Napredni polimerni materiali na osnovi bio-osnovanega benzoksazina in epoksida

Švigelj, Nina (author), Ručigaj, Aleš (mentor)

Materiali z učinkom oblikovnega spomina iz bio-vhodnih surovin, ki izkazujejo dobre mehanske in termične lastnosti, so vedno bolj aktualna tema raziskav. V magistrski nalogi sem sintetizirala bio-osnovan benzoksazin, ki je ključna komponenta v kombinaciji z epoksidno smolo. Benzoksazinski monomer sem okarakterizirala z infrardečo spektroskopijo s Fourierjevo transformacijo (FTIR), magnetno resonančno spektroskopijo (NMR) in diferenčno dinamičo kalorimetrijo (DSC). Z NMR in FTIR metodo sem potrdila nastanek benzoksazinskega obroča. Z namenom izboljšanja termičnih in mehanskih lastnosti benzoksazinskega monomera RS-BOX sem v drugem delu pripravila in zamrežila kopolimere benzoksazinskega monomera z rezorcinol diglicidil etrom v različnih razmerjih. S pomočjo DSC analize sem določila termične lastnosti zamreževanja in okarakterizirala dva prisotna eksotermna vrhova. Prvi eksotermni vrh predstavlja kopolimerizacijo benzoksazinskega monomera in epoksidne smole, drugi vrh pa homopolimerizacijo preostanka epoksida. Entalpija narašča z višjim deležem epoksidne smole v kopolimeru. Z dinamično mehansko analizo sem potrdila temperaturo steklastega prehoda za benzoksazinski monomer, ki je pri 81,7 °C. Kopolimeri RS-BOX : RS EP so izkazovali Tg v območju med 60 °C in 80 °C. Nižji kot je delež benzoksazina v kopolimeru, nižji je Tg. Z večjo vsebnostjo epoksida v kopolimeru je elastični modul narastel. Učinek oblikovnega spomina je bil potrjen s pomočjo upogibnega testa pri razmerjih 33 : 67, 50 : 50 in 67 : 33. Razmerje obnovljene oblike Rr v preliminarnih testih je pokazalo, da se vsi vzorci povrnejo v osnovno stanje, vendar potrebujejo več časa za končno relaksacijo. Rf se giblje med 95 % in 99 %. Večji delež epoksida v kopolimeru predstavlja večjo rigidnost, večji del benzoksazina pa premajhno strukturno trdnost za ohranjanje oblike. Najbolj obetavne rezultate je pokazalo razmerje RS-BOX : RS-EP v molskem razmerju 50 : 50, zaradi najboljše homogenosti vzorca in mehanskih lastnosti v praksi. Ciklične obremenitve razmerja 50 : 50 pri kotu obremenitve 120° so pokazale dobro razmerje zadržane oblike, ki je med 98 % in 99 %. Razmerje obnovljene oblike se skozi vsak cikel podaljšuje, kar nakazuje na rahlo izgubljanje svoje funkcije pametnega materiala. V praksi čisti benzoksazinski monomer in kopolimer RS-BOX : RS-EP še izkazujejo preveliko krhkost, kar je lahko izhodišče za nadaljnje raziskave in izboljšave.

• Language: Slovenian
• Keywords: benzoksazini, epoksidne smole, pametni materiali, oblikovni spomin, kopolimeri.
• 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-121776
• COBISS.SI-ID: 39767299
• Publication date in RUL: 28.10.2020

Secondary language

• Language: English
• Title: Advanced polymer materials on bio-based benzoxazine and epoxy

Abstract

Materials with shape memory effect from bio-based raw materials, which exhibit good mechanical and thermal properties, are now often topic of research. First part is synthesis of bio-based benzoxazine which is a key component in combination with epoxy resin. Benzoxazine monomer is characterized with Fourier transform infrared spectroscopy (FTIR), magnetic resonance spectroscopy (NMR) and differential dynamic calorimetry (DSC). NMR method confirmed the presence of benzoxazine ring. In order to improve the thermal mechanical properties of the benzoxazine monomer, copolymer with resorcinol diglicidil ether was prepared in different ratios. Using DSC analysis, thermal properties of copolymer crosslinking were determined. First exothermic peak represents copolymerization of benzoxazine monomer and epoxy resin. The second peak represents homopolymerization of residual resorcinol diglicidil ether. Entalphy increases with a higher percentage of epoxy resin in the copolymer. Dynamic mechanical analysis (DMA) confirmed temperature of glass transition (Tg) for benzoxazine monomer at 81,7 °C. RS-BOX : RS-EP copolymers exhibit Tg in range between 60 °C and 80 °C. The lower the proportion of benzoxazine in the copolymer, the lower the Tg. With a higher epoxide content in the copolymer, the elastic modulus increases. The effect of shape memory was confirmed in preliminary tests by a bending test at ratios of 33 : 67, 50 : 50, and 67 : 33. Shape recovery ratio Rr showed that all samples returned to its original shape but needed more relaxation time. The shape fixity ratio Rf ranges between 95 % and 99 %. The higher ratio of epoxide in the copolymer represents higher rigidity. The higher higher ratio of benzoxazine also shows insufficient structural strength to maintain the shape. The most promising results were shown by RS-BOX : RS-EP molar ratio 50 : 50 due to the best Rr, sample homogeneity and mechanical properties in practice. Cyclic load of 50 : 50 ratio at a load angle of 120° showed a good shape fixity ratio between 98 % and 99 %. The shape recovery ratio of restored sample over each cycle indicated a slight loss of its shape memory function. For practical purposes benzoxazine monomer and copolymer RS-BOX : RS-EP still show excessive fragility, which may be a starting point for further research and improvements.

• Keywords: Benzoxazines, epoxy resins, smart materials, shape memory, copolymers.