Re-Aggregation Of Antifoaming Process In Polymer-Based Nano-Composite Prepared By In Situ Bubble Stretching (ISBS) Method

With the development and application of composite, research of nano-composite has become new focus in polymer science. Because of little particle size, high surface energy and unstable state in thermodynamics, nano-particles is apt to form aggregation in production, storage and usage, thus it will loss the function of nano-particles. Therefore, the dispersion of nano-particles is an important factor to improve the nano-composite properties and decrease its filling amount. People have attempted many methods to solve the dispersion problem; however it is still one of bottleneck problem in preparation of polymer-based nano-composite. Professor Daming Wu put forward a new method which named In Situ Bubble Stretching method, abbreviation ISBS. In-Site Bubble Stretching (ISBS) is a method for dispersing aggregated nano-particles in polymer melt by rapid stretching action in the fast expansion of bubbles. The results show that it can generate high stretching velocity reached to 10⁶s^-1 in polymer melt, an improvement of about two orders of magnitude over general mechanical dispersing method.By the ISBS dispersion, bubbles still exist in the dispersed nano-composite system and it can influent material's properties. So a defoaming course is essential. Whether the dispersed nano-particles will re-aggregate again in defoaming course and subsequent molding process is an important factor which can determine the dispersion result and the properties of composite.In this paper, we talk about the re-aggregation in defoaming course and subsequent molding process based on summarizing studies of others, which concluding the studies of ISBS dispersion rules and ability. Make PPR as resin matrix and nano-CaCO₃ and nano-Mg(OH)₂ as filling nano-particles. First, use two-screw extruder to mix the mixture of polymer and nano-particles and make granulation. Then use single-screw extruder to foam the composite under a controlled die pressure. At last, use injection molding machine to made the standard sample strip and investigate mechanical properties, during this course the bubble can be defoamed making use of the function of self-exhausting.Use the software of Image-Pro Plus to analysis and compute the FE-SEM electronic microscope photograph and then analysis and compare the data of impact property and tensile property, we can conclude that:1. ISBS method is an effective method to disperse nano-composite aggregation. Under a certain addition of nano-particles, the nanocomposite system of PPR/nano-CaCO₃ and PPR/nano-Mg(OH)₂ can be dispersed homogeneously.2. After the defoaming and molding process, the nano-composites made by ISBS method don't found obvious re-aggregation.3. After the defoaming and molding process, the impact property highly improve with the addition of nano-particles. At the same addition, it is much higher than that made by two-screw extruder directly. The impact property reach maximum value on certain addition and it will decrease with the increase of addition.4. In the dispersed nano-composite system, whether the nano-particles will re-aggregate again is determined by the addition of nano-particles in the composite system after the defoaming and molding process. When the addition is up to a certain value, the impact probabilities of nano-particles in polymer will increase, when it is easy to re-aggregate at the critical value.