BOPP Envelope Window Films: Specialty Films for Postal Converting
Envelope window converting demands a precise combination of properties :
- high rigidity for clean die-cutting,
- optical clarity for postal address readability,
- dimensional stability under hot-melt adhesive bonding,
- and low density for yield efficiency.
Conventional oriented polystyrene (OPS) films have historically met these requirements, but with limited recyclability, they are increasingly incompatible with mono-material PP envelope design and modern packaging waste regulation.
Bioxpack’s AW range is a family of specialty bioriented copolymer films engineered specifically for envelope window converting. At 0.91 g/cm³, AW films deliver a higher surface yield per kilogram than OPS while maintaining the rigidity, transparency and machinability that envelope converting lines require.
Available in standard, high-thickness, mono-material PP and biodegradable versions, from 24 to 48 microns, and produced under BRC Packaging Materials certification.
Why BOPP for Envelope Windows
The case for switching rests on three practical advantages.
Yield and cost efficiency
The lower density of BOPP versus OPS translates directly into more windows per roll and lower material cost per envelope — an advantage that compounds significantly at industrial converting volumes.
Recyclability and regulatory compliance
OPS-based window films are not compatible with PP recycling streams and create contamination in paper envelope recycling. BOPP-based AW films can be integrated into mono-material PP envelope structures compliant with CEFLEX design-for-recycling guidelines and EU PPWR requirements — turning a regulatory constraint into a product differentiator.
Machinability
AW films are engineered for high-speed envelope converting — die-cutting, hot-melt adhesive bonding and automated insertion — with the dimensional stability, thermal resistance and COF profile these processes require.
AW Range: Specialty Envelope Window Films
AW12R: Standard & High Thickness
AW12R is the core grade of the AW range — a high-rigidity bioriented copolymer film designed for envelope window converting and for lamination with PP cast films. Both sides are treated for printability and lamination compatibility. The standard series covers 24 to 32 microns for conventional envelope formats.
The high-thickness series covers 35 to 48 microns for heavier envelope stock or applications requiring greater window rigidity. Across both series, the film delivers consistent gloss, controlled haze suited to postal address readability, high COF for envelope converting equipment compatibility, low shrinkage for dimensional stability under thermal processing, and very low density.
Not heat-sealable. Printable, laminatable, metallizable.
Recyclable, bisphenol-free, free from heavy metals.
AW Range: Specialty Envelope Window Films
AWRB: Biodegradable Envelope Window Film
Our biodegradable specialty copolymer film for envelope window converting, combines the rigidity and machinability of the AW12R with certified biodegradability. Available from 25 to 48 microns, it delivers consistent gloss and haze performance across the range, with the dimensional stability and thermal resistance required for hot-melt adhesive bonding on envelope converting lines.
Not heat-sealable. Printable. Recyclable and biodegradable. Free from bisphenol A, phthalates and heavy metals. Low density.
Our Recyclable AW grade addresses the growing demand from postal operators and envelope manufacturers for window films that go beyond standard recyclability claims — particularly relevant in markets where biodegradability certification is a purchasing criterion.
Key Properties Across the AW Range
All AW grades share the defining characteristics of specialty envelope window films.
- High rigidity relative to thickness enables clean, precise die-cutting at converting speeds.
- Controlled haze — consistent across the range — delivers the translucent clarity that makes envelope windows readable for automated postal sorting without the glare issues associated with fully transparent films.
- Low shrinkage at processing temperatures ensures dimensional stability during hot-melt adhesive bonding and in postal handling environments.
- High COF on both sides is calibrated for envelope converting and insertion equipment where controlled friction prevents misfeeding.
None of the AW grades are heat-sealable — window bonding is achieved via hot-melt adhesive in the converting process, consistent with standard envelope manufacturing practice.
Full technical specifications are available in the individual data sheets for each grade.
Applications & Converting Compatibility
The AW range serves envelope manufacturers and converters producing commercial, mailing and catalogue envelopes across European postal markets. AW films are compatible with standard envelope converting lines using die-cutting and hot-melt adhesive window bonding.
The AW12R-T1 grade extends the range into flexible packaging — mono-material PP pouches and sachets where the rigidity and optical properties of the AW copolymer formulation offer an alternative to standard BOPP outer webs.
The AWRB biodegradable grade is suited to markets with specific biodegradability procurement requirements or to brands seeking a differentiated environmental claim on their mailing packaging.For producers transitioning from OPS or PS window films, Bioxpack’s technical team provides grade selection guidance, sample rolls for machine trials and full qualification support.
Request Samples or Technical Data Sheets
Contact our technical team to request AW film samples, technical data sheets, or grade selection support for your envelope converting process and format requirements.
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