Tesis doctoral de María Del Pilar Casas Carne
Cars, trucks, tractors, airplanes all need tyres as essential component to work. Unfortunately, due to its continuous use, tyres suffer from wear and have a limited lifetime; therefore, they must be changed every certain time becoming end of life tyres (eol tyres). Paradoxically tyres are formulated to withstand difficult conditions and among other raw materials, they contain vulcanizated rubbers, high amount of stabilizers and other additives that turn tyres into non biodegradable material. Until 2006, disposal of eol tyres in landfills was a common practice but it was banned by the european community (directive 1993/31/ec). This european legislation together with an increasing environmental consciousness has instigated researchers to find applications for 3.4million tonnes of used tyres generated per year in europe. Some extended uses for eol tyres are energy recover and civil applications but the use of tyres after separation and grinding processes (material know as ground tyre rubber – gtr), has increased during the last decade. Physical and chemical properties of eol tyres make them an interesting material for the international research community focused today on finding new ways to recycle tyres for value added applications. a good option to recycle big volumes of discarded tyres is using gtr particles as filler in thermoplastic matrixes, although this is a difficult task due to the low compatibility between the two materials. The surface characteristics of the gtr particles are responsible of this low compatibility. Despite these facts, the particle size obtained from standard industrial grinding processes is between 400 and 600¿m. These particles are too large to be entrapped easily in polymeric matrixes. These characteristics in conjunction with the fact that gtr is made of highly crosslinked rubber with difficulties to react chemically to other materials, make gtr a material very difficult to work with. the present thesis deals with the study of different compatibilization methods for an injection moulding grade of high density polyethylene (hdpe) and gtr obtained from standard industrial grinding process. The hdpe resin was chosen due to its wide range of injection moulding applications. The aim is to explore different methods to mix these two materials and obtain optimum mechanical, thermal and morphological properties for injection moulding applications. The composites are optimized to obtain the highest gtr amount, adequate processability and minimum cost. after a preliminary study of the composites based on gtr and hdpe, three different methods to improve the adhesion between these two materials are studied. The first method consists in an oxidizing treatment on gtr particles surface in order to promote mechanical anchoring. In the second method the influence of wetting additives and waxes is studied. These substances reduce interfacial tension between gtr particles and hdpe matrix. The third and last method, study the influence of ethylene propylene diene monomer (epdm) addition with and without peroxides. In this method, gtr particles are encapsulated by epdm and this effect can be boosted by the use of peroxides. The composites properties are quite different depending on the used method. after a comparison of the composites obtained by the three different compatibilization methods, it is found that the one with 30% of epdm plus two peroxides, corresponding to 30% gtr + 40% hdpe + 30% epdm + 0.5% trigonox 311 + 0.1% dicumyl peroxide fulfil the objectives of the thesis. This composite has good adhesion between gtr and hdpe that results in high elongation, it is obtained by a cheap compatibilization process and contains a high amount of recycled tyres (30%), it is easy to process, and the most important thing, it represents a new route to recycle scrap tyres for a value added application.
Datos académicos de la tesis doctoral «Study of compatibilization methods for high density polyethylene and ground tyre rubber: exploring new routes to recycle scrap tyres«
- Título de la tesis: Study of compatibilization methods for high density polyethylene and ground tyre rubber: exploring new routes to recycle scrap tyres
- Autor: María Del Pilar Casas Carne
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 25/03/2010
Dirección y tribunal
- Director de la tesis
- Francisco Javier Cañavate ávila
- Tribunal
- Presidente del tribunal: pere Pagés figueras
- Juan Lopez Martinez (vocal)
- Ana isabel López macipe (vocal)
- félix ángel Carrasco alonso (vocal)