Type of HC Slick Flame Retardant Polyester Fiber

What is HC slick flame retardant polyester fiber 6d filling sofas?
HC slick flame retardant polyester fiber 6d filling sofas (PSF), which is made directly from PTA and MEG or PET Chips or from PET/ Polyester waste and post consumed PET bottles. It’s used for spinning yarns and making geotextiles, as well as fill pillow, stuff toys, cushions ,etc.