How to Select Plastic Additives: A Step-by-Step Framework

Plastic additive selection runs through 7 steps: define the property gap, identify the host polymer, check the processing temperature, define the end-use environment, screen the regulatory status, check the interactions with the rest of the package, then set the dosage, the cost in use and the test plan. The steps run in that order because each one removes candidates that the next one can no longer recover, and a formulator who reverses two of them pays for it in a failed trial. The global market moves 36.7 Mt of additives a year (Ceresana, 2023 data), spread across 43 families, so the first job of any selection method is elimination rather than search.

Elimination works because the constraints are hard numbers. Engineering polymers process at 240 to 320 °C, which rules out aluminium trihydrate, since ATH releases its water from about 200 °C. Food contact in the European Union rules out every substance absent from the Union list of Regulation (EU) No 10/2011. A single antagonism, thioester plus hindered amine light stabilizer, cancels a package that looked correct on paper. Which constraint bites first?

The host polymer decides that, and this page works through the 7 steps in their binding order: how to state a property gap as a measurable number, how the polymer and its grade narrow the family list, how the processing window excludes decomposition-limited chemistries, how outdoor, food, fire and electrical end uses add their own gates, how to screen REACH, the POPs Regulation, Regulation (EU) No 10/2011, 21 CFR, RoHS and California Proposition 65 in one pass, which additive pairs work together and which cancel, and how to set a dosage in phr or wt%, cost it per kilogram and per litre, and confirm it by test. Selection is part of plastic formulation as a whole, and the same 7 steps apply to every one of the 43 additive families catalogued on this site.

The table below summarises the 7 steps, the single question each one answers and the output each one produces before the next step starts.

What Is Plastic Additive Selection?#

Plastic additive selection is the formulation decision that matches a measurable property gap in a polymer to an additive family, a specific grade, a dosage and a delivery form, under the constraints set by the host polymer, the process, the end use and the regulations of every target market. Selection is therefore a constrained search, not a product comparison: the constraints come first, and the candidate list is what survives them. How large is the starting list? The reference covers 43 additive families and 437 named substances and grades, of which a typical compound uses between 3 and 12.

Every commercial plastic carries a package rather than a single additive. The polymer supplies the mechanical and thermal backbone, and the additives supply everything the backbone lacks: thermal survival through the extruder, service life outdoors, fire performance, colour, surface behaviour and cost. Selection assigns one family to each of those gaps, then reconciles the choices with each other. The full catalogue of families sits on the plastic additives reference page, and each family page carries the dosage bands and grade lists that steps 6 and 7 of this framework depend on.

Why does additive selection fail more often than additive chemistry?#

Additive selection fails more often than additive chemistry because the chemistry is usually correct in isolation and wrong in context. A phenolic antioxidant does stop autoxidation, and it still yellows a white part when nitrogen oxides reach it. Aluminium trihydrate does suppress flame, and it still decomposes in a polyamide at 280 °C. The failure is a context error, not a mechanism error.

Three context errors account for most failed trials. The first is a symptom-level property gap: a formulator specifies an impact modifier when the impact loss comes from thermo-oxidative chain scission during regrind, which an antioxidant fixes at one tenth of the cost. The second is an unchecked interaction, where a correct additive is added to a package that neutralises it. The third is a regulatory exclusion discovered after the trial, which invalidates the data rather than the chemistry.

Each of those errors has a step in the framework that catches it. Step 1 catches symptom-level gaps by forcing a measurable target. Step 6 catches interactions by reviewing the whole package. Step 5 catches regulatory exclusions before a trial is booked, which is the reason it sits ahead of the interaction check and not after it. Defects that survive all 7 steps belong to the compounding line rather than the recipe, and they are diagnosed under troubleshooting additive-related defects.

Which 6 decisions does one additive selection make?#

One additive selection makes 6 decisions: the family, the chemical class inside that family, the specific grade, the dosage, the delivery form and the supplier. Each decision narrows the one below it, and a decision taken out of order forces rework. The 6 decisions are listed below in the order the framework resolves them.

1. Family. The functional class that closes the property gap, such as antioxidants, UV stabilizers, flame retardants, plasticizers, fillers or impact modifiers.
2. Chemical class. The sub-type inside the family, such as hindered phenol against phosphite inside antioxidants, or hindered amine against benzotriazole inside light stabilizers.
3. Grade. The named commercial product, defined by molecular weight, melting point, particle size, surface treatment and purity.
4. Dosage. The loading in phr for PVC and rubber, or in wt% or ppm for polyolefins and engineering plastics.
5. Delivery form. Powder, free-flowing powder, dust-free granules, pastilles, prills, liquid or masterbatch.
6. Supplier. The manufacturer or distributor, with the documentation, the capacity and the regulatory dossier the application needs.

Family and class are technical decisions, grade and dosage are performance decisions, and form and supplier are operational decisions. Splitting them this way prevents the most common shortcut, in which a familiar grade is carried into a new project before anyone has restated the property gap.

The 7-Step Plastic Additive Selection Framework#

Select plastic additives in 7 steps: define the property gap, identify the host polymer and its grade, check the processing method and temperature, define the end-use environment, screen the regulatory status in every target market, check interactions with the rest of the package, then set the dosage, the cost in use and the test plan. The order is not arbitrary. Steps 1 and 2 build the candidate list, steps 3 to 6 remove candidates, and step 7 converts the survivors into a recipe that can be tested. Reversing steps 5 and 7 is the single most expensive mistake, because it puts regulatory screening after the trial data exist.

The 7 steps are worked through individually below. Each step states its input, the decision it makes and the evidence that closes it.

Step 1: Define the Property Gap#

Define the property gap as a measured current value, a target value and the test method that produces both. A gap written as "the part is too brittle" cannot be closed by any additive, while a gap written as "notched Izod impact is 22 J/m and the specification requires 60 J/m by ASTM D256 at 23 °C" selects a family on its own. The unit and the method belong in the statement, because the same property measured by two methods gives two different numbers.

Which cause produced the gap? That question separates the two families that can close it. A high-impact polystyrene at 5 % rubber reaches 40 J/m notched impact, and the same polymer at 15 % rubber reaches 166.2 J/m, so a rubber-phase change is one route. Impact loss caused instead by melt-flow-rate drift over five extrusion passes is oxidative chain scission, and the correct family is an antioxidant, not an impact modifier. Property gaps are therefore written twice: once as the measured shortfall, once as the mechanism behind it.

Four gap statements from real specifications show the pattern. Polyethylene pressure pipe compound requires an oxidative induction time of at least 20 minutes at 210 °C under EN 12201-1 and ISO 4427-1. A PVC cable insulation requires a limiting oxygen index of at least 26 vol % O2. An unattended household appliance part under IEC 60335-1 clause 30.2.3 requires a glow-wire flammability index of at least 850 °C and a glow-wire ignition temperature of at least 775 °C. A clarified polypropylene requires haze below the level a nucleating agent alone can reach, which moves the choice from nucleating agents to clarifiers.

Step 2: Identify the Host Polymer and Its Grade#

Identify the host polymer, its grade and the additive package it already carries, because the polymer decides which families are standard, which are optional and which are chemically pointless. Polyvinyl chloride cannot be melt-processed at all without a heat stabilizer, since it starts losing hydrogen chloride at 100 to 120 °C and degrades rapidly near 250 °C. Polyethylene stays thermally stable to about 400 °C and needs no chlorine-scavenging stabilizer of any kind. The same words therefore name different products in different polymers.

Grade matters as much as polymer type. A polypropylene homopolymer and a polypropylene block copolymer take different Piringer diffusion constants in migration modelling, 13.1 and 11.5 respectively with activation-energy terms of 1577 K and 0 K (JRC EUR 27529, 2015), so the same additive migrates at different rates from the two grades. Reactor grades already contain a base stabilization package, typically a hindered phenol with a phosphite and an acid scavenger, and adding a second phenol to that package buys far less than adding the missing function.

Base packages by polymer are compared further down this page, and the full formulation guides sit under additives by polymer. Three polymer facts change a selection immediately: chlorine content, which creates acid; ester, amide or carbonate links, which create hydrolysis sensitivity; and tertiary carbons, which create oxidation sensitivity. Polypropylene oxidises at its tertiary carbon and loses molecular weight through beta-scission, so its melt flow rate rises; polyethylene crosslinks instead and forms gels. One mechanism needs melt-flow protection, the other needs gel control, and the two lead to different antioxidant ratios.

Step 3: Check the Processing Method and Temperature#

Check the melt temperature, the shear history and the residence time, then delete every candidate that decomposes, volatilises or reacts inside that window. Plastics process between 150 and 320 °C, and the upper end of that range excludes whole chemistries. Engineering polymers such as PA66, PBT, PET and polycarbonate run at roughly 240 to 320 °C, and PEEK runs above 340 °C, which leaves only highly stable additives in the candidate list.

Decomposition temperature is the hard gate. Aluminium trihydrate releases its water of hydration from about 200 °C, absorbing 1051 J/g as it does so, which is exactly the mechanism that makes it a flame retardant and exactly the reason it cannot be compounded into a polyamide. Magnesium hydroxide replaces it where the process runs hotter. Volatility sets the second gate: butylated hydroxytoluene at a molar mass of 220 g/mol is volatile enough that most polyolefin formulators replaced it with Irganox 1010 at 1178 g/mol, which shows 5 % mass loss by thermogravimetry only at 330 to 353 °C.

Process type changes the answer as much as temperature does. The 4 process constraints that most often force a grade change are listed below.

• Residence time. Rotomoulding holds polyethylene in a 300 °C oven to an internal air end point of 180 °C for 1 to 2 cycles per hour, which demands far more thermal reserve than film extrusion at the same melt temperature.
• Shear. A co-rotating twin-screw compounder disperses agglomerates that a single-screw extruder leaves intact, so a fine-particle filler that works after compounding fails when it is dry-blended.
• Dosing accuracy. Additives dosed at parts per million need gravimetric loss-in-weight feeders or delivery as a masterbatch, because volumetric feeding cannot hold a 150 ppm clarifier level.
• Multiple heat histories. Recyclate carries the thermal history of its first life, so its stabilizer demand is set by what the first life consumed, not by the virgin specification.

The equipment side of these constraints belongs to plastic compounding, where screw design, side feeding and strand cooling decide whether a correctly selected additive is correctly dispersed.

Step 4: Define the End-Use Environment#

Define the end-use environment as 5 variables: service temperature, exposure to light and weather, contact with food, drinking water or the body, fire performance requirement and electrical duty. Each variable maps onto a standard with a number, and the number is what selects the grade. An outdoor part exposed for 25 years and an indoor part exposed for 2 years share a polymer and share almost nothing else in their light-stabilizer package.

Light exposure is the clearest case. Polyolefins absorb only below 250 nm, so photo-oxidation starts at impurities and chromophores rather than at the polymer itself, while polyethylene terephthalate absorbs from 360 nm and degrades directly. About 70 % of all light stabilizers go into polyolefins for that reason. Outdoor polyethylene pipe uses carbon black at 2.0 to 2.5 wt% with a primary particle size of 10 to 25 nm under EN 12201-1, and geomembranes under GRI-GM13 Revision 16 of 17 March 2021 use 2.0 to 3.0 %. Those two numbers are not interchangeable, and writing "2 to 3 %" for pipe is a specification error.

Fire duty selects by rating rather than by family. The UL 94 flammability ratings define V-0 as an afterflame of 10 seconds or less per application, 50 seconds or less in total for 5 specimens, and no ignition of the cotton indicator, always stated with the specimen thickness. Reaching V-0 in polypropylene takes 22 to 30 wt% of an intumescent ammonium polyphosphate system, while a glass-filled polyamide reaches V-0 at 0.4 to 3.2 mm with a metal phosphinate system at far lower loading. Electrical duty adds its own numbers: a comparative tracking index of up to 600 V under IEC 60112, and the glow-wire pair already named in step 1.

Food contact and drinking-water contact convert the environment into a legal question rather than a performance question, which is what step 5 resolves. Application-level packages are collected under plastic additives by application, from packaging film to wire and cable.

Step 5: Screen the Regulatory Status in Every Target Market#

Screen every candidate against the rules of every market the article is sold in, before any trial is booked, because a restriction invalidates trial data rather than merely delaying it. Screening runs through 8 gates in the European Union and the United States: REACH registration, the SVHC Candidate List, REACH Annex XIV, REACH Annex XVII, the POPs Regulation, the food-contact Union list of Regulation (EU) No 10/2011, the relevant sections of 21 CFR, and, where electrical or Californian markets apply, RoHS and California Proposition 65.

Registration is the first gate and the one most often missed. Polymers are exempt from REACH registration under Article 2(9) of Regulation (EC) No 1907/2006, and additives are not: an additive is a substance and must be registered at 1 tonne per year or more per manufacturer or importer, including when it is imported inside a masterbatch, because a masterbatch is a mixture. An importer who buys a finished masterbatch abroad therefore inherits a registration question that a domestic compounder does not have.

The Candidate List gate triggers duties rather than a ban. The list held 253 entries on 22 September 2026, last updated on 4 February 2026 with n-hexane and bisphenol AF and its salts. Inclusion above 0.1 % by weight in an article triggers Article 33 communication to recipients immediately, Article 7(2) notification to ECHA within 6 months where the actor also exceeds 1 tonne per year, and a SCIP database entry under the Waste Framework Directive. The Court of Justice confirmed in case C-106/14 of 10 September 2015 that the 0.1 % applies to each component article of a complex product, which is why a 0.1 % calculation done on total product weight understates the result.

Restriction and listing gates are absolute. REACH Annex XVII entry 51 limits DEHP, DBP, BBP and DIBP to 0.1 % by weight of plasticised material in all articles since 7 July 2020, while entry 52 limits DINP, DIDP and DNOP to 0.1 % only in toys and childcare articles that can be placed in the mouth, so DINP is not banned in the EU. Entry 63, introduced by Regulation (EU) 2023/923, sets lead in PVC articles below 0.1 % from 29 November 2024, with recovered rigid PVC allowed up to 1.5 % in listed building uses until 28 May 2033. Under Regulation (EU) 2019/1021, UV-328 became the first non-halogenated plastic additive listed in Stockholm Annex A, by decision SC-11/11 in 2023, and its EU limit falls from 100 mg/kg since 4 August 2025 to 10 mg/kg in 2027 and 1 mg/kg in 2029. The step-by-step screen against these instruments is set out under plastic additive regulations, and each substance record in the plastic additive substance database carries its own status.

Step 6: Check Interactions With the Rest of the Package#

Check every candidate against the additives already in the formulation, because additive packages contain both synergies that reduce the required dosage and antagonisms that cancel it. A hindered phenol with a phosphite is the standard processing pair, since the phosphite decomposes hydroperoxides and its transesterification releases a primary antioxidant. A thioester with a hindered amine light stabilizer is the standard antagonism, since acidic sulfur products protonate and deactivate the basic HALS.

Acidity is the most general antagonism mechanism. Hindered amine light stabilizers are neutralised by hydrogen chloride in PVC unless NOR-HALS grades are used, they are neutralised by halogenated flame retardants, and they are neutralised by sulfur-containing pesticides in agricultural film, where 1,000 to 2,000 ppm of sulfur cuts greenhouse-film life by 20 to 25 %. Flame retardants reduce antioxidant effectiveness by the same route. Any formulation that combines a light stabilizer with an acid source therefore needs a stabilizer class chosen for acid tolerance rather than for peak efficiency.

Adsorption is the second mechanism and it is physical rather than chemical. Talc, kaolin and silica carry acid surface sites that adsorb antioxidants and HALS, so a talc-filled polypropylene needs a stronger stabilizer package than the unfilled grade at the same service temperature. Silica antiblock adsorbs erucamide and amine antistats in the same way, which is why a film that gains an antiblock often loses its coefficient-of-friction target at unchanged slip dosage. Low-surface-treatment titanium dioxide with a phenolic antioxidant produces pink titanium-quinone complexes, and phthalocyanine pigments nucleate polypropylene and change mould shrinkage from 13.6 to 22.3 %, turning a colour decision into a dimensional one. The complete pairing matrix is set out under additive interactions.

Step 7: Set the Dosage, Cost in Use and Test Plan#

Set the dosage in the unit the polymer uses, convert it to cost per kilogram and per litre of compound, and name the test that will accept or reject the trial. Dosage units are not interchangeable: phr counts parts per hundred parts of resin, so the polymer is always 100 and the total exceeds 100, while wt% is calculated as the phr of the ingredient divided by the sum of all phr, multiplied by 100. A PVC pressure-pipe recipe under PPI TR-2-2023 totals 108.03 phr, which makes 5.00 phr of calcium carbonate equal to 4.63 wt%.

Dosage bands span four orders of magnitude, and knowing the band prevents the most common overdose. Clarifiers run at 150 to 200 ppm for a grade such as Irgaclear XT 386, acid scavengers up to 1000 ppm and slip agents at 500 to 1200 ppm; stabilizers run at 0.05 to 1 %; PVC stabilizers, lubricants and impact modifiers run at 1 to 10 phr; plasticizers, fillers and mineral flame retardants run at 10 to 70 %. Hahladakis and co-workers at the University of Manchester published the composition ranges behind those bands in the Journal of Hazardous Materials in 2018, and Chea and co-workers reproduced them in 2025: plasticizers 10 to 70 wt%, flame retardants 2 to 28 wt%, antioxidants 0.05 to 3 wt%, UV stabilizers 0.05 to 10 wt%, heat stabilizers 0.05 to 3 wt%.

Cost in use is calculated per kilogram and per litre, and the two answers differ. Cost per kilogram of compound is the sum of each ingredient's weight fraction multiplied by its price, and cost per litre is that figure multiplied by the compound density. Mineral fillers lower the cost per kilogram and raise the density at the same time, so the cost per unit volume falls far less than the cost per unit mass, and a part sold by volume captures less of the saving than the raw-material calculation suggests. The unit conversions behind both figures are worked through under PHR (parts per hundred resin), and the PHR to weight percent calculator performs them directly.

The test plan closes the step. Every property gap from step 1 has a standard method attached to it, so the acceptance criterion is written before the trial rather than after the results: oxidative induction time by ASTM D3895-19 or ISO 11357-6, melt flow rate by ISO 1133-1 or ASTM D1238, limiting oxygen index by ASTM D2863-23e1 or ISO 4589-2, yellowness index by ASTM E313-20, and accelerated weathering by ISO 4892-2 or ASTM G155-25. A trial without a pre-agreed criterion produces data that the project then argues about.

Which Additive Family Solves Which Property Gap?#

Each property gap maps to a primary additive family and, in most cases, to one alternative family that closes the same gap by a different mechanism. Choosing between the two is a step 3 to step 6 decision, because the primary family is usually cheaper and the alternative usually survives a harder process or a stricter regulation. The table below maps 16 common property gaps to their families, their typical dosage bands and the polymers where each family is standard practice.

Colour is the one gap that is decided outside this table, because it is specified rather than calculated, and colorants for plastics covers pigment class, heat stability and the nucleation side effects noted in step 6. Molecular weight loss in condensation polymers is the other exception, since it is repaired by chain extenders for polymers at 0.1 to 0.5 wt% of a Joncryl ADR type and prevented by hydrolysis stabilizers, which act on a mechanism no stabilizer in the table addresses.

Which Additives Does Each Polymer Need?#

Each polymer carries a mandatory base package set by its degradation chemistry, plus optional families set by the application. The mandatory part is not negotiable: it exists because the polymer cannot be processed or cannot survive service without it. The optional part is where selection does its work. The table below states the base package for 7 polymer families and the families most often added to it.

Polyvinyl chloride is the extreme case, with about 70 % of EU PVC volume going into building and construction and a compound that regularly carries 6 or more families at once. The full recipes sit under additives for PVC and additives for polypropylene, with additives for polyethylene and additives for nylon covering the other two highest-volume cases.

Recyclate changes the base package rather than the optional part. Post-consumer and post-industrial polyolefins arrive with a partly consumed stabilizer system, a mixed thermal history and contamination from adjacent streams, where 5 % of polypropylene in recycled HDPE cuts slow crack growth resistance by up to 40 %. Restabilization rather than topping up is the accepted answer, and it is treated below the contextual border and in full under additives for recycled plastics.

How Does Processing Temperature Exclude Additives?#

Processing temperature excludes an additive when the melt temperature reaches the additive's decomposition or volatilisation point, which happens most often between 200 and 320 °C. Exclusion is absolute rather than gradual: an additive that decomposes inside the barrel does not underperform, it produces gas, odour, colour and, in the case of hydrated mineral flame retardants, foam. Thermogravimetry at 10 °C per minute under nitrogen is the standard screen, reported as the temperature of 5 % mass loss.

Four temperature bands cover most commercial processing, and each band deletes a different set of candidates. Below 200 °C, wood-plastic composites cap out because cellulose degrades, and the process runs at least 28 °C below the unfilled resin. Between 200 and 240 °C, polyolefins run comfortably and hydrated mineral flame retardants are already marginal. Between 240 and 320 °C, engineering polymers exclude ATH, most ammonium polyphosphate grades, low-molar-mass phenolics and amine-based stabilizers. Above 340 °C, PEEK admits only the most stable additives.

Volatility and extraction set a second limit that temperature alone does not capture. Higher molar mass lowers both volatility and the diffusion coefficient, which is why Irganox 1010 at 1178 g/mol displaced BHT at 220 g/mol in most polyolefin packages. Solubility data make the same point for extraction: a SONGNOX 1010 grade dissolves below 0.05 g per 100 g in squalane and below 0.1 g per 100 g in n-hexane, while SONGNOX 1680 dissolves at 10.0 g per 100 g in n-hexane and is therefore far easier to extract. Physical loss during service is covered under additive volatility, extraction and fogging.

Temperature also decides the delivery form. Additives dosed below 1000 ppm reach the melt reliably only through a masterbatch or a one-pack, because a gravimetric feeder at that level runs at the edge of its accuracy, and masterbatch carriers are themselves selected for compatibility with the host polymer at the processing temperature.

How Do You Screen a Plastic Additive for Regulatory Compliance?#

Screen a plastic additive market by market and use by use, because the same substance can be permitted in one application and restricted in another within the same jurisdiction. DEHP illustrates the split: it is restricted to 0.1 % in plasticised material in all articles under REACH Annex XVII entry 51, it carries a specific migration limit of 0.6 mg/kg in food contact under Regulation (EU) 2023/1442, and it holds a separate medical-device authorisation with a latest application date of 1 January 2029 and a sunset date of 1 July 2030 under Regulation (EU) 2023/2482. One substance, three different answers.

Screening is quickest as a fixed sequence, because the gates that exclude most candidates come first. The 8 gates below are worked in order, and each one is answered yes or no before the next is opened.

1. Check REACH registration. Confirm the substance is registered for the tonnage and the use, including inside any imported masterbatch.
2. Check the SVHC Candidate List. Confirm whether the substance is among the 253 entries as of 4 February 2026, and whether the article will exceed 0.1 % by weight.
3. Check REACH Annex XIV. Confirm whether the substance is on the Authorisation List, with 59 entries, and note its latest application and sunset dates.
4. Check REACH Annex XVII. Confirm whether a restriction entry covers this use, with entries numbered up to 83.
5. Check the POPs Regulation. Confirm whether Regulation (EU) 2019/1021 lists the substance, and at which concentration limit and date.
6. Check the food-contact rules. Confirm the Union list entry and SML under Regulation (EU) No 10/2011 for the EU, and the relevant 21 CFR section or effective food contact notification for the United States.
7. Check sector rules. Confirm RoHS for electrical equipment, the Toy Safety Regulation for toys, PPWR for packaging and the MDR for medical devices.
8. Check US state rules. Confirm California Proposition 65 listing and any state-level restriction for the article category.

The additive regulatory status checker runs the same sequence against the substance database, and each gate is documented in detail under REACH Annex XVII restrictions and the SVHC Candidate List.

Food-contact screening: EU 10/2011 and 21 CFR#

Food-contact screening asks whether the substance is on the authorised list for that jurisdiction, then whether the finished article stays inside the migration limits. In the European Union, Regulation (EU) No 10/2011 works from a Union list in Annex I, where each authorised monomer, additive or polymer production aid carries an FCM number and, where relevant, a specific migration limit. Substances that are not on the Union list are not permitted, and a substance without an SML falls under the generic limit of 60 mg/kg.

Two limits apply to every food-contact article regardless of the substance. The overall migration limit is 10 mg/dm² of contact surface, or 60 mg/kg for articles intended for infants and young children, under Article 12. The functional barrier rule of Articles 13 and 14 allows unlisted non-CMR substances behind a barrier only when they are not detectable at 0.01 mg/kg. Migration is measured against the Annex III simulants: A is 10 % ethanol, B is 3 % acetic acid for food below pH 4.5, C is 20 % ethanol, D1 is 50 % ethanol, D2 is vegetable oil and E is Tenax.

Phthalate limits changed with Regulation (EU) 2023/1442, in force since 1 August 2023, and the older figures are obsolete. The current values are 0.6 mg/kg for DEHP, 0.12 mg/kg for DBP, 6 mg/kg for BBP and 1.8 mg/kg for the DINP plus DIDP group restriction 26, with group restriction 36 set at 0.6 mg/kg expressed as DEHP equivalents. The European Food Safety Authority derived the basis of those numbers in 2019 as a group tolerable daily intake of 50 µg per kg of body weight per day in DEHP equivalents.

United States screening runs through a different instrument. There is no equivalent of the Union list, and an additive is cleared either by a 21 CFR listing with its stated conditions of use or by an effective food contact notification, which covers only the notifier named in it. Polyolefin articles are cleared under 21 CFR 177.1520 with extraction limits that vary by resin: polypropylene at 6.4 % maximum n-hexane extractables under reflux and 9.8 % xylene solubles at 25 °C, polyethylene at 5.5 % n-hexane extractables at 50 °C and 11.3 % xylene solubles. The correct phrasing is that a substance complies with the named section for the named polymer, never that it is FDA approved. FDA food contact rules and EU 10/2011 set out both systems, and both end in the same physical test, which is migration testing of plastics for food contact.

Restricted-substance screening: REACH, POPs, RoHS and US rules#

Restricted-substance screening asks whether a limit applies to this substance in this article category, and which date it starts. Restrictions differ from the Candidate List in kind: a Candidate List entry creates communication and notification duties, while an Annex XVII entry, a POPs listing or a RoHS limit prohibits the article above a stated concentration.

Five restriction regimes cover most plastic additives, and their limits are listed below with the instrument that sets each one.

• REACH Annex XVII. Entry 51 sets 0.1 % for DEHP, DBP, BBP and DIBP in plasticised material in all articles since 7 July 2020. Entry 63 sets lead in PVC below 0.1 % from 29 November 2024 under Regulation (EU) 2023/923. Entry 23 sets cadmium in listed plastics below 0.01 %.
• POPs Regulation (EU) 2019/1021. UV-328 falls to 10 mg/kg on 4 August 2027 and 1 mg/kg on 4 August 2029; Dechlorane Plus holds 1,000 mg/kg until 15 April 2028 and then 1 mg/kg; HBCDD stands at 100 mg/kg; the PBDE sum stands at 10 mg/kg.
• RoHS, Directive 2011/65/EU. Cadmium at 0.01 % and lead, mercury, hexavalent chromium, PBB, PBDE, DEHP, BBP, DBP and DIBP at 0.1 % per homogeneous material, with phthalates applying since 22 July 2019.
• PPWR, Regulation (EU) 2025/40. Applies from 12 August 2026, with a 100 mg/kg sum limit for lead, cadmium, mercury and hexavalent chromium, and PFAS in food-contact packaging at 25 ppb for any targeted PFAS, 250 ppb for the sum of targeted PFAS and 50 ppm total fluorine-based PFAS.
• United States. The CPSIA sets 0.1 % for 8 phthalates in children's toys and childcare articles; TSCA section 6(h) sets a 0.1 wt% unintentional-presence threshold for decaBDE and PIP (3:1); California Proposition 65 sets a no significant risk level of 146 µg per day for DINP.

Two traps recur in this screen. The first is treating the Candidate List as a ban, which it is not. The second is treating a proposal as law: the FDA action of 27 May 2026 on DEHP, DCHP, DIOP and DINP under docket FDA-2026-N-5776 is a proposal, the EPA final risk evaluations of 6 January 2026 found unreasonable risk to workers rather than to consumers, and the universal PFAS restriction in the EU remains at opinion stage, with the RAC final opinion of 2 March 2026 and a SEAC draft opinion of 10 March 2026. One outright ban does exist and is often forgotten: oxo-degradable plastic products have been prohibited on the EU market since 3 July 2021 under Article 5 of Directive (EU) 2019/904, which removes an entire additive class from consideration. The evidence behind that class is reviewed under biodegradation additives for plastics.

How Do Additive Interactions Change the Selection?#

Additive interactions change the selection by moving the effective dosage up or down, and in the antagonistic cases by removing a function the formulation was paying for. Synergies are exploited deliberately, because a pair at a combined 0.15 % often outperforms either component at 0.3 %. Antagonisms are avoided by substitution, by separating the additives into different layers, or by choosing a class that tolerates the interfering species.

The 12 interactions below are the ones that most often decide a selection. The mechanism column states why the effect occurs, which is what allows the pair to be replaced rather than simply dropped.

Gas fading is the interaction that most often surprises a formulator, because the second partner is not in the formulation at all. Phenolic antioxidants react with nitrogen oxides from ambient air, from gas heaters or from cardboard packaging, and the reaction products yellow a white or pastel part after it has left the factory. Phenol-free antioxidant masterbatches yellow less for that reason, which turns a warehouse complaint into an additive-class decision. Discoloration with 4 competing causes, phenolic over-oxidation, a titanium dioxide interaction, NOx gas fading and cardboard yellowing, is separated under troubleshooting additive-related defects, and the full pairing matrix sits under additive interactions.

How Do You Confirm an Additive Choice by Testing?#

Confirm an additive choice with the test that measures the property gap defined in step 1, run on compound produced by the intended process, not on a laboratory plaque made another way. Process route changes dispersion, dispersion changes performance, and a press-moulded plaque therefore overstates what an injection-moulded part delivers. The acceptance criterion is fixed before the trial, so the trial decides rather than opens a discussion.

Eight methods cover the confirmation work for most additive selections. The table names each one, what it proves and the value a common specification asks for.

Accelerated tests answer relative questions rather than absolute ones. Oxidative induction time under ASTM D3895 can read low for a volatile antioxidant that performs well in service, which the method itself notes, so a candidate is compared against a reference compound rather than against an absolute threshold wherever the specification allows. Migration performance follows the same logic: Otto Piringer's upper-bound diffusion model, published as JRC EUR 27529 in 2015 and validated at 95 % confidence by Begley and co-workers in 2005, is a screening tool under Annex V 2.2.3 of Regulation (EU) No 10/2011, while Article 18(3) requires a failure to be confirmed by testing. The mechanisms behind those numbers are set out under additive migration in plastics and polymer degradation, and the full method catalogue under testing plastic additives.

How Does Additive Selection Change for Recycled and Bio-Based Plastics?#

Additive selection for recycled and bio-based plastics starts from a different baseline: the material already contains additives, and the formulator does not know all of them. Virgin resin arrives with a declared package, while post-consumer recyclate arrives with a partly consumed stabilizer system, legacy additives from its first life and contamination from adjacent streams. Selection therefore begins with characterisation rather than with a property gap.

Legacy content is measurable and often large. Wiesinger and co-workers at ETH Zurich analysed 151 Swiss floorings in 2024 and found regulated chemicals above 0.1 wt% in 16 % of samples, mainly lead and DEHP, other ortho-phthalates above 0.1 wt% in 29 %, DEHP present in 19 % of samples at 0.003 to 20 wt%, and zinc, barium and tin in 96 %, 72 % and 58 % respectively. Those numbers are a regulatory input as much as a technical one, which is why step 5 of the framework runs on the recyclate itself and not only on the additives being added to it. This section sits below the contextual border of the page: the sections above answer how to select an additive, and the sections below answer what changes when the material, the delivery form or the supplier is unusual.

Restabilizing recycled polyolefins#

Restabilize recycled polyolefins with a fresh primary plus secondary antioxidant package rather than topping up whatever survived the first life. Post-consumer and post-industrial polyolefins are generally not topped up in practice, which is the gap that restabilization closes. Rudolf Pfaendner, formerly of Ciba and then at Fraunhofer LBF, developed the concept and reviewed 30 years of it in 2022.

Dosages are published and specific. Knoben and co-workers reported in 2025 that recycled polypropylene restabilizes at 500 ppm of primary antioxidant plus 1000 ppm of secondary antioxidant per cycle, and a binary blend in recycled PP or HDPE runs at 0.1 to 0.3 % in supplier practice. The effect is measurable as embrittlement time: recycled polypropylene held at 150 °C embrittles at about 25 days unstabilised and at 37 to 42 days with 0.15 to 0.4 wt% of a dedicated restabilization blend. Antioxidant also accumulates across closed loops, with Irgafos 168 rising from about 650 ppm after cycle 1 to more than 1200 ppm after cycle 5 at that dosing rate, so the package is designed for the loop rather than for a single pass.

Two further constraints apply to recyclate that never apply to virgin resin. Odour is one: zeolite at 4 wt% cut odour intensity by 45 % in published trials, and excluding the worst input categories cut volatile organic compound content by 56 %. Sorting is the other: near-infrared sorting struggles with black and strongly coloured plastics, so the Association of Plastic Recyclers asks for L greater than 40 and near-infrared reflectance above 10 %, which makes a colorant choice a recyclability decision. Both belong to how additives affect plastic recyclability.

Selecting additives for bio-based and compostable plastics#

Select additives for bio-based and compostable plastics against the certification the product claims, because a compostability claim restricts the additive list far more tightly than a bio-based claim does. Bio-based content is measured by radiocarbon under ASTM D6866 and says nothing about end of life. Biodegradability depends on chemical structure rather than on feedstock origin, so a bio-based polyethylene is not compostable and a fossil-based polyester can be.

EN 13432 sets the European compostability criteria: less than 10 % residue after 3 months of disintegration testing under EN 14045, at least 90 % biodegradation within 6 months, plus heavy-metal and ecotoxicity criteria. Every additive in the compound counts toward those criteria, which excludes most conventional heavy-metal-based stabilizers and constrains pigment choice. Polylactic acid additive practice is well documented at specific levels: acetyl tributyl citrate at a 15 wt% reference for plasticization, cardanol at 10 wt% reaching 472 % elongation, ethylene bis-stearamide at 1 % as a nucleating agent at 110 °C, zinc phenylphosphonate at 0.3 wt%, and a Joncryl ADR chain extender at 0.1 to 0.5 wt%.

Volume context keeps the decision in proportion. Global bioplastics capacity stood at 2.31 Mt in 2025 with a forecast of 4.69 Mt by 2030, against actual production of 1.67 Mt at 72 % utilisation, which is 0.5 % of the 431 Mt global plastics total, with packaging taking 41.3 % (European Bioplastics and nova-Institute, 2025). Additives chosen from renewable feedstocks are a separate question from compostability, and they are covered under bio-based plastic additives.

One-pack systems and masterbatch as delivery forms#

Choose between individual additives, a one-pack blend and a masterbatch on dosing accuracy, dust exposure and formulation control, not on unit price. Individual additives give full control and the lowest raw-material cost per kilogram of active substance. A one-pack blend gives a single stream with a fixed ratio, which removes weighing errors at the mixer. A masterbatch gives accurate dosing at parts-per-million levels and removes dust handling entirely.

Delivery forms are a commercial reality rather than a laboratory detail. Suppliers ship powder, free-flowing powder, dust-free granules, pastilles, flakes, prills and liquids, and Songwon codes them as PW, FF, DF, FG, SB, DW, CP, SL, LQ and GR. Phosphite antioxidants ship in aluminium-coated bags because they are moisture-sensitive, which is a storage constraint that survives the selection decision. Liquid colour is dosed by peristaltic pump, and ppm-level solid additives need gravimetric loss-in-weight feeders or a masterbatch route.

One-pack systems are standard in PVC, where a stabilizer and lubricant one-pack replaces 4 to 6 separately weighed ingredients, and they exist across polyolefin stabilization as blended antioxidant systems at defined ratios, such as the 1:1, 2:1, 3:1 and 4:1 primary-to-secondary ratios in a commercial binary blend series. The trade-off is transparency: a one-pack hides the individual dosages from the formulator, which matters when step 6 of the framework requires an interaction review. Both routes are compared under one-pack additive systems and additive product forms.

When does a masterbatch beat a direct powder addition?#

A masterbatch beats a direct powder addition whenever the target level is below about 1000 ppm, whenever the additive is dusty or hazardous to handle, and whenever the process has no gravimetric feeder. Masterbatch carries 40 to 65 wt% of active additive as a rule, with extremes from 15 to 80 wt%, and is let down at 1 to 5 % of the base polymer. A let-down of 25 kg per tonne equals 2.5 %, and 5 % is written equivalently as a 19:1 ratio.

Active content in the final part is the masterbatch concentration multiplied by the let-down. A 4 % antioxidant masterbatch at 2.5 % let-down delivers 1000 ppm of active antioxidant, and a 35 % carbon black masterbatch at 5 to 6.5 % let-down delivers 1.75 to 2.3 % carbon black, which is the standard route to the pipe specification named earlier. Masterbatch costs more per kilogram of active substance and less per failed batch, which is the calculation that decides it. The additive dosage and cost-in-use calculator runs both figures.

Which mistakes make an additive selection fail?#

Six mistakes account for most failed additive selections, and 5 of them are sequence errors rather than chemistry errors. Each is listed below with the step of the framework that prevents it, which is the fastest way to audit a selection that has already gone wrong.

• Treating a symptom as the property gap. Prevented by step 1, which requires a measured value, a target and a method.
• Carrying a grade across polymers. Prevented by step 2, since a PVC-specific stabilizer chemistry has no function in a polyolefin.
• Ignoring the decomposition temperature. Prevented by step 3, and visible as gas, odour or foam in the first trial.
• Specifying an indoor package for an outdoor part. Prevented by step 4, and visible only after 6 to 24 months of service.
• Running the regulatory screen after the trial. Prevented by step 5, which is the only step that invalidates completed work when it is skipped.
• Overdosing to buy safety margin. Prevented by steps 6 and 7, because excess additive blooms, plates out, raises cost and can lower performance.

Overdosing deserves its own note, because it looks conservative and behaves otherwise. An additive above its solubility at the use temperature is supersaturated once the part cools, and it diffuses to the surface at a rate set by its diffusion coefficient, as Nouman and co-workers described in Polymer Degradation and Stability in 2017. The result is chalking on stabilizers, exudation on plasticizers, plate-out on PVC tooling and a drifting coefficient of friction on film. The fixes are a higher-molar-mass or oligomeric grade, a better solubility-parameter match or simply a lower loading, and they are set out under blooming and exudation in plastics.

What to ask an additive supplier before the first trial#

Ask a supplier for 7 items before the first trial: the exact grade designation, the CAS number, the regulatory dossier for every target market, the recommended dosage range for this polymer, the delivery form, the documented interactions and a sample large enough for the intended process. A trade name alone is not an identification, because one substance can carry two or more trade names, and a trade name can cover a reaction mass rather than a single compound.

Grade-level identity prevents the most common documentation failure. A request written as "an antioxidant for recycled polypropylene" returns a different product from every supplier, while a request that names the chemical class, the dosage band, the processing temperature, the food-contact requirement and the target market returns comparable offers. Documentation to request with the sample includes the safety data sheet, the food-contact declaration where relevant, the REACH registration status and the specification sheet with melting point, particle size and volatility data.

Supplier structure matters at the sourcing stage. The plastic additives market is valued between USD 43.5 bn for 2023 by MarketsandMarkets and USD 63.71 bn for 2025 by Precedence Research, with scope definitions that differ between analysts, and volume estimated at 36.7 Mt for 2023 by Ceresana. Producers, distributors and masterbatch houses sell into that market with different minimum quantities and different technical support, which are listed under plastic additive manufacturers and suppliers, with price context under plastic additive prices. The plastic additive supplier finder collects quotes for a named substance, volume, polymer and country in one request.

Frequently asked questions about choosing plastic additives#

The 6 questions below are the ones asked most often about additive selection, each answered in one or two sentences. They compress the framework above into single answers for readers who arrive at one specific decision.

How do you choose the right additive for a plastic? Work the 7 steps in order: state the property gap as a number with a test method, identify the host polymer and its existing package, check the processing temperature, define the end-use environment, screen the regulations in every target market, check interactions, then set the dosage and the test plan.

Which additive fixes which property problem? Antioxidants fix processing and long-term thermal degradation, UV stabilizers fix outdoor ageing, heat stabilizers fix HCl release in PVC, plasticizers fix rigidity, impact modifiers fix brittleness, flame retardants fix fire ratings, fillers fix cost and stiffness, and slip, antiblock and antistatic agents fix surface behaviour.

How much additive does a plastic compound need? The band depends on the family: clarifiers and slip agents run at 150 to 1200 ppm, stabilizers at 0.05 to 1 %, PVC stabilizers, lubricants and impact modifiers at 1 to 10 phr, and plasticizers, fillers and mineral flame retardants at 10 to 70 %.

Can one additive be used in every polymer? No. Heat stabilizers of the PVC type act on hydrogen chloride and have no function in polyolefins, aluminium trihydrate decomposes above about 200 °C and cannot be used in engineering polymers at 240 to 320 °C, and standard HALS are deactivated by the acid present in PVC and in halogenated flame-retardant systems.

Which additives are not allowed in food-contact plastics? In the European Union, any substance absent from the Union list of Regulation (EU) No 10/2011 is not permitted, and listed substances carry specific migration limits such as 0.6 mg/kg for DEHP and 0.12 mg/kg for DBP under Regulation (EU) 2023/1442; in the United States, use is cleared through a 21 CFR listing with stated conditions or through an effective food contact notification.

Do two additives ever cancel each other out? Yes. Thioesters deactivate hindered amine light stabilizers through acidic sulfur products, acid sources including PVC and halogenated flame retardants protonate standard HALS, and talc, kaolin and silica adsorb antioxidants and HALS on their acid surface sites.

Selection questions that turn into defects after production belong to a different workflow, and they are handled under troubleshooting additive-related defects and under additive dosage levels in plastics, which lists the published band for every family on this site, while the additive finder by polymer and function narrows the 43 families to the ones that work in a named resin.