Research On Modification Of Polyphenylene Sulfide And Its' Pipe Processing

The polyphenylene sulfide (PPS) is a super engineering plastic with excellent heat stability, outstanding wearability and good mechanical properties.Its corrosion resistance is just lower than PTFE.It can be used as high temperature resistant pipe in petroleum, chemicals, metallurgy and mining.However,compared to PE and PVC,it's harder to extrude PPS pipe,because it has a narrow processing temperature and less toughness.So,it has been a difficulty to produce high temperature resistant and flexible pipes.The PPS was toughened by SEBS-g-MAH and PA6. A dedicated extrusion die for PPS pipe was designed, and the extrusion process was simulated by Polyflow. The flow field was also analized in the flow channel.The paper studied the effect of different techniques and modified materials on extrusion molding of PPS pipe.Then the effect of SEBS-g-MAH and PA6 on Vicat softening point of PPS pipe.The paper's main works and research results were as follows.1 The toughening modification of PPSThe PPS was toughened by SEBS-g-MAH and PA6 in the methods of melt mixing. The rheological properties, crystallization and melting behaviors, heat stability and mechanical properties of different blends were researched.(1)The melt flow rate (MFR) of PPS/SEBS-g-MAH blends increased at the beginning, then decreased with increased content of SEBS-g-MAH.The melt viscosity of blends was smaller than PPS's.Heat stability of blends was reduced, but it influences very little on the processing tempreture.The crystallinity decreased while the material toughness increased clearly.When the content of SEBS-g-MAH was 40%, notch impact strength of blends was 13.1 KJ·m-2—three times notch impact strength of pur PPS.(2) The melt flow rate of PPS/PA6 blends decreased. When the content of PA6 was 50%,the MFR was 17.5 g/10min. The melt viscosity of blends increased,and the crystallinity and heat stability decreased. Notch impact strength and the elongation at break point of PPS/PA6 blends rosed. When the content of PA6 was 50%, notch impact strength of blends was 7.2 KJ-m"2.2 Design of the dedicated die for PPS pipe and simulation analysis of the extrusion dieAccording to the characteristics of the material of the PPS, the special die for PPS was designed. Then the flow field in the extrusion process of the tube was simulated by POLYFLOW software and the following results were obtained:Along the extrusion direction, the pressure in the die gradually decreases,as well as the differential pressure was increased or decreased due to the change of the flow channel shape, and the velocity distribution along the extrusion direction was uniform. Therefore, from the point of view of extrusion speed,the design of the die and the temperature conditions have been to set reasonably. In the passage, the melt temperature near the central part was higher than that near the wall location, which was due to shear heating effects in the internal melt.3 Extrusion molding of PPS pipeIt was found that the temperature of the die is vitally important to the quality of the molding. Studies concluded that, when forming temperature of the die reached about 275?, the PPS tube could be extrusion molded; if the forming temperature of the die was below 270?, die overflow or pipe rupturetiming will occur caused by the die plugging and head pressure surge head; when forming temperature of the die reached about 280?,the extrusion tube was unable to finalize the design. The study also found that either PA6 or SEBS-g-MAH was added to the corresponding composite material, the Vicat softening point will be lower than PPS, still much higher than the general plastics.