A follow-up report on the web seminar with Dr. Heiko Schenck
On 10 March 2026, participants joined the Innoform web seminar “Sealing Layers and Sealing Properties PE & PP – Basics for Flexible Packaging Films to gain a comprehensive overview of sealing technologies for flexible packaging. Heiko Schenck, an experienced polymer chemist with more than 30 years in the industry, guided attendees through the complex world of polyethylene (PE) and polypropylene (PP) sealing layers and their role in modern packaging applications.
Introduction to Sealing Materials in Flexible Packaging
In his opening, Heiko presented a clear overview of where sealing layers are used today: frozen food packaging, heavy‑duty shipping sacks, confectionery, snacks, lidding films, rigid packaging, and multilayer laminates. These examples illustrated the central role of polymer selection along the entire value chain—from resin producer to film manufacturer, brand owner, and retailer.
He emphasised that no single material fits all applications. Understanding performance boundaries, environmental requirements, and processing constraints is essential before selecting materials or film structures.
Deep Dive: Polyethylene (PE) as a Sealing Layer
A major part of the web seminar was dedicated to the variety of polyethylene grades and how their structure and morphology affect sealing behaviour.
1. Traditional PE Types
- LDPE – highly branched, low‑density, easy processing, low melting point, historically the first standard sealant.
- HDPE – highly crystalline, excellent water‑vapour barrier, but unsuitable as a sealant due to stiffness and high melting point.
2. Linear Polyethylenes
- LLDPE (Butene/Hexene/Octene) – improved mechanical strength and seal strength; properties depend heavily on comonomer type and content.
- VLDPE / ULDPE / Plastomers – ultra‑low densities, very soft and elastic, excellent for low‑temperature sealing and flexible applications.
3. Metallocene‑PE (mPE)
Schenck highlighted the transformative impact of metallocene catalyst technology:
- Very narrow molecular weight distribution
- Superior optical clarity
- Outstanding seal initiation temperatures (SIT)
- High seal strength and hot‑tack
- Lower migration due to cleaner catalyst residues
These properties make mPE grades the state‑of‑the‑art solution for performance‑critical applications.
Key Factors Influencing Seal Performance
Heiko explained the four cornerstones of high‑quality sealing:
1. Seal Initiation Temperature (SIT)
Lower SIT allows faster packaging speeds and reduced thermal load on sensitive products. Modern mPE (especially Octene‑based grades) offers the lowest SIT values today.
2. Seal Strength
Crucial for packages with heavy or bulky contents such as cereals or pet food.
3. Hot‑Tack
The immediate strength of a seal right after closing—essential for vertical form‑fill‑seal operations. mPE provides the strongest performance in this category.
4. Seal‑Through Contamination
A real‑world challenge, particularly in dusty or fatty environments:
– Ionomers show excellent resistance to fat contamination
– mPE performs best in powder contamination scenarios
He later emphasised in the Q&A that the only reliable test method remains real‑package overpressure testing—there is no alternative laboratory shortcut.
Peelable Systems: Three Mechanisms
The web seminar outlined the main peel concepts used today:
- Sub‑burst Peel – destruction within the sealant layer
- Cohesive Peel – two‑phase system, often PE with polybutene; peel force depends on blend ratio and layer thickness
- Adhesive Peel – delamination between coating and substrate, common for lidding films (cups, trays, bottles)
Achieving reproducible peel behaviour requires precise formulation and process control, especially for multilayer films.
Polypropylene (PP) as a Sealing Layer – More Versatile Than Ever
Polypropylene, historically limited by higher SIT and lower seal strength, has undergone significant innovation:
- PP offers excellent thermal stability, making it ideal for retort, microwave, and hot‑fill applications.
- New terpolymer and copolymer technologies allow significantly lower SIT.
- Blends with PE‑plastomers further boost seal performance.
→ These advances now allow fully recyclable PP monomaterial structures with reliable sealing.
Sustainability: Pathways to Monomaterial Structures
Schenck addressed current developments toward PE‑ or PP‑based monomaterial packaging:
- MDO‑PE is emerging as an alternative to PET, though challenges remain (stiffness, seal temperature, process stability).
- PP monomaterial concepts are increasingly used in meat, dairy, and ready‑meal applications thanks to improved barrier and sealing options.
He emphasised that although technically feasible, monomaterial solutions often require complete redesigns of existing laminates—and may involve trade‑offs in machinability or cost.
Conclusion
The web seminar delivered a rich and insightful overview of sealing layer technologies for flexible packaging. Participants gained:
- A clear understanding of the differences and synergies between PE and PP
- Up‑to‑date knowledge on modern resin innovations
- Practical insights into sealing behaviour, peel systems, and contamination challenges
- A sober assessment of the opportunities and limits of monomaterial sustainability solutions
With its blend of technical depth and market relevance, this web seminar provided valuable knowledge for anyone working with packaging films, sealing processes, or material development.
With this web seminar, we are further strengthening our claim to be the leading knowledge partner in the field of flexible packaging – both through our Testing Service in Oldenburg and through Innoform Coaching.