Abstract
AimsA simple and easy optical method is proposed for the determination of glass transition temperature (Tg) of polymers.Methods & ResultsTg was determined using the technique of microsphere imaging to monitor the variation of the refractive index of polymer microsphere as a function of temperature. It was demonstrated that the method can eliminate most thermal lag and has sensitivity about six fold higher than the conventional method in Tg determination. So the determined Tg is more accurate and varies less with cooling/heating rate than that obtained by conventional methods. The most attractive character of the method is that it can simultaneously determine the Tg of several polymers in a single experiment, so it can greatly save experimental time and heating energy.ConclusionThe method is not only applicable for polymer microspheres, but also for the materials with arbitrary shapes. Therefore, it is expected to be broadly applied to different fundamental researches and practical applications of polymers.
Highlights
The glass transition temperature (Tg) is one of the most important properties that define a polymer
Many physical properties change profoundly at the glass transition temperature, including the coefficient of thermal expansion, heat capacity, refractive index, mechanical damping, and electrical properties which are important for the applications of materials in chemistry, food, pharmacy and optics, etc.[2,3,4,5]
Thermal lag depend on the size and shape of the sample, due to the low thermal conductivity of common polymers, large sample size will increase the temperature lag, so the Tg determined by Differential scanning calorimetry (DSC) has a greater variation with cooling/heating rate in which larger size sample is used and the samples are usually not symmetry in shape
Summary
The glass transition temperature (Tg) is one of the most important properties that define a polymer. Another conventional thermal analysis technique for Tg measurement is thermo-mechanical analyzer (TMA), which measures the volume or modulus change of the sample It is more sensitive than the methods detecting heat capacity change[8], but the result of Tg determined by this method is influenced by the size and surface roughness of the samples. An optical method based on ellipsometry can be used to measure Tg and physical aging with the inflection in a plot of refractive index versus temperature[9,10] This method can only measure thin or ultra-thin films; especially the result is dependent on the thickness of the film and cannot provide the bulk glass transition temperature. The thermal lag depends on the heating/cooling rate, and the sample mass and the thermal conductivity of both the sample and the equipment[11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
