Pigment & Filler Decks for Wearable NR Film
Safety. Pigments and fillers change skin-contact extractables and aging chemistry; food-contact colorant lists are not wear certificates. Metal impurities (copper, manganese) consume antioxidant capacity. This article is compounding literacy, not a recipe card.
Executive summary
Wearable NR film gets color and opacity from compounding (pigments and fillers in the latex before the film forms) or from buying already-colored sheet. Surface paints and undispersed powders are a different failure class. Fillers and some polymeric modifiers raise modulus and can cut stretch; metal impurities accelerate aging.
Use this when choosing tint strategy for a cast compound versus ordering colored roll goods, or when a “paint it on” shortcut is proposed — see Liquid Latex Painting vs Compounding Pigment. Pair with Gauge, Modulus & Reduction for stiffness trade-offs.
How color and opacity enter NR film
Three industrial routes — only two belong in wearable film design.
Liquid latex work — compound before film formation
Liquid latex work default: compounding materials include optional dyes and pigments as elastomer-phase modifiers alongside sulfur, zinc oxide, accelerators, antidegradants, clays, and softeners. A film from raw latex is not a saleable article until compounded. Color is part of the compound package, not an afterthought on cured film.
What is compounding?
Compounding is mixing rubber latex with curatives, fillers, pigments, and protective chemicals before the film forms. You tint the bottle (or batch tank) before you cast or dip — not after cure with unrelated paints.
Sheet-based work — buy formed, optionally pre-colored sheet
Sheet-based work: calendered or catalog NR sheeting may ship in standard colors. The mill already compounded and formed the film. You inherit opacity, modulus, and aging package as sold.
Rejected for stretchy NR film — surface-only decoration
Craft “liquid latex paint,” styrene-acrylic construction dispersion, or undispersed textile dye added after cure is not documented NR compounding. Industrial aqueous pigment dispersions marketed for rubber latex are the documented tinting path — still liquid-latex prep, not brush-on afterthought. See Printing & Surface Decoration for post-cure decoration.
Pigment and filler identity buckets
| Bucket | Prep rule | Wearable film note |
|---|---|---|
| Aqueous pigment dispersion | Add when compound stable | Vendor TDS may list rubber latex |
| Dry pigment powder | Dispersion <5 µm before latex | Undispersed powder shocks colloid |
| Oil-phase colorant | o/w emulsion first | Poor emulsion → oil spots on film |
| Mineral filler | Slurry before latex | Modulus ↑; keep load low for soft sheet |
| Polymeric filler (high-styrene SBR) | Add as latex | Tear ↑; modulus and set ↑ |
Insoluble solids and immiscible liquids must be dispersed or emulsified before latex addition or colloidal stability is upset.
Loading trade-offs you will feel in wear
Mineral clay. Handbook example: DIXIE clay 0 → 50 phr drops tensile 3100 → 1500 psi while stress at 500% rises 500 → 1100 psi — stiffer, weaker in tension.
High-styrene SBR filler. At 20 pphr, crescent tear 1769 N/cm, modulus at 300% 2.76 MPa, permanent set 30%; handbook flags modulus rise as disadvantage for some applications.
What does phr mean?
phr means parts per hundred rubber — how much of each ingredient is added relative to 100 parts of dry rubber in the recipe. It is the standard counting unit in rubber compounding tables.
Filler band (adhesive analogy). Typical mineral filler 0–30 pphp; higher load cuts tack while increasing stiffness.
Metal impurities and aging
Copper protection needs 2 phr total antioxidant; coarse dispersions → uneven protection. Spec NR concentrate limits Cu/Mn at 8 mg/kg solids (ISO 2004). Pigments can re-introduce metal catalysis. See Antidegradants in DIY Compounds and Aging, Storage and Care.
Sheet-based vs liquid latex decision cues
Liquid latex work: batch color, opacity control, tear tuning via polymeric filler; accept prep discipline.
Sheet-based work: colored sheet without millroom; you inherit vendor formulation.
See Sheet vs Liquid Film Pathways for pathway choice.
Deep dives (optional)
Deep dive: High-styrene SBR polymeric filler (Table 16.12)
NR base compound; high-styrene SBR at 0/10/15/20 pphr; vulcanize 15 min @ 93°C.
| pphr | Modulus 300% (MPa) | Tensile (MPa) | Eb (%) | Tear (N/cm) | Set (%) |
|---|---|---|---|---|---|
| 0 | 0.90 | 28.6 | 880 | 1156 | 6 |
| 20 | 2.76 | 26.9 | 730 | 1769 | 30 |
Plant example — not a home mixing card.
Deep dive: Dispersion and emulsion prep
Dispersions: <5 µm target; Hegman grind gauge; remix before weigh-up. Emulsions: drop test QC; homogenize ≤38°C.
Deep dive: Mineral clay filler curves
DIXIE clay 0/25/50 phr CR example: tensile and stress @500% trends — filler stiffens at the cost of ultimate tensile.