Investigation of Hydroxyl‐Terminated Polyether Cured with Different Isocyanates: Curing Process and Mechanical Property

Abstract

In order to study the curing process of hydroxylterminated polyether (HTPE) with different curing agents, aliphatic triisocyanate (N100) and toluene diisocyanate (TDI), the crosslink density (XLD) and chemical processes of the curing reactions have been investigated by low-field NMR spectroscopy and FTIR spectroscopy, respectively, while the mechanical properties of those two cure systems were studied as well. The results show that, for either HTPE/ N100 or HTPE/TDI, the higher curing temperature leads to the shorter curing time to reach stability of XLD, while the final XLD decreases by increasing the temperature. The XLD and tensile strength of HTPE/TDI are both lower than those of HTPE/N100, although curing reaction of the HTPE/TDI system is faster and more complete, as seen from FTIR spectra. Besides, the tensile strength of HTPE/N100 based propellant attains the maximum value of 0.64 MPa at NCO/ OH ratio of 1.4, while the maximum XLD value of 6.5 �10 À 5 mol•cm À 3 was obtained at the same time. The XLD is well correlated in tensile strength with the variation of NCO/OH, that suggests regulation of XLD value may be an effective way to optimize the curing conditions for improving mechanical properties of HTPE/isocyanate-based propellants.

Overlooked Impact of Interchain H-Bonding between Cross-Links on the Mechanical Properties of Thermoset Polyurethane Elastomers

“…However, the systematic analysis of the mechanical properties of polyurethane thermosets is not as rich as that of TPE. The majority of the strategies on tuning their mechanical properties have been focused on adjusting the cross-linking density, SS prepolymer modification and blending, mixing of cross-linkers and curing agents, and so on. − The cross-linking density was usually reported to be varied by changing the molar ratios of the isocyanate group to the hydroxyl group (NCO/OH). , The chain length, composition, and structure of the soft segment also played important roles in modulating the properties of polyurethane thermosets. ,− In terms of HS structure, many other works have been focusing on constructing elastomer networks based on various types of polyol cross-linkers or isocyanate cross-linkers, including employing a mixture of aliphatic and aromatic isocyanates instead of only one type. ,− …”

“…20−23 The cross-linking density was usually reported to be varied by changing the molar ratios of the isocyanate group to the hydroxyl group (NCO/ OH). 24,25 The chain length, composition, and structure of the soft segment also played important roles in modulating the properties of polyurethane thermosets. 24,26−30 In terms of HS structure, many other works have been focusing on constructing elastomer networks based on various types of polyol cross-linkers or isocyanate cross-linkers, including employing a mixture of aliphatic and aromatic isocyanates instead of only one type.…”

Effect of Fluoroalcohol Chain Extension Modified HTPB Binder on the Combustion Performance of Aluminized Propellants

“…When used as propellant matrixes, especially for propellants that need to be loaded under extreme conditions, HTPB binders are expected to possess excellent mechanical properties. The tailoring of mechanical properties can be accomplished by employing bonding agents to modulate the interfacial bonding between fillers and binders [6] and by adjusting the binder's network structure via the use of curing agents, crosslinking agents, and chain extenders [7,8]; of these, chain extension stands out as a straightforward and efficient method. Commonly used chain extenders include small-molecule diol or diamine chain extenders [9] such as 1,4-butanediol, ethylene glycol, and 2,4-diamino-3,5-dimethylthiotoluene.…”

Role of the Soft and Hard Segments Structure in Modifying the Performance of Acrylic Adhesives Modified by Polyurethane Macromonomers

“…The contact area between the adhesive film and the substrate decreases, resulting in a decrease in peel strength. 35 Figure 9b shows that modified acrylic adhesives with symmetric structures have higher peel strength than those with asymmetric structures; adhesives containing benzene rings have lower peel strength than those without benzene rings, 36 while P HDI has the best peel strength and P TDI has the worst. In addition, the peel strength of PU macromonomermodified acrylic adhesives prepared by PPG is lower than the that of those modified by PEG.…”