DOST Balik Scientist Dr. Caldona: How to Make Polymeric Materials ‘Speak’
by Faith P. Macatangay
“You can’t talk about materials without talking about polymers. Now is the polymer age.” – Dr. Eugene B. Caldona
A polymer is any natural or synthetic large molecule made by repeating small molecules called monomers. Polymerization is the process that links monomers together using heat and pressure.
We all use polymers - in fact, a famous example of these are the plastics that we use daily.
Plastic is a synthetic polymeric (made of polymers) material derived from crude oil and natural gas. Plastics became the name of polymers because of their booming demand across almost every sector, including packaging, building and construction, consumer products, transportation, and industrial machinery.
The techniques for measuring polymers' properties were the center of DOST Balik Scientist Dr. Caldona’s seminar entitled ‘Conventional and Modern Approaches to Characterizing Polymeric Materials’ on July 12, 2023.
In purchasing polymers to be used, Dr. Caldona shared that researchers must consider fundamental properties such as molecular weight and distribution. The minimum molecular weight for good physical and mechanical properties for the most important polymers is 25,000 grams per molecule. In measuring molecular weights, he highlights the commonly used Gel Permission Chromatography (GPC) analysis and the detectors used in its system.
Polymers have other properties that influence their characteristics. Making polymers ‘speak’ is like asking them what their properties are so that they can be understood and used in appropriate applications.
Crystallinity is one of their properties. It refers to the alignment of molecular chains, which influences the hardness of polymers. X-ray diffraction (XRD) can determine a sample's degree of crystallinity.
Chemical structure is another property of polymers. Dr. Caldona shared some spectroscopic techniques to probe the chemical structures of polymers: infrared (IR) spectroscopy to measure the interactions between molecules and IR light; Surface-Enhanced Raman Scattering (SERS) spectroscopy for finding the functional groups of atoms or bonds that are not seen using IR spectroscopy; and X-ray photoelectron spectroscopy (XPS) to identify the quantitative atomic composition and chemistry.
The behavior of polymers under controlled temperature programs is also part of a better understanding of polymer performance. Thermal analysis techniques include
thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA measures the changes of sample mass with temperature or time under programmed
temperature. DSC, on the other hand, measures the energy absorption of a sample as it is subjected to a specified thermal profile.
The resource person, Dr. Eugene B. Caldona, discusses to the onsite and online participants.
According to Dr. Caldona, “in terms of resistance to fracture, it is always very useful to fabricate polymer composites for demanding applications.”
The resistance to fracture of polymers is comparable to that of metals, ceramics, and composites. Other mechanical behaviors, such as strength and toughness, can be increased by incorporating different materials into polymers, such as composites and rubber.
The DOST Balik Scientist further shared that the relationship between the change in mechanical properties and temperature of the polymer can be determined using thermomechanical characteristics analysis (TMA). Rheology, meanwhile, measures a material's flow behavior through an oscillatory test mode.
In summary, the discussion imparts to the participants that performing the recommended techniques to assess the characteristics of polymers is an advantage in synthesizing or fabricating polymeric materials.
This seminar was the third of the five-part seminar series of Dr. Caldona about materials engineering. The seminars were in connection with Dr. Caldona’s engagement with the DOST-Metals Industry Research and Development Center as a DOST Balik Scientist.
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