Effects of Molecular Structure on Physical Properties of Butyl Rubber

1946 ◽  
Vol 19 (3) ◽  
pp. 552-598 ◽  
Author(s):  
Paul J. Flory
Keyword(s):  
Molecular Structure ◽  
Molecular Weight ◽  
Physical Properties ◽  
Small Samples ◽  
Rational Approach ◽  
Complete Evaluation ◽  
Testing Procedures ◽  
Molecular Weights ◽  
Vulcanized Rubber ◽  
Structural Variables

Abstract The investigation was undertaken in an attempt to establish the fundamental connections between the physical properties of a typical vulcanized rubberlike polymer and its chemical structure. The structural variables to be considered are the molecular weight of the “primary molecules” entering the vulcanizate, their molecular-weight distribution, and the concentration (or frequency) of cross-linkages introduced during vulcanization. The molecular weights of Butyl rubbers were determined by previously established procedures ; the effects of molecular-weight heterogeneity were suppressed by careful fractionation from very dilute solution. An indirect method, based on the theory of gelation and on the observation of critical molecular weight for incipient gelation (partial insolubility) in “vulcanisates” formed when the cross-linking capacity is fixed, was employed to determine the frequency of occurrence of cross-linked units—a quantity not hitherto evaluated in a vulcanized rubber. In representative pure-gum vulcanizates of Butyl the molecular weight per cross-linked unit ranges from about 35,000 to 20,000, depending (inversely) on the diolefin content of the raw rubber. Micro compounding and testing procedures have been devised for evaluating the necessarily small samples ob- tained in fractionation. Complete evaluation of tensile strength, stress-strain characteristics, swelling in solvents, and creep rate can be obtained with as little as 3 grams of rubber. Results are no less reproducible than those obtained with conventional procedures requiring 50 grams or more. A number of rela- tionships between vulcanizate structure and physical properties have been established. The feasibility of a rational approach to the interpretation of properties of rubber vulcanizates in terms of molecular structure has been demonstrated.

Relation between Molecular Weights and Physical Properties of Rubber Fractions

1941 ◽  
Vol 14 (3) ◽  
pp. 580-589 ◽  
Author(s):  
G. Gee ◽  
L. R. G. Treloar
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Physical Properties ◽  
High Molecular Weight ◽  
Elastic Properties ◽  
Elastic Material ◽  
Experimental Results ◽  
Molecular Weights ◽  
High Elasticity ◽  
Latex Rubber

Abstract As high elasticity is a property possessed only by substances of high molecular weight, it is of interest to enquire into the relation between the elastic properties of a highly elastic material such as rubber and its molecular weight. An investigation on these lines has been made possible through the work of Bloomfield and Farmer, who have succeeded in separating natural rubber into fractions having different average molecular weights. The more important physical properties of these fractions have been examined with the object of determining which of the properties are dependent on molecular weight and which are not. Fairly extensive observations were made on the fractions from latex rubber referred to as Nos. 2, 3 and 4 by Bloomfield and Farmer, and some less extensive observations were carried out on the less oxygenated portion of fraction No. 1 obtained from crepe rubber (called hereafter 1b) . Before considering these experimental results, and their relation to the molecular weights of the fractions, it will be necessary to refer briefly to the methods used for the molecular-weight determinations, and to discuss the significance of the figures obtained.

Synthesis and Properties of Uniform Polyisoprene Networks. I. Synthesis and Characterization of α,ω-Dihydroxy-Polyisoprene

1976 ◽  
Vol 49 (2) ◽  
pp. 303-319 ◽  
Author(s):  
M. Morton ◽  
L. J. Fetters ◽  
J. Inomata ◽  
D. C. Rubio ◽  
R. N. Young
Keyword(s):  
Molecular Weight ◽  
Physical Properties ◽  
Soluble Fraction ◽  
Synthesis And Characterization ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
The Subject

Abstract The results of this study are the first to show that high-1,4 linear α,ω-dihydroxypolydienes can be synthesized with (a) predictable molecular weights, (b) narrow molecular weight distributions, and (c) high functionalities. Using the functionalized polyisoprenes prepared in this work, a series of networks was prepared with a purified triisocyanate as the chain linking agent. The soluble fraction in these networks ranged from 4.6 to 1.6 per cent. The characteristics and physical properties of these networks will be the subject of a forthcoming publication.

IV. The Micellar Theory of the Structure of Rubber

1942 ◽  
Vol 15 (3) ◽  
pp. 446-451
Author(s):  
G. Gee
Keyword(s):  
Molecular Weight ◽  
Physical Properties ◽  
Infinite Dilution ◽  
Mechanical Deformation ◽  
Point Of View ◽  
Pressure Measurements ◽  
Physical Behavior ◽  
Molecular Weights ◽  
Micelle Size ◽  
Weight Data

Abstract The molecular weight data reported in Part II depend on the assumption that the values obtained by extrapolating osmotic pressure measurements to infinite dilution represent true molecular weights. This point of view has been strongly criticized, particularly by Pummerer and his coworkers, according to whom rubber normally exists in solution in the form of micelles comprising more or less well-defined aggregates containing a considerable number of chemical molecules. The- osmotic “molecular weight” is then regarded as the weight of an average micelle. If they exist, these micelles may be important in determining both the chemical and physical behavior of rubber, for we should clearly expect the bonds by which the chemical molecules are bound into micelles to be weaker than those within the molecules. It may be noted that it has been shown elsewhere that the physical properties of a series of rubber fractions are closely related to their osmotic and viscosity molecular weights. Since, according to the micellar theory, these fractions can differ only in micelle size, their mechanical behavior must, from this viewpoint, be determined by the size of the micelles, which must therefore remain intact during mechanical deformation of the rubber. It is the object of the present paper to examine in more detail the basis of the micellar theory, and especially to offer an interpretation of the results of the East method, on which Pummerer's arguments are mainly based.

Soluble poly(glycerol sebacate) and poly(ε-caprolactone) 3D scaffolds for blood vessel constructs

2016 ◽  
Vol 1819 ◽  
Author(s):  
Ricardo Vera Graziano ◽  
Andromeda A.L. Monroy Brera ◽  
Raúl Montiel Campos ◽  
Alfredo Maciel Cerda
Keyword(s):  
Molecular Structure ◽  
Molecular Weight ◽  
Blood Vessel ◽  
Physical Properties ◽  
High Surface ◽  
Sebacic Acid ◽  
Solvent Mixtures ◽  
Homogeneous Solutions ◽  
Electrospun Scaffolds ◽  
Soluble Poly

ABSTRACTCardiovascular diseases, frequently associated to the formation of aneurisms, are the mayor cause of mortality and morbidity in the world. Due to the increased need for the regeneration of arteries and veins, several natural and synthetic biopolymers such as poly(glycerol sebacate), PGS, have been studied to make blood vessel constructs. PGS elastomeric properties develop after it is crosslinked; however, the poor solubility of the material limits the process to fabricate useful constructs for tissue engineering by electrospinning, casting, or other methods. The structure and properties of electrospun scaffolds made from soluble poly(glycerol sebacate) and poly(ε- caprolactone), are reported here. Soluble PGS oligomers (o-PGS) of different molecular weight, obtained by the polycondensation reaction of sebacic acid and glycerol, were analyzed, including molecular structure, physical properties and solubility. Temperature, reactor atmosphere, and time of reaction strongly influenced the solubility, the molecular weight and molecular structure. To improve o-PGS processing and properties it was mixed with PCL to make electrospun scaffolds. In order to process the mixture by electrospinning, homogeneous solutions o-PGS and PCL were prepared. Because PCL is hydrophobic and o-PGS is hydrophilic selected solvent mixtures were tested to form the homogeneous solutions; the materials dissolved in a mixture of THF:DMF:DCM. Typical electrospinning parameters for preparing the tubular scaffolds at room conditions were: voltage 17.5 kV, needle-collector distance 20 cm and, relative humidity 30-35%, flow injection 0.5 to 2.0 ml/h. The initial mechanical properties of the biodegradable scaffolds were better than those made of natural grafts; the Young’s modulus ranged from 7.6 to 13.0 MPa, depending on electrospinning process parameters. The morphology and physical properties of electrospun PGS/PCL tubular scaffolds show useful features not found in similar constructs made by other methods. The 3D tubular scaffolds were built-up of layered porous walls to produce constructs of different pore size and fibers of different diameter. The porous area was one to two orders of magnitude higher than those produced at micrometer scale by conventional melting and dry/wet spinning methods. These scaffolds show useful characteristics for regenerative medicine such as physical properties; nanometric diameters; high surface/volume ratio; and potentiallity for adhesion and growth of living cells.

scholarly journals The thermal conductivities of carbon monoxide and nitrous oxide

1928 ◽  
Vol 121 (787) ◽  
pp. 285-293 ◽  
Keyword(s):  
Molecular Structure ◽  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Nitrous Oxide ◽  
Kinetic Theory ◽  
Physical Properties ◽  
Kinetic Theory Of Gases ◽  
Molecular Weights ◽  
Thermal Conductivities

The authors’ experiments on the thermal conductivities of carbon monoxide and nitrous oxide were undertaken partly because very few determinations had been made previously, and partly on account of a consideration of other physical properties of these gases. Smith showed experimentally that the viscosities of nitrogen and carbon monoxide are equal, and a similar result was obtained in the case of carbon dioxide and nitrous oxide. Such results are indicated by the Kinetic Theory of Gases from the aspect of the equality of molecular weights in the two cases. Similar equalities are not anticipated, however, in the case of the thermal conductivities, as the conduction effect depends on a consideration of differences in molecular structure. The following table shows the values of the thermal conductivities and the viscosities of the four gases concerned, and illustrates the extent to which the thermal conductivities differ:—

Characterizing Hydrocarbon Plus Fractions

1983 ◽  
Vol 23 (04) ◽  
pp. 683-694 ◽  
Author(s):  
Curtis H. Whitson
Keyword(s):  
Molecular Weight ◽  
Specific Gravity ◽  
Physical Properties ◽  
Critical Pressure ◽  
Probability Function ◽  
Carbon Number ◽  
Physical Property ◽  
Molecular Weights ◽  
Property Estimation ◽  
Boiling Points

Whitson, Curtis H., SPE, U. of Trondheim Abstract Methods are developed for characterizing the molar distribution (mole fraction/molecular weight relation) and physical properties of petroleum fractions such as heptanes-plus (C7 +). These methods should enhance equation-of-state (EOS) predictions when experimental data are lacking. predictions when experimental data are lacking. The three-parameter gamma probability function is used to characterize the molar distribution, as well as to fit experimental weight and molar distributions and to generate synthetic distributions of heptanes-plus fractions. Equations are provided for calculating physical properties such as critical pressure and temperature properties such as critical pressure and temperature of single-carbon-number (SCN) groups. A simple three-parameter equation is also presented for calculating the Watson characterization factor from molecular weight and specific gravity. Finally, a regrouping scheme is developed to reduce extended analyses to only a few multiple-carbon-number (MCN) groups. Two sets of mixing rules are considered, giving essentially the same results when used with the proposed regrouping procedure. Introduction During the development of the application of EOS's to naturally occurring hydrocarbon mixtures, it has become clear that insufficient description of heavier hydrocarbons (e.g., heptanes and heavier) reduces the accuracy of PVT predictions. Volatile oil and gas-condensate volumetric phase behavior is particularly sensitive to composition and properties of the heaviest components. properties of the heaviest components. Until recently there has not been published in technical journals a comprehensive method for characterizing compositional variation, which we call "molar distribution." Several authors have given lucid descriptions of petroleum fraction characterization, though they deal mainly with physical property estimation. Usually, only physical property estimation. Usually, only a single heptanes-plus (C7 + ) fraction lumps together thousands of compounds with a carbon number higher than six. Molecular weight and specific gravity (or density) of the C7 + fraction may be the only measured data available. Preferably, a complete true-boiling-point (TBP) analysis should be performed on fluids to be matched by an EOS. Distillation experiments yield boiling points, specific gravities, and molecular weights, from which molar distribution is found directly. Special analyses of TBP data can also provide estimates of the paraffin/napthene/ aromatic (PNA) content of SCN groups, which are useful in some property correlations. Unfortunately, such high-quality data are seldom available for fluids being matched or predicted by an EOS. If data other than lumped C7+ properties are available, they might include a partial component analysis (weight distribution) from chromatographic measurements. In this case. only weight fractions of SCN groups are reported; normal boiling points, specific gravities, and molecular weights (needed to convert to a molar basis) simply are not available. Compositional simulation based on an EOS involves two major problems:how to "split" a C7 + fraction into SCN groups with mole fractions. molecular weights, and specific gravities that match measured C7+ properties, andif a partial extended analysis (e.g., C 11 + ) is available, how to extend it to higher carbon numbers. The first step in addressing these problems is to find a versatile, easy-to-use probability function for describing molar distribution. The distribution function should allow consistent matching and reasonable extension of partial analyses. Also, it should not contain too many unknown or difficult-to-determine parameters. This paper presents such a probabilistic model and describes its application to several reservoir fluids under "Molar Distribution."The second step in characterizing plus fractions involves estimating SCN group specific gravities, which, together with estimated molecular weights (from the probabilistic model), could be used to estimate critical properties required by EOS's. We address this problem and suggest a simple method for specific gravity estimation under "Physical Properties Estimation." SPEJ p. 683

The Formation and Structure of Vulcanizates

1949 ◽  
Vol 22 (1) ◽  
pp. 96-104
Author(s):  
J. Bardwell ◽  
C. A. Winkler
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Physical Properties ◽  
Network Structure ◽  
Weight Distribution ◽  
Elastic Behavior ◽  
Cross Linking ◽  
Structural Factors ◽  
Experimental Proof ◽  
Vulcanized Rubber

Abstract The characteristic mechanical properties of vulcanized rubber are believed to result from a network structure made up of chainlike molecules bonded together by occasional cross-linkages. In relating the physical properties of the vulcanizate to the structure of the network, it is therefore necessary to consider the concentration of cross-linkages and the molecular-weight distribution of the rubber molecules before cross-linking. Various theories have been proposed for the dependence of elastic properties on these structural factors, but experimental proof of the suggested relations has been meager, largely because of the complexities met with in, vulcanization reactions. In the present investigation some of these difficulties have been overcome, and the quantitative relations between the elastic behavior of GR-S and its network structure have thereby been revealed.

Molecular Degradation of Lubricants in Sliding Elastohydrodynamic Contacts

1975 ◽  
Vol 97 (3) ◽  
pp. 390-395 ◽  
Author(s):  
D. L. Walker ◽  
D. M. Sanborn ◽  
W. O. Winer
Keyword(s):  
Molecular Weight ◽  
Weight Loss ◽  
Small Samples ◽  
Lubricant Degradation ◽  
Shear Rates ◽  
Molecular Weights ◽  
Average Shear ◽  
Bulk Polymers ◽  
Energy Dissipated ◽  
Viscosity Changes

The extent of lubricant degradation in a sliding elastohydrodynamic contact has been investigated. The lubricant was subjected to peak Hertz pressures of approximately 109 N/m2 and average shear rates of 106 to 107 s−1. Hydrocarbon lubricants, bulk polymers and polymer containing hydrocarbon solutions were examined. Small samples (10−8m3) of test lubricant were extracted from the entrance and exit regions of the EHD contact. These samples were then analyzed to determine alterations in the molecular weight distribution. In addition, a microcapillary viscometer was developed to determine viscosity changes. Degradation resulting in up to a 70 percent viscosity loss was found in fluids which had molecular weights of over 1000. High degrees of correlation were found between molecular weight loss, viscosity loss and the energy dissipated in the contact.

Synthesis and characterization of novel β-cyclodextrin cored poly(α-caprolactone)s by anionic ring opening polymerization

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Yingzhi Guo ◽  
Changjiang Yu ◽  
Zhongwei Gu
Keyword(s):  
Molecular Weight ◽  
Physical Properties ◽  
Ring Opening ◽  
Monomer Conversion ◽  
Ring Opening Polymerization ◽  
Molar Ratio ◽  
Molecular Weights ◽  
Molar Ratios ◽  
Anionic Ring ◽  
Feed Molar Ratio

Abstract By anionic ring opening polymerization initiated by cyclodextrin oxyanions generated from NaH and β-cyclodextrin(β-CD), novel biodegradable β- CD cored star-shaped poly(ε-caprolactone)s (s-PCLs) were synthesized and then characterized by means of FTIR, GPC, 1H-NMR. The effects of different feed molar ratios of NaH and β-CD on arm number and on the molecular weight of s-PCLs, and the relationship between the polymerization time and monomer conversion were investigated. Moreover, the physical properties of linear PCL (l-PCL) and s- PCLs with similar molecular weights but different arm number were studied and compared by DSC, SEM and intrinsic viscosity measurement, respectively. It was found that the feed molar ratio of NaH and β-CD is an important factor which influences both the molecular weight and arm number. The melting points and intrinsic viscosities of s-PCLs with similar molecular weights were lower than that of l-PCL, and were found to decrease with increasing arm number. Both SEM and AFM showed that the surface morphology of s-PCL films was different from that of l-PCL. These results indicated that s-PCL with different arms and physical properties could be synthesized using just a β-CD core by adjusting the feed molar ratio of NaH and β-CD

Effect of Primary Molecular Weight on the Dynamic Properties of Cured Rubber

1959 ◽  
Vol 32 (3) ◽  
pp. 651-661
Author(s):  
E. V. Kuvshinskiĭ ◽  
M. M. Fomicheva
Keyword(s):  
Molecular Weight ◽  
Dynamic Modulus ◽  
Room Temperature ◽  
Dynamic Properties ◽  
Molecular Weights ◽  
Vulcanized Rubber ◽  
Equilibrium Modulus ◽  
Modulus Of Resilience ◽  
Molecular Weight Fractions ◽  
Butadiene Styrene

Abstract 1. Studied were the moduli of resilience and rebound elasticity of the vulcanized rubbers made from fractions of butadiene-styrene rubber “SKS-30-A” at temperatures of 20, 60, and 100° C in the region of molecular weights from 45,000 to 620,000 with various degrees of vulcanization (with variation in the pseudoequilibrium modulus from 5 to 70 kg/cm2). 2. The dynamic modulus of resilience is little dependent on the molecular weight of the original rubber both at room temperature and at higher temperatures. 3. At higher temperatures the elasticity of vulcanized rubber is mainly determined by the degree of vulcanization, the measure of which is the pseudo-equilibrium modulus, and is little dependent on the initial molecular weight. At low temperatures (20° C) elasticity increases with the degree of vulcanization, but it increases at different rates for vulcanized rubbers made from fractions with different molecular weights. At 20° C the increase in the degree of vulcanization increases the elasticity of vulcanized rubbers made from low-molecular fractions (45,000) to a lower degree than of those made from high molecular weight fractions (above 133,000). 4. The value of the maximum elasticity of vulcanized rubbers obtained from rubbers of the same molecular weight is not dependent on the type of accelerator used.

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