Thermo-mechanical properties of poly ε-caprolactone/poly l-lactic acid blends: Addition of nalidixic acid and polyethylene glycol additives

• Loading of PLLA caused total eradication of the elongation at break of PCL matrix.
• PCL–PLLA blends are thermally stable at 200 °C for 2 h making extrusion viable.
• Increasing PLLA content decreased the Melt Flow Index and increased the viscosity.
• Crystal size was more controlled with increasing concentration of PLLA.
• Addition of nalidixic acid to the blends caused formation of dendritic crystals.

The search for ideal biomaterials is still on-going for tissue regeneration. In this study, blends of poly ε-caprolactone (PCL) with poly l-lactic acid (PLLA), nalidixic acid (NA) and polyethylene glycol (PEG) were prepared. Mechanical and thermal properties of the blends were investigated by tensile and flexural analysis, DSC, TGA, WXRD, MFI, BET, SEM and hot stage optical microscopy. Results showed that the loading of PLLA caused a significant decrease in tensile strength and almost total eradication of the elongation at break of PCL matrix, especially after PEG and NA addition. Increased stiffness was also noted with additional NA, PEG and PLLA, resulting in an increase in the flexural modulus of the blends.Isothermal degradation indicated that bulk PCL, PLLA and the blends were thermally stable at 200 °C for the duration of 2 h making extrusion of the blends at this temperature viable. Morphological study showed that increasing the PLLA content and addition of the very low viscosity PEG and powder NA decreased the Melt Flow Indexer and increased the viscosity.At the higher temperature, the PLLA begins to soften and eventually melts allowing for increased flow and, coupling this with, the natural increase in MFI caused by temperature is enhanced further. The PEG and NA addition increased dramatically the pore volume which is important for cell growth and flow transport of nutrients and metabolic waste.

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