Production of long glass fibre reinforced PP by direct mixing The plastics processing industry has been using long glass fibre reinforced PP (PP-LGF) granules for many years. This can be used as a substitute for fibreglass (thermoplastic compression moulding), glass fibre PA, PBT or even metal in certain applications embedded in PP binders. While so far mainly types containing 40% or more glass fibres have been sought, there is now also demand for PP-LGF with a lower glass fibre content.