Effect of Thermal Treatment on Mechanical Properties of PP BCF Yarns

Carpet is an exactly developed and custom-made floor covering. All the raw materials and fiberswhich are used as pile yarn for carpets originate from the whole fiber range [1,2]. As far assynthetic fibers are concerned three different fibers are currently used more, spun acrylic and BCFpolyamide and polypropylene yarns [3]. Today PP BCF yarn is common material for carpet applications as it’s overall use in carpet industryhas topped a 70% share despite the fact that this polymer was only introduced to floor coveringindustry recently[3,4]. It’s widespread use is due to ease of production, inherent inertness tohumidity and chemicals, stain resistance and light weight [3].Despite this fast penetration into carpet industry, PP has been shown to be deficient in resilienceproperty which refers to recovery power from deformation. In order to improve the resilience of thePP BCF yarns it is a common practice to twist and thermally treat them by steam or hot air incarpet industry. This process implies a thermal treatment of yarn at temperatures significantlyabove the transition temperature and may induce changes in crystallinity and other mechanicalproperties [3].Effect of thermal treatment conditions on various properties of Nylon[5,6] and PET[7] pile yarnswas investigated in some researches. So, thermal treatment effects on some mechanical propertiesof PP BCF yarns were investigated in this work.In this study 17 Polypropylene BCF yarn packages were produced under identical conditions. Then16 of them were twisted and thermally treated in temperatures 120, 130, 140 and 150°C for 45, 60,75 and 90 seconds by Suessen machine which is the common employed heat setting machine. Oneother package was only twisted without any thermal treatment. Tensile properties, bending rigidityand crimp characteristics of these yarns were investigated.It was shown that tensile strength, modulus, crimp contraction and bending rigidity of PP BCFyarns decreased by increasing temperature while residual time had no significant effect on theseproperties except in high temperatures. Figure 1and 2 show effect of temperature on crimpcontraction and bending rigidity of PP BCF yarns.