Epoxies repeat unit structure

Problem 3.19 Calculate an estimate of the solubility parameter for the epoxy resin DGEBA (diglycidyl ether of bisphenol A) having the repeat unit structure as shown below and density 1.15 g/cm. ... 

Epoxy cured silicones were developed to be photo initiated rather than thermally cured [54]. The chain length of these materials ranges to 200 monomer repeat units, but the majority component of most formulations is significantly shorter. The structure of a typical base polymer is shown in Fig. 4. The chain can be terminal and/or pendant functional, with degree and type of epoxy function-... 

The analysis of epoxy resins has been a particular challenge for the polymer chemist because of the complexity of the repeating units. The multitude of comonomers, the number and type of initiators, the variety of possible polymerization reactions, the insoluble nature of the product and the susceptibility of the network to hydrolysis and other types of chemical attack. Consequently there has been little knowledge of the structural basis of the physical, chemical and ultimate mechanical properties of the epoxy resins. However, it is essential that knowledge of the structures and curing processes be obtained in order to optimize the performance of the epoxy resins. 

Conventional (spectroscopic) analysis techniques are also readily applied to determine structural details (e.g., the epoxy ring and the repeat unit) and can also be applied to determine the degree of polymerization, particularly where the poor solubility of the oligomer may hamper solution-based techniques. Mertzel and Koenig presented a thorough spectral characterization of EPON 828 (a commercial grade of DGEBA). 

The calculated Tg-value of a linear polymer with this repeating unit is 321 K. The contribution of two crosslinks is 82 K. Hence, the calculated Tg-value for the resin system A/ HHPA system is 321 K + 82 K 403 K. The measured Tg-value was 399 K. The Tg-values of five other epoxy resin systems were calculated (and measured) in the same way, all results are listed in Table 7.5. It is important to realise that the used structures are idealised structures. Every deviation from this ideal network structure will lower the experimental Tg-value. Thus, the calculated Tg-values will in general be equal or higher than the measured Tg-values. This was confirmed for the six systems investigated. 

The maximum equilibrium water saturation of a cured epoxy system (resin system A/HHPA, see 7.2.3) was calculated succesfully using these new molar water content values. As repeating unit was recognised for this three dimensional network structure (see 7.2.4) ... 

When the number of repeating units in a polymer chain is low, that is when the molecular weight of the polymer is low (2000-10000 g mol ), the polymer is defined as a resin, provided it possesses sufficient numbers of active sites in its structures for chemical cross-linking to occur. The resins can form three-dimensional network structures if sufficient external energy (heat/light/radiation) is applied, with or without the use of any other chemical(s) in their finished state. They are free flowing materials of low viscosity. Polyester resins, epoxy resins, and polyurethane resins are examples of this type of polymer. This book contains descriptions of the different types of resins derived from various vegetable oils. 

The single-ion conductor, PAGSOa Na (m/n = 0.4 or 1.0, in which m and n are the number of siloxy units in the structure), was made by consecutive hydrosilylation of PHMS with AM PEG and allyl glycidyl ether. The neutral polymer was sulfonated with aqueous NaHSOa, which quantitatively converted the epoxy group into -CH(0H)CH2S03". Excess NaHSOa was removed by repeated ultrafiltration of the polymer solution with a cutoff membrane having a Mw of 1000. The poly sulfonate was azeotropically dried with benzene and finally in vacuum at 50 °C for several days. 

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