Polypropylene(PP) and Polyester(PES) are the two major fibres mainly used in apparals, Nonwovens, Industrial yarns and fabrics. It is therefore useful to have an understanding of their relative merits and limitations. It is therfore useful to have an understanding of their relative merits and limitations.Polyester is made from Dimethyl terepthalate(DMT) and Mono Ethylene Glycol. Modern processes use pure Terepthalic acid(PIA) in place of DMT. Polypropylene is a polyolefin made from a polypropylene monomer obtained from naptha. Both fibres are available as virgin and bottle grade( from regenerated material). Virgin fibre is used for apparal purposes and regenerated fibre is used in nonwovens for making carpets, floor coverings, blankets and filters.
PES is available in 1 - 15 denier range though micro denier fibres are also made by some manufacturers. PP is usually available in the denier range 2.5 to 20.
The two fibres are nearly comparable in tenacity though PES is avaiable in higher tenacity grades.Polyester is available in 3 tenacity grades vizMediumgrade -4.8 -5 g/den, Hightenacity - 6 - 6.7 g/den, Super tenacity 7 g/den.Polypropylene has a tenacity between 3.5 -6 g/den. For industrial fabrics with higher stipulated strength and sewing threads, PES will be able to meet the requirements of strength more easily.
Elongation is higher in PP. This gives better elasticity for material and improved moulding in moulded carpets.
Density of polypropylene (0.91g/cc) is much lower than that of polyester(1.38 g/cc). As a result thicker, bulkier yarns and loftier fabrics and more comfortable carpets are made with the former for a given count of yarn and area density of fabric.
Polypropylene is dope dyed and is available in an extensive range of colours and shades. It is therefore much easier to achieve colour and shade matching by mixing a minimum number of shades of fibres. Dope dyed polyester, on the other hand, is available only in a limited number of colours and shades. The required shade has often to be developed through R&D work or fibre has to be dyed.
Melting point of polypropylene (165oC) is much lower than that of polyester (260oC - 270oC). Material made from this fibre are therefore not suitable in fire fighting and similar clothings where temperatures are high. Heating time, temperature and pressing time are therefore more critical in moulding with polypropylene.
Flame retardancy by burning rate is inferior with polypropylene than with polyester. A flame retardant compound has to be added to the dope to meet the flammability requirements in Exports with polypropylene. This adds to the costs.
Resistance to UV light is inferior with PP compared to PES. UV stabiliser has to be added during manufacture of polypropylene to improve its resistance to UV light. Carbon black is usually added as UV stabiliser to PP. With geotextiles and upholstry material continuously exposed to sunlight, PES is more suitable than PP.
Polypropylene tends to form beads during carding. The beads get deeply loaded on the cylinder wire and also on the needles. There has to be a regular programme for removing the beads from the wire and needle. Achievable production rates are therefore lower with polypropylene than polyester because of card loading. Card processing problems are more acute with lower deniers and recycled fibres with polypropylene.Polypropylene tends to melt forming beads in OE spinning at high rotor speeds leading to nep like defects in yarn. Even in ring spinning nep like defects due to bead formation is encountered with polypropylene at high spindle speeds. Achievable speeds are therefore lower with PP than PES.
PP is highly inert to chemicals and is suitable as fishing nets and geotextiles in alkaline and acidic soils. PES on the other hand loses its strength in alkaline soils and should not be used. Strength retention of PES after immersion in aqueous solution at 95oC is given below.
Strength retention of PES straps after immersion in aqueous solution at 95oC
Number of days
Alkaline solution
Neutral solution
30
76%
90%
300
38%
45%
PES has higher creep resistance (Retention of tensile properties over a long period of time) than PP and this is a distinct advantage in geotextiles used for anchoring of soils and similar applications. Because of its low glass trangition value(T<sub></sub>g) PP has less creep resistance.
Static generation is more with PP than PES because of lower moisture regain. Danger of sparks is therefore more.
» left by jatin makwana j. from vadodar (Gujarat) (India) (1 year 187 days ago.)
i want to do plsama treatment in polypropylene fibre. can u guide me? how do this process, which material used, etc....
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