, 23],... 

PC is more resistant to strong acids but is less stable than polyterephthalates (PET, PBT) to benzene and methanol. PET, polyethylene terephthalate, is a hard, stiff homopolymer, whilst PBT, polybutylene terephthalate is somewhat softer. Further materials in this group include, i) thermoplastic poly (ether) ester elastomers, included in the TPE grouping, ii) amorphous polyarylates, and Hi) self-reinforced crystalline polyarylates (LCP). Polycarbonate may be blended with various styrenics (PC/ABS, PC/ASA, PC/SMA). 

Fig. 1. Engineering resins cost vs annual volume (11) (HDT, °C) A, polyetheretherketone (288) B, polyamideimide (>270) C, polyarylether sulfone (170- >200) D, polyimide (190) E, amorphous nylons (124) F, poly(phenylene sulfide) (>260) G, polyarylates (170) H, crystalline nylons (90—220) I, polycarbonate (130) J, midrange poly(phenylene oxide) alloy (107—150) K, polyphthalate esters (180—260) and L, acetal resins (110—140).

Many engineering thermoplastics (e.g., polysulfone, polycarbonate, etc.) have limited utility in applications that require exposure to chemical environments. Environmental stress cracking [13] occurs when a stressed polymer is exposed to solvents. Poly(aryl ether phenylquin-oxalines) [27] and poly(aryl ether benzoxazoles) [60] show poor resistance to environmental stress cracking in the presence of acetone, chloroform, etc. This is expected because these structures are amorphous, and there is no crystallinity or liquid crystalline type structure to give solvent resistance. Thus, these materials may have limited utility in processes or applications that require multiple solvent coatings or exposures, whereas acetylene terminated polyaryl ethers [13] exhibit excellent processability, high adhesive properties, and good resistance to hydraulic fluid. 

Polyarylate It is a form of aromatic polyester (amorphous) exhibiting an excellent balance of properties such as stiffness, UV resistance, combustion resistance, high heat-distortion temperature, low notch sensitivity, and good electrical insulating values. It is used for solar glazing, safety equipment, electrical hardware, transportation components and in the construction industry. 

Amorphous bisphenol-A polyarylates are soluble in dioxane and in chlorinated solvents such as CH2C12, 1,2-dichlororethane, 1,1,2-trichloroethane, and 1,1,2,2-tetrachloroethane while semicrystalline and liquid crystalline wholly aromatic polyesters are only sparingly soluble in solvents such as tetrachloroethane-phenol mixtures or pentafluorophenol, which is often used for inherent viscosity determinations. 

Statistical copolymerization of ethylene glycol and 1,4-butanediol with dimethyl ter-ephthalate results in products with improved crystallization and processing rates compared to poly(ethylene terephthalate). Polyarylates (trade names Ardel, Arylon, Durel), copolymers of bisphenol A with iso- and terephthalate units, combine the toughness, clarity, and proce-sibility of polycarbonate with the chemical and heat resistance of poly(ethylene terephthalate). The homopolymer containing only terephthalate units is crystalline, insoluble, sometimes infusible, and difficult to process. The more useful copolymers, containing both tere- and isophthalate units, are amorphous, clear, and easy to process. Polyarylates are used in automotive and appliance hardware and printed-circuit boards. Similar considerations in the copolymerization of iso- and terephthalates with 1,4-cyclohexanedimethanol or hexa-methylene diamine yield clear, amorphous, easy-to-process copolyesters or copolyamides,... 

They are atactic amorphous polymers which have good light transparency (92%) and yield transparent moldings and films. As was noted for polyalkyl acrylates, the solubility parameters decrease as the size of the alkyl groups increases. The flexibility also increases as one goes from polymethyl methacrylate (PMMA) to polyaryl methacrylate and then decreases as the size of the alkyl group is further increased. 

Polyarylates (PAr) are wholly aromatic polyesters derived from aromatic dicarboxylic acids and diphenols or their derivatives. They are amorphous in nature with good injection moldability. Figure 7 shows the typical formula structure of PAr. 

POLYARYLATES. These are clear, amorphous thermoplastics that combine clarity, high heat deflection temperatures, high impact strength, good surface hardness, and good electrical properties with inherent ultraviolet stability and flame retardance. No additives or stabilizers are required to provide these properties. Polyarylates are aromatic polyesters that are manufactured from various ratios of iso- and terephthalic acids with bisphenol A.1 The resultant products are free-flowing pellets which can be processed by a variety of thermoplastic techniques in transparent and... 

Zoller, P., "A Study of the Pressure-Volume-Temperature Relationships of Four Related Amorphous Polymers Polycarbonate, Polyarylate, Phenoxy, and Polysulfone," J. Polym. Sci., Polym. Phys. Ed., 20, 1453 (1982). 

Polyaryl(ether-ketone-carbaborane)s have also been synthesized by using CF3SO3H as both solvent and catalyst to give linear amorphous polymers [Eq. (54)] [163]. These polymers have low molecular weights (IV = 0.24-0.59) and low thermolytic weight loss upon pyrolysis (10-15% at 1000° C)... 

The epsilon CTPZ, however, is a special case which requires the shearing process to be activated at the same time that a craze is developing and in locations directly adjacent to the craze. This is unusual since both craze and shear band initiate from essentially the same location, the crack tip. The same polymer can exhibit either the DCG process without epsilon plastic zones or the DCG process with epsilon plastic zones depending upon the conditions existing at the crack tip. Epsilon CTPZs have been identified in several ductile amorphous polymers BPA-polycarbonate " " , BPA-polyestercarbonate polyphenylsulfone and BPA-polyarylate... 

A whole series of high-performance polyester LCPs was introduced in 1985. They were assembled from p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. Polyarylates (PARs) - amorphous phenolic esters derived from aromatic dicarboxylic acids (mixtures of terephthalic acid and isophthalic acid) and biphenols such as bisphenol A - are produced by Amoco (Ardel ), Celanese (Durel ) and DuPont (Arylon ) at a volume of approx. 2000 t/a. 

Aromatic polyesters having an amorphous molecular structure. Compared with other amorphous engineering plastics in terms of heat resistance, polyarylates are generally positioned between polycarbonate on the low side and sulfone and polyether polymers on the high side. Compared with crystalline and semi-crystalline engineering plastics, polyarylate resins offer better resistance to warping, and generally comparable mechanical properties. 

This Figure notes that combinations of amorphous (high T ) engineering polymers (e.g., PPE, polycarbonate, polyarylate) with lower T crystalline polymers (e.g., polyamide-66, polybutyleneterephthalate), offers the modulus-temperature behavior desired for the noted application. 

As an example of fractality displayed in polymers at a macroscopic level (a secondary structural element), we shall consider the growth of a crack in a film of amorphous vitreous polyarylate-sulfone [100] (see Figure 11.6). 

The authors [105] used amorphous glassy polymers PMMA, polycarbonate (PC) and polyarylate (PAr). The necessary for further evaluations shear modulus values G were obtained according to Young s modulus E experimental values with the formula using [88] ... 

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