RICERCA ITALIANA     

Polyesters functional properties optimization for packaging applications by morphology control, nanofillers and nanoreinforced coatings

Università degli Studi di Palermo

Abstract

The improvement of transport properties of polymers used in food packaging applications based on polyethylene terephthalate (PET) will be undertaken following different strategies such as:
· copolymerization with a rigid-chain polyester,
· blending with an Organoclay type commercial nanofiller, or
· blending with a new generation nanofiller like POSS (Polyhedral Oligomeric Silsesquioxane), with promising development perspective due to their plausible low production cost or finally
· with coatings with polyurethane adhesives in their turn reinforced by nanofillers.
These objectives will be carried out through the control of the primary structure in the copolymers and by the compatibilization of the nanoreinforcements using both 2D types (organoclays) and 3D types (POSS). New melt blending methods that will allow to incorporate greater quantitites of nanofillers will be investigated. The interactions with the rheological characterizations, used as an instrument for analyzing the structure formed, will permit to optimize the operating conditions. A complete macro- and microscopic characterization of the structure will allow to analyze the best processing conditions to be used for obtaining a satisfactory exploitation of the nanofillers.
The use of a solidification technique simulating the conditions encountered in polymer processing will allow to highlight the interactions between the morphology developed and the cooling conditions as >>>

Principal Investigator

Stefano PICCAROLO Università degli Studi di PALERMO

Research Objectives

The main goal of the project is to improve the barrier properties of materials used in food packaging applications. This project is centred on polyethylene terephthalate, a polymer that is widely used and well established in the sector which also enjoys well developed processing technologies.
The same sectors that already use PET will benefit from the strategies followed in this project. They will be able to broaden the horizons of the utilization of this polymer by a better control of the primary structure considering the possibility of using nanofillers and analyzing the optimum conditions of the transformation process.
An important parameter, especially for films used in food packaging, is low permeability to oxygen since this is the condition that determines the capacity of the film to preserve the aliment unaltered although in recent years, the demand also includes heat resistant packaging materials that can be directly used in ovens or boiled in water.
The reduction of the permeability to gases and vapour implies the possibility of using lower material thickness, guaranteeing a sufficient level of barrier or the possibility of using the same thickness however considerably increasing the shelf-life of the packed food product. Besides, if one considers the fact that the use of nanofillers does not alter the transparency of the polymeric matrix and also the real possibility that it offers in improving the mechanical properties, this means >>>

First Results

In particular, making reference to the scheme in Fig. 1 and to the synoptic and temporary picture of the undertaken tasks (Gantt's diagram) in Fig. 2, the actions (with the list of expected results following each task) will be:

A.a PET+ PEN copolymers
This activity will focus both on the synthesis of innovative PET-PEN copolymers and on the preparation of systems of PET-POSS, PEN-POSS and on the functionalizing of POSS using polyols. The synthesis of PET/PEN copolymers, in particular, includes block as well as random copolymers. As regards the second case, techniques of polycondensation will be used modifying both the composition and the degree of randomization.
The block copolymers instead will be synthesized starting from commercial polymers. The synthesis will be carried out in two successive stages. In the first stage the functionalization of the base polymers with reactive end groups will be accomplished and in the second stage the functionalized polymers will be made to react in order to form the block copolymers. Different compositions, block lengths and end groups will be obtained.
· Synthesis of random PET-PEN copolymers with various percentage compositions and different degrees of randomness .
· Synthesis of block PET-PEN copolymers with various percentage compositions, block length and end groups.

A.b Melt Compounding: PET+ PEN/ compatibil PET +PEN
This activity includes the >>>

Timescale

24 months

National and international background

Polyethylenterephthalate (PET) is the material of choice to produce containers for mineral water and soft drinks. Recently it is being introduced for packaging of more sensitive products, e.g. fruit juices, beer , wine, dry food, sauce, milk. The most important factors affecting the shelf life of these products are the microbiological sensitivity, the action of light and the permeation of gases and aromas through the package layer. Another important aspect is the possibility for the material to withstand thermal and sterilizing treatments necessary to guarantee the requirements of cleanness and those imposed by container filling under aseptic conditions.
In fact the need for higher barrier in PET has been recognized for many years and numerous PET backbone modifications have been accomplished to enhance barrier characterized by high cost and investment required to built new monomer and polymer plants and to obtain food contact regulatory clearances for new polymers. Technological solutions with active and passive barrier are known through multilayer processing techniques, where high-barrier polymers are sandwiched between PET layers [1].
PET based nanocomposites able of displaying barrier improvement from dispersion of low to modest levels (generally <6-8%) of relatively inexpensive clay materials and of being processable with conventional stretch blow molding processing equipment. Another alternative is to develop nanocomposite coatings and adhesives which >>>