Polyurethane (PUR) rigid foams derived from petrochemical raw materials are some of the most effective high-performance insulation materials, highly efficient energy-saving, with a minimum space occupation. The versatility of PUR foams makes them suitable for a wide range of applications in insulations for civil and industrial constructions, from building envelope to insulations for industrial pipes or utility routes. PUR foams show a combination of physical and mechanical properties that recommend them for these applications: exceptionally low values of thermal conductivity, extreme temperature ranges thermal stability, fire resistance, excellent chemical and biological resistance, strength, lightness, high adhesivity, good processability and, last but not least, sustainability. Studies have shown that, in use, insulating PUR foams result in saving an amount of energy many times greater than that consumed to produce them.
Rigid PUR foams derived from petrochemical raw materials are not widely applied in construction due to the higher price than that of expanded polystyrene or mineral wool. However, up to 1.5 million tons of PUR rigid foams are annually used in thermal insulation for homes, shops, commercial offices, factories, warehouses, food processing plants, public institutions like schools and hospitals. If the price of PUR rigid foams would be reduced, they could become an exceptional solution to replace materials commonly used for insulation. Lowering the price of rigid PUR foams is possible using as raw materials aromatic oligoester polyols derived from poly(ethylene terephthalate) (PET) waste, which can induce to polyurethane foams the same outstanding properties as commercial aromatic polyester-polyols based on phthalic acids do. If the chemical process can be altered to occur in mild conditions, chemical recycling of PET may become a very convenient method to obtain PUR foams. Furthermore, using as depolymerization or modification agents other reagents derived from biomass, the chemical structure of the products can be tailored to aquire additional suitable properties.
Polyethylene terephthalate (PET) is a versatile polyester, extensively used for packaging beverages, food items and other consumer products (NAPCOR - National Association for PET Container Resources (www.napcor.com). PET is not biodegradable, and its accumulation into landfill causes serious damage to the natural environment. On the other hand, recycling of PET wastes results in the following advantages:
- Conservation of raw materials by reducing the need of virgin petrochemical feedstock;
- Energy saving, while less energy is required when converting recycled PET to new value added products, this resulting in less greenhouse gas emissions.
PET is the most widely recycled plastic in the world and it can be recycled several times to obtain large variety of products such as: fiber, fiberfill, carpet, strapping, food and non-food bottles, etc. However, PET can not be recycled by physical processes but for a limited number of times.
Chemical recycling is an appealing technique according to sustainable development principles, because it can lead to value-added products, while the quality of PET wastes is not as restrictive as for physical recycling. The chemical structure of PET backbone can be modified using a wide range of depolymerisation reagents and different proportions of these reagents, as well as a great number of possible subsequent chemical reactions, thereby providing targeted properties to the resulting oligoesters.
The classical metal-catalyzed chemical recycling of PET has some disadvantages, namely the negative effects on the environment of the heavy metal salts used as catalysts, as well as the harsh reaction conditions (elevated temperature and relatively long reaction time). Consequently, the organocatalytic glycolysis of PET has become an active research area lately. A key concept in organocatalysis involves the ability to strategically modify their structures into higher performing ones.
The last few decades have witnessed a spiralling growth of interest in using renewable resources, both in scientific and industrial field. Suitable biomass-based products, containing functionalities, were used as precursors for the production of chemicals, in order to avoid the use and preparation of co-reagents, as well as eliminate various process steps. Using of carbohydrate or vegetable oil based polyols in polyurethane formulations is one of the current environmental trends.
The project's goal is to provide a sustainable technology, with low energy consumption, for obtaining PUR rigid foams with significantly reduced price, which will represent an exceptional solution to replace materials commonly used for insulation in buildings with new materials, exhibiting outstanding properties and available for various applications, from building envelope to insulations for utility routs.
The project aims to develop a sustainable process of obtaining rigid PUR foams, cellular materials with excellent thermal insulating and fire resistance properties. The process consists of chemically recycling poly(ethylene terephthalate) (PET) wastes, using as depolymerization and/or modification agents renewable materials. Novel modified organocatalytic systems, different from conventional metallic compounds, will be developed and optimised in order to increase process performance, maximize energy efficiency and eliminate the need for solvents.
The products we plan to achieve along this project have to meet the requirements of their applications, therefore they have to acquire an appropriate chemical structure, considering also the particular project goal, namely to include structural moieties derived from PET and renewable materials. In this respect, the key of the project stands in organocatalysts modification, in order to induce selective solvolysis/ chemical modification of PET in mild conditions. Depending on the properties of the resulted oligoester-poliols, adequate formulations for the preparation of PUR foams will have to be found.
- Elaboration of experimental models concerning: organocatalysts with modified chemical structure in view of obtaining selective activity for cleavage of PET ester linkages in presence of specific renewable materials, in mild reaction conditions; oligoester polyols synthesis, using modified organocatalysts; various polyurethane materials formulations using oligoester-polyols derived from PET wastes and renewable resources; complex characterization of oligoester polyol products and polyurethane materials:
- Drafting lab-scale technologies for synthesis of modified organocatalysts;
- Drafting lab-scale technologies for synthesis of tailored oligoester-polyols from PET wastes and renewable materials;
- Drafting lab-scale technology for rigid polyurethane foams formation
- Up-scale in pilot plant of lab-scale technologies for oligoester-polyols synthesis and lab-scale technology for spray PUR foams preparation using previously selected versions of oligoester-polyols; creation of a library of new organic catalysts with modified chemical structures;
- Identification and assignment of intellectual propriety and dissemination of scientific results
Scientiffic challenges of the project refer to
- computational modelling novel catalitic systems and establishing the synthesis techniques to be used for their preparation;
- establishing correlations between reaction parameters, chemical structures and target properties of the final products (tailoring the chemical structure) and developing synthesis technologies using the novel organic catalysts.
- One of the major barriers that impede implementing PET chemical recycling lies in the high costs of the process catalyzed by metallic catalysts, arising from the severe reaction conditions and the significant consumption of energy; this project focuses on drastically reducing energy consumption, by achieving mild conditions required for the chemical reactions to occur, while maintaining a high yield;
- The chemical recycling of PET will lead to novel innovative products, also including in their structures renewable materials, suitable for polyurethane foam formulations
- Novel polyurethane foams, with remarkable thermo insulating, fire resistance and physico-mechanical properties, suitable for a wide range of applications in insulations for constructions, will be finally produced.