Optimization of Structure of Soft Block for Design of Adaptive Polyurethanes

Abstract

A synthesis of new di-and triblock polyurethane thermoplastic copolymers containing different mass ratio of two crystallizing blocks - poly (1,4-butylene glycol) adipate and poly-ε-caprolactone diols was developed. Using combination of danamometric analysis, IR-spectroscopy, differential scanning calorimetry and X-ray diffraction, the effect of the soft block composition and crystallization conditions on crystal structure and thermal behavior of the obtained polymers have been studied. For the triblock copolymers we have shown a possibility of control the kinetics of material hardening and final mechanical characteristics due to the mutual influence of polydiols during crystallization. In the result, the second crystallizing component allows to control amount, structure and quality of crystalline domains in polyurethanes by variation of crystallization conditions.

The Influence of Long-Time Storage on the Structure and Properties of Multi-Block Thermoplastic Polyurethanes Based on Poly(butylene adipate) Diol and Polycaprolactone Diol

“…Earlier, we have observed similar complex thermal behavior during long-term storage for semi-crystalline polyurethane-urea systems [ 23 ]. Interestingly, in contrast to TPU-381(PBA) and TPU-382(PCL) the crystallization rates of PBA and PCL become comparable due to slow phase separation of the blocks in the initial state [ 25 ]. Parallel formation of two types of crystallites slows crystallization of PBA but from on the other side accelerates phase separation because of high chain mobility of the amorphous polymer.…”

“…In the FTIR spectra of all samples ( Figure 5 ) one can see absorption bands corresponding to stretching and bending vibrations of the -NH group ( υ NH ~3500–3200 cm −1 and δ NH ~1580–1490 cm −1 ) and stretching vibrations of the carbonyl group ( υ C=O ~1800–1640 cm −1 ), which characterize the formation of urethane bonds ( Figure S1 ). The presence of the corresponding bands in the FTIR spectra indicates the formation of inter-urethane bonds in phase-separated morphology of TPU [ 25 , 38 ]. The peaks at 2865 cm −1 and 2939 cm −1 are characteristic of CH 2 groups of the soft segment ( Figure S1 ).…”

“…Synthesis of multi-block thermoplastic polyurethane (TPU) was carried out by the three-stage method developed by us earlier [ 1 , 25 ]. Two crystallizing diols with similar molecular weight 2000 Da were used in different weight ratios PBA/PCL (in %) 100/0 for TPU-381(PBA); 0/100 for TPU-382(PCL) and 50/50 for TPU-383(PBA/PCL).…”

Nanocellulose-Based Thermoplastic Polyurethane Biocomposites with Shape Memory Effect

“…Diisocyanates of different types and structures can be used in the synthesis of TPU (Figure 4c) [11,15,106]. This allows the structure of rigid domains to be changed and, as a consequence, changes the mechanical and adaptive properties of the resulting material.…”

“…The hard segments provide the elasticity of the matrix that is required for shape recovery thanks to the presence of physical cross-links of hydrogen bonds. Improvement and modification of the adaptive properties of TPUs can be achieved either by changing the ratio of soft [10][11][12] and hard segments [1,13,14] or by introducing nanoscale fillers, such as silicon [2] or carbon nanoparticles [15][16][17]. In the last decade, researchers have been particularly attracted to nanoscale particles from natural sources to reinforce polymers or give them new functional properties.…”