Influence of a novel drying technique on the mechanical per- formance of recycled and virgin PET

GABRIELA CLARISA CAMPOS ; VALERIA PETTARIN; FEDERICO MORALES; ALEJANDRA COSTANTINO

Conferencia; 3er International Conference on Polymer Process Innovation; 2023

About 40% of thermoplastic polymeric materials are currently used in the packaging industry as wrappers and disposable consumer items, such as flexible films and rigid containers and bottles. Regarding bottles, a large part of them is associated with the beverage market, especially carbonated (soda), which is practically monopolized by polyethylene terephthalate (PET). PET then occupies 7.7% of the European market (4 million tons), being the third most used polymer in the packaging industry [1] . It is well known that PET is a polyester resin that must be properly driedbefore processing to avoid hydrolysis reactions. These reactions occur at high temperature in the presence of water, causing the scission of ester groups in PET, which leads to the formation of carboxyl acid, and hydroxyl ethyl ester chain ends [2] . Hydrolysis may modify PET’s processability and deteriorate its mechanical properties [3] . Besides, drying is one of the stages in the PET processing cycle that takes more time and consumes most energy. Reducing energy and production time are fundamental requirements of the current global industrial agenda, in which being environmentally responsible without losing competitiveness and being able to supply social demands is a priority. That is why reducing the energy consumption of each stage of the production cycle as much as possible is still a big challenge for the environmental engineering field. According to the industrial drying methods used, the drying time is between 4 to 12 hours [3] , while the final shaping could take only minutes. Although there are some studies about alternative drying methods such as microwave or vacuum technology, many of them are impractical in technical terms, they do not generate considerable reductions in drying time and/or their implementation in the industrial sector would require a large investment that would not be compensated by its performance. An alternative that may be attractive in terms of drying time reduction and implementation in the PET processing industry is the use of infrared technology as a drying method. This technology is currently implemented in different industries such as food, paper industries, and several more [4–7] . However, it is not yet used on a massive scale for drying polymers. The principle of infrared dryingis similar to microwaves, where the beam penetrates the material, exciting it and generating heat within it. The air inside the IR ovens remains at room temperature, so there is a temperature gradient between the irradiated material and the environment. That gradient drives the water to come out faster than in conventional drying ovens, in which the material core has to reach a certain temperature to start the water evaporation. In addition, it is been pointed out that IR technology could be more efficient in the crystallization of PET, a required condition to avoid the subsequent absorption of water prior to processing. However, the secondary effects that this technology could generate in the irradiated material should also be considered. To the authors knowledge, there are not yet studies which imply a complete characterization of PET dried by IR radiation, including complex tests that are more representative of real products situation and sensitive to possible processing side effects. Then, the aim of this work is to evaluate PET under infrared radiation influence – which should reduce associated time, energy and cost – on material’s performance by studying the morphological, mechanical and fracture properties of virgin and recycled PET.