Establishment Of Reactive Extrusion System And Preparation Of Starch-based Superabsorbent Polymer

Starch modification using reactive extrusion is a new technology attracted increased attention since many advantages including high efficiency and low energy. However, the traditional extrusion machine, including reactive extruder, needs to be modified to suitable for the application of starch modification. There is no equipment can be used to modify starch directly. It is needed firstly to establish a system used for starch modification in this work, especially for grafting.Superabsorbent resin is a functional polymer with a certain network structure and hydrophilic groups. It has super-absorbent and water-holding capacity. Starch-based superabsorbent resin was synthesized by graft copolymerization with initiator and crosslinkers, and used starch as the raw material, acrylic acid, acrylonitrile and acrylamide as monomers, starch macromolecular carbon chain as the skeleton. There are many synthesis methods, such as aqueous solution polymerization, inverse suspension polymerization, inverse emulsion polymerization, radiation polymerization etc. Twin-screw extruder is a kind of polymer processing equipment, which has many advantages like high efficiency, less pollution, continuous production and so on. Its combination of barrel and screw can be used as the reaction vessel for polymer physical or chemical modifications. This project used waxy maize starch to prepare starch-based superabsorbent reaction with the extruder. The topic researched the time of the starch in the barrel at different speed, and different water contents to establish the reactive system. Experiments showed that in this process the residence time of the starch, the gelatinization and the phase change related to processing conditions, such as extrusion temperature, the speed of twin-screw, moisture content and so on.The results of this experiment show that by modifying the extruder into a closed system, we can get the anaerobic conditions and feasible reaction time for copolymerization. Acrylamide and starch can be prepared into starch-based SAP by reactive extrusion which will carry out chemical reactions while starch gelatinized. Experiments in this article shows that SAP have poorer performance by reactive extrusion than traditional method, which reflected in water absorption, the water absorption in salt solution and other aspects of the performance. Contents of this thesis include the following:1, Establishing a suitable extrusion reaction system to improve the twin-screw extruder and assemble the combination of twin screw. At the same time we researched the influence of temperature, screw speed, screw combination and the other conditions of the new system in extrusion process of starch, as a guide for reactive extrusion of SAP.2, Preparing starch-based SAP and testing its performance and microstructure by using waxy corn starch as raw material, twin-screw extruder as reaction vessel SAP I tested the superabsorbent resin that was made in the extrusion system in macroscopic properties, thermodynamics etc, and obtained preliminary study on extrusion reaction products.3, Studying morphology of starch in extrusion process and studied particles changes and pasting process of starch by polarized light microscopy, the torque curve etc. By comparing screw torque curve in different conditions, we descripted reactive extrusion process preliminary.