Rheology application polymers

Baird, D. G. The rheology of polymers with liquid-crystalline order, in Rheology, Vol. 3, Applications (ed.) Astarita, G., Mannicci, G., Nicolais, L., p. 647, New York, Plenum, 1980... 

The crosslink density ultimately defines the rheological and mechanical properties of the polymer. Polymers that have a high crosslink density are thermosets and are infusible, insoluble, and dimensionally stable under load. These properties make epoxy resin systems useful as structural adhesives as well as important materials in other applications. Polymers that have a low crosslink density are more flexible and show greater resistance to stress concentration, impact, and cold. 

The rheology of polymer colloids is crucially important for coating applications and better control of rheology is sought by the polymer colloids industry. The development of theoretical treatments that model the particles realistically (i.e., not as hard spheres) is paramount. 

In this section, some other relevant aspects of the rheology of polymer melts are addressed in some detail. The case of filled systems is discussed first. These types of systems are of significant importance in industrial applications. In addition, molecular dynamic and fluid dynamic simulations that have greatly benefited from the significant advances in computer power are discussed to some extent. 

Kulicke WM, Kull AH, Kull W, Thielkmg H, EngeUiart J, Pannek JB (1996) Characterization of aqueous carboxymethylcellulose solutions in terms of their molecular structure and its influence on rheological behavior. Polymer 37(13) 2723-2731 Kulicke WM, Reinhardt Fuller UGG, Arendt O (1999) Characterization of the flow properties of sodium carboxymethylcellulose via mechanical and optical techniques. Rheol Acta 38 26-33 Kulshreshtha AK, Dweltz NE (1973) Para crystalline lattice disorder in cellulose - 1. Reappraisal of the application of the two-phase hypothesis to the analysis of powder x-ray diffractograms of native and hydrolyzed cellulosic materials. J Polym Sci 11 487 97 Mathur NK, Mathur V (2001) Chemical Weekly, July Edition, 155... 

Sung Gun Chu, chemist, received a Ph.D. degree in physical polymer chemistry from the University of Texas at Austin in 1978. His main interests are in the property-structure processing relations of polymeric materials, and the rheology of polymers. Since Dr. Chu began work at Hercules in April 1981, he has been involved in the study of adhesives and sealants. He is also involved in the development of new, tough matrix resins for graphite composite applications, has published over 20 papers, and has several patents on adhesives and composite resins. He is presently a Project Leader in Adhesives at the Hercules Research Center. 

S. Soyles, D.A. Dinga, G.P. Glass, J.E. Dynamic Uniaxial Extensional Viscosity. Response in Spray Applications, Polymers as Rheology Modifiers, ACS 462 (1991)... 

Van Oene, H., in Polymer Blends, Rheology of Polymer Blends and Dispersion (D. R. Paul and S. Newman, eds.). Academic Press, New York (1978), Vbl. 1, pp. 296-352. Plochocki, A P., Polyolefins blends rheology, melt mixing and applications, in Polymer Blends (D. R. Paul and S. Newman, eds.). Academic Press, New York (1978), Vol. 2, pp. 319-368. 

Polymer solutions (i.e., polymers dissolved in low molecular weight solvents) are widely used in industrial compoimds of varying complexity. Synthetic hydrocarbon elastomers are often marketed as oil-extended rubber , which are solutions of the basic elastomer with hydrocarbon mineral oils. Polyvinyl chloride is often marketed in a plasticized form, which are solutions involving low molecular weight esters. Many additives dissolve in polymers forming polymer solutions. In this chapter, we consider the fundamental thermodynamics and rheology of polymer solutions as well as important applications. 

Acrylic polymers have the advantage that they can be formulated to be inherently tacky. However, for certain applications it may be desirable to adjust the rheological properties of the PSA beyond what can be obtained by selecting the right polymer composition and crosslink density. 

The dry adhesive films on the two substrates to be joined must be placed in contact to develop adequate autoadhesion, i.e. diffusion of polymer rubber chains must be achieved across the interface between the two films to produce intimate adhesion at molecular level. The application of pressure and/or temperature for a given time allows the desired level of intimate contact (coalescence) between the two adhesive film surfaces. Obviously, the rheological and mechanical properties of the rubber adhesives will determine the degree of intimacy at the interface. These properties can be optimized by selecting the adequate rubber grade, the nature and amount of tackifier and the amount of filler, among other factors. 

Silicone adhesives are generally applied in a liquid and uncured state. It is therefore the physical and chemical properties of the polymers, or more precisely of the polymer formulation, that guide the various processes leading to the formation of the cured silicone network. The choice of the cure system can be guided by a variety of parameters that includes cure time and temperature, rheological properties in relation with the application process, substrates, the environment the adhesive joints will be subjected to and its subsequent durability, and of course, cost. 

---