Priprava i svojstva hidrofobnih prevlaka na osnovi šelaka

master's thesis

• Title (english): Preparation and properties of shellac-based hydrophobic coatings
• Author: Lana Rončević
• Mentor: Mirela Leskovac (mentor)
• Committee member: Mirela Leskovac (predsjednik povjerenstva)
• Committee member: Emi Govorčin Bajsić (član povjerenstva)
• Committee member: Ljerka Kratofil Krehula (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2024-02-23, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering

Abstract

Šelak je prirodna, organska smola koju proizvode insekti koji obitavaju na stablima u Indiji i na Tajlandu. Smola koju oni izlučuju prolazi kroz razne faze pročišćavanja da bi se kao konačna sirovina dobio šelak, a ovisno o vrsti insekata, stablima i procesu pročišćavanja i obrade moguće je dobiti različite vrste šelaka, drugačijeg sastava, svojstava i boje. Primjenjuje se u raznim područjima kao što je u farmaciji, prehrambenoj industriji, zaštiti i premazu drvenih površina, kozmetici. Dodatak silana utjecao bi na poboljšanje svojstava šelaka. Cilj ovog rada bio je istražiti svojstva prevlaka mješavina šelaka (SCH) i dvaju silana
(3-glicidoksipropil-trimetoksisilan, GPTMS i 1,1,1,3,3,3-heksametildisilazan, HMDS) različitih udjela, pripremljenih iz otopine etanola, uz dodatak glicerola. Provedena su ispitivanja toplinskih svojstava primjenom diferencijalne pretražne kalorimetrije (DSC) i termogravimetrijske analize (TGA) i ispitivanja površinskih karakteristika mjerenjem kontaktnog kuta. Strukturna svojstva analizirana su pomoću FTIR-ATR spektroskopije,
a barijerna svojstva su određena mjerenjem propusnosti vodene pare te je ispitivana otpornost prevlaka na ljudski znoj. Utvrđeno je prema DSC analizi da dodatak silana povećava fleksibilnost prevlake i utječe na toplinsku stabilnost prevlaka prema TGA.
FTIR analiza ukazala je da nema značajnih razlika između prevlaka sa i bez silana. Kod prevlaka s ishodnim (krutim) šelakom, dodatkom silana propusnost vodene pare se povećala, odnosno kontaktni kut s vodom smanjio. Također, utvrđeno je da dodatkom silana topljivost prevlaka u otopini znoja raste te da silani nisu poboljšali tražena svojstva prevlaka.

Abstract (english)

Shellac is a natural, organic resin produced by insects that live on trees in India and on Thailand. The resin they secrete goes through various stages of purification to obtain shellac as the final raw material and depending on the type of insects, trees and the process of purification and processing, it is possible to obtain different types of shellac, with different composition, properties and color. It is used in various fields such as pharmacy, food industry, protection and coating of wooden surfaces, cosmetics. Addition of silane would improve the properties of shellac. The aim of this work was to investigate the coating properties of mixtures of shellac (SCH) and two silanes (3-glycidoxypropyl-trimethoxysilane, GPTMS and 1,1,1,3,3,3-hexamethyldisilazane, HMDS) of different proportions, prepared from an ethanol solution, with addition of glycerol. Thermal properties were tested using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and surface characteristics were tested by measuring the contact angle. The structural properties were analyzed using FTIR-ATR spectroscopy and the barrier properties were determined by measuring water vapor permeability and the coating's resistance to human sweat was tested. According to DSC analysis, it was determined that the addition of silane increases the flexibility of the coating and affects the thermal stability of the coating according to TGA. FTIR analysis showed that there are no significant differences between coatings with and without silanes. In the case of a coating with original (solid) shellac, the water vapor permeability increased with the addition of silane, that is, the contact angle with water decreased. Also, it was determined that with the addition of silane, the solubility of the coating in the sweat solution increases and that the silanes did not improve the required properties of the coating.

• Keywords: šelak; GPTMS; HMDS; DSC; TGA; FTIR-ATR; kontaktni kut; propusnost vodene pare; otpornost na znoj
• Keywords (english): shellac; GPTMS; HMDS; DSC; TGA; FTIR-ATR; contact angle; water vapor permeability; resistance to sweat
• Language: croatian
• URN:NBN: urn:nbn:hr:149:851776
• Study programme: Title: Chemical Engineering - Graduate study; Study programme type: university; Study level: graduate; Academic / professional title: sveučilišni/a magistar/magistra inženjer/inženjerka kemijskog inženjerstva (sveučilišni/a magistar/magistra inženjer/inženjerka kemijskog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2024-02-29 09:29:33