Question

you are given a sample of polymer; it is not obvious if it is amorphous, semi-crystalline, crosslinked,filled or not filled. a) explain the concepts of how you would determine the tg (glass transitiontemperature). will it also necessarily have a tm (melting temperature)? explain how tm would bedetermined. b) your manager asks you to use this polymer for a product that would typically be usedabove tg and in a humid environment. what technical concerns do you need to explain to yourmanager so that they fully understand any possible risks?

Answer 1

a. Dimensional instability: The polymer may undergo significant swelling or warping due to moisture absorption.

b. Hydrolysis: The polymer chains may break down due to prolonged exposure to moisture, affecting its mechanical properties.

c. Environmental stress cracking: The combined effects of moisture and stress can lead to cracking in the polymer.

d. Microbial growth: The moist environment may promote the growth of microorganisms, potentially degrading the polymer.

Determining the glass transition temperature (Tg) and melting temperature (Tm) of a polymer sample is crucial for understanding its behavior and suitability for various applications.

a) Determining Tg:

Differential Scanning Calorimetry (DSC): Heat the polymer sample at a controlled rate while monitoring heat flow. Tg is identified as a step change in heat flow.

Thermomechanical Analysis (TMA): Monitor the dimensional changes of the polymer sample as it is heated. Tg is observed as a sudden change in slope.

b) Determining Tm:

DSC: Similar to Tg determination, Tm is identified as an endothermic peak in the heat flow curve.

Polarized Light Microscopy (PLM): Observe the polymer sample under a microscope as it is heated. Tm is characterized by the disappearance of crystalline birefringence.