Improving oxygen barrier properties of poly(ethylene terephthalate) by incorporating isophthalate. I. Effect of orientation

Abstract

ABSTRACT:The present study examined poly(ethylene terephthalate) (PET) and a series of statistical and blocky copolymers in which up to 30% of the terephthalate was replaced with isophthalate by copolymerization and melt blending, respectively. Some level of transesterification during processing of melt blends resulted in blocky copolymers, as confirmed by NMR. Random and blocky copolymers exhibited similar properties in the glassy state, including a single glass transition, due to miscibility of the blocks. However, random copolymerization effectively retarded coldcrystallization from the glass whereas blocky copolymers readily cold-crystallized to a crystallinity level close to that of PET. The polymers were oriented at four temperatures in the vicinity of the T g and characterized by oxygen transport, wide-angle X-ray diffraction, positron annihilation lifetime spectroscopy, and infrared spectroscopy. Orientation of all the copolymers resulted in property changes consistent with strain-induced crystallization. However, blocky copolymers oriented more easily than random copolymers of the same composition and after orientation exhibited slightly lower oxygen permeability, higher density, and higher fraction trans conformers. Analysis of oxygen solubility based on free volume concepts led to a two-phase model from which the amount of crystallinity and the amorphous phase density were extracted. Dedensification of the amorphous phase correlated with the draw temperature

Effect of exfoliated graphite nanoplatelets’ size on the phase structure, electrical, and barrier properties of poly(trimethylene terephthalate)-based nanocomposites

“…Both EG50 and EG500 with a total concentration of nanoplatelets of 0.5 wt% do not cause crystallization of thin films. This is extremely important from the point of view of the barrier properties and electrical conductivity, where the influence of crystallinity on both gas permeability and the value of the conductivity and the formation of conduction paths has been confirmed. As may be seen in Fig.…”

“…Table summarizes the carbon dioxide and oxygen permeability of these PTT/EG films as a function of weight fraction of nanofiller type. The permeability strongly depends on the morphology of the nanocomposites but also on degree of crystallinity of the samples . For both series of nanocomposites a significant enhancement in impermeability to CO 2 and O 2 has been observed.…”

Oxygen permeability, electron spin resonance, differential scanning calorimetry and positron annihilation lifetime spectroscopy studies of uniaxially deformed linear low‐density polyethylene film

“…Conformational changes caused by sample deformation could be investigated by solid state NMR or FTIR. Such investigations performed by FTIR on deformed poly(ethylene terephthalate) have shown a higher fraction of trans conformers after orientation . The orientation and some aspects about the conformation of the chain segments in the amorphous regions of drawn polyethylene were also studied by infrared spectroscopy .…”

Amorphous copolyesters based on bibenzoic acids and neopentyl glycol

“…Early patents by Monsanto claimed copolyester compositions where PET was modified with 4,4′BB comonomer, however, very little property analysis was reported on these compositions. Over the years, both 3,4′BB and 4,4′BB were investigated for their potential to enhance gas barrier, and our recently reported work modified PET with 4,4′BB, 3,4′BB, and isophthalate moieties in an effort to improve its thermal, mechanical, and barrier properties . PET copolyesters containing 15 – 40 mol % 4,4′BB were amorphous with T g ’s ranging from 89 to 98 °C.…”