Fast crystallization of poly(ethylene terephthalate)

Abstract

The crystallization of poly(ethylene terephthalate) (PET) was studied in the presence of nucleating agents and promoters. The effect of both by themselves and in concert was investigated using differential scanning calorimetry. The aim of this work is to find conditions of fast crystallization of PET. Sodium benzoate(SB) and Surlyn | (S) substantially increase the crystallization rate of PET at higher temperature owing to a reduction in the energy barrier towards primary nucleation, but they accelerate crystallization even more at lower temperature with an additional improvement of the molecular mobility of PET chains. Chain seission of PET caused by the reaction with the nucleating agents was proven by determination of molecular weight. The addition of S alone led to a lower reduction in molecular weight. A series of N-alkyl-p-toluenesulfonamides (ATSAs) were shown to effectively promote molecular motion of the PET chains, leading to an increase in crsytallization rate at lower temperature. A remarkable acceleration of crystallization of PET was attained at lower temperature when S and ATSA were added together. When the content of ATSA is low, S has the dominant influence due to its dual effect of decreasing energy barrier towards nucleation and promoting molecular motion of PET chains. A further increase of crystallization rate of PET was found only after an addition of ATSA of above 5 wt.%.

Nucleation mechanism of polyhydroxybutyrate and poly(hydroxybutyrate‐co‐hydroxyhexanoate) crystallized by orotic acid as a nucleating agent

“…In that case, the nucleating agent added to the polymer does not act as an inert heterogeneous substrate, but is dissolved in the polymer melt. For these cases, it has been shown by IR analysis 17,18 that molten polymer chains reacted with the nucleant, inducing the random chain scission of polymers and the creation of new ionic chain ends. These ionic species will then form some organized ionic aggregates which will become the true nucleating species.…”

Crystallization and melting behavior of liquid crystalline copolyesters based on poly(ethylene terephthalate)

“…Fast crystallization of polymers with slow crystallization rates, such as PET, is usually achieved by adding nucleating agents and nucleating promoters. 20,21 However, some arylate-unit-containing PET copolymers have been found recently to show a higher crystallizability than PET homopolymer, and a mechanism of accelerated nucleation was proposed for the improvement of crystallization properties. 22,23 In the present work, we have used hydroquinone/ terephthalic acid (HQ/TA) to partially replace HBA and explored compositions and thermal transition behaviors of the resulting copolyesters by means of differential scanning calorimetry (DSC), NMR spectroscopy, polarized light microscopy (PLM) and wide angle X-ray diffraction (WAXD).…”

Injection moulding of long glass fibre reinforced poly(ethylene terephtalate): Influence of carbon black and nucleating agents on impact properties

“…Besides, nucleating agents (e.g. most commonly carboxylate or phosphate ester salts, and sorbitol acetals) are often added to semi-crystalline polymers such as PET [24][25][26][27] or PP [28,29] in order to modify the crystallisation kinetics and mechanism (increase of the crystallisation rate, leading to a faster polymer solidification), consequently leading to injection moulding cycle time reduction. In particular, PET is characterised by a very slow crystallisation and nucleating agents are often added to control a more homogeneous structure through a uniform spherulite size more than to increase the degree of crystallinity of the polymer.…”

“…The sodium salts usually used as nucleating agent do not act as nucleation centres themselves but interact with the PET molecules to give sodium terephtalate chains that are the effective nucleating species. These nucle-ophilic substitution chemical reactions induce a global molecular weight decrease of the polymer [24][25][26]. Sodium benzoate nucleating agent is wellknown to substantially increase the crystallization rate of poly(ethylene terephtalate) at higher temperature and to accelerate crystallization even more at lower temperature with an additional improvement of molecular mobility of PET chains, but the increase of crystallization rate is limited by the fact that sodium benzoate may be only partially soluble in PET matrix [26,27].…”

“…These nucle-ophilic substitution chemical reactions induce a global molecular weight decrease of the polymer [24][25][26]. Sodium benzoate nucleating agent is wellknown to substantially increase the crystallization rate of poly(ethylene terephtalate) at higher temperature and to accelerate crystallization even more at lower temperature with an additional improvement of molecular mobility of PET chains, but the increase of crystallization rate is limited by the fact that sodium benzoate may be only partially soluble in PET matrix [26,27]. The sodium 2,2!-methtylenebis(4,6-di-tert-butylphenyl)phosphate nucleating agent is usually used to increase the crystallization rate of polyolefins, polyamides and PET; it may induce smaller spherulites than sodium benzoate at higher crystallization temperature with shorter crystallization half time [28,29].…”