Hello,
I'm havaing difficulty understanding the relationship between crystalline properties and mechanical properties of polymers.
I'm compounding two biodegradable semi-crystalline polymer 1) PLA and 2)PBAT.
I analyzed DSC, TGA, XRD, and mechanical properties of above polymers and have a couple of questions.
1) Through XRD analysis, PLA turned out to be amorphous while PBAT has crystalline dimensions. but it is known that these two polymers are semi-crystalline polymers(both have melting point, crystallization point in DSC analysis). Then why PLA is amophous in XRD analysis?
2) According to the previous reports, high crystallinity of polymer results in high elastic modulus and tensile strength because of brittleness. However, i got an opposite result that amorphous PLA(from XRD) has significantly high elastic modulus (about 2000 MPa) showing high brittleness while crystalline PBAT(from XRD) has significantly low elastic modulus and high elongation properties.
It would be really thankful if you share clear references or solutions!
Thank you in advance!
Good day! May it be dedicated to increased interconnectivity of PLA flexible chains, that possibly create a network of interwined chains?
Hi Jisou Lyu ,
1) PLA can be amorphous or semi-crystalline depending on your processing method. For example, a semi-crystalline PLA pellets can be transformed to amorphous PLA compounds or products if the cooling rate is too fast and the polymer chains don't have enough time to arrange themself into ordered state.
2) PBAT is a co-polyester with a very low glass transition temperature (Tg), which is below 0 degree. This means that the polymer itself is very ductile in room temperature as polymer chains are quite flexible.
PLA, on the other hand, has a high Tg, being around 55-60 C degree. It means that the polymer is rigid at room temperature.
Best regards,
Cuong
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