Modification Of Natural Barite Filler Mechanism

Barite (Barium sulfate) is a crude rhombic salt; it is a neutral filler. Now, it is becoming an important functional filler because of its electric insulation and magnetic shield. Our previous research found that when the barite was used as filler, it had an important advantage that the high filling percentage can be achieved, and some may even exceed 50%. In this paper, we chose engineering plastics polycarbonate (PC) and polyphenylene sulfide (PPS) as the carriers, systematically studied the rheological behavior of barium sulfate modified polycarbonate composite material and crystallization behavior of the barium sulfate modified PPS composite material, discussed their reaction mechanism. The main content and the results were as follows:1. Studied the rheological behavior of PC/BaSO₄ composites. Found that only 1%-5% of BaSO₄ which were added in PC can greatly reduce the melt viscosity of the PC, thereby improving the high-temperature processing mobility of PC. In addition, the adding barium sulfate makes the shear-thinning behavior more obvious, and the composites indicated the solid-like behavior at the low frequency region. We established a rheological model. The result of curve fitting between experimental data and the prediction of rheological mode indicated that the rheological behavior of PC/BaSO₄ composites could be well described by this rheological mode. We calculated the activation energy of the composites and concluded that the addition of BaSO₄ reduced the activation energy of the composites. The activation energy reduced from 101.7 kJ·(mol·K)^-1 to 45.3 kJ·(mol·K)^-1 when the volumn fraction of BaSO₄ was 1.38%. Using logG'～logG" curve and the temperature dependence, we explored the phase structure of melt blend.2. The XPS and FTIR analysis indicated that there is strong interaction between Ba²⁺ of barium sulfate particles and the carbonyl of polycarbonate matrix, which resulted in the split of the infrared absorption peak of the carbonyl and made Ba 3d5 orbit shift 3eV to lower energy. We thought the reaction reduced the flexibility of the polymer molecular chain and the density of entanglement points. It resulted in the reduction of the composite's viscosity and the rheology enhancement of PC/BaSO₄ composites.3. Non-isothermal crystallization behaviors of PPS/BaSO₄ composites were studied by the Mo equation. The results showed that when the contents of barite were 10%-40%, Mo equation could characterize the non-isothermal crystallization behavior of PPS and its composites. At the same cooling rate, the crystallinity of the composites decreased. Barium sulfate particles have obvious nucleation effects. The composites show low induction period, high crystallization rate and short half crystallization time. In addition, we had studied the crystal conformation of PPS by the polarized light microscopy.4. We had prepared one new type of suspension containing natural barite and PPS. The coating had good impact strength and anticorrosion properties. The impact strength of the coating was higher than 50 kg·cm.