The Thermogravimetric,Microscopic and Mechanical Analyses of PBT and PET yarns(2)

In many applications, modification of polyester fibre properties is desirable in order to enhance certain features of the product or to enhance the process of converting fibres into finished goods. Polyester can be modified to obtain new or enhanced properties,such as an affinity for cationic dyes,non-flammability, resistance to ultraviolet radiation, increased strength, etc; or to suppress some negative properties, such as reducing the pilling tendency, increasing the absorbing capacity, etc Polyester melts at around ~265-285°C.The glass transition temperature of amorphous polyester is in the range of 65-75°C, and this can increase to ~125°C after being drawn and partially crystallized, reflecting the reduced

Rotational mobility of the chain segments. But sometimes, problems can occur with garments made from thermoplastic polymer fibres when exposed to flames; the molten polymer can stick to skin and cause burns.Thermal decomposition of polyester also generates acetaldehyde, which is a flammable gas that feeds combustion. Additives can be used to break the combustion cycle, e.g. endothermic substances that absorb heat; char formers that insulate the flame from the substrate, additives that react with and remove oxygen (e.g. phosphorous), or additives that promote melting and dripping to separate the molten material from the combustion area.

UV radiation is also one of the major causes of degradation of textile materials, which is due to excitations in some parts of the polymer molecule and a gradual loss of integrity, and depends on the nature of the fibres.UV absorbers incorporated into the fibres convert electronic excitation energy into thermal energy, function as radical scavengers and singlet oxygen quenchers. The high-energy, shortwave UVR excites the UV absorber to a higher energy state; the energy absorbed may then be dissipated as longer-wave radiation. Alternately, isomerisation can occur and the UV absorber may then fragment into nonabsorbing isomers

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