Resin usually refers to a range of softening or melting after heating. When softened, it has a tendency to flow under the action of external forces. It is a solid, semi-solid, or liquid organic polymer at normal temperature. Broadly speaking, any polymer that can be used as a raw material for processing plastic products is called a resin. Resin is divided into natural resin and synthetic resin. Natural resins refer to amorphous organic substances, such as rosin, amber, shellac, etc., obtained from the secretions of plants and animals in nature. Synthetic resin refers to the resin product obtained by chemical synthesis of simple organic matter or chemical reaction of certain natural products. Natural resins can be classified according to the resin composition and the history of resin formation.
According to the basic components of the resin can be divided into three categories:
①Pure resin, which is a resinous substance composed of terpenoids and crude essential oil. Generally insoluble in water, but soluble in organic solvents such as rosin.
②Gum-containing resin or gum resin is composed of polysaccharides. It is soluble in water or swells with water, but insoluble in alcohol and organic solvents such as frankincense.
③Olein-containing resin, or fragrant gum, refers to a resin that contains more essential oils and is soluble in oil. According to the formation history of the resin, it can be divided into fossil resin, semi-fossil resin and fresh resin. The latter is the most important source of natural resins. Some natural resins are named after the names of the earliest ports for container shipments, such as Mastic resin and Coba resin. Synthetic resin is a viscous liquid or a solid that can be softened by heating. When heated, it usually has a melting or softening temperature range. It can show a plastic flow state under external forces. Some properties are similar to natural resins. The most important application of synthetic resins is the manufacture of plastics. In order to facilitate processing and improve performance, additives are often added and sometimes directly used for processing and forming, so they are often synonymous with plastics.
FRP inspection manhole cover is an inspection manhole cover made of unsaturated polyester resin as the raw material, glass fiber as the reinforcing material, and a certain filler. Due to different processes, different structural materials, and different reinforcing materials. The performance of the manufactured inspection manhole cover products also varies greatly. The domestic technology for producing FRP inspection manhole covers is generally as follows:
(1) Resin transfer molding process. Due to the high resin content, the manhole cover produced is not suitable for use on the roadway due to insufficient bearing capacity;
(2) Hand lay-up process. Slow production efficiency, not suitable for large-scale production, and no competitive advantage;
(3) Molding process. The molding process is a layered composite compression molding under a certain temperature and pressure. This product has a dense structure, and it uses different materials in different parts of the inspection cover. Use continuous fiber reinforcement under the manhole cover. To ensure its carrying capacity: use fillers in the middle. To improve the product's resistance to deformation and reduce production costs:
Use higher hardness and better wear resistance on the upper part to improve the compression resistance and wear resistance of the upper part of the product. FRP inspection resin manhole covers are gradually popularized due to their advantages such as light material, high strength, fatigue resistance, corrosion resistance, non-brittle damage, and easy processing.