Composite PVC materials with enhanced thermal stability on the basis of nanofillings

The company Compuestos y Granzas, S. A. (CYGSA), which is acting as the co-ordinator, and the L'Urederra R+D Centre are also involved in the project. The researchers from the Public University of Navarre are Antonio Gil-Bravo and Sophia A. Korili, lecturers from the Department of Applied Chemistry, and Saioa Albeniz, the project assistant. They all belong to the Environmental Technologies and Applications Research Group.

The nanofilled polymer composite materials are developed through the synthesis and treatment of nanoclays inserted into the matrix of the polymer. According to Antonio Gil, "the main aim is to improve their photostability properties: ultraviolet rays, responsible for the accelerated degradation of the polymers, cause discolouration and loss of performance of the materials, thus shortening their useful life. Inserting molecules capable of absorbing light radiation increases the composite's resistance to UV radiation."

The molecules tend to be of an ionic type and can be inserted using various methods, such as ion-exchange. Depending on the chosen option, the photoresistance properties and the range of absorption in the UV-visible region may be altered, which means that each method can be adapted to the two main groups of material synthesis applications: opaque plastic nanocomposites, and coloured products. In the latter group, the desired colour in the final product will determine the type of colouring molecule used.

Enhancement of refractory properties

The second objective is to enhance the refractory properties relating to the capacity of the nanofillers to act simultaneously as mechanical and flame-retardant reinforcements. "The flame retardants used are currently based on aluminium or magnesium hydroxides or on flame-retardant plasticisers and high loading percentages need to be used, which leads to a deterioration in the mechanical properties of the final composite," says Prof. Gil.

The new nanofillers being developed can increase the thermal stability of the material, reduce smoke emission in the case of combustion, and halt the deterioration of mechanical properties caused by other fire retardants. "Thanks to the synergy effect between the nanofilling and the flame retardant material, it is even possible to reduce the proportion of the conventional flame retardant materials used in the standard formulations."

Finally, the improvement in the permeation properties of the materials can pave the way, thanks to the addition of the nanofillers, for the development of new formulations with barrier properties against gases and volatile organic molecules with low molecular weight. This way, an attempt will be made to reduce the diffusion of gases through the modified polymers.

The Vinilclay project is receiving funding from the Spanish Ministry of Science and Innovation within the framework of the INNPACTO programme, and is co-funded by the European Regional Development Fund (FEDER); it is scheduled to continue until the end of this year.

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