| Abstract | U radu su istraženi utjecaji polikaprolaktona (PCL) kao biorazgradljivog polimernog premaza
na kartonu u svrhu unapređenja svojstava ambalaže i tiska na recikliranom kartonu. Također,
istražene su modifikacije premaza dodavanjem nanočestica aluminijevog oksida (Al2O3),
silicijevog dioksida (SiO2) i cinkovog oksida (ZnO). Uzorci premaza pripremljeni su
otapanjem PCL-a u etil-acetatu, a umješavanje nanočestica provedeno je homogenizatorom.
Mjerna karta boja otisnuta je na GD2 kartonima različite gramature (230 g/m2, 280 g/m2, 350
g/m2). Kartoni su premazani ispitivanim PCL i PCL nanokompozitnim premazima u
različitim debljinama (4 μm, 24 μm, 40 μm, 80 μm). Odabir optimalne koncentracije i
debljine nanokompozitnih premaza definiran je analizom kolorimetrijskih rezultata mjerne
karte boja.
PCL premaz je nakon optimizacije modificiran dodavanjem Al2O3, SiO2 i ZnO nanočestica.
Karakterizirana su kolorimetrijska, adhezijska, barijerna, termička i mehanička svojstva kao i
degradacija premaza te svjetlostalnost otiska uzoraka kartona s PCL premazom. Uzorci su
također karakterizirani FTIR i UV-Vis spektroskopijom. Određeni su parametri adhezije kako
bi se istražila međusobna povezanost kartona i PCL nanokompozitnog premaza odnosno
mogućnost njihova raslojavanja. Tijekom istraživanja razmatrana je kompatibilnost PCL
polimera i nanočestica praćenjem morfologije određene SEM mikroskopom te određivanjem
termičkih (TG analizom) i mehaničkih svojstva (prekidne čvrstoće, prekidnog istezanja,
otpornost na: savijanje, obostrano savijanje, pucanje i otiranje) dvoslojnog ambalažnog
materijala. Provedena su mehanička ispitivanja postojanosti različitih ambalažnih oblika
(valjak, trostrana, četverostrana, peterostrana i šesterostrana prizma) na tlačno naprezanje.
Dodane nanočestice različito su unaprijedile uzorke otisnutog kartona s PCL premazima: ZnO
nanočestice dominantno su unaprijedile svjetlostalnost i smanjile propusnost na vodenu paru,
nanočestice SiO2 najviše su poboljšale mehanička svojstva kartona i kartonskih oblika, dok su
Al2O3 nanočestice uzrokovale najmanje promjene u boji tj. postigle najveći stupanj
transparentnosti PCL nanokompozita. Kod ispitivanih oblika ustanovljeno je da ambalaže
valjkastog oblika postižu najveći stupanj strukturalne stabilnosti na na tlačno naprezanje, a
oblik šesterokutne prizme utvrđen je kao optimalan s obzirom na odnos strukturalne
stabilnosti i uštedu prostora pri transportu. |
| Abstract (english) | Packaging paperboards are exposed to increased mechanical stress and deformations during
production and the use of packaging. This is a big issue when paperboards with a large
amount of non selected recycled cellulose material are used because recycled paperboards
have greatly decreased mechanical properties. Selection of packaging material has different
requirements depending on the type of the product. Despite having numerous advantages; like
strength to mass ratio, excellent printability, biodegradability and easy recycling, cellulose
packaging has a large disadvantage due to its permeability. This characteristic is usually
compensated by laminating or impregnating the paperboard using non-biodegradable
polymers which can complicate the recycling procedure.
In this study, polycaprolactone (PCL) was used in order to enhance properties of recycled
paperboard. PCL is a biopolymer which has good permeability properties but lacks in tensile
strength and transparency. In order to achieve the desired properties, PCL was modified with
aluminum oxide (Al2O3), silicon dioxide (SiO2) and zinc oxide (ZnO) nanoparticles. The
coating was prepared by dissolving PCL in ethyl-acetate, and nanoparticles were added using
a homogenizer. GD2 paperboard was offset printed with a color chart in order to investigate
the color change induced by the coatings. The weight of paperboard samples were 230 g/m2,
280 g/m2 and 350 g/m2. The coating was applied using a machine coater in four different
thicknesses: 4 μm, 24 μm, 40 μm and 80 μm.
The study was divided into five main stages. The first stage investigated the optimal
concentration of SiO2 nanoparticles in PCL coating needed to achieve the minimum color
change of the print, and to determine optimal thickness of the coating film. The color change
of the print coated with additional PCL nanocomposites (PCL-Al2O3, PCL-ZnO, PCLSiO2/Al2O3 and PCL-SiO2/ZnO) was determined in the second stage. The third stage explored
the adhesion, barrier, thermal and mechanical properties of the paperboard samples coated
with PCL nanocomposites. The samples were also characterized using SEM microscopy and
FTIR and UV-Vis spectroscopy. Later, in the fourth stage, the paperboard samples were
shaped into various packaging forms with the same share of the test material. The tested
forms were: triangular, quadrilateral (with three variations in the pages), pentagonal and
hexagonal prism, and cylinder. The packaging shapes were exposed to vertical pressure using
the crush test method to determine their structural stability and the effect of different coatings
on the mechanical properties. In the last, fifth stage, printed paperboard samples with PCLand PCL nanocomposite coatings were subjected to accelerated aging using a xenon lamp
chamber. The samples were additionally studied using FTIR analysis to establish whether
there was a change in the degradation properties of the PCL nanocomposites, and colorimetric
results were used to determine the level of lightfastness in order to define if the coatings
decreased the amount of color fading of print.
Research conducted in this study determined that the implementation of nanoparticles in the
polymer matrix improved PCL properties which, when applied, enhanced the properties of
printed paperboard. Implemented nanoparticles differently improved the properties of PCL
coated paperboards: ZnO nanoparticles predominantly improved lightfastness of print and
enhanced the water vapor permeability, SiO2 nanoparticles improved mechanical properties of
paperboards samples and packaging shapes, while Al2O3 nanoparticles enhanced the
transparency of PCL and caused the least amount of color change. Crush test of packaging
shapes found that the cylindrical shape achieved the highest degree of resistance to
compressive stress, but the hexagonal prism was determined as optimal due to its material to
volume ratio, degree of resistance to vertical pressure and optimal use of space during
transportation. |
