GMW GMW15117 PDF

Note: Nothing in this standard supercedes applicable laws and regulations.

Note: In the event of conflict between the English and domestic language, the English language shall take precedence.

Purpose. Accurate and fast measure for degree of cure using thermal mechanical analysis intended for, but not exclusive of ethylene acrylic (AEM), fluorocarbon (FKM), hydrogenated nitrile butadiene rubber (HNBR), polyacrylate (ACM), and silicone (MVQ) elastomers. This procedure accommodates small to moderate size specimens with equipment available in most plant or independent test laboratories. As cure state increases, hysteresis decreases. Tan delta is a measure of hysteresis. As cure state increases, tan delta decreases. This procedure aids in the determination of optimum production part process conditions for new compounds; verification of process conditions for existing compounds; and analysis of suspect parts for degree of cure. No other uses are intended or recommended.

Foreword. This document describes a procedure for evaluating the state of cure of non-post cured or post cured elastomers. For non-post cured elastomers, a rheometry curve (e.g., Moving Die Rheometer) of the compound under evaluation is generated. At points along the curve (Tc 50, Tc 70, and Tc 90), specimens are removed and cooled to prevent further curing. Each Tc "x" specimen is tested using Dynamic Mechanical Analysis to find the tan delta (δ) value. The part specimen tan delta is measured and compared to the Tc "x" values taken at controlled points on the cure curve. For post cured elastomers, tan delta values are compared from known post cure conditioned specimen to verify if the unknown specimen was post cured. The results can confirm if the unknown was post cured for a sufficient time at the correct temperature.

Applicability.

Test new, unused, or assembled parts, not exposed to actual operating heat or fluids after assembly.

Parts from dynamometer durability, bench testing, field, warranty returns or consumer use are not to be evaluated.

The compound molder uses this procedure to setup optimum production part cure conditions as a reference, process verification, or when required for problem solving.

This procedure is relevant if the Dynamic Mechanical Thermal Analysis (DMTA) data produced can discriminate between reference specimen cure conditions.