US Patent 9725645 Proppant with composite coating

Proppants for hydraulic fracturing of oil and gas wells have a polymeric coating that is strengthened with reinforcing particulates that are reactive with, or chemically bonded to, the polymeric proppant coating. Preferably, these particulates are added into the coating during the coating process. In one embodiment, functionalized particulates are used that become grafted into the polymer of the proppant coating through the chemical functionality imparted to the particulates. If non-functionalized particulates are used, a coupling agent is preferably added to enhance the bond strength between the added particulates and the polymeric matrix of the proppant coating.