Main materials:

Resin matrix: provides the product with corrosion resistance, certain toughness, and formability. Unsaturated polyester resin is commonly used, but for highly corrosive environments, more expensive vinyl resin is preferred.

Reinforced fiber: usually glass fiber (short cut wire or mesh cloth), equivalent to "steel bars", provides the core strength and impact toughness of manhole covers.

Filler material: such as quartz sand, used to increase the rigidity and wear resistance of the product while reducing costs.

Other additives: such as pigments (coloring), curing agents (promoting resin curing), etc.

Manufacturing process:

Compression molding: the most common method. Place the mixed material into a high-temperature mold and apply high pressure and temperature through a large press to press it into shape in one go. This process produces products with high density and good performance.

Casting molding: Inject the mixed slurry into the mold and solidify it into shape under normal pressure or low pressure.