The courier bag is one of the bag types that entered everyday life with the spread of e-commerce. Clothing, textiles, books and small unbreakable products are often shipped in these bags instead of cardboard boxes. The adhesive-strip flap at the mouth of the bag closes the shipment in a single movement.
Packaging bag describes a broader group: plain or printed bags that protect the product from dust, moisture and dirt in the warehouse, on the shelf or in transit. On this page we cover the two groups together because of their shared expectations.
What is expected of a courier bag
A courier bag has to hold up throughout the whole journey of the shipment, from leaving the warehouse to reaching the recipient. It is dragged along conveyors, crushed under other parcels and may be left in the rain. So the properties expected of the bag are quite different from those of a shop bag.
- Opacity: The contents should not be visible from outside; this is for both privacy and security.
- Puncture and tear resistance: The film should withstand abrasion and impacts.
- Secure closure: The adhesive strip should leave a mark when opened, so it can be seen whether the bag has been opened.
- Writable surface: Labels should stick, and it should be possible to write on it if needed.
What raw material is it made from?
Courier bags are mostly made from LDPE and LLDPE blends. The puncture resistance and elongation of LLDPE are important against the stresses the bag meets in transit. LDPE makes the film easier to process and to seal.
White, grey or black masterbatch is used for opacity. A common solution in courier bags is a multi-layer film: the outer layer is white or coloured and the inner layer black. This gives a clean look from outside while hiding the contents completely.
Recycled polyethylene can be used, particularly in the inner layer or in packaging bags where appearance is secondary. A multi-layer structure allows the recycled raw material to be placed in a layer that is not visible from outside. The ratio to be used should be set with the film’s strength and the product’s expectations in mind.
The courier bag is the first point of contact between the product and the recipient; it bears every mark of the journey but does not reveal what is inside.
Production steps
Courier bag film can be produced by co-extrusion, that is on blown film lines where more than one layer is produced at the same time. Each layer is fed from a separate extruder, and the layers merge in the annular die to form a single film.
Bags that will carry a brand name, logo or shipping information go through the printing stage. Before printing, the film surface is prepared with corona treatment. E-commerce companies that see the courier bag as part of their brand use printed courier bags.
At the converting stage, the film is folded, the side seams are sealed and an adhesive strip is applied to the mouth. A release liner on the strip protects the adhesive until the bag is used. Some bags also have a second strip for returns. Quality control checks the tack of the strip, the seal seams, opacity and print quality.
Packaging bags: from warehouse to shelf
Besides the courier bag, there is a broad family of packaging bags used to protect products. Transparent bags that keep textile products free of dust, plain bags that separate spare parts, and cover bags that wrap furniture and large products all belong to this group. What comes first with these bags is that the product stays clean in the warehouse and on the shelf.
Packaging bags are mostly transparent and unprinted; the product needs to be visible and its barcode readable. Some have small holes for ventilation, others have a perforation for easy opening. As also noted on Hayashi’s production page, flat bags, block-bottom bags and pallet covers are different forms that come out of the same film production chain.
With these bags, the choice depends more on the product’s size and storage conditions than it does with a courier bag. For products that will wait in the warehouse for a long time, you can also ask how the film behaves under sunlight and temperature changes.
As with courier bags, a size standard is useful for packaging bags too. Using many different sizes in the same warehouse both complicates stock tracking and leads to the wrong bag being chosen. Setting a few sizes per product group is a simple way to streamline the packing line.
Choosing the right bag
When choosing a courier bag, the dimensions of the products being shipped should be taken first. Setting a few standard sizes for different products both makes order in the warehouse easier and reduces the use of bags larger than needed. The bag must be able to take the product comfortably once the flap is folded.
- Does the product have hard corners or is it soft? Products with hard corners need higher puncture resistance.
- Is a return strip needed?
- Will the bag be printed, or will a label be stuck on?
- Could the shipment be left waiting outdoors?
If a claim is to be made about recycled content or environmental properties, the claim must be verifiable and made in line with the relevant legislation. The statements to appear on the bag should be assessed together with the producer.