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The polyol is a major component in polyurethane formulations and therefore introducing to the formulation recycled polyol (obtained during decomposition process) allows decreasing the usage of pure petrochemical components. In this work, thermoplastic polyurethanes were prepared using various mixtures of a petrochemical macrodiol poly(ethylene-butylene adipate)diol (PEBA) and a recycled glycolysate intermediate, called glycolysate polyol, in a two-step synthesis procedure with 4,4-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD). The glycolysate polyol was obtained during glycolysis process of polyurethane elastomer using ethylene glycol as a decomposing agent. Glycolysate polyol showed a higher hydroxyl value (199 mg KOH g −1 ) and glass transition temperature (Tg, −50.1 °C) than pure macrodiol (PEBA). The maximum concentration of glycolysate polyol was 25 wt% over the total polyol. Synthesized polyurethanes had similar chemical structure compared to the polyurethane synthesized without glycolysate polyol, confirmed by Fourier transform infrared spectroscopy. On the one hand, higher contents of glycolysate polyol resulted in higher T g and a slightly lower thermal stability analyzed by thermogravimetric analysis. On the other hand, improved thermomechanical and mechanical properties were obtained in polyurethanes with partial replacement of pure macrodiol. [ABSTRACT FROM AUTHOR]

In this paper, sustainable thermoplastic polyurethanes (TPU) were synthesized from a recycled bis(2-hydroxyethyl) terephthalate (BHET) monomer obtained by glycolysis of marine polyethylene terephthalate (PET) litter and from a renewable castor oil-derived macrodiol. The BHET was obtained in a closed reactor at 220 °C and a short time reaction of 30 min. The TPUs with different BHET contents, ranging from 10 to 30% by weight, incorporated as chain extenders, were synthesized in bulk without catalysts. In all polyurethanes, the content of the biobased macrodiol was at least 45 wt%. TPUs with commercial BHET have also been synthesized for comparative purposes. The BHET monomer produced and the TPUs synthesized were extensively characterized. The TPUs synthesized in this work, in which at least three quarters of their components are biobased and recycled, showed an interesting combination of thermal, thermomechanical and mechanical properties. [ABSTRACT FROM AUTHOR]

In this work polyurethane elastomers were synthesised by using different mixtures of a petrochemical and glycerolysate polyols and 4,4-diphenylmethane diisocyanate (MDI). Glycerolysate polyol was produced from polyurethane foam decomposition using crude glycerine as a decomposition agent. The structure and thermal properties of obtained semi-product were similar to the polyol used in the synthesis of original foam. Glycerolysate polyol was incorporated into polyurethane formulation as soft segment (SS). Since polyol is one of the major component in polyurethane system (>70%) introducing recycled components leads to lowering of consumption of petrochemicals and valorisation of recycled products. Polyurethane elastomers containing up to 16.4 wt.% of glycerolysate polyol were synthesised, soluble in dimethylformamide (DMF) up to ca. 12 wt.%. The effect of glycerolysate polyol content on the structure and properties was analysed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and mechanical tests. Thermal properties did not worsen after using glycerolysate into polyurethane formulation. A slight increase in glass transition temperature is observed with the incorporation of glycerolysate polyol. Elastic modulus, tensile strength and hardness of polyurethane elastomers increased with recycled polyol content. Moreover they showed high elongation at break values. [ABSTRACT FROM AUTHOR]

Biobased crosslinked polyurethanes were synthesized and characterized as shape-memory polymers. Both the macrodiol and the diisocyanate were derived from renewable sources; the first one from castor oil, and the second one from l -lysine amino acid. The influence of component molar ratios, crosslink density and maximum elongation on the shape-memory properties was analyzed. The thermal analysis showed that polyurethanes were microphase separated. Though the study of the shape-memory properties, it was seen that shape-memory was influenced by crosslink density. A higher crosslink density led to a greater shape recovery, since crosslinks are the responsible for memorizing the shape of the material. With the increase of maximum elongation, both shape fixity and recovery decreased due to higher amount of crosslink net points were broken. Moreover, the synthesized polyurethanes showed its potential to be used in biomedical applications, according to the preliminary in vitro cytotoxicity assays. [ABSTRACT FROM AUTHOR]

In this work, segmented biopolyurethanes with thermally-activated shape-memory properties were synthesized and characterized. All the employed starting materials were derived from renewable sources. The macrodiol, which forms the hard segment, was derived from castor oil, while the soft segment was composed of a diisocyanate from the amino acid lysine, as well as a chain extender from corn sugar. The effect of component molar ratios and switching temperature on the shape-memory behavior was analyzed. Thermal analysis of the biopolyurethanes shows a phase separated structure. Programming at different temperatures resulted in shape-memory effects, in which shape fixation and recovery could be attributed to different phases of the physical networks. Increasing the switching temperature, shape fixity values improve, however, it has no significant effect on shape recovery values. In addition, preliminary in vitro cytotoxicity evaluation shows that the synthesized fully biobased biopolyurethane has a non-toxic behavior, showing its potential to be used in biomedical applications. [ABSTRACT FROM AUTHOR]

• TPU residues from livestock sector were mechanically recycled. • TPU waste was processed using traditional and advanced technologies. • Thermal and mechanical degradation was more severe as reprocessing cycles increased. • The filament obtained after a single processing stage was suitable for 3D printing. • Electrospun mats of continuous microfibers were directly obtained from TPU waste. In this work different ways to valorise discarded ear tags made of TPU from livestock sector were studied. This singular residue does not require separation from other plastics like other industrial and urbane wastes, which could contribute to simplify its management. Firstly, mechanical processing was carried out by several cycles of consecutive extrusion and injection processes. The material obtained in each process was characterized using different physical, chemical and mechanical characterization techniques in order to study the degradation as a consequence of processing cycles. Thereafter, suitable filaments for 3D printing were obtained and the effect of infill pattern in the mechanical properties of the printed pieces was investigated. Besides, an electrospun mat constituted by TPU waste microfibers was successfully obtained by electrospinning, and its morphology together with superficial and mechanical properties were characterized. Results showed that these applications were suitable options to valorise TPU waste consisting of discarded ear tags. [ABSTRACT FROM AUTHOR]

A commercial kraft lignin (k-lignin) was successfully functionalized by means of the reaction of an isocyanate group from isophorone diisocyanate (IPDI) with hydroxyl groups present in lignin (k-IPDI), for their further incorporation in a flexible polyurethane foam (PUF) formulation. The functionalization was confirmed by FTIR and 13 C NMR, as well as by the OH number determination. It was observed that approximately half of the hydroxyl groups present in k-lignin were functionalized. Afterwards, two series of PUF containing 3, 5 and 10% of k-lignin and k-IPDI were prepared by one-shot free rise polymerization. It was observed that the presence of unmodified lignin decreased the reactivity of the system, yielding to longer foaming stages that required the addition of more catalyst to the system. Apart from that, more rigid foams were obtained with k-lignin than with k-IPDI, as it was observed by DSC and compression force deflection (CFD), which values reflected that the presence of k-IPDI contributed to the formation of more flexible foams. It was also found that the functionalization of lignin contributed to a higher chemical attachment of the lignin to the polyurethane matrix as it was observed by lignin extraction experiments. This chemical attachment was reflected on the stress-strain curves which showed that k-lignin containing foams had higher elastic modulus and higher ability to absorb energy than k-IPDI containing ones, which resulted to be more soft and flexible. [ABSTRACT FROM AUTHOR]

A mat of fibers with shape memory effect is obtained using commercially available components and a simple electrospinning process. For obtaining this goal, a blend of diglycidyl ether of bisphenol A (DGEBA) and Polycaprolactone (PCL) is electrospun and the obtained mats are cured by UV radiation, avoiding the melting of the PCL component. The cationic photoinitiator based on iodonium salts, used for the first time in the electrospinning process, increases the solution conductivity and consequently the spinnability of the blend. The obtained mats show shape memory properties through several cycles, with shape fixity ratios that range from 95 to 99% and shape recovery ratios of between 88 and 100% respectively. [ABSTRACT FROM AUTHOR]