Abstract
Poly(ε-caprolactone) (PCL) and poly(lactic acid) (PLA) blends were compatibilized by reactive blending and by copolymers formed during reaction in the solution. The reactive blending of PCL/PLA was performed using di-(2-tert-butyl-peroxyisopropyl)benzene (BIB) or dicumyl peroxide (DCP) as radical initiator. PCL-g-PLA copolymers were prepared using 1.0 wt. % of DCP or BIB via reaction in solution, which was investigated through a Fourier transform infrared spectrometry (FTIR) and nuclear magnetic resonance (NMR) in order to better understand the occurring mechanisms. The effect of different additions such as PCL-g-PLA copolymers, DCP, or BIB on the properties of PCL/PLA blends was studied. The unmodified PCL/PLA blends showed a sea-island morphology typical of incompatible blends, where PLA droplets were dispersed in the PCL matrix. Application of organic peroxides improved miscibility between PCL and PLA phases. A similar effect was observed for PCL/PLA blend compatibilized by PCL-g-PLA copolymer, where BIB was used as initiator. However, in case of application of the peroxides, the PCL/PLA blends were cross-linked, and it has been confirmed by the gel fraction and melt flow index measurements. The thermal and mechanical properties of the blends were also investigated by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and tensile strength.
Highlights
The preparation of innovative materials is associated with their continuous modification and improvement, thanks to which they may meet high application requirements
These results suggest that organic peroxides can promote the crystallization process of PCL, as confirmed by Xc(PCL), which increased to 36% for modified PCL/poly(lactic acid) (PLA) blends
The reference PCL/PLA blend, and compatibilized by PCL-g-PLA copolymers obtained in solution were completely soluble in chloroform, which proves that these blends did not show cross-linking
Summary
The preparation of innovative materials is associated with their continuous modification and improvement, thanks to which they may meet high application requirements. The most common methods of modification are blending and cross-linking of polymers [1,2,3]. Biodegradable polymer blends give a wide range of possibilities to obtain materials with properties that would not be possible using homopolymers without losing their biodegradability [4]. The final properties of polymer blends, achieved by physical mixing, may be disadvantageous or not observable at all. This is due to their thermodynamic incompatibility associated with low free energy mixing [5,6,7]. In order to successfully mix two incompatible polymers, improving their functional properties and broadening their use, it is necessary to introduce additional stimuli/factors, e.g., organic peroxides [8]
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