Mono Material Lid Film Selection for Ready Meals

Abstract

Driven by sustainability goals and regulatory pressure, the packaging industry is transitioning from complex multilayer structures toward mono material solutions that are more easily recyclable. This shift presents challenges, especially in high-performance applications such as microwaveable ready meals, where packaging must endure sealing, cooking, and reheating processes without compromising safety or functionality.

This thesis focuses on selecting a suitable mono material polypropylene (PP) lidding film for the Micvac FlexProcess™. A packaging system where food is sealed into a tray, cooked in-pack using microwave energy, and later reheated by the consumer. The lid film plays a critical role by forming a heat-sealable barrier that must expand under steam pressure (ballooning), maintain a vacuum after cooling, and allow safe, user-friendly opening. Its interaction with the tray and valve system is essential for pressure regulation and product integrity throughout the process.

To guide evaluation, two design criteria were established: fulfilling product needs such as safety and usability, and meeting process requirements like thermal stability and controlled expansion. These were translated into four critical parameters: sealing performance, pressure resistance, mechanical properties, and peel ability.

Five candidate films from three suppliers were assessed through lab and pilot-scale testing. Performance differences were largely influenced by seal layer design and peel mechanisms. A selection matrix based on the Ulrich and Eppinger method enabled structured comparison, identifying M22 as the most promising film, despite some reheating-related limitations.

The study concludes with recommendations for further testing using real food products and advanced material characterization to ensure robust performance across the full product lifecycle.

Popular Abstract

From Plastic Waste to Recyclable Solution: Toward Sustainable Ready Meals

Ready meals are a convenient part of modern life: just microwave, open, and enjoy. But what happens to the packaging afterward? While the food disappears in minutes, the packaging often sticks around much longer.

Most ready meals are sealed with multilayer plastic films. Each layer has a job: one blocks air and moisture, another makes the lid stick to the tray, and a third helps it open easily. But because these layers are made from different materials, they’re nearly impossible to recycle, the packaging often ends up as waste, and at best, it’s burned for energy.

To promote a more circular approach, packaging should be made from just one material, something that can be easily sorted, recycled, and reused to make new packaging similar to the one it was used for. This not only reduces waste but also helps avoid the need for new raw materials, lowering the environmental impact.
This thesis explores a way forward: could we switch to a single material film that’s still safe, functional, and recyclable? Working with the Swedish company Micvac, I focused on their FlexProcess™, a unique system where food is sealed into trays, cooked inside the package, and then vacuum-sealed for freshness, all without preservatives. Their packaging system (tray and valve) is already made almost entirely from recyclable polypropylene. The only part left is the lid film, which has a lot to handle: it must survive the heat of cooking, stretch without bursting, and still peel open easily for the consumer.

To determine which of the five polypropylene (PP) film candidates was up to the task, I put each one through a series of tests. These included microwave simulations, lab experiments, and even a taste panel with mashed potatoes to assess everything from sealing strength to how consumer-friendly the packaging feels. One film, M22, came close to meeting all the key requirements. While not perfect, especially during reheating, it shows strong potential. More importantly, this project provides clear selection criteria and highlights critical parameters, offering other companies a practical method to test and improve monomaterial packaging.

In the end, it’s about taking small steps that create a big impact: designing packaging that balances sustainability and convenience without compromising what makes ready meals so enjoyable.

• author: Henao Tobon, Ana Maria
• supervisor: Lars Palm; Uli Nicol Hosse Pastor
• organization: Packaging Logistics
• alternative title: Polypropylene (PP) Lid Film Selection for Micvac FlexProcess™ Package
• course: MTTM01 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Mono material Lid Film, Polypropylene, Microwave Packaging, Critical Parameters, Material Selection Matrix
• language: English
• id: 9202284
• date added to LUP: 2025-06-18 14:50:37
• date last changed: 2025-06-18 14:50:37