Switch segment and halloysite nanotube role in the phase separation behavior of shape‐memory thermoplastic polyurethane

Abstract

Thermoplastic polyurethane consists of hard and soft segments. The difference in glass transition temperature and thermodynamic incompatibility of these segments results in phase separation and shape memory behavior. In this study, the effect of molecular weight of polyol and the amount of nanoparticles on the phase separation and shape memory behavior of polyurethane nanocomposites were studied. Polyurethane was synthesized using poly(tetramethylene glycol) with molecular weights of 1000 and 2000 g/mol, hexamethylene diisocyanate, and 1,4‐butanediol by step polymerization. The nanocomposites were synthesized through in situ method containing 1 and 2 wt% of nanoparticle. Phase separation and shape memory behaviors were studied using attenuated total reflectance‐Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, and atomic force microscopy analysis. The results indicated that higher molecular weight polyol with molecular weight of 2000 g mol−1 shows higher phase separation than the lower molecular weight sample. Also, the addition of nanoparticles results in an increased phase separation due to the halloysite nanotubes tendency to the hard segment. The shape fixity ratio (Rf) and shape recovery ratio (Rr) were in the range of 90% to 100% in all of the synthesized samples. By increasing the nanoparticles content, the shape fixity and shape recovery parameters were increased and decreased, respectively. The study of shape memory behavior also showed that the higher the polyol molecular weight, the better the nanocomposite shape memory behavior.

Thermoplastic polyurethane/multiwalled carbon nanotubes nanocomposites: Effect of nanoparticle content, shear, and thermal processing

“…Moreover, the presence of MWCNTs increased the melting temperature of the hard segments due to the higher phase separation and formation of more hard domains. The emergence of sharper melting peaks at higher temperatures due to higher phase separation has also been reported by Mohammadzadeh et al [30] for TPU/halloysite nanotubes (HNTs). With the increase in the MWCNT content up to 0.4%, the melting temperature and the enthalpy of the soft phase increased because of promoted phase separation.…”

Advanced Kolarik model for the modulus of a nanocomposite system reinforced by halloysite nanotubes and interphase zone

“…Many researchers have reported the improvement of thermo-mechanical and chemical properties of polymer HNT samples. [23][24][25][26][27][28][29][30][31][32] HNT can raise the fracture stiffness of epoxy system minus reducing the modulus, strength and thermal constancy. [33] Moreover, HNT enhance the crystallization temperature, glass transition temperature and crystallinity of polyamide-11 (PA11) nanocomposites.…”

Covalent crosslinks turn natural Eucommia ulmoides gum/polybutene‐1 composites into multiple shape memory materials

“…[17][18][19][20][21][22] However, formation of "sea-island" phase morphology is unfavorable for high shape recovery force as well as excellent mechanical properties of polymer composites due to weakened interfacial adhesion. [19,23,24] Therefore, it is essential to promote interfacial interaction by tailoring the phase morphology for the development of shape memory composites via polymer blending.…”