Study On The Preparation And Characterization Of Anti-oxidizing Polyphenylene Sulfide

Polyphenylene sulfide (PPS) is an engineering plastics with special high performance. PPS boasting excellent heat resistance, flame resistance, chemical resistance, electrical insulation and good mechanical properties, it ranks the sixth among engineering plastics. PPS is widely used in automotive, electronics, machinery, petrochemical, military, and aerospace. Polyphenylene sulfide fiber, featured with heat-resistance, chemical resistance, flame resistance (LO1>35) and high-performance, can be widely used in high-temperature flue dust, fire insulated clothing,etc, and it developed rapidly in recent years. However, due to the structural characteristics of the molecular of polyphenylene sulfide, the PPS has poor thermal stability of oxygen, which limits its application scope and field. Therefore it is of practical importance to study the antioxidant modification of PPS.In this paper, polyphenylene sulfide (PPS) was synthesized through reactions of sodium sulfide and P-dichlorobenzene in N-methylpyrrolidone. Then, the structure and crystal properties of the PPS were investigated by Fourier transform infrared spectrometry (FTIR), Raman spectrometry, and X-ray diffraction (XRD) analysis. The thermal properties and the thermal degradation behavior of the PPS were investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC). The rheology of the PPS was studied by the Physica MCR-301rotary rheometer. The anti-oxidizing PPS was prepared through the addition of different anti-oxidant and the antioxidant property was tested by the TGA and the DSC. Kissinger method, Flynn-Wall-Ozawa method and Coast-Redfern method were applied to describe the thermal degradation kinetics of the PPS and anti-oxidizing PPS.The results showed that the crystal water of the sodium sulfide must be removed. The polymerization of the PPS could be divided into two stages, in the first stage, the reaction temperature should be220℃and the time should be3-4h, and in the second stage, the reaction temperature should be260℃and the time should be2h. The melting temperature (Tm) of the PPS was at285℃, which had a high temperature. In nitrogen atmosphere, the maximum decomposition rate temperature was at540℃, and it showed that the product had a high thermal decomposition temperature. From the test analysis of XRD, it showed that the crystallization of the polymer had a good performance. From the test analysis of Fourier transform infrared spectrometry (FTIR) and Raman spectrometry, it showed that the product of the polymerization was a typical structure of polyphenylene sulfide, and the polymer system was not containing the S-S.The test results of the rheological properties showed that the PPS had a high molecular weight. With the temperature improved, the melt viscosity of the PPS was to first reduce and then increase. When in the initial heating stage, molecular motions of the PPS increase, then the viscosity reduce. The incremental of the viscosity caused by the oxidation and the cross-linking was greater than the descend that cause by the rise of the temperature, therefore, when the PPS maintain a period of time in the high-temperature environment, the viscosity of the PPS showed a rising phenomenon.Several antioxidants were added into the PPS. When the MMT and the antioxidant4426were added into the PPS, the oxidation induction temperature was higher nearly35℃than the pure PPS. To sum up, the composite antioxidant has a good effect of resistance to thermal oxidation aging of PPS.The PPS and anti-oxidizing PPS on the thermal behavior were investigated through thermogravimetric analysis (TGA) in the nitrogen atmosphere. The thermal decomposition was a step weight loss process with the largest weight loss occurred between the500-600℃and the total weight loss was45%-50%.Degradation activation energy (Em) of the anti-oxidizing PPS was lower than the pure PPS, but when the degradation extent(a) was0.2-0.45, the Em of the anti-oxidizing PPS was higher than the pure PPS. After modification treatment, the performance of PPS to resist thermal degradation had been improved. S8function was ensure to be the thermal degradation reaction function, and ensured the thermal degradation mechanism of PPS and anti-oxidizing PPS were both phase-side reaction mechanism. The thermal degradation kinetics equation showed that, with the addition of antioxidant4426, the thermal degradation reaction rate decreased, only when added antioxidant content of0.1%, the Em kept the highest.