PP and HDPE are not attacked by ester-based chemical UV filters or oil-rich SPF emulsions and are the default contact materials, with glass where premium. PET is fine for most SPF emulsions but fails above ~30% ethanol (spray and after-sun formulas), swelling and hazing. AS (SAN) is attacked, PMMA acrylic crazes and clouds, and standard NBR or TPE gaskets swell — so acrylic is used only as an outer shell over a PP inner, and gaskets are silicone or fluoroelastomer. The confirming test is the actual bulk in the actual component at 48°C, RH 75%, for 30 days with ambient and cold controls, passing only with no discolouration, odour, swelling, cracking or decoration attack.
What in a sunscreen does the damage
Three things. The organic (chemical) UV filters are largely esters and aromatic compounds dissolved in the oil phase at high loadings — far higher than the fragrance level that already troubles clear plastics. The oil phase itself is large, because filters need a solvent and a water-resistant film needs emollients. And many SPF products carry silicones for spreadability or ethanol for a dry-touch or spray format. Each acts on plastics differently: esters and aromatics dissolve into and stress-crack the amorphous clear resins; oils extract plasticisers from cheap elastomers; low-surface-tension silicones creep past threads and wick through pump seals; ethanol swells PET.
Material by material
| Material | Attacked by SPF filters? | Where it fails | Verdict for sunscreen |
|---|---|---|---|
| PP (polypropylene) | No | Handles pH below 4; lower dimensional precision than PET; moulded-in white never matches sprayed white | Default contact material — airless inner, jar inner cup, stick barrel, pump components, caps |
| HDPE | No | Sprayed coatings scuff without a wet-rub requirement | Default for body-SPF lotion bottles and tottles; softens 125–135°C |
| PET | Not by the filters; by ethanol | Swells, hazes and deforms above ~30% ethanol; avoid hot-fill above ~60°C | Acceptable for SPF emulsions without alcohol; ruled out for spray sunscreens and alcohol after-sun |
| PETG | Rarely | Costs more than PET; check each grade against the alcohol level | Alcohol-rated grades exist for spray formats |
| AS / SAN (clear styrenic) | Yes | Attacked by ester filters, oils and fragrance; crazes | Do not use in contact with SPF |
| PMMA acrylic | Yes | Crazes and clouds in contact with oil-rich or ester-rich bulk | Outer shell only, over a PP inner that carries the product |
| Glass | No | 2–3× the weight of plastic; breakage in transit; amber or cobalt for UV | Premium face SPF, oil-serum SPF, alcohol formats |
| Single-layer PE tube | Not chemically, but no barrier | Oxygen transmission 150–300 units — oxidation-sensitive actives brown | Mineral bulks only |
| 5-layer PE/EVOH co-ex tube | No | EVOH 15–20 µm layer; OTR 0.2–1.2 | Face and body SPF, especially with vitamin C, retinol or peptides |
| ABL (aluminium barrier laminate) tube | No | Stays squeezed (no spring-back); visible side seam | Easily oxidised or strongly fragranced SPF; best barrier |
| NBR / TPE standard gaskets | Yes | Swell; extract plasticisers; a 0.2 mm swell in an aerosol valve is a leaking can | Specify silicone or fluoroelastomer; PTFE-coated or solvent-grade for alcohol |
The practical shortlist is therefore short: PP or HDPE in contact, EVOH or ABL for tubes, glass for premium, with any clear or metallic decoration carried on an outer part that never sees the bulk. That rule set is why a sunscreen airless bottle is always a PP inner behind a PP or acrylic shell, and why the sunscreen packaging formats look the way they do. The same nine rules across every formula type are on the formula-to-packaging compatibility matrix.
The 48°C / 30-day compatibility test
A rule shortlists; a test confirms. The industry method used by partner factories operating to ISO 22716 / GMP is a 30-day accelerated hold, run on the first sample set — in parallel with production sampling, so it does not add a month to the calendar if it is started on day one.
| Element | Specification |
|---|---|
| Sample | The actual SPF bulk in the actual component — the exact resin grade, gasket compound, decoration and closure that will ship, not a stand-in |
| Conditions | 48°C, RH 75%, for 30 days; ambient (25°C) and cold (−15°C or 5°C) controls run alongside |
| Orientation | Filled and capped, held upright and inverted so the bulk contacts liner, thread and dispenser |
| Read-outs | Discolouration of bulk or pack; odour; swelling, softening or crazing of any part; stress cracks at threads and the airless collar; decoration lift or bleed; pump or valve function after the hold; weight loss |
| Pass | No visible or functional change on any read-out at 30 days; pump still primes within 10 strokes and dispenses; weight loss within the leak threshold |
| Companion tests | Colour migration in 75% alcohol at 48°C for 12 hours on decorated parts; seal hold at 45°C for 24 hours; vacuum leak −0.08 MPa for 15 minutes, loss ≤0.5% |
| Why 48°C | A sealed container or a car in summer reaches 45–50°C; 30 days at 48°C is the accepted accelerated proxy for a shelf life at ambient |
Two things buyers get wrong. First, running the test with water or a placebo emulsion — a pump that primes in five strokes with water can need fifteen with an SPF bulk, and water attacks nothing. Second, testing a sample from a different resin lot or a different gasket supplier than the production run; the compatibility result belongs to the exact bill of materials it was run on, and any change to the BOM re-opens it. The test sits under the four inspection gates on cosmetic packaging quality standards.
Adjacent failures the 30-day hold catches
- Acrylic shell clouds or crazes — an SPF jar or bottle quoted without a PP inner. Caught at spec; confirmed at 30 days.
- Formula browns or smells in the tube — single-layer PE chosen for an oxygen-sensitive filter system. Caught by OTR at spec; confirmed at 48°C.
- Pack yellows on a sunny shelf — clear or white resin without UV additive. Caught by a separate UV test: 24 h UV, one week in sun, or a 300 W lamp at 50°C for 48 h, no visible colour shift (≈ one year of UV).
- Tube leaks at the shoulder in cabin pressure — oily bulk creeping past a wide seal at low torque. Caught by −0.08 MPa for 15 min and 24 h inverted.
- Aerosol can weeps at the valve — gasket compound not specified against the propellant blend. Caught by gasket swelling measurement; a 0.2 mm swell is a leaking can.
Tube structures and barrier numbers are on cosmetic tube specifications; the airless test sheet is on airless, pump and sprayer specifications.
Writing it into the brief
Give the packaging partner the formula sheet before the mood board: filter system (organic, mineral or hybrid), oil-phase percentage, ethanol percentage, silicone content, viscosity in mPa·s, pH. From that the contact material is chosen in one step — PP/HDPE, EVOH/ABL, or glass — and the shape is chosen inside that constraint. Then write three lines into the order: “contact materials PP / HDPE / EVOH only; acrylic exterior only; gaskets silicone or FKM”, “48°C / RH 75% / 30-day compatibility on actual bulk before PO release”, and “vacuum leak −0.08 MPa 15 min ≤0.5%”. Minimums and lead times by route are in sunscreen packaging at low MOQ from China and the MOQ index 2026; face SPF within a routine is in the skincare packaging solution.
Vella is a Guangzhou-based beauty packaging solutions provider — a sourcing partner, not a factory — that routes briefs like this one to vetted partner factories operating to ISO 22716 / GMP, matches the components as one set, and runs the tests above on filled samples before any production run. The supplier questions that reveal whether a factory actually runs this hold — or just quotes it — are in how to evaluate a China packaging supplier; send your formula sheet via the contact page.
Common questions
Send the formula sheet,
get the material shortlist.
Filter system, oil phase, alcohol, silicone, viscosity, pH. We reply within 24 hours with the eligible contact materials and a 30-day test plan on your actual bulk.
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