Predstavitve raziskovalnega dela FTPO na 2. Circul-a-bility konferenci
Med 12. in 14. septembrom 2022 je v Ljubljani potekala 2. Circul-a-bility mednarodna konferenca v organizaciji Inštituta za celulozo in papir (ICP) in v okviru COST akcije 191249: Re-Thinking Packaging for Circular & Sustainable Food Supply Chains of the Future.
Konferenca je vključevala raziskave, osredotočene na trajnostne rešitve za embalažno industrijo. Tako je konfereca zadružila znanstvenike iz različnih področij, ki so izmenjali rezultate raziskav, razpravljali o idejah in reštvah in tako pripomogli k hitrejšemu »zelenemu« prehodu na bolj trajnostno embalažo. Eden od razvojnih in raziskovalnih ciljev na FTPO so tudi biopolimeri, katerim se posvečamo že od ustanovitve fakultete. Tako smo svoje delo na konferenci predstavili s tremi prispevki, dva prispevka sta predstavila asist. Rebeka Lorber in viš. pred. Silvester Bolka, tretjega je predstavila Aleksandra Nešić iz Univerze v Novem Sadu, ki je predstavljene raziskave opravila v celoti na FTPO.
S prispevki FTPO smo vzbudili pozornost udeležencev konference, tako da smo stkali nove vezi tako v industriji kot znanstveni sferi.
POVZETKI PREDSTAVLJENIH PRISPEVKOV NA KONFERENCI:
PLA-PET blends: preparation and mechanical recycling
Rebeka Lorber, Aleksandra Nešić, Silvester Bolka, Blaž Nardin
Bio-based and bio-degradable polymers like polylactides (PLA) represent more sustainable solution due to their end of life and low carbon footprint thus may be used as alternatives to petroleum-based polymers in different applications. However, with biopolymers there are often certain drawbacks compared to conventional petroleum-based polymers, such as low toughness of PLA and poorer thermal performance which limit their practical applications. Blending of recycled PLA with recycled polyethylene terephthalate (PET) is a useful way to create new blends with improved properties, while simplifying the separation of waste bottle material, since PLA along with PET are among most used materials by consumption in bottle manufacture.
In present work, PLA bottles were ground and mixed with ground PET followed by compounding in a laboratory twin screw extruder. Three mixtures with different ratios 95/5, 90/10 and 85/15 of PLA/PET were prepared without the addition of a compatibilizer. Further, PLA/PET blends were processed by injection moulding. Injection moulded specimen of sizes according to ISO 527 (type 1BA), ISO 178 and ISO 179 standards were ground, and injection moulded again. Mechanical recycling was repeated 10 times. Thermal, mechanical, and optical properties were evaluated after 1st, 3rd, 5th, 7th, and 10th cycle of injection moulding.
The results suggest that addition of PET in PLA improves thermal stability of the materials. Mechanical and optical properties do not decrease dramatically even after 10 cycles of mechanical recycling, which indicates the potential of material as a sustainable option in broad range of applications.
PLA-PHA Blends: Biodegradation, Morphology, Mechanical And Thermal properties
Silvester Bolka, Ivana Burzic, Filip Miketa, Filip Brkic, Rajko Bobovnik, Blaž Nardin
Biobased polymers polylactides (PLA) and polyhydroxyalkanoates (PHA) are alternatives to petroleum-based polymers and represent a circular and sustainable solution. The biobased polymers often have serious drawbacks compared to conventional petroleum-based polymers. One is poor toughness of PLA which limit its practical applications. Blending of PLA with PHA is a useful way to create new blends with improved properties, which can overcome the poor toughness of neat PLA. The thermal and mechanical properties, morphology and biodegradability of PLA/PHA blends can be tuned by choosing the proper polymers and varying the composition of the blend. PLA and amorphous PHA copolymer were compounded in a laboratory extruder. Mixtures with different ratios of PLA and PHA were prepared without the addition of a compatibilizer. Pure PLA as reference and PLA/PHA blends were processed by cast extrusion. Films with a thickness of 20 μm to 50 μm and a width of about 220 mm were produced. The properties of the prepared films depend on the PHA content of the blend. The influence of the addition of an amorphous PHA copolymer to the PLA/PHA blend on the mechanical properties, biodegradability and morphology was investigated. The correlation of stiffness, strength and elongation at break with the kinetics of crystallisation of PLA in PLA/PHA blends, and the biodegradation behaviour as a function of the kinetics of crystallisation of PLA in PLA/PHA blends are presented in this paper. The mechanical properties of the prepared films were characterised in the extrusion direction and transverse to the extrusion direction. The different degree of crystallinity of PLA in PLA/PHA blends affects the transparency of the prepared 72 films. Tests were carried out with 10 wt.% and 20 wt.% PHA blends. The low PHA content in the blends was due to the high price of PHA compared to PLA. The results suggest that PLA/PHA blend films could also be used for packaging films, since the toughness of PLA/PHA blend films was much higher than that of pure PLA and thus comparable to that of films extruded from recycled polyethylene.
Multiple recycling of PLA - influence on the color change and mechanical properties
Aleksandra Nešić, Rebeka Lorber, Silvester Bolka, Blaž Nardin, Branka Pilić
Poly(lactide) (PLA) is the most common biobased and biodegradable polyester with a variety of applications for both high-performance and high-volume products. It is very suitable for applications in the packaging industry, since it can be processed on the existing process equipment with small modifications. Also, it can be modified to meet the requirements of the packed products regarding the gas permeability, mechanical and thermal properties. It is thoroughly examined through the years, and large scale production is established. One of the reasons why it was the material of choice for the food packaging industry was it’s biodegradability, since most of the food packaging is single-use and in most of the cases it is thrown away and finishes on the landfill. But, the biodegradability of the PLA is not so fast nor possible in all environments, but only under controlled conditions in industrial composters. For this reason, PLA should be properly collected and degraded under appropriate conditions, but still only a limited amount of polymers is allowed in the compost bin. Also, degradation of the materials should be the last step of the materials cycle, not the first, since the raw materials and energy are embedded into it and it would be better to recycle it instead of degrade it.
In this paper, the influence of multiple recycling of the PLA industrial waste on mechanical and sensorial properties was examined. Industrial waste PLA bottles were provided from the Slovenian company Stramex PET. The bottles undergo milling and extrusion, and then 10 cycles of injection molding followed by milling. The color of the samples evolved from transparent to slightly opaque when comparing the first and the last series of samples, which is not a drawback since this material will be processed into very thin packaging films. Melt flow rate was increasing with the number of the cycles of reprocessing, which was expected since the slight degradation of PLA occured due to the mechanical and thermal treatments. Tensile properties, flexural and impact strength were slightly decreasing through the series for the same reason. Overall, the difference between first and tenth cycle samples is not so significant, and it can be considered that PLA can undergo at least 10 cycles of mechanical recycling.