LDPE Poly-mailers

What is it?

LDPE poly-mailers are the ubiquitous waterproof shipping envelopes powering online retail. Made from co-extruded low-density polyethylene (LDPE), they feature multiple plastic layers fused together during manufacturing to maximize tear resistance and strength.

Due to the absence of plastic recycling codes on poly-mailers, they rarely make it into circular systems in Singapore. Thermal paper labels, permanent rubber adhesives, and thin-film dynamics mean millions end up straight in the incinerator after a single journey.

What does it feel like?

In its original post-consumer state, a poly-mailer is ultra-lightweight, soft, and slick, with a smooth, reflective interior. It stretches significantly before tearing and lacks crisp crease memory. Once fused with heat, it transforms into a dense, semi-rigid, synthetic sheet with a smooth, matte finish that resembles flexible sheet leather.

Why can't it just be recycled?

While LDPE itself is technically recyclable, standard waste management systems struggle to process these types of mailers:

Why they fall through the cracks:

Machinery Clogging: Soft, thin plastic films wrap around rotating sorting drums in recycling facilities, bringing operations to a halt.
Contamination & Label Glue: Thermal paper shipping labels and aggressive flap glues are extremely difficult to separate without heavy chemical washing.
Microplastic Downcycling: "Biodegradable" variants of poly-mailers contain additives that break down into microplastics faster, which contaminates standard PE recycling batches if mixed together.

So what happens to them? Once containing our long-awaited parcels, they are discarded without a second thought, headed straight for the incineration plant. A highly engineered material that took energy and resources to produce gets burned after a single use.

That's the gap The Interchange is working in.

What we've learned working with it

We began experimenting with post-consumer delivery mailers in 2026 to explore heat-fusion and structural crafting techniques. Here is what our studio trials revealed:

Safety & PPE with LDPE Polymailers

Ventilation & Fume Extraction:

Heating LDPE past its melting threshold (~135°C) or holding it at high temperatures risks thermal oxidation, releasing respiratory irritants and volatile organic compounds (VOCs). Always operate in a well-ventilated space equipped with active fume extraction or open cross-airflow.

Respiratory Protection:

Wear a fitted half-mask respirator equipped with Organic Vapor and Particulate cartridges (e.g., OV/P100) during extended fusing sessions or when working with unknown plastic blends.

Preparing the Material

Manual Label Removal (Recommended):

Cut away any contaminants (e.g., stickers, labels, seals with adhesives).

Chemical Label Removal:

Spray an adhesive remover (e.g., 3M or Daiso Seal Peeling Spray) generously over thermal shipping labels. Once saturated, peel slowly at a low angle.

Surface Cleaning:

Wash with mild soap to remove grime, ensuring all outer surfaces are completely free of sticky residue to prevent damage to heat press equipment.

Fusing Layers

Thermal Window:

Poly-mailers fuse between 120°C to 135°C under a heat press, depending on the thickness of the material. Always allow the poly-mailers to cool completely before handling.

Protective Barriers:

Always sandwich the plastic between Teflon/Baking sheets to prevent sticking and avoid unintended surface impressions.

Layer Rigidity:

Experiment with layers to achieve your desired thickness/structure.

4. Sewing and Construction

Technical Framework

The Right Needle

Employ a sharp, heavy-duty needle.

Longer Stitches

Calibrate your equipment for a longer stitch length. If your stitches are mapped too close together, they form a perforated line that causes the material to sheer and rip under tension.

No Pins

Punctures in this matrix are permanent. Utilize standard sewing clips or double-sided tape to hold your patterns together instead.

Sharp Cutting tools

Blunt cutting tools will cause the plastic to stretch and shred. Always work with sharp tools to minimize the risk of the poly-mailers stretching.

What we've made from it

Our baseline application from this waste stream focuses on everyday utility. Here is what we have prototyped and constructed so far:

Cardholders made out of poly-mailers with snap buttons — **// Product 01:** Minimalist Cardholders — Slim Snap-closure with a leather-like finish.

Two-Way lanyard wallets made out of poly-mailers — **// Product 02:** Two-Way Lanyard Wallet — card and id holder that wears in either portrait or landscape.

Sling Bag made with poly-mailers and discarded lanyard — **// Product 03:** Poly-mailer Sling Bag — simple, waterproof daily crossbody sling bag made from fused panels.

Poly-mailer pen holder with elastic strap — **// Product 04:** Elastic Pen Holder — stylish pen sleeve with an elastic band to strap onto notebooks and tablets.

Poly-mailer passport cover — **// Product 05:** Poly-mailer Passport Cover — slim waterproof sleeve that keeps your passport and cards safe.

What's still being figured out

Hole Punch Deformation: Standard mechanical punch tools pull and stretch the elastic LDPE film instead of slicing cleanly.
Thermal Shrinkage: Fusing larger panels causes uneven warping and dimensional shrinkage as the plastic cools.
Hardware Tension: Heavy-duty snap closures pull out from thin layers over time; double-layered structural reinforcement patches are currently being tested for long-term durability.

Donate your poly-mailers

We accept post-consumer LDPE poly-mailers from households, offices, and e-commerce sellers. Drop us a message at makeit@theinterchange.cc to arrange collection or drop-off at our studio in Bukit Merah.

Contact: makeit@theinterchange.cc