| Abstract | Poliester čini gotovo 80 % ukupne proizvodnje sintetskih vlakana, od kojih je najzastupljeniji poli(etilen-tereftalat), PET. U medicini i zdravstvu se primjenjuju i vlakna i materijali iz PET-a u područjima gdje su mehanička svojstva, bioinertnost i trajnost od ključne važnosti. U ovom radu istraživanje je obuhvatilo razvoj bio-inoviranih poliesterskih materijala za ciljanu primjenu u bolničkom okružju kroz 3 faze, a odabrane metode primijenjene su s ciljem analize postavljenih parametara učinkovitosti. Prva faza je aktivacija površine poliesterske tkanine (standardna i PET) hidrolizom s naglaskom na održivost procesa. U tu svrhu istražena je alkalna hidroliza pri sniženoj temperaturi uz dodatak akceleratora te hidroliza ekološki prihvatljivim enzimima. Rezultati istraživanja potvrdili su postavljenu hipotezu da se proces hidrolize poliesterskih vlakana u tkanini može provesti upotrebom ekološki povoljnijih sredstava i/ili na energetski i ekonomski povoljniji način alkalnom hidrolizom uz dodatak heksadeciltrimetilamonijeva klorida (2 g/l HDTMAC, 80 °C, 10 min) te enzimskom hidrolizom amanolipazama Amano Lipase A iz Aspergillus niger (ALA) i Amano Lipase iz Pseudomonas fluorescens (ALAK) - vrijednost pH 9, koncentracija enzima 0,2 g/l, 60 °C, 60 min. Hidrolizom dolazi do povećanja hidrofilnosti što je potvrđeno analizom sorpcijskih svojstava. Za razliku od alkalne hidrolize, enzimskom hidrolizom ostaju zadržana primarna svojstva tkanine. Druga faza obuhvaća pripremu kitozana te implementaciju na površinu aktivirane tkanine. S obzirom na prikazane rezultate, kao i na postojanost obrade nakon prvog ciklusa pranja u neionskom tenzidu, funkcionalizacija kitozanom postupkom impregnacija-sušenje-kondenzacija homogeniziranom otopinom kitozana u octenoj kiselini pokazala se povoljnijom u odnosu na termosol postupak dispergiranim submikronskim česticama kitozana. Za pretpostaviti je da su kod funkcionalizacije termosol postupkom prisutne samo vodikove veze, dok su kod postupka impregnacija-sušenje-kondenzacija prisutne i ionske veze jer je kitozan protoniran. Rezultati ciljanih istraživanja potvrdili su postavljenu hipotezu da se poliesterska tkanina može funkcionalizirati kitozanom, a postupak impregnacija-sušenje-kondenzacija homogeniziranom otopinom kitozana u octenoj kiselini je postojana i nakon višestrukih ciklusa pranja. To je potvrđeno SEM i elektrokinetičkom analizom, bojadisanjem, poboljšanjem sorpcijskih svojstava i analizom antimikrobne učinkovitosti. U trećoj fazi ispitana je antimikrobna učinkovitost funkcionaliziranih tkanina nakon 10 ciklusa prilagođenog industrijskog pranja kako bi se utvrdila postojanost obrade. Tkanina zadržava dobivena svojstva do 3 ciklusa pranja, a antimikrobnu učinkovitost i nakon 10 pranja te se kao takva može primijeniti u bolničkom okružju kao zamjena za jednokratnu zaštitnu odjeću. Enzimski hidrolizirana PET tkanina funkcionalizirana kitozanom ima veću učinkovitost u odnosu na alkalno hidroliziranu PET tkaninu funkcionaliziranu kitozanom budući da pokazuje učinkovitost i na mikrogljivice, a funkcionalizacija je postojana i nakon višestrukih ciklusa pranja. Enzimski hidrolizirana PET tkanina enzimom ALAK funkcionalizirana kitozanom pokazuje antimikrobni učinak na sva tri mikroorganizma čak i nakon 10 ciklusa pranja. Valja istaknuti da osim antimikrobnoj učinkovitosti enzimska hidroliza i funkcionalizacija kitozanom doprinose udobnosti tkanine jer se povećavaju hidrofilnost, upravljanje kapljevitom vlagom, osjet glatkoće i osjet mekoće. S obzirom na sve dobivene rezultate i analizu parametara učinkovitosti za ciljanu primjenu u bolničkom okružju, najprihvatljivijim se pokazao bio-inovirani postupak aktivacije površine PET tkanina enzimskom hidrolizom amanolipazom iz Pseudomonas fluorescens (ALAK) funkcionaliziran homogeniziranim kitozanom postupkom impregnacija-sušenje-kondenzacija. |
| Abstract (english) | Polyester accounts for almost 80 % of the total production of synthetic fibers, of which poly(ethylene terephthalate), PET, is the most common. In medicine and healthcare, PET fibers and materials are also used in areas where mechanical properties, bioinertness and durability are crucial. In this doctoral thesis, the development of bio-innovated polyester materials aimed for use in a hospital environment was investigated in three phases. The first phase is the activation of the surface of polyester fabrics (standard and PET) by sustainable hydrolysis process. For this purpose, alkaline hydrolysis at reduced temperature with the addition of an accelerator and hydrolysis with environmentally friendly enzymes were performed. The effect of temperature on the alkaline hydrolysis of PET was analysed with and without the addition of an accelerator (cationic surfactant hexadecyltrimethylammonium chloride, HDTMAC) in terms of the change in mass and in breaking force and the morphology of the fibers. The kinetics of PET degradation and the activation energy were determined according to the theoretical model. It was found that it is possible to carry out PET hydrolysis in a more environmentally friendly way compared to conventional alkaline hydrolysis (100 °C, 60 min). Alkaline hydrolysis with the addition of 2 g/l HDTMAC at 80 °C for 10 min results in the same changes. Although this process is still not completely environmentally friendly due to the use of sodium hydroxide, it is economically and energetically more acceptable and therefore more sustainable compared to the conventional process. Enzymatic hydrolysis, which is more environmentally friendly than alkaline hydrolysis, was performed using different hydrolases, esterase and lipase. Amano Lipases proved to be efficient and it is possible to carry out PET hydrolysis in more environmentally, economically and energetically favourable process. The effectiveness of the Amano Lipase A from Aspergillus niger (ALA) in an alkaline medium has been confirmed. An enzyme concentration of 0.1 g/l is sufficient, and hydrolysis can also be carried out at a reduced temperature of 60 °C, although hydrolysis at 100 °C is more effective. The Amano Lipase from Pseudomonas fluorescens (ALAK) is effective in both acidic and alkaline media. In an acidic medium, it achieves the best results at a concentration of 0.2 g/l and a temperature of 100 °C. In an alkaline medium, satisfactory results can be achieved with a lower concentration of 0.1 g/l at a lower temperature and time. The analysis of the results in terms of sustainability of the hydrolysis process showed that the optimal process parameters for hydrolysis using the enzyme ALA are: pH value 9, enzyme concentration 0.1 g/l, 60 °C, 60 min; and for the enzyme ALAK: pH value 9, enzyme concentration 0.2 g/l, 60 °C, 60 min. In view of the easier comparability of all the results obtained and the small differences in the preliminary results, the enzyme concentration of 0.2 g/l was also used for the ALA enzyme, which was very effective. From this it can be concluded that the hydrolysis of the surface of commercially available polyester fabrics can be carried out in an ecologically, energetically and economically process, when the process parameters are carefully selected. Hydrolysis leads to an increase in hydrophilicity, which was confirmed by analysing the sorption properties. In contrast to alkaline hydrolysis, enzymatic hydrolysis preserves the primary properties of the fabric. This confirms hypothesis 1. HYPOTHESIS 1: The process of hydrolysis of polyester fibers in the fabric can be carried out by more environmentally friendly process and/or in a more energetically and economically favourable process. The second phase includes the preparation of chitosan and its implementation on the activated surface of the fabric. The implementation of chitosan was carried out by the thermosol process from dispersion of submicron particles of chitosan and by the pad-dry-cure process of chitosan homogenized in acetic acid solution. Considering the results presented and the durability of the functionalization treatment after the first washing cycle in a non-ionic surfactant, functionalization with chitosan using the pad-dry-cure method of chitosan homogenized in acetic acid solution proved to be more favourable than the thermosol process with dispersion of submicron chitosan particles. It is to assume that in thermosol process only H-bonds are present, while in pad-dry-cure process ionic bond occurs between protonated chitosan and PET fiber. The pad-dry-cure process of chitosan homogenized in acetic acid solution is durable after one washing cycle. This confirms hypothesis 2. HYPOTHESIS 2: Polyester fabric can be functionalized with chitosan. In the third phase, the antimicrobial efficacy of the functionalized fabrics was tested after 10 cycles of adapted industrial washing process for determination of the treatment durability. The morphological characterization of the surface (SEM), electrokinetic analysis, dyeing, improvement of sorption properties and analysis of antimicrobial efficacy were performed. Literary sources state that chitosan has antimicrobial effectiveness. Given that chitosan is a natural biopolymer that has not been proven to have a negative impact on humans or the environment, it is considered a favourable antimicrobial agent. The results show that alkaline hydrolysis leads to the migration of an antimicrobial agent (quaternary ammonium compounds, QAC) from the surface of the material, which can have a negative effect on the natural bacterial flora of the skin. In contrast, enzymatic hydrolysed PET fabrics functionalized with chitosan have no inhibition zone, have a higher efficacy than alkaline hydrolysed samples as they also act on fungi and are stable even after several washing cycles. The enzymatically hydrolysed PET fabric with ALAK enzyme functionalized with chitosan shows an antimicrobial effect on all three microorganisms tested even after 10 washing cycles, thus fulfilling the basic requirements for a good antimicrobial agent for textile substrates and the requirements for an ideal antimicrobial treatment. It should be noted that enzymatic hydrolysis and functionalization with chitosan, in addition to antimicrobial efficacy, also contribute to the comfort of the fabric by increasing its hydrophilicity, moisture management and the feeling of smoothness and softness. The fabric retains its properties up to 3 washing cycles and its antimicrobial efficacy even after 10 cycles and can therefore be used in hospitals as a replacement for disposable protective clothing. Considering this purpose, hypothesis 3 can be considered confirmed. HYPOTHESIS 3: Polyester fabric functionalized with chitosan is resistant to the washing process. Taking into account all the results obtained and analysing the efficiency parameters aimed for use in the hospital environment, the bio-innovative process for activating the surface of PET fabrics by enzymatic hydrolysis with Amano Lipase from Pseudomonas fluorescens (ALAK) functionalized with homogenized chitosan by pad-dry-cure process proved to be the most acceptable. |
