PET/PEN copolymers

Pentaerythritol tetranitrate (PETN) PET/PEN copolymers, 20 50-51 PET POY spun yarn, 20 14 PET/PTN blend bottles, 20 53 PET resins, 20 33 handling, 20 59-60 Petri, Julius Richard, 11 8 Petri dish, invention of, 11 8 Petrochemical feedstocks, 13 556-570, 674... 

The isomeric bibenzoic acids (BBs), would appear to share similar structural features with naphthalene dicarboxylic acid. Like the PET-naphthalate copolymers, PET-bibenzoates have been demonstrated to possess moduli and glass transitions temperatures which increase with increasing levels of rigid comonomer [37-39], Unlike the PET/PEN copolymers, when the symmetrical 4,4 - I f I f monomer is substituted into a PET backbone, virtually every composition of PET-BB is semicrystalline the 2,4- and 3,4- isomers of BB, when... 

Jenkins, S. D., PET/PEN copolymers and blends for hot-fill and high barrier packaging applications, presentation given at the Specialty Polyesters 95 Conference, Brussels, June 27-28, 1995, Schotland Business Research Inc., Skillman, NJ, 1995. 

Mechanical studies have also been performed on another non-LCP system -copolyesters of PET and PEN, where both copolymer units having flexible chain segments and lack a liquid-crystalline behaviour (Santa Cruz et al, 1992). The whole range of PET/PEN copolymers can therefore be prepared in the amorphous state. 

Samples of PET/PEN copolymers with 10, 20, 30, 50, 80 and 100 mol% PEN have been synthesized. Amorphous films of the samples were obtained by melt pressing above the melting point and quenching in ice-water. The samples were then crystallized by annealing the glassy materials at various temperatures. The degree of crystallinity was calculated from the amorphous density measured on quenched samples and from the crystal density derived from the crystal unit cell. 

Finally we mention that draw-induced mesophases have also been observed in some other semi-rigid chain polymers. Examples of such studies are cold drawing of glassy PEN [108,109] and oriented crystallization of PET/PEN copolymers [110, 111]. In all cases a smectic mesophase has been reported. In the absence of crystallization it can attain a degree of stability that resists decay from chain relaxation. This supports the view that the mesophase represents a thermodynamic state [101]. We expect that similar mesophases based on semi-rigid monomers can be observed in other polymers with intrinsic rigid building blocks, such as other aromatic polyesters and polyamides. 

Fig. 1. Melting point of PET/PEN copolymers and blends. Blend. Data from BP Amoco Chemcial Co.

The use of naphthalate-modified polyester resins in packaging applications offers improvement in gas barrier, UV barrier, thermal, and mechanical properties versus PET alone. Naphthalate resins suitable for packaging applications are commercially available in either homopolymer (PEN), PET/PEN copolymers (PETN-x), or PET/PEN blends. 

Packaging Applications Using Low PEN Level PET/PEN Copolymers. PETN-x low level copolymers, where x < 1% to typically 10% are used in rigid packaging applications where increased UV barrier resistance or small improvements in thermal performance versus PET are required. 

Figure 20.1 The chemical structures of the materials used in this study, i.e. the liquid crystal copolymer (PHB-PET), PEN and PET IV, intrinsic viscosity...

A great deal of attention on PET/PEN blends has been paid to elucidate the type of kinetics of the transesterification reaction, and, in particular, reversible second-order kinetics has been found in solution [64], On the other hand, the reaction kinetics is strongly affected by terminal hydroxyl groups when the reaction is carried out in a mixing chamber [65], In the same device, studies on the thermal, rheological, and mechanical properties for blends with 25, 50, and 75 wt% of PEN content have also been reported [66], By using a twin-screw extruder, a block copolymer may be obtained via melt extrusion when the PEN content is 20 wt% [67],... 

In many cases blends of PET with other polymers are only partially blends and partially copolymers, due to transesterification reactions, which take place during extrusion. This is the case, for example, for the PET/PEN blends which will be discussed in Section 4.9.3. 

The use of the microhardness technique in blends of condensation polymers [PET/PEN and PET/polycarbonate (PC)] evidences the formation of copolymer sequences within the blends (30). 

Within the range of approximately 10-90 mol% NDC, PET/PEN random copolymers (PETN) remain essentially amorphous. On the other hand, PET/PEN blends are capable of crystallizing and exhibiting a melting point at any TIN ratio, which depends not only on this ratio but also on the degree of randomness or... 

Fig. 3. Oxygen permeability of 4 x 4 biaxially oriented films from PET/PEN blends and copolymers (7). For O2 permeability values with the units, multiply by 2.

Fig. 11. Opportunities for PEN homopolymers, copolymers, and blends in rigid packaging. A PET, B Low PEN copolymer, C PEN blends, D PEN.

Structurally the difference between PEN and PET is in the double (naphthenic) ring of the former compared to the single (benzene) ring of the latter. This leads to a stiffer chain so that both and are higher for PEN than for PET (Tg is 124°C for PEN, 75°C for PET is 270-273°C for PEN and 256-265°C for PET). Although PEN crystallises at a slower rate than PET, crystallization is (as with PET) enhanced by biaxial orientation and the barrier properties are much superior to PET with up to a fivefold enhancement in some cases. (As with many crystalline polymers the maximum rate of crystallisation occurs at temperatures about midway between Tg and in the case of both PEN and PET). At the present time PEN is significantly more expensive than PET partly due to the economies of scale and partly due to the fact that the transesterification route used with PEN is inherently more expensive than the direct acid routes now used with PET. This has led to the availability of copolymers and of blends which have intermediate properties. 

This class of polyesters consists of four major commercial polymers and their copolymers, namely PET, PTT, PBT, and PEN (see Table 2.1). They compete for engineering thermoplastics, films, and fibers markets with other semicrystalline polymers, such as aliphatic polyamides, and for some other applications with amorphous engineering plastics such as polycarbonate. The syntheses of PET and PBT, detailed in numerous reviews and books,2-5 are described in Sections 23.2.2 and 2.3.2.1. 

Neither poly(ethylene 2,6-naphthoate) (PEN), nor copolymers of PEN and PET, are new materials, but they continue to receive considerable attention, due to their relatively high Tm and T values, and attractive tensile, flexural and gas-barrier... 

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