Search

Polyurethane (PU) plays a critical role in elastomers, adhesives, and self-healing materials. We selected the most commonly used aromatic isocyanates, 4,4′-methylene diphenyl diisocyanate (MDI) and tolylene-2,4-diisocyanate (TDI), and the most commonly used aliphatic isocyanates, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and dicyclohexylmethane-4,4′-diisocyanate (HMDI), as raw materials, combined with polytetramethylene ether glycol (PTMG) and 1,4-butanediol (BDO) to successfully synthesize five PU materials. The effects of isocyanate structure on polymerization rate, hydrogen bonding, thermal properties, phase separation, wettability, self-healing performance, adhesion, and mechanical properties were systematically investigated. The results show that isocyanates with higher symmetry facilitate hydrogen bonding, but excessive flexibility and crystallinity may inhibit its formation. MDI-based PU exhibits the highest hydrogen bonding index (HBI) of 4.10, along with the most distinct phase separation and the highest tensile strength of 23.4 MPa. HMDI-based PU demonstrates the best adhesion properties, with the highest lap shear strength of 7.9 MPa, and also exhibits excellent scratch healing ability. IPDI-based PU shows good self-healing performance, recovering 88.7% of its original tensile strength and 90.6% of its original lap shear strength after heating at 80 °C for 24 h. Furthermore, all the samples can be reprocessed by melt or solution methods, showing excellent recyclability. [ABSTRACT FROM AUTHOR]

The development of new polymer electrolytes is greatly significant due to the improvement of the energy density and safety of lithium batteries. Comparing with a single polymer electrolyte, the composite polymer electrolyte has better performance, especially some based on the concept of rigid–flexible coupling polymer electrolytes. In this study, a series of polyurethane with various proportion of soft and rigid segments are synthesized and used as a composite polymer electrolyte (C‐PU) together with cellulose membrane. The optimized polymer electrolyte C‐PU20 (with 20 wt% of the hard segment) exhibits high ionic conductivity of 2.4 mS/cm at 25°C and wide electrochemical stability window up to 4.8 V. Moreover, the C‐PU20 electrolyte for LiFePO4/Li cell shows more fantastic cycling performance with capacity retention of 96% after 300 cycles at 0.5 C and better C‐rate capability compared with the pristine cellulose membrane. All the findings indicate that the C‐PU20 electrolyte is a very prospective polymer electrolyte for high‐performance lithium batteries. [ABSTRACT FROM AUTHOR]

In order to obtain higher thermoelectric and mechanical properties in nonpolar thermoplastic vulcanizates (TPVs), the butyl rubber/polypropylene (TPVs)/hydroxylated graphene (HGE) composites with nanosheet network were prepared through masterbatch technique and based on thermodynamic calculations, using polypropylene-graft-maleic anhydride (PP-MA) as a compatibilizer. The Fourier transform infrared (FTIR) and Raman spectra revealed the introduced maleic anhydride group on PP-MA can form strong interfacial interaction with hydroxyl-containing functional groups on HGE. Morphology study indicated the rubber particles in the composites occupied the most volume of the PP phase, as expected to hinder the aggregation of HGE and form the effective nanosheet network. The nanosheet network can be combined with the butyl rubber (IIR) cross-linked particles during the dynamic vulcanization process to improve the interface bonding between PP and IIR, thus increasing the tensile strength of TPVs. The prepared TPVs/HGE composites have significantly improved in mechanical properties, thermal properties and dielectric properties, which provides a guarantee for their potential application as multifunctional TPVs polymers. [ABSTRACT FROM AUTHOR]