The purpose of conditioning is to ensure the polymer chains are in a consistent state to ensure the testing is objective. The orientation, crystallinity, strength, and impact resistance of polymers can be easily influenced through conditioning.
Question: My company deals with polymer compounding and we have an testing lab. According to ISO 291, we are required to condition the multipurpose testing bar for 88 hours. Wish to ask what should we do if during the 88 hours, the condition went of the specification. Thank you.
My Response: The standards do provide allowance for deviation and minimum times for compliant conditioning. For example, most materials require the atmospheric pressure must be within spec for 88 hours, but many material classes require less than 88 hours for temperature conditioning, especially when drying or moisture removal is needed. For this reason, I recommend you verify the specific requirements for your material class. If the conditioning does go out of specification, you must begin measuring the conditioning time at the last point when conditions are in specification.
Additional Thoughts: Keep in mind, many companies will test samples under non ISO conditions for practical or comparative purposes, yet the results cannot be considered ISO or ASTM compliant and should not be reported as such. As a compounder, if your intention is to derive objective data for the customer, then you must follow the standards. You should also have a data recorder which records the temperature, relative humidity, and atmospheric pressure in case your results are disputed. For this reason, you should have a standard methodology for processing the test samples and keep accurate records of this as well.