Application of polyurethane in the production of shoe soles

Good footwear should be comfortable, long-lasting and fit for purpose, polyurethanes allow designers to meet all of these objectives. Polyurethanes are used in the footwear industry to make insoles and shoe soles.There are two types of PU soles a polyether and polyester based PU sole. Polyether based PU soles have a high resistance against hydrolysis and low oil resistance while polyester based PU soles have a low resistance against hydrolysis and high oil resistance. In this work thermal and mechanical properties of PU elastomers with polyether and polyester polols with different hard segment content were investigated. Differential scanning calorimetry (DSC) indicated partial crystalinity structure of the PU elastomers. PU elastomers based on polyether type polyol show the higher degree of crystalization. Based on DMA results , Tg values of the PU increases and broadened with increasing hard segment content in the PU elastomers based on polyester polyol, due to the interaction between the urethane groups and the ester carbonyl groups. Mechanical studies indicated that the tensile strength of PU elastomers increased with hard segment

Utjecaj toplinske obrade na mikrostrukturu i toplinska svojstva traka s prisjetljivosti oblika na bazi bakra

The aim in this work was to investigate the change in microstructure, phase transformation temperatures, and thermal properties due to the quenching of the investigated Cu-Al-Mn and Cu-Al-Mn-Ti alloys in ribbon form. This paper presents the results of microstructure analysis and thermal properties of Cu-Al-Mn and Cu-Al-Mn-Ti shape memory alloys produced in ribbon form by melt spinning technique. The microstructural analysis was carried out before and after quenching. After casting of the investigated alloys, annealing at 900 °C for 30 min was performed, followed by water quenching. The microstructural analysis was carried out by optical and scanning electron microscopy equipped with an energy dispersive spectrometer and by X-ray diffractometer. Thermodynamic calculation of a ternary Cu-Al-Mn system in equilibrium condition was performed using Thermo-Calc 5 software. Phase transformation temperatures were determined by differential scanning calorimetry and electrical resistance measuring. The results of microstructural analysis show the presence of martensite microstructures before and after quenching in the Cu-Al-Mn alloy, while in the Cu-Al-Mn-Ti alloy martensite microstructure exists only after quenching. Phase transformation temperatures decreased after quenching and titanium addition.Cilj rada bio je istražiti promjene u mikrostrukturi, temperaturama transformacije i toplinskim svojstvima nastale uslijed kaljenja Cu-Al-Mn i Cu-Al-Mn-Ti legura u obliku trake. U radu su prikazani rezultati mikrostrukturne analize i toplinskih svojstava Cu-Al-Mn i Cu-Al-Mn-Ti legura s prisjetljivosti oblika proizvedenih u obliku trake postupkom melt spinning. Mikrostrukturna analiza je provedena prije i nakon kaljenja. Nakon lijevanja istraživane legure su žarene pri 900 °C u trajanju 30 minuta, nakon čega je slijedilo kaljenje u vodi. Mikrostrukturna analiza je provedena optičkim i pretražnim elektronskim mikroskopom opremljenim energetsko disperzijskim spektroskopom te rendgenom. Termodinamički proračun ternarnog Cu-Al-Mn sustava proveden je u ravnotežnim uvjetima pomoću Thermo-Calc 5 programskog paketa. Temperature fazne transformacije određene su diferencijalnom pretražnom kalorimetrijom i mjerenjem električnog otpora. Rezultati mikrostrukturne analize pokazuju prisutnost martenzitne mikrostrukture prije i nakon kaljenja Cu-Al-Mn legure, dok u Cu-Al-Mn-Ti leguri martenzitna mikrostruktura postoji samo nakon kaljenja. Temperature faznih transformacija smanjuju se nakon kaljenja i dodatka titana

Effect of Micro and Nano TiO2 on UV Degradation behavior of TiO2 Reinforced Polycaprolactone Composites

In this work the influence of micro and nano titanium dioxide (TiO2) particles on the properties of polycaprolactone (PCL) based composites before and after UV radiation was investigated. The neat PCL and PCL / TiO2 micro and nanocomposites were radiated for 120 and 240h. DSC analysis showed that the melting temperature (Tm) decreased while the crystallization temperature (Tc) and degree of crystallinity (χc) increased when the composites were exposed to UV radiation. DMA analysis showed that the glass transition temperature (Tg) increased after UV irradiation. The addition of fillers leads to an increase in the initial weight loss (5 wt %) which decreases by time of exposing the samples to UV radiation. SEM showed that the addition of micro and nano TiO2 promote UV degradation of polymer matrix after 120 and 240 h degradation. The results of FTIR spectroscopy confirmed that the micro and nano TiO2 enhance the degradation process because of their photocatalytic activity. The PCL / TiO2 microcomposites showed higher changes in all investigated properties after UV radiation compared to the PCL / TiO2 nanocomposites. This work is licensed under a Creative Commons Attribution 4.0 International License

The Influence of Heat Treatment on Microstructure and Phase Transformation Temperatures of Cu-Al-Ni Shape Memory Alloy

This paper presents the results of thermal and microstructural analysis of Cu-Al-Ni shape memory alloy before and after heat treatment. After casting, a bar of Cu-12.8 Al-4.1 Ni (wt.%) alloy, obtained by the vertical continuous casting technique, was subjected to a certain heat treatment procedure. Solution annealing was performed at 850 °C for 60 min, followed by water quenching. Tempering was then performed at four different temperatures (150 °C, 200 °C, 250 °C and 300 °C). The microstructural results were obtained by optical and scanning electron microscopy. Thermodynamic calculation of ternary Cu-Al-Ni system under equilibrium was performed using Thermo-Calc 5 software. Phase transformation temperatures were determined by differential scanning calorimetry (DSC). The DSC results show the highest values of transformation temperatures in as-cast state. After solution annealing and tempering, the transformation temperatures show lower values with exceptional stability of Ms temperature (martensite start temperature)

Development of Shape Memory Alloys Based on Copper within Scientific Research Projects at the Faculty of Metallurgy, University of Zagreb

U ovom pregledu prikazan je dio znanstvenih istraživanja pri razvoju legura s prisjetljivošću oblika (engl. Shape Memory Alloy, SMA) na bazi bakra na Metalurškom fakultetu Sveučilišta u Zagrebu u razdoblju od 2006. do 2022. godine u suradnji s brojnim visokoškolskim i znanstvenim institucijama u regiji. Istraživane su sljedeće legure SMA: CuAlNi, CuAlMn, itd. Provedeno je fizikalno modeliranje uključujući numeričku simulaciju razvoja mikrostrukture i toplinsku analizu tih legura. Legure SMA rađene su u lučnoj, visokofrekventnoj i indukcijskim pećima pomoću tri različite tehnologije lijevanja: brzo skrućivanje, lijevanje u metalne i/ili grafitne kokile te kontinuirano lijevanje u šipke. Nakon toga odabrane legure su toplo i hladno valjane. Provedena je toplinska obrada (austenitizacija uz naknadno gašenje u vodi i žarenje) i karakterizacija funkcionalnih svojstava legura SMA u različitim stanjima. Za karakterizaciju, osim ispitivanja mehaničkih svojstava, primijenjene su brojne visokosofisticirane metode: optička mikroskopija (OM), pretražna (SEM) i transmisijska elektronska mikroskopija (TEM), energetsko disperzijska-spektroskopija (EDS), pretražna diferencijalna kalorimetrija (DSC), dinamičko-mehanička analiza (DMA), rendgenska difrakcija (XRD), elektrokemijska impedancijska spektroskopija (EIS) itd. Već pri lijevanju kod pojedinih legura SMA, a posebice nakon toplinske obrade austenitizacijom uz naknadno gašenje u vodi, utvrđena je martenzitna mikrostruktura koja je osnovni preduvjet za svojstvo prisjetljivosti oblika. Na temelju provedenih istraživanja po većini parametara (plastičnost, korozijska otpornost itd.) može se zaključiti da su se najbolje pokazale legure CuAlMn. Kao rezultat provedenih istraživanja na legurama SMA, prema podatcima iz baze CROSBI (na dan 23. prosinca 2022.), istraživački tim objavio je 33 rada u časopisima (od kojih su 23 rada u časopisima indeksiranim u bazi podataka Web of Science), 74 rada u zbornicima međunarodnih konferencija, 18 sažetaka u zbornicima konferencija te pet ostalih radova. Također, obranjena je jedna doktorska disertacija te je izrađeno i obranjeno 12 završnih i 25 diplomskih radova u području tehničkih znanosti iz znanstvenih polja metalurgije i kemijskog inženjerstva.This review presents part of scientific research in the development of shape memory alloys (SMA) based on copper at the Faculty of Metallurgy of the University of Zagreb in the period from 2006 to 2022, in cooperation with a number of universities and scientific institutions in the region. The following SMA alloys were studied: CuAlNi, CuAlMn, etc. Physical modelling, including numerical simulation of microstructure evolution and thermal analysis were performed. The SMA alloys were produced in arc, high-frequency, and induction furnaces by means of three different technologies: melt spinning, casting in metallic and/or graphite moulds, and continuous casting in bars. The selected SMA alloys were then hot and cold rolled. The heat treatment (quenching and tempering) and the characterisation of the functional properties of the SMA alloys under the different conditions were carried out. Numerous sophisticated methods were used to characterise the functional properties, in addition to testing the mechanical properties: optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), dynamic mechanical analysis (DMA), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), etc. According to several parameters (ductility, corrosion resistance, etc.), it could be concluded that CuAlMn was the best alloy. As results of this investigation on SMA alloys, according to the CROSBI database (by December 23, 2022), the research team has published 33 articles in journals (including 23 articles in journals indexed in the Web of Science database), 74 papers in proceedings of international conferences, 18 abstracts in proceedings of conferences, and 5 other papers. In addition, 1 doctoral thesis, 12 bachelor theses, and 25 master theses were prepared and defended in the field of technical sciences in the areas of metallurgy and chemical engineering

Properties of continuously casted Cu-Al alloy

In this work are shown properties of continuously casted Cu – 9.1Al alloy before and after heat treatment. The continuously cast cylindrical bar with 8 mm diameter was produced using the device for the vertical continuous casting which is connected with the vacuum induction furnace. Heat treatment was consisted of annealing at 900 °C/30 minutes and water quenching. Microstructural analysis was performed by optical microscopy (OM), scanning electron microscopy (SEM) equipped by device for energy dispersive spectroscopy (EDS) and using differential scanning calorimeter (DSC). Also, hardness and mechanical properties were measured. EDS analysis confirmed that as-cast state of Cu – 9.1Al alloy is successfully done and alloy with homogeneous composition was produced. Optical and scanning electron microscopy showed existence of dual-phase α+β microstructure, which keeps after heat treatment but with certain sporadic changes of α - phase shape. DSC analysis on all samples presented one endothermic change of the heat flow during the heating, which probably represents α→β transformation and one exothermic change of the heat flow during the cooling which probably represents β→α transformation. The effect of heat treatment on the hardness and yield strength values is insignificant, while the tensile strength decreases with annealing

Utjecaj toplinske obrade na mikrostrukturu i mehanička svojstva legure Cu-Al-Mn s prisjetljivosti oblika

The 8-mm diameter bars of Cu-Al-Mn shape memory alloys were produced by continuous casting technique. The samples were characterised using optical microscopy and scanning electron microscopy along with EDX analysis. The continuous cast alloy revealed some martensitic phase, which, after quenching, led to the microstructure that is completely martensite. Quenching of samples had an effect on several mechanical properties and change in morphology of fracture. After ageing at 200 °C and 300 °C, the tensile strength increased and elongation drastically decreased. Morphology of fracture surface changed from primary ductile to a mixture of intergranular and ductile. This work is licensed under a Creative Commons Attribution 4.0 International License.Šipke promjera 8 mm proizvedene su iz legure Cu-Al-Mn s prisjetljivosti oblika tehnikom kontinuiranog lijevanja. Uzorci su karakterizirani pomoću optičke mikroskopije i pretražne elektronske mikroskopije uz analizu EDX. Kontinuirano lijevana legura je pokazala mjestimičnu prisutnost martenzitne faze, dok je nakon kaljenja nastala potpuno martenzitna mikrostruktura. Kaljenje uzoraka utjecalo je na mehanička svojstva i na promjenu morfologije prijeloma. Nakon starenja pri 200 °C i 300 °C porasla je vlačna čvrstoća a izduženje se drastično smanjilo. Morfologija prijelomne površine se mijenjala od duktilne do mješavine interkristalne i duktilne. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna

The effect of heat treatment on the microstructure and mechanical properties of Cu- Al-Mn shape memory alloy

The 8 mm diameter bars of Cu-Al-Mn shape memory alloys were produced by continuous casting technique. The samples were characterised using optical microscopy and scanning electron microscopy along with EDX analysis. The continuous cast alloy revealed some martensitic phase which, after quenching, led to the microstructure that is completely martensite. Quenching of samples had an effect on several mechanical properties and change in morphology of fracture. After ageing at 200 °C and 300 °C the tensile strength increased and elongation is drastically decreased. Morphology of fracture surface was changed from primary ductile to a mixture of intergranular and ductile

Preparation and Characterization of Biocomposite Based on Polylactide (PLA) and Bacterial Nanocellulose (BNC)

Polilaktidna kiselina (PLA) i bakterijska nanoceluloza (BNC) zbog svoje biorazgradljivosti, biokompatibilnosti i netoksičnosti imaju velik potencijal za primjenu u biomedicini. Cilj ovog rada bio je pripraviti i ispitati biokompozit PLA/BNC. Istražen je utjecaj BNC-a na morfološku strukturu, kemijski sastav, toplinska svojstva, toplinsku postojanost i hidrofobnost PLA te zasijavanje i rast stanica biokompozita PLA/BNC primjenom pretražnog elektronskog mikroskopa (SEM), infracrvene spektroskopije (FTIR), diferencijalne pretražne kalorimetrije (DSC) i termogravimetrijske analize (TGA) te određivanjem kontaktnog kuta i metodom MTT. Dodatkom BNC-a u PLA dolazi do pomaka staklišta (Tg) prema nižim temperaturama, što ukazuje na veću pokretljivost amorfne faze PLA te porasta stupnja kristalnosti zbog nukleacijskog učinka celuloze. Početak toplinske razgradnje pomaknut je na niže temperature u odnosu na čisti PLA, što ukazuje na smanjenje toplinske postojanosti PLA dodatkom BNC-a. Biokompozit PLA/BNC pokazuje poroznu, vlaknastu strukturu. Test zasijavanja stanica pokazao je da je biokompozit PLA/BNC pogodan za prihvaćanje i rast humanih stanica, pa je prema tome potencijalno primjenjiv u regenerativnoj medicini i tkivnom inženjerstvu. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.Polylactic acid (PLA) and bacterial nanocellulose (BNC) are promising materials in medicine due to their biodegradability, biocompatibility, and non-toxicity. The aim of this work was to prepare and characterize the PLA/BNC biocomposite. Morphology, chemical composition, thermal properties, thermal stability, hydrophobicity and cell seeding, and growth of the PLA/BNC biocomposite were characterized by means of scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), contact angle, and MTT method. DSC showed that the glass transition temperature (Tg) of PLA decreased with the addition of BNC due to higher mobility of amorphous PLA phase. The degree of crystallinity increased due to nucleation effect of cellulose. With the addition of BNC, the thermal stability of biocomposite decreased. The PLA/BNC biocomposite exhibited a porous, fibrous structure. The cell seeding test showed the PLA/BNC biocomposite to be suitable for growth of human cells, and therefore, potentially applicable in regenerative medicine and tissue engineering. This work is licensed under a Creative Commons Attribution 4.0 International License

Electrospun Polycaprolactone for Controlled Drug Delivery

Tkivno inženjerstvo dobra je alternativa za razvoj tkiva ili potencijalnih organa iz pacijentova vlastitog staničnog materijala, a kako bi se smanjio problem nedostatka organa za transplantaciju. Elektroispredeni materijali su dobri kandidati kod primjene u biomedicini tj. kao nosači za uzgoj tkivnih stanica. Kod regeneracije tkiva mogu dodatno prenositi lijekove kontrolirano prema terapiji. U ovom je radu istraživano kontrolirano otpuštanje antibiotika Cefuroxima (CFU) koji se upotrebljava u terapiji okularnog tkiva. Elektroispredeni su polikaprolaktonski nosači uz dodatak CFU-a u udjelima od 1, 2, 5 i 10 mas %. Uspješna kapsulacija antibiotika potvrđena je pojavom novih karakterističnih pikova u FTIR spektrima elektroispredenih mješavina. Dodatkom antibiotika i povećanjem njegove koncentracije dobivaju se vlakna homogenijeg izgleda s manjim brojem deformacija po duljini vlakna. UV-VIS spektrofotometrijom praćeno je vrijeme otpuštanja antibiotika iz elektroispredenih PCL/CFU nosača. Dobiveno je povećanje apsorbancije antibiotika s vremenom i porastom koncentracije lijeka u nosaču. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.Tissue engineering is a good alternative for the development of tissue or potential organs from the patient’s own cell material in order to reduce the problem of organ transplant deficiency. Electrospun materials are good candidates for use in biomedicine, as scaffolds for tissue cells culture. Additionally, these scaffolds can provide controlled drug release in tissue regenerative therapies. In this paper, controlled release of antibiotic Cefuroxim (CFU), which is used for ocular tissue therapy, was investigated. The polycaprolactone scaffolds were prepared by electrospinning with the addition of CFU in the amount of 1, 2, 5, and 10 wt %. The successful antibiotic capsulation was confirmed by the new characteristic peaks appearing in the FTIR spectra of the electrospun blends. With the addition of antibiotic and increase in its concentration, fibres with more uniform morphology and less deformations along the fibres length were obtained. The release of antibiotic from PCL scaffolds was determined by UV–VIS spectrophotometer. Obtained was an increase in absorption of antibiotics with time and with increased drug concentration in the scaffolds. This work is licensed under a Creative Commons Attribution 4.0 International License