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Date：2026-11-03Why does power bank mould need two stages, and why does a box keep moulding after the shell has been wiped? Mould on the shell grows in the assembly gaps and the oil film on a gloss face, while mould in the box grows in the moisture trapped between board and tray. Blend iHeir-JS117 into the PC shell compound at 0.5%-1.0% of compound weight, and put iHeir-D vapour sheets in the colour box at 0.1-0.2g of active matter each. This article covers the mixing stage, the sheet count and the packing.
1. Mould sits in the shell gaps, and in the box and tray
Take a power bank apart: PC or PC/ABS shell and top panel, lithium cell, PCBA, buttons and ports, TPU soft edge, colour box, plastic tray, leaflet and cable. The cell and the PCBA do not mould. The shell surface, the soft parts and the paper and plastic packaging do.
The shell fails at the surface. A gloss PC part has low surface energy, and release agent plus fingerprints are hard to wipe off; parting lines, button slots, port recesses and the edge of the indicator window all collect dust. Once store humidity rises, those points spot, and wiping leaves a haze on the gloss face that ends in a downgrade.
The packaging fails because it is closed. A printed box with a plastic tray becomes a small sealed space: board takes water, the tray does not breathe, and the moisture has nowhere to go. Made in a wet season and held two or three months through a pre-season build-up, the box opens onto spots along the tray edge while the unit itself looks clean.
The two causes differ. Shell mould comes from line and store humidity; box mould comes from that small sealed volume. Do the shell only and the box still fails on opening; add sheets only and the spots on the machine stay.
2. Powder in the shell, sheets in the box
The table lines up the shell, the soft edge, the box and the tray. Plastic is dosed on compound weight, paper on active matter per sheet, and the two are not convertible.
| Part | Material | Product and level | Stage | Control point |
|---|---|---|---|---|
| Shell, top panel | PC, PC/ABS | iHeir-JS117 0.5%-1.0% of compound | Premix before moulding | Well dispersed, gloss trial first |
| Colour box, tray | Board, PET sheet | iHeir-D 0.1-0.2g per sheet | Before the box is closed | Trial at three times the dose |
| TPU soft edge | Thermoplastic elastomer | Run with the shell compound | Moulding | Trial-moulded with the shell |
| Cable, leaflet | PVC, paper | Paper per unit, humidity control | Boxing | Store below 60% RH |
One boundary. A vapour sheet acts only inside a closed space and never reaches a machine left out in the open; powder in the shell does not evaporate into the box either. Run both stages for a clean box on opening.
3. PC shell: disperse the powder properly, trial the gloss face first
Shell, top panel and button seat take iHeir-JS117 plastic anti-mould powder at 0.5%-1.0% of finished part weight. It is a nitrogen heterocycle phenol-alcohol compound with more than 97% active matter, 380 kg/m³ bulk density, 110μm mean particle size, insoluble in water and leaching-resistant.
Where to add it. Blend it thoroughly with the compound and mould as usual. Plants compounding in house mix it with PC pellets and pigment in a high-speed mixer, then pelletise or feed the machine; those buying compound have it blended at the pelletising stage. Scooping powder into the hopper does not work: at 110μm the barrel shear is far too brief, and the result is a hazy streak across a gloss face.
Trial the gloss face on its own. Power bank shells are usually moulded gloss without paint, so any shade shift or haze shows. Run trial sets at 0.5% and 1.0%, compare both against an unfilled control under standard light for hue shift, haze and flow marks at the parting line, then release; the first production run is no place to find out.
Three points. First, polymer: JS117 covers PVC, PU, silicone resin, polyolefins and polyester systems, while PC and PC/ABS sit outside that list, so a small trial for compatibility and impact strength comes first. Second, above thirty percent regrind, go to 1.0%. Third, run clear shells and pale panels as their own batches, not shared with dark parts. The general selection route is in masterbatch or powder for moulded parts.
4. Colour box and tray: one sheet to a box, after a compatibility trial
The paper stage uses iHeir-D gas-phase anti-mould paper, a speciality ink carrying anti-mould particles coated onto paper, which works once sealed with the goods. The dose basis is 0.1-0.2g of active matter per sheet: one sheet inside a box holding a single unit, and one against each carton wall plus sheets between layers for multi-unit cartons.
Placement. Put the sheet between the tray and the lid rather than flat against a mirror face or a printed panel; vapour settles downward once the lid closes, so a sheet above covers more evenly than one underneath. Close the box soon after packing and carton it the same day to limit air exchange.
The compatibility trial is not optional. Boxes use dyed board, foil stamping and metal clasps. Put three times the normal dose into the box under test, mist a little water, separate the sheet from the box wall with paper, close it and inspect after a few days for fading, yellowing or dulled metal. iHeir-D carries 70%±5 solids, and under damp conditions it really can corrode a poor-quality metal clasp, so foil and magnetic closures get the trial first. Sheet selection is covered in choosing anti-mould packaging paper.
5. Assembly, cartoning and export
Risk at assembly sits in exposed work in progress: moulded shells wait in totes for assembly while soft edges and buttons lie loose at the bench. Move shells within the shift, lid the totes, dehumidify the bench and hold the shop below 60% RH; let assembled units reach room temperature before bagging, since a warm unit sealed in a bag traps its own moisture.
At cartoning, sheet the colour box, close it, then carton, and put cartons on pallets 10cm off the floor and 10cm off the wall. At sea, container condensation is far harsher than the inside of a box, so leave an air path and keep cartons off the wall; see small appliance export anti-mould.
Release at three levels: shells to ASTM G21 or ISO 22196, sampling one gloss face and one parting line; colour boxes to GB/T 24346-2009, sampling one box wall and one tray; complete units for 30 days at 30℃/85% RH, opening to check shell gaps, tray edges and leaflets. Put all three on one shipping inspection sheet.
6. Questions on sheets, fading and over-dosing
Q: With powder in the shell, can the box skip the sheet?
No. While the unit sits sealed in the box, mould starts from the board and the tray, and powder in the shell never reaches that space; sheets alone leave the spots on the machine.
Q: Will the sheet fade the box printing?
There is a risk. Poor dyes react to the vapour, which is why the trial at three times the dose comes first; high-value foil and spot-colour boxes deserve a small trial pack before a full run.
Q: More sheets must be safer, surely?
No. Stay inside 0.1-0.2g of active matter per sheet, taking the upper figure for large boxes, many layers or long storage, because piling sheets on raises the risk of fading and metal corrosion rather than adding protection.
Four points to take away: blend iHeir-JS117 into the PC shell and top panel at 0.5%-1.0% of compound weight, with trials at 0.5% and 1.0% read for shade and haze; put iHeir-D vapour sheets in the colour box and tray at 0.1-0.2g of active matter each, after a trial at three times the dose; move shells within the shift, cool units before bagging and hold the shop below 60% RH; leave an air path in the container. A 1kg powder sample and a pack of sheets go out for a trial first, with MOQ and lead time on the iHeir-JS117 product page.
