Zeleni biokompoziti na bazi otpada taloga kave

Stalni rast tržišta kave uzrokuju velike količine nastanka otpada taloga kave (OTK) koji čini i do 95 % otpada nakon konzumacije kave. OTK skriva bogatstvo različitih resursa, koje treba samo prevesti u neki drugi oblik, pogodan za uporabu. S druge strane, današnja prekomjerna proizvodnja plastičnog otpada uvelike uzrokuje ekološki poremećaj na globalnoj razini u gotovo svim aspektima industrije, što uzrokuje ubrzanu uporabu biorazgradivih polimera i biokompozita. Upravo zbog enormnih količina nastanka OTK i spore biorazgradnje polilaktida (PLA), u ovome istraživanju ispitana su svojstva i biorazgradivost zelenih biokompozita PLA_OTK pripremljenih umješavanjem matrice polilaktida s različitim udjelima otpada taloga kave. Toplinska svojstva biokompozita ispitana su diferencijalnom pretražnom kalorimetrijom (DSC) i termogravimetrijskom analizom (TGA). Ispitana je raspodjela veličina čestica otpada taloga kave metodom laserske difrakcije te apsorpcija vode (AV). Biorazgradnja biokompozita provedena je procesom kompostiranja tijekom 19 dana. Rezultati ispitivanja toplinskih svojstava pokazali su da OTK kao punilo ne utječe na fazne prijelaze PLA matrice, ali utječe na smanjenje toplinske stabilnosti biokompozita PLA_OTK. Rezultati ispitivanja apsorpcije vode pokazali su da povećanjem udjela OTK dolazi do povećanja apsorpcije vode u biokompozitima zbog hidrofilnog karaktera punila. Iz fotografija svjetlosnog mikroskopa vidljiv je površinski napad mikroorganizama kod biokompozita s manjim udjelom OTK, dok je dublji prodor vidljiv kod biokompozita s većim udjelom OTK kao punila.
The continuous growth of the coffee market generates enormous amounts of spent coffee grounds (SCG), which account for up to 95 % of waste after coffee consumption. SCG contain a wealth of different resources that just need to be converted into another usable form. On the other hand, today’s excessive production of plastic waste in almost all industries worldwide is causing significant environmental pollution, leading to increased use of biodegradable polymers and biocomposites. Precisely because of the enormous amounts of SCG and the slow biodegradability of polylactide (PLA), this study aimed to investigate the properties and biodegradability of biocomposites made from green PLA and SCG, which were prepared by mixing the PLA matrix with different proportions of SCG. The thermal properties of the biocomposite were investigated by differential scanning calorimetry and thermogravimetric analysis. The particle size distribution of the SCG was studied by laser diffraction method, as well as the water absorption. The biodegradation of the biocomposite was carried out by a composting process of 19 days. The results of the thermal properties test showed that the SCG as filler did not affect the phase transitions of the PLA matrix, but it did affect the reduction of the thermal stability of the PLA_SCG biocomposite. The results of the water absorption test showed that increasing the amount of SCG leads to an increase in water absorption in biocomposites, due to the hydrophilic nature of the filler. On the light microscopic images, the surface attack of microorganisms was visible in biocomposites with lower SCG content, while deeper penetration was observed in biocomposites with higher SCG filler content.