INVESTIGATION OF MATERIALS AND METHODS OF EXTENDING THE SHELF LIFE OF POLYESTERS.
Abstract
The objective of this program was to extend the shelf life of burn-resistant polyester resins to 3 years at temperatures up to 70C without the loss of properties required for bare base applications. Prediction of 3-year shelf life on the basis of a one-year study made mandatory a rapid test procedure which could be extrapolated over extended periods of time. An accelerated test was developed to screen free-radical scavengers as stabilizers for two types of resins, the Hetron resins and Marco resins. Three classes of compounds showed promise as stabilizers in the accelerated tests, namely, phenols, quinones, and nitrophenols. The best individual stabilizers were tetrabromocatechol-cobalt octoate complex (formed in situ), picric acid, dinitrophenol, dinitrocresol, o-nitrophenol, and chloranil at concentrations of 0.5 to 1.0 mole %. The most promising additives were the tetrabromocatechol complex and the picric acid. Effects of the stabilizers on both the uncured and cured polyester resin properties and characteristics were found to be insignificant, while curing rates were lowered appreciably. Combinations of two peroxide catalysts and two additives (sodium methoxide and cobalt promoter) were found beneficial, and curing in the presence of the recommended combination stabilizer systems can be accomplished with excess peroxides to give about 90% of ultimate flexural strength in 2 to 4 hours. Tentative specifications are supplied for preparation, handling and storage of stabilized burn-resistant polyesters for bare base applications.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1968
- Accession Number
- AD0841290
Entities
People
- David A. Daniels
- Edwin W. Lard
- Eldon E. Stahly
- Michael Rock