| In this paper, light calcium carbonate as the main raw material was modified in the water and n-Butanol mixed solvent system by wet surface chemical modification. Two modifiers are the single aluminum coupling agent and the composite modifier (aluminum coupling agent+stearic acid), respectively. The characters of modified calcium carbonate were investigated by the contact angle, viscosity, active ratio, stability, infrared spectroscopy (IR) and thermal analysis (DTA/TG). The experimental results indicated that the surface of the calcium carbonate powder changed from the hydrophilic property to the hydrophobic property. Then study the mechanical performance after it filled in the low-density polyethylene(LDPE). The results are listed as follows.1. Light calcium carbonate powder is modified by aluminate coupling agent(ACA). The modification technology of light calcium carbonate powder was studied by parameter optimization tests in the process with the contact angle of the modified calcium carbonate as criterion. The process was done by changing modification temperature, modification time, rotation speed, ACA dosage and n-Butanol percentage. Optimized conditions for modification of the surface were the following:modification temperature was at 110℃, rotation speed was at 650 r/min, modification time was 30 min, ACA dosage was 1.2wt% and n-Butanol percent was 20v%.Comparatively speaking, the ACA dosage and n-Butanol percentage are the major influencing factors. The contact angle of modified CaCO3 powder obtained in optimum conditions is 134.5°. The modified calcium carbonate was studied by infrared spectroscopy (IR), thermal analysis and their active ratio and viscosity were tested. The experimental results indicate that the surface of the calcium carbonate powder changed from the hydrophilic property to the hydrophobic property and that there are chemi-sorption and physic-sorption between the calcium carbonate powder and the modifier.Different proportions of modified calcium carbonate filled in LDPE through the first and second plastic refine. And analyze the mechanical performance of LDPE filled by calcium carbonate. The results showed that with augmentation of the component of modified calcium carbonate, the tensile strength and yield strength remained stable, the breaking elongation and melt flow rate decreased, while the tensile modulus, hardness, bending modulus and bending strength were improved. It can be see that with the increase of the component of modified calcium carbonate, the strength, hardness and processing properties are improved correspondingly, but the toughness decreases. Among them, the best filling volume of modified calcium carbonate is 20wt%.2. Light calcium carbonate powder is modified by aluminate coupling agent and stearic acid as composite modifier. The preparation of process parameters of modified calcium carbonate is studied by orthogonal experiment with the contact angle as criterion through changing temperature, stirring speed, aluminate coupling agent dosage and stearic acid dosage. The optimal reaction conditions are as follows: aluminate coupling agent dosage of 1.Owt%,stearic acid dosage of 0.8wt%,stirring speed of 650r/min and modification temperature of 100℃.And the contact angle of modified calcium carbonate is mostly influenced by aluminate coupling agent dosage, then by stirring speed and stearic acid dosage, and least by temperature. The contact angle of modified CaCO3 powder obtained in optimum conditions is 136.5°. The results of active ratio and viscosity show that after modification the hydrophilic surface of calcium carbonate is changed into hydrophobic surface. IR analysis shows that surface active agents are attached to calcium carbonate.Different proportions of modified calcium carbonate filled in LDPE through the first and second plastic refine. And analyze the mechanical performance of LDPE filled by calcium carbonate. The results showed that with augmentation of the component of modified calcium carbonate, the variation trend of the mechanical performance is similar to that of LDPE filled by calcium carbonate, which modified by aluminate coupling agent, and the performance is improved slightly. The best filling volume of modified calcium carbonate is 20wt%. Add a certain amount of elastomer EVA into the LDPE material filled by modified calcium carbonate, the strength, hardness, toughness and processing properties of the materials can all be improved well.SEM results show that with the addition of modified calcium carbonate, the toughness of the LDPE material is much better than that with unmodified calcium carbonate. |
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