Having recently researched about the pillow industry in order to set up our new E-Commerce website Purley Pillows, I came across some information on conjugated fibres in pillows.
Conjugated fibres are a twisted polyester fibre used to increase the fill in the pillow and increase longevity. On top of that, these fibres increase the bounce of the pillow and have extra resiliency hence the time span of pillows being a lot longer than regular fibres.
Added to this was another term that was associated with conjugated and this was called "hollow". Hollow means that the pillow traps air in-between the fibres. This then allows the pillow to create greater loft and thus increases the shape of the pillow.