Effect of Temperature on Morphology and Mechanical Properties of Terephthalate Co-Polyesters Processed by Lamination Extrusion Coating and Film Casting

Aim of the Work Nowadays polymers are materials of common use, both for commodities both for advanced specialized applications, such in biomedical or nanocomposite elds. The great success of these materials is due to dierent factors, such as availability of raw materials, ease of processing, lightness, low costs, a great variety of properties, etc. Moreover, the polymer industries has developed in a signicant and rapidly way new synthetic pathways and new techniques and methods of forming, depositing, coating, processing these materials in advantageous ways. Today polymer processes, such as extrusion, injec- tion moulding, thermoforming, and casting, provide parts and products with controlled and specic shapes and sizes. To obtain these important successes materials engineers must have a broad knowledge of fundamental principles of polymer science and follow the requests of products that must be cheaper and higher performing. Therefore, the development of high speed production processes and new machines allow improvements in polymer characteristics and performances. Film extrusion is one of the most popular polymer processing technique and lms are widely used in our daily life. Recently, because of the competition with dierent materials, lm production have moved to higher productivity, high speed lines and high quality. A few examples of this economically driven technology are the production of very thin lms, dimensionally stable, and multi-layered lms for applications in food packaging. Extrusion coating is the most important process used to realize multilayer composites, where pa- perboard is coated with plastics to combine the mechanical properties of the paperboard with the barrier and sealing properties of plastics. In this way paperboard is suitable for a number of specially demanding applications. The extrusion coating is used to produce materials for liquid and solid food packaging, industrial packaging, building, medical and hygiene purposes. The commonly used resin used in extrusion coating is polyethylene (LDPE). However, the recently decreasing cost of terephthalate polyester resins, above all polyethylene terephthalate (PET), has at- tracted a certain interest in manufacturing paper based structures that comprehend layers of extrusion coated PET. However, the extrusion coating process has grown and optimized for handling and processing PE resins. The dierences in properties and processing conditions between polyolens and polyesters make very hard the setting of machinery used for the process. A lot of parameters and congurations have to be again evaluated and optimized in order to substitute PE with PET. More specically, PET presents the drawback that it is obtained by extrusion coating in an amorphous state and becomes brittle as a function of time spent at room temperature. The attempt to induce a thermal crystallization in PET during the process is not eective because crystals not oriented have poor mechanical performances. Only semicrystalline and bi-oriented lms have good properties, stable over the time, but bi-orientation is not achievable by extrusion coating. 7