Study On The Spinning And Modification Of Polyphenylene Sulfide (PPS) Fiber

Polyphenylene sulfide (PPS), an advanced thermoplastic material, was first developed by Philip-Chevron Petroleum Co. Ltd. The molecular chain of PPS is constructed with benzene ring and sulfur atom arranged alternately, and consists three types of structure, linear, cross linked as well as hyperbranched molecular configuration. Linear PPS possess good processing ability, and can be fabricated into fibers. PPS polymer has excellent properties such as chemical resistant, thermal stability, fire retard, etc Filtration fell fabricated by PPS fiber is mainly utilized to filtrate fh id of high temperature and corrosive chemical agents in such situation as coal power station and rubbish burning plant. The filtration felts can decrease the release of toxic gas and carry on sustainable environment development.In this study, four aspects were discussed including the synthesis of PPS, the spinning of PPS filament, synthesis of hyperbranched PPS and its use in melt spinning of normal PPS chips as rheological modifier.In this study, the method to svnthesize PPS was by polycondensation of sodium sulfide and p-dichlorobenzene in polarized solvent as NMP that can he industrialized. It has been found that moisture content must be controlled during the process and the polycondensation was carried out in two steps. The appropriate temperature and time for first step was 220℃and 1hr respectively while the second was 260℃and 4-6hr. The mol ratio of p-dichlorobenzene to sodium sulfide should be strictly 1.03: 1. Higher temperature will result in a higher crystallinity and is therefore preferred. 4hr was enough if the temperature reaches: polymerization with too long time was not encouraged.The results showed that optimum conditions for the preparation of PPS fiber were, spinning temperature of 330℃, winding speed of 600m/min, drawing temperature of 150℃and total draw ratio of four. Fiber with higher crystallinity, tensile strength and lower elongation percentage could be obtained by increasing draw temperature and draw ratio. Computer program for profiled fiber cross-section simulation was developed to obtain the optimum shape and dimension of spinneret die. The result showed that Y-shaped PPS fiber possessed lowest bulk density and filtrate efficiency when the cross-section of bottom branch was twice as long as the upper branch. Profiled PPS fiber, compared to regular round one, possessed higher tensile strength and lower elongation at break. Above all, Y-shaped PPS fiber had the largest perimeter and surface area. Different lengths of branch could get rid of the overlap phenomenon of trilobal fiber with branches embedded into each other due to the equal branch length and width.Hyperbranched PPS was synthesized by 3,4-dichlorobenzenethiol with potassium carbonate in polarized solvent NMP at 150℃for 8.5hr. Highly branched structure endows hyperbranched PPS with entirely different properties to linear PPS. For instance, hyperbranched PPS is amorphous while linear PPS is semi-crystal polymer. Linear PPS wiil not dissolve in most solvents at room temperature for while hyperbrancned PPS can easily be dissolved in common solvents such as DMSO and THF.Hyperbranched PPS/PPS fiber was prepared by blending the raw material with twin-screw extruder. Non-isothermal crystallization test indicated that hyperbranched PPS could serve as heterogeneous nuclear agent during the course of crystallization to accelerate the crystallization rate and increase the crystallization temperature. In addition, the addition of hyperbranched PPS could enhance the thermal stability and crystallinity, and as a result to extend its ranges of application temperature and improve the mechanical properties. Hyperbranched PPS could form numerous of entanglements, and benefit to the transportation of stress to form interface structure with higher mechanical properties; therefore the toughness of matrix get enhanced. The adding amount should be in the range of 3 to 4%. During the modification of rheologicai behavior, hyperbranched PPS can decrease the departure of PPS melt from Newtonian fluid. During the blending, hyperbranched PPS with sphere like molecule acted as surface active agent and migrated to the surface of linear PPS melt owning to the wall attachment effect. The friction force between melt and capillary can be decreased and as a result, PPS melt shows a much lower apparent viscosity at same shear rate and lower temperature. In this way, rheologicai behavior could be improved to obtain PPS fiber with outstanding mechanical properties with tensile strength of 4.15 cN/dtex.