Purpose
The purpose of this paper is to prepare stabile emulsions with 0–15% of colloidal silica and high monomer/water ratio and to investigate the influence of silica addition and surface ...modification on the polyacrylate properties.
Design/methodology/approach
Improving the properties of the composite can be achieved by optimizing the compatibility between the phases of the composite system with improving the interactions at the matrix/filler interface. Therefore, the silica surface was modified with nonionic emulsifier octylphenol ethoxylate, cationic initiator 2,2'-azobis-(amidinopropane dihydrochloride) and 3-methacryloxypropyltrimethoxysilane and polyacrylate/silica nanocomposites were prepared via in situ emulsion polymerization. Particle size distribution, rheological properties of the emulsions and morphology, thermal properties and mechanical properties of the film prepared from the emulsions were investigated.
Findings
Polyacrylate/silica systems with unmodified silica, silica modified with nonionic emulsifier and cationic initiator have micrometer, while pure PA matrix and systems with silica modified with silane have nanometer particle sizes. Addition and surface modification of the filler increased emulsion viscosity. Agglomeration of silica particles in composites was reduced with silica surface modification. Silica filler improves thermal stability and tensile strength of polyacrylate.
Originality/value
This paper provides broad spectrum of information depending on filler surface modification and latex preparation via in situ emulsion polymerization and properties with high amount of filler and monomer/water ratio with the aim that prepared latex is suitable for film formation and final application.
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 (TiO 2 ) 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/TiO 2 nanokompozita. Rezultati diferencijalne pretražne kalorimetrije (DSC) ukazuju na djelovanje nanočestica TiO 2 kao heterogenih nukleacijskih centara. Također, dodatak nanopunila pospješuje stvaranje stabilnijih i uređenijih kristalnih struktura poliamidne matrice. Termogravimetrijskom analizom (TGA) dokazano je da dodatak TiO 2 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.
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 TiO 2 nanoparticles were prepared in this work.
Agglomerates of the TiO 2 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 ( T c ) by the addition of filler to the polymer matrix and it can be concluded that the TiO 2 nanoparticles represent the nucleation centres in the PA matrix (Fig. 2, Table 1). In systems with 4 and 5 wt. % TiO 2 crystallization enthalpy (Δ H c ) and melting enthalpy (Δ H m ) 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 TiO 2 nanoparticles on the onset of thermal decomposition, which is most pronounced in the system with 3 wt. % TiO 2 (Fig. 3, Table 2). As thermal degradation progresses further, the positive effect of the addition of TiO 2 nanoparticles becomes less pronounced and finally becomes negative in the final stages, i.e. TiO 2 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 TiO 2 and/or the formation of so-called conductive pathway.
The results of the mechanical test indicate that the addition of TiO 2 nanofiller decreases the values of the secant modulus ( E ), while the values of the yield stress ( σ 2>y</sub) and yield elongation ( ε 2>y</sub) change slightly relative to the values obtained for the pure polymer matrix (Table 3).
In conclusion, the addition of TiO 2 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 TiO 2 nanoparticles.
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 study, the addition of carbon nanotubes (MWCNT) and modified carbon nanotubes (MWCNT-COOH) in the range of 0.5 wt. % to 5 wt. % in polyamide (PA) obtained as a residue upon 3D printing, was ...investigated. PA and nanocomposite samples were prepared by melt mixing. PA/MWCNT and PA/MWCNT-COOH nanocomposites were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), THB thermal conductivity determination method, electrochemical impedance spectroscopy (EIS), and tensile test. Results of DSC analysis showed that both types of carbon nanotubes (MWCNTs) acted as nucleation centres of PA matrix, but had no effect on the order of the crystalline structure. Due to the polar nature of the surface and better dispersion, MWCNT-COOH filler accelerated PA crystallization more significantly compared to MWCNT. Due to the presence of nanofiller, the PA chains had limited motion space, which interfered with the crystallization process of the matrix. The thermal stability of the PA matrix increased with the addition of both MWCNT and MWCNT-COOH fillers. Higher thermal conductivity was achieved with the addition of MWCNT-COOH filler compared to the addition of MWCNT. The results of the tensile test showed that with the addition of both types of MWCNT fillers in the PA matrix, the modulus of elasticity and yield stress had reduced, but the yield strain increased. Results of the EIS showed that MWCNT nanofiller had not changed the electrical conductivity regardless of modification.
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