The Thermogravimetric,Microscopic and Mechanical Analyses of PBT and PET yarns(1)

In this study, thermogravimetric, microscopic and mechanical properties of different types of polyester yarns were investigated and compared. To this goal, PET based regular polyester yarn and polyester yarns modified for various specialities (flame-retardant, UV protective and antibacterial) and PBT yarn were selected. According to the results, it was determined that PBT had a lower Tdi value, higher char residue, lower tensile strength compared to regular PET and similar surface characteristics to regular PET. Among the modification processes, only the flame retardancy process was found to affect the thermal property.

Introduction
Polyester is a well known synthetic fibre that has been around for more than half a century. It is used in all types of apparel, home furnishings, geotextiles, industrial applications, tire reinforcement, and so on. Like other fibers, it is routinely sold in many variants of diameter, cross-section, and luster. It is generally produced by the polycondensation of terephthalic acid and ethylene glycol and this polyester fibre is known as polyethylene terephtalate (PET) fibre (1). Polyethylene terephthalate (PET) fibers have an excellent capacity for physical modification (2). Besides PET fibre, there are also other commercialized polyester fibres synthesized from various monomers such as poly 1,4-cyclohexylenedimethylene terephtalate, poly buthylene terephtalate and poly trimethylene terephtalate

Poly 1,4-cyclohexylenedimethylene terephtalate was originally developed for fibre applications but has found wider utility as a reinforced polymer for injection molding and as a material for crystallized food packaging trays nowadays (4). Polytrimethylene terephthalate (PTT) is a new type of polymer material produced by the polycondensation reaction of purified terephthalic acid (PTA) and 1,3-propanediol (PDO). As a member of the polyester family, PTT has very similar chemical properties with polyethylene terephthalate (PET)

Poly butylene terephthalate (PBT) is a linear polyester of aromatic nature and has excellent mechanical properties (7). PBT is made by reacting 1, 4- butanediol (BDO) with terephthalic acid (TPA) or dimethyl terepthalate (DMT) in the presence of a transesterification catalyst. PBT is easily made into fibre and monofilament and has been used in some fibre applications. Compared to PET, PBT fibre is more resistant to permanent deformation (4). Polyester fibers are produced in avariety of forms, broadly classified as staple fibres, textile filament and industrial filament. End-uses for these variants have different requirements in terms of fibre properties and physical geometry, and so different fibre manufacturing processes have evolved according to the special needs of each market segment (4). Although polyester fibre has good properties like high tensile strength, luster etc., it has inherent characteristics that limit its use in some applications too. For example, low water-absorbing capacity, high pilling tendency, tendency to accumulate static charge, difficulty of dyeing and low abrasion resistance are undesirable properties of the polyester fibres (8).

Writen by Buket ARIK1, Ebru BOZACI1, Asli DEMIR2, Esen ÖZDOGAN1