Določanje klorida v razgrajenem PVC

Velkov, Katarina (author), Strlič, Matija (mentor)

PVC je tretja najbolj uporabljana vrsta plastike na svetu, katere uporabnost se je razširila tudi v svet umetnosti in oblikovanja. Pomembno je preučevanje stabilnosti in kvalitete izdelkov iz PVC, za namene ohranjanja zdravja ljudi, kot tudi za čim boljše ohranjanje lastnosti umetniških del skozi čas. PVC je podvržen procesu dehidroklorinacije oziroma eliminaciji HCl. Pri tem na polimerni verigi nastajajo konjugirane dvojne vezi, ni pa popolnoma jasno, ali nastali klorid ostane v polimernem mediju ali odhlapi kot HCl. Izdelki, pri katerih razgrajevalni proces dehidroklorinacije pospešeno poteka, porumenijo, v primerih intenzivne razgrajenosti pa postanejo rjavi, tudi črni. PVC je termično slabo obstojen, saj dehidroklorinacija pospešeno poteka pri povišani temperaturi. Zato je med proizvodnjo PVC potrebno dodajati ustrezne stabilizatorje, navadno kalcijeve, barijeve, cinkove stearate ali karboksilate. V eksperimentalnem delu diplomske naloge sem določala vsebnosti prostega klorida v vzorcih naravno razgrajenega PVC. Metoda za določanje klorida je postavljena na osnovi ionske kromatografije, ki za analizo zahteva vodne raztopine klorida. Pri PVC je ekstrakcija klorida otežena, saj ni topen vodi. Zato sem razvila postopek za pripravo fino zmletih vzorcev PVC in iskala ustrezne pogoje za postopke ekstrakcije prostega klorida iz polimernega medija v vodne raztopine in tudi v organsko topilo aceton. Namen diplomske naloge je bilo pokazati, da bolj razgrajen vzorec PVC vsebuje večjo količino prostega klorida od manj razgrajenega.

• Language: Slovenian
• Keywords: PVC, dehidroklorinacija, klorid, ekstrakcija, ionska kromatografija
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2021
• PID: 20.500.12556/RUL-129868
• COBISS.SI-ID: 81743363
• Publication date in RUL: 09.09.2021

Secondary language

• Language: English
• Title: Determination of chloride in degraded PVC

Abstract

PVC is the third most used variety of plastics in the world. The application of PVC expanded also to the area of art and design. Research into stability and quality of products made from PVC is important mainly for maintaining human health but also for maintaining the properties and appearance of works of art. PVC is subject to dehydrochlorination or elimination of HCl. This results in formation of conjugated double bonds on the polymer chain. It’s not clear whether the formed chloride stays in the polymer medium or evaporates as HCl. Products which are subject to accelerated dehydrochlorination turn yellow over time or in cases of severe degradation turn brown or even black. PVC is prone to thermal degradation because the process of dehydrochlorination is accelerated at higher temperatures. That is why it’s necessary to add a stabiliser during the production of PVC. These kinds of stabilisers are predominantly calcium, barium, zinc stearates or carboxylates. In the experimental part of diploma thesis I’ve analysed the content of free chloride in samples of naturally degraded PVC. The method used for the analysis is based on ion chromatography which suggests a water based sample for the analysis to be successful. The extraction of chloride from PVC is problematic because PVC is not soluble in water. That is why I had to develop a procedure for preparation of finely ground samples of PVC and I searched for suitable conditions of extraction procedure of chloride from polymer into water solutions and also into acetone. The purpose of this diploma thesis was to show that a more degraded sample of PVC contains a larger quantity of chloride than a less degraded sample.

• Keywords: PVC, dehydrochlorination, chloride, extraction, ion chromatography