## 1 Introduction  
Cyanate ester (CE) resins are novel high-performance thermosetting resins similar to epoxy (EP) and bimaleimide (BMI) that have been developed in recent decades [1]. CE monomers contain two or more -OCN functional groups which can form a highly symmetrical triazine ring structure after the curing reaction [2]. It is the chemical nature of the CE monomers and the unique structure of the cured resin that give rise to a series of properties, such as excellent mechanical properties, a high glass transition temperature, low contractility rate, low water absorption, and ultralow dielectric constant and dielectric loss values [3; 4; 5; 6]. Compared with other thermosetting resins, CEs have excellent overall performance. Therefore, CEs are a proven replacement for thermosets, such as epoxy or polyimide, in applications in the aerospace, electronics, and communications industries [4; 7; 8; 9; 10; 11]. CE monomers polymerize via a ring-forming reaction under the conditions of heating or catalysts. [PERSON] first proposed the self-polymerization mechanism of CE resins in the absence of a catalyst [12]. The curing reaction of the CE resins was initiated and catalyzed by impurities in the monomer or moisture in the environment. However, this process proceeds with difficulty when the purity of the monomer is high [13]. Active hydrogen containing compounds, such as phenols, amines, and imidazole, in concert with metal ions can catalyze the curing of CE resins [14]. This reaction is depicted in Figure 1. A range of such metal ions has been reported, including chromium [15], manganese [16], iron [17], cobalt [18], tin [19], zinc [20], and copper [21]. However, the metal ion compounds have poor solubility in the CE resins and promote the hydrolysis reaction of the triazine ring as well; as a result, these metal salts are rarely used as a catalyst. Alternative catalytic systems have always been an important direction of research. At present, room temperature ionic liquids (RTILs) and organically modified layered silicate have been proved to accelerate CE resin curing [22; 23; 24]. Physical and structural changes affect the polymerization kinetics and the structure. Therefore, the identification of relevant kinetic models can provide insight into the curing process of thermosetting resin systems. In the curing process, identifying each step of the chemical reaction is very difficult. Especially, in the late curing stage, the diffusion factor plays a controlling role. Thus, the phenomenological model, rather than the mechanism model, is used [25]. The Kamal kinetic model considers both the autocatalytic behavior and the n-stage reaction, and it can be used to describe the curing process of thermosetting resins precisely [26]. However, these models are limited to describing the curing reaction process and do not give specific physical meaning to the parameters. Previous studies demonstrated that the Avrami equation considerably illustrated the isothermal and non-isothermal curing behavior of thermosetting resins [25; 27; 28; 29]. The essence of thermosetting resin curing is the cross-linked chemical reaction of linear polymer chains. Meanwhile, this is accompanied by microphase separation, the shift of the glass transition, and other processes, eventually forming a three-dimensional network structure. It is generally believed that the crystallization process of the polymer includes two processes of nucleation and growth [30]. The first step is the formation of crystal nuclei. Due to local fluctuations in the parent phase, the local free energy increases, resulting in a small range of new phases (clusters). The clusters can continue to grow and become macroscopic crystals, which can also dissolve and disappear. When the cluster reaches a certain size--that is, a critical size--it becomes a crystal nucleus. The second step is the growth of the crystal nucleus, which is characterized by the diffusion and stacking of the polymer segment to the nucleus.