Polymers elastomeric

Vascular access ports typically consist of a self-sealing siUcone septum within a rigid housing which is attached to a radiopaque catheter (see Radiopaques). The catheter must be fabricated from a low modulus elastomeric polymer capable of interfacing with both soft tissue and the cardiovascular environment. A low modulus polyurethane-based elastomer is preferred to ensure minimal trauma to the fragile vein. 

Synthetic. The main types of elastomeric polymers commercially available in latex form from emulsion polymerization are butadiene—styrene, butadiene—acrylonitrile, and chloroprene (neoprene). There are also a number of specialty latices that contain polymers that are basically variations of the above polymers, eg, those to which a third monomer has been added to provide a polymer that performs a specific function. The most important of these are products that contain either a basic, eg, vinylpyridine, or an acidic monomer, eg, methacrylic acid. These latices are specifically designed for tire cord solutioning, papercoating, and carpet back-sizing. 

Unlike most elastomeric polymers, which are made by direct polymerization of monomers or comonomers, chlorosulfonated polyethylene, as the name implies, is made by chemical modification of a preformed thermoplastic polymer. The chlorination and chlorosulfonation reactions are usually carried out simultaneously but may be carried out ia stages. 

Prepa.ra.tion, The preparation of amorphous high (99%) 1,2-polybutadiene was first reported iu 1981 (27). The use of a heterocycHc chelating diamine such as dipiperidine ethane iu the polymerization gave an amorphous elastomeric polymer of 99.9% 1,2 units and a glass-transition temperature of +5°C. In a previous description (53,54) of the use of a chelating diamine such as A/A/N(N -tetramethylethylene diamine, an 80% 1,2-polybutadiene with a glass-transition temperature of —30°C was produced. 

Micro-mechanical processes that control the adhesion and fracture of elastomeric polymers occur at two different size scales. On the size scale of the chain the failure is by breakage of Van der Waals attraction, chain pull-out or by chain scission. The viscoelastic deformation in which most of the energy is dissipated occurs at a larger size scale but is controlled by the processes that occur on the scale of a chain. The situation is, in principle, very similar to that of glassy polymers except that crack growth rate and temperature dependence of the micromechanical processes are very important. 

H. E. Mark, B. Erman, eds. Elastomeric Polymer Networks, Englewood Cliffs, NJ Prentice Hall, 1992. 

In general, the reaction mechanism of elastomeric polymers with vulcanisation reagents is slow. Therefore, it is natural to add special accelerators to rubber compounds to speed the reaction. Accelerators are usually organic compounds such as amines, aldehyde-amines, thiazoles, thiurams or dithio-carbamates, either on their own or in various combinations. 

Queslel, J. P. and Mark, J. E. Molecular Interpretation of the Moduli Elastomeric Polymer Networks of Know Structure. Vol. 65, pp. 135—176. 

Ewen B, Richter D (1992) In Mark JE, Erman B (eds) Elastomeric polymer networks. Prentice Hall, Englewoods Cliffs... 

Bowden, N. Brittain, S. Evans, A. G. Hutchinson, J. W. Whitesides, G. M. 1998. Spontaneous formation of ordered structures in thin films of metals supported on an elastomeric polymer. Nature 393 146-149. 

Initiators such as BPO are used not only for the initiation of chain reaction polymerization, but also for the curing of polyesters and ethylene-propylene copolymers, and for the grafting of styrene on elastomeric polymer chains. 

Tetrahydrofuran, a five-member cyclic ether, polymerizes cationically to yield an elastomeric polymer [28]. Oxepane, a seven-member analog, polymerizes to a crystalline polymer. 

Pawlow et al. (3) prepared multifiinctionalized high-trans-content elastomeric polymers using Grubbs second-generation ruthenium catalyst in the metathesis polymerization of cyclooctadiene, cyclopentene, and l,4-bis(trimethoxysilyl)-2-butene. 

Various organic dihalides are employed in a reaction with sodium polysulfide to produce organic polysulfides (Thiokols). Ethylene dichloride, from the direct chlorination of ethylene, dichloroethyl formal, and /3,0 -dichlorodiethyl ether are the principal dihalides that have been employed in the process (44). These elastomeric polymers have been commercially available for a number of years, and many applications have been developed for them. They have excellent oil resistance and one of their principal uses has been in hose and tank linings in which that property is required. 

By the process of vulcanization, rubber elasticity, impact resistance, flexibility, thermal stability and many other properties are either introduced or improved. In addition, the crosslinking of non-elastomeric polymers increases the toughness, abrasion resistance and, particularly, the maximum service temperatures of the material. 

The solubility of a gas is an integral part for the prediction of the permeation properties. Various models for the prediction of the solubility of gases in elastomeric polymers have been evaluated (57). Only a few models have been found to be suitable for predictive calculations. For this reason, a new model has been developed. This model is based on the entropic free volume activity coefficient model in combination with Hildebrand solubility parameters, which is commonly used for the theory of regular solutions. It has been demonstrated that mostly good results are obtained. An exception... 

P. Thorlaksen, J. Abildskov, and G.M. Kontogeorgis, Prediction of gas solubilities in elastomeric polymers for the design of thermopane windows, Fluid Phase Equilib., 211(1) 17—33, August 2003. 

Preparation of an aqueous elastomeric polymer emulsion of colloidally dispersed small particles with a particle size of 0.15-0.22 p,... 

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