Properties of Waste Polyamide Powder and Titanium Dioxide Nanocomposites

Selektivno lasersko sinteriranje (SLS) jedan je od važnijih postupaka 3D ispisa koji se u današnje vrijeme sve više primjenjuju za dobivanje različitih modela. Najvažniji polimerni materijali koji se upotrebljavaju u tom procesu su poliamidi. Značajan nedostatak tog procesa je velika količina otpadnog polimernog praha. Stoga je cilj ovoga rada bio istražiti utjecaj dodatka nanočestica titanijeva dioksida (TiO2) na toplinska i mehanička svojstva otpadnog poliamidnog praha (PA 2200). U ovom radu pripremljeni su nanokompoziti PA/TiO2 u rasponu masenog udjela punila 1 – 5 %, postupkom zamješavanja punila u talinu polimera u gnjetilici Brabender. Aglomerati nanopunila vidljivi su na SEM mikrografiji 5 %-tnog PA/TiO2 nanokompozita. Rezultati diferencijalne pretražne kalorimetrije (DSC) ukazuju na djelovanje nanočestica TiO2 kao heterogenih nukleacijskih centara. Također, dodatak nanopunila pospješuje stvaranje stabilnijih i uređenijih kristalnih struktura poliamidne matrice. Termogravimetrijskom analizom (TGA) dokazano je da dodatak TiO2 nanopunila povećava temperaturu početka razgradnje PA matrice, to jest poboljšava toplinsku postojanost PA matrice i neznatno povećava vrijednosti toplinske vodljivosti nanokompozita u odnosu na čistu polimernu matricu. Ispitivanjem mehaničkih svojstava uzoraka uočeno je smanjenje vrijednosti sekantnog modula te neznatne promjene naprezanja i istezanja u točki popuštanja s povećanjem udjela punila u nanokompozitu. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.The PA 2200 waste powder generated during selective laser sintering (SLS) process is an important environmental and economic problem. In order to test and modify the properties of the waste powder, nanocomposites based on polyamide matrix and TiO2 nanoparticles were prepared in this work. Agglomerates of the TiO2 nanofiller are visible on the SEM micrographs for the nanocomposite with 5 wt. % of the nanofiller (Fig. 1). The DSC analysis indicates an increase in crystallization temperature (Tc) by the addition of filler to the polymer matrix and it can be concluded that the TiO2 nanoparticles represent the nucleation centres in the PA matrix (Fig. 2, Table 1). In systems with 4 and 5 wt. % TiO2 crystallization enthalpy (ΔHc) and melting enthalpy (ΔHm) are higher than the values for the polyamide matrix (Table 1), indicating that the nanoparticles promote crystallization of the PA matrix. The results of TG analysis imply a positive effect of the TiO2 nanoparticles on the onset of thermal decomposition, which is most pronounced in the system with 3 wt. % TiO2 (Fig. 3, Table 2). As thermal degradation progresses further, the positive effect of the addition of TiO2 nanoparticles becomes less pronounced and finally becomes negative in the final stages, i.e. TiO2 nanoparticles accelerate the degradation. The thermal conductivity values (λ) are slightly higher for the nanocomposites relative to the pure PA matrix (Fig. 4) due to the formation of a more ordered structure of the polymer matrix by the addition of TiO2 and/or the formation of so-called conductive pathway. The results of the mechanical test indicate that the addition of TiO2 nanofiller decreases the values of the secant modulus (E), while the values of the yield stress (σ2>y2>y2 nanoparticles to the PA 2200 waste powder represents a useful approach for its reuse, thus improving the economic and environmental sustainability of the SLS process. The main disadvantage of the studied systems is the inconsistent mechanical properties at break. In future studies, this problem will be solved with adequate surface modification of TiO2 nanoparticles. This work is licensed under a Creative Commons Attribution 4.0 International License

Influence of Thermoplastic Polyolefins Flame Treatment on Coating Adhesion in Industrial Conditions of Robotic Dyeing

U ovom radu istražen je utjecaj obrade plamenom polipropilena (PP) i termoplastičnih poliolefina s talkom i čađom (TPO) na površinska svojstva i adheziju nanesenog premaza u uvjetima industrijskog procesa robotskog bojenja. Obrada plamenom provedena je na dvije udaljenosti plamena od površine (7,5 cm i 12,5 cm) pri konstantnom protoku zraka i metana te brzini kretanja plamenika. Toplinska postojanost netretiranih uzoraka ispitana je primjenom termogravimetrijske analize (TGA). Promjena toplinskih svojstava prije i nakon obrade plamenom praćena je primjenom diferencijalne pretražne kalorimetrije (DSC). Metodom kontaktnog kuta određena je površinska energija uzoraka prije obrade plamenom te 1 h i 24 h nakon obrade plamenom. Promjene uzrokovane obradom plamenom istražene su ATR – FTIR analizom, a morfološke promjene pretražnim elektronskim mikroskopom (SEM). Nakon nanošenja temeljnog sloja, sloja boje i sloja laka na površinu obrađenih uzoraka određena je adhezija standardnim metodama ISO 2409 i ISO 16925/D25 2018-B. Rezultati su pokazali da TPO uzorci koji sadrže punilo talk i čađu imaju bolju toplinsku postojanost u odnosu na PP. Obrada plamenom utječe na promjenu površinskih karakteristika uzoraka, povećanje slobodne površinske energije i na izgled/strukturu površine. ATR – FTIR analizom utvrđeno je postojanje polarnih skupina na površini nakon obrade plamenom. Svi obojeni uzorci prema zahtjevima normi zadovoljavaju uvjete izvrsne adhezije na međupovršini supstrat/premaz. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.In this paper, the influence of flame treatment on the surface properties of polypropylene (PP) and thermoplastic polyolefins with talc and carbon black filler (TPO), and adhesion of the applied coating in the conditions of industrial robotic dyeing process were investigated. The flame treatment was carried out at two distances from the flame (7.5 cm and 12.5 cm) at constant air and methane flows as well as speed of the burner. The thermal stability of untreated samples was investigated using thermogravimetric analysis (TGA). The change in thermal properties before and after flame treatment was investigated using differential scanning calorimetry (DSC). Changes of the samples’ surface energy were examined before flame treatment, 1 h and 24 h after flame treatment, by the contact angle method. Qualitative analysis of the surface chemical composition, before and after flame treatment, was performed by ATR – FTIR analysis, and morphological changes by scanning electron microscopy (SEM). After applying the base layer, dye and topcoat on the surface of the treated samples, the adhesion was determined by standard methods ISO 2409 and ISO 16925/D25 2018-B. The results showed that TPO containing talc and carbon black filler have better thermal stability compared to PP. Flame treatment influenced the surface characteristics of the samples, namely the increase in surface free energy and the appearance/structure of the surface. With ATR – FTIR, the existence of polar groups on the surface after flame treatment were determined. According to the standards, all dyed samples met the requirements of excellent adhesion on the substrate/coating interface. This work is licensed under a Creative Commons Attribution 4.0 International License

Ružička days : International conference 17th Ružička Days “Today Science – Tomorrow Industry” : Proceedings

In front of you are the Proceedings of the International Conference 17th Ružička days: „Today Science – Tomorrow Industry“ that was held in Vukovar, Croatia at September 19-21, 2018. The main goal of this interdisciplinary conference is to promote excellence in science and engineering as well as application of up-to-date research results and technological achievements in industry. In its fifth issue (2011, 2013, 2015, 2017, 2019) the Proceedings continues with publishing of quality scientific and professional full papers in sections Chemical Analysis and Synthesis (2), Chemical and Biochemical Engineering (3), Food Technology and Biotechnology (4), Medical Chemistry and Pharmacy (2), Environmental Protection (9) and Meeting of Young Chemists (4). All the papers were thoroughly reviewed from respectable evaluators, to whom we express our gratitude. We are also thankful to all the authors and participants of the Ružička days, and to all that support and contribute in its organization; especially our international coorganizers EuCheMS, EFFoST and EHEDG, the members of organizing and scientific committee, plenary and invited lecturers, sponsors, and of course our highly skilled and committed associates, which put a lot of effort in preparation of this book