Advanced fabrication and properties of hybrid polyethylene tetraphalate fiber-silica aerogels from plastic bottle waste

Recycled polyethylene tetraphalate (rPET) fiber-silica aerogels are successfully developed from rPET fibers obtained from PET plastic bottle waste and tetraethoxysilane (TEOS). The rPET - silica aerogels are prepared through a direct gelation of silica on PET. rPET fibers are treated with dichloromethane to partially dissolve the fibers. The fibers are then dipped and allow to swell in TEOS/ethanol mixture, with the pH controlled to 2.5 using HCl to promote hydrolysis. After the acid hydrolysis, the pH was controlled to 7 with an ammonium hydroxide solution (NH4OH) to promote condensation. The surface modification is carried out in a trimethylchlorosilane (TMCS)/n-hexane solution and washed with n-hexane to dry at room temperature to prevent shrinkage. The developed rPET - silica aerogels exhibit super-hydrophobicity with an average water contact angle of 149.9 degrees. Their thermal conductivity is approximately 0.037 W/m K. They have a very low compressive Young's Modulus (0.95-4.19 kPa) and hence very soft. By utilizing rPET fibers, this work provides an alternative method of recycling PET plastic wastes which ultimately helps in reducing its detrimental impact to the environment. The developed aerogels can be used in several industrial applications such as heat insulation, filtering, sound insulation and absorption.