20 research outputs found

    Нанокомпозити на бази термопластичног линеарног поли(уретан-силоксан)а и органоглине: утицај састава на својства

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    Thermoplastic poly(urethane-siloxane)/organoclay nanocomposites (TPU NCs) with different hard segment content (20–55 wt. %) were prepared by in situ polymerization in the presence of organically modified montmorillonite as a nanofiller (Cloisite 30B; 1 wt. %). Hydroxyl-terminated ethoxypropyl- poly(dimethylsiloxane) was used as soft segment, while 4,4'-methylenediphenyl diisocyanate and 1,4-butanediol were the hard segment components. The study of the influence of the hard segment content on the functional properties of TPU NCs was performed by Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometry (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), dynamic mechanical thermal analyses (DMTA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), water contact angle and water absorption tests. The results revealed that TPU NCs with the increasing hard segment content exhibit higher values of degree of microphase separation, melting temperature of the hard segments, degree of crystallinity, storage modulus (except for TPU NC-55), but lower thermal stability and hydrophobicity. TPU NC films were hydrophobic and their free surface energy was in the range from 17.7 to 24.9 mJ m-2. This work highlights how the composition of TPU NCs would affect their functional properties and provide an additional composition intended for designing advanced TPU NC materials for special biomedical applications.Термопластични поли(уретан-силоксан)/органоглина нанокомпозити (TPU NCs) са различитим садржајем тврдих сегмената (20–55 теж. %) припремљени су in situ полимеризацијом у присуству органски модификованог монтморилонита као нанопуниoца (Cloisite 30B; 1 теж. %). Као меки сегмент коришћен је хидроксиетоксипропил терминирани поли(диметилсилоксан), а као компоненте тврдог сегмента коршћени су 4,4'- -метилендифенилдиизоцијанат и 1,4-бутандиол. Проучавање утицаја садржаја тврдог сегмента на функционална својства TPU NCs је испитивано FTIR спектроскопијом, дифракцијом X-зрака (XRD), микроскопијом атомских сила (AFM), скенирајућом електронском микроскопијом (SEM), динамичко механичко термичком анализом (DMTA), диференцијално скенирајућом калориметријом (DSC), термогравиметријском анализом (TGA), тестовима одређивања контактног угла са водом и апсорпције воде. Резултати су показали да TPU NCs са већим садржајем тврдих сегмената показују веће вредности степена микрофазне сепарације, температуре топљења тврдих сегмената, степена кристалиничности, модула сачуване енергије (осим за TPU NC-55), али нижу термичку стабилност и хидрофобност. TPU NC филмови су били хидрофобни и њихова површинска енергија је била у опсегу од 17,7 до 24,9 mJ m-2. Овај рад истиче како би се променом састава у TPU NCs подешавала функционална својства и обезбедило додатно подешавање састава за дизајнирање напредних TPU NC материјала за специјалне биомедицинске примене

    Novel siloxane based polyurethane nanocomposites

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    A series of novel thermoplastic polyurethanes (TPUs) nanocomposites based on α,ω–dihydroxy ethoxy propyl poly(dimethylsiloxane) (EOPDMS), 1,4-butanediol (BD) and 4,4'-diphenylmethane diisocyanate (MDI) was synthesized by in situ two-step polyaddition reaction in solution using modified clay (Cloisite 30B). The clay percentage in the nanocomposites was 1, 3, 5, 8 and 10 wt% in relation to the polymers. The aim of this study was to improve some properties of TPUs by the addition of clay nanoparticles. The prepared nanocomposites were characterized using FTIR, AFM and DSC analyses. The influence of nanoparticles dispersion on the morphology and thermal properties of TPUs was investigated

    Proučavanje morfologije i termomehaničkih svojstava umreženih poli(uretan-siloksana) na bazi hiperrazgranatog poliestra

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    Two series of polyurethane films based on hyperbranched polyester of the second pseudo-generation (Boltorn®), 4,4'-methylenediphenyl diisocyanate and two different siloxane prepolymers, α,ω-dihydroxy-(ethylene oxide-poly(dimethylsiloxane)-ethylene oxide)(EO-PDMS-EO) and α,ω-dihydroxypropyl-poly(dimethylsiloxane) (HP-PDMS), were prepared by two-step polymerization in solution. The influence of the type and content of soft segment on the morphology, thermomechanical and surface properties of the synthesized polyurethanes was studied by atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA) and water absorption measurements. It was found that these techniques confirmed existence of microphase separated morphology. Synthesized polyurethanes exhibited two glass transition temperatures and one second relaxation process. The results showed that polyurethanes based on HP-PDMS had higher surface roughness, better microphase separation and waterproof performances. Samples synthesized with lower PDMS content had less hydrophobic surface, but higher crosslinking density and better thermomechanical properties.U ovom radu pripremane su dve serije poliuretanskih filmova na bazi hiperrazgranatog poliestra druge pseudo generacije (Boltron), 4,4¢-metilendifenildiizocijanata i dva različita iloksanska pretpolimera kao što su a, ω-dihidroksi- (etilenoksid-poli(dimetilsiloksan)-etilenoksid)(EO-PDMS-EO) i a,ω-dihidroksipro-pilpoli(dimetilsiloksan)(HP-PDMS), dvostepenom polimerizacijom u rastvoru. Uticaj vrste i sadržaja mekog segmenta na morfologiju, termomehanička i površinska svojstva sintetisanih poliuretana je proučavan pomoću mikroskopije atomske sila (AFM), rasipanja X-zraka pod malim uglovima (SAXS), skenirajuće elektronske mikroskopije (SEM), dinamičko mehaničke termičke analize (DMTA) i merenja količine apsorbovane vode. Nađeno je da primenjene tehnike potvrđuju postojanje morfologije mikrofaznog razdvajanja. Sintetisani poliuretani pokazivali su dve temperature ostakljivanja i jedan sekundarni relaksacioni proces. Rezultati su pokazali da poliuretani na bazi HP-PDMS su imali veći koeficijent hrapavosti, bolje mikrofazno razdvajanje i bolju otpornost prema vodi. Uzorci sintetisani sa nižim sadržajem PDMS-a su imali manju hidrofobnost, ali veću gustinu umrežavanja i bolja termomehanička svojstva

    Termička i morfološka svojstva termoplastičnih poliuretana na bazi poli(propilenoksida)-b-poli(dimetilsiloksana)-b-poli(propilenoksida)

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    In this paper was investigated the influence of the content of soft poly(propylene oxide)-b-poly(dimethylsiloxane)-b-polY(propylene oxide) (PPO-PDMS) segments on the thermal and morphological properties of new thermoplastic polyurethane with TGA, DSC and AFM analyses as well as deconvolution of FTIR spectra. The thermal stability of the copolymers increased, while the degree of crystallinity decreased with increasing content of PPO-PDMS segments. AFM and FTIR analysis confirmed that with decreasing of the content of PPO-PDMS segments the degree of microphase separation in copolymers increased.U ovom radu ispitan je uticaj sadržaja mekih poli(propilenoksida)-b-poli(dimetilsiloksana)-b-poli(propilenoksida) (PPO-PDMS) segmenta na termička i morfološka svojstva novih termoplastičnih poliuretana pomoću TGA, DSC i AFM analiza kao i dekonvolucijom FTIR spektara. Termička stabilnost kopolimera se povećavala, dok se stepen kristaliničnosti smanjivao sa povećanjem sadržaja PPO-PDMS segmenata. AFM i FTIR analize su potvrdile da se sa smanjivanjem sadržaja PPO-PDMS segmenata povećavao stepen mikrofaznog razdvajanja kopolimera

    Novel Tough and Transparent Ultra-Extensible Nanocomposite Elastomers Based on Poly(2-methoxyethylacrylate) and Their Switching between Plasto-Elasticity and Viscoelasticity

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    Novel stiff, tough, highly transparent and ultra-extensible self-assembled nanocomposite elastomers based on poly(2-methoxyethylacrylate) (polyMEA) were synthesized. The materials are physically crosslinked by small in-situ-formed silica nanospheres, sized 3–5 nm, which proved to be a very efficient macro-crosslinker in the self-assembled network architecture. Very high values of yield stress (2.3 MPa), tensile strength (3.0 MPa), and modulus (typically 10 MPa), were achieved in combination with ultra-extensibility: the stiffest sample was breaking at 1610% of elongation. Related nanocomposites doubly filled with nano-silica and clay nano-platelets were also prepared, which displayed interesting synergy effects of the fillers at some compositions. All the nanocomposites exhibit ‘plasto-elastic’ tensile behaviour in the ‘as prepared’ state: they display considerable energy absorption (and also ‘necking’ like plastics), but at the same time a large but not complete (50%) retraction of deformation. However, after the first large tensile deformation, the materials irreversibly switch to ‘real elastomeric’ tensile behaviour (with some creep). The initial ‘plasto-elastic’ stretching thus causes an internal rearrangement. The studied materials, which additionally are valuable due to their high transparency, could be of application interest as advanced structural materials in soft robotics, in implant technology, or in regenerative medicine. The presented study focuses on structure-property relationships, and on their effects on physical properties, especially on the complex tensile, elastic and viscoelastic behaviour of the polyMEA nanocomposites
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