Vpliv mikro in nanoceluloze na lastnosti kompozitov iz nenasičene poliestrske smole

Velkovrh, Matjaž (author), Šebenik, Urška (mentor)

Poliestri in poliestrske smole se uporabljajo na številnih področjih, zato je vsako izboljšanje lastnosti le-teh lahko izjemnega pomena. Nenasičene poliestrske smole so ene izmed poliestrskih smol, za katere je značilna prisotnost dvojnih vezi. Te delujejo kot mesta, ki omogočajo polimerizacijo in zamreževanje, saj lahko ob prisotnosti iniciatorjev (termični, redoks, fotoiniciatorji) razpadejo na radikale. Nano in mikroceluloza sta dve vrsti delcev, katere je moč dodati v polimerno matrico ter s tem tvoriti kompozit z boljšimi lastnostmi od matrice. Predvsem s pomočjo kristalinične celuloze, je moč zvišati togost ter posledično Young-ov modul kompozita. Kako pa dodatek celuloze vpliva na same lastnosti kompozita, je potrebno ustrezno ovrednotiti. To je moč storiti z analiznimi tehnikami, kot so tri-točkovni upogibni test ter DSC in DMA analiza. S pomočjo prve sem določil Young-ov modul kompozitov. Temperaturo steklastega prehoda sem določil tako z DSC kot DMA, medtem ko sem stopnjo zamreženja poliestra določil s pomočjo DSC analize. V moji magistrski nalogi sem določeval vpliv dodane celuloze na omenjene lastnosti kompozita. Polimerna matrica, katero sem uporabljal, je bila Colpoly 7201. To je nenasičena poliestrska smola, raztopljena v 40 % stirena. V osnovno matrico sem dodajal kristalinično nano in mikrocelulozo ter fibrilno nanocelulozo. S tri-točkovnim upogibnim testom sem pokazal, da kristalinični celulozi zvišata Young-ov modul kompozita, pri čemer mikroceluloza Young-ov modul zviša bolj od nanoceluloze. Za razliko od kristalinične celuloze, pa je ob dodatku fibrilne nanoceluloze, Young-ov modul približno enak ali pa manjši, kot pred samim dodatkom. Ključna parametra, ki vplivata na zvišanje Young-ovega modula, sta stopnja zamreženja poliestra in Young-ovi moduli posameznih celuloz. Tako višja stopnja zamreženja, kot tudi višji Young-ov modul celuloze, vodi do višjega Young-ovega modula kompozita. Temperatura steklastega prehoda je prav tako odvisna od stopnje zamreženja poliestra, pri čemer prav tako velja, da zvišanje stopnje zamreženja, vodi do višje temperature steklastega prehoda. Poleg stopnje zamreženja, na Tg vpliva tudi količina povezav, ki se tvorijo pri interakcijah na fazni površini med celulozo in poliestrsko smolo. Te interakcije so šibkejše kot vezi, ki nastanejo pri zamreževanju poliestrske smole, zaradi česar se ob dodatku celuloze Tg kompozita zmanjša. Poleg steklastega prehoda in zamreževanja poliestra, se je pri DSC analizi pokazalo tudi območje razpada celuloze, in sicer v temperaturnem območju med 230 °C in 300 °C.

• Language: Slovenian
• Keywords: kompoziti, celuloza, Young-ov modul, steklasti prehod, zamreževanje
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2020
• PID: 20.500.12556/RUL-114115
• COBISS.SI-ID: 1538539203
• Publication date in RUL: 17.02.2020

Secondary language

• Language: English
• Title: Effect of micro and nanocellulose on properties of unsaturated polyester resin composites

Abstract

Polyesters and polyester resins are used in many areas, which means that every improvement of their properties could be crucial. Unsaturated polyester resins are a group of polyester resins, which main property is presence of double bonds. Those are sites of polymerization and cross-linking, because radicals could be formed in the presence of initiators (thermal, redox and photoinitiators). Nano and microcellulose are materials, which could be added to polymer matrices, which lead to better properties of those. Crystalline cellulose could raise Young modulus and rigidity of composite. Improvement of composites properties should be evaluated by techiques such as three point bending test, DSC and DMA analysis. Three point bending test was used to determine Young modulus of composites. Glass transition temperature was determined by DSC and DMA techiques. Besides the glass transition temperature, DSC was also used to determine a degree of cross-linking of the polyester resin. Effect of different types of cellulose on properties of composites was examined. Colpoly 7201, which was used polymer matrix, is an unsaturated polyester resin, which is dissolved in 40 % of styrene. Crystalline nano and microcellulose and fibril nanocellulose were added to the matrix. Three point bending test proved that Young modulus increase with addition of crystalline microcellulose. On the other hand fibril nanocellulose led to Young modulus which were lower or same as Young modulus of the polymer matrix. Degree of cross-linking of polyester and Young modulus of celluloses were main parameters that effected the Young modulus of composites. Increase of both parameters led to larger Young modulus. Temperature of glass transition was also effected by degree of cross-linking. Higher degree of cross-linking, also led to higher temperatures of glass transition. Links, which are caused by interactions on phase boundary between cellulose and polyester resins, also had effect on Tg. These interactions are weaker than bonds which are formed during cross-linking of polyester. That is the reason why addition of cellulose led to lower Tg. Besides the temperatures of glass transition and cross-linking, temperature of cellulose degradation was also determined. Temperature range of cellulose degradation was determined to be between 230 °C and 300 °C.

• Keywords: composites, cellulose, Young modulus, glass transition, cross-linking