Antiblock Additives: 5 Types, Mechanisms, Dosage and Selection

Antiblock additives are fine mineral or organic particles that roughen the surface of a plastic film so that adjacent layers cannot stick together, and the 5 types used in film, silica, talc, nepheline syenite, calcium carbonate and organic beads, run from about 1,000 ppm to 20,000 ppm of the film. Blocking stops film from unwinding, opening or sliding on packaging lines, so which particle solves it with the least haze?

Antiblock additives are one of the 7 processing modifiers among the 43 families of plastic additives, and they reach the film as a concentrate rather than as a loose powder: antiblock is one of the masterbatch types listed for biaxially oriented polypropylene film, beside antistat, antifog, migrating slip, non-migrating slip and white. The particles themselves are ordinary industrial minerals, and 4 of the 5 types appear on the same food-contact lists as fillers and colorants.

This page defines blocking and the antiblock mechanism, sets out the 5 types in the order of the dosage evidence behind them, matches each type to a film and a polymer, gives the dosage window in ppm and wt%, explains how antiblock interacts with slip agents, antistats and stabilizers, lists the 4 test methods, states the EU and US food-contact positions, names the mineral producers and masterbatch makers, and closes with the complete list of the 8 antiblock substances that carry their own page on this site.

Table T1. The 5 antiblock types at a glance.

Levels are trial or study values from Ampacet, from Van Essche, Kromminga and Schmidt (2000) and from Dziadowiec and colleagues (2023), not grade recommendations. Refractive indices come from the substance records in our source library.

What Is an Antiblock Additive?#

An antiblock additive is a particulate additive, usually a mineral such as silica or talc, that creates micro-roughness on a film surface and so reduces the contact area and van der Waals adhesion between two film layers. The particle does no chemistry. It works by geometry, because a surface carrying protrusions touches the opposing surface at fewer points than a smooth one does. That is why the same 5 minerals and beads serve across polyethylene, polypropylene and polyester film, and why the effective level is set by particle size and shape rather than by the polymer.

The trade uses several names for one function. The spellings anti-block, antiblocking agent and antiblock agent all denote the particulate additive described above, and an anti-blocking agent is the same thing again. Both standard reference works treat the class as its own chapter: the Hanser Plastics Additives Handbook carries a chapter titled "Anti-blocking Additives", and Murphy's Additives for Plastics Handbook groups it with lubricants, mold release agents and slip. An antiblock additive is not a lubricant, not a release coating and not a slip agent, and the next two sections separate it from each. Why do smooth films stick in the first place?

What is blocking in plastic film?#

Blocking is the unwanted adhesion of two plastic film layers in a roll, a bag or a stack, caused by van der Waals attraction across smooth surfaces held in close contact. Two polyolefin surfaces pressed together by winding tension or by the weight of a pallet approach one another closely over a large real contact area, the short-range attraction holds, and the film then behaves as if the layers were welded. The force needed to pull them apart is what the blocking test measures: ASTM D3354-21 reports the load in grams required to separate two 100 cm2 film specimens, with a maximum of 200 g, and ISO 11502 Method B follows a similar principle.

The term blocking covers roll, bag and stack adhesion alike, and it appears at 4 points in the film value chain.

• Roll unwinding, where blocked layers tear or stretch as the reel runs off
• Bag and pouch opening, where the two walls of the bag will not separate at the filling machine
• Film-to-film sliding on packaging lines, where blocked surfaces stall the transport
• Stacked sheets and folded film in storage, where load and time raise the separation force

What is the difference between antiblock and slip additives?#

Antiblock additives keep film layers apart with solid surface particles, while slip additives such as erucamide migrate to the surface and lower the coefficient of friction, so most polyolefin films carry both. The antiblock particle is insoluble and stays where the melt put it. The slip amide dissolves in the melt, becomes incompatible as the film cools and blooms to the surface over hours and days: erucamide reaches most of its coefficient-of-friction reduction within 24 to 48 hours and its final value after 7 to 10 days. Slip agents are used in plastics to control that friction, which is why their performance is measured under ASTM D1894 rather than with a blocking test.

The two classes also sit at different levels. Slip amides are dosed at 0.05 to 0.12 wt%, or 500 to 1,200 ppm, in LDPE and LLDPE film, while antiblock minerals run from 1,000 ppm to 20,000 ppm. They are chemically coupled as well: erucamide adsorbs on the antiblock particle, which is the most common single cause of film that never reaches its target friction. Amide chemistry, bloom rate and dosing are compared on slip additives for plastic film.

How Do Antiblock Additives Work?#

Antiblock additives work by standing proud of the film surface: particles in the outer layer lift the next layer away, cut the real contact area and so cut the van der Waals adhesion that causes blocking. The mechanism is recorded the same way for every type in our source library. Diatomaceous earth gives surface roughness through irregular porous particles. Nepheline syenite particles protrude from the film surface and create micro-roughness that reduces contact area and van der Waals adhesion. Silicone resin beads in a BOPP skin layer are sized at about 40 % of the skin-layer thickness, so part of each bead sits above the surface.

The mechanism runs in 3 steps.

1. Protrude: a particle larger than the natural roughness of the polymer surface projects from the film face.
2. Separate: the protruding particles hold the next layer at a distance, so the real area of contact between the two surfaces falls.
3. Release: van der Waals adhesion, which acts only across that real contact area, falls with it, and the blocking load measured under ASTM D3354 drops.

How particle shape, size and refractive index set the haze trade-off#

An antiblock particle blocks best when it is irregular and large enough to stand above the film surface, and it costs least clarity when its refractive index is close to that of the polymer, as with diatomaceous earth in polyethylene. Four particle properties decide where a grade lands between those two ends.

• Shape. Irregular and platy particles outperform blocky ones. In Ampacet's film trials the porous, irregular diatomaceous earth and the platy talc were the efficient antiblocks, while blocky calcium carbonate, whose aspect ratio is 1 to 3, needed 250 to 300 % more loading for the same effect.
• Top cut. The coarsest particles in the distribution do the antiblock work and also set the defect risk. The top cut of a diatomaceous earth grade can reach 44 µm against a film only 25 µm thick, so selection by top cut matters more than selection by mean size.
• Refractive index. A refractive index close to that of the polymer limits haze, which is the documented reason diatomaceous earth suits polyethylene. The measured values across the types are 1.459 for synthetic amorphous silica, 1.58 for talc, 1.6584 for calcite and 1.42 for silicone resin beads. Our source library records no general numerical law linking refractive-index mismatch to haze, so these values rank the types against each other rather than predict a haze figure.
• Hardness. Diatomaceous earth sits at Mohs 5.5 to 6 and is abrasive to screws, dies and slitting knives, while talc is the Mohs 1 reference mineral and is not.

5 Types of Antiblock Additives#

The 5 types of antiblock additives are silica (natural diatomaceous earth and synthetic amorphous silica), talc, nepheline syenite, calcium carbonate and organic antiblocks such as silicone resin beads. Three of the 5 are natural minerals, one is a synthetic mineral and one is organic, and they appear in that order throughout this page: the order follows the dosage evidence, from the two minerals that performed best in the published film trials to the specialty class used in high-clarity skin layers.

1. Silica antiblocks#

Silica antiblocks are silicon dioxide particles from two sources, natural diatomaceous earth and synthetic amorphous silica, and together they form the most fully documented antiblock class in our source library. Both carry the same food-contact logic and the same adsorption behaviour toward slip agents and antistats. They differ in particle architecture, in hardness and in the level at which they work, which is why the two are treated separately below.

Diatomaceous earth (natural silica)#

Diatomaceous earth is a natural siliceous sediment of fossil diatoms, 80 to 90 % SiO2, whose irregular porous particles make it one of the two efficient antiblocks in Ampacet's film trials at 2,500 to 10,000 ppm. It also carries 2 to 4 % alumina and 0.5 to 2 % iron oxide, and it trades under the synonyms diatomite, kieselguhr, celite, moler and tripolite. Filler grades have a mean particle size of 4 to 30 µm, a Mohs hardness of 5.5 to 6 and a density of 2 to 2.5 g/cm3. Its refractive index is close to that of polyethylene, which limits the haze penalty in PE film.

Three properties constrain its use. The top cut can reach 44 µm against a 25 µm film, the Mohs 5.5 to 6 hardness makes it abrasive to equipment, and the 0.5 to 2 % iron oxide content can accelerate polymer degradation. Identity and status: CAS 61790-53-2 for natural diatomaceous earth and CAS 68855-54-9 for the soda ash flux-calcined grade, EU FCM No 707 (Ref 46375) and FCM No 734 (Ref 46380) with no specific migration limit, and a listing in 21 CFR 178.3297. Calcined grades contain crystalline silica, which changes the occupational picture and is treated below the contextual border.

Synthetic amorphous silica#

Synthetic amorphous silica is a manufactured silicon dioxide, mainly in precipitated grades, that gives antiblock below 0.5 wt% and, in high pore-volume grades, at 1,000 to 1,500 ppm. Dziadowiec and colleagues report the level below 0.5 wt% for precipitated silica in their 2023 cast-film review, and Van Essche, Kromminga and Schmidt found high pore-volume silica effective at 1,000 to 1,500 ppm in the Journal of Plastic Film and Sheeting in 2000. That makes synthetic silica the lowest-loading antiblock for which our source library holds a figure, roughly one tenth of the calcium carbonate level.

Precipitated silica is porous, with primary particles of 5 to 100 nm, agglomerates of 1 to 40 µm, a specific surface area of 5 to 100 m2/g, a Mohs hardness of 5.5, a density of 1.9 to 2.1 g/cm3 and a refractive index of 1.459. Its identity is CAS 7631-86-9 and EC 231-545-4, the current numbers for synthetic amorphous silica, while 112926-00-8 is a former precipitated-silica CAS that still appears on safety data sheets. In the EU it is FCM No 504 (Ref 86240), with silanated grades at FCM No 87, and amorphous silica is not on the California Proposition 65 list. Fumed silica shares the same CAS and EC numbers, but our source library documents it as a thickener and reinforcing filler, not as a film antiblock grade.

2. Talc antiblock#

Talc antiblock is a platy hydrated magnesium silicate that matches diatomaceous earth in antiblock efficiency at 2,500 to 10,000 ppm and is used at up to 5 wt% in polypropylene blown film. The 5 wt% figure comes from the 2023 review by Dziadowiec and colleagues, and the 2,500 to 10,000 ppm window comes from the Ampacet trials, in which talc and diatomaceous earth were the two efficient minerals. Talc is Mg3Si4O10(OH)2, CAS 14807-96-6, EC 238-877-9, with platelets of aspect ratio 5 to 40, a mean size of 0.5 to 20 µm, a refractive index of 1.58 and a Mohs hardness of 1, the softest of the 5 types and the kindest to dies and slitting knives.

Talc in plastics is not only a film antiblock. It is the platy reinforcing filler that raises stiffness, heat distortion temperature and dimensional stability, and it nucleates the alpha phase in polypropylene, with plastics taking 32 % of US talc sales in 2024 according to the USGS Mineral Commodity Summaries 2025. That broader role, including loadings of 10 to 40 wt% as a filler, is covered in talc in plastics.

One formulation caution applies specifically to talc. Its Lewis-acid surface sites can catalyse polymer oxidation and depolymerization at elevated temperature, and talc adsorbs phenolic antioxidants and HALS, with a loss of stabilizer activity. In food contact it is EU FCM No 615 (Ref 92080) with no specific migration limit, and it is listed as magnesium silicate in 21 CFR 178.3297. Its hazard classification status is set out below the contextual border.

3. Nepheline syenite#

Nepheline syenite is a quartz-free sodium potassium aluminosilicate mineral that serves as a low-refractive-index antiblock and functional filler in polyolefin film, with crystalline silica below 0.1 % in the MINEX grades of Covia. It is a natural silica-undersaturated rock of nepheline plus alkali feldspar, CAS 37244-96-5, EC list number 609-369-8, with the idealised formula Al2KNaO8Si2. Its irregular particles protrude from the film surface and create the micro-roughness that reduces contact area and van der Waals adhesion, the same geometry as diatomaceous earth but from a mineral that carries no free quartz.

Two properties explain why film producers reach for it. The relatively low refractive index limits the clarity penalty, and the crystalline silica content below 0.1 % removes the respirable-silica question from the handling area. Our source library holds no published dosage for nepheline syenite in film, so it is specified by grade and particle size rather than by a ppm window. On regulation it is EU FCM No 684 (Ref 68125) with no specific migration limit, no active REACH registration is on file because natural minerals that are not chemically modified are generally exempt under REACH Annex V, and it is not on the Candidate List as of 22 September 2026. Most searches for this mineral concern ceramics and glass, which sit outside the scope of this page.

4. Calcium carbonate#

Calcium carbonate is a low-cost blocky mineral antiblock that needs 250 to 300 % more loading than diatomaceous earth or talc, so trial levels run from 2,500 to 20,000 ppm. Both figures come from the same Ampacet film trials that set the 2,500 to 10,000 ppm window for the two efficient minerals, and the reason is geometric: calcite particles have an aspect ratio of 1 to 3 and present a blunt face to the opposing layer instead of an irregular or platy one. CAS 471-34-1, a Mohs hardness of 3 to 4 and a calcite refractive index of 1.6584 complete the picture, and that refractive index is the highest among the 5 types.

Calcium carbonate in plastics is used far more as a volume filler and extender than as an antiblock, at 20 to 40 % in polypropylene and up to 70 phr in PVC cable compounds, and at those levels the difference between ground and precipitated grades matters; both are compared in calcium carbonate in plastics. In food contact it is EU FCM No 21 (Ref 42500) under the entry for salts of carbonic acid, with no specific migration limit, and in the US it is listed both in 21 CFR 178.3297 and as GRAS in 21 CFR 184.1191.

5. Organic antiblocks: silicone resin beads and fatty amides#

Organic antiblocks are polymer beads and waxy amides, such as methylsilsesquioxane microspheres and stearamide, that roughen or harden the film surface without a mineral filler, mainly in high-clarity BOPP skins. Methylsilsesquioxane, CAS 68554-70-1 and EC 614-610-5, is a silicone resin microsphere sold under the Tospearl name and used as a light diffuser as well as an antiblock and slip additive in film. Its refractive index is 1.42, the lowest of the 5 types, and its commercial grades span 1.8 to 2.3, 2.3 to 3.1, 4.0 to 5.0 and 8.5 to 10.5 µm, chosen so that the bead diameter is about 40 % of the skin-layer thickness in BOPP film. In the EU it carries FCM No 730 (Ref 66930) with a restriction of less than 1 mg residual methyltrimethoxysilane per kg of methylsilsesquioxane.

The amide route is different in kind. Stearamide, CAS 124-26-5, is a saturated C18 amide whose chain crystallises at the film surface, and our source library records its effect as antiblock and release rather than low friction, which is what separates it from the unsaturated slip amides. It is EU FCM No 306 and falls under the saturated fatty acid amides of 21 CFR 178.3860. Ethylene bis stearamide, CAS 110-30-5, is a secondary bis-amide that works as internal and external lubricant, dispersant, release agent and antiblock, but not as a classic film slip additive, and it is EU FCM No 250 with no specific migration limit. Neither amide replaces a mineral antiblock where blocking loads are high: both are chosen where release and surface hardening matter more than a large cut in contact area.

Which Antiblock Additive Suits Each Film and Polymer?#

The best antiblock depends on the film: diatomaceous earth, talc or synthetic silica for LDPE and LLDPE blown film, talc at filler level for polypropylene blown film, and fine silica or silicone resin beads in the skin layers of BOPP. The polyethylene film package in our source library is explicit: slip at 0.05 to 0.12 %, antiblock at 2,500 to 10,000 ppm for diatomaceous earth or talc or 2,500 to 20,000 ppm for calcium carbonate, plus a processing aid, antifog and antistat. Polypropylene needs slip and antiblock specifically in its biaxially oriented grades, where antiblock is one of the named masterbatch types.

Table T2. Antiblock choice by film and polymer.

Two cells in the matrix stay open on purpose. Our source library carries no sourced antiblock type or level for HDPE film or for PET film, so this page names no grade for them; the decision there is made from the blocking target, the film gauge and the clarity limit, exactly as in the 6 steps below. The full stack that surrounds the antiblock in a converted structure, slip, antifog and antistat together, is on additives for packaging film.

How to select an antiblock additive in 6 steps#

Select an antiblock additive in 6 steps: define the blocking target, match particle size to the film, set the clarity limit, check the slip and antistat package, screen food-contact status and confirm the dose by trial. Each step produces a number or a constraint that narrows the grade list, and the order matters because step 4 can overturn a choice made in step 2.

1. Define the blocking target with ASTM D3354. Fix the acceptable separation load in grams per 100 cm2, remembering that the method tops out at 200 g.
2. Match the particle to the film gauge and the layer. Compare the top cut of the grade against the film thickness, since a 44 µm particle in a 25 µm film becomes a defect, and size beads at about 40 % of the skin-layer thickness in coextruded BOPP.
3. Set the clarity limit. Choose the type whose refractive index sits closest to the polymer where haze is critical, and accept a higher-index mineral only where the film is not a clarity application.
4. Check the slip, antistat and stabilizer package for adsorption. Synthetic silica adsorbs slip agents and antistats, and talc, kaolin and silica adsorb antioxidants and HALS on their acid sites.
5. Screen food-contact status in each market. Confirm the EU FCM number for every type in the formulation and the 21 CFR 178.3297 listing for the mineral grades.
6. Run trials across the dosage window and measure the result. Cover 2,500 to 10,000 ppm for diatomaceous earth or talc, and measure coefficient of friction and haze alongside the blocking load.

The general method behind these steps, including how the constraints from several additive families are reconciled, is on how to select plastic additives.

How Much Antiblock Additive Is Needed? Dosage in ppm and wt%#

Antiblock levels run from about 1,000 ppm for high pore-volume silica to 20,000 ppm, or 2 wt%, for calcium carbonate, with diatomaceous earth and talc in the middle at 2,500 to 10,000 ppm. The spread of 20 to 1 between the lowest and the highest figure is a particle-efficiency spread, not a quality difference: every value below is a trial or study range for a named grade type, measured in the film rather than in the concentrate.

Table T3. Antiblock level by type.

These are trial and study ranges, not supplier recommendations for a named grade.

The unit convention is simple and worth stating once, because film specifications mix the two. 10,000 ppm equals 1 wt% of the film, so the diatomaceous earth window of 2,500 to 10,000 ppm is the same as 0.25 to 1.0 wt%, and the 5 wt% talc level in polypropylene blown film is 50,000 ppm. Level also moves with film gauge, in the same direction as it does for slip: the thicker the film, the lower the additive concentration needed for the same surface effect, because surface area per unit mass falls. The unit rules, including phr and the conversion to wt% and ppm, are on conversion to wt% and ppm.

How is antiblock masterbatch let down?#

Antiblock masterbatch is let down at the extruder so that the concentrate supplies the target ppm in the finished film, and the dose follows from one division: the target level divided by the antiblock content of the masterbatch. Film plants buy antiblock as an additive masterbatch rather than as a powder, because the mineral disperses better from a pre-compounded carrier and because dosing a few percent of pellets is more repeatable than dosing a few tenths of a percent of a fine powder. Additive masterbatches in general carry 40 to 65 wt% of active content and are let down at 1 to 5 % of the base polymer, and the same arithmetic governs every concentrate described on additive masterbatch. Our source library holds no verified let-down percentage specific to antiblock concentrates, so the calculation below starts from the concentrate datasheet rather than from a rule of thumb.

Worked example (arithmetic only). To reach 5,000 ppm, that is 0.5 wt%, of antiblock in the film from a concentrate containing 20 % antiblock, add 2.5 % masterbatch: 0.5 divided by 20 equals 0.025, which is 2.5 %, or a let-down ratio of 39:1. The 20 % concentration here is illustrative, not a product value, and any real calculation uses the antiblock content printed on the concentrate datasheet.

Two checks belong with that arithmetic. Confirm the concentrate's active content rather than assuming it, and confirm that the carrier resin is compatible with the film resin. Any concentrate can be checked with the let-down ratio calculator.

How Do Antiblock Additives Interact with Slip, Antistatic and Processing Additives?#

Antiblock additives interact with 3 documented additive classes: they adsorb slip agents, they adsorb antistatic agents, and they take up antioxidants and HALS on acidic mineral surfaces. All 3 interactions run through the same property, the high specific surface area of a porous or acidic mineral, which is 5 to 100 m2/g for precipitated silica. Nothing is consumed chemically. The additive is held at the particle instead of reaching the film surface, so the symptom is a delayed or missing effect rather than a degraded molecule.

Table T4. Antiblock interactions in film.

The one interaction that works in the formulator's favour is the friction synergy: a polypropylene study recorded in our source library under PMC10458392 found that erucamide and silica together lower the coefficient of friction more than either does alone, even though the silica adsorbs part of the amide. The other 3 rows cost performance and have to be paid for in the recipe. A full matrix of these effects across additive families is on additive interactions.

Why does slip performance drop when silica antiblock is added?#

Slip performance drops when silica antiblock is added because the porous silica adsorbs part of the erucamide or oleamide and slows its migration to the surface, so the film reaches its target coefficient of friction later or not at all. The amide has to leave the bulk, cross to the surface and form a continuous layer there, and any of it held on a 5 to 100 m2/g mineral surface is not doing that work. Two other causes produce the same symptom and are worth excluding first: insufficient bloom time, since erucamide needs 24 to 48 hours for most of its effect and 7 to 10 days for its final value, and a change in film gauge, since the same concentration gives a different surface loading at a different thickness. The bloom kinetics behind that timing are covered in slip agent migration and COF development.

Three fixes apply, in the order a plant should try them.

• Wait out the bloom and re-measure. Test the coefficient of friction at a fixed age rather than straight off the winder.
• Switch to a slow-bloom amide or re-set the slip level to match the antiblock type and loading actually in the film.
• Adjust the slip level with film gauge, lowering concentration as the film thickens for the same target friction.

Other coefficient-of-friction faults and their causes are collected under troubleshooting additive-related defects.

How Is Antiblock Performance Tested?#

Antiblock performance is tested with 4 methods: the blocking load under ASTM D3354, the coefficient of friction under ASTM D1894, haze under ASTM D1003 and ash content under ASTM D5630 to confirm the mineral level in the film. The first measures the property the additive exists for, the second and third measure what it costs, and the fourth confirms that the dose the recipe called for is the dose that reached the film. All 4 methods are indexed under testing plastic additives.

Table T5. Test methods for antiblock film.

How Are Antiblock Additives Regulated for Food-Contact Film?#

The common antiblock minerals are authorised for food-contact plastics in both major markets: each type has an EU Union list entry without a specific migration limit, and the US lists silica, diatomaceous earth, talc and calcium carbonate in 21 CFR 178.3297. That is the whole of the picture for the mineral types; the organic types carry entries of their own, one of them with a residual-monomer restriction. Every instrument behind these entries is summarised in plastic additive regulations.

Two REACH points complete the EU position. Natural minerals that are not chemically modified, which covers natural diatomaceous earth and nepheline syenite, are generally exempt from registration under REACH Annex V, while synthetic amorphous silica and soda ash flux-calcined diatomite are registered substances with active dossiers. None of the antiblock substances on this page is on the REACH Candidate List, checked on 22 September 2026.

Food-contact status is a per-market screen, not a global one, and it applies to the slip, antifog and antistat additives in the same structure as much as to the antiblock. The full food-contact film stack is on additives for food packaging.

EU: Union list entries under Regulation (EU) No 10/2011#

All 5 antiblock types appear on the Union list of Regulation (EU) No 10/2011 without a substance-specific migration limit, so the generic limit of 60 mg/kg and the overall migration limit of 10 mg/dm2 apply instead. The values below are verified against the Union list as consolidated on 16 March 2025.

Table T6a. Union list entries for antiblock substances.

An entry without a specific migration limit does not mean an unlimited level. The generic specific migration limit of 60 mg/kg food and the overall migration limit of 10 mg/dm2 still bind the finished article, and the declaration of compliance has to name every FCM number in the structure. How the Union list works, and what an authorisation covers, is explained on EU 10/2011.

US: 21 CFR 178.3297 and 178.3860#

In the US the antiblock minerals silica, diatomaceous earth, talc and calcium carbonate are listed in 21 CFR 178.3297, the section for colorants in food-contact polymers, while saturated fatty amides such as stearamide fall under 21 CFR 178.3860 for release agents. Section 178.3297 also covers mica, China clay, bentonite, barium sulfate and calcium silicate, and it limits the use level of these minerals to the amount needed for the colouring effect, which makes it a listing route rather than a dosage clearance for the antiblock function. Calcium carbonate carries a second route as a GRAS substance under 21 CFR 184.1191.

Two cautions belong with these citations. Methylsilsesquioxane and nepheline syenite are not found in the sections we checked, which is not the same as being disallowed, and no substance on this page is "FDA approved": the correct phrasing is that it is listed in a named section under stated conditions of use. One further distinction matters for slip pairing: 21 CFR 178.3860 covers erucamide, oleyl palmitamide, stearyl erucamide and saturated fatty acid amides, and oleamide is not among them. Every 21 CFR section relevant to plastic additives is mapped on FDA food contact rules.

Who Makes Antiblock Additives? Mineral Producers and Masterbatch Suppliers#

Antiblock additives come from 2 supplier groups: mineral producers such as Imerys, Evonik and Covia, which make the diatomaceous earth, silica, talc and nepheline syenite, and masterbatch makers such as Ampacet, Avient and Tosaf, which sell those minerals as film concentrates. Film converters buy almost entirely from the second group, while compounders and concentrate makers buy from the first. Company profiles across both groups are in the directory of plastic additive manufacturers and suppliers.

Table T7. Producers by antiblock type.

For the mineral side of the chain, see mineral filler suppliers.

Prices are published for the minerals, not for the antiblock function. The USGS Mineral Commodity Summaries 2025 put world diatomite mine production at 3.0 million t in 2024, with the US at 29 %, Denmark at 18 % and China at 12 %, and the US average price at USD 590/t f.o.b. plant, with filtration grade at about USD 790/t; milled talc averaged USD 330/t ex-works in the same year. Synthetic silica prices for plastics are tracked separately on silica price for plastics, because they follow a chemical cost structure rather than a mining one.

No reliable published figure exists for the size of the antiblock additive segment on its own, and this page states none; segment data at the level of the whole additives industry are on plastic additives market. For the buying step itself, concentrate makers are compared on masterbatch manufacturers, where the selection criteria are carrier resin, active content and film-grade cleanliness rather than the mineral itself.

Complete List of Antiblock Additive Substances (8 Pages)#

The table lists the 8 antiblock substances with their own pages on this site, with CAS number, antiblock type, film function, main polymers and EU food-contact entry. Rows follow the same type order used throughout this page.

Table T8. Antiblock substances on PlasticAdditives.net.

Every other substance used in plastics, with its CAS number, function, dosage and regulatory status, is in the plastic additives database.

Are Antiblock Minerals Hazardous? Dust, Crystalline Silica and Recycling#

The main hazard of antiblock minerals is respirable dust during handling, not the particles bound in the finished film, and it concentrates in the grades that contain crystalline silica, such as calcined diatomaceous earth. Powder handling, concentrate compounding and bag emptying are where exposure controls apply; once the mineral is dispersed in a polymer matrix it is bound in the article. Three questions come up repeatedly in specification reviews, and each has a documented answer: the crystalline silica status of diatomaceous earth, the classification status of talc, and the effect of mineral antiblock on film recycling.

Is diatomaceous earth antiblock a crystalline silica hazard?#

Calcined diatomaceous earth can be a crystalline silica hazard, because our source library records that calcined grades contain crystalline silica, so the safety data sheet of each grade decides. Where crystalline silica is present, the occupational limits apply: the EU binding limit value for respirable crystalline silica is 0.1 mg/m3 under Directive (EU) 2017/2398, and the OSHA permissible exposure limit is 50 µg/m3 as an 8-hour time-weighted average with an action level of 25 µg/m3 under 29 CFR 1910.1053. Respirable crystalline silica has been on the California Proposition 65 list since 1 October 1988.

Two practical consequences follow. Check the safety data sheet for cristobalite content before specifying a calcined grade, and note that amorphous silica, including the synthetic precipitated grades, is not on the Proposition 65 list.

What is the classification status of talc?#

Talc has no harmonised EU hazard classification in force as of the CLP consolidation of 1 July 2026, while the International Agency for Research on Cancer placed talc not containing asbestos in Group 2A in July 2024. IARC classifies talc containing asbestos in Group 1, a separate entry. In California, Proposition 65 lists only talc containing asbestiform fibers, listed on 1 April 1990, and asbestos-free talc is not listed. Most GHS notifications for talc report no classification: 4,523 of 4,758 notifications record that it does not meet the criteria. The IARC decision sits in Monographs volume 136 and applies to talc as a substance rather than to talc bound in a plastic film.

Do antiblock additives affect film recycling?#

The design guidance of the Association of Plastic Recyclers lists slip and antiblock among the Preferred additives for PE film while asking that they be minimized, and it calls for testing once film density approaches 0.996 g/cm3. Density is the mechanism: above 1.00 g/cm3 a PE film sinks in the float-sink separation step and counts as non-recyclable. Every mineral antiblock is denser than the polymer, at 2 to 2.5 g/cm3 for diatomaceous earth, 2.7 to 2.8 g/cm3 for talc and 2.7 to 2.95 g/cm3 for calcium carbonate, so the arithmetic matters most where a high-loading mineral meets a thin film.

At the ppm levels in the dosage table the density contribution is small, but it adds to the contribution of every other filler in the structure, which is why the guidance sets a test threshold rather than a ban. How each additive family affects the recycling route is set out in design for recycling.

Antiblock additive FAQs#

Three questions dominate the search results for this topic, and two of them exist because the trade vocabulary is used loosely.

Is an antiblock additive the same as an anti-slip agent?#

No. An antiblock additive stops film layers sticking by roughening the surface with insoluble particles, while "anti-slip" is used inconsistently in the trade and is sometimes even applied to slip agents, the migrating amides that lower the coefficient of friction measured under ASTM D1894. The two functions are opposite in mechanism and are dosed independently.

Does antiblock reduce film clarity?#

Yes. Antiblock particles scatter light and add haze, which is the cost side of the trade-off, and the loss is smallest when the refractive index of the particle sits close to that of the polymer, as it does for diatomaceous earth in polyethylene. Haze is quantified under ASTM D1003-21, and a film above 30 % haze counts as diffusing.

Is nepheline syenite free of crystalline silica?#

Yes. Nepheline syenite is a quartz-free mineral, and the MINEX grades of Covia contain less than 0.1 % crystalline silica. That is the property that distinguishes it from calcined diatomaceous earth grades in a handling risk assessment.