Preparation And Properties Of Dyeable Modified Polypropylene Composite Fiber

Polypropylene(PP)fiber is a chemical fiber spun with isotactic polypropylene.Since incepted,polypropylene fiber has been used in the field of civilian fibers due to its excellent hydrophobicity and moisture conductivity,light specific gravity,and low thermal conductivity.However,the dyeing properties of polypropylene fiber is poor due to its regular structure and lack of polar groups in the molecular chains which could bind to dyes.Thus,dyeing modification for polypropylene fiber is of great significance.Among all dyeing modification methods,blending modification is considered as one of the most effective methods to improve the dyeing properties of polypropylene due to the high efficiency and low cost.A large amount of modifier is necessary in order to increase the dye uptake of polypropylene,which would greatly affect spinning processability of PP and mechanical properties of PP fiber.Therefore,preparation of dyeable PP fiber with good spinning processability and mechanical properties will be important and difficult by choosing superior modifier and spinning technology.In this paper,dyeing modified PP was prepared through melt blending,using thermoplastic polyester elastomer(TPEE)as a dyeing modifier and polypropylene grafted glycidyl methacrylate(PP-g-GMA)as a compatibilizer,with various of proportion.The sheath-core composite spinning technology was employed to prepare dyeable PP composite fiber using the obtained modified PP as the sheath component and fibergrade PP as the core component.Chemical structure and properties of PP,TPEE and PP-g-GMA were investigated on nuclear magnetic resonance spectrometer,melt index meter,differential scanning calorimeter and rotational rheometer.The hard segments and soft segments of TPEE are respectively composed of polybutylene terephthalate(PBT)and polytetramethylene ether glycol(PTMG).The melting points of PP,TPEE and PP-g-GMA are 162.0 °C,193.3 °C and 165.7 °C respectively,and the initial thermal decomposition temperatures are 419 °C,374 °C and 427 °C respectively,showing a good thermal stability and a wide processing temperature range.The melt index of three raw materials is following the order of PP>TPEE>PP-g-GMA,in which the melt index of PP and TPEE increases obviously with increasing temperature,while the melt index of PP-g-GMA has little change with increasing temperature.According to the results of the rotational rheological test,the complex viscosity of PP and TPEE decreases as the temperature increases,and the complex viscosity of PP is lower than that of TPEE.The melt index test results are consistent with the rotational rheological test resultsModified PP with various compatibilizer contents was prepared via melt blending in a twinscrew extruder under different blending temperature using PP-g-GMA as a compatibilizer and TPEE as a dyeing modifier.Scanning electron microscope,differential scanning calorimeter,polarizing microscope,rotational rheometer,etc.were used to study the cross-sectional morphology,crystalline properties,and rheological properties of the modified PP.Average size of dispersed TPEE phase in modified PP reaches 1.03 ?m with a good dispersion with 1 %compatibilizer,which is smaller than that of other compatibilized samples.In addition,the average size of dispersed TPEE phase in modified PP prepared at 220 °C reaches 0.81 ?m,which is smaller than that of samples prepared at other temperatures.Melt crystallization temperature and crystallinity of modified PP decrease with increasing compatibilizer content,and the isothermal crystallization rate increases at lower temperature.The spherulite size of PP decreases with less crystal nuclei and weak black cross extinction after the addition of TPEE.Loss modulus,storage modulus and complex viscosity of modified PP all increase with the addition of TPEE or increasing compatibilizer content.The complex viscosity of modified PP has little change with longer testing time at 230 °C,showing a good thermal stability.Dyeable sheath-core composite PP fiber was prepared via composite spinning using modified PP as the sheath component and PP as the core component.The effect of spinning speed,sheathcore component ratio and compatibilizer content on the properties of composite fiber was then investigated.As the spinning speed increases,Orientation,crystallinity,dynamic thermal stress and tensile strength of the composite fiber increase with a poorer spinning processibility.The dyeing properties of composite fiber has been significantly improved with sheath component content increasing from 40 % to 60 % with decreased orientation degree,crystallinity,dynamic thermal stress and tensile strength.K/S value increases from 4 to 5.11 at the dyeing temperature of 100 °C,and dye uptake ratio increases from 18.2 % to 36.7 % The tensile strength of compatibilized composite fiber increases,and the dying ability of composite fiber with compatibilizer is superior to the original composite fiber and PP fiber.K/S value of composite fiber with 1% compatibilizer reaches 4.73 and dye uptake ratio increases to 35.4 % at the dyeing temperature of 100 °C,which are higher than 0.26 and 11.1 % of PP fiber,respectively.In this paper,melt blending and sheath-core composite spinning technology are used to prepare dyeable sheath-core PP composite fiber.This PP composite fiber has good processibility,good mechanical properties and improved dyeing properties for disperse dyes.This work will contribute to the industrialization of dyeable PP fiber.