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Structure and Characterization of Room Temperature Self-crosslinked Acrylonitrile-butadiene-styrene

Author: XueWenJuan
Tutor: WenZuoJiang
School: Suzhou University
Course: Materials Science
Keywords: crosslinked polyolefin ABS resin crosslinking mechanism mechanical properties thermal behavior
CLC: TQ325.2
Type: Master's thesis
Year: 2011
Downloads: 17
Quote: 0
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Abstract


ABS is a kind of most widely used engineering thermoplastic in the world, with a big versatility of application possibilities due to superior mechanical properties, chemical resistance, ease of processing and recyclability. However, ABS has certain disadvantages, e.g., low thermal stability, poor flame and weather resistance. In an effort to tackle these disadvantages, a large number of reports have focused on increasing the glass transition temperature and thermal stability of ABS as well its component polymers under various conditions. Crosslinking is an efficient way to achieve a better thermal stability of polymer. Three commercial methods were used for the crosslinking of polymer: peroxide crosslinking, radiation crosslinking, and crosslinking through the grafting of silane followed by moisture crosslinking.Silane crosslinking polyolefin was obliged to immerse the product in warm water or steam vapor to complete crosslinking reaction, which has several drawbacks such as slow crosslinking velocity, complex crosslinking process and waste of energy. In addition, the crosslinked degree is directly influenced by the thickness of products. In order to reduce the process, Self-crosslinked acrylonitrile-butadiene-styrene (ABS) at room temperature was prepared by silane crosslinked method in a twin-screw reactive extruder using aluminium hydroxide as a crosslinking agent and 2, 3-dimethyl-2, 3-diphenylbutane (DMDPB) as an initiator. The crosslinking agent for crosslinking of ABS is aluminum hydroxide which can be decomposed into water and alumina at its decomposed temperature to cause crosslinking of the silane grafted material in the presence of moisture. This method obviates the need for placing the material into water to obtain the diffusion, because the water is developed in the material itself.The mechanism and process for siloxane crosslinked acrylonitrile-butadiene-styre -ne were discussed in this paper. At the same time, the effects of the crosslinking time, a wide range of initiator 2, 3-dimethyl-2, 3-diphenylbutane (DMDPB, 0.5-3.5phr) and crosslinking agent concentration on the gel contents, mechanical properties, thermal stability and thermomechanical behavior of the resulting crosslinked ABS were investigated. The structure and surface characterization of pure ABS and self-crosslinked ABS were studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The gel content was determined by the technique of solvent extraction. Thermal behavior and mechanical properties of the self-crosslinked ABS were studied by thermogravimetric analysis and tensile test, respectively. The room temperature self-crosslinked ABS were melt blended by Haake Mixer. The effects on the equilibrium torque (TQs) with the crosslinking time, blending temperature and the concentration of aluminium hydroxide were studied. And finally we got the following conclusions:1) Room temperature self-crosslinked ABS was successfully synthesized by the extrusion. The mechanism for self-crosslinked ABS technology was put forward. It obviates the need for placing the material into water due to using aluminium hydroxide as a crosslinking agent which develops the water by the chemical reaction.2) The structure character of pure ABS, grafted-ABS and crosslinked-ABS were studied by IR, XPS, Gel content and SEM.3) The thesis investigated the gel content of crosslinked ABS with different initiator concentration as a function of time. With the crosslinking time increasing, the gel percentages of crosslinked ABS increased rapidly to around 27wt% in the first ten days, and the gel percentages increased slowly in the later days. It ranged from 30wt% to 40wt% in the crosslinked ABS added varies content initiator. The maximum gel content of crosslinked ABS is up to 37.2wt%.4) The effects of crosslinking time and initiator concentration, crosslinking agent concentration on mechanical properties of crosslinked ABS were studied. It indicated tensile strength of crosslinked ABS increased differently with diverse initiator concentration and crosslinking agent concentration, after crosslinking for 30 days, the tensile strength, modulus and elongation remained stable. The tensile strength of self-crosslinked ABS increased about 20%, and it reached a maximum at ~1.5phr initiator. As the crosslinking agent concentrations were 0.5phr, 1.5phr and 2.5phr, the mechanical properties of crosslinked ABS was maximum at ~1.5phr crosslinking agent concentration as well.5) The thermal properties of crosslinked ABS had various extents of growths at different crosslinking times. By comparison with the pure ABS, the T0.1 and T0.5 of the crosslinked ABS increased respectively about 20°C and 30°C for crosslinking thirty days. With adding different concentration initiator and crosslinking agent concentration, the thermal stability properties of crosslinked ABS improved greatly in contrast with pure ABS.6) The room temperature self-crosslinked ABS were melt blended by Haake Mixer. The effects on the melting time(tm) and equilibrium torque (TQs) with the crosslinking time, blending temperature and the concentration of aluminium hydroxide were studied. The results showed that tm and TQs of crosslinked ABS increase with the increase of crosslinking time, decreased with the increase of processing temperature. The TQs of crosslinked ABS represented different changes with the various crosslinking agent concentrations.

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CLC: > Industrial Technology > Chemical Industry > Synthetic resins and plastics industry > Polymer resin and plastic > Polystyrene and its copolymers
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