Thermosetting polymers systems

In this book I have confined discussion to those polymeric materials which are cured by chemical reaction and which have found widespread application in the construction industry. As such, the book covers materials based on epoxies, polyurethanes, silicones, polysulphides, alkyds and polyesters. In addition, there is a chapter on hybrid polymer systems and one on acrylics. It is true that acrylic emulsions are not strictly thermosetting polymer systems, but their widespread use and importance made their exclusion difficult. These materials find use as coatings, sealants, adhesives, grouts, flooring compounds, repair compounds and waterproofing agents. 

Poranski, Jr., C.F., Moniz, W.B., Birkle, D.L., Kopfle, J.T., and Sojka, S.A., Carbon-13 and Proton NMR Spectra for Characterizing Thermosetting Polymer Systems 1. Epoxy Resins and Curing Agents", Naval Research Laboratory Report 8092, Washington, D.C., 1977. 

A thermoset polymer system with one or more epoxide groups in it, used mainly as matrices in composites or as adhesives. Epoxides can be cured by amines, alcohols, phenols, carboxylic acids, etc. 

Chem. Descrip. Decabromobiphenyl oxide CAS 1163-19-5 EINECS/ELINCS 214-604-9 Uses Flame retardant for thermoplastic, elastomeric, and thermoset polymer systems incl. HIPS, PBT, ABS, nylons, PP, PC, PET, polybutylene, PVC, LDPE, EPDM, unsat. polyesters, epoxies, flexible PU foam, wire insulafion (polyolefin, TPE, PU elastomer, polyamide/polyimide), adhesives, coatings, textiles... 

Upadhyaya, P., Roy, S., Haque, M.H., Lu, H. Influence of nano-clay compounding on thermo-oxidative stabihty and mechanical properties of a thermoset polymer system. Compos. Sci. Technol. 84, 8-14 (2013)... 

Matloka, P. R. Kean, Z. Wagener, K. B., Chain Internal/Chain End Latent Crosslinking in Thermoset Polymer Systems. J. Polym. Sci., Part A Polym. 

Titanates are currently used with calcium carbonate to reduce the viscosity of filled thermosetting polymer systems. 

Th rmOS0tS. Structure determination in thermoset polymer systems can at times be problematic because of their relative insolubilities and large molecular weights. Direct observation of structural details by afm has been advantageous for such systems, describing both inherent material properties as well as the impact of processing steps on final structure properties. 

In fact, RIM was the first plastic to be approved for bumper fascia in North America to meet the low-temperature crashworthiness demanded by some OEMs. Unfortunately, due to process complexity, RIM could not be fabricated at a high enough rate to meet the demands of large car platforms. Faster cycle time for part production is delimited by the speed of curing chemistry and the ability of the resin to flow into molds. Furthermore, the automotive industry wanted to move away from the use of thermoset polymer systems that cannot be remelted. This attribute of thermosets was labeled by the industry as non-recyclable, and the industry made room for other thermoplastics such as TPO that can be remelted. Reaction-injection-molded parts are made from urethane epoxies, polyesters, and polyamides. A study of cost versus performance reported that RIM gives the best cost-performance characteristic for composite materials and is competitive with steel. ... 

Industrial minerals are used in both thermoplastic and thermosetting polymer systems. 

In this section we examine some examples of cross-linked step-growth polymers. The systems we shall describe are thermosetting polymers of considerable industrial importance. The chemistry of these polymerization reactions is more complex than the hypothetical AB reactions of our models. We choose to describe these commercial polymers rather than model systems which might conform better to the theoretical developments of the last section both because of the importance of these materials and because the theoretical concepts provide a framework for understanding more complex systems, even if they are not quantitatively successful. 

Stabilization of the Cellular State. The increase in surface area corresponding to the formation of many ceUs in the plastic phase is accompanied by an increase in the free energy of the system hence the foamed state is inherently unstable. Methods of stabilizing this foamed state can be classified as chemical, eg, the polymerization of a fluid resin into a three-dimensional thermoset polymer, or physical, eg, the cooling of an expanded thermoplastic polymer to a temperature below its second-order transition temperature or its crystalline melting point to prevent polymer flow. 

The final physical properties of thermoset polymers depend primarily on the network structure that is developed during cure. Development of improved thermosets has been hampered by the lack of quantitative relationships between polymer variables and final physical properties. The development of a mathematical relationship between formulation and final cure properties is a formidable task requiring detailed characterization of the polymer components, an understanding of the cure chemistry and a model of the cure kinetics, determination of cure process variables (air temperature, heat transfer etc.), a relationship between cure chemistry and network structure, and the existence of a network structure parameter that correlates with physical properties. The lack of availability of easy-to-use network structure models which are applicable to the complex crosslinking systems typical of "real-world" thermosets makes it difficult to develop such correlations. 

Membranes with extremely small pores ( < 2.5 nm diameter) can be made by pyrolysis of polymeric precursors or by modification methods listed above. Molecular sieve carbon or silica membranes with pore diameters of 1 nm have been made by controlled pyrolysis of certain thermoset polymers (e.g. Koresh, Jacob and Soffer 1983) or silicone rubbers (Lee and Khang 1986), respectively. There is, however, very little information in the published literature. Molecular sieve dimensions can also be obtained by modifying the pore system of an already formed membrane structure. It has been claimed that zeolitic membranes can be prepared by reaction of alumina membranes with silica and alkali followed by hydrothermal treatment (Suzuki 1987). Very small pores are also obtained by hydrolysis of organometallic silicium compounds in alumina membranes followed by heat treatment (Uhlhom, Keizer and Burggraaf 1989). Finally, oxides or metals can be precipitated or adsorbed from solutions or by gas phase deposition within the pores of an already formed membrane to modify the chemical nature of the membrane or to decrease the effective pore size. In the last case a high concentration of the precipitated material in the pore system is necessary. The above-mentioned methods have been reported very recently (1987-1989) and the results are not yet substantiated very well. 

In principle, molecular sieve carbons (MSC) can be achieved by the pyrolysis of thermosetting polymers such as polyvinylidene chloride, polyfurfuryl alcohol, cellulose, cellulose triacetate, polyacrylonitrile and phenol formaldehyde (Koresh 1980). An example is given by Trimm and Cooper (1970,1973) for the preparation of MSC (mixed with metallic compounds) for catalyst systems. A mixture of furfuryl alcohol, platinum oxide and formaldehyde was heated to 40°C and additional formaldehyde was added to ensure the... 

Cole reviews the nse of Raman spectroscopy to monitor the curing of different thermoset composite polymer systems, thongh he cautions that it is not suitable for certain materials [215]. Cruz et al. studied the effect of elevated pressure on the cure rate and the degree of cnre of unsaturated polyester and other thermoset materials [216,217]. The approach worked well, though the experimental set up required addi-... 

This paper rerports an investigation of the yield behavior of several amine and anhydride cured DGEBA resin systems. The Argon theory is used to assess the controlling molecular parameters from the experimental results. Such parameters are then compared with the known chemical structures of the resins. The mechanisms of plastic flow in thermoset polymers such as epoxies is demonstrated. 

Another type of thermoset polymers is based on epoxy monomers. These thermosets are cured by use of a two-component system or by photo initiators. Disadvantages of epoxies are high water uptake in service and polymerization shrinkage (22). 

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