Monitoring of chlorobenzene impact on rapid aging of pet bottles by image analysis

Abstract

Poly(ethylene terephthalate) (PET) is a material widely used for various kinds of packaging, because of its superior barrier properties, low price and simple processing. Apart from aqueous products, it is being used as a packaging material for organic solvent based products, eg. for medicinal purposes, or for pesticides. In this work the influence of chlorobenzene on the properties of PET bottles was investigated. The bottles (50 ml) were filled with chlorobenzene and were subject to aging at 54 °C for 15 days. Afterwards, the bottles were characterized by a method of image analysis, using the Image-Pro Plus programme, where the dimension alterations were defined, together with the zones where the material was damaged. The change of mass of the bottles was also established. The results show that the bottles that were subject to chlorobenzene have acquired over 5% of the mass during the experiment, whilst the control samples - empty ones or the ones filled with water, showed no significant change in mass. The zones of the largest alteration of dimension were established, and it was concluded that these are present around the screw thread and at the peripheral zones of the bottom, i.e. where the highest strains are present. It has also been shown that the zone of increased crystallinity, that stems from the PET structure ordering as a result of solvent penetration, is present around points of irregular structure, and these points act as entry points for solvent penetration into the material as opposed to the absorption through the whole bottle surface.

Poli(etilen tereftalat) (PET) je materijal koji se koristi za izradu različitih vrsta ambalaže zbog svojih dobrih barijerinih svojstava, niske cene i jednostavne prerade. Osim proizvoda na bazi vode, PET je često materijal koji se koristi kao ambalaža za proizvode rastvorene u organskim rastvaračima, kao što su medicinski proizvodi ili pesticidi. U ovom radu ispitivanje uticaj hlorbenzena na bočice od PET-a (50 ml), tako što su bočice punjene hlorbenzenom i izlagane ubrzanom starenju na 54 °C tokom 15 dana. Bočice su potom karakterisane metodom analize slike, korišćenjem programa Image-Pro Plus pomoću koga je određena promena dimenzija boca tokom ovog eksperimenta i definisane zone oštećenja boce. Takođe je merenjem određena i promena mase bočica. Pokazalo se da pod dejstvom hlorbenzena dolazi do povećanja mase bočice od preko 5%, za razliku od kontrolnih uzoraka koji nisu punjeni ili su bili punjeni vodom kod kojih ne dolazi do porasta mase tokom eksperimenta. Definisane su i zone promene dimenzije boce, gde se vidi da su one najveće na delu boce gde se nalazi navoj za zapušač i u perifernim delovima dna boce gde su najveći zaostali naponi. Pokazalo se i da se oblast povećane kristaliničnosti koja je posledica uređivanja strukture PET-a pod dejstvom rastvarača koji je materijal apsorbovao javlja oko tačaka gde postoji nepravilnost strukture i da kroz ta mesta dolazi do penetracije hlorbenzena, a ne ravnomerno kroz celu strukturu materijala.