Abstract
The aim of this study is the analyze the structure of branched polyurethanes based on synthetic poly([R,S]-3-hydroxybutyrate) and their blends with biopolymers and montmorillonite. The properties which would predict the potential susceptibility of these materials to degradation are also estimated. Fourier-transform infrared spectroscopy with attenuated total reflection analysis shows that poly([d,l]-lactide) is on the surfaces of polyurethanes, whereas chitosan and starch are included inside the blend network. Atomic force microscopy images have shown that the surfaces of investigated samples are heterogenous with the formation of spherulites in case of pure polyurethanes. The presence of biopolymers in the blend reduced the crystallinity of polyurethanes. Thermal stability of blends of polyurethanes with poly([d,l]-lactide) and polysaccharides decreased in comparison to pure polyurethanes. Although the tensile strength is reduced after the blending of polyurethanes with biopolymers, the elongation at break increased, especially in the case of polyurethane/poly([d,l]-lactide) blends. The presence of polysaccharides in the obtained blends caused the significant reduction of contact angle after one minute from water drop immersion. This hydrophilizing effect is the highest when montmorillonite has been incorporated into the chitosan blend. The estimated properties of the obtained materials suggest their potential sensitivity on environmental conditions.
Highlights
Taking into consideration the fact that undegradable polyurethane (PUR) waste influences the natural environment, it is advisable to find a solution to this problem
Branched polyurethanes with 10 and 20 wt.% of poly([R,S]-3-hydroxybutyrate) in soft segments were blended with chitosan, montmorillonite, starch and poly([d,l]-lactide)
ATR-Fourier-transform infrared spectroscopy (FTIR) analysis has shown that poly([d,l]-lactide) is on the surface of blends, whereas other additives of blends are inside the polyurethanes network
Summary
Taking into consideration the fact that undegradable polyurethane (PUR) waste influences the natural environment, it is advisable to find a solution to this problem. Polyurethane modification using natural components seems to be the most reasonable one. It is difficult to replace synthetic polymers with natural equivalents due to typically worse properties of such materials, especially in terms of mechanical properties. Introducing the natural compounds into a polymer structure or polymer network means the properties of pure polymers could be preserved while the material will gradually degrade at the end of the life cycle. Natural substrates usually used for polyurethanes modification are vegetable oils, polysaccharides, proteins, plants fibres, poly(hydroxy acids) and poly(lactide acid) [1,2,3]. The presence of chitosan (Ch) and Polymers 2020, 12, 16; doi:10.3390/polym12010016 www.mdpi.com/journal/polymers
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