Relationships between processing‐structure‐migration properties for recycled polypropylene in food packaging∗

Abstract

In this work the relationships between processing, structure and migration properties of recycled polypropylene (PP) were analysed in relation to the possible use of recycled PP in food packaging applications. PP containers used in food packaging were contaminated with food and then washed, reduced into a processable size, dried and reprocessed by injection moulding. Gel Permeation Chromatography (GPC) analysis, mechanical, and total migration tests were performed on injection moulded samples to verify the effect of the recycling process on the structure and properties of PP. In order to evaluate the effect of the molecular weight on the properties of the recycled polymer, the study was conducted on containers produced by injection moulding made from a low molecular weight (LMW) PP and on containers produced by thermoforming made from a high molecular weight (HMW) PP.

Influence of recycling and contamination on structure and transport properties of polypropylene

“…These results also reveal that in the contaminated PP the degradation phenomena are mainly in regard to the polymer chains with high molecular weight. Similar results were reported in our previous works conducted on the primary and secondary recycling of PP 14, 15. Moreover, the MWDs ( M z / M w and M w / M n ) calculated for the contaminated samples that are recycled twice (R2 c ) are narrowed more than 20% with respect to the virgin contaminated ( V c ) PP.…”

“…A number of studies report on the processability and performance of recycled polymers,7–13 but few works are focused on the barrier properties of articles manufactured from postconsumer plastics. In our previous studies14–16 we separately analyzed the influence of reprocessing (primary recycling) and food contamination (postconsumer recycling) on the structural, mechanical, and barrier properties and migrational behavior of polypropylene (PP). The results obtained from performing primary and secondary recycling experiments have shown that the structure, which is the number‐average molecular weight ( M n ), weight‐average molecular weight ( M w ), and molecular weight distribution (MWD) of the starting polymer is of primary importance to obtain first quality goods that are suitable for food packaging applications.…”

On the use of tris(nonylphenyl) phosphite as a chain extender in melt‐blended poly(hydroxybutyrate‐co‐hydroxyvalerate)/clay nanocomposites: Morphology, thermal stability, and mechanical properties

“…This issue is of special relevance since during food packaging operations, there are many thermic cycles (film processing, stretching, thermoforming, hot sealing, etc.) where some local thermal degradation can occur, being the products of such degradation susceptible to migrate toward the content of the package . This trend is in concordance with the literature where the TNPP has been used as chain extender in other matrices …”

Thermal, mechanical and permeation properties of gamma-irradiated multilayer food packaging films containing a buried layer of recycled low-density polyethylene

“…In general, melt processing, usually employed as a step of plastics recycling process, may introduce oxidative as well as thermomechanical degradation of (Incarnato et al, 1998;Tzankova Dintcheva et al, 1997). The result of this is a significant modification in the molecular structure of the polymer and a subsequent deterioration of mechanical, thermal and optical properties, gas transmission rates as well as increase in migration values of the polymer (Devlieghere et al, 1998;Tzankova Dintcheva et al, 1997;Incarnato et al, 1998;Pospisil et al, 1995;Suarez and Mano, 2001). By introducing additives such as antioxidants, stabilizers and impact modifiers the properties of recycled polymers can be improved (Tzankova Dintcheva et al, 1997).…”

“…Considerable work has been published in the literature on the effect of ionizing radiation on (a) thermal, mechanical and gas permeation properties and (b) structural changes of polymers as a result of ionizing radiation treatment (Zenkiewicz, 2004;Fengmei et al, 2000;Woo and Sandford, 2002;Yagoubi et al, 1999;Buchalla et al, 1993;Klemchuk, 1993;Goulas et al, 2002Goulas et al, , 2003Goulas et al, , 2004 as well as on the above reported properties of non-irradiated recycled polymers (Devlieghere et al, 1998;Incarnato et al, 1998;Tzankova Dintcheva et al, 1997) and irradiated recycled polymers (Burillo et al, 2002a, b;Suarez and Mano, 2001) There are, however, no data on the effect of ionizing radiation on the above reported properties of multilayer packaging structures containing a middle buried layer of recycled polymer.…”