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Mr Selected Application Recommendations Radioactive Materials Polymer -matrix composites in general have a very low neutron cross-section capture efficiency. Therefore, they are very well-suited to the containment of radioactive materials, even at relatively high levels of radioactivity. Testing of uncured DION® 382 by Atlas Chemical Laboratories demonstrated that this resin is highly resistant to molecular weight changes at dosages up to 15 million rads. Extrapolations based on this study estimate that DION® 382 may be able to withstand 50 to 100 million rads. For reference, the lethal radiation dose is about 400 rads. Given the hazardous nature of radioactive materials, testing is recommended before actual use in high radiation environments. Sodium Hydroxide and Alkaline Solutions Alkaline solutions can attack the resin, usually by hydrolysis of any ester groups. Glass fibers and other silica based materials can also be attacked or digested. This leads to a very characteristic type of wicking and blistering, as well as fiber blooming. Dilute sodium hydroxide is often more aggressive than the more concentrated solutions. This relates to the fact that NaOH is a very strong base, but at higher concentration there is equilibrium between dissolved and solid phase NaOH, which reduces the caustic effects. Epoxy based vinyl esters and bisphenol-A based polyesters display exceptional resistance to caustic. Even though novolac based vinyl esters are well- regarded for excellent corrosion and thermal resistance in many applications, it is often observed that novolac based resins can show somewhat inferior caustic resistance. Laminates based on novolac vinyl esters exposed to caustic have a tendency to develop a pinkish color incipient to failure. It is speculated this is due to formation of phenolates from the novolac structure. There is widespread belief that it is advisable to use synthetic surfacing veils versus C -glass in caustic applications. However, controlled laboratory tests usually reveal no clear-cut or distinct advantages to a synthetic veil, and there is a long history of use of C -veil in alkaline environments. The synthetic veil allows an increased resin content at the surface to ostensibly afford more protection. On the other hand, the resin rich areas can make the surface more prone to cracking and can, at times, present more fabrication difficulties.