P-Hydroxybenzoic acid copolymer

Ethylene terephthalate/p-hydroxybenzoic acid copolymer polycarbonate-bisphenol-A and trichloromethane 88SCH... 

ET-pHBA Etbylene terepbtbalate/p-hydroxybenzoic acid copolymer 170-171... 

Kaneda et al. synthesized [61] a series of high molecular weight extended chain copolyimides (XV) by the reaction of PMDA and 3,3, 4,4 -biphenyltetra-carboxylic dianhydride (PPDA) with 3,3 -dimethyl-4,4 -diaminobiphenyl. Solvents used for the one-step synthesis to the fully cyclized imide structure were phenol, p-chlorophenol, m-cresol, p-cresol and 2,4-dicholorophenol. The polycondensations were performed at 180°C for 2h with a monomer concentration of 6% by weight and p-hydroxybenzoic acid used as a catalytic accelerator. A maximum of 50 mol % of PMDA could be used before the copolymer precipitated from solution. Reconstituted copolymers as isotropic dopes (8-10% by weight) in p-chlorophenol were dry-jet wet spun between 80 and 100 °C [62]. 

Among the many different classes of thermotropic polymers, only a limited number of polyesters based on aromatic ester type mesogenic units have been studied by rheological methods, beginning with the publication by Jackson and Kuhfuss of their work on the p-oxybenzoate modified polyethylene terephthalate, PET, copolymers. They prepared a series of copolyesters of p-hydroxybenzoic acid, HBA, and PET and measured the apparent melt viscosity of the copolymers as a function of their composition by use of a capillary rheometer. On inclusion of low levels of HBA into PET, the melt viscosity increased because of partial replacement of the more... 

Fig. 12. Viscosity Versus Mesogenic Comonomer Concentration of Copolymers of Ethylene Tereph-thalate and p-Hydroxybenzoic Acid (after Jackson and Kuhfuss)...

The samples used in the present study are (1) a copolymer consisting of p-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA) in the mole fraction ratios 73 27 and (2) a polymer which contains HBA, HNA, terephthalic acid (TA) and hydroquinone (HQ) in the ratios 57 41 1 1. It will be shown later that the incorporation of the small amount of TA and HQ into the latter structure makes the material less shear—thinning than the copolymer containing only HBA and HNA, when examined theologically. It is generally believed that a random sequence distribution of monomers occurs in both... 

Thermally stable copolymers of 3-(trimethylsiloxyl)- and 3,5-bis(trimethylsiloxyl)benzoyl chloride (4A) or 3-acetoxy- and 3,5-diace-toxy-benzoic acid (4B) were prepared with mole ratios of AB AB2 monomer ranging from 160-5.32 Polymers containing 10-20 mole % of branching monomers were insoluble in CHC13 but soluble in polar solvents, such as A,A-dimethylformamide (DMF) or a mixture of pyridine and benzene. Compared to the linear homopolymer of 3-hydroxy-benzoic acid, the branched polymer showed lower crystallinity and slower crystallization. There was an inverse linear relationship between percent crystallinity and the number of branches in the chain. Similarly, in an attempt to improve moldability and decrease anisotropy of rigid aromatic polyesters, 0.3-10 mole % of 1,3,5-trihydroxybenzene, 3,5-di-hydroxybenzoic acid, and 5-hydroxyisophthalic acid were copolymerized with p-hydroxybenzoic acid/terephthalic acid/4,4 -dihydroxy-diphenyl.33 The branched polymer showed a lower orientation and possessed improved flex properties. 

The crosslinked copolymer just described does not have sufficient flow for injection molding. If the crosslinking step is eliminated, the copolymer can be injection molded, but only with considerable difficulty. Also, the parts obtained have poor strength above 300°F. It was felt that an all para system was necessary to overcame the poor hot strength. The combination of monomers that provided optimum properties and processability was found to be terephthalic acid, p-hydroxybenzoic acid, and a dihydroxy aromatic. Hie synthesis can be cartied out in the melt, or in a heat exchange medium. The product has a fairly sharp melting... 

Yamato Masafumi, Murohashi Ritsuko, Kimura Tsunehisa, Ito Eiko. (1997). Dielectric P-Relaxation in Copolymer Ethyleneterephthalate-p-hydroxybenzoic Acid. J. Polym. Sci. Technol, 54(9), 544-551. 

Finally, results of structural investigations on random copolymers were recently reported.X-ray methods were used to investigate the physical structure of high strength melt-spun liquid crystalline aromatic copolyester fibers prepared from p-hydroxybenzoic acid (B), 2,6-dihydroxynaphthalene (N) and terephthalic acid (P)... 

X-ray diffraction patterns of fibers spun from liquid crystalline melts of p-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (HNA) show a high degree of axial orientation. Several meridional maxima are detected which are aperiodic and also change in position and number with the monomer composition. The positions of these maxima can be predicted by calculating the theoretical scattering of random copolymer chains, in which the residues are represented by points separated by the monomer lengths. Both peak positions and intensities are reproduced when intraresidue interferences are allowed for in an atomic model for the random chains. This procedure also allows determination of the stiff-chain persistence (or correlation) length from the breadth of the maximum at d=2.lA which increases from 9 to 13 residues as the HBA content is increased from 25 to 75%. 

The relaxation behavior of nematic, longitudinal PLCs is greatly complicated by their multiphase character. The presence of both crystallites and a coexisting isotropic component has been reported [32]. Vectra A (poly(p-hydroxybenzoic acid-co-2,6-hydroxynaphthoic acid)), currently one of the more widely used and studied commercial polymers, exhibits, despite that fact that it is a statistical copolymer, a sizeable amount (10-60%) of crystallinity, either of the non-periodic layer type [121] or of a truly statistical type according to the model of Biswas and Blackwell [122]. It has become clear that the relaxation of oriented Vectra is to a substantial degree controlled by the thermal behavior of its tiny crystallites. 

In this and the following two sections we consider the data for a PLC and for different blends of that PLC with isotactic polypropylene (PP). The PLC used in this study was liquid crystalline copolyester PET/0.6PHB, where PET = poly (ethylene terephthalate), PHB = p-hydroxybenzoic acid and 0.6 is the mole fraction of PHB in the copolymer, manufactured by Unitika Ltd, Kyoto, Japan. The content of the PLC in the blends with PP was varied from 0 to 20 wt%. The samples were prepared by injection molding. PP, resin VB65 llB, was supplied by Neste OY, Finland. 

The homopolymer has a melting temperature of at least 550° C. It is insoluble in all known solvents and is exceptionally thermally stable. The metal-like polymer, however, can only be worked by hammering, sintering, or plasma spraying. For this reason, more easily processed copolymers of p-hydroxybenzoic acid with isophthalic acid, hydroquinone, terephthalic acid, orp,p-diphenyl ether with correspondingly changed mechanical properties have been made. Industrially, these polymers are often referred to briefly as aromatic polyesters. ... 

Research centred on copolymers of terephthalic acid, isophthalic acid, bisphenols, and p-hydroxybenzoic acid to provide materials with the... 

In some cases it is possible to directly polycondense acid and phenols evolving water at about 300 C [41]. This process works well when catalysed with compoimds of group IV or V metals tin salts are preferred, especially dialkyl tin dialkanoates or oxides. The process is not really suitable if p-hydroxybenzoic acid is involved because this can imdergo decarboxylation at >200 "C. The polymerisation is not affected because the phenol formed volatilises at the high temperatures involved, but the resultant polyester will contain less than the anticipated mole ratio of hydroxybenzoate-derived units. Hydroxynaphthoic acid does not suffer from this problem, and direct esterification processes may be used if non-benzoate copolymers are required [42]. 

Investigations of the thermal degradation of copolymers of p-hydroxybenzoic acid with 2,6-hydroxynaphthoic acid [105-108], and of the naphthoic homopolymer [128] showed similar results, indicating complex random chain scission processes. 

The copolymer of ethylene oxide with p-hydroxybenzoic acid gives a poly(ester ether) fiber. 

In Section 24.1 we have defined ways of prediction of long-term behavior from short-term tests. Let us now provide more examples of application of these concepts. Creep and stress relaxation have been determined for PET/ 0.6PHB, where PET is the poly(ethylene terephthalate), PHB, the p-hydroxybenzoic acid, and 0.6 is the mole fraction of the latter in the copolymer [58]. PET/0.6PHB is a polymer liquid crystal, see chapter 41 on PECs in this Handbook. In temperature ranges of interest it forms 4 coexisting phases [60]. Conventional wisdom said that prediction methods work only for so-called rheologically simple materials, practically for one-phase polymers. Therefore, we have decided to apply as severe a test as possible to our prediction methods and a multiphase PLC is a good choice. 

Semiflexible polymers—including regular AB type copolymers in which A is rigid while B flexible. Cellulose derivatives belong here, as well as poly(p-hydroxybenzoic acid) (PHB), and for instance poly(p-phenylene terephtha-lamide). They are of course stronger than flexible polymers, but their processing is more difficult. 

Three commercially available thermotropic liquid crystalline polymers (TLCPs) were presented as examples in this section. They are Hoechst Celanese Vectra A950 and Vectra B950 as well as Amoco Xydar . Vectra A950 is a random copolymer of 73 mol% 4-hydroxybenzoic acid and 27 mol% 6-hydroxy-2-naphthoic acid, and Vectra B950 is a random copolyesteramide consisting of 60 mol% of 6-hydroxy-2-naphthoic acid, 20 mol% terephthalic acid, and 20 mol% p-aminophenol. Xydar is made from p-hydroxybenzoic acid, isophthalic and/or terephthalic acids, and 4,4 -biphenol. The repeating unit structures of the three LCPs are shown in Figure 6.2. 

Such is not the case in blends of two liquid crystal polymers or LCP s that were first extensively studied by DeMeuse and Jaffe. In their initial study (DeMeuse and Jaffe 1988), they examined blends of LCP s that contain copolymers of p-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA) of different copolymer ratios. It was surmised that miscibility in the melt state depended on the difference in copolymer ratios between the two component polymers. However, miscibility in the solid state seemed to be present for all blends that were studied. This is an interesting contrast to the systems previously mentioned because there is no obvious enthalpic interaction that is occurring between the two blend components. 

Another example is a copolymer of p-hydroxybenzoic acid,p,p -biphenol, and terephthalic acid, creating the polyester structure... 

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