Silica (silicon dioxide) is a key component of silicone rubber products, and its recycling and reuse technology is of great significance for resource conservation and environmental protection. At present, the recycling technology of silicone rubber mainly includes physical separation, chemical treatment and heat recovery. Combining the surface characteristics of silica and the structure of silica matrix, a variety of efficient recycling processes have been formed.

1. Recycling technology of silicone rubber

Physical separation technology

Crushing and screening: The silicone rubber products are crushed into micron-sized particles by mechanical crushing, and the silica and other components are separated by screening equipment. This method is suitable for the pretreatment of large-sized waste, but it needs to be combined with subsequent purification processes.

Airflow sorting: The density difference between silica and silica matrix is used to achieve separation through airflow classification. This method has a high recovery efficiency for ultrafine particles, but the energy consumption is large.

Chemical treatment technology

Solvent extraction method: Use organic solvents (such as toluene and ethanol) to dissolve the silica matrix, and separate silica by filtration or centrifugation. The recovered silica needs to be washed and dried before reuse, but the cost of solvent recovery is high.

Acid-base treatment method: dissolve inorganic impurities in silicone rubber by acid washing (such as hydrochloric acid), or destroy silicone rubber network structure by alkali washing (such as sodium hydroxide) to release white carbon black. This method can obtain high-purity white carbon black, but the reaction conditions must be strictly controlled to avoid pollution.

Heat recovery technology

High-temperature cracking: Under the protection of inert gas, heat the silicone rubber to 500-800℃ to decompose the organic silicon matrix into gas (such as methane, hydrogen), and the residual Silicais collected after cooling. This method can achieve complete separation of silicone rubber matrix and white carbon black, but it requires supporting tail gas treatment equipment.

Combustion pyrolysis: Mix silicone rubber with fuel and burn it. While recovering heat energy, Silicaremains in the form of ash. This method is suitable for large-scale processing, but the purity of Silicais low and needs further purification.

2. Silicarecycling technology

Surface modification and recycling

Recycled Silicaoften has residual organic matter or impurities on its surface, and needs to be surface modified by silane coupling agent, alcohol or chlorosilane reagent to improve its compatibility with the new silica matrix. The modified Silicacan be reused in the production of silicone rubber, sealant and other products.

Preparation of nanocomposite materials

Recycled Silicais compounded with nanomaterials (such as carbon nanotubes and graphene) to prepare high-performance composite materials by sol-gel method or in-situ polymerization technology. Such materials have wide application potential in electronic packaging, sensors and other fields.

Resource utilization

Construction field: Recycled Silica used as an additive in cement and coatings to improve the wear resistance and weather resistance of the material.

Agriculture field: Modified Silica be used as a soil conditioner to enhance soil water retention and air permeability.