The effects of the structure and molecular weight of the macrodiol on the properties polyurethane anionic adhesives

Polyurethane anionic adhesives were synthesized as waterborne polyurethane dispersions (PUDs) by modified dispersing procedure, using isophorone diisocyanate, dimethylol propionic acid, ethylenediamine as a chain extender and a range of soft segments with various macrodiols proportions. The soft segment was formed by replacing poly(propylene glycol) (PPG) as polyether polyol with polycarbonate diol (PCD), as polyester polyol. The effect of the macrodiols proportions of soft segment on the thermal properties of polyurethane films was measured by thermogravimetry analyses (TGA) and differential scanning calorimetry (DSC) methods. The infrared spectroscopy (FTIR) was used for evaluating the degree of phase separation. The results showed that phase separation between hard and soft segments of poly(ester-urethane) is more significant than of poly(ether-urethane). The phase separation degree of polyurethane dispersion significantly affected the glass transition temperature (T-g) and film properties. While the phase separation degree increased, T-g proportionally decreased, but the hardness and gloss of the dried films increased, as expected. However, thermal stability was influenced by the molecular weight of used polyols and chemical structure of the polyols, and it was described by the effect of oxygen content, and interaction between the soft and hard segment, and the soft segment composition. The soft segment can be achieved with a proper selection, in order to fine-tune the performance of waterborne polyurethane dispersion, considering certain practical application. (C) 2012 Elsevier Ltd. All rights reserved

The waterborne polyurethane dispersions based on polycarbonate diol: Effect of ionic content

Three water-based polyurethane dispersions (PUD) were synthesized by modified dispersing procedure using polycarbonate diol (PCD), isophorone diisocyanate (IPDI), dimethylolpropionic acid (DMPA), triethylamine (TEA) and ethylenediamine (EDA). The ionic group content in the polyurethane-ionomer structure was varied by changing the amount of the internal emulsifier, DMPA (4.5, 7.5 and 10 wt.% to the prepolymer weight). The expected structures of obtained materials were confirmed by FTIR spectroscopy. The effect of the DMPA content on the thermal properties of polyurethane films was measured by TGA, DTA, DSC and DMTA methods. Increased DMPA amounts result in the higher hard segment contents and in the increase of the weight loss corresponding to the degradation of the hard segments. The reduction of hard segment content led to the elevated temperature of decomposition and to the decrease of the glass transition temperature and thermoplasticity. The atomic force microscopy (AFM), results indicated that phase separation between hard and soft segment of PUD with higher DMPA content is more significant than of PUD with lower DMPA content. The physico-mechanical properties, such as hardness, adhesion test and gloss of the dried films were also determined considering the effect of DMPA content on coating properties. (C) 2012 Elsevier B.V. All rights reserved

Microstructure and properties of poly(urethane-siloxane)s based on hyperbranched polyester of the fourth pseudo generation

Poly(urethane-siloxane) networks based on hydroxyethoxy propyl terminated poly(dimethylsiloxane) (PDMS) as the soft segment and 4,4'-methylenediphenyl diisocyanate (MDI) and two hyperbranched polyesters with different core as the hard segments were characterized by swelling experiments, thermal analyses (DSC and TG), thermomechanical analysis (DMTA), X-ray scattering studies, SEM and AFM analyses, water contact angle and water absorption measurements, as well as surface free energy determination. From these studies, structure-property relationships were elucidated. Hyperbranched polyesters based on 2,2-bis(hydroxymethyl)propionic acid and ethoxylated pentaerythritol or di-trimethylolpropane as core (BH-40 and HBP-4) were used as crosslinkers for the samples of different series. Both series are composed of samples having different PDMS (i.e., soft segment) content. The crosslinking density and extent of hydrogen bonding showed an influence on the polyurethane (PU) properties. It was found that higher crosslinking density and better thermal stability of PUs based on BH-40 compared to HBP-4 based PUs are due to the less dense structure of BH-40. DMTA experiments revealed that the networks exhibit two glass transition temperatures, of the soft and hard segments, and one secondary relaxation process. The crosslinking density and extent of the microphase separation increased and thermomechanical properties were improved with decreasing content of PDMS. With increasing PDMS content, the surface of the polyurethane networks became more hydrophobic, the surface free energy decreased and thermal stability was improved. The obtained results revealed that synthesized PUs have good thermal and thermomechanical properties, which can be tailored for the potential use in the coating technology by changing the type of hyperbranched polyester or PDMS content

Influence of hematite nanorods on the mechanical properties of epoxy resin

The mechanical properties of nanocomposites obtained by incorporation of fairly uniform hematite nanorods (alpha-Fe2O3 NRs) into epoxy resin were studied as a function of the content of the inorganic phase. A thorough microstructural characterization of the alpha-Fe2O3 NRs and the nanocomposites was performed using transmission electron microscopy (TEM) and atomic force microscopy (AFM). The TEM measurements revealed rod-like morphology of the nanofiller with a uniform size distribution (8.5 nmx170 nm, diameterxlength). High-magnification TEM and AFM measurements indicated agglomeration of alpha-Fe2O3 NRs embedded in the epoxy resin. Stress at break, strain at break, elastic modulus and tensile toughness of the nanocomposites were compared with the data obtained for pure epoxy resin. Significant influence of nanofiller on the mechanical properties of epoxy resin, as well as on the glass transition temperature, could be noticed for samples with low contents of the inorganic phase (up to 1 wt. %)

Montmorillonite/poly(urethane-siloxane) nanocomposites: Morphological, thermal, mechanical and surface properties

The aim of this work was to prepare and characterize the series of segmented polyurethane nanocomposites (PUNC) modified with poly(dimethylsiloxane) and based on montmorillonite (Mt) as a nano-filler. alpha,omega-Dihydroxy-poly(propylene oxide)-b-poly(dimethylsiloxane)-b-poly(propylene oxide) macrodiol was used as the soft segment component, while 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD) were selected as the hard segment components. PUNC were synthesized with different ratio of hard/soft segments. PUNC were morphologically, structurally, thermally, mechanically and surface characterized by XRD, TEM, FTIR, AFM, TGA, DMTA, tensile test, XPS, contact angle, surface free energy (SFE) and water absorption measurements. Added Mt (1 wt%) was completely delaminated and well dispersed in the form of mixed exfoliated/intercalated layers in the polymer matrix, and that PUNC have more pronounced microphase separated morphology, higher thermal stability, superior mechanical features, enhanced surface properties, as well as outstanding hydrophobicity. Due to the improved features, developed polymers can be considered as candidates for materials with specific biomedical applications or as waterproof coatings

Studies of the Thermal and Mechanical Properties of Poly(urethane-siloxane)s Cross-Linked by Hyperbranched Polyesters

Polyurethane networks based on Boltorn hyperbranched polyesters (HBPs) of different pseudogenerations as cross-linkers, alpha,omega-dihydroxy(ethylene oxide-poly(dimethylsiloxane)-ethylene oxide) (EO-PDMS-EO) and 4,4'-methylenediphenyl diisocyanate were synthesized using a two-step polymerization reaction in solution. The influence of the pseudogeneration number of Boltorn HBPs on the thermomechanical and thermal properties and morphologies of polyurethane networks was investigated using FTIR, DMTA, TGA, hardness measurements, SEM, and SAXS. Synthesized polyurethanes showed higher cross-linking density and hardness and lower thermal stability with increasing pseudogeneration number of HBP. Samples with lower EO-PDMS-EO content exhibited slightly better thermal stability and higher hardness. All utilized characterization methods yielded consistent results and confirmed the existence of microphase separated morphology with the appearance of certain microphase mixing between segments as the pseudogeneration number of HBP increased. The obtained results revealed that the synthesized polyurethanes have good thermal and thermomechanical properties, which can be tailored by changing the pseudogeneration number of the HBP or the EO-PDMS-EO content

Preparation and Thermal Stability of Elastomers Based on Irregular Poly(urethane-isocyanurate) Networks

The objective of this study was to investigate the thermal stability of poly(urethane-isocyanurate) networks with increasing amount of dangling chains. In order to improve thermal stability of elastomeric materials, networks were prepared by adding some heat resistant isocyanurate rings as a junction points by catalytic cyclotrimerisation of telechelic diisocyanates. The thermal degradation kinetics of samples has been studied by means of high-resolution thermal analyzer SDT Q600 TA Instruments, under nitrogen atmosphere. The activation energy for the two step reactions of thermal decomposition of different species was calculated and compared

European energy security and the role of LNG

Thesis (M.A.)--Özyeğin University, Graduate School of Social Sciences, Department of Institute of Social Sciences Department of Public Law, 2017.İşbu çalışmanın amacı, hukuki açıdan Avrupa Birliği'nde enerji güvenliğinin nasıl algılandığı ve sıvılaştırılmış doğal gaz yani (dilimize geçtiği hali ile) LNG'nin bunu nasıl desteklediğinin açıklanmasıdır. Çalışma, enerjinin modern dünyadaki yerini, Avrupa'nın enerji güvenliği konseptini doğal gaz ve özellikle LNG kapsamında ne şekilde anladığı kapsamında değerlendirerek izah eder. Enerji güvenliğinin gerekliliği, hukuki bir bakış açısıyla ele alınmaktadır. Bahse konu konseptin hukuki açıdan anlaşılabilmesi, yalnızca hukukun tepkisiyle mümkündür ve Avrupa'nın enerji güvenliği konseptine bakış açısının analizine destek olmak için hukuki düzenlemeler ve somut vakalar örnek olarak kullanılmaktadır. Enerji güvenliğinin hukuki gelişiminin yanı sıra teknolojik gelişmeler de değerlendirilmekte ve bu açıdan LNG, enerji güvenliğine katkıları anlamında incelenmektedir. Çünkü, enerji olmaksızın ekonomi, hukuk olmaksızın enerji olmaz.The purpose of this work is to explain how energy security is perceived within the European Union and how liquified natural gas, in short LNG, supports it from legal aspect. This work states the place of energy in modern world by evaluating Europe's understanding of energy security concept under the scope of natural gas and especially LNG. The essentialness of energy security is discussed from a legal point of view. The aforesaid concept can only be understood by legal reactions and regulations and case studies are used as examples to support the analysis of Europe's energy security perception. Along with the legal development of energy security, technological development is also studied and LNG is discussed within the meaning of its reinforcement for the concept. Eventually, economy does not exist without energy; likewise energy does not exist without law

Structure-Property Correlation Study of Novel Poly(urethane-ester-siloxane) Networks

Novel poly(urethane-ester-siloxane) networks, based on hydroxypropyl terminated poly(dimethylsiloxane) (PDMS), 4,4'-methylenediphenyl diisocyanate, and hyperbranched polyesters (HBPs) of the second and third pseudogenerations, were synthesized by two-step polymerization. The effects of the PDMS content and pseudogeneration number of HBPs on the structural, thermomechanical, thermal, and surface properties of polyurethanes were investigated. Thermomechanical and thermal properties of polyurethanes and FTIR, SAXS, and SEM results indicated good microphase separated structure. SAXS data suggested that the difference in the HBP pseudogeneration number affects only the global properties of the structure and is much less pronounced than the dependence on the PDMS content, while local properties depend only on the PDMS content. Surface characterization of samples indicated the slightly amphiphilic nature of polyurethanes. The results revealed that the synthesized polyurethanes have good thermal, thermomechanical, and surface properties, which can be tuned and adjusted for coating application by changing the PDMS content or type of the HBP

Analysis of dynamic mechanical, thermal and surface properties of poly(urethane-ester-siloxane) networks based on hyperbranched polyester

Six polyurethane networks were synthesized from Boltorn (R) hyperbranched polyester of the second pseudo generation, alpha,omega-dihydroxy-(ethylene oxide-poly(dimethylsiloxane)-ethylene oxide) (EO-PDMS-EO) and 4,4-methylenediphenyl diisocyanate. The effect of the EO-PDMS-EO content on the properties of prepared polyurethanes was investigated by dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), swelling measurements, water contact angle and water absorption. Different techniques (FTIR peak deconvolution, DMTA and SEM) revealed that decrease of EO-PDMS-EO content promotes microphase separation in the synthesized polyurethanes. Samples synthesized with higher EO-PDMS-EO content have more hydrophobic surface and better waterproof performances, but lower crosslinking density. TGA results suggest that thermal stability of the synthesized polyurethane networks in nitrogen is significantly affected by the mutual influence of the crosslinking density and EO-PDMS-EO content. The results obtained in this work indicate that the synthesis of polyurethanes based on hyperbranched polyester and EO-PDMS-EO leads to the creation of networks with good thermal, thermomechanical and surface properties. (C) 2012 Elsevier B.V. All rights reserved