Tunable Structure and Properties of Segmented Thermoplastic Polyurethanes as a Function of Flexible Segment

Segmented thermoplastic polyurethanes (PUs) were synthetized using macrodiols with different functional groups (carbonate, ester, and /or ether) as a segment with a molar mass of 1000 and 2000 g/mol, and 4,4’-diphenylmethane diisocyanate (MDI) and 1,4-butanediol as a rigid segment. The polyurethanes obtained reveal a wide variation of microphase separation degree that is correlated with mechanical properties and retention of tensile properties under degradation by heat, oil, weather, and water. Different techniques such as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR), and synchrotron small-angle X-ray scattering (SAXS) were used to determine rigid-flexible segments’ phase behaviour. Retention of tensile properties determines the stability of the samples under different external factors. This work reveals that pure polycarbonate-based macrodiols induce the highest degree of phase miscibility, better tensile properties, hardness shore A, and retention of tensile properties under external agents.

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Transparent thermoplastic polyurethanes based on aliphatic diisocyanates and polycarbonate diol

Journal of Elastomers & Plastics ◽

10.1177/0095244316639633 ◽

2016 ◽

Vol 49 (1) ◽

pp. 77-95 ◽

Cited By ~ 12

Author(s):

Clara Maria Gomez ◽

D Gutierrez ◽

M Asensio ◽

V Costa ◽

A Nohales

Keyword(s):

Tensile Properties ◽

Soft Segment ◽

Mechanical Analysis ◽

Attenuated Total Reflection ◽

Hexamethylene Diisocyanate ◽

Scanning Calorimetry ◽

Phase Mixing ◽

Thermoplastic Polyurethanes ◽

Polycarbonate Diol ◽

Weather Resistance

Segmented thermoplastic polyurethanes (PUs) were synthetized using polycarbonate diol as soft segment with a molar mass of 500 and as a hard segment 1,5-pentanediol with a combination of isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI). Differential scanning calorimetry, differential mechanical analysis, Fourier transform infrared-attenuated total reflection spectroscopy, haze, transmittance, hardness, tensile properties and retention of tensile properties tests were employed to characterize the different PUs. The results of this study show that IPDI/HDI relation has a significant impact on the phase mixing, crystallinity and therefore on the PU’s properties. The variation of diisocyanate type ratio allows obtaining PUs of different nature from a high rubbery material with a high content in IPDI to high crystalline PU increasing the HDI content. Material transparency was also modified by decreasing the amorphous nature of the materials with the increase in the HDI content. The weather resistance of the final PU is related with the different isocyanate relation.

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Controlling stereocomplexation, heat resistance and mechanical properties of stereocomplex polylactide films by using mixtures of low and high molecular weight poly(D-lactide)s

e-Polymers ◽

10.1515/epoly-2018-0115 ◽

2018 ◽

Vol 18 (6) ◽

pp. 485-490 ◽

Cited By ~ 3

Author(s):

Yaowalak Srisuwan ◽

Yodthong Baimark

Keyword(s):

Mechanical Properties ◽

Molecular Weight ◽

Heat Resistance ◽

Tensile Properties ◽

Tensile Testing ◽

Mechanical Analysis ◽

Scanning Calorimetry ◽

Molecular Weights ◽

Film Series ◽

High Molecular Weight Poly

AbstractStereocomplex polylactide (scPLA) films were prepared by blending poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) solutions before solvent evaporation. The PLLA/PDLA ratios were 80/20 and 60/40 (w/w). PDLAs with low and high molecular weights (M.W.) were used as PDLA mixtures. The scPLA films with different low/high M.W. PDLA ratios were investigated for both the 80/20 and 60/40 (w/w) scPLA film series. Stereocomplexation, heat resistance and the mechanical properties of the scPLA films were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and tensile testing, respectively. The results indicated that low M.W. PDLA can enhance the stereocomplexation and heat resistance of scPLA films while the high M.W. PDLA can improve tensile properties of scPLA films. It was concluded that the stereocomplexation, heat resistance and tensile properties of scPLA films could be controlled by adjusting the low/high M.W. PDLA ratio in PDLA fraction.

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Influence of film stretching on crystalline phases and dielectric properties of a 70/30 mol% poly(vinylidenefluoride-tetrafluoroethylene) copolymer

Journal of Advanced Dielectrics ◽

10.1142/s2010135x2050023x ◽

2020 ◽

Vol 10 (05) ◽

pp. 2050023

Author(s):

Thulasinath Raman Venkatesan ◽

Anna A. Gulyakova ◽

Reimund Gerhard

Keyword(s):

Dielectric Properties ◽

Polyvinylidene Fluoride ◽

Ferroelectric Phase ◽

Mechanical Analysis ◽

Dielectric Relaxation Spectroscopy ◽

X Ray Diffraction ◽

Scanning Calorimetry ◽

Crystalline Phases ◽

The Stability ◽

Dissipation Losses

Polyvinylidene fluoride (PVDF)-based copolymers with tetrafluoroethylene (P(VDF-TFE)), trifluoroethylene (P(VDF-TrFE)) or hexafluoropropylene (P(VDF-HFP)) are of strong interest due to the underlying fundamental mechanisms and the potential ferro-, pyro- and piezo-electrical applications. Their flexibility and their adaptability to various shapes are advantageous in comparison to inorganic ferroelectrics. Here, we study the influence of stretching temperature on the crystalline phases and the dielectric properties in P(VDF-TFE) films by means of Dielectric Relaxation Spectroscopy (DRS), Fourier-Transform InfraRed spectroscopy (FTIR), Wide-Angle X-ray Diffraction (WAXD), Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). Especially, the effect of stretching and the influence of the temperature of stretching on the mid-temperature ([Formula: see text] transition are studied in detail. The results show that stretching has a similar effect as that on PVDF, and we observe an increase in the fraction of ferroelectric [Formula: see text]-phase with a simultaneous increment in both melting point ([Formula: see text] and crystallinity ([Formula: see text] of the copolymer. While an increase in the stretching temperature does not have a profound impact on the amount of ferroelectric phase, the stability of the ferroelectric phase seems to improve — as seen in the reduction of the Full Width at Half Maximum (FWHM) of the WAXD peaks in both parallel and perpendicular directions to the molecular chain axis. The observation is also supported by the reduction of dissipation losses with an increase in stretching temperature — as seen in DRS measurements. Finally, both stretching itself and the temperature of stretching affect the various molecular processes taking place in the temperature range of the [Formula: see text] transition.

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Effect of diacylhydrazine as chain extender on microphase separation and performance of energetic polyurethane elastomer

e-Polymers ◽

10.1515/epoly-2020-0052 ◽

2020 ◽

Vol 20 (1) ◽

pp. 469-481

Author(s):

Yang Gao ◽

Jie Lv ◽

Licheng Liu ◽

Yingfeng Yu

Keyword(s):

Hydrogen Bonding ◽

Hard Segment ◽

Microphase Separation ◽

Low Cost ◽

Ethylene Carbonate ◽

Mechanical Analysis ◽

Chain Extender ◽

Thermal Transitions ◽

Scanning Calorimetry ◽

Hard Segment Content

AbstractIt is low cost and feasible to improve the mechanical properties of polyurethane by using the chain extender with hydrogen bonding function to improve the degree of microphase separation. In this article, hydrazine hydrate was used to react with ethylene carbonate and propylene carbonate, respectively, to synthesize diacylhydrazines as the polyurethane chain extender with amide bonds, which were characterized by 1H nuclear magnetic resonance. Polyurethane with different contents of hard segment were prepared from poly-3,3-bis(azidomethyl)oxetane-tetrahydrofuran as the polyol and 4,4′-diphenylmethane diisocyanate as the isocyanate components. Fourier transform infrared spectroscopy showed that with the increase of the hard segment content, the proportion of hydrogen-bonded ordered carbonyl group increased to 94%, proving that diacylhydrazines could improve the degree of ordered hydrogen bonding, which led to clear microphase separation observed by field emission scanning electron microscopy and higher storage modulus of the polyurethane. Differential scanning calorimetry and dynamic mechanical analysis showed that polyurethane with higher hard segment content is likely to exhibit multiple thermal transitions caused by microphase separation. When the hard segment content was 40%, compared with polyurethane with 1,4-butanediol as the chain extender, the tensile strengths of polyurethanes with diacylhydrazines also improved by 30% and 76%, respectively.

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Compatibilization of Thermoplastic Polyurethane and Polypropylene with a SEBS Compatibilizer

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1025-1026.605 ◽

2014 ◽

Vol 1025-1026 ◽

pp. 605-614

Author(s):

Ocelić Bulatović Vesna ◽

Govorčin Bajsić Emi ◽

Filipan Veljko

Keyword(s):

Thermoplastic Polyurethane ◽

Mechanical Analysis ◽

Polymer Materials ◽

Creep Recovery ◽

Scanning Calorimetry ◽

Creep Fatigue ◽

The Stability ◽

Creep Modulus ◽

Pp Blends ◽

Constant Deformation

The effect of styrene-ethylene/buthylene-styrene triblock copolymer (SEBS) on the thermal and rheological properties of thermoplastic polyurethane/polypropylene (TPU/PP) blends was investigated. For the selection of polymer materials and polymer blends for various fields of applications the stability of materials under constant deformation are very important. The blends were therefore characterized by measuring secondary viscoelastic functions creep, recovery and creep modulus using dynamic mechanical analysis (DMA) in the creep fatigue regime. The master curves at the reference temperature of 25°C were created by time-temperature correspondence (TTC) principle. The correlation of the creep modulus with time, temperature and addition of compatibilizer was discussed. The differential scanning calorimetry (DSC) results indicated that the addition of SEBS as a compatibilizer in TPU/PP blends increases glass transition temperature (Tg) and decreases crystallinity (χc). SEBS block copolymer acts as an efficient compatibilizer for TPU/PP blends.

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Light-cured dental composites characterization by Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100175272 ◽

1990 ◽

Vol 48 (4) ◽

pp. 428-429

Author(s):

B. M. Culbertson ◽

M. L. Devinev ◽

E. C. Kao

Keyword(s):

Electron Microscopy ◽

Mechanical Analysis ◽

Service Performance ◽

Dental Composite ◽

Dental Composites ◽

Neat Resin ◽

Scanning Calorimetry ◽

Research Meeting ◽

Formulation Variables

The service performance of current dental composite materials, such as anterior and posterior restoratives and/or veneer cements, needs to be improved. As part of a comprehensive effort to find ways to improve such materials, we have launched a broad spectrum study of the physicochemical and mechanical properties of photopolymerizable or visible light cured (VLC) dental composites. The commercially available VLC materials being studied are shown in Table 1. A generic or neat resin VLC system is also being characterized by SEM and TEM, to more fully understand formulation variables and their effects on properties.At a recent dental research meeting, we reported on the differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) characterization of the materials in Table 1. It was shown by DSC and DMA that the materials are substantially undercured by commonly used VLC techniques. Post curing in an oral cavity or a dry environment at 37 to 50°C for 7 or more hours substantially enhances the cure of the materials.

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Star-shaped arylacetylene resins derived from silicon

Journal of Polymer Engineering ◽

10.1515/polyeng-2020-0083 ◽

2020 ◽

Vol 40 (8) ◽

pp. 676-684

Author(s):

Niping Dai ◽

Junkun Tang ◽

Manping Ma ◽

Xiaotian Liu ◽

Chuan Li ◽

...

Keyword(s):

High Performance ◽

Room Temperature ◽

Mechanical Test ◽

Flexural Modulus ◽

Mechanical Analysis ◽

Reinforced Composites ◽

Scanning Calorimetry ◽

Chemical Structures ◽

Structures And Properties ◽

High Performance Resin

AbstractStar-shaped arylacetylene resins, tris(3-ethynyl-phenylethynyl)methylsilane, tris(3-ethynyl-phenylethynyl) phenylsilane, and tris (3-ethynyl-phenylethynyl) silane (TEPHS), were synthesized through Grignard reaction between 1,3-diethynylbenzene and three types of trichlorinated silanes. The chemical structures and properties of the resins were characterized by means of nuclear magnetic resonance, fourier-transform infrared spectroscopy, Haake torque rheomoter, differential scanning calorimetry, dynamic mechanical analysis, mechanical test, and thermogravimetric analysis. The results show that the melt viscosity at 120 °C is lower than 150 mPa⋅s, and the processing windows are as wide as 60 °C for the resins. The resins cure at the temperature as low as 150 °C. The good processabilities make the resins to be suitable for resin transfer molding. The cured resins exhibit high flexural modulus and excellent heat-resistance. The flexural modulus of the cured TEPHS at room temperature arrives at as high as 10.9 GPa. Its temperature of 5% weight loss (Td5) is up to 697 °C in nitrogen. The resins show the potential for application in fiber-reinforced composites as high-performance resin in the field of aviation and aerospace.

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Double-Chain Cationic Surfactants: Swelling, Structure, Phase Transitions and Additive Effects

Molecules ◽

10.3390/molecules26133946 ◽

2021 ◽

Vol 26 (13) ◽

pp. 3946

Author(s):

Rui A. Gonçalves ◽

Yeng-Ming Lam ◽

Björn Lindman

Keyword(s):

Phase Transitions ◽

Phase Behaviour ◽

Double Chain ◽

Scanning Calorimetry ◽

Alkyl Chains ◽

X Ray Scattering ◽

Amphiphilic Compounds ◽

Liquid Phases ◽

Lamellar Phases ◽

Water Layers

Double-chain amphiphilic compounds, including surfactants and lipids, have broad significance in applications like personal care and biology. A study on the phase structures and their transitions focusing on dioctadecyldimethylammonium chloride (DODAC), used inter alia in hair conditioners, is presented. The phase behaviour is dominated by two bilayer lamellar phases, Lβ and Lα, with “solid” and “melted” alkyl chains, respectively. In particular, the study is focused on the effect of additives of different polarity on the phase transitions and structures. The main techniques used for investigation were differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SAXS and WAXS). From the WAXS reflections, the distance between the alkyl chains in the bilayers was obtained, and from SAXS, the thicknesses of the surfactant and water layers. The Lα phase was found to have a bilayer structure, generally found for most surfactants; a Lβ phase made up of bilayers with considerable chain tilting and interdigitation was also identified. Depending mainly on the polarity of the additives, their effects on the phase stabilities and structure vary. Compounds like urea have no significant effect, while fatty acids and fatty alcohols have significant effects, but which are quite different depending on the nonpolar part. In most cases, Lβ and Lα phases exist over wide composition ranges; certain additives induce transitions to other phases, which include cubic, reversed hexagonal liquid crystals and bicontinuous liquid phases. For a system containing additives, which induce a significant lowering of the Lβ–Lα transition, we identified the possibility of a triggered phase transition via dilution with water.

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Phase Behaviour of Methane Hydrates in Confined Media

Crystals ◽

10.3390/cryst11020201 ◽

2021 ◽

Vol 11 (2) ◽

pp. 201

Author(s):

Hao Bian ◽

Lu Ai ◽

Klaus Hellgardt ◽

Geoffrey C. Maitland ◽

Jerry Y. Y. Heng

Keyword(s):

Phase Behaviour ◽

Methane Hydrates ◽

Scanning Calorimetry ◽

Macroporous Silica ◽

Interfacial Energies ◽

Temperature Method ◽

Hydrate Phase ◽

Dissociation Temperature ◽

Confined Media ◽

Decomposition Behaviour

In a study designed to investigate the melting behaviour of natural gas hydrates which are usually formed in porous mineral sediments rather than in bulk, hydrate phase equilibria for binary methane and water mixtures were studied using high-pressure differential scanning calorimetry in mesoporous and macroporous silica particles having controlled pore sizes ranging from 8.5 nm to 195.7 nm. A dynamic oscillating temperature method was used to form methane hydrates reproducibly and then determine their decomposition behaviour—melting points and enthalpies of melting. Significant decreases in dissociation temperature were observed as the pore size decreased (over 6 K for 8.5 nm pores). This behaviour is consistent with the Gibbs–Thomson equation, which was used to determine hydrate–water interfacial energies. The melting data up to 50 MPa indicated a strong, essentially logarithmic, dependence on pressure, which here has been ascribed to the pressure dependence of the interfacial energy in the confined media. An empirical modification of the Gibbs–Thomson equation is proposed to include this effect.

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Quadruple Hydrogen Bond-Containing A-AB-A Triblock Copolymers: Probing the Influence of Hydrogen Bonding in the Central Block

Molecules ◽

10.3390/molecules26154705 ◽

2021 ◽

Vol 26 (15) ◽

pp. 4705

Author(s):

Boer Liu ◽

Xi Chen ◽

Glenn A. Spiering ◽

Robert B. Moore ◽

Timothy E. Long

Keyword(s):

Hydrogen Bonding ◽

Self Assembly ◽

Microphase Separation ◽

Triblock Copolymers ◽

Random Copolymer ◽

Thermomechanical Properties ◽

Structure Property ◽

Scanning Calorimetry ◽

Central Block ◽

Quadruple Hydrogen Bonding

This work reveals the influence of pendant hydrogen bonding strength and distribution on self-assembly and the resulting thermomechanical properties of A-AB-A triblock copolymers. Reversible addition-fragmentation chain transfer polymerization afforded a library of A-AB-A acrylic triblock copolymers, wherein the A unit contained cytosine acrylate (CyA) or post-functionalized ureido cytosine acrylate (UCyA) and the B unit consisted of n-butyl acrylate (nBA). Differential scanning calorimetry revealed two glass transition temperatures, suggesting microphase-separation in the A-AB-A triblock copolymers. Thermomechanical and morphological analysis revealed the effects of hydrogen bonding distribution and strength on the self-assembly and microphase-separated morphology. Dynamic mechanical analysis showed multiple tan delta (δ) transitions that correlated to chain relaxation and hydrogen bonding dissociation, further confirming the microphase-separated structure. In addition, UCyA triblock copolymers possessed an extended modulus plateau versus temperature compared to the CyA analogs due to the stronger association of quadruple hydrogen bonding. CyA triblock copolymers exhibited a cylindrical microphase-separated morphology according to small-angle X-ray scattering. In contrast, UCyA triblock copolymers lacked long-range ordering due to hydrogen bonding induced phase mixing. The incorporation of UCyA into the soft central block resulted in improved tensile strength, extensibility, and toughness compared to the AB random copolymer and A-B-A triblock copolymer comparisons. This study provides insight into the structure-property relationships of A-AB-A supramolecular triblock copolymers that result from tunable association strengths.

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