For up to 400 hours of direct sunlight, untreated polyester will retain greater than 90 % of its strength . In the long term , the ultraviolet degradation of polyester slows down and can level out. Half the strength remains after 4000-5000 hours. (29)
Generally, because of polyester ̉s excellent chemical and physical properties , this material can be used with confidence and is the material of choice for most geotextile applications.
I.3.1.2 Polypropylene fibres
Polypropylene fibres are a manufactured olefin fibre made from polymers or copolymers of propylene, (34)
Polypropylene fibre (PP) continues to be the raw material of choice for the geotextile industry , as polypropylene based geotextiles comprise about 90% of the geotextile market. (39)
Needle punched polypropylene is still one of the largest products for geotextile and related applications in drainage and asphalt resurfacing.(40)
Polypropylene fibres have a very distinguished properties which made it suitable for being used in geotextiles sector :