A series of plastic materials from recycled polyethylene (PE) and oyster-shell powder were prepared to test their fire-retardant properties with an aim of finding a practical way of waste recycling. Oyster-shell powder was found to be mainly composed of calcium carbonate and it decomposed to calcium oxide and carbon dioxide at temperature higher than ϳ800°C, thus preventing fire from access of oxygen by the produced carbon dioxide. This fireretardation mechanism is environmental-friendly, since another available method, the inclusion of halogen-containing compounds, normally generates toxic chemicals like dioxine during incineration. To improve mechanical properties of this composite material, surface of oyster-shell powder was coated with cetyltrimethylammonium bromide (CTAB). Flame retardation and the mechanical properties of these composite resins were analyzed.
Nanocomposites from polyurethane (PU) and montmorillonite (MMT) were prepared under meltmixing condition, by a twin screw extruder along with a compatibilizer to enhance dispersion of MMT. MMT used in this study was Cloisite 25A (modified with dimethyl hydrogenated tallow 2-ethylhexyl ammonium) or Cloisite 30B (modified with methyl tallow bis-2-hydroxyethyl ammonium). Maleic anhydride grafted polypropylene (MAPP) was used as the compatibilizer. XRD and TEM analysis demonstrated that melt mixing by a twin-screw extruder was effective in dispersing MMT through the PU matrix. The PU/Cloisite 30B composite exhibited better interlayer separation than the PU/Cloiste 25A composite. Nanoparticle dispersion was the best at 1 wt % of MMT and improved with compatibilizer content for both composites. Properties of the composites such as complex viscosity and storage modulus were higher than that of a pure PU matrix and increased with the increase in MMT content, but decreased with the increase in compatibilizer content.
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