Contamination of polyvinyl chloride cling films from cardboard packaging

An analytical screening was undertaken with the aim of investigating the occurrence of di-isobutylphthalate (DIBP) in polyvinyl chloride (PVC) cling films for food contact applications and its source of contamination throughout a converting process. Although raw plastic materials used by producers are free from phthalates and analytical evidences confirm their absence after the extrusion process, DIBP can be found in final rolls packaged into cardboard packaging during storage. A solvent extraction Gas Chromatography/Mass Spectrometry (GC/MS) analysis was applied on several intermediate products and at different stages taken from the converting process, with the aim of identifying the source of contamination. Different cardboard cores and folding cardboards made of recycled fibres were analyzed, and some of them resulted highly contaminated by DIBP. The storage of final cling films with these materials increased DIBP transfer into PVC. To investigate the possible DIBP transfer mechanism from contaminated paper and adsorption by plastic materials through the gas phase, kinetic experiments were performed in a model system. Results obtained at 20 C, 30 C and 40 C showed a considerable uptake of DIBP into PVC; Weibull model parameters estimated from the experimental data suggested an initial rate of the process dependent on temperature. In addition, to evaluate the partitioning behaviour, adsorption isotherms of DIBP into paper, PVC and low low density polyethylene (LLDPE) cling film were obtained at 40 C.