Physical Properties Of Polymers Research Articles

Interested in Homogeneous Catalysis? Physical Properties of Polymers? Chemical Carcinogenesis?

Interested in Homogeneous Catalysis? Physical Properties of Polymers? Chemical Carcinogenesis?

The design of photoreactive polymer systems for imaging processes

Abstract

Effect of formulation on properties and morphology of polyurethane elastomers

AbstractA model polyurethane elastomers system has been used to study the relationships between chemical formulation, polymer physical structure and mechanical properties. The elastomers were made from formulations comprising a polyether polyol blend (diol plus triol), a chain extender blend (1,4 butane diol plus 1,1,1‐trimethylol propane) and 4,4′‐di‐isocyanate diphenylmethane. The morphologies of the elastomers were investigated in detail, mainly by means of small angle X‐ray scattering techniques. It was confirmed that the polyurethane systems examined comprised domains 50 to 100 Å in size and spaced around 100 to 200 Å apart. A complete decription of the polyurethane morphology has been made in terms of the volume fraction of domains present, the average domain size and the average domain–domain separation. The results suggest that, whilst it is possible to correlate, in general, formulation changes with variations in the elastomer morphology, it seems that direct correlations between physical structure and mechanical properties are not very meaningful in the present model system. However, it is clear that knowledge of the morphology is of considerable importance in interpreting the effects of formulation on observed properties.

Molecular motions in aromatic polyamides and polyimides

NMR was used to study the behaviour of several aromatic polyamides and polyimides over the temperature range of 77–700°K and low molecular weight compounds which simulate polymer chain fragments. Assuming that torsional vibrations of planar groups and units are the main type of molecular motion in these systems, a study was made of actual features of this type of motion and their effect on thermal and physical properties of polymers was investigated. Effects of restricting the intensity of molecular motion as a result of molecular interaction in layers of plane parallel groups are important.

Preparation, thermal characterization and tribological evaluation of some polyquinazolinediones and polyquinazolones

The preparation of a series of pre-polymers by solution polycondensation of 4,4′-diaminodiphenyl-3,3′-dicarboxylic acid (BDC) and di-isocyanates, and the melt polycondensation of BDC and diacetyl derivatives of aromatic diamines is described. These pre-polymers have been characterized and cyclized to yield polyquinazolinediones and polyquinazolones whose structures and thermal stabilities have been investigated. The physical characteristics of films made from these materials were determined after cyclization, and friction and wear characteristics of composite films containing polytetrafluoroethylene, lead oxide and graphite were evaluated in a journal bearing bush configuration. The relationship between wear behaviour and polymer structure, thermal stability and physical properties is discussed.

Polyethylene single crystals: Melting and morphology

AbstractDetermination of important thermodynamic and physical properties of polymers has often been frustrated by the tendency of these materials to reorganize when heated. A novel technique has been developed which permits a more careful examination of the relationships existing between melting and morphology of single crystals. This has lead to the observation that high molecular weight polymers possess much narrower melting ranges than had been previously reported. By using this technique it has been possible to identify distinct transition temperatures for {100} and {110} fold sectors. DTA and DSC data have been previously reported for dried down single crystals. The applicability of this data to single crystals as they exist in suspension is questioned.

Chapter 7. Physical properties of polymers and their solutions

Chapter 7. Physical properties of polymers and their solutions

Cationic copolymerization of cyclopentadiene with 2‐chloroethyl vinyl ether and some properties of the copolymer

AbstractCationic copolymerizations of cyclopentadiene with 2‐chloroethyl vinyl ether were carried out at −78°C using boron trifluoride etherate as a catalyst. Toluene, methylene chloride, and nitroethane were used as polymerization solvents. In each solvent the monomer reactiviety ratios were determined and a solvent effect on the copolymerization was observed, i. e., cyclopentadiene was more reactive in the polar solvents, but less in toluene. This solvent effect could be interpreted based on the differences of monomer nucleophilicities and of stabilities of the two carbonium ions.The copolymers were able to be cured with sulfur and some physical properties of polymers and of their vulcanizates were investigated.

Influence of diluent mobility on the plasticization of polymers

In an attempt to formulate a general picture of the influence of diluents on the physical properties of polymers without invoking specific molecular characteristics of the diluents, a systematic study has been undertaken of the mobility of both the polymer and the diluent in polymer-diluent systems, and of the resulting effects on the physical properties of these systems. In dynamic mechanical and dielectric loss studies of polymer-diluent systems, the influence of the mobility of the diluent on the background loss as well as on the loss associated with subsidiary relaxation transitions has been followed as a function of temperature and correlated with the temperature dependence of the modulus, over temperature ranges which include the low-temperature γ and β transitions. The temperature ranges of plasticization and antiplasticization have been established for bisphenol A polycarbonate and atactic polystyrene plasticized with various phthalates and chlorinated biphenyls and terphenyls, which were selected to have a wide range of glass transition temperatures and plasticizing efficiencies.

Molecular Theories of Rubberlike Elasticity and Polymer Viscoelasticity

Abstract The foundation for nearly all the molecular theories of the physical properties of polymers was laid in 1934 when Guth and Mark and Kuhn first recognized the role of configurational entropy of polymer chains. By virtue of ability of their segments to rotate with respect to each other along the chain backbone, macromolecules are capable of assuming a myriad of conformations. It is this long, flexible chain nature of polymer molecules that provides us a link in interpreting the macroscopic physical properties in terms of microscopic molecular dynamics. In this review we shall demonstrate the utilization of conformational statistics in the formulation of molecular theories for two important aspects of the mechanical properties of polymers. The first part deals with the equilibrium elastic response of a crosslinked rubberlike network. A simplified derivation will be given on the basis of the entropic approach. Some of the underlying assumptions will then be examined, and the contribution of internal energy to rubber elasticity scrutinized. The second part describes the transient viscoelastic properties of linear polymers in solution and in bulk. Limitations of the model will be assessed and its applications to experimental data explored. It should be pointed out that a number of reviews are available in the literature both for elasticity and viscoelasticity of polymers. The present work is not an exhaustive review of these fields, but rather concentrates on the more recent developments not previously discussed. The emphasis will be placed upon polymers in the bulk state, although solution properties will be mentioned where appropriate.

Effect of hydrostatic pressure combined with uniaxial tension on certain physical properties of polymers

The residual changes in the density and swelling properties of high-density polyethylene, teflon, PVC, and ebonite after extension under hydrostatic pressure have been investigated. It is shown that in this case the density of all the materials tested is higher and the swelling lower than in the case of uniaxial tension alone. This effect of hydrostatic pressure is attributable to the creation of favorable conditions for the healing of cracks formed in the deformation process.

The viscoelastic behaviour of plasticized and “antiplasticized” polyvinylchloride

SEVERAL papers have appeared recently in which the question of increase in the elasticity modulus and strength of plasticized polymers as the concentration of plasticizer is increased, is discussed [1-8]. Jackson and Caldwell [1-4] have called this phenomenon antiplasticization and have formulated the basic requirements of low-molecular additives to a polymer, for its strength and elastici ty modulus to be increased. For this purpose they investigated the behaviour of a large number of low-molecular substances (mainly containing phenyl groups), which they mixed with a polycarbonate, and divided them into two classes. Those low-molecular organic substances that cause lowering of the strength and elasticity modulus when added to the polymer they assign to the first class (plasticizers). Low-molecular organic substances that raise the elasticity modulus and strength were assigned to the other class (antiplasticizers). This division of substances into plasticizers and antiplasticizers has more recently been confirmed by a number of authors [7, 8]. I t should be mentioned that effects analogous to antiplasticization, relating to anomalous effects of addition of small amounts of substances on the strength and deformational characteristics of polymers had been observed a considerable time before [9, 10]. When the concentration of plasticizer was large however the strength and elasticity modulus decreased as the concentration of plasticizer was increased [9, 10]. This has complicated ideas about the specific effect of low concentrations of a plasticizer. In references [5] and [6] it was stated that it is not correct to compare the properties of polymers containing different concentrations of the same plasticizer at an arbitrarily chosen (usually room) temperature. In such a comparison it could prove to be that the compositions containing different quantities of the plasticizer are in different physical states. For example at a given temperature a polymer containing a low concentration of plasticizer could be in the glassy state and one with a high concentration of plasticizer in the high-elastic state. I t is understandable that such a comparison would not lead to discovery of the mechanism of the effect of a plasticizer on the physical properties of polymers. For this reason it was proposed [5, 6, 11] tha t the properties of polymers should

The physical properties of polymers based on 1,1,2-trichloro-1,3-butadiene (TCB)

The physical properties of polymers based on 1,1,2-trichloro-1,3-butadiene (TCB)

Evaluation of microstructure and its effect on the physical properties of polymers

Journal of Polymer Science Part C: Polymer SymposiaVolume 30, Issue 1 p. 135-146 Structure of Macromolecules Evaluation of microstructure and its effect on the physical properties of polymers S. Bywater, S. Bywater Division of Applied Chemistry, National Research Council of Canada, Ottawa, CanadaSearch for more papers by this author S. Bywater, S. Bywater Division of Applied Chemistry, National Research Council of Canada, Ottawa, CanadaSearch for more papers by this author First published: 1970 https://doi.org/10.1002/polc.5070300117Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume30, Issue11970Pages 135-146 RelatedInformation

Some Aspects of the Microcellular Urethane Material and Process

The use of novel intermediates for the production of integral- skin microcellular urethane rubber has been explored in detail from the standpoints of polymer physical properties and process ability. Polymer/polyols and quasi-prepolymers were combined to yield extremely reactive, yet controllable, systems which are cured at room temperature and demoldable in less than 10 minutes. The ingredients are liquid at room temperature, shelf stable, and con tain no aromatic diamines, which are relatively expensive and can cause handling and discoloration problems. These novel urethane polymers possess physical properties which were heretofore ob tainable only with the use of aromatic diamine curing agents. Formu lation and process variables were explored to provide the technol ogy necessary for the practical utilization of the raw materials by microcellular urethane rubber parts producers. By proper manipu lation of formulation and processing conditions, rubbers suitable for a wide range of applications have been developed.

Cross-Linking–Effect on Physical Properties of Polymers

Many of the polymers used in composite systems and in other applications are cross-linked or thermoset polymers. How do such cross-linked polymers differ in properties from the better-understood linear or thermoplastic polymers? This review paper attempts to answer this question. The paper is written from the practical viewpoint of the experimental scientist who is using cross-linked polymers but who is not an expert on the theory of cross-linking. In spite of their intractable nature once they have been formed, and the difficulty of fabricating highly cross-linked polymers, such materials have some outstanding properties that make them ideal for many applications. The properties include (1) excellent dimensional stability and low creep rates, (2) resistance to solvents, and (3) in many cases, high heat-distortion or softening temperatures.

The Effect of Backmixing on the Molecular Weight Distribution of Polymers

Abstract One of the factors that has a great effect on the physical properties of polymers is the molecular weight distribution. There is an increasing trend in the polymer manufacturing industry away from batch processes toward continuous processing. One of the drawbacks of continuous flow reactors is backmixing, which has a deleterious effect on the molecular weight distribution. This paper demonstrates this effect on a specific type of polymer. Equations are presented for batch, semibatch, and single continuous stirred tank reactors.

MOLECULAR THEORIES OF RUBBER-LIKE ELASTICITY AND POLYMER VISCOELASTICITY

Abstract The foundation for nearly all the molecular theories of the physical properties of polymers was laid in 1934 when Guth and Mark [I], and Kuhn [21 first recognized the role of configurational entropy of polymer chains. By virtue of ability of their segments to rotate with respect to each other along the chain backbone, macromolecules are capable of assuming a myriad of conformations. It is this long, flexible chain nature of polymer molecules that provides us a link in in terpreting the macroscopic physical properties in terms of microscopic molecular dynamics. In this review we shall demonstrate the utilization of conformational statistics in the formulation of molecular theories for two important aspects of the mechanical properties of polymers. The first part deals with the equilibrium elastic response of a cross-linked rubber -like network. A simplified derivation will be given on the basis of the entropic approach. Some of the underlying assumptions will then be examined, and the contribution...

The effect of structure on chemical and physical properties of polymers

Suggests using polymers to teach the effect of changes in structure on chemical reactivity, the effect of structure on physical properties, the role of catalysts, and the basic principles of a chain reaction mechanism.

The Physical Properties of Polymers

The Physical Properties of Polymers