Effect of Type and Content of Diizocyanate on the Thermal and Mechanical Properties of Polyurethane/Polycarbonate Blends

U ovom radu istražen je utjecaj vrste i udjela diizocijanata u poliuretanskim elastomerima (PU) na njegovu mješljivost s polikarbonatom (PC) te je dobivena korelacija između sastava mješavina, vrste i udjela diizocijanata u PU-u, toplinskih i reoloških svojstva važnih za primjenu te mehaničkih svojstva. Mješavine PU/PC pripravljene su miješanjem elastomera PU na osnovi poliesterskog tipa poliola uz aromatski (MDI) i cikloalifatski (H12MDI) diizocijanat, različitih udjela diizocijanata (NCO/OH = 2/1 i 4/1) i PC-a u Brabender mikseru. Rezultati mjerenja DSC-om pokazali su kristalnu strukturu PU-a na osnovi tipa diizocijanata MDI u odnosu na PU s H12MDI tipom diizocijanata, koji ima amorfnu strukturu. Rezultati mjerenja DMA-om ukazuju na djelomičnu mješljivost mješavina PU/PC. Bolja mješljivost postignuta je kod mješavina PU/PC s tipom diizocijanata H12MDI i uz veći udjel tvrdog segmenta u odnosu na tip diizocijanata MDI. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.The miscibility of polyurethane/polycarbonate, PU/PC, blends prepared by mixing of PU elastomers based on polyester polyol as a soft segment and different type and content (NCO/OH=2/1 and 4/1) of hard segments (aromatic (MDI) and cycloaliphatic (H12MDI) diisocyanate) with PC was investigated. The correlation between the composition of the blends, different type and content of PU diisocyanate, thermal and rheological properties important for the application and the mechanical properties was obtained. The PU/PC blends of PU-elastomers and PC were prepared via melt mixing in a Brabender mixer. Differential scanning calorimetry (DSC) indicated that PU elastomers based on aromatic type of diisocyanate (MDI) had crystalline structure, while the PU elastomers based on cycloaliphatic type of diisocyanate (H12MDI) were of amorphous structure. The results obtained by dynamic mechanical analysis (DMA) indicated partial miscibility of PU/PC blends. The PU elastomers made from H12MDI type of diisocyanate and with higher hard segment content had better miscibility with PC than the PU elastomers made from MDI type of diisocyanate. This work is licensed under a Creative Commons Attribution 4.0 International License

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

Kinetics of Isothermal Crystallization for TPU/PP Blends

U ovom radu istražena je kinetika izotermne kristalizacije i kristalna struktura mješavina termoplastičnog poliuretana i polipropilena (TPU/PP) te termoplastičnog poliuretana i polipropilena uz dodatak talka (TPU/PP/T) različitog sastava (80/20, 50/50 i 20/80) diferencijalnom pretražnom kalorimetrijom (DSC). Kristalizacija je proučavana u području temperatura od 116 °C do 132 °C. Ustanovljeno je da je kristalizacija brža za mješavine TPU/PP/T. Kinetika izotermne kristalizacije opisana je pomoću Avramijeve jednadžbe. Utjecaj različite izotermne temperature proučavan je usporedbom vrijednosti kinetičkih parametara kao što su Avramijev eksponent, n, kinetička konstanta brzine kristalizacije, k, i polovično vrijeme kristalizacije, t1/2. Dobiveno je da se Avramijev eksponent kreće u rasponu od 1,18 do 2,31. Ti rezultati ukazuju na dvodimenzijski rast kristalnih jedinica. Kinetika izotermne kristalizacije pokazala je da se dodatkom talka povećava kristalište i raste konstanta brzine kristalizacije, k, mješavina TPU/PP. Za dane temperature kristalizacije, polovično vrijeme kristalizacije, t1/2, mješavina TPU/PP/T niže je od pripadajućih vrijednosti kod mješavina TPU/PP. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.The kinetics of isothermal crystallization and crystalline structure of thermoplastic polyurethane and polypropylene (TPU/PP) and thermoplastic polyurethane, polypropylene blends with addition of talc (TPU/PP/T) of different composition ratios (80/20, 50/50 and 20/80) were studied under isothermal conditions by differential scanning calorimetry (DSC). Crystallization studies were carried out in the temperature range of 116 °C to 132 °C. It was found that crystallization was faster for TPU/PP/T blends. Isothermal crystallization kinetics were described by means of the Avrami equation. The effects of different isothermal temperatures were studied by comparing the values of kinetic parameters, such as the Avrami exponent, n, the kinetic constant of the crystallization rate, k, and the crystallization half-time, t1/2. The Avrami exponent was evaluated to be in the range of 1.18–2.31. The results indicated the two-dimensional growth of crystalline units. The isothermal crystallization kinetics showed that the addition of talc increased the isothermal crystallization temperature and the crystallization rate constant, k, of TPU/PP blends. For the given crystallization temperatures, the crystallization half-time, t1/2, for the TPU/PP/T blends was lower than the corresponding value for TPU/PP blends. This work is licensed under a Creative Commons Attribution 4.0 International License

Preparation and Characterisation of Mixtures Based on Thermoplastic Polyurethane and Silk Fibroin

Fibroin svile (FS) jedinstven je i obećavajući prirodni polimer te zbog svoje biokompatibilnosti, biorazgradivosti i netoksičnosti ima velik potencijal za primjenu kao biomedicinski materijal. Unatoč svojoj čvrstoći, sam FS nije prikladan zbog svoje slabe fleksibilnosti. S druge strane, termoplastični poliuretan (TPU) vrlo je poželjan materijal za medicinsku primjenu upravo zbog njegove fleksibilnosti. Problem slabe fleksibilnosti FS-a mogao bi se riješiti miješanjem fleksibilnog TPU-a s FS-om. Cilj ovoga rada bio je pripremiti mješavine na osnovi TPU-a i prirodnog polimera FS-a. Mješavine TPU-a s FS-om pripremljene su umješavanjem FS-a u TPU u omjerima 5, 10, 15 i 20 mas. % FS-a u laboratorijskoj gnjetilici Brabender. Uzorci su dobiveni prešanjem na hidrauličkoj preši. Određena je struktura te toplinska i viskoelastična svojstva čistog TPU-a, FS-a i mješavina TPU/FS primjenom infracrvene spektroskopije s Fourierovim transformacijama (FTIR), diferencijalne pretražne kalorimetrije (DSC), dinamičko-mehaničke analize (DMA) i termogravimetrijske analize (TGA). Dobiveni rezultati FTIR analize pokazuju da je FS ugrađen u TPU matricu. Rezultati dobiveni mjerenjem DSC i DMA pokazali su da se dodatkom FS-a u TPU temperature staklastog prijelaza (Tg) izražene kao Teig, Tmg i Tefg snižavaju zbog smještanja amorfne faze FS-a (asparaginska kiselina) u amorfnu fazu TPU-a, čime dolazi do veće pokretljivosti polimernih lanaca. Temperature taljenja (Tm) izražene kao Teim, Tpm i Tefm u mješavinama TPU/FS neznatno se snižavaju u odnosu na čisti TPU zbog nastajanja slabije uređene kristalne strukture dodatkom FS-a. Toplinska postojanost neznatno se smanjuje dodatkom FS-a zbog njegove slabije toplinske postojanosti.Silk fibroin (SF), a unique and promising natural material extracted from silkworm, has gained much attention for its use as biomedical material, because of its biocompatibility, biodegradability, and nontoxicity. Despite its strength, SF alone is not appropriate because of its poor flexibility. Thermoplastic polyurethane (TPU) is a very desirable material for medical applications because of its flexibility. A solution to the problem of SF’s poor flexibility can be achieved by mixing flexible TPU with SF. The aim of this work was to examine the influence of FS content on the physical and thermal properties of TPU/FS blends. Blends of SF and TPU were prepared with melt mixing of TPU with 5, 10, 15, and 20 wt% of SF in a laboratory Brabender kneading chamber. The specimens of the neat components and their blends were moulded in a hydraulic press. The structural characteristics, thermal, and viscoelastic properties of neat TPU, SF and their blends (TPU/SF blends) were examined by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The FTIR results showed that the SF was successfully introduced to TPU matrix. Results obtained with DSC and DMA measurements showed that, when the SF content increased in the TPU/SF blends, the Tg, expressed as Teig, Tmg, and Tefg of the TPU, slightly shifted to lower temperature due to the incorporation of the amorphous phase of FS (aspartic acid) in the amorphous phase of TPU, and mobility of polymer chains increased. The melting temperature (Tm), expressed as Teim, Tpm, and Tefm, decreased because of the less organised crystal structure with the addition of SF. Thermal stability was determined by TGA, which showed that, with the addition of SF, the thermal stability decreased because of the lower thermal stability of SF

Primjena poliuretana u izradi potplata za cipele

Dobra obuća trebala bi biti udobna, dugotrajna i primjerena svrsi, a poliuretani (PU) su upravo materijali koji omogućuju dizajnerima da ispune sve ove ciljeve. Poliuretani se u industriji obuće koriste za izradu uložaka i potplata za cipele. Postoje dva tipa PU potplata na osnovi polietera i poliestera. PU potplati na osnovi polietera imaju visoku otpornost na hidrolizu i nisku otpornost na ulje dok PU potplati na osnovi poliestera imaju nisku otpornost na hidrolizu i visoku otpornost na ulje. U ovom radu istražena su toplinska i mehanička svojstva PU elastomera s polieter i poliester poliolom uz različite udjele tvrdog segmenta. Poliuretanski elastomeri priređeni su pretpolimernim postupkom. DSC tehnikom dobivena je djelomična kristalna struktura PU elastomera. Veću kristalnost imaju PU elastomeri s eterskim tipom poliola. Rezultati dobiveni DMA mjerenjem pokazuju da se staklište mekog segmenta povisuje i relaksacijski maksimum se proširuje povećanjem udjela tvrdog segmenta u PU elastomerima na osnovi esterskog tipa poliola uslijed interakcija između uretanske skupine i karbonilne skupine iz poliestera. Mehanička ispitivanja pokazuju porast prekidne čvrstoće s povećanjem udjela tvrdog segmenta

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

Antibacterial Properties of mTiO2 Filler in Biocomposites Based on Low Density Polyethylene and Rice Husks

Polietilen niske gustoće (LDPE) sintetski je nerazgradljiv polimer koji se najčešće upotrebljava kao ambalažni materijal za pakiranje hrane, međutim njegova nerazgradljivost ima loš utjecaj na okoliš. Razvoj i uporaba biorazgradljivih polimernih materijala ili plastike kao ambalažnog materijala za pakiranje hrane danas je u značajnom porastu. Biopolimeri predstavljaju jednu od najznačajnijih alternativa za razvoj ekološki prihvatljive ambalaže u prehrambenoj industriji zbog njihove biorazgradljivosti. Cilj ovoga rada bio je pripremiti biokompozite na osnovi linearnog polietilena niske gustoće (LDPE), rižinih ljuskica (RLJ) i punila mikro titanijeva dioksida (mTiO2) kako bi se dobili biorazgradljivi biokompoziti s antibakterijskim učinkom, pogodni za primjenu kao ambalažni materijali u prehrambenoj industriji. Biokompoziti su pripremljeni umješavanjem u laboratorijskoj Brabender gnjetilici. Ispitan je utjecaj različitog masenog udjela mTiO2 (w = 0,5, 1,0, 1,5 i 2,0 %) na inhibiciju bakterijske kulture Escherichia coli, Pseudomonas aeruginosa i Bacillus subtilis. Rezultati pokazuju da je mTiO2 inhibirao rast bakterijske kulture Escherichia coli, Pseudomonas aeruginosa i Bacillus subtilis kod masenog udjela mTiO2 od 1,5 i 2,0 % (broj stanica bakterijskih kultura se smanjivao). Rezultati TGA i DSC mjerenja pokazuju prisutnost mTiO2 u biokompozitima. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.Low-density polyethylene (LDPE) is a synthetic, non-degradable polymer most commonly used as a food packaging material; however, its non-degradability has an adverse effect on the environment. The development and use of biodegradable polymeric materials or plastics as packaging materials for food packaging has significantly increased. Biopolymers present one of the best alternatives for development of environmentally friendly packaging materials in the food industry due to their biodegradability. The aim of this study was to prepare biocomposites of low-density polyethylene (LDPE), rice husk (RH) and micro titanium dioxide (mTiO2) as a filler in order to obtain a biodegradable and antibacterial material suitable for use as a packaging material in the food industry. The biocomposites were prepared by melt mixing in laboratory Brabender mixer. Antibacterial effect of different mass fraction of mTiO2 (w = 0.5; 1.0; 1.5, and 2.0 %) on bacterial cultures of Escherichia coli, Pseudomonas aeruginosa, and Bacillus subtilis was investigated. The results showed that mTiO2 inhibited the growth of bacterial cultures of Escherichia coli, Pseudomonas aeruginosa, and Bacillus subtilis at the mTiO2 mass fraction of 1.5 and 2.0 % (the number of bacterial culture cells decreased). The results of TGA and DSC measurements showed that TiO2 was blended successfully into the biocomposites. This work is licensed under a Creative Commons Attribution 4.0 International License

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

The effect of silver addition on microstructure and thermal properties of the Cu–10%Al–8%Mn shape memory alloy

The influence of Ag addition on microstructure and thermal properties of the Cu-10%Al–8%Mn alloy was investigated in this work. Two alloys with designed compositions Cu-10%Al–8%Mn and Cu-10%Al–8%Mn-4%Ag (in wt.%) were prepared by induction melting of pure metals. Microstructures of the prepared samples were investigated in the as-cast state, after homogenization annealing and after quenching. The effects of different methods of heat treatment on the microstructure and transformation temperatures of the investigated Cu-10%Al–8%Mn and Cu-10%Al–8%Mn-4%Ag alloys were investigated using SEM-EDS and DSC techniques.It was determined that after induction melting microstructure of the both investigated alloys are primarily composed of martensite and a small amount of α-phase precipitates.Fully martensitic structure in both investigated alloys was obtained after direct quenching from the 850 °C into the ice water. Based on the DSC cooling curves it was determined that two-step martensite transformation for the both investigated alloys occur in the temperature interval from about 30 to -40 °C