Theoretical and experimental study of foaming process with chain extended recycled PET

Abstract

Abstract. The theoretical and experimental study of a thermoplastic polymer foaming process is presented. Industrial scraps of PET were used for the production of foamed sheets. The process was performed by making use of a chemical blowing agent (CBA) in the extrusion process. Due to the low intrinsic viscosity of the recycled PET, a chain extender was also used in order to increase the molecular weight of the polymer matrix. Pyromellitic dianhydride (PMDA) and Hydrocerol CT 534 were chosen as chain extender and CBA, respectively. The reactive extrusion and foaming were performed in a two step process. Rheological characterization was carried out on PET samples previously treated with PMDA, as well as the morphological study was performed to define the cellular structure of the foams produced. Moreover, in order to predict the morphology of the foam, a non isothermal model was developed by taking into account both mass transfer phenomenon and viscous forces effect. Model results were compared with experimental data obtained analyzing the foamed samples. The model was validated in relation to working conditions, chemical blowing agent percentage and initial rheological properties of recycled polymer. A pretty good agreement between experimental and calculated data was achieved.

Analysis of high melt‐strength poly(ethylene terephthalate) produced by reactive processing by shear and elongational rheology

“…The PMDA supplied by company abcr has a melting point at 286°C and a molar mass of 218 g mol −1 . The applied concentrations published vary between 0.08 and 1.00 wt% . In particular, different optimum PMDA concentrations were reported with respect to maximum viscosity or molar mass without the occurrence of gelation, depending on the grade and/or the processing conditions.…”

“…Since LCB polymers are known to possess higher melt strength compared to linear polymers , LCB‐PET can withstand higher stresses in the melt state. Consequently, stable production of thinner films is possible, and foams with well defined porosity can be produced .…”

The effect of technological parameters on the foaming of injection molded, recycled PET

“…This can be dramatically improved by adding chain extenders. These materials connect to the ends of several polymer chains, this way increasing their length and the number of branches, thus increasing intrinsic viscosity of the material, giving it better processability [8][9][10][11].…”

Cellulose Acetate for Thermoplastic Foam Extrusion

“…Blends of linear and branched polypropylene (PP), crosslinked polyethylene (PE) or blends of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) are good examples for improved melt strength, melt extensibility, and consequently good foaming behavior [4,[9][10][11][12][13]. Chain extension of recycled poly(ethylene terephthalate) (PET) significantly improves the rheological properties and foaming behavior [14]. Blends of polystyrene (PS) with different molecular weights lead to bimodal MWD.…”