Utjecaj limunske kiseline na svojstva TPS/PLA mješavina

master's thesis

• Title (english): The influence of citric acid on the properties of TPS/PLA blends
• Author: Mark Ružić
• Mentor: Vesna Ocelić Bulatović (mentor)
• Committee member: Vesna Ocelić Bulatović (predsjednik povjerenstva)
• Committee member: Mirela Leskovac (član povjerenstva)
• Committee member: Iva Movre Šapić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2023-07-11, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering

Abstract

U težnji za smanjenjem akumulacije sintetske plastike u okolišu, sve se više istražuju i razvijaju novi materijali koji će, nakon što završe u okolišu, biti potpuno razgradljivi. Stoga su u ovom radu pripremljene biorazgradive mješavine termoplastičnog škroba (TPS) i polilaktida (PLA). TPS/PLA polimerne mješavine različitog sastava pojedine komponente, bez i s dodatkom limunske kiseline (LK) pripremljene su umješavanjem u Brabender miješalici.
TPS je priređen plastifikacijom krumpirovog škroba s udjelom od 40 mas. % glicerola u jednopužnom ekstruderu. Udio limunske kiseline bio je 5 i 10 mas. %. Istražen je utjecaj limunske kiseline na toplinska, mehanička, barijerna svojstva kao i uvid u morfološku strukturu TPS/PLA polimernih mješavina. Struktura polimera i mješavina, te esterifikacija limunskom kiselinom potvrđena je kombiniranom tehnikom infracrvene spektroskopije s Fourierovim transformacijama i prigušene totalne refleksije, FTIR-ATR spektroskopijom.
Uvid u morfološku strukturu istražen je primjenom elektronske pretražne mikorskopije (SEM), toplinska svojstva i stupanj kristalnosti TPS/PLA mješavina primjenom diferencijalne pretražne kalorimetrije (DSC) i toplinska stabilnost termogravimetrijskom analizom (TGA) te kao pokazatelj barijernih svojstava ispitana je apsorpcija vode. Mehanička svojstva mješavina određena su rasteznim ispitivanjem. Na SEM mikrografijama TPS/PLA mješavina vidljiva je slaba adhezija između TPS i PLA, dok dodatkom limunske kiseline dolazi do poboljšanja adhezije što utječe na bolju homogenosti, odnosno međusobnu mješljivost TPS/PLA mješavina. DSC analizom potvrđeno je djelovanje limunske kiseline kao mogućeg kompatibilizatora. Također, veći udio TPS-a u TPS/PLA mješavinama utječe na povećanje stupnja kristalnosti PLA. Dodatkom limunske kiseline od 5 mas. % u TPS/PLA mješavine, vidljivo je poboljšanje mehaničkih svojstava, te smanjenje vrijednosti apsorpcije vode.
Na osnovu svih provedenih ispitivanja, TPS/PLA 50/50 polimerna mješavina s 5 mas.% limunske kiseline izdvojila se kao dobar kandidat za daljnja istraživanja kao obećavajući materijal.

Abstract (english)

In an effort to reduce the accumulation of synthetic plastics in the environment, new materials are increasingly being researched and developed that, once they end up in the environment, will be completely degradable. Therefore, biodegradable mixtures of thermoplastic starch (TPS) and polylactide (PLA) were prepared in this work. TPS/PLA polymer mixtures with different compositions of individual components, without and with the addition of citric acid (LK) were prepared by mixing in a Brabender mixer. TPS was prepared by plasticizing potato starch with a proportion of 40 wt. % of glycerol in a single-screw extruder. The proportion of citric acid was 5 and 10 wt. %. The influence of citric acid on thermal, mechanical, and barrier properties was investigated, as well as an insight into the morphological structure of TPS/PLA polymer mixtures. The structure of polymers and mixtures, as well as esterification with citric acid, was confirmed by the combined technique of infrared spectroscopy with Fourier transforms and attenuated total reflection, FTIR-ATR spectroscopy. Insight into the morphological structure was investigated using scanning electron microscopy (SEM), thermal properties and degree of crystallinity of the TPS/PLA mixture using differential scanning calorimetry (DSC) and thermal stability using thermogravimetric analysis (TGA), and water absorption was tested as an indicator of barrier properties. The mechanical properties of the mixtures were determined by tensile testing. On the SEM micrographs of the TPS/PLA mixture, weak adhesion between TPS and PLA is visible, while the addition of citric acid improves the adhesion, which affects the better homogeneity, that is, the mutual miscibility of the TPS/PLA mixture. DSC analysis confirmed the action of citric acid as well as a possible compatibilizer. Also, the greater part of TPS in TPS/PLA blends affects the increase in the degree of crystallinity of PLA. With the addition of citric acid of 5 wt. % in the TPS/PLA blends, an improvement in mechanical properties and a decrease in the water absorption value are visible. Based on all the conducted tests, the TPS/PLA 50/50 polymer blend with
5 wt.% citric acid stood out as a good candidate for further research as a promising material.

• Keywords: krumpirov škrob; termoplastični škrob; polilaktid; biorazgradivi materijali
• Keywords (english): potato starch; thermoplastic starch; polylactide; biodegradable materials
• Language: croatian
• URN:NBN: urn:nbn:hr:149:984114
• Study programme: Title: Materials Science and Engineering - Graduate study; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka kemijskog inženjerstva (magistar/magistra inženjer/inženjerka kemijskog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access; Embargo expiration date: 2023-09-30
• Created on: 2023-07-27 09:15:36