Bor-Kuan Chen

Preparation of ductile PLA materials by modification with trimethyl hexamethylene diisocyanate

Polylactide (PLA) is biodegradable and has been useful in various biomedical applications. Since the majority of the biodegradable polymers in clinical use are rather stiff materials that exhibit limited extendibility with low elongation at break values, the physical and mechanical properties of PLA must be improved to allow for more biomedical applications. Poly(ester-urethane) structure polymer materials were prepared; PLA was reacted with a small amount of trimethyl hexamethylene diisocyanate to obtain ductile PLA with markedly improved mechanical properties. Elongation at break was increased by more than 20 times while maintaining relatively high tensile stress when compared to pristine PLA. Impact resistance (notched) improved 1.6 times. Thus, the modified PLA biodegradable polymers presented here may have greater application as a biomedical material due to its enhanced mechanical properties.

Naphthalene containing polyimide nanocomposites hybrid with organo-modified montmorillonite

To improve the thermal and mechanical properties of polyimides, a nanocomposite of naphthalene containing polyimide (PI) was hybridized with Montmorillonite (MMT). The PI was synthesized from a diamine, 2,7-bis (4-aminophenoxy) naphthalene and polymerized with a 3,3’,4,4’-benzophenone tetracarboxylic dianhydride via thermal imidization. PI-MMT nanocomposites were then prepared from a DMAc solution of poly(amic acid) precursor and a DMAc dispersion of MMT which were organo-modified with various amount of n-dodecylamine. Characterization results demonstrated that the introduction of a small amount of MMT (up to 5%) led to enhanced thermal stability and mechanical properties of PI. The 5% weight loss temperature in N2 was increased by 46oC in comparison to pristine PI with an organoclay content of 5%. The CTE and dielectric constant were decreased. However, at organoclay contents higher than 5% these properties were reduced because the organoclay was poorly dispersed and resulted in aggregate formation.