Poly(trimethylene terephthalate)/magnesium hydroxide composites with on-demand thickening at high temperatures

Magnesium hydroxide, when melt extruded with poly(trimethylene terephthalate) (PTT) at low concentrations (1–3 wt.%), can be melt processed during extrusion and injection molding. When the polymer is heated in the melt to 295°C, the viscosity of the composite behaves similarly to control samples and...

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Bibliographic Details
Published in:Fire and materials 2014-03, Vol.38 (2), p.174-181
Main Authors: Messmore, Benjamin W., Zudans, Andrew W., Pottiger, Michael T., Berl, Anna G.
Format: Article
Language:English
Subjects:
Applied sciences
Building technical equipments
Buildings
Buildings. Public works
char
Exact sciences and technology
Fire behavior of materials and structures
Fire protection
flame-retardant
flammability
magnesium hydroxide
magnesium oxide
Materials
modifier
Paints and renderings. Protection products
Plastics
poly(trimethylene terephthalate)
polyester
viscosity
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Summary:Magnesium hydroxide, when melt extruded with poly(trimethylene terephthalate) (PTT) at low concentrations (1–3 wt.%), can be melt processed during extrusion and injection molding. When the polymer is heated in the melt to 295°C, the viscosity of the composite behaves similarly to control samples and the viscosity decreases as a function of temperature. When the temperature of the composite is raised above 295°C (above the normal processing conditions for PTT), a significant change in the melt rheology of the composite is observed relative to unfilled compositions. This change in melt rheology coincides with the decomposition temperature of magnesium hydroxide and formation of magnesium oxide, a common thickening agent employed in unsaturated polyester resins. Lower processing temperature polyesters, including PTT, enable processing of the polymer in the presence of magnesium hydroxide under normal conditions. The viscosity modifier ‘turns on’ when the composite sees elevated temperature where magnesium oxide is known to form. The magnesium oxide is hypothesized to interact with PTT carboxyl end groups, providing the observed increase in viscosity. The rheological response observed in the composites is dependent on the concentration of magnesium hydroxide. During burning, the viscosity modifier results in a non‐dripping formulation of PTT. Copyright © 2012 John Wiley & Sons, Ltd.
ISSN:0308-0501
1099-1018
DOI:10.1002/fam.2171