{"id":11033,"date":"2026-08-03T00:00:34","date_gmt":"2026-08-03T00:00:34","guid":{"rendered":"https:\/\/longchangchemical.com\/?p=11033"},"modified":"2026-08-09T15:08:16","modified_gmt":"2026-08-09T15:08:16","slug":"waterborne-plastic-sealer-additives","status":"publish","type":"post","link":"https:\/\/longchangchemical.com\/fr\/waterborne-plastic-sealer-additives\/","title":{"rendered":"Waterborne Plastic Sealer Additives: Adhesion First"},"content":{"rendered":"

Waterborne plastic sealer additives<\/strong> cannot replace correct polymer identification, mold-release removal or surface treatment. First prove the plastic grade, surface age, cleanliness, wetting tension and adhesion of the full stack. Then separate wetting from flow and cure chemistry.<\/p>\n

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Identify plastic<\/strong>
Grade, additives, texture and release.<\/div>\n
Prepare surface<\/strong>
Clean, treat and verify wetting.<\/div>\n
Seal and recoat<\/strong>
Cure, adhesion and appearance.<\/div>\n<\/div>
Original waterborne plastic sealer map: substrate and adhesion gates precede additive selection.<\/figcaption><\/figure>\n

Define the substrate precisely<\/h2>\n

Record polymer family and grade, filler, recycled content, molded or film form, texture, mold-release agent, cleaning, corona\/plasma\/flame treatment, time after treatment and storage. PP, PE, ABS, PC, PET and blends cannot share one assumed surface-energy or solvent-resistance rule.<\/p>\n

Measure treatment, then adhesion<\/h2>\n

ASTM D2578<\/a> measures wetting tension of polyethylene and polypropylene films using specified solutions. Its own scope notes that wetting tension is not a complete adhesion measure. Use it only for applicable films and correlate the result with the actual sealer and recoat.<\/p>\n

Separate the three additive routes<\/h2>\n\n\n\n\n\n\n\n
Itin\u00e9raire<\/th>\nPublished facts<\/th>\nFirst justified use<\/th>\nBoundary<\/th>\n<\/tr>\n<\/thead>\n
3071<\/a><\/td>\n0.1\u20131%; water\/solvent\/UV; surface tension <25 mN\/m<\/td>\nVerified spreading deficit after treatment<\/td>\nMay stabilize foam; no actual-plastic adhesion result<\/td>\n<\/tr>\n
3345<\/a><\/td>\n100% active; 0.1\u20131%; water\/solvent\/UV<\/td>\nMeasured film-flow or leveling defect<\/td>\nMust preserve recoat adhesion<\/td>\n<\/tr>\n
3467<\/a><\/td>\n100% active; waterborne 0.5\u20135%; OH \u226485<\/td>\nCompatibility\/leveling after chemistry review<\/td>\nUpper-limit OH cannot support exact reaction calculation<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Use 3071 for wetting, not as adhesion proof<\/h2>\n

3071 is a polyether-modified polysiloxane recommended at 0.1\u20131.0% and may be added in grinding, stirring or later. Its page describes wetting on polyethylene, polypropylene and polyester, but that application statement is not a quantified adhesion result for the actual grade, treatment and coating stack.<\/p>\n

The page warns that 3071 may stabilize foam in waterborne systems. Track wet density, foam persistence, microbubbles and pinholes along with coverage. Reject a wetting gain if the cured sealer or basecoat adhesion declines.<\/p>\n

Use 3345 for a controlled flow defect<\/h2>\n

3345 is a 100% active polyether-modified polysiloxane with a 0.1\u20131.0% range. Screen it only after application viscosity, atomization or roll settings, flash and film build are stable. Measure craters, orange peel, gloss and edge coverage at equal thickness.<\/p>\n

If co-solvent is used to enhance effect, include it in plastic stress-cracking, swelling, dry, VOC and adhesion evaluation. Better leveling cannot compensate for an incompatible plastic or untreated surface.<\/p>\n

Gate 3467 by exact chemistry<\/h2>\n

3467\u2019s page reports OH \u226485 mg KOH\/g, an upper limit rather than an exact batch value. A polyurethane reaction calculation needs batch OH, resin OH, isocyanate equivalent, solids and target NCO\/OH. Other cure systems need their own reaction and bake evidence.<\/p>\n

Without those inputs, treat 3467 as a non-stoichiometric compatibility\/leveling trial. Verify cure, plastic stress response, sealer adhesion, intercoat adhesion and service performance.<\/p>\n

Use a substrate-by-treatment matrix<\/h2>\n\n\n\n\n\n\n\n\n
Stage<\/th>\nVariants<\/th>\nPrimary measure<\/th>\nStop gate<\/th>\n<\/tr>\n<\/thead>\n
Surface<\/td>\nActual grade \u00d7 cleaning\/treatment<\/td>\nWetting tension\/contact angle and coverage<\/td>\nSurface drifts before coating<\/td>\n<\/tr>\n
Wetting<\/td>\n3071 low\/mid\/high<\/td>\nSpreading, foam, pinholes<\/td>\nAdhesion declines<\/td>\n<\/tr>\n
Flow<\/td>\n3345 low\/mid\/high<\/td>\nLeveling, craters, gloss<\/td>\nStress cracking or recoat loss<\/td>\n<\/tr>\n
Chemistry<\/td>\n3467 after data review<\/td>\nCure and compatibility<\/td>\nStoichiometry unresolved<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Test the complete coating stack<\/h2>\n

ASTM D3359<\/a> was developed for coatings on metal; if used on plastic, agree the limitation and method before testing. Record film thickness, conditioning, cut spacing, tape and failure plane. Add crosshatch, peel or pull methods appropriate to the component and customer specification.<\/p>\n

Age before release<\/h2>\n

Repeat adhesion after humidity, heat, water, cleaning chemicals, UV or thermal cycling as the end use requires. Check untreated controls and parts at different times after surface treatment. Plastic additives and mold-release residues can migrate, so an immediate pass may not remain a pass.<\/p>\n

Control application and cure<\/h2>\n

Measure wet and dry film, part temperature, flash, oven or ambient cure and the interval before the next coat. Thin spots on texture peaks and pooled film in recesses can produce different failure modes on the same molded part. Compare flat plaques with representative geometry, ribs, edges and gates.<\/p>\n

Use the same plastic lot for the first screen, then repeat on additional production lots. Track recycled-content and color-package changes because fillers, pigments and internal lubricants can change surface behavior. A candidate should pass the expected manufacturing variation, not only a specially prepared plaque.<\/p>\n

Verify recoat and assembly operations<\/h2>\n

Apply the actual basecoat or topcoat at minimum and maximum recoat intervals. Test masking, tape, adhesive, printing, heat staking or assembly operations where relevant. Inspect for stress cracking after cleaners and co-solvents. A sealer is successful only if it improves the entire stack without weakening the plastic component.<\/p>\n

Decision rules<\/h2>\n