Customization of flexographic printing plates related to uvc-induced changes in the crosslinking degree

In this paper, the swelling properties of photopolymer flexographic printing plates related to the variations of UVC post-treatment have been analysed. The aim of the research was to interconnect the changes in the cross-linking degree of the photopolymer material occurring due to the modified UVC radiation of the printing plate and the changes of its surface free energy crucial in the graphic reproduction process. Changes in the crosslink-ing degree in the photopolymer materials have been analysed by the swelling experiments. Results have proven that the partial dissolution of the photopolymer material caused by the immersion of the printing plates in vari-ous solvents is in the direct relation with the changes of the dispersive surface free energy. UVC post-treatment, used for the crosslinking termination and the definition of the surface properties of printing plates, is therefore directly affecting the resistivity of the printing plate in the solvent environment. By calculating the correlation coefficients for the weight loss of the photopolymer material in solvents and the dispersive surface free energy, the relation between the crosslinking degree and the UVC post-treatment has been established

Thermal, surface and mechanical properties of PCL/PLA composites with coconut fibres as an alternative material to photopolymer printing plates

In this paper, methods of thermal, mechanical and surface analyses of biodegradable PCL/PLA composites with the addition of different concentrations of coconut fibres were performed. The aim was to assess the potential of these composite materials for the relief-printing plates as an alternative to classical photopolymer materials. Differential scanning calorimetry, surface free energy calculations and hardness measurements were performed on the samples. Results have shown that most thermal transitions that are characteristic for PLA and PCL do not take place in the area of temperatures applicable in the printing process. Most thermal transitions were not affected by the addition of coconut fibres. Coconut fibres in the composite structure contributed to the increased hardness of the material. Moreover, the hardness range of the prepared PCL/PLA composites was within the range of some classic photopolymer printing plates. By adding coconut fibres in higher concentrations, surface free energy of the materials decreased, which enables a wider application of the material for the production of printing plates. From the obtained results it can be concluded that there is a potential for the use of PCL/PLA biodegradable composite materials in the manufacture of various relief-printing plates for different printing techniques (letterpress, embossing, label printing)

Synthesis of ethylene-propylene-diene-graft-polystyrene copolymers of various structures

Kako bi se istražila mogućnost sinteze cijepljenih kopolimera različite strukture, pri sintezi je cijepljen etilen/propilen/dienski kaučuk (EPDM) i polistiren (PS) različitih gustoća bočnih grana. Dobiven je kopolimer etilen/propilen/dienskog kaučuka i polistirena (EPDM-g-PS). Tijekom sinteze rabljena su tri različita EPDM-a koja se međusobno razlikuju s obzirom na sadržaj dvostrukih veza i propilena. Sinteza cijepljenih kopolimera provedena je pri temperaturi od 90 °C u toluenu, uz inicijator dibenzoil-peroksid (DBP). Vrijeme polimerizacije mijenjano je radi dobivanja različite strukture cijepljenih kopolimera. Cijepljeni kopolimeri izdvojeni su iz reakcijske smjese metodom prema Soxletu. Sintetizirani cijepljeni kopolimeri karakterizirani su određivanjem staklišta (Tg), određivanjem prosjeka molekulskih masa ( ) te određivanjem slobodne energije površine. Rezultati određivanja staklišta, prosjeka molekulskih masa kao i slobodne energije površina pokazuju da porast vremena polimerizacije i promjena temeljnog lanca cijepljenog kopolimera utječu na koncentraciju bočnih grana, koja određuje strukturu i sastav kopolimera.To study the relationship of different structures on properties, ethylene-propylene-diene-graft-polystyrene (EPDM-g-PS) copolymers, with different graft density were synthesized. For this purpose three different types of EPDM copolymers which differ by concentration of double bonds and propylene were used. The synthesis was carried out at 90 °C in toluene solution using dibenzoyl-peroxide as initiator. Variation of polymerization time was applied to obtain different structures of graft copolymers. Graft copolymers were extracted from mixture of polymers obtained by polymerization. The chain structure of the synthesized graft copolymers was followed by glass transition temperature (Tg), by molecular masses, ( ) and by surface energy. The results of glass transition temperature, of molecular masses and free surface energy show that with extended polymerization time and with various types of main chains of graft copolymers affect the concentration of side branches, which determines the structure and composition of graft copolymer

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

Polypropylene Blends with m-EPR Copolymers: Mechanical and Rheological Properties

The effects of two metallocene ethylene-propylene-based elastomers (m-EPR1 and m-EPR2) differing in molecular mass and viscosity on mechanical, rheological and interfacial properties were compared. The m-EPR elastomers were added to iPP in 2.5, 5, 10, 15, and 20 vol.%. Torque values, elongation at break and impact strength measured of the iPP/m-EPR1 blends were higher than the iPP/m-EPR2 blends due to higher molten viscosity of m-EPR1 than m-EPR2 copolymer. Slight differences in Young moduli as well as in tensile strength at yield and at break might indicate that tensile properties of iPP/m-EPR blends were not significantly affected by difference in viscosity or molecular mass, miscibility and spherulite size. Optimization diagrams indicated the metallocene m-EPR copolymers are efficient impact modifiers for polypropylene and showed good balancing of mechanical properties in iPP/m-EPR blends

Ružička days : International conference 16th Ružička Days “Today Science – Tomorrow Industry” : Proceedings

Proceedings contains articles presented at Conference divided into sections: open lecture (1), chemical analysis and synthesis (3), chemical and biochemical engineering (8), food technology and biotechnology (8), medical chemistry and pharmacy (3), environmental protection (11) and meeting of young chemists (2)

The adhesion phenomena in polypropylene/wollastonite composites

Modification of polypropylene (PP) with wollastonite fillers was investigated in this paper. Three types of different silane pretreated wollastonite mineral filler were used for preparation of binary PP/wollastonite composites. The composite samples were homogenized in a Brabender Plasti-Corder kneading chamber and compression moulded into plates on a laboratory press. The adhesion between the wollastonite fillers used in this study and the PP matrix was predicted on the basis of the calculated adhesion parameters (work of adhesion, interfacial free energy and spreading coefficient) obtained by the surface free energy of pure materials. The contact angle method was used to determine surface free energy of components. The obtained values of adhesion parameters at the interface in the composites were correlated with mechanical properties as well as morphology observations of corresponding composites and were proved to be in relatively good agreement with the mechanical property measurements. Stronger adhesion in investigated composites has reflected in higher yield stress and tensile strength at break but in lower elongation at break and impact resistance.Preučevali smo modifikacijo polipropilena (PP) z wollastonitom kot polnilom. V ta namen smo uporabili tri različne tipe wollastonitov, obdelanih z različnimi silani. Vzorce kompozitov smo pripravili v talini v Brabenderjevem gnetilniku in s stiskanjem v plošče v laboratorijski stiskalnici. Predvideli smo jakost adhezije med uporabljenimi polnili in PP matriko na osnovi izračunanih adhezijskih parametrov (adhezijsko delo, prosta energija medpovršine in koeficient omočenja), ki smo jih izračunali iz prostih energij površine posameznih komponent. Za določanje proste energije površine komponent smo uporabili metodo kontaktnega kota. Dobljene vrednosti adhezijskih parametrov na medpovršini smo korelirali z mehanskimi lastnosti in morfološkimi raziskavami preučevanih kompozitov in pri tem ugotovili njihovo dobro skladnost z rezultati mehanskih lastnosti. Močnejša adhezija v preučevanih PP/wollastonit kompozitih se je odražala v višjih vrednostih meje plastičnosti in pretržne trdnosti, medtem ko so bile vrednosti raztezka ob pretrgu in zarezne udarne žilavosti nižje

Blends Based on Poly(ε-Caprolactone) with Addition of Poly(Lactic Acid) and Coconut Fibers: Thermal Analysis, Ageing Behavior and Application for Embossing Process

In this research a biodegradable blend of poly(ɛ-caprolactone) (PCL) and poly(lactic acid) (PLA) is proposed as a new material for the production of a relief printing plate used for special applications on packaging materials, i.e., the embossing process. Coconut fibers (CFs) were added as a natural filler to PCL/PLA blends to improve the functional properties of the prepared blends. Thermal, mechanical and surface analyses were performed on the unaged and artificially aged blends. The results showed that CF has been proven to optimize the hardness of the blend, which is crucial for the production of relief plate for embossing applications. The lowest hardness was measured on neat PCL (53.30° Sh D) and the highest value on PCL/PLA/CF 70/30/3.0 blend (60.13° Sh D). Stronger interfacial interactions were present at the PLA/CF interface because the interfacial free energy is closer to zero and the work of adhesion and spreading coefficient are higher than for the PCL/CF interface. The results of thermal analysis of unaged and aged blends showed that ageing for 3 weeks resulted in significantly lower thermal stability, especially for neat PCL and PCL/PLA 80/20 blends. Blends with a higher content of PLA and CF showed a slightly increased ageing resistance, which is attributed to the increased crystallinity of PLA after ageing due to the addition of CF showed in the DSC diagrams

The Role of the Interface in Multiphase Polymer Systems Filled with Nanoparticles

Poboljšanje adhezijskih svojstava na međupovršini u nanokompozitima, u odnosu na standardne mikrokompozite, posljedica je velike specifične površine nanopunila i uspostavljenih interakcija na nanorazini. U ovom radu dan je pregled rezultata istraživanja svojstava međupovršine i svojstava materijala u uvjetima promjene parametara adhezije kontroliranom predobradom površine punila. Predobrada nanopunila kalcijeva karbonata (CaCO3) silanom, stearinskom kiselinom, radijacijskim cijepljenjem poli(vinil-acetata) i/ili njihovom kombinacijom mijenja adhezijske parametre na međupovršini u istraživanim kompozitima i polimernim mješavinama na osnovi poliuretana (PUR) i poli(vinil-acetata) (PVAC). Energija površine komponenata u kompozitu i polimernoj mješavini mjerena je metodom kontaktnoga kuta. Morfologija je istražena primjenom optičke mikroskopije, a mehanizam popuštanja kompozita tehnikom pretra`ne elektronske mikroskopije (SEM). Mehanička svojstva kompozitnih sustava određena su rasteznim ispitivanjem, a toplinska svojstva metodom diferencijalne pretražne kalorimetrije (DSC). Strukturne promjene matrice pod utjecajem nanopunila analizirane su metodom raspršenja rendgenskih zraka pod malim kutom (SAXS). Rezultati poboljšanja mehaničkih svojstava polimernih sustava punjenih nanočesticama u vezi su s postignutom homogenom morfologijom i smještanjem nanopunila na međupovršini u uvjetima optimalne adhezije. Uvjeti optimalne adhezije u kojima je energija međupovršine minimalna i teži nuli, a postižu se kontroliranom predobradom površine punila, rezultiraju znatno boljim svojstvima u odnosu na sustave u kojima su uvjeti na međupovršini daleko od optimalnih.Improvements in adhesive properties at the interface in nanocomposites, with respect to the standard microcomposites, are a consequence of the great specific surface area of nanofillers and established interactions at nanolevel. An overview of investigations related to the interface and material properties in the conditions of the changed parameters of adhesion by the controlled pre-treatment of the filler surface is given in this paper. The pre-treatment of nanofiller calcium carbonate (CaCO3) by silane, stearic acid, irradiation grafting of poly(vinyl-acetate) and/or its combination changed the adhesion parameters at the interface in the investigated composites and polymer blends based on polyurethane (PUR) and poly(vinyl acetate) (PVAC). The surface energy of the components in the composite and polymer blends is measured by a contact angle technique. The morphology of composites is investigated by the optical polarization microscopy and the failure mechanism by the scanning electron microscopy (SEM). Mechanical properties of composites are determined by a tensile test and thermal properties by the differential scanning calorimetry (DSC) technique. Structural changes of the matrix under the influence of nanofillers are analyzed by the small angle X–ray scattering (SAXS) technique. Improved results in mechanical properties are related with the homogeneous morphology and the preferential location of nanofillers at the interface. Conditions of the optimal adhesion when the interfacial energy between nanofillers and a particular matrix is minimal and tends to zero can be achieved by a controlled filler surface pre-treatment. They result in significantly improved properties in comparison to the systems with the conditions at the interface that cannot match the optimal ones