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Nano- SiOx composite spray fogging agent technology and performance of

Author: LuoMaoXian
Tutor: LiuDongHui
School: Kunming University of Science and Technology
Course: Chemical Engineering
Keywords: antifogging-agent anti-fog dripping nano-SiO_x compound formula
CLC: TQ420.7
Type: Master's thesis
Year: 2009
Downloads: 114
Quote: 2
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Abstract

With the improvement of the living standards and the extensive use of the agricultural greenhouse films (mainly vegetables, flowers), the antifogging and dripping problem of the greenhouse films have attracted more and more attention. At present, the normal interior-adding antifogging agents are widely used in agriculture films for its many merits, such as processing conveniently with other additives and masterbatch, effectively improving greenhouse environment with its dripless performance which can meet a growth cycle of most crops. However, compared with the life the agriculture films (about 2-3 years), the antifogging life length of this type (about 3-6 months) was shorter, so it can not completely meet the requirement of the dripless performance. For that, many researches have been focused on out-coating antifogging agent. With the weaker surface binding strength between the films and antifogging agent which resulted in the rapid loss of the antifogging agent, the out-coating antifogging agent developed now can not completely meet the need of crops growth. In this paper, we add nano-particles into the antifogging agent inorganicly in order to improve the antifogging and dripping performances of the greenhouse films for its characteristics on the basis of our preliminary work. The relevant technology and antifogging mechanism are also studied. The results can provide a practical guidance for how to enhance the combination of the film surface and the coating antifogging agent. At the same time, they can provide a new idea to extend the antifogging durability and expand the application direction. The main contents in this paper are as following:1. Directed against the particularity of the coating antifogging agent and the characteristics of the nano-particles, the effect of three factors (particle diameter, surface area and surface hydroxyl content) on dripless performance were analyzed and discussed. Based on this, we chose DPI nano-SiOx as additive which was afforded by Zhejiang Hongsheng Materials Technology Co. Ltd.2. We chose three hydroxy compounds with different structures or amphiphilic compounds as the surface treatment agents of nano-silica particles, and using the quantitative mixing and standing observation to study the compatibility of the antifogging agents with surface treatment agents. The selected antifogging agent is hydroxy compound, And in our research, the dispersed system was uniformity and good stability when the mass ratio of the nano-SiOx and antifogging agent is below 5:100. So antifogging agents can be directly used as a nano-SiOx surface treatment agent.3. The surface treatment technique of nano-SiOx has been also studied. Four main factors which influenced nano-SiOx homogenized in antifogging agent have been designed in a orthogonal test. The four factors are as follows:the mass ratio of nano-SiOx and antifogging agent (factor A), the shear dispersion speed (factor B), the time of shear dispersion (factor C), and the last one, the time of disperse system treated by ultrasonic (factor D). We modified the test standard GB/T 19603-2004 in order to improve its precision. According to this method, we tested the antifogging and dripping properties before and after soaking with water. Target assess is the first drop time and the every ten droplets’ time. Intuitionistic analysis of the results showed that, at the early stage, the factor A was the most significant factor for greenhouse films performance. The best process parameters are:the mass ratio of nano-SiOx and antifogging agent is 5:100, the shear dispersion speed is 1.6×104 rpm, the time of shear dispersion is 300 s, the time of disperse system treated by ultrasonic is 2700 s. With this condition, the first time of the greenhouse films was 380.29 s, the average of ten droplets’ time was 231.09 s, and the dripping curve was very flat. At the later stage, factor C was predominant. And the best technique condition:the mass ratio of nano-SiOx and antifogging agent was 1:100, the shear dispersion speed is 1.6×104 rpm, the time of shear dispersion is 120 s, the time of disperse system treated by ultrasonic is 1800 s. Under this condition, after the sample was soaked with water, the first time was as short as 417.81 s, the average of ten droplets’time was 256.53 s, and the dripping curve was also very flat.4. Several analytic methods such as TEM, AFM were adopted to characterize the dispersion of nano-silica particles and the microcosmic morphology and structure of the films surface before and after soaked. The results showed that the nano-SiOx can improve the antifogging and dripping performances of the out-coating antifogging agents, because it was dispersed evenly in antifogging agents by the strong shear dispersion and ultrasonic dispersion, and can strengthen the binding force of the greenhouse films with antifogging agent molecules for its smaller particles size, larger specific surface area, and higher surface activity owing to its higher surface hydroxyl groups density. The nano-SiOx particles play a bridging role. It can fix antifogging agent molecules at the greenhouse films’surface and slowdown the rate loss of the antifogging agent with water, which extended the antifogging agent durability and dripping properties.

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CLC: > Industrial Technology > Chemical Industry > Reagents and the production of pure chemicals > General issues > Product testing,analysis and identification
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