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Soft Segments (soft + segment)

Distribution by Scientific Domains

Polymers and Materials Science	90%
Chemistry	10%

Selected Abstracts

Structure and properties of cross-linked polyurethane copolymers

ADVANCES IN POLYMER TECHNOLOGY, Issue 3 2009
S. Oprea
Abstract Polyurethane elastomers based on polyester diols and aromatic or aliphatic diisocyanates can be used as vibration dampers and isolation materials. Two series of cross-linked polyurethanes with various hard segment structures and different amounts were prepared and thermomechanical properties of these materials were studied. Cross-linked polyurethane copolymers composed of poly(ethylene adipate)diol as soft segment and 4,4,-methylenebis(phenylisocyanate), 1,6-hexamethylene diisocyanate, and diols glycerin, 1,4-butanediol, and 1,6-hexanediol as hard segments were synthesized by a two-step process. The networks have been prepared by end-linking a mixture of the bifunctional precursor chains with trifunctional cross-linkers at off-stoichiometric ratios. The results show that the cross-link and the polyurethane hard segment interaction play a special role in the interconnected chain density and its magnitude is revealed by the mechanical properties. Of most importance, maximum stress, tensile modulus, and elongation at break increased significantly at the 22 wt % composition of hard segment content. Interchain cross-linking improves thermal stability, which was measured by thermogravimetric analysis and differential scanning calorimetry. Cross-linked polyurethane behaves as an elastomer and is useful for shock, noise, and vibration control. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:165,172, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20155 [source]

Structural and photooxidation studies of poly(styrene oxide) prepared with Maghnite-H+ as cationic catalyst

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008
Aïcha Hachemaoui
Abstract The nature of irregularities and end-groups in poly(styrene oxide) samples prepared using Maghnite-H+ as a cationic catalyst were studied by 1H- and 13C-NMR at 200 MHz. Head-to-head (H-H) and tail-to-tail (T-T) irregularities are detected in all the samples studied. Secondary hydroxyl terminal groups are identified in polymers prepared with Maghnite-H+. Poly(styrene oxide) was found to undergo chain scission by aging at 25°C. It was confirmed that oxidation of this type of polymers results from the important sensitivity of the polyether soft segment to oxidative degradation. For this reason, the scissions due to the oxidation of the material lead to notable quantities of low molecular weight photoproducts. Among the various structures produced by the oxidative degradation process, benzoate and secondary hydroxyl groups are identified by MALDI-TOF-MS. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Poly(ester urethane)s with polycaprolactone soft segments: A morphological study

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2002
Juliana Kloss
Abstract Two series of poly(ester urethane)s were prepared, containing polycaprolactone (PCL) as the soft segment with molecular weights of 530 and 2000. In each series, the soft-segment/hard-segment ratio was varied, and the morphological changes were monitored with differential scanning calorimetry, dynamic mechanical thermal analysis, wide-angle X-ray scattering, and scanning electron microscopy techniques. The polyurethanes with longer PCL segments retained their crystallinity, whereas those with shorter PCL segments did not. A morphological model is proposed, in which a continuous PCL-rich matrix contains both PCL crystallites and domains of urethane hard segments. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4117,4130, 2002 [source]

Solid polymer electrolytes III: Preparation, characterization, and ionic conductivity of new gelled polymer electrolytes based on segmented, perfluoropolyether-modified polyurethane

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2002
Chi-Chang Chen
Abstract New segmented polyurethanes with perfluoropolyether (PFPE) and poly(ethylene oxide) blocks were synthesized from a fluorinated macrodiol mixed with poly(ethylene glycol) (PEG) in different ratios as a soft segment, 2,4-toluene diisocyanate as a hard segment, and ethylene glycol as a chain extender. Fourier transform infrared, NMR, and thermal analysis [differential scanning calorimetry and thermogravimetric analysis (TGA)] were used to characterize the structures of these copolymers. The copolymer films were immersed in a liquid electrolyte (1 M LiClO4/propylene carbonate) to form gel-type electrolytes. The ionic conductivities of these polymer electrolytes were investigated through changes in the copolymer composition and content of the liquid electrolyte. The relative molar ratio of PFPE and PEG in the copolymer played an important role in the conductivity and the capacity to retain the liquid electrolyte solution. The copolymer with a 50/50 PFPE/PEG ratio, having the lowest decomposition temperature shown by TGA, exhibited the highest ionic conductivity and lowest activation energy for ion transportation. The conductivities of these systems were about 10,3 S cm,1 at room temperature and 10,2 S cm,1 at 70 °C; the films immersed in the liquid electrolyte with an increase of 70 wt % were homogenous with good mechanical properties. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 486,495, 2002; DOI 10.1002/pola.10119 [source]

Composites of carbon nanofibers and thermoplastic polyurethanes with shape-memory properties prepared by chaotic mixing

POLYMER ENGINEERING & SCIENCE, Issue 10 2009
Guillermo A. Jimenez
Composites of carbon nanofibers (CNFs), oxidized carbon nanofibers (ox-CNFs), and shape-memory thermoplastic polyurethane (TPU) were prepared in a chaotic mixer and their shape-memory properties evaluated. The polymer was synthesized from 4,4,-diphenylmethane diisocyanate, 1,4-butanediol chain extender, and semicrystalline poly(,-caprolactone) diol soft segments. The shape-memory action was triggered by both conductive and resistive heating. It was found that soft segment crystallinity and mechanical reinforcement by nanofibers produced competing effects on shape-memory properties. A large reduction in soft segment crystallinity in the presence of CNF and stronger mechanical reinforcement by well-dispersed ox-CNF determined the shape-memory properties of the respective composites. It was found that the maximum shape recovery force, respectively, 3 and 4 MPa, was obtained in the cases of 5 and 1 wt% CNF and ox-CNF, respectively, compared with ,1.8 MPa for unfilled TPU. The degree of soft segment and hard segment phase separation and thermal stability of the composites were analyzed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers. [source]

Preparation and properties of transparent thermoplastic segmented polyurethanes derived from different polyols

POLYMER ENGINEERING & SCIENCE, Issue 5 2007
Da-Kong Lee
Various segmented polyurethanes of different soft segment structure with hard segment content of about 50 wt% were prepared from 4,4,-diphenylmethane diisocyanate (MDI), 1,4-butanediol and different polyols with a Mn of 2000 by a one-shot, hand-cast bulk polymerization method. The polyols used were a poly(tetramethylene ether)glycol, a poly(tetramethylene adipate)glycol, a polycaprolactonediol and two polycarbonatediols. The segmented polyurethanes were characterized by gel permeation chromatography (GPC), UV-visible spectrometry, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X-ray diffraction, and their tensile properties and Shore A hardness were determined. The DSC and DMA data indicate that the miscibility between the soft segments and the hard segments of the segmented polyurethanes is dependent on the type of the soft segment, and follows the order: polycarbonate segments > polyester segments > polyether segments. The miscibility between the soft segments and the hard segments plays an important role in determining the transparency of the segmented polyurethanes. As the miscibility increases, the transparency of the segmented polyurethanes increases accordingly. The segmented polyurethanes exhibit high elongation and show ductile behavior. The tensile properties are also affected by the type of the soft segment to some extent. POLYM. ENG. SCI., 47:695,701, 2007. © 2007 Society of Plastics Engineers. [source]

Preparation and characterization of polyurethane,gold nanocomposites prepared using encapsulated gold nanoparticles

POLYMER INTERNATIONAL, Issue 7 2010
Chao-Ching Chang
Abstract Gold nanoparticles (GNPs) have been widely studied due to their unique properties. Although many research groups have developed the synthesis of GNPs using various polymers as stabilizing or reducing agents, the effects of GNPs on the structures and properties of polymer matrices have been less reported. We propose a new design for the preparation of polyurethane,gold (PU,Au) nanocomposites. 11-Mercapto-1-undecanol-coated GNPs acted as the chain extenders and reacted with isocyanates to form covalent bonds between PU and GNPs. PU,Au nanocomposites were successfully synthesized, and the effects of multifunctional GNPs on the structures, morphology and properties of poly(ester urethane) were investigated. Scanning electron microscopy images suggested the GNPs can be dispersed uniformly in the PU matrix. Maltese-cross of spherical crystals was observed in the PU,Au nanocomposites, and the size of the crystals decreased with an increase in gold content. As the gold content increased, the thermal decomposition temperature and the temperature of the maximum decomposition rate increased. The glass transition temperature, crystal melting temperature and melting enthalpy of the soft segment also increased progressively. The results showed that multifunctional GNPs concentrated hard segments and resulted in an increase of heterogeneous nucleation, phase separation and elasticity. Copyright © 2010 Society of Chemical Industry [source]

Synthesis and properties of room temperature curable trimethoxysilane-terminated polyurethane and their dispersions

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 8 2007
Sankaraiah Subramani
Abstract The purpose of this research is to study the synthesis and characterization of stable aqueous dispersions of externally chain extended polyurethane/urea compositions terminated by hydrolyzable or hydrolyzed trialkoxysilane groups incorporated through secondary amino groups. These dispersions with excellent storage stability are substantially free from organic solvents which cure to water and solvent resistant, tough, scratch resistant, preferably light stable (non-yellowing) silylated polyurethane (SPU) films. The films were characterized by FT-IR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile strength and water contact angle measurements, nanoindentation, gel content, water and xylene swellability tests. The properties of the films were discussed and correlated in detail by changing length of soft segment, diisocyanates, NCO/OH ratio and chain extender, ethylenediamine (EDA). From the results, it was found that the particle size and viscosity are lower whereas the gel content and thermal stability are higher for SPUs. Modulus, hardness and tensile properties of SPU films are superior compared to EDA-PU film. Higher water contact angle and residual weight percentage of SPU films confirm silylation of PU by [3-(phenylamino)propyl]trimethoxysilane (PAPTMS). Increase in NCO/OH ratios consumes more quantity of PAPTMS which makes PU with superior mechanical properties. Higher PAPTMS content in SPU results in effective crosslinking of the functional silanol groups formed by hydrolysis reaction of trimethoxysilane groups. Overall, SPUs synthesized at 1.4 NCO/OH ratio using Poly-(oxytetramethylene)glycol (PTMG)-2000 and isophorone diisocyanate (or) toluene-2,4-diisocyanate have excellent properties compared to SPUs prepared using PTMG-1000 and at 1.2 and 1.6 NCO/OH ratios. SPUs prepared at 1.6 NCO/OH ratio are brittle due to higher crosslinking density. In addition, the crosslinking density of the films can be modified through silane end-group modification to produce SPUs with a wide range of physical properties. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Novel Segmented Thermoplastic Polyurethanes Elastomers Based on Tetrahydrofuran Ethylene Oxide Copolyethers as High Energetic Propellant Binders

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 1 2003
Fu-Tai Chen
Abstract Novel thermoplastic polyurethane (TPU) elastomers based on copolyether (tetrahydrofuran ethylene oxide) as soft segments, isophorone diisocyanate and 1,4-butanediol as hard segments were synthesized for the purpose of using as propellant binders. In order to increase the miscibility of thermoplastic polyurethane elastomers with nitrate ester, polyethylene glycol (PEG) is incorporated in the co-polyether (tetrahydrofuran ethylene oxide) as soft segment. When the molecular weight and content of polyethylene glycol are controlled to 4000 and 6% of soft segments, respectively, the properties of thermoplastic polyurethane elastomers are most perfect. If plasticizing ratio of nitrate ester to thermoplastic polyurethane elastomers exceeds 4 no crystallinities are determined at room temperature. The propellant samples were prepared by a conventional absorption-rolling extrusion process and the mechanical and combustion properties evaluated afterwards. The maximum impulse reaches up to 265,270 s which is a little bit higher than that of a HTPB propellant. The measured results reveal a promising TPE propellant candidate which shows good processing temperature (<393,K) and excellent mechanical properties. An attracting feature which can be pointed out is that the burning rate pressure exponent reaches as low as 0.36 without the addition of burning rate catalysts. This enables an easy control of propellant combustion. [source]

Influence of TiO2 Nanoparticles Incorporated into Elastomeric Polyesters on their Biocompatibility In Vitro and In Vivo

ADVANCED ENGINEERING MATERIALS, Issue 11 2009
Miroslawa El-Fray
Abstract Fibroblasts proliferation and apoptosis as well as tissue response after implantation of elastomers containing nanocrystalline TiO2 were investigated in the present in vitro and in vivo study. Materials investigated were soft poly(aliphatic/aromatic-ester) multiblock thermoplastic elastomers with poly(ethylene terephthalate) (PET) hard segments and dimerized linoleic acid (DLA) soft segments, respectively, containing 0.2,wt% TiO2 nanoparticles. An investigation of the influence of TiO2 nanoparticles incorporated into polymeric material on in vitro biocompatibility revealed enhanced cell proliferation and diminished number of necrotic and apoptotic cells as compared to nanoparticles-free polymer. Implantation tests indicated that the observed tissue changes were similar to those observed with medical-grade silicone elastomer, no evidence of contact necrosis being observed. The unchanged morphology of rat liver hepatocytes and the lack of parenchymal necrosis also indicated that exposure to the material containing TiO2 nanoparticles, did not cause any cytotoxic reactions. The present study, thus, showed that elastomeric polyester containing TiO2 nanoparticles are interesting biomimetic constructs for improved tissue regeneration. [source]

Effects of soft segments on the surface properties of polydimethylsiloxane waterborne polyurethane prepolymer blends and treated nylon fabrics

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
Meng-Shung Yen
Abstract This study of waterborne polyurethane prepolymer blends was done to investigate the effects of different types of soft segments on the dispersion properties and other properties of treated nylon fabrics. The particle size of the dispersion increased, the surface tension of the dispersion decreased, and the contact angle of the nylon fabric with the dispersion decreased when the blending amount of the polydimethylsiloxane polyurethane prepolymer increased. The add-on of ether-type polyurethane increased rapidly when the ether-type polyurethane was blended with a small amount of the polydimethylsiloxane polyurethane prepolymer, whereas the add-on of the ether-type polyurethane reached a maximum at a blending content of 10%. The add-on of the ester-type polyurethane prepolymer constantly decreased with increasing blending amount of the polydimethylsiloxane polyurethane prepolymer. The vertical wicking height of the treated nylon fabrics decreased slightly when the treating agent contained a small amount of the polydimethylsiloxane polyurethane prepolymer. For the treated nylon fabrics with blended prepolymers, the drying time was faster than for the untreated fabric, and the moisture ratio reached about 10% in 15 min © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Studies on thermoplastic polyurethanes based on new diphenylethane-derivative diols.

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008

Abstract Two series of poly(ether urethane)s and one series of poly(ester urethane)s were synthesized, containing, respectively, poly(oxytetramethylene) diol (PTMO) of Mn = 1000 and 2000 and poly(,-caprolactone) diol of Mn = 2000 as soft segments. In each series the same hard segment, i.e., 4,4,-(ethane-1,2-diyl)bis(benzenethiohexanol)/hexane-1,6-diyl diisocyanate, with different content (, 14,72 wt %) was used. The polymers were prepared by a one-step melt polymerization in the presence of dibutyltin dilaurate as a catalyst, at the molar ratio of NCO/OH = 1 (in the case of the polymers from PTMO of Mn = 1000 also at 1.05). For all polymers structures (by FTIR and X-ray diffraction analysis) and physicochemical, thermal (by differential scanning calorimetry and thermogravimetric analysis), and tensile properties as well as Shore A/D hardness were determined. The resulting polymers were thermoplastic materials with partially crystalline structures (except the polymer with the highest content of PTMO of Mn = 2000). It was found that the poly(ether urethane)s showed lower crystallinity, glass-transition temperature (Tg), and hardness as well as better thermal stability than the poly(ester urethane)s. Poly(ether urethane)s also exhibited higher tensile strength (up to 23.5 MPa vs. 20.3 MPa) and elongation at break (up to , 1950% vs. 1200%) in comparison with the corresponding poly(ester urethane)s. Among the poly(ether urethane)s an increase in soft-segment length was accompanied by an increase in thermal stability, tensile strength, and elongation at break, as well as a decrease in Tg, crystallinity, and hardness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Moisture-cured polyurethane/polysiloxane copolymers: Effects of the structure of polyester diol and NCO/OH ratio

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008
Hongmei Jiang
Abstract Moisture-cured polyurethane is one of the commercially important polymers, which is widely used in sealants, coatings, and reactive hot-melt adhesives. A series of moisture-cured polyurethane/polysiloxane (PUSR) copolymers were successfully prepared using a two-step solution polymerization procedure. Both amine-terminated polysiloxane (PDMS) and polyester diol were together used as mixed soft segments to react with 4,4,-diphenlymethane diisocyanate (MDI), and the alkoxysilane was used as end-capping agents. The effects of structure variation of building blocks such as the polyester diol structure and NCO/OH ratio on the properties and morphology of PUSR copolymers were studied. The tensile properties, dielectric behavior, thermal stability, surface, and water-repellency properties were investigated. The results showed that the properties and morphology of PUSR copolymers were greatly affected by the variations in molecular architecture. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Melt spun thermoresponsive shape memory fibers based on polyurethanes: Effect of drawing and heat-setting on fiber morphology and properties

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007
Jasmeet Kaursoin
Abstract Thermoresponsive shape memory (SMP) fibers were prepared by melt spinning from a polyester polyol-based polyurethane shape memory polymer (SMP) and were subjected to different postspinning operations to modify their structure. The effect of drawing and heat-setting operations on the shape memory behavior, mechanical properties, and structure of the fibers was studied. In contrast to the as-spun fibers, which were found to show low stress built up on straining to temporary shape and incomplete recovery to the permanent shape, the drawn and heat-set fibers showed significantly higher stresses and complete recovery. The fibers drawn at a DR of 3.0 and heat-set at 100°C gave stress values that were about 10 times higher than the as-spun fibers at the same strain and showed complete recovery on repeated cycling. This improvement was likely due to the transformation brought about in the morphology of the permanent shape of the SMP fibers from randomly oriented weakly linked regions of hard and soft segments to the well-segregated, oriented and strongly H-bonded regions of hard-segments. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2172,2182, 2007 [source]

Synthesis and characterization of polyurethane,urea nanoparticles containing methylenedi- p -phenyl diisocyanate and isophorone diisocyanate

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2004
In Woo Cheong
Abstract Water-based polyurethane,urea (WPUU) nanoparticles containing 4,4,-methylenedi- p -phenyl diisocyanate (MDI) and isophorone diisocyanate (IPDI) were synthesized by a stepwise prepolymer mixing process, that is, the consecutive formation of hydroxyl-terminated and isocyanate-terminated polyurethane prepolymers. The reaction behavior, chemical structure, and consequent morphology of the polyurethane prepolymers and WPUU were investigated with Fourier transform infrared (FTIR), gel permeation chromatography, and NMR techniques with MDI concentrations ranging from 0 (pure IPDI) to 50% with respect to the total moles of isocyanate. Wide-angle X-ray diffraction and differential scanning calorimetry patterns showed that the crystallinity of WPUU, which mostly originated from crystallizable poly(tetramethylene adipate) polyol, was significantly affected by the MDI content. Both the crystallinity and melting temperature of WPUU decreased as the MDI content increased. Deconvoluted relative peak areas of the carbonyl region in the FTIR spectrum revealed that the effect of hydrogen bonding among the hard segments became favorable as the MDI content increased, whereas the hydrogen bonding of the soft segments significantly decreased. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4353,4369, 2004 [source]

Poly(ester urethane)s with polycaprolactone soft segments: A morphological study

Synthesis and properties of segmented main-chain liquid-crystalline polyurethanes with a high aspect ratio mesogenic diol as a chain extender

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2002
T. Padmavathy
Abstract Main-chain liquid-crystalline polyurethanes were synthesized based on a high aspect ratio mesogenic diol (4-{[4-(6-hydroxyhexyloxy)-phenylimino]-methyl}-benzoic acid 4-{[4-(6-hydroxyhexyloxy)-phenylimino]-methyl}-phenyl ester) as a chain extender; polycaprolactone (PCL) diol soft segments of different number-average molecular weights (530, 1250, or 2000); and different diisocyanates, including 1,4-hexamethylene diisocyanate (HMDI), 4,4,-methylene bis(cyclohexyl isocyanate) (H12MDI), and 4,4,-methylene bis(phenyl isocyanate) (MDI). The structure of the polymers was confirmed with Fourier transform infrared spectroscopy, and differential scanning calorimetry and polarizing microscopy measurements were carried out to examine the liquid-crystalline and thermal properties of the polyurethanes, respectively. The mesogenic diol was partially replaced with 20,50 mol % PCL. A 20 mol % mesogen content was sufficient to impart a liquid crystalline property to all the polymers. The partial replacement of the mesogenic diol with PCL of various molecular weights, as well as the various diisocyanates, influenced the phase transitions and the occurrence of mesophase textures. Characteristic liquid-crystalline textures were observed when a sufficient content of the mesogenic diol was present. Depending on the flexible spacer length and the mesogenic content, grained and threadlike textures were obtained for the HMDI and H12MDI series polymers, whereas the polyurethanes prepared from MDI showed only grained textures for all the compositions. The polymers formed brittle films and could not be subjected to tensile tests. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1527,1538, 2002 [source]

Enhanced Biocompatibility in Biostable Poly(carbonate)urethane

MACROMOLECULAR BIOSCIENCE, Issue 4 2004
Shan-hui Hsu
Abstract Summary: In this work, we synthesized two MDI-based polyurethanes, including a poly(ether)urethane (PEU) and a poly(carbonate)urethane (PCU), by using different soft segments, poly(tetramethylene oxide) and poly(hexyl, ethyl)carbonate diol (,,,2,000). We demonstrated that, in addition to the enhanced biostability of PCU over PEU, the biological performances of PCU in vitro were also improved in general. These included, better cellular attachment and proliferation, less platelet activation, as well as reduced monocyte activation. The unusual wide-ranging enhancement in biocompatibility for PCU was believed to be related to the larger micro-phase separation in PCU (,25 nm) that caused distinct protein adsorption on the surface. The total number of adherent monocytes (nonactivated and activated) on the bare sample surfaces, albumin pre-adsorbed sample surfaces, and fibrinogen pre-adsorbed sample surfaces. [source]

Segmented Block Copolymers with Monodisperse Aramide End-Segments

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2008
Araichimani Arun
Abstract Segmented block copolymers were synthesized using monodisperse diaramide (T,T) as hard segments and PTMO with a molecular weight of 2,900 g,·,mol,1 as soft segments. The aramide: PTMO segment ratio was increased from 1:1 to 2:1 thereby changing the structure from a high molecular weight multi-block copolymer to a low molecular weight end-block copolymer. The thermal and thermal-mechanical properties were studied by DSC and DMA. Also studied were the tensile and the elastic properties as well as the melt rheological behavior as a function of frequency. The crystallinity of aramide in the end-block copolymers was found to be higher than in the multi-block copolymer. [source]

Effect of Biodegradable Epoxidized Castor Oil on Physicochemical and Mechanical Properties of Epoxy Resins

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 15 2004
Soo-Jin Park
Abstract Summary: Biobased epoxy materials were prepared from diglycidyl ether of bisphenol A (DGEBA) and epoxidized castor oil (ECO) initiated by a latent thermal catalyst. The physicochemical and mechanical interfacial properties of the DGEBA/ECO blends were investigated. As a result, the thermal stability of the cured epoxy blends showed a maximum value in the presence of 10 wt.-% ECO content, which was attributed to the excellent network structure in the DGEBA/ECO blends. The storage modulus and glass transition temperature of the blends were lower than those of neat epoxy resins. The mechanical interfacial properties of the cured specimens were significantly increased with increasing the ECO content. This could be interpreted in terms of the addition of larger soft segments of ECO into the epoxy resins and thus reducing the crosslinking density of the epoxy network, which results in increasing toughness in the blends. KIC values of the DGEBA/ECO blends as a function of ECO content. [source]

Deformation Behavior of PET, PBT and PBT-Based Thermoplastic Elastomers as Revealed by SAXS from Synchrotron

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2003
Norbert Stribeck
Abstract The present paper discloses the changes in the nanostructure as revealed by small-angle X-ray scattering (SAXS) of synchrotron radiation of anisotropic semi-crystalline samples of polyester and poly(ether ester) type differing in their chemical composition, while subjected to controlled progressive elongation. From the group of polyesters poly(ethylene terephthalate) (PET), and poly(butylene terephthalate) (PBT) were selected. Two PBT-based commercial poly(ether ester)s were also studied differing in the molecular weight of their soft segments (poly(tetramethylene glycol), PTMG) being 1000 and 2000, respectively. A blend of PBT and EM550 (40/60 by wt.) was also characterized. All materials underwent the same sample preparation process resulting in highly oriented "bristles" of 1 mm diameter. It was found that ,b, the elongation at break, strongly depends on the flexibility of the glycol residues of the materials studied , ranging from ,b,=,8% for PET that contains ethylene glycol residues, through ,b,=,18% for PBT including the more flexible tetramethylene glycol (TMG) up to ,b,=,510% for the PEE containing the longest PTMG moieties. During straining the relationship between the external elongation , and the changes in the long spacing L was determined. After relaxation from each deformation step the relationship between the tensile set ,r and the long period L was also followed and discussed. Such analysis led to a model describing the nanostructure evolution during the deformation-relaxation cycle that finally was verified and refined utilizing the multidimensional chord distribution function computed from the anisotropic SAXS patterns. 2D SAXS patterns (pseudo color) of bristles of PET (PBT), respectively, cold drawn, ,,=,3.5 (,,=,2.3) and annealed with fixed ends for 6 h at 240,°C (180,°C), recorded at room temperature at a forced tensile deformation , or tensile set (residual elongation) ,r in percent. [source]

Novel Dynamic Viscoelastic Measurements of Polyurethane Copolymer Melts and Their Implication to Tack Results

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2006
Sonia Florez
Abstract Summary: A series of polyurethane multiblock copolymers with different proportions of hard segments (urethane) to soft segments (polyadipate of hexane-1,6-diol), are investigated. Dynamic viscoelastic functions of homogeneous melts in the terminal zone are determined. For the first time, entanglement modulus values of such copolymers are reported, which allows estimation of the packing length. These parameters do not vary with changing the hard-to-soft segment ratio, a result that is explained by a compensating effect of the chain architecture. For samples of similar molecular weight, the relaxation time of the terminal zone increases as the hard-to-soft segment ratio augments. The adhesives obtained from PUR solutions show a correlation between the elastic modulus and the debonding stress-strain curves in tack experiments. The storage modulus of the adhesives as a function of frequency at 70,°C. [source]

Conformational aspects of segmented poly(ester-urethanes)

MACROMOLECULAR SYMPOSIA, Issue 1 2003
S. Ioan
Abstract Segmented poly(ester-urethanes) containing hard and soft segments, were obtained from aromatic diisocyanates with thiodiglycol or diethylene glycol as chain extenders, and poly(ethylene glycol)adipate usig a multistep polyaddition process. Transition temperatures by differential scanning calorimetry and thermo-optical analysis were employed to characterize polyurethane materials. Changes in the conformation of these polyurethanes were analyzed also, by viscometer measurements in N,N-dimethyl-formamide. The obtained data revealed that the thermal curves are influenced by the soft and hard segment structures in the temperature range studied. [source]

Composites of carbon nanofibers and thermoplastic polyurethanes with shape-memory properties prepared by chaotic mixing

Preparation and properties of transparent thermoplastic segmented polyurethanes derived from different polyols

Relationship between segment structures and elastic properties of segmented poly(urethane-urea) elastic fibers

POLYMER ENGINEERING & SCIENCE, Issue 11 2003
Nori Yoshihara
Studies on segmented poly(urethane-urea) (SPUU) elastic fibers having various segment structures were done in terms of elastic recovery and stress-strain relationship (S-S). Three kinds of segment structures were used: 1) the same composition having different sequences of segment units, 2) the same length of soft segments having different molecular weights of polyol, and 3) different segment structures having almost the same stress at 350% elongation. The SPUU elastic fibers having higher sequence numbers of both soft and hard segment units, that is, greater block structures, show better elastic recovery properties, especially delayed elastic recovery. The SPUU elastic fibers showing better elastic recovery take an optimum value for the number-average molecular weight (Mn) of soft segments jointed with urethane bonds. Here the optimum Mn depends on the molecular weight of polytetramethyleneglycol (PTMG) as a starting material. The hysteresis loss in S-S for the pre-elongation decreases with an increase of Mn of PTMG. The SPUU elastic fibers having greater block structures show lower stress with lower 2C1 and 2C1 + 2C2 of Mooney-Rivilin plot constants for elastic fibers having the same composition. This indicates a lower density of crosslinks for finite deformation. An increase of the urea bonds or the molar ratio of urea bond to urethane bond raises the stress. It is found that the polymerization process, as well as composition, is important for design structures of SPUU elastic fibers. [source]

Copolymers based on poly(butylene terephthalate) and polycaprolactone- block -polydimethylsiloxane- block -polycaprolactone

POLYMER INTERNATIONAL, Issue 6 2010
Vesna V Anti
Abstract A series of novel thermoplastic elastomers, based on poly(butylene terephthalate) (PBT) and polycaprolactone- block -polydimethylsiloxane- block -polycaprolactone (PCL-PDMS-PCL), with various mass fractions, were synthesized through melt polycondensation. In the synthesis of the poly(ester-siloxane)s, the PCL blocks served as a compatibilizer for the non-polar PDMS blocks and the polar comonomers dimethyl terephthalate and 1,4-butanediol. The introduction of PCL-PDMS-PCL soft segments resulted in an improvement of the miscibility of the reaction mixture and therefore in higher molecular weight polymers. The content of hard PBT segments in the polymer chains was varied from 10 to 80 mass%. The degree of crystallinity of the poly(ester-siloxane)s was determined using differential scanning calorimetry and wide-angle X-ray scattering. The introduction of PCL-PDMS-PCL soft segments into the polymer main chains reduced the crystallinity of the hard segments and altered related properties such as melting temperature and storage modulus, and also modified the surface properties. The thermal stability of the poly(ester-siloxane)s was higher than that of the PBT homopolymer. The inclusion of the siloxane prepolymer with terminal PCL into the macromolecular chains increased the molecular weight of the copolymers, the homogeneity of the samples in terms of composition and structure and the thermal stability. It also resulted in mechanical properties which could be tailored. Copyright © 2010 Society of Chemical Industry [source]

Fireproofing of polyurethane elastomers by reactive organophosphonates

POLYMER INTERNATIONAL, Issue 1 2003
Wassef El Khatib
Abstract Polyurethane elastomers were prepared with hydroxytelechelic polybutadiene (HTPB) as polyol, modified 4,4,-diphenylmethane diisocyanate (modified MDI) as liquid polyisocyanate, and phosphonate diols as chain extenders and flame retardant compounds. These phosphonate diols were synthesized by radical thiol,ene addition of allyl or vinyl dialkyl phosphonate to 3-mercapto-1,2-propanediol. For various percentages of phosphorus (0 to 3%, w/w), polyurethane elastomers remain stable up to 250,°C. The percentage of residual char at 600,°C increases with increasing phosphorus content. For the soft segments, no variation in the glass transition temperature (Tg) is observed as the percentage of P increases, whereas the Tg of hard segments increases. Above 0.5% phosphorus content, the limiting oxygen index (LOI) becomes higher than the percentage of oxygen in the air. © 2003 Society of Chemical Industry [source]