Properties of Polyether-Polyester Thermoplastic Elastomers

1977 ◽  
Vol 50 (1) ◽  
pp. 1-23 ◽  
Author(s):  
A. Lilaonitkul ◽  
S. L. Cooper
Keyword(s):  
Melting Point ◽  
Hard Segment ◽  
Elevated Temperatures ◽  
Basic Structure ◽  
Thermoplastic Elastomers ◽  
Degree Of Crystallinity ◽  
Fabrication Procedure ◽  
Hard Segments ◽  
Average Block ◽  
Definition Of

Abstract The viscoelastic properties of polytetramethylene oxide—polytetramethylene terephthalate block polymers are strongly influenced by phase separation of the 4GT hard blocks into crystalline domains. Thermal analysis reveals a single Tg which increases with increasing 4GT content. This suggests that short sequences of hard segments form a compatible interlamellar amorphous phase with the polyether component. The Gordon-Taylor equation was found to model Tg behavior accurately, provided that the crystalline polyester component was not included in the definition of the hard segment. The melting point of the polytetramethylene terephthalate blocks depends on the average block length of crystallizable segment. Incorporating non-crystallizing polytetramethylene 1,4-cyclohexanedicarboxylate into the hard segment reduces the 4GT melting point and degree of crystallinity. The morphological features of the copolymers depend on sample composition and fabrication procedure. The basic structure is spherulitic. Three different types of spherulite were observed: positive and negative spherulites, as well as spherulites which have their optical axis 45° to their radial direction. The different spherulite types are relatively stable; annealing the samples at elevated temperatures does not alter their morphology. Annealing does increase the degree of crystallinity somewhat and produces crystallites in equilibrium at the annealing temperature. Infrared dichroism studies reveal that, at low deformations, the hard segment lamellae orient as a whole in the stretching direction. This is refleeted by the initial negative orientation of the hard segments. At this stage of elongation, the deformation of the crystallites is nearly reversible. At higher strain levels, the lamellae are disrupted and the hard segments orient positively with a high degree of orientational hysteresis. The soft segments, however, orient almost reversibly in the stress direction at all strain levels studied. It is concluded that the extensive stress softening is brought about by plastic deformation of the crystalline hard segments.

scholarly journals Influence of e-beam irradiation on the chemical and crystal structure of poly(aliphatic/aromatic-ester) multiblock thermoplastic elastomers

2012 ◽  
Vol 14 (2) ◽  
pp. 70-74 ◽  
Author(s):  
Miroslawa El Fray ◽  
Marta Piątek-Hnat ◽  
Judit Puskas ◽  
Elizabeth Foreman-Orlowski
Keyword(s):  
Crystal Structure ◽  
Tensile Tests ◽  
Thermoplastic Elastomers ◽  
Degree Of Crystallinity ◽  
Aromatic Ester ◽  
Multiblock Copolymers ◽  
Beam Irradiation ◽  
Static Tensile ◽  
Chemical Crosslinks ◽  
Hard Segments

Influence of e-beam irradiation on the chemical and crystal structure of poly(aliphatic/aromatic-ester) multiblock thermoplastic elastomers Poly(aliphatic/aromatic-ester) (PED) multiblock copolymers belong to the class of thermoplastic elastomers (TPEs), characterized by a physical network of semi-crystalline hard segments. The PEDs were modified with e-beam to create an additional network structure. Polymers were evaluated using SEC, WAXS, DSC and quasi-static tensile tests. E-beam irradiation induced a significant increase of molecular weight and tensile strength of the PEDs. This effect, together with the diminished degree of crystallinity can be explained by the formation of chemical crosslinks, which are located in the hard phase segments.

Dynamically Vulcanized Thermoplastic Elastomers

1996 ◽  
Vol 69 (3) ◽  
pp. 476-494 ◽  
Author(s):  
S. Abdou-Sabet ◽  
R. C. Puydak ◽  
C. P. Rader
Keyword(s):  
Elevated Temperatures ◽  
Elastic Recovery ◽  
Great Majority ◽  
Thermoplastic Elastomers ◽  
Dynamic Vulcanization ◽  
Product Lines ◽  
Wide Range ◽  
Rubber Phase ◽  
Definition Of ◽  
Thermoplastic Polyolefin

Abstract Thermoplastic elastomers (TPEs) exhibit the functional properties of conventional thermoset rubber, yet can be processed on thermoplastic fabrication equipment. The great majority of TPEs have hetero-phase morphology, whether the TPE is derived from block copolymers, rubber-plastic compositions or ionomers. Generally speaking, the hard domains (or the ionic clusters) undergo dissociation at elevated temperatures, thus allowing the material to flow. When cooled, the hard domains again solidify and provide tensile strength at normal use temperatures. The soft domains give the material its elastomeric characteristics. In this review article, the focus is on rubber-plastic polymer compositions as a group of TPEs which have achieved significant growth in the marketplace in the last two decades. The growth has been primarily in the nonpolar (olefinic) elastomer/polyolefin thermoplastic materials because of the wide range of products generated, their performance and their significant acceptance by the automotive sector in applications requiring elastic recovery. The field of TPEs based on polyolefin rubber-plastic compositions has grown along two distinctly different product lines or classes: one class consists of a simple blend and classically meets the definition of a thermoplastic elastomeric olefin (TEO), commonly called a thermoplastic polyolefin (TPO) in earlier literature. In the other class, the rubber phase is dynamically vulcanized, giving rise to thermoplastic vulcanizates (TPVs), named elastomeric alloys (EAs) in some previous literature. Both the simple blends and the dynamically vulcanized TPEs have found wide industrial application. It is the dynamically vulcanized TPE that has the performance characteristics required for true thermoset rubber replacement applications. The first TPE introduced to the market based on a crosslinked rubber-plastic composition (1972) was derived from W. K. Fisher's discovery of partially crosslinking the EPDM phase of EPDM/polypropylene (PP). Fisher controlled the degree of vulcanization by limiting the amount of peroxide, to maintain the thermoplastic processability of the blend. Crosslinking was performed while mixing, a process known as dynamic vulcanization. It is worth noting, however, that the dynamic vulcanization process and the first crosslinked EPDM/PP composition were discovered independently by Gessler and Haslett and by Holzer, Taurus and Mehnert in 1958 and 1961, respectively. Significant improvement in the properties of these blends was achieved in 1975 by Coran, Das and Patel by fully vulcanizing the rubber phase under dynamic shear while maintaining the thermoplasticity of the blend. These blends were further improved by Abdou-Sabet and Fath in 1977 by the use of phenolic curatives to improve the rubber-like properties and the flow (processing) characteristics.

Polycarbonate-based polyurethane elastomers: temperature-dependence of tensile properties

2014 ◽  
Vol 68 (2) ◽  
Author(s):  
Zdeněk Hrdlička ◽  
Antonín Kuta ◽  
Rafał Poręba ◽  
Milena Špírková
Keyword(s):  
Tensile Properties ◽  
Hard Segment ◽  
Elevated Temperatures ◽  
Thermoplastic Elastomers ◽  
Chain Extender ◽  
Hexamethylene Diisocyanate ◽  
Polyurethane Elastomers ◽  
Oh Groups ◽  
Polycarbonate Diol ◽  
Polyurethane Composition

AbstractNovel polyurethane thermoplastic elastomers were prepared from polycarbonate diols, butane-1,4-diol (chain extender) and hexamethylene diisocyanate. They differ in the kind of macrodiol used and the ratio of macrodiol to chain extender OH groups (hence, in hard segment contents). The tensile properties of the elastomers at low and elevated temperatures were determined and discussed with regard to polyurethane composition and polycarbonate diol structure.

Chain Conformation in Elastomeric Multiblock Copolymers as Measured by Small-Angle Neutron Scattering

1985 ◽  
Vol 58 (5) ◽  
pp. 899-912 ◽  
Author(s):  
Stuart L. Cooper ◽  
John A. Miller
Keyword(s):  
Small Angle ◽  
Hard Segment ◽  
Elevated Temperatures ◽  
Soft Segment ◽  
Random Coil ◽  
Radius Of Gyration ◽  
Soft Phase ◽  
Soft Segments ◽  
Hard Segments ◽  
Increasing Temperature

Abstract Small-angle neutron scattering has been shown to be an effective technique for investigating segment conformation in two-phase multiblock copolymer systems. By choosing the appropriate isotopic compositions, either segment can be investigated, as can the whole chain. The best approach to the experiment is to use a phase-contrast matched sample, one where no interphase scattering occurs. This allows the experiments to be carried out on a single sample, simplifying the experiment, and reducing the beam time requirements. Equations (2) and (3) describe the phase-contrast matched criterion. At room temperature, the polyether soft segments in the polyurethane elastomer-and in the polyether-polyester block copolymers are somewhat extended on the average relative to the bulk oligomer conformation. In the polyether-polyester with a lower hard-segment content, the soft segments are less extended than in the higher ester content material. A distribution of conformations occurs in these materials, with a majority of the soft segments being nearly in a random-coil conformation. A substantial number of segments are fairly taut, leading to an average conformation that is somewhat extended relative to the random coil conformation. The soft-segment radius of gyration in the polyurethane material initially decreases with increasing temperature. As the temperature rises, the retractive force on the taut soft segments increases, thus facilitating the extraction of hard segments from the amorphous hard phase into the soft phase. One would expect that the degree of phase separation would decrease with increasing temperature due to such a mechanism, and in fact this is borne out by small-angle x-ray scattering studies. Above 150°C, an upturn in the soft-segment radius of gyration is observed. Koberstein et al. propose a phase mixing transition around this temperature in polyurethane systems. Such a transition implies a greater compatibility between the hard and soft segment types at elevated temperatures. Thus, a swelling of the soft segments is seen due to favorable interactions with the hard segments located in the soft phase. A schematic diagram of the polyurethane microstructure and chain conformation is presented in Figure 9. The soft-segment radius of gyration in the polyether-polyester materials decreases smoothly with increasing temperature. This is primarily due to a decrease in the number of taut tie molecules present at elevated temperatures due to the rearrangement of the hard crystalline domains. In addition, relaxation of stresses introduced by molding these samples below the hard-segment crystalline melting temperature may contribute to the decrease in the soft-segment Rg.

scholarly journals Synthesis of thermoplastic poly(ester-siloxane)s in the melt and in solution

2005 ◽  
Vol 70 (12) ◽  
pp. 1469-1485 ◽  
Author(s):  
Biljana Dojcinovic ◽  
Vesna Antic ◽  
Marija Vuckovic ◽  
Jasna Djonlagic
Keyword(s):  
1H Nmr Spectroscopy ◽  
Hard Segment ◽  
Soft Segment ◽  
Weight Ratio ◽  
Thermoplastic Elastomers ◽  
Degree Of Crystallinity ◽  
Mechanical Spectroscopy ◽  
Scanning Calorimetry ◽  
Melting Temperatures ◽  
High Boiling Solvent

Two series of thermoplastic elastomers, based on poly(dimethylsiloxane) PDMS, as the soft segment and poly(butylene terephthalate), PBT, as the hard segment, were synthesized by catalyzed transesterification, from dimethyl terephthalate, DMT, silanol-terminated poly(dimethylsiloxane), PDMS-OH Mn=1750g/mol, and 1,4-butanediol, BD. The mole ratio of the starting comonomers was selected to result in a constant hard to soft weight ratio of 55:45. The first series was synthesized in order to determine the optimal mole ratio of BD and DMT for the synthesis of high molecular weight thermoplastic poly(ester-siloxane)s, TPESs. The second series was performed in the presence of the high-boiling solvent, 1,2,4-trichlorbenzene in order to increase the mixing between the extremely non-polar siloxane prepolymer and the polar reactants, DMT and BD, and, therefore, avoid phase separation during synthesis. The structure and composition of the synthesized poly(ester-siloxane)s were verified by 1H-NMR spectroscopy, while the melting temperatures and degree of crystallinity were determined by differential scanning calorimetry (DSC). The effectiveness of the incorporation of the silanol-terminated poly( dimethylsiloxane) into the polyester chains was verified by chloroform extraction. The rheological properties of the poly(ester-siloxane)s were investigated by dynamic mechanical spectroscopy (DMA).

scholarly journals The influence of hard segment content on mechanical and thermal properties of polycarbonate-based polyurethane materials

2012 ◽  
Vol 66 (6) ◽  
pp. 853-862 ◽  
Author(s):  
Jelena Pavlicevic ◽  
Milena Spirková ◽  
Jaroslava Budinski-Simendic ◽  
Mirjana Jovicic ◽  
Oskar Bera ◽  
...  
Keyword(s):  
Phase Separation ◽  
Hard Segment ◽  
Soft Segment ◽  
Chain Extender ◽  
Melting Enthalpy ◽  
Degree Of Crystallinity ◽  
Elongation At Break ◽  
Hard Segment Content ◽  
Hard Segments ◽  
Polycarbonate Diol

Aliphatic segmented polyurethanes were prepared by one-step procedure in catalytic reaction between polycarbonate diol, hexamethylene-diisocyanate and 1,4-butandiol (as chain extender). The hard segment content TS was varied (17, 24, 30 and 42 wt. %) by changing the ratio of starting compounds. The soft segment is made from flexible aliphatic polycarbonate diol, while hard segments consist of chain extender and diisocyanate component. In order to study the hydrogen bonding formation and phase separation, Fourier transform infrared spectroscopy (FT-IR) was used. Wide angle X-ray scattering (WAXS) was performed to determine a degree of crystallinity and to investigate the phase behavior of prepared elastomers. The effect of TS content on mechanical properties (tensile strength, elongation at break and hardness) was tested. Thermal behavior of prepared novel polycarbonate-based polyurethanes was investigated using differential scanning callorimetry (DSC). It was determined that the elastomer which contains the highest amount of urethane groups in its structure (TS content of 42 wt. %) exhibits the most pronounced phase separation and the highest degree of crystallinity. All prepared polyurethanes exhibit high elongation at break (over 700%). The glass transition temperature Tg of prepared samples was in the temperature region from ?39 to ?36?C, and it was found to be slightly influenced by the soft segment content. The enthalpy of chain segments relaxation in diffused region between hard and soft domains (detected in the temperature range from 35 to 55 ?C) was decreased with the increase of hard segment content. The multiple melting of hard segments (connected with the dissruption of physical crosslinks) appeared above 100 ?C. It was found that the melting enthalpy linearly increases with the increase of urethane group content. Sample with 42 wt. % of TS has the highest value of melting enthalpy (41.5 J/g).

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

scholarly journals PEG-POSS Star Molecules Blended in Polyurethane with Flexible Hard Segments: Morphology and Dynamics

Molecules ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 99
Author(s):  
Konstantinos N. Raftopoulos ◽  
Edyta Hebda ◽  
Anna Grzybowska ◽  
Panagiotis A. Klonos ◽  
Apostolos Kyritsis ◽  
...  
Keyword(s):  
Glass Transition ◽  
Star Polymer ◽  
Polymerization Process ◽  
Degree Of Crystallinity ◽  
Dielectric Relaxation Spectroscopy ◽  
Scanning Calorimetry ◽  
Similar System ◽  
Soft Phase ◽  
Hard Segments ◽  
Star Molecules

A star polymer with a polyhedral oligomeric silsesquioxanne (POSS) core and poly(ethylene glycol) (PEG) vertex groups is incorporated in a polyurethane with flexible hard segments in-situ during the polymerization process. The blends are studied in terms of morphology, molecular dynamics, and charge mobility. The methods utilized for this purpose are scanning electron and atomic force microscopies (SEM, AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and to a larger extent dielectric relaxation spectroscopy (DRS). It is found that POSS reduces the degree of crystallinity of the hard segments. Contrary to what was observed in a similar system with POSS pendent along the main chain, soft phase calorimetric glass transition temperature drops as a result of plasticization, and homogenization of the soft phase by the star molecules. The dynamic glass transition though, remains practically unaffected, and a hypothesis is formed to resolve the discrepancy, based on the assumption of different thermal and dielectric responses of slow and fast modes of the system. A relaxation α′, slower than the bulky segmental α and common in polyurethanes, appears here too. A detailed analysis of dielectric spectra provides some evidence that this relaxation has cooperative character. An additional relaxation g, which is not commonly observed, accompanies the Maxwell Wagner Sillars interfacial polarization process, and has dynamics similar to it. POSS is found to introduce conductivity and possibly alter its mechanism. The study points out that different architectures of incorporation of POSS in polyurethane affect its physical properties by different mechanisms.

scholarly journals Investigation into the Structural, Chemical and High Mechanical Reforms in B4C with Graphene Composite Material Substitution for Potential Shielding Frame Applications

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1921
Author(s):  
Ibrahim M. Alarifi
Keyword(s):  
Composite Material ◽  
Melting Point ◽  
Boron Carbide ◽  
High Strength ◽  
Stir Casting ◽  
High Fracture Toughness ◽  
Chemical Compositions ◽  
High Fracture ◽  
Fabrication Procedure ◽  
Standard Designs

In this work, boron carbide and graphene nanoparticle composite material (B4C–G) was investigated using an experimental approach. The composite material prepared with the two-step stir casting method showed significant hardness and high melting point attributes. Scanning electron microscopy (SEM), along with energy dispersive X-ray spectroscopy (EDS) analysis, indicated 83.65%, 17.32%, and 97.00% of boron carbide + 0% graphene nanoparticles chemical compositions for the C-atom, Al-atom, and B4C in the compound studied, respectively. The physical properties of all samples’ B4C–G like density and melting point were 2.4 g/cm3 density and 2450 °C, respectively, while the grain size of B4C–G was in the range of 0.8 ± 0.2 µm. XRD, FTIR, and Raman spectroscopic analysis was also performed to investigate the chemical compositions of the B4C–G composite. The molding press composite machine was a fabrication procedure that resulted in the formation of outstanding materials by utilizing the sintering process, including heating and pressing the materials. For mechanical properties, high fracture toughness and tensile strength of B4C–G composites were analyzed according to ASTM standard designs. The detailed analysis has shown that with 6% graphene content in B4C, the composite material portrays a high strength of 134 MPa and outstanding hardness properties. Based on these findings, it is suggested that the composite materials studied exhibit novel features suitable for use in the application of shielding frames.

scholarly journals Impact of Macrodiols on the Morphological Behavior of H12MDI/HDO-Based Polyurethane Elastomer

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2060
Author(s):  
Shazia Naheed ◽  
Mohammad Zuber ◽  
Mahwish Salman ◽  
Nasir Rasool ◽  
Zumaira Siddique ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Chain Length ◽  
Microphase Separation ◽  
Soft Segment ◽  
Group Identification ◽  
Degree Of Crystallinity ◽  
Polyurethane Elastomers ◽  
Hard Segments ◽  
Morphological Behavior

In this study, we evaluated the morphological behavior of polyurethane elastomers (PUEs) by modifying the soft segment chain length. This was achieved by increasing the soft segment molecular weight (Mn = 400–4000 gmol−1). In this regard, polycaprolactone diol (PCL) was selected as the soft segment, and 4,4′-cyclohexamethylene diisocyanate (H12MDI) and 1,6-hexanediol (HDO) were chosen as the hard segments. The films were prepared by curing polymer on Teflon surfaces. Fourier transform infrared spectroscopy (FTIR) was utilized for functional group identification in the prepared elastomers. FTIR peaks indicated the disappearance of −NCO and −OH groups and the formation of urethane (NHCOO) groups. The morphological behavior of the synthesized polymer samples was also elucidated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The AFM and SEM results indicated that the extent of microphase separation was enhanced by an increase in the molecular weight of PCL. The phase separation and degree of crystallinity of the soft and hard segments were described using X-ray diffraction (XRD). It was observed that the degree of crystallinity of the synthesized polymers increased with an increase in the soft segment’s chain length. To evaluate hydrophilicity/hydrophobicity, the contact angle was measured. A gradual increase in the contact angle with distilled water and diiodomethane (38.6°–54.9°) test liquids was observed. Moreover, the decrease in surface energy (46.95–24.45 mN/m) was also found to be inconsistent by increasing the molecular weight of polyols.

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