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. 2022 May 9;15(9):3396.
doi: 10.3390/ma15093396.

Study on Nitrile Oxide for Low-Temperature Curing of Liquid Polybutadiene

Ping Li  1 , Xiaochuan Wang  2   3   4   5
Affiliations

Study on Nitrile Oxide for Low-Temperature Curing of Liquid Polybutadiene

Ping Li et al. Materials (Basel). .

Abstract

As a significant component of composite solid propellants, the cross-link alkenyl polymers need to cure at high temperatures and the current isocyanate curing systems are highly humidity sensitive. This paper presented a low-temperature curing method for a cross-linked polymer (polybutadiene) with stable wettability by using cycloaddition of the nitrile oxide of tetramethyl-terephthalobisnitrile oxide (TTNO) and the C=C group of liquid polybutadiene (PB). The TTNO was synthesized in four steps from 1,2,4,5-tetramethylbenzene and evaluated as a low-temperature hardener for curing liquid PB. To characterize the reaction ability of TTNO at 25 °C, the cross-linked rubber materials of various contents (8%, 10%, 12%, 14%, 16%) of curing agent TTNO were prepared. The feasibility of the curing method can be proved by the disappearance of the absorption peak of the nitrile oxide group (2300 cm-1) by FT-IR analysis. Contact angle, TG-DTA and tensile-test experiments were conducted to characterize the wettability, thermo-stability and mechanical properties of the obtained cross-linked rubber materials, respectively. The results showed that the curing agent TTNO could cure PB at room temperature. With the growing content of the curing agent TTNO, the tensile strength of the obtained cross-linked rubber material increased by 260% and the contact angle increased from 75.29° to 89.44°. Moreover, the thermo-stability performances of the cross-linked rubber materials have proved to be very stable, even at a temperature of 300 °C, by TGA analysis.

Keywords: cross-linked rubber material; low-temperature curing; tetramethyl-terephthalobisnitrile oxide.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Synthesis of rubber material: (a) synthesis of TTNO and (b) formation of the cross-linked rubber material.
Figure 2
Figure 2
FT-IR spectra of (a) cross-linked polymer and the blend of PB and TTNO, (b) cross-linked polymers of different TTNO contents.
Figure 3
Figure 3
Brittle fracture surface of (a) 8% curing agent, (b) 10% curing agent, (c) 12% curing agent, (d) 14% curing agent, (e) 16% curing agent.
Figure 4
Figure 4
Contact angle of (a) curing agent 8%, (b) curing agent 10%, (c) curing agent 12%, (d) curing agent 14%, (e) curing agent 16%.
Figure 5
Figure 5
Properties of the rubber material of various TTNO content: (a) tensile strength and (b) TG curves.
See this image and copyright information in PMC

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