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The Materials Resin Manhole Cover and Production Processes of the FRP Inspection Manhole Cover?

the materials resin Manhole Cover and production processes of the FRP inspection manhole cover?

Resin generally refers to a softening or melting range after heating, a tendency to flow under external force when softened, and a solid, semi-solid, and sometimes liquid organic polymer at normal temperature. Broadly speaking, any polymer that can be used as a raw material for the processing of plastic products is referred to as a resin. The resin is divided into natural resin and synthetic resin. Natural resin refers to amorphous organic substances obtained from animal and plant secretions in nature, such as rosin, amber, shellac and the like. Synthetic resin refers to a resin product obtained by chemical synthesis of a simple organic substance or chemical reaction of certain natural products. Natural resins can be classified according to the history of resin components and resin formation.

Resin manhole cover
According to the basic components of the resin can be divided into three parts:
1 pure resin, that is, a resinous substance composed of an anthraquinone substance and a crude essential oil. Generally insoluble in water, but soluble in organic solvents such as rosin.
2 Containing gum or gum resin, it is composed of polysaccharides, soluble in water or swollen with water, insoluble in alcohol and organic solvents, such as frankincense.
3 oleoresin or scented gum refers to a resin containing more essential oils and soluble in oil. According to the formation history of the resin, it can be classified into a fossil resin, a semi-fossil resin, and a fresh resin. The latter is the most important source of natural resins. Some natural resins are named after the port name of the earliest container export, such as gamma resin and coba resin.
Synthetic resins are viscous liquids or heat-softenable solids. They usually have a melting or softening temperature range when heated, and can be plastically flowed under external force. Some properties are similar to those of natural resins. The most important application of synthetic resins is in the manufacture of plastics. In order to facilitate processing and improve performance, additives are often added, and sometimes used directly for forming, so it is often synonymous with plastic.
Synthetic resins are also the basic raw materials for the manufacture of synthetic fibers, coatings, adhesives, and insulating materials. There are many types of synthetic resins. According to the main chain structure, there are carbon chain, hetero chain and non-carbon chain synthetic resins; according to the synthetic reaction characteristics, there are polyaddition type and polycondensation type synthetic resin. In practical applications, thermoplastic resins and thermosetting resins are often classified according to their thermal behavior. The raw materials for the production of synthetic resins are abundant. In the early days, coal tar products and calcium carbide acetylene were the main products. Currently, oil and natural gas products are mainly used, such as ethylene, propylene, benzene, formaldehyde and urea. The production method of the synthetic resin employs bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization, melt polymerization, and interfacial polycondensation.
Plastics: A material that has a plastic behavior. The term "plasticity" refers to a state in which deformation occurs when an external force is applied, and the force is maintained after the external force is removed. The elastic modulus of the plastic is between the rubber and the fiber, and the force can be deformed. Soft plastic is close to rubber and hard plastic is close to fiber.
Plastic refers to a material that can be flow-formed during processing by using a resin (or a monomer directly polymerized during processing) as a main component and additives such as plasticizers, fillers, lubricants, and colorants as auxiliary components. Plastic is a synthetic polymer compound that can be freely changed in shape. Plastic is a material obtained by polymerizing a monomer raw material by synthesis or condensation reaction, and is composed of a synthetic resin and a filler, a plasticizer, a stabilizer, a lubricant, a colorant and the like, and its main component is a synthetic resin.
Recycled resin composite inspection manhole cover is a synthetic resin-based composite material which is made by using fly ash and waste plastic as raw materials and is mixed and melted in a molten state. This composite inspection cover is made of waste materials without any steel or Other recyclable materials have an anti-theft feature. At the same time, it can digest a large amount of fly ash and waste plastics in manufacturing, in line with national energy conservation and environmental protection policy requirements. It is therefore called the “green manhole cover”. At the same time, its anti-pressure, anti-bending, impact strength and other properties are better, and it has the advantages of no corrosion, no rust, etc. Its quality has reached the level of similar cast iron products, and its cost is about 30% lower than that of cast iron products. The economic benefits are significant, so it has strong market competitiveness. However, the quality of the recycled resin composite inspection manhole cover is unstable during use, especially in the case of high temperature. The manhole cover will undergo a qualitative change, which will cause the middle part of the inspection manhole cover to sink continuously and cause it to fall off. This will create a great safety hazard.

FRP Inspection Manhole Cover
 FRP inspection manhole cover, which is made of unsaturated polyester resin as raw material, glass fiber as reinforcing material, and added with a certain filler to make the inspection manhole cover. Due to different processes, different structural materials, and different materials. The performance of the manufactured inspection covers is also very different. The domestic production process of FRP inspection manhole covers generally includes:
(1) Resin transfer molding process. Due to the high resin content, the inspection manhole cover produced is not suitable for use on the roadway due to insufficient carrying capacity;
(2) Hand lay-up process. The production efficiency is slow, it is not suitable for large-scale production, and there is no competitive advantage;
(3) Molding process. The molding process is layered composite press molding under a certain temperature and pressure. This product is relatively compact in structure and uses different materials in different parts of the inspection manhole cover. Continuous fiber reinforcement is used in the lower part of the inspection manhole cover. To ensure its carrying capacity: use filler in the middle. In order to improve the product's resistance to deformation and reduce production costs: use high hardness, wear-resistant materials in the upper part to improve the pressure resistance and wear resistance of the upper part of the product. The FRP inspection manhole cover has been gradually promoted due to its advantages of light weight, high strength, fatigue resistance, corrosion resistance, brittleness, and easy processing.

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