New Elastomers Derived from Copolymers of Tetrahydrofuran and Propylene Oxide

1963 ◽  
Vol 36 (1) ◽  
pp. 296-304
Author(s):  
L. A. Dickinson
Keyword(s):  
Propylene Oxide ◽  
Boron Trifluoride Etherate ◽  
Polyurethane Elastomers ◽  
Physical Test ◽  
Point Temperature ◽  
Novel Technique ◽  
Polymerization Catalyst ◽  
Viscosity Effects ◽  
Glass Point ◽  
A Chain

Abstract The homopolymers of tetrahydrofuran, polytetramethylene glycols, may be chain-extended to form polyurethane elastomers. These materials, while possessing a low glass point temperature, suffer from cold hardening, and it was decided to investigate copolymers of tetrahydrofuran and propylene oxide as elastomer ingredients. The preparation of these copolymers has been achieved by use of a boron trifluoride etherate polymerization catalyst. Details are given of the properties of both the copolymer and derived elastomers at nominal compositions in the range 50–85 weight per cent of tetrahydrofuran. The copolymers described were synthesized as ingredients for castable elastomers, and in consequence viscosity effects are important. It has been found that no significant increase in viscosity occurs until the tetrahydrofuran content exceeds 75 weight per cent. This indicates that each side methyl group exerts a screening effect over an average of 13 atoms of the polymer backbones. The mechanical testing of the derived elastomers indicates that the copolymerization of tetrahydrofuran and propylene oxide leads to material possessing a low glass point temperature and much better physical properties than the homopolymer of propylene oxide. The elastic properties of a chain-extended diol are dependent on the degree of crosslinking and on the incidence of network deficiencies. Network deficiencies are caused by the presence of monofunctional species in the copolymeric diols, and a novel technique for determining diol monofunctionality based on analysis of physical test data was evolved for these studies.

Residual Deformation of a Hard-Coated Valve Seat Subjected to Thermal Shocks

2010 ◽  
Author(s):  
Jean-Philippe Mathieu ◽  
Jean-Franc¸ois Rit ◽  
Je`roˆme Ferrari ◽  
David Hersant
Keyword(s):  
Welding Process ◽  
Residual Deformation ◽  
The Body ◽  
Dominant Effect ◽  
Welding Temperature ◽  
Physical Test ◽  
Physical Testing ◽  
A Chain ◽  
Globe Valve ◽  
Thermal Shocks

Most safety related valves in EDF’s nuclear plant must prove their ability to sustain thermal shocks of approximately 240K amplitude. This paper evaluates the simulation of a globe valve tested for thermal shocks. Since the physical test campaign showed inadequate internal sealing, the simulation focuses on the residual deformation of the hard alloy, planar seat, welded on successive body designs. This deformation is the result of the thermal loadings first induced by the welding process, then by fluid flow inside the valve. A chain of 3D simulations successively computes: a welding temperature transient in the body, the resulting strain hardening — especially in the seat vicinity —; temperature transients in the flow and the valve parts, and the resulting strains in the body causing a bump deformation of the seat surface. This end result agrees with measurements on the tested valve specimen. We show that inaccurate results are obtained on simpler assumptions, such as no welding, and we give insights on the dominant effect of the first hot, cold, hot transient over other profiles. Finally, the agreement we obtain on deformation predictions is toned down by an unsatisfactory sealing prediction, as well as the complexity and duration of the simulation chain compared with physical testing.

SYNTHESIS OF N-SUBSTITUTED DIISOPROPANOLAMINES, THEIR SEBACATE POLYESTERS AND POLYURETHANE ELASTOMERS

1958 ◽  
Vol 36 (10) ◽  
pp. 1405-1409 ◽  
Author(s):  
Jean L. Boivin
Keyword(s):  
Aqueous Solutions ◽  
Infrared Absorption ◽  
Propylene Oxide ◽  
Sebacic Acid ◽  
Ionization Constants ◽  
Polyurethane Elastomers ◽  
Molecular Weights ◽  
Slight Excess ◽  
Infrared Absorption Spectra ◽  
Strong Acids

Several N-substituted diisopropanolamines were prepared by reacting aqueous solutions of amines with excess propylene oxide at ordinary pressure but higher N-substituted diisopropanolamines had to be prepared in an autoclave at 200 °C. The ionization constants of these bases were measured and recorded as pKa values. Their infrared absorption spectra gave bands common to all diisopropanolamines mainly at 3.04, 7.14, 7.55, 7.85, 9.45, 10.6, and 11.95 microns. Their condensation with sebacic acid gave the corresponding polyesters, which were soluble in strong acids and had molecular weights of about 1500. The hydroxyl-terminated polyesters were cured with a slight excess of 2,4-tolylene diisocyanate at 100 °C for 2 days to yield elastomers of brittle temperatures in the region of −50 °C.

scholarly journals Achievement of Both Mechanical Properties and Intrinsic Self-Healing under Body Temperature in Polyurethane Elastomers: A Synthesis Strategy from Waterborne Polymers

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 989 ◽  
Author(s):  
Liangdong Zhang ◽  
Teng Qiu ◽  
Xiting Sun ◽  
Longhai Guo ◽  
Lifan He ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Body Temperature ◽  
Healing Process ◽  
Waterborne Polyurethane ◽  
Polymer Materials ◽  
Self Healing ◽  
Polyurethane Elastomers ◽  
Elongation At Break ◽  
Synthesis Strategy ◽  
A Chain

Inspired by the growing demand for smart and environmentally friendly polymer materials, we employed 2,2′-disulfanediyldianiline (22DTDA) as a chain extender to synthesize a waterborne polyurethane (WPUR). Due to the ortho-substituted structure of the aromatic disulfide, the urea moieties formed a unique microphase structure in the WPUR, its mechanical strength was enhanced more 180 times relative to that of the material prepared without 22DTDA, and excellent self-healing abilities at body temperature in air or under ultrasound in water were obtained. If the self-healing process was carried out at 37 °C, 50 °C or under ultrasound, the ultimate tensile strength and elongation at break of the healed film could reach 13.8 MPa and 1150%, 15.4 MPa and 1215%, or 16 MPa and 1056%, respectively. Moreover, the WPUR films could be re-healed at the same fracture location over three cutting–healing cycles, and the recovery rates of the tensile strength and elongation at break remained almost constant throughout these cycles.

Experimental Investigation of Casting Shape Memory Polyurethane

2014 ◽  
Vol 703 ◽  
pp. 191-195
Author(s):  
Guang Ling Li ◽  
Hong Lei Zhou
Keyword(s):  
Hot Press ◽  
Point Temperature ◽  
Good Ductility ◽  
Comprehensive Properties ◽  
Glass Point ◽  
Development Technology ◽  
Shape Memory Polyurethane ◽  
Polymerization Method ◽  
Press Molding ◽  
Temperature Crack

It is feasible to polymerize SMPU from MDI, PBA, BDO and DMF. Each component has a good ductility, but there are insufficient in terms of strength, glass-point temperature, crack resistance and implosion tendencies. The formulation (PBA: BDO: MDI: DMF=1: 3: (3-4): (7-8)) is recommended. SMPU polymerized by this proportion has good comprehensive properties. The effect of the two-step prepolymerization method, especially the full polymerization method is satisfactory. The composite Materials obtained from powders and particles by hot press molding and that formed by cotton fabric have good ductility. Finally, some suggestions are proposed about implosion preventing, casting crack preventing and development technology.

Influence of Glycols on the Glycolysis Process and the Structure and Properties of Polyurethane Elastomers

2011 ◽  
Vol 43 (6) ◽  
pp. 529-541 ◽  
Author(s):  
J. Datta ◽  
J. T. Haponiuk
Keyword(s):  
Chain Elongation ◽  
Step Method ◽  
Polyurethane Elastomers ◽  
Elongation At Break ◽  
Tensile Tester ◽  
Molecular Masses ◽  
One Step ◽  
The Mean ◽  
A Chain ◽  
Glycolysis Process

In this work, the influence of glycols on the glycolysis process and the properties of obtained polyurethanes were investigated. The glycolysates were produced via glycolysis of waste polyurethane foam in the reaction with one of the following glycols: 1,3-propanediol, 1,5-pentanediol, and 1,6-hexanediol.The reactions were carried out for different mass ratios of polyurethane wastes to glycolysis agent, i.e. 6:1, 8:1, and 10:1. Polyurethanes were synthesized from the obtained intermediates by a one-step method of mixing polymeric di-isocyanate and the glycolysis products with molecular masses ranging from 700 to 1000, while a polyol (Poles 55/20) was used as a chain elongation agent. The influence of glycolysates on tensile strength and elongation at break of polyurethanes was investigated using a Zwick universal tensile tester. Thermal decomposition of the obtained glycolysates and polyurethanes was investigated by thermogravimetry coupled with Fourier transform infrared spectroscopy. It has been found that of all used glycols, 1,6-hexanediol gives the best improvement in the thermal stability of polyurethanes during the glycolysis process. The mean hardness of polyurethanes decreases but rebound resilience increases with chain length of the glycol used for obtaining glycolysates.

Chain Extension Studies Relevant to the Completeness of End-Linking in Elastomeric Polyurethane Networks

1982 ◽  
Vol 55 (5) ◽  
pp. 1464-1468 ◽  
Author(s):  
J. E. Mark ◽  
P. H. Sung
Keyword(s):  
Propylene Oxide ◽  
Relevant Information ◽  
Polymer Chains ◽  
Chain Extension ◽  
Polyurethane Elastomers ◽  
Molecular Weights ◽  
Before And After ◽  
End Linking ◽  
Poly Propylene

Abstract Polyurethane elastomers may be prepared by end-linking hydroxyl-terminated (atactic) poly(propylene oxide) chains with an aromatic triisocyanate. As is invariably the case, networks thus formed are insoluble and very difficult to analyze with regard to the completeness of the end-linking reaction. Relevant information can, however, be obtained by studying the products of the analogous reaction, between a structurally similar diisocyanate and the same polymer chains, under identical conditions. Since both reactants now have functionalities less than three, the reaction gives chain extension rather than crosslinking (gelation), and it is now possible to measure molecular weights before and after the reaction. Such experiments were carried out using diphenylmethane-4,4′-diisocyanate with poly(propylene oxide) chains which had viscosity-average molecular weights ranging from 10−3Mv=1.15−4.50 g mol−1. Values of Mv were found to increase by factors of 20–30, which indicates high extents of reaction. These results are relevant with regard to the probable efficiency of polyurethane curing techniques, and also for the characterization of “model” networks used in the quantitative evaluation of the molecular theories of rubberlike elasticity.

Observation of Atom Rows in Thorium Pyromellitate Using a Field Emission STEM

1977 ◽  
Vol 35 ◽  
pp. 80-81
Author(s):  
H. Todokoro ◽  
S. Nomura ◽  
T. Komoda
Keyword(s):  
Field Emission ◽  
Amorphous Carbon ◽  
Carbon Film ◽  
Dark Field Image ◽  
Dark Field ◽  
Amorphous Carbon Film ◽  
Atomic Size ◽  
Wide Range ◽  
A Chain

It is interesting to observe polymers at atomic size resolution. Some works have been reported for thorium pyromellitate by using a STEM (1), or a CTEM (2,3). The results showed that this polymer forms a chain in which thorium atoms are arranged. However, the distance between adjacent thorium atoms varies over a wide range (0.4-1.3nm) according to the different authors.The present authors have also observed thorium pyromellitate specimens by means of a field emission STEM, described in reference 4. The specimen was prepared by placing a drop of thorium pyromellitate in 10-3 CH3OH solution onto an amorphous carbon film about 2nm thick. The dark field image is shown in Fig. 1A. Thorium atoms are clearly observed as regular atom rows having a spacing of 0.85nm. This lattice gradually deteriorated by successive observations. The image changed to granular structures, as shown in Fig. 1B, which was taken after four scanning frames.

Time-Resolved Cryo-Electron Microscopy of Oscillating Microtubules

1990 ◽  
Vol 48 (1) ◽  
pp. 502-503
Author(s):  
Eva-Maria Mandelkow ◽  
Ron Milligan
Keyword(s):  
Electron Microscopy ◽  
Dynamic Instability ◽  
Entire Solution ◽  
Reaction Scheme ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
A Chain ◽  
Ray Scattering

Microtubules form part of the cytoskeleton of eukaryotic cells. They are hollow libers of about 25 nm diameter made up of 13 protofilaments, each of which consists of a chain of heterodimers of α-and β-tubulin. Microtubules can be assembled in vitro at 37°C in the presence of GTP which is hydrolyzed during the reaction, and they are disassembled at 4°C. In contrast to most other polymers microtubules show the behavior of “dynamic instability”, i.e. they can switch between phases of growth and phases of shrinkage, even at an overall steady state [1]. In certain conditions an entire solution can be synchronized, leading to autonomous oscillations in the degree of assembly which can be observed by X-ray scattering (Fig. 1), light scattering, or electron microscopy [2-5]. In addition such solutions are capable of generating spontaneous spatial patterns [6].In an earlier study we have analyzed the structure of microtubules and their cold-induced disassembly by cryo-EM [7]. One result was that disassembly takes place by loss of protofilament fragments (tubulin oligomers) which fray apart at the microtubule ends. We also looked at microtubule oscillations by time-resolved X-ray scattering and proposed a reaction scheme [4] which involves a cyclic interconversion of tubulin, microtubules, and oligomers (Fig. 2). The present study was undertaken to answer two questions: (a) What is the nature of the oscillations as seen by time-resolved cryo-EM? (b) Do microtubules disassemble by fraying protofilament fragments during oscillations at 37°C?

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