Cleanroom Bag: LDPE and HDPE Component Packaging

A cleanroom bag has one job that is easy to state and hard to achieve: move a clean component from one controlled space to another without adding contamination. The bag itself is a contamination source unless it was made and packed under control, and the way it is sealed decides whether the contents stay clean in transit.

Wuxi Harmake Technology Co., Ltd. produces LDPE and HDPE bags for pharmaceutical and cleanroom use, including square-bottom bags, flat pockets, perforated and incised formats, double-line sealed pockets, coloured bags and roll film, manufactured and packed in a controlled environment.

Resin Choice: LDPE, HDPE and What They Do

Property	LDPE	HDPE
Clarity	Good, soft haze	Higher haze, stiffer
Flexibility	High, drapes and conforms	Low, holds shape
Puncture resistance	Good	Moderate
Heat seal window	Wide, forgiving	Narrower, needs control
Moisture barrier	Moderate	Better
Typical use	Component bags, liners, drum liners	Stiffer pouches, heavier contents

For most component packaging, LDPE is the default because it seals easily, conforms to odd shapes and does not crackle when handled. HDPE is chosen when the bag has to stand up, hold a heavier load, or provide a better moisture barrier.

Neither resin is "clean". Cleanliness comes from the additives package, the extrusion environment and the packing environment.

Additives and Extractables

Slip agents, antiblocks and plasticisers are the usual sources of extractables from a polyethylene bag. For pharmaceutical component packaging, ask for the additive package and, where the bag contacts a product-contact surface, for a USP Class VI or equivalent statement.

A bag that smells of plastic is a bag with volatiles in it. That smell is a reasonable field test before you spend money on laboratory testing.

Thickness, Size and Seal Style

Thickness is quoted in micrometres or in "mil" and drives both strength and cost. Thin bags (around 30 µm to 50 µm) suit light components and single use. Heavy components, sharp edges and any bag that will be handled repeatedly need 80 µm and above.

Seal style matters as much as thickness:

• Double-line seal. Two parallel welds with a gap between them. If one line fails, the second holds. This is the standard for any bag whose contents must remain sterile.

• Perforated flat pocket. Tear-off perforations for dispensing a strip of bags. Convenient, but perforations are weak points and particle generators — not for aseptic use.

• Flat pocket with incision. A slit that lets air escape during sealing of the outer bag. Useful when double bagging.

• Square-bottom bag. Stands upright when filled, good for bulky or liquid-adjacent components.

• Roll film. Lets the user make a bag at the point of use, at the length required, with their own sealer. Popular in cleanrooms because it removes the need to stock many sizes.

Coloured Bags Are a Control, Not a Decoration

Pink, blue and black bags are used to segregate status — rejected components, sampled material, waste. Using colour consistently removes a whole class of mix-up deviations and costs nothing extra.

Cleanroom Level and Packing

This is where most suppliers are vague and where the buyer should be precise. A bag extruded in an uncontrolled hall and packed in a warehouse carries particles on both surfaces, and the inside surface is the one that touches your component.

Ask three questions:

1. In what environment is the bag extruded?

2. In what environment is it cut, sealed and packed?

3. What is the documented cleanliness level of the packed product?

Harmake produces and packs its pharmaceutical bags in a cleanroom environment, which is the difference between a bag that is clean and a bag that is merely new.

Double Bagging

For transfer between classified areas, double bagging is standard: the component goes into the inner bag, the inner bag is wiped and placed into the outer bag, and the outer bag is removed at the destination. The inner bag never touches the outside of the outer bag, which is why the incision format and the flat pocket exist.

Handling in the Cleanroom

• Store bags in their original packaging, sealed, on a clean shelf — not on the floor and not in a cardboard box inside the clean area.

• Open the outer packaging on the dirty side of the transfer hatch and take only the inner pack through.

• Use clean or sterile gloves; a bag handled with bare hands is contaminated on the outside even if it looks untouched.

• Seal with a validated sealer and check seal integrity visually at every seal.

• Never reuse a bag. Polyethylene creases and the crease is where pinholes form.

Specification Checklist

Item	What to specify
Resin	LDPE or HDPE, virgin, additive package declared
Thickness	µm range matched to content weight and sharpness
Seal	Double-line for critical contents
Format	Flat pocket, square bottom, perforated, incision or roll film
Colour	Colour-coded by material status where useful
Cleanliness	Extrusion and packing environment stated in writing
Compliance	USP Class VI or equivalent where product contact occurs
Size range	Stocked sizes plus roll film for made-at-use bags

Harmake's cleanroom bag range covers square-bottom bags, flat pockets, perforated pockets, incised pockets, double-line sealed pockets, coloured bags, folding bags, roll film and small medicinal pockets, all produced and packed under controlled conditions for pharmaceutical and cleanroom use.

Harmake produces the whole format range under one controlled process, which means a site can standardise on a single supplier for square-bottom bags, flat pockets and roll film. A cleanroom bag is not a bag that happens to be used in a cleanroom. It is a packaging component with a resin, a thickness, a seal geometry and a cleanliness level — and it deserves the same specification discipline as the components it carries.