With the rapid development of industrialization and urbanization, suspended particulate matter pollution has become a major factor that threatens air quality, even the health and life of human[1–3]. For example, particulate matters with a size of less than 2.5 µm (PM2.5) can penetrate the respiratory tract and alveolar tissues and then stay in the body, causing many serious diseases, such as asthma, bronchitis, pneumonia, lung cancer, heart disease and even serious endanger human health[4, 5]. Therefore, some countries have set increasingly strict emission limits for pollutants, from "ultra-low emission" to "near-zero emission"[6]. In this context, fiber filtration materials with a simple structure and excellent filter performance for suspended particulate matter are widely used in various industrial fields[7].
Compared to woven fabrics, nonwoven materials are made directly of fibers, making them form a three-dimensional mesh structure with high porosity, good air permeability and high filtration efficiency[8, 9]. Therefore, nonwoven materials are often used as high-performance fiber filtration materials. For the past few years, fiber filter materials have been commonly processed through needling, meltblowing, Solution Blowing, spunlace and electrospinning[10–14]. Among them, electrospinning is considered as a simple and effective method to prepare nanofibers. The electrospinning nanofibers have the characteristics of a large specific surface area and small pore size[15, 16]. It is well known that the filters with smaller fiber diameter have a more effective interception for suspended particles in the air stream, especially for particles with smaller size[17, 18]. As a result, electrospinning nanofiber membranes can be used as a high efficiency air filter.
According to the operating temperature, fiber filtration materials are commonly divided into normal temperature filtration materials, high temperature filtration materials and ultra-high temperature filtration materials[19]. The main factor that determines the use temperature of fiber filtration materials is the thermal stability of the fiber. In the few last years, the fibers used in high temperature filtration materials mainly include polyphenylene sulfide (PPS), polyimide (PI)[20, 21], polytetrafluoroethylene (PTFE)[22, 23], polyether ether ketone (PEEK)[24], aramid[25, 26], aromatic sulfone (PSA)[27] and other high performance organic fibers[28], and even include inorganic fibers such as glass fiber[29], ceramic fiber[30, 31] and carbon fiber[32]. High performance organic fibers and inorganic fibers respectively have high price or poor textile machinability (rigidity, easy to brittleness) shortcomings, which restrict their application in fiber filters. As a result, the development of new fiber filter material has become an urgent need.
OPAN fiber is a kind of fiber obtained from PAN fiber through thermal stabilization, accomplished in an air atmosphere at 200–300℃[33, 34]. In addition, the OPAN fiber is an intermediate product in the process of the preparation of high performance carbon fiber[35]. The OPAN fiber has some excellent performances, such as high temperature resistance, excellent chemical resistance, low price and good textile machinability characteristics, which make it to be a potential thermal stable fiber used for filters