Poly ethylene-2,6-naphthalate

Poly(ethylene-2,6-naphthalate) (4.60) under UV irradiation is photodegraded by a mechanism analogous to that for poly(ethylene terephthalate) (cf. section 4.6.3) [81, 1664]. 

PEN was first described in 1948. Conunercially, PEN is prepared by a two-step reaction consisting of  

Esterification between 2,6-naphthalene dicarboxylic acid and glycol to obtain a low-molecular-weight esterified compound, and 

Polycondensation reaction of the esterified compound to obtain a higher molecular weight PEN product. 

Either NDC or the acid itself can be used. Using the dimethyl ester, zinc acetate or manganese acetate as a catalyst at a reaction temperature of 180-260°C is needed to produce (jS-hydroxyethyl)naphthalate, or its low-molecular-weight prepol5mier. When the acid is used, no catalyst is needed for the first step of esterification. 

After the esterification, the low-molecular-weight esters can be readily polycondensed in the presence of a polymerization catalyst, such as antimony trioxide at a reaction temperature of 280-300°C at a reduced pressure of less than 1 torr to produce a high-molecular-weight polymer.  

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Poly(ethylene naphthalate) (PEN), 20, 21, 25. See also PEN entries structure and properties of, 44-46 Poly(ethylene oxide) (PEO), 359 Polyethylenes... 

In addition to the crystal forms, X-ray scattering studies indicate that when unoriented PEN fiber was drawn at 120 °C ( 7 g), a mesophase is generated. In this form, the molecular chains are in registry with each other in the meridional direction but not fully crystallized in the equatorial direction. This conclusion was based on the presence of additional meridional peaks not accounted for by the crystal structure obtained by X-ray scattering. The mesophase is a intermediate phase and its existence is strongly dependent upon the processing conditions consequently, it could have implications with respect to the properties of commercially produced fibers and films, since it appears to be stable and not easily converted to the crystalline form, even at elevated temperature [25, 26], The mesophase structures of PET, PEN and poly(ethylene naphthalate bibenzoate) were compared by Carr et al. [27], The phase behavior of PEN and PEN blends with other polymers has also been studied [28-32],... 

Bicakci, E., Zhou, X. and Cakmak, M., Phase and uniaxial deformation behavior of ternary blends of poly(ethylene naphthalate), poly(ether imide) and poly(ether ether ketone), in Proceedings of the 55th SPE ANTEC 97 Conference, May 5-8, 1997, Toronto, ON, Canada, Society of Plastics Engineers, Brookfield, CT, 1997, Vol. 2, pp. 1593-1599. 

Chuah et al. [107] prepared a series of PTT/poly(trimethylene napthalate) (PTN) copolyesters by copolymerizing PDO with dimethyl terephthalate and dimethyl naphthalate. The PTN homopolymer has a 7 g of 75 °C and a Tm of 245 °C. Despite the more rigid napthalate moiety, the PTN Tg and Tm were much lower than the Tg of poly(ethylene naphthalate) (PEN), indicating the strong influence of the flexible trimethylene units. 

The modification of PET with naphthalene-2,6-dicarboxylic acid and other additional comonomers is a common measure in bottle manufacturing. Copolyesters based on this compound show excellent barrier properties. Such materials can be produced by addition of the desired amount of comonomer during polymer processing or by blending PET with poly(ethylene naphthalate) (PEN). Additionally, PEN can also be modified by other comonomers such as isophthalic acid (IPA) to improve the flow properties and reduce the melting point. The high price of naphthalene dicarboxylic acid is the reason for its limited application. The overall cost may be reduced by using TPA or IPA as comonomers. 

While depolymerizing poly(ethylene naphthalate) could be attractive on the small scale because of the high commercial price for the naphthalate moiety, even this candidate resin is in too little availability to permit economical depolymerization. Of polyesters, only poly(ethylene terephthalate) (PET) is available at sufficient quantities to make the commercial use of depolymerization potentially attractive. 

Depolymerization processes have been proposed for poly(butylene terephtha-late) by the glycolysis of PBT with 1,4-butanediol and a titanium catalyst [65]. Methanolysis of poly(ethylene naphthalate) to dimethyl naphthalate and ethylene glycol has also been proposed [66, 67], but not implemented. The lack of commercial depolymerization of PEN is probably due not to technical limitations, but to insufficient supplies of PEN polymer feedstock to meet the minimum quantities needed for economical operations. 

It should additionally be noted that a number of the paths of the schemes above have received some confirmation in a number of literature reports dealing with the photolysis and photo-oxidation of other polyesters [32-35], Because these reports investigated poly(butylene terephthalate) (PBT), poly(ethylene naphthalate) and poly(butylene naphthalate), however, they may not have direct application to understanding of the processes involved in PET and PECT and so have not been discussed in this present chapter. All do contain support for the formation of radicals leading to CO and C02 evolution, as well as the hydrogen abstraction at glycolic carbons to form hydroperoxides which then decompose to form alkoxy radicals and the hydroxyl radical. These species then were postulated to undergo further reaction consistent with what we have proposed above. 

Poly(ethylene naphthalate) (PEN) is also completely analogous to PET except that it incorporates a naphthalene group in its main structure as opposed to a phenyl group. The naphthalene unit stiffens the backbone and gives PEN a higher glass transition temperature and improved mechanical properties when compared to PET (see Chapters 9 and 10). 

Poly(ethylene terephthalate) (PET), eg. DuPont Teijin Films Melinex polyester film, and poly(ethylene naphthalate) (PEN), eg. DuPont Teijin Films Teonex polyester film, are biaxially oriented semicrystalline films [1], The chemical structures of PET and PEN are shown in Fig. 7.1. 

This deficiency is overcome by application of a hard coat to the amorphous resins this substantially improves resistance to the solvents and chemicals such as NMP, IPA, acetone, methanol, THF, ethyl acetate, 98% sulfuric acid, glacial acetic acid, 30% hydrogen peroxide, and saturated bases such as sodium hydroxide [13]. With poly(ethylene terephthalate) and of poly(ethylene naphthalate) films a hard coat is not required for solvent resistance. 

One of the main drivers in moving to plastic substrates is that it opens up the possibility of roll-to-roll processing and the process and economic advantages that this brings. Under these conditions a winding tension will clearly be present and polymer film substrates with low moduli will be susceptible to internal deformation, particularly at elevated process temperatures. Figure 7.8 shows a comparison between poly(ethylene terephthalate) and poly(ethylene naphthalate) films. 

Although there have been several examples of flexible OLED displays on plastics, including passive-matrix OLED displays on poly(ethylene terephthalate) (PET) substrates from Pioneer and Universal Display Corporation [26, 27], and a-Si H TFT-driven monochrome active-matrix OLED displays on poly(ethylene naphthalate) (PEN) from Honeywell [28], there have been no demonstrations of organic TFT-... 

It is well known from diffusion theory that different types of polymers have different diffusion behaviours. For example, the polyester type polymers like poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN) and polycarbonate (PC) as well as rigid poly(vinyl chloride) (PVC), which have a high glass transition temperature, are low diffusive polymers. The migration of potential contaminants in these polymers will result in low migration values. In contrast, polyolefins like high density polyethylene (HDPE), polypropylene (PP) or low density polyethylene (LDPE), which... 

Figure 13.3 Comparison of the PA-IR and FT-IR spectra recorded for (a) Poly(ethylene naphthalate) in the high-frequency range with an InSb FPA (b) Polystyrene recorded in the fingerprint region with an MCT FPAs. Panels (a) and (b) adapted from Refs [6] and [7], respectively.

The manufacture of poly(ethylene naphthalate) (PEN) is carried out using dimethyl 2,6-naphdialene dicarboxylate (NDC) and EG and is similar to die manufacture of PET from DMT. The IV after the melt is typically in the range of 0.5... 

POLY(ETHYLENE NAPHTHALATE), COPOLYMERS AND ESTERS 10.4 COSMETIC AND PHARMACEUTICAL CONTAINERS... 

ORIENTED POLY(ETHYLENE NAPHTHALATE) FILMS 4.9 MEDICAL USES... 

It should be taken into account that all of the aspects described above are of a general nature and therefore more or less valid for any kind of industrially relevant polyester resin. Upon closer examination, the experiences gained with PET are particularly applicable to poly(butylene terephthalate) (PBT), poly(trimethylene terephtlialate) (PTT) and poly(ethylene naphthalate) (PEN). These polymers have gained major industrial importance as a result of a number of different properties in comparison with PET. 

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