Emi Govorčin Bajsić

The influence of talc content on the thermal and mechanical properties of thermoplastic polyurethane/polypropylene blends:

The influence of different talc contents on the thermal and mechanical properties of thermoplastic polyurethane/polypropylene (TPU/PP) blends was investigated. The compatibility and crystallinity of TPU/PP and TPU/PP/T blends were determined by differential scanning calorimetry (DSC). The DSC results indicated that the addition of PP in TPU/PP blends increased glass transition temperature (T g), melting temperature (T m) and crystallinity (χ c). The addition of talc has decreased T m and χ c and increased T g and crystallization temperature (T c). The effect of talc content on T g, T m and χ c was insignificant, while T c content increased. The T g of nonfilled and talc-filled blends increased suggesting that the TPU and PP are partially compatible. Thermogravimetric analysis (TGA) showed improved thermal stability of all investigated nonfilled and talc-filled TPU/PP blends in the nitrogen atmosphere. In the air atmosphere only talc-filled TPU/PP 80/20 blends show a higher thermal stability, while thermal stability decreased for TPU/PP 50/50 and increased insignificantly for TPU/PP 20/80 blends. DSC and TGA results showed improved thermal properties of talc-filled TPU/PP blends when compared with nonfilled blends. The mechanical properties of talc-filled TPU/PP 50/50 and 20/80 blends improved in terms of tensile strength and Young’s modulus, while elongation of break decreased with the addition of talc and as the talc content increased.

Preparation and Characterization of Talc Filled Thermoplastic Polyurethane/Polypropylene Blends

The effect of the addition of talc on the morphology and thermal properties of blends of thermoplastic polyurethane (TPU) and polypropylene (PP) was investigated. The blends of TPU and PP are incompatible because of large differences in polarities between the nonpolar crystalline PP and polar TPU and high interfacial tensions. The interaction between TPU and PP can be improved by using talc as reinforcing filler. The morphology was observed by means of scanning electron microscopy (SEM). The thermal properties of the neat polymers and unfilled and talc filled TPU/PP blends were studied by using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The addition of talc in TPU/PP blends improved miscibility in all investigated TPU/T/PP blends. The DSC results for talc filled TPU/PP blends show that the degree of crystallinity increased, which is due to the nucleating effect induced by talc particles. The reason for the increased storage modulus of blends with the incorporation of talc is due to the improved interface between polymers and filler. According to TGA results, the addition of talc enhanced thermal stability. The homogeneity of the talc filled TPU/PP blends is better than unfilled TPU/PP blends.

Kinetic Parameters Estimation for Thermal Degradation of Polyurethane Elastomers

In this work, thermogravimetric analysis is used to determine the kinetic parameters of thermal degradation of polyurethane (PU) elastomers, based on poly(ether polyol) soft segment and aromatic-type diisocyanates. To determine the kinetic parameters of PU thermal decomposition, a nonlinear regression procedure is applied. Parameter estimation is obtained by minimizing the weighted quadratic output error functional with the modified Nelder-Mead simplex search algorithm. The confidence region of pre-exponential factor-activation energy are established both for the first and second steps of degradation. The effect of the soft segment molecular weight and hard segment content on the activation energy of the degradation process has been studied.

Dynamic mechanical study of thermoplastic polyurethane/polypropylene blends

Abstract Thermoplastic polyurethanes (TPU) are an important class of elastomers that found many novel and specialized applications where high mechanical and chemical performances are prerequisites. They are known for their good mechanical strength, wear and tear resistance, and low-temperature elasticity. The aim of this work is to study the viscoelastic behaviour of TPU, polypropylene (PP) and their blends using dynamic mechanical analysis. Blends of TPU+PP as well as samples of pure TPU and PP were prepared using a laboratory twin-screw extruder. Primary and secondary viscoelastic functions were determined. Primary viscoelastic functions, viz. storage modulus, loss modulus and loss tangent, were evaluated in the temperature range -100 to 250°C. The secondary viscoelastic functions creep, recovery and creep modulus were investigated in the creepfatigue regime at 25 - 65°C. A master curve at the reference temperature 25°C for the creep modulus of TPU, PP and TPU+PP blends was created by applying the time-temperature correspondence principle. The obtained results are discussed.

The influence of filler treatment on the mechanical properties and phase behavior of thermoplastic polyurethane/polypropylene blends

Thermoplastic polyurethane (TPU) and isotactic polypropylene (iPP) composites and their talc reinforced blends containing untreated and silane treated talc were investigated. The talc surface was modified with organosilane coupling agent in order to improve the polymer–filler interface interaction. TPU has been blended with iPP in a twin screw extruder and samples for investigation were prepared by injection moulding at different concentrations. The neat polymers, composites and blends were characterized with DMA, XRD, FTIR and tensile testing. The obtained results showed that mechanical properties of the talc filled TPU and iPP composites and TPU/iPP blends were improved with the addition of untreated and silane treated talc. The storage modulus of the TPU/iPP blends increased with the addition of untreated and silane treated talc, due to a stiffer interface which talc generated in the polymer matrix. The comparison among samples filled with untreated and silane treated talc filler showed that the polymer composites and TPU/iPP blends filled with silane treated talc displayed better mechanical properties. Silane addition improves the adhesion between the filler and the polymer matrix.

Polypropylene Blends with m-EPR Copolymers: Structure, Morphology and Thermal Properties

ABSTRACT The effects of different contents of two metallocene propylene-based m-EPR elastomers on structure, morphology, thermal, and dynamic mechanical properties of the isotactic polypropylene/m-EPR blends were investigated. The both m-EPR copolymers have been built in isotactic polypropylene matrix as amorphous phase. However, the nucleation effect at lowest addition (2.5 vol%) and the solidification effect along with increased m-EPR’s additions have caused changes of the crystallinity degree and the size of spherulites in the isotactic polypropylene matrix. Higher degree of miscibility/compatibility of the isotactic polypropylene/m-EPR2, with lower viscosity has been observed. Homogeneous dispersion of m-EPR particles as well as their radial distribution has been observed. GRAPHICAL ABSTRACT

Miscibility of Poly(Vinyl Chloride) with Poly(Ethylene Oxide) of Different Molecular Weights

In this work, five different techniques: dilute solution viscometry, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FT-IR), and scanning electronic microscopy (SEM) were employed in order to evaluate interactions of amorphous poly(vinyl chloride) (PVC) and semi- crystalline poly(ethylene oxide) (PEO) in solution and solid state. The results varied significantly from one experimental technique to another. The positive interactions between the investigated polymers were found over the whole composition range only in solution. However, in the solid state, by DSC and DMA analysis, the positive interactions were found only at elevated PVC content, while FT-IR and SEM analysis could not confirm interactions between the investigated polymers.

Effect of Silane Treated and Untreated Talc on the Properties of Thermoplastic Polyurethane/Polypropylene Blends

The effect of the silane treated talc on the mechanical and thermal properties of talc filled thermoplastic polyurethane/polypropylene blends (TPU/PP blends) was investigated. Thermoplastic polyurethane and polypropylene are partially miscible due to the lack of interfacial interaction between the nonpolar crystalline PP and polar TPU. Blends of TPU and PP with silane treated and untreated-talc were prepared using melt blending in a laboratory twin-screw extruder. Organosilane (3-glycidoxypropyl-trimetoxy silane coupling agent) was used to treat talc in order to improve the affinity between the filler and the TPU/PP blends. Dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and mechanical (tensile test) measurements were used to characterize the talc filled and silane treated talc filled composites and TPU/PP/talc blends. The addition of silane treated and untreated talc in TPU/PP blends improved miscibility in all investigated TPU/PP/talc blends. The silane treatment increases the storage modulus in all investigated TPU/PP/talc blends in comparison with that of the untreated TPU/PP/talc blends. The obtained DSC results show that the addition of silane treated talc increases the degree of crystallinity (χc) of TPU/PP/talc blends because of the improved adhesion between the polymer and the treated talc. Addition of silane treated talc improved the mechanical properties as compared to TPU/PP/talc blends without chemical modification of talc. The results of strength correlate to the values of the storage modulus and crystallinity of the investigated TPU/PP/talc blends.

The efficacy of electrospun polyurethane fibers with TiO2 in a real time weathering condition

This study focuses on the behavior of electrospun polyurethane fibers filled with nano, micro spheres and nanotube TiO2, thus nTiO2, mTiO2 or TiNT, under real time ultraviolet (UV) radiation. Analyses were conducted using scanning electron microscopy (SEM), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis and differential scanning calorimetry (DSC) techniques. Significant changes of thermoplastic polyurethane (TPU) + 0.5% nTiO2 and TPU + 0.5% mTiO2 fibers morphology, that is, agglomerated TiO2 particles, were observed on material surfaces due to TPU fiber degradation, also supported by FTIR spectra given as reduction in the peaks intensities after UV radiation, especially in the case of TPU + 0.5% nTiO2. Further, after UV radiation, the initial degradation temperature reduction of the hard segment for all materials was up to 40℃. A significant reduction in the final degradation temperature (from 397.8℃ to 274.1℃) was noticed for the mTiO2 filled fibers, suggesting their photocatalytic activity, while Tg was increased up to 20℃ for almost all fillers added to TPU, thus indicating lower molecular chain mobility upon UV radiation.

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

Otkriće, razvoj i uporaba materijala oduvijek je bila vrlo bitan čimbenik razvoja ljudske civilizacije. Živimo u svijetu brzog razvoja tehnologije, gdje je konstantno prisutna potreba za poboljšanjem postojećih i stvaranjem novih materijala koji nalaze svoju primjenu u proizvodnji. Poliuretan je jedinstven materijal, koji nudi elastičnost gume u kombinaciji s čvrstoćom i trajnosti metala.1,2,3 U odnosu na ostale polimere, poliuretani pokazuju veliku otpornost na udar i trošenje. Svoju primjenu nalaze u građevini i arhitekturi, strojarstvu, elektronici, tekstilnoj industriji, medicini, itd. Poliuretani (PU) su linearno segmentirani kopolimeri koji se sastoje od naizmjeničnih tvrdih (HS) i mekih segmenata (SS).4,5 Tvrdi segment sastoji se od diizocijanata i kratkih molekula produživača lanca, kao što su dioli ili diamini koji su kruti i visokopolarni. Zbog prisutnosti vodikovih veza u tvrdom segmentu dolazi do međumolekulnih interakcija između skupina uretan-urea. Vodikove veze unutar tvrdih segmenata u PU-u djeluju kao ojačanje za slabu matricu mekog segmenta. S druge strane, meki segmenti su dugolančani dioli ili polioli, koji su fleksibilni i slabo polarni. Molekule poliuretana izgrađene su od segmenata blok-kopolimera sastavljenih od relativno dugih i savitljivih polieterskih ili poliesterskih segmenata koji predstavljaju meke segmente, koji su kovalentno povezani sa segmentima uretanskih blokova i predstavljaju tvrde segmente. U PU-u dolazi do odvajanja faza zbog termodinamičke nemješljivosti između tvrdog i mekog segmenta.6,7 Termoplastični polikarbonat (PC) je amorfan polimer, koji se često upotrebljava kao polimerni materijal, zbog njegove izvanredne kombinacije uporabnih svojstava i niske cijene, kao i zbog njegove strukture koja se jednostavno modificira. Odlike PC-a su velika krutost, čvrstoća i žilavost te svoju primjenu nalazi u arhitekturi (staklo, zaštita od korozije, podovi), medicini (medicinska oprema, leće, zubne ispune), autoindustriji (auto-prevlake, dijelovi interijera), elektronici (CD, DVD, mobilna kućišta) i mnogim drugim područjima. Važno svojstvo na kojem se temelji primjena u medicini je biokompatibilnost, što znači da je PC osnovni, esencijalni element za dijelove koji su u izravnom i neizravnom kontaktu s pacijentom. Međutim primjena polikarbonata (PC) u mješavinama s drugim polimerima ograničena je zbog visoke temperature prerade PC-a, na kojima može doći do njihove toplinske razgradnje.8,9 Ti problemi mogu se djelomično riješiti miješanjem amorfnih i termoplastičnih materijala, kao što su polikarbonat i termoplastični poliuretan, pri čemu se dobivaju mješavine dobrih mehaničkih, toplinskih i reoloških svojstava.10,11