Copolymerization of phthalonitrile-based resin containing benzoxazine and cyanate ester: Curing behaviors, fiber-reinforced composite laminates and improved properties

Abstract

Curing behaviors and copolymerization mechanisms between phthalonitrile-based resin containing benzoxazine (A-ph) and cyanate ester (CE) were characterized and discussed. Results indicated that copolymerization between A-ph and CE were comprised of ring-opening polymerization of oxazine rings and ring-forming polymerization of cyanate and nitrile groups. From them, ring-opening of oxazine occurred preferentially, followed by ring-forming of cyanate and nitrile groups, which were promoted by active hydrogen and amine structures generated from ring-opening of oxazine. Moreover, with increasing the content of CE (≥40 wt%), self-polymerization of cyanate would dominate the components of the resulting composites and reduces the thermal stability of fiber-reinforced composite laminates. Additionally, mechanical properties of composite laminates were also affected by the content of CE. Composite laminates with 10 wt% CE showed the highest flexural strength (622 MPa). The improved mechanical properties were also verified with investigation of dynamic thermomechanical analysis and morphology of fracture surfaces. These findings are helpful to improve the thermosetting resins in terms of their chemical structure, material properties, and processability.

The water uptake, thermal and mechanical properties, and aging resistance to thermo‐oxidation of phenylboronic acid‐modified benzoxazine‐glass fiber composites

“…On the other hand, prior works have reported that the Bz‐based polymeric blends do not always promote the flexural strength of their composites. For example, the flexural strength increases as an increased amount of incorporated poly(resorcinol borate), 21 while the amount of incorporated phthalonitrile has minimal influence to its flexural strength 9 . In comparison, an increased amount of incorporated poly (ether‐thioureas) deteriorates the Bz/GF composite's flexural strength 42 .…”

“…For example, the flexural strength increases as an increased amount of incorporated poly(resorcinol borate), 21 while the amount of incorporated phthalonitrile has minimal influence to its flexural strength. 9 In comparison, an increased amount of incorporated poly (ether-thioureas) deteriorates the Bz/GF composite's flexural strength. 42 In Figures 9 and 10, Bz-a shows increased flexural strength and modulus by 27.1% and 13.7%, respectively, for its enhanced interfacial adhesion due to higher cross-linked density of Bz.…”

“…3 However, Bz has the disadvantages of high curing temperature, while with lower char yield at elevated temperature and resin toughness. 4,5 Therefore, other high-performance thermoset resins, such as polyimide, 5 epoxy, 6 phenolic, 7 bismaleimide 8 or cyanate ester, 9 have been modified by blending with Bz to obtain lower curing temperature and/or greater toughness. In addition, Bz has been further improved by modifying its molecular structure via grafting with alkynyl groups, such as ethynyl, 10 nitrile 11 and propargyl 12 groups, in order to boost its thermal stability.…”

Preparation of hybrid cyanate ester resin in the presence of polysilazane and its properties

“…Bisphenol-A dicyanate ester is an important high-performance thermosetting polymer with excellent dimensional stability, high heat resistance, low dielectric constant, strong adhesion and good mechanical properties. 1 –7 It is usually used as a resin matrix for advanced composites, adhesives and coatings used in the electronics, aerospace and military industries. 8 –10 To meet the process requirements of these practical applications, it is necessary for bisphenol-A dicyanate ester to have good processability, including film-forming properties, melting fluidity and a wide processing window.…”

Ablation Behavior of Silicone Rubber-Benzoxazine-Based Composites for Ultra-High Temperature Applications

“…To deal with the carbon residue problem, it is effective to add a polymer resin which is of high carbon content, into the silicone rubber–inorganic filler composites. Benzoxazine resins (BZs) are a type of highly cross-linked aromatic polymer with outstanding advantages, including excellent thermal resistance, good flame retardancy, and near-zero volumetric shrinkage upon curing and high carbon residue [13,14,15,16]. These extraordinary properties make BZs the ideal resin to be used in SR composites for ultra-high temperature applications.…”