(363g) Hybrid Polymer Nanocomposites with Low Flammability and Enhanced Mechanical Strength for Transport Applications**

Hybrid polymer nanocompositeS with low flammability and enhanced mechanical strength for transport applications

Stephanos F. Nitodas (1)*, Javier Sacristán (2) and Gemma Ibarz (3)

1. Glonatech S.A., VIPE Lamia, Greece and 14 West 23^rdSt. New York, NY 10010, USA, Tel.: +302118000980

*E-Mail: snitodas@glonatech.com

 2. Acciona Infraestructuras, Calle Valportillo II, 8. Polígono Industrial de Alcobendas, 28108 Alcobendas, Madrid (Spain). Tel.: +34 917912020, Fax: +34 917912101

3. Instituto Tecnológico de Aragón, calle María de Luna 7-8, 50018 Zaragoza (Spain). Tel.:+34 976010021, Fax: +34 976016201

The introduction of composite materials in the primary and secondary structures of marine vessels increased in the last ten years, after the latest SOLAS (Safety of Life at Sea) rule that allows construction of commercial ferries and cruise ships with other materials than steel, which can provide same safety levels. In this sense, low FST sandwich structures are the key factor to build lightweight, reliable, stiff and durable vessels with lower maintenance costs. Sandwich structures can also be applied to other fields such as construction.

The main aim of this research work is the development of polymer foams from polyvinyl chloride (PVC) that will serve as the core of sandwich structures. The foam is enhanced with modified nanoparticles consisting of either a two-component flame retardant system [Layered-Double-Hydroxides (LDHs) in conjunction with synergistic organophosphorous compounds] or high-purity multi-wall carbon nanotubes (MWCNTs)[1]. MWCNTs intrinsically exhibit flame retardancy. There are several studies investigating CNTs as flame-suppressing additives[2]. Various MWCNTs-polymers were examined and it was shown that 1%-5% CNTs addition results in decrease of heat release rates for polypropylene and EVA from 2800 kW/m² to 700 kW/m² and from 475 to 400 kw/m², respectively.

Phosphorous-based-onium compounds were grafted on the surface of LDHs. Pristine MWCNTs and MWCNTs modified with carboxyl groups were also tested as additives[3]. The nanoparticles were characterized with XRD, FTIR, XPS and SEM in order to define their attributes and the modification level. The PVC-based nanocomposites were prepared via extrusion after thorough determination of the processing parameters for attaining optimal dispersion of nanoparticles. Structural characterization of the composites was performed with XRD and SEM. The thermal stability and flame retardancy were determined by TGA and the Limited-Oxygen-Index method, respectively. The results showed enhanced thermal stability for LDHs whereas the flammability of MWCNTs-PVC composites was found to drastically ameliorate relative to that of PVC.

The PVC-based composites exhibited enhanced Young’s modulus compared to PVC, due to the reinforcing effect of the chosen flame-retardant systems, as well as improvements in compressive strength of more than 200% with respect to the values of pristine PVC. Taken under consideration the obtained data, novel hybrid PVC composites with combination of LDHs-MWCNTs were synthesized in addition to the initial nanoparticles formulations. Their characterization revealed remarkable improvement in both thermal and mechanical properties. The characterization results are presented and discussed.