Mailing bags and OPP bags: Differences, applications and closures

Coex mailing bag vs. OPP bag: Two film concepts compared directly

In fashion, textile and mail-order retail, Coex mailing bags and OPP bags are frequently used side by side – often within the very same order as a combination of protective inner garment bag (OPP) and tough outer shipping mailer (Coex) [14], [15]. In terms of polymer science and function, however, the two films differ fundamentally [14], [16]:

Property	Coex mailing bag (poly mailer)	OPP bag (flat or adhesive-flap bag)
Raw material	Coextruded polyethylene (LDPE / LLDPE) [14]	Oriented polypropylene (OPP / BOPP) [15], [16]
Optics & transparency	Opaque, typically white/grey outside and black inside [9], [14]	Crystal clear (high transparency) with high surface gloss [15], [16]
Mechanics & feel	Soft, flexible, tough, puncture- and tear-resistant [8], [14]	Crisp, stiff, dimensionally stable, high tensile strength [15], [16]
Closure system	Permanent security adhesive strip (optionally with 2nd return strip) [14]	Resealable adhesive strip on flap or open flat bag [15]
Primary application	Outer postal and courier shipping bag in e-commerce [14], [17]	Retail presentation, textile inner bag, printed matter, food [15], [16]

Construction and advantages of Coex mailing bags in e-commerce

Coex mailing bags are manufactured by blown-film coextrusion, bonding at least two differently pigmented polyethylene layers together in the melt [9], [14]. This creates a thin yet fully opaque film: while the black interior prevents contents from showing through against the light, the white or grey exterior provides high contrast for thermal shipping labels and multi-colour brand printing [9], [14].

For non-fragile goods such as apparel, home textiles, boxed footwear, catalogues or spare parts in primary boxes, Coex mailing bags are a space- and weight-saving alternative to corrugated cardboard boxes [14], [17]. They require only a fraction of the warehouse pallet space of folding cartons, conform closely to product volume without shipping excess air, protect reliably against rain and splash water, and reduce transport weight [14], [17].

Security adhesive closure and return strip (double adhesive tape)

Because mailing bags face high mechanical stress on automated parcel sorting conveyors, they are equipped with a permanent self-adhesive closure (hot-melt security adhesive) [14]. Once the liner is removed and the flap pressed down, the adhesive bonds so firmly to the film that tamper-free opening without visible damage or distortion of the bag is impossible [14].

For online fashion and footwear retailers, mailing bags with a second adhesive strip (return strip) and an intermediate tear perforation are particularly practical: the recipient opens the parcel cleanly along the perforation line without cutting the bag body and can reseal the same bag immediately with the second adhesive strip if returning goods [14], [17].

Crystal-clear OPP bags for presentation, order picking and food contact

OPP (Oriented Polypropylene) and BOPP (Biaxially Oriented Polypropylene) are produced by stretching polypropylene film in the longitudinal or both longitudinal and transverse directions [16]. This orientation of the polymer chains gives the film its crystal-clear transparency, brilliant gloss, crisp stiffness and effective moisture vapour barrier [15], [16].

In retail and fulfilment, OPP bags are used in two main styles:

• OPP bags with adhesive flap: Equipped with a resealable adhesive strip on the flap or bag body – ideal for shirts, knitwear, greeting cards, brochures and small parts that must stay protected from dust in storage while remaining readable by barcode scanners through the film [15], [16]. Air-vent holes or Euro-slot hangers for retail displays can be added as required [15].
• OPP flat bags (without closure): For open wrapping, taping or heat-sealing, including bakery items, confectionery and dry food products in compliance with food-contact Regulation (EU) No 10/2011 [16].

Pakzeno supplies both opaque Coex mailing bags (with single closure or return strip, plain or multi-colour printed) and crystal-clear OPP flat and flap bags in standard sizes and custom dimensions.

View mailing bags and OPP bags from Pakzeno