Project R-9252

Optimal peelable seals in packaging concepts undergoing thermal processing (Research)

During the last decennium, the consumer demand for convenient food packaging has steadily increased. Having an easy-to-open seal is a crucial aspect, both for convenience as for the quality assurance of the food product. This demand has motivated material researchers to develop new sealants that are now on the market. However, to the best of our knowledge, research into the post-seal quality during and after (thermal) treatments has not been investigated thoroughly. Therefore, the aim of the CORNET project is to investigate the effect of thermal processing on the quality (e.g. seal strength, tightness) of the easy-peel seals before, during and after such treatments. What are the practical questions we want to answer? 1)Which packaging material should I choose when I have a target consumer peel force in mind, and have a well-defined thermal treatment step to assure product safety? 2) What is the effect of the parameters of my sealing machine (time, pressure, temperature) on the seal quality before, during and after thermal treatment? 3) When applying thermal treatment, what is the maximal temperature gradient I can induce that still guarantee a good quality seal? 4) How do package shape and seal contour influence the seal integrity during thermal treatment? How will we do this? 1) We will select the most relevant film/tray material, and will characterize them using reference methods (DSC, viscosity, physical parameters). 2) We will investigate the relation between (film x seal parameters x thermal treatment parameters) and the seal quality. This will be based on samples rather than on packages to standardize our measurements and findings. 3) We will then run experiments on the packaging level, where we focus on trays and pouches. 4) We will use these results to develop an optimization model with a limited number of tests to predict the peel behavior. Expected results and practical recommendations for industry? 1) We will apply the results on films or packages of our user commission. This way, there is a direct benefit for their own business. 2) A best practice guide will tell a producer which packaging material to use, how to seal it, and will define limits on thermal gradients the package will be able to resist. 3) An easy-to-use module will be developed and will be accessible to user committee members to optimize their own process. Update results (february '21): Cool processing with peelable polyethyelene (=PE) seal layer: Seal strength increased during cool processing with peelable topfilms, sealed against bottomwebs. There was no influence of processing temperature on seal strength after processing, when the sealed sample is in standard condition (23 °C, 50 % RH). With peelable pouches, sealed to itself (two peelable surfaces), there was no influence of processing temperature during and after processing. Hot processing with peelable polypropylene (=PP) seal layer: 95 and 121 °C are considered as processing temperatures and compared with 23 °C. Seal strength decreased during hot processing with peelable pouches and topfilm-bottomweb concepts. The strongest decrease is observed at 121 °C. The decrease is material dependent. In some cases a decrease in seal strength is observed after thermal processing as well. The decrease in strength during heat processing should be taken into account when choosing peelable packages undergoing thermal processing. Case studies: Tropical conditions (38, 50 and 60 °C) had no impact on the peel performance of coated paper during and after thermal processing. A decrease in seal strength is observed with coated paper, during processing at 95 °C.

01 January 2019 - 31 December 2020