Influence of Starch on the Structure–Properties Relationship in Polyethylene Glycol/Polycaprolactone Diol Polyurethanes

Improvements in the antithrombogenicity activity of biomaterials for cardiovascular applications are necessary to meet the demand for vascular grafts in the world. Zwitterionic compounds tend to be used due to their anti-fouling properties, which reduce platelet adhesions and protein absorptions. Therefore, in this research, potato starch (AL-N) and zwitterionic starch (AL-Z) (obtained by Williamson etherification) were included as fillers in polyurethane (PU) matrices from polycaprolactone diol (PCL), polyethylene glycol (PEG), pentaerythritol (PE) and isophorone diisocyanate (IPDI) in order to study their effect in terms of their physicochemical, mechanical and thermal properties. We conducted our evaluation using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), contact angle analysis, swelling behavior, thermogravimetric analysis (TGA), tensile/strain analysis, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS), dynamic mechanic analysis (DMA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The results showed that AL-N and AL-Z modified these properties, where AL-N improved tensile strength, and AL-Z increased the hydrophilicity of polyurethanes matrices; additionally, AL-N had interactions with the soft segments, and AL-Z had interactions with the hard segments. Finally, both fillers reduced the degree of crystallinity and did not affect the thermal stability of polyurethanes.

Effects of chain extender in biodegradable polyurethane foams

Molded flexible polyurethane (PU) foams were synthesized from a starch/petroleum based polyol, 2,4/2,6-toluene diisocyanate (TDI-80), using a one shot method with water as the blowing agent. The effects of chain extender type [starch (S series), diethanolamine (DEA, D series), glycerol (G series)] and content (0, 2, 5, 10 pphr) were extensively studied. The rate of foam formation, density, compression strength, glass transition temperature (Tg) and rubbery modulus of the foam increased with the addition and increasing content of extender. At the same extender content, DEA showed the highest of these properties, while starch showed the lowest. The rate of biodegradation in a buffer solution decreased with the addition of DEA and glycerol, due to the increased crosslinking density and hard segment content, but increased with starch, owing to its biodegradability.