Organic Peroxides for Polymers: 5 Peroxide Classes, Half-Life and Dosage

Organic peroxides are compounds built around an oxygen-oxygen single bond (R-O-O-R') that splits into two free radicals on heating, which is what lets them crosslink polyethylene, EVA and POE, graft silanes and, in polypropylene, cut chains instead. Their whole behaviour in a compound is set by one property, the temperature at which they decompose fast enough to cure but slowly enough to survive the extruder; so which grade fits which process?

Peroxides sit at the reactive end of the plastic additives spectrum: they are meant to be consumed during processing, not to survive in the part. Where a heat stabilizer or a plasticizer stays inside the polymer for the life of the part, a crosslinking peroxide breaks apart on purpose during the cure, and only its decomposition fragments, gases such as methane and small molecules such as acetophenone, remain once the process finishes.

This page works through that behaviour in order: the radical mechanism itself, the 5 chemical classes suppliers sell, how half-life and SADT data decide which grade survives compounding and cures on schedule, how to convert phr of a 40 % formulation into active peroxide content, which grade goes into XLPE cable, PEX pipe, EVA and POE foam, photovoltaic encapsulant, controlled-rheology polypropylene and recycled polyolefins, what coagents and byproducts do to the result, how the degree of crosslinking is measured and targeted by standard, how the drums are stored and handled, and what the regulatory status of the class looks like after dicumyl peroxide joined the REACH Candidate List.

What Are Organic Peroxides and What Do They Do in Plastics?#

In plastics, organic peroxides do four different jobs: they crosslink polyethylene, EVA and POE into thermosets, they graft silanes and maleic anhydride onto polyolefin chains, they cut polypropylene chains in controlled-rheology visbreaking, and they initiate the polymerisation of LDPE and polystyrene. Each job uses the same radical chemistry at a different point in the life of the resin: crosslinking joins finished chains together, grafting attaches a small molecule to a chain, visbreaking shortens chains on purpose, and initiation starts chain growth from monomer before a polymer exists at all. Dialkyl peroxide production for these uses runs at about 60,000 t/yr, with dicumyl peroxide the dominant grade.

The hub on crosslinking agents for polymers compares the peroxide, silane and radiation routes side by side, since peroxide is only one of three industrial ways to build a thermoset network from a thermoplastic resin. The rest of this page stays inside the peroxide route and the chemistry that makes it work.

How does peroxide crosslinking work?#

Peroxide crosslinking works in four radical steps: the oxygen-oxygen bond splits, the resulting alkoxy radicals pull hydrogen atoms off the polymer backbone, the polymer macroradicals that remain combine in pairs, and the result is a permanent carbon-carbon bridge between two chains. Dicumyl peroxide shows the sequence clearly.

1. The oxygen-oxygen bond in dicumyl peroxide breaks by homolysis on heating, producing two cumyloxy radicals.
2. Each cumyloxy radical abstracts a hydrogen atom from a polyethylene chain, producing cumyl alcohol (which can lose water to form α-methylstyrene) and, by a competing β-cleavage path, acetophenone plus a methyl radical that goes on to form methane.
3. The hydrogen abstraction step leaves a macroradical on the polymer backbone at the site the hydrogen was removed from.
4. Two polymer macroradicals combine directly, and the result is a permanent carbon-carbon crosslink between the two chains.

The peroxide itself is consumed in this sequence, and only its fragments, methane, acetophenone, cumyl alcohol, α-methylstyrene and water, remain in the finished part; it is never built into the network and it is never a catalyst. Crosslinking efficiency from this sequence is well below one crosslink per peroxide molecule: Loan, J. Polym. Sci. A, 1964, measured about 0.4 crosslinks per peroxide molecule in ethylene-propylene rubber, a rubber system rather than a thermoplastic one, which is the closest published efficiency figure for this radical-combination step.

Why do peroxides crosslink polyethylene but degrade polypropylene?#

Peroxides crosslink polyethylene but degrade polypropylene because of one structural difference: the macroradical formed on a PP chain sits on a tertiary carbon and breaks apart by β-scission before it can find a partner, while the secondary macroradicals on a PE chain survive long enough to combine. Chain scission of this kind intensifies as peroxide content rises, which is why controlled-rheology PP grafting always competes with degradation rather than adding to it.

The deliberate use of that scission is [peroxide modification of polypropylene], the visbreaking route covered on its own page, where the same reaction that ruins a crosslinking attempt becomes the entire point of the process.

Is an organic peroxide the same as hydrogen peroxide?#

No: hydrogen peroxide is H2O2, an inorganic compound sold in water, while an organic peroxide replaces one or both of those hydrogen atoms with an organic group, which is what makes grades such as dicumyl peroxide solid, oil-soluble and usable in a polymer melt. The two share the reactive O-O bond but nothing else about their use: hydrogen peroxide bleaches and disinfects in water solution, while an organic peroxide crosslinks, grafts or initiates inside a plastics compound.

What Are the 5 Classes of Organic Peroxides Used in Polymers?#

The 5 classes of organic peroxide used in polymers are dialkyl peroxides, peroxyketals, peroxycarbonates, cyclic ketone peroxides and diacyl peroxides, and the dialkyl class does almost all of the thermoplastic crosslinking. The classes are listed here in order of importance to thermoplastics, from the dialkyl grades that dominate cable and foam to the diacyl grades that mostly stay in silicone rubber.

Table T1: class overview

Temperatures are the "typical crosslinking temperature" (t90 of about 12 minutes) from the Nouryon EMEIA crosslinking brochure, June 2026. Trials decide the real cure cycle.

1. Dialkyl peroxides#

Dialkyl peroxides carry the oxygen-oxygen bond between two alkyl or aralkyl groups, and this class supplies almost every crosslinking grade in the thermoplastics industry, from dicumyl peroxide in cable insulation to the bifunctional grades used in foam. Dicumyl peroxide, CAS 80-43-3, EC 201-279-3, C18H22O2, molecular weight 270.4, is a white crystalline solid melting at 39 to 40 °C with a density of 1.02 g/cm3 and 5.92 % active oxygen, and it is the reference grade the rest of this page uses for worked examples.

Di-tert-butyl peroxide, CAS 110-05-4, is the liquid, high-temperature member of the class, boiling at 110 to 111 °C with 10.94 % active oxygen. DHBP and BIPB are the bifunctional grades, carrying 11.02 % and 9.45 % active oxygen respectively, TBCP is the liquid grade used for direct peroxide injection in cable compounding, and hexyne peroxide is the high-temperature bifunctional grade used in PEX and rotomolding.

2. Peroxyketals#

Peroxyketals sit between the peroxycarbonates and the dialkyl grades: Trigonox 29 cures at about 145 °C and Trigonox 17 at about 160 °C, which suits compounds that cannot be taken to the 170 to 185 °C that dialkyl peroxides need. Trigonox 29, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, CAS 6731-36-8, has a safe processing temperature of 115 °C and a typical crosslinking temperature of 145 °C; Trigonox 17, butyl 4,4-di(t-butylperoxy)valerate, CAS 995-33-5, runs at 125 °C safe processing and 160 °C typical crosslink. Both grades appear alongside the dialkyl peroxides in the Nouryon dosage table for PE, EVA, POE and EPDM.

3. Peroxycarbonates#

Peroxycarbonates are the fast, low-temperature crosslinkers: TBEC has the lowest 10-hour half-life temperature of the common grades at 98 °C in chlorobenzene and cures at about 150 °C, which is what makes it the standard peroxide in photovoltaic encapsulant film. TBEC, CAS 34443-12-4, carries 6.49 % active oxygen, a 1-hour half-life of 117 °C and a 0.1-hour half-life of 137 °C, with an activation energy of 151.72 kJ/mol. Its SADT of 60 °C and Ts max of 20 °C are the lowest in the class, and refrigerated storage is the trade-off for that fast cure. TAEC (Trigonox 131), CAS 70833-40-8, runs at 110 °C safe processing and 140 °C typical crosslink. Storage conditions and encapsulant data are on [TBEC peroxide].

4. Cyclic ketone peroxides#

Cyclic ketone peroxides such as Trigonox 301 carry three peroxide bonds in one ring, which gives them the highest active-oxygen content of any crosslinking grade at 18.16 % in the pure substance and makes them the tool of choice for adjusting the melt flow rate of polypropylene. Trigonox 301, a cyclic MEK peroxide trimer, CAS 24748-23-0, EC 429-320-2, carries a 10-hour half-life of 125 °C, a 1-hour half-life of 146 °C and a 0.1-hour half-life of 170 °C in chlorobenzene, with an activation energy of 150.23 kJ/mol, an SADT of 110 °C and a Ts max of 40 °C; its active oxygen content falls to 7.3 to 7.6 % once diluted into the 40 to 42 % commercial formulation. Nouryon positions the grade for controlled rheology of virgin and recycled PP and for MFI reduction of recycled PE. Identity and the formulation-versus-pure-substance classification split are covered on [Trigonox 301 (cyclic triperoxonane)].

5. Diacyl peroxides#

Diacyl peroxides such as dibenzoyl peroxide decompose at low temperature and are used mainly in silicone rubber and as grafting initiators rather than as thermoplastic crosslinkers. Silicone rubber sits outside this site's border as a rubber chemistry, but the grafting use carries over into plastics: in a POE/LLDPE silane-grafting study, Dana, Zohuri and co-workers, J. Macromol. Sci. A, 2019, found benzoyl peroxide the better grafting initiator compared with dicumyl peroxide, with 0.2 wt% giving 79 % gel content.

How Is a Crosslinking Peroxide Selected? Half-Life, Scorch and Cure Temperature#

A crosslinking peroxide is chosen by its decomposition kinetics, not by its chemical class: the grade has to survive compounding without premature crosslinking and then decompose fast at the cure temperature, and two published numbers describe exactly that, the half-life temperature and the safe processing temperature. Four factors drive the choice in practice.

• The processing temperature the compound has to survive without premature crosslinking, known as scorch.
• The cure temperature and cycle time the production line allows.
• The storage and transport conditions the grade needs, set by SADT and Ts max.
• The byproducts and odour the peroxide leaves in the finished part.

Table T2: master kinetics and selection table

Half-lives are measured in chlorobenzene. "Safe processing temperature" means a rheometer scorch time ts2 above 20 minutes; "typical crosslinking temperature" means t90 of about 12 minutes. Source: Nouryon product data sheets and the EMEIA crosslinking brochure, June 2026. Blank cells mean the value is not in the data sheets used to build this table, not that it is zero.

Half-life temperatures (10 h, 1 h and 0.1 h) and the Arrhenius equation#

The half-life temperature is the temperature at which half of the peroxide has decomposed in a stated time, and suppliers publish it at three times, 10 hours, 1 hour and 0.1 hours, which for dicumyl peroxide means 112 °C, 132 °C and 154 °C in chlorobenzene. The underlying kinetics follow first-order decomposition: kd = A · e^(-Ea/RT) and t½ = ln 2 / kd. Because Nouryon publishes A and Ea for each grade, dicumyl peroxide carries A = 9.24 × 10^15 s-1 and Ea = 152.67 kJ/mol, the half-life at any process temperature can be calculated rather than interpolated from the three published points.

Full cure is usually taken as 6 to 7 half-lives at the cure temperature; this is a working convention used across the industry, not a written standard. A formulator who needs the half-life at an intermediate melt temperature, rather than at the three published reference points, can solve the Arrhenius equation directly with the [organic peroxide half-life calculator], which takes A and Ea per grade and returns the half-life at any entered process temperature.

Safe processing temperature and typical crosslinking temperature#

The safe processing temperature is the melt temperature at which a compound can be mixed and shaped without premature crosslinking, defined by the supplier as a rheometer scorch time above 20 minutes, and it sits about 40 °C below the typical crosslinking temperature for every dialkyl grade. The typical crosslinking temperature is defined the same way, as the temperature at which the compound reaches t90, about 12 minutes to 90 % of full cure on the rheometer.

The gap between the two numbers is the process window a compounder has to work inside. Dicumyl peroxide gives a window of 130 to 170 °C, di-tert-butyl peroxide 145 to 180 °C, and Trigonox 311 180 to 220 °C. A compound that has to be extruded hot, because the resin itself needs a high melt temperature, needs a grade further up this table so that its safe processing temperature clears the extrusion temperature with margin.

SADT and the maximum storage temperature#

SADT, the self-accelerating decomposition temperature, is the lowest temperature at which a peroxide in its original packaging can start to decompose on its own, and it ranges from 60 °C for TBEC to 110 °C for Trigonox 301. SADT is determined by the UN Heat Accumulation Storage Test and is a safety value, not a formulation choice.

Ts max, the supplier's recommended maximum storage temperature, runs from 20 °C for TBEC to 40 °C for DHBP, DTBP and Trigonox 301, and it is a quality-driven storage limit set to protect shelf life and consistent reactivity, not the safety limit that SADT represents. The two numbers must be kept apart: a drum stored above Ts max loses quality and consistency, while a drum stored near or above SADT is a self-heating hazard.

How Much Organic Peroxide Does a Compound Need?#

Peroxide dosage is quoted in phr, parts per hundred parts of resin, and supplier tables give it as phr of a diluted formulation rather than of the peroxide itself, which is why the same PE compound can be described as 1.4 phr or 0.56 phr without either number being wrong. Converting between the two bases with the PHR to weight percent calculator avoids that confusion before comparing two suppliers' recommendations.

Recommended dosage by polymer#

Nouryon's recommended dosages run from 0.8 phr of Trigonox 101-45 in polyethylene to 12.5 phr of Trigonox 17-40 in EPDM, always as phr of the diluted formulation and always with a coagent recommended for POE and EPDM. These figures come from a single supplier's product line and are stated here as phr of the 40 % or 45 % formulation, never of the pure peroxide.

Table T3: recommended dosage, phr of the formulation

Nouryon recommended dosage table, phr of the 40 % or 45 % formulation, not of the pure peroxide. Convert with Table T4 before comparing suppliers.

Converting phr of a 40 % formulation into active peroxide#

To compare two suppliers' recommendations, multiply the phr of the formulation by its peroxide content: 1.4 to 6.8 phr of Perkadox BC-40 is 0.56 to 2.7 phr of dicumyl peroxide, because the product is 40 % peroxide on an inert carrier. This is a calculation example built from the dosage table above, not a separate supplier recommendation.

Table T4: converting formulation phr to active peroxide

Active oxygen is a second, separate comparison basis and is not interchangeable with peroxide content: dicumyl peroxide carries 5.92 % active oxygen and DHBP carries 11.02 %, so equal phr of two grades does not mean equal radical yield.

Which Peroxide Suits Which Polymer and Product?#

The right peroxide depends on the cure temperature of the process and on what the byproducts are allowed to do in the finished part: dicumyl peroxide for cable and foam, di-tert-butyl or hexyne peroxide for the hot PEX-a and rotomolding routes, TBEC for photovoltaic film, and a cyclic grade when the aim is to cut polypropylene chains rather than join them. The full additive package that sits around the peroxide in each of these resins, stabilizers, fillers and processing aids, is set out on additives for polyethylene, since the peroxide is only one line of the formulation.

Table T5: selection by product

Supplier TDS ranges and published study values. Peroxide cures give tensile and tear strength about 15 % below a sulfur cure, with better compression set and heat resistance and no reversion (Nouryon). Trials decide the final level.

XLPE cable insulation#

XLPE cable insulation is crosslinked with dicumyl peroxide at 1.4 to 2.0 phr, extruded at a melt temperature of 120 to 140 °C so that no cure starts in the die, then vulcanised above 180 °C for about five minutes and degassed. In one HVDC study, gel content rose from 74.3 % to 81.6 % and hot-set elongation fell from 300 % to 80 % as DCP rose from 1.4 to 2.0 phr, and a dose above 1.4 % was needed to pass the hot-set requirement. The material itself, its grades and its temperature ratings, 90 to 105 °C operating, 130 to 140 °C emergency and 250 °C short circuit, are covered on XLPE: crosslinked polyethylene.

The full insulation and jacket package around this compound, including the additives that sit alongside the peroxide in a cable formulation, is on additives for wire and cable compounds. XLPE and PEX together account for about 5 to 10 % of the polyethylene market, with a 6 to 8 % compound annual growth rate expected.

PEX pipe and rotomolded crosslinked PE#

PEX-a pipe is made by the Engel process, in which HDPE carrying about 2 % peroxide is crosslinked in the melt at 200 to 250 °C, which is why the grades used here are the high-temperature ones, di-tert-butyl peroxide and hexyne peroxide. ASTM F876-23 sets the overall crosslinking range at 65 to 89 %, with a minimum of 70 % for the peroxide route specifically, 65 % for radiation and 65 % for silane. DIN 16892 is reported as giving PE-Xa 75 %, PE-Xb 65 % and PE-Xc 60 %, a secondary source not yet checked against ISO 15875.

The three pipe routes, peroxide, radiation and silane, are compared in full on [PEX-a, PEX-b and PEX-c]. Pipe-grade stabilization, the antioxidant and pressure-rating side of the same formulation, is on [additives for plastic pipes]. Rotomolded crosslinked PE tanks use the same high-temperature chemistry: hexyne peroxide, with a safe processing temperature of 145 °C and a typical crosslink temperature of 185 °C, is the grade Nouryon lists for this process.

EVA and POE foam#

EVA and POE foam for midsoles and mats is crosslinked with BIPB at 0.5 to 0.7 phr when a chemical blowing agent does the expansion, and at up to 1.2 phr when the foam is blown physically, which lifts gel content from 78 % to 91 %. A representative lab formulation combines the peroxide with 1.35 phr azodicarbonamide and 2 phr zinc oxide, pressed at 165 to 190 °C, and reaches a density of 0.15 to 0.25 g/cm3 once chemically foamed.

The gas side of the same formulation, the blowing agent that creates the cells, is covered under blowing agents, while the complete EVA additive package is on [additives for EVA]. Gas release and crosslinking have to be balanced in this process: too much crosslinking before the gas is released gives a dense, closed skin instead of an even cellular foam.

EVA and POE solar encapsulant#

Photovoltaic encapsulant film uses TBEC at about 1.5 % by mass, laminated at around 150 °C, and reaches 95 % of full crosslinking in 8.9 minutes for EVA against 14.6 minutes for POE. The formulation runs TBEC alongside about 0.1 m% HALS, and lamination cycles and gel targets in full are detailed under [crosslinking EVA and POE solar encapsulants].

Optimal gel content for this application sits at 84 to 90 %, with manufacturer data sheets citing minima of above 75 % for EVA and above 60 % for POE and JPL setting a 65 % floor; below 70 % gives poor cell adhesion and stability, while above 92 % increases yellowing of the film. A field survey by PI Berlin found adequate gel content in only about two thirds of 254 samples drawn from 120 modules, tested by Soxhlet extraction to IEC 62788-1-6. The stabilizer side of the same film, the UV and thermal package that sits alongside the peroxide cure, is on [additives for solar (PV) encapsulants]. TAIC's presence in commercial encapsulant formulations is presumed from FTIR peak analysis in the cited studies, not confirmed as a stated composition.

Polypropylene: visbreaking instead of crosslinking#

In polypropylene the same peroxides are used to cut chains on purpose: 200 to 600 ppm of DHBP in reactive extrusion raises the melt flow rate and narrows the molecular-weight distribution, which is how controlled-rheology PP for fibres and thin-wall moulding is made. A dose of 200 ppm is typical for staple-fibre CR-PP, and above 400 ppm mild and harsh screw designs start to diverge in the resulting rheology.

FDA 21 CFR 177.1520 clears DHBP as an initiator for propylene homopolymer and olefin copolymers containing at least 75 % propylene, on the condition that residual tert-butyl alcohol stays at or below 100 ppm. Melt flow rate, the property this visbreaking process controls, is measured at 230 °C and 2.16 kg for PP under melt flow rate test methods; the visbreaking page itself, the topic this H3 only summarises, carries the full depth on screw designs and property targets.

Recycled polyolefins#

Recycled polyolefins are the fastest-growing use for peroxides, because the same radical chemistry that cuts polypropylene chains can also branch them: lowering the melt flow rate and rebuilding melt strength turns a recycled grade back into a foaming, blow-moulding or thermoforming resin. Trigonox 301 is positioned by Nouryon for controlled rheology of recycled PP and for MFI reduction of recycled PE, while the company's patented Perkadox PM-60ST-GR grade lowers MFI and raises melt strength through long-chain branching, which is what reopens recycled PP to foaming, blow moulding and thermoforming applications.

The wider additive toolkit that peroxides sit inside for this use is on additives for recycled plastics, and branching competes directly with the additive route described under [melt strength enhancers]. A separate route uses radiation rather than peroxide: electron-beam crosslinking of recycled PE raised gel content from 46.7 % to 56.2 % across a dose range of 95 to 125 kGy, with 110 kGy giving the best balance of properties (Polymers, 2026).

What Do Coagents Do, and When Does a Peroxide Need One?#

Coagents are polyfunctional monomers added with a peroxide to raise the number of crosslinks each radical produces, which lets the formulator cut the peroxide dose, and they are the only way to crosslink polypropylene at all, because they intercept the tertiary macroradicals before β-scission can break the chain. Every coagent chemistry used with crosslinking peroxides is compared in full on [crosslinking coagents].

[TAIC (triallyl isocyanurate)] is the allylic coagent used in encapsulant film and e-beam wire, and TAC isomerises to TAIC on heating, as Gillham and Mentzer, J. Appl. Polym. Sci., 1973, first documented. [TMPTMA] is the methacrylate coagent used in radiation-crosslinked PP foam; in an e-beam crosslinked PP/POE foam system it raised crosslinking with rising dose up to about 8 phr and then plateaued, reaching 55 % crosslinking at 15 kGy. Nouryon recommends a coagent for POE and EPDM in every dosage line of Table T3, since these two resins crosslink poorly with a peroxide alone. No TAIC dosage figure is established in our source library, and none is stated here.

What Byproducts Do Peroxides Leave, and Why Is XLPE Degassed?#

Every peroxide crosslink leaves decomposition fragments in the part: dicumyl peroxide leaves methane, acetophenone, cumyl alcohol, α-methylstyrene and water, and in high-voltage cable these raise the conductivity of the insulation enough that the cable has to be degassed before it can be used. Degassing runs at about 70 °C for 24 hours in laboratory practice, and for days at industrial scale.

• Methane, a gaseous fragment from the methyl radical formed during β-cleavage of the cumyloxy radical.
• Acetophenone, formed by the same β-cleavage step and the main contributor to residual odour.
• Cumyl alcohol, formed directly by hydrogen abstraction from the polymer chain.
• α-Methylstyrene, formed when cumyl alcohol loses water.
• Water, released in the same dehydration step that produces α-methylstyrene.

These byproducts explain three things a buyer notices in a finished part: odour in foam and footwear, fogging in automotive interior parts, and the degassing step that lengthens cable production before the reel can ship. Byproduct levels are the main technical argument both for BIPB as a lower-odour alternative to DCP, a supplier positioning rather than a confirmed byproduct comparison, and for the peroxide-free insulation research covered in a 2024 Advanced Materials review. Di-tert-butyl peroxide leaves a different byproduct pair, tert-butanol and acetone, and FDA 21 CFR caps residual tert-butyl alcohol in visbroken PP at 100 ppm for the same reason DCP-cured cable needs degassing: the fragment itself, not the finished polymer, carries the regulatory limit.

How Is the Degree of Crosslinking Measured?#

The degree of crosslinking is measured either as gel content, the fraction that will not dissolve in hot xylene under ASTM D2765, or as hot-set elongation, the stretch of a loaded specimen at 200 °C under IEC 60811-507, and the pass mark comes from the product standard rather than from a general rule. Both metrics move together in the XLPE study cited above, gel content and hot-set elongation both track rising DCP dose in the same compound.

Table T6: crosslinking targets by standard

Both methods, with their solvents and specimen geometry, are described in full on [gel content and hot set test].

How Are Organic Peroxides Stored and Handled Safely?#

Organic peroxides are class 5.2 dangerous goods, and the number that controls their storage is the SADT, the self-accelerating decomposition temperature measured in the original packaging by the UN Heat Accumulation Storage Test. Handling in a compounding plant follows five rules that apply to every crosslinking grade on this page.

• Store peroxide below the supplier's Ts max, which is 20 °C for TBEC and 30 to 40 °C for the dialkyl grades.
• Never weigh out peroxide inside the storage room; weighing and dispensing happen in a separate area.
• Keep peroxides away from reducing agents, amines, acids and metal salts, all of which can trigger decomposition.
• Melt a frozen liquid peroxide only with indirect heat, at a maximum of about 25 °C, never with a direct flame or hot surface.
• Keep the original packaging, since SADT is a packaging-dependent value that does not carry over if the peroxide is repackaged.

Hazard classification differs by grade: DTBP is classified Flam. Liq. 2, H225, together with Org. Perox. E, H242, and Muta. 2, H341, while Trigonox 301's pure substance carries Org. Perox. B, H241. What the label and the safety data sheet must state for every grade on this page is covered under [safety data sheets and GHS labels].

What Is the Regulatory Status of Crosslinking Peroxides?#

Crosslinking peroxides were an unregulated corner of the additive market until 27 June 2024, when dicumyl peroxide, the most used grade of all, was added to the REACH Candidate List as toxic for reproduction. In the EU, food-contact clearance runs through Regulation (EU) No 10/2011; in the US, it runs through 21 CFR; no crosslinking peroxide on this page carries the word "approved" from either authority, only "listed", "cleared" or "authorised" under the specific instrument that applies to it.

Dicumyl peroxide on the SVHC Candidate List since 27 June 2024#

Dicumyl peroxide has been on the REACH Candidate List since 27 June 2024, listed under Article 57(c) as toxic for reproduction and described by ECHA as a processing aid and cross-linker in polymers, which makes it the first crosslinking peroxide with SVHC status. The listing was the sole entry of the 31st update. Its harmonised CLP classification, index 617-006-00-X under ATP15, carries Org. Perox. F, H242, Repr. 1B, H360D, Skin Irrit. 2, H315, Eye Irrit. 2, H319, and Aquatic Chronic 2, H411. Dicumyl peroxide is not on REACH Annex XIV, so it does not require authorisation, but it is on the CoRAP list for further substance evaluation.

For a converter, this listing means a duty to check, not a confirmed breach: an XLPE or EVA-foam article carrying more than 0.1 % w/w residual dicumyl peroxide triggers REACH Article 33 information duties down the supply chain and a SCIP database notification, and residual DCP levels in finished XLPE articles still need verifying against that threshold rather than being assumed to exceed it. Formulators moving away from dicumyl peroxide have named alternatives that include BIPB, DHBP, tert-butyl cumyl peroxide, silane crosslinking and electron-beam crosslinking. Every other plastic additive carrying SVHC status is tracked on the SVHC Candidate List page.

Food contact: EU 10/2011 and 21 CFR#

No crosslinking peroxide is on the Union list of Regulation (EU) No 10/2011: peroxide residues in food-contact plastic are generally handled as aids to polymerisation under Article 6(4)(b), which leaves them to national law rather than to a specific migration limit. How the Union list and Article 6 work in full is explained on EU 10/2011.

Table T8: regulatory matrix

Candidate List status was checked against the CIRS compilation of the 35th update, November 2025, and ECHA CHEM on 22 September 2026; 2026 Candidate List updates were not re-checked. "No entry" means no entry was found in the source searched, not that use is prohibited.

Dicumyl peroxide is cleared for adhesives under 21 CFR 175.105, as a polymerisation catalyst only under 175.300, for crosslinked polyester resins under 177.2420 and for rubber articles under 177.2600. DHBP is cleared under 177.1520 as an initiator for propylene polymers, on the condition that residual tert-butyl alcohol stays at or below 100 ppm, and DTBP is cleared under 177.2600 and named among the closure-gasket substances in 177.1210. TMPTMA is FCM 463 with an SML of 0.05 mg/kg, and vinyltrimethoxysilane is FCM 453 at the same 0.05 mg/kg limit; TAIC has no Union list entry and no FDA hit. The full 21 CFR structure that governs these clearances is decoded on FDA food contact rules for plastic additives.

Who Supplies Crosslinking Peroxides?#

Crosslinking peroxides for plastics come from a short list of producers: Nouryon sells them as Trigonox and Perkadox, Arkema as Luperox, and Pergan under its own name, and the same molecule appears under a different code in each catalogue. Nouryon's organic peroxide business traces to the renaming of AkzoNobel Specialty Chemicals on 9 October 2018, with sites including Radnor, Pennsylvania and Amsterdam; Arkema sells the Luperox range and reported revenue of EUR 9.1 billion in 2025. Buyers should compare grades by CAS number, active-oxygen content and the peroxide content of the formulation, not by trade name.

Table T7: same chemistry, different trade names (not a performance-equivalence claim)

Trade-name mappings from supplier data sheets in our source library. Entries marked as reported, not confirmed, are equivalences that have not been checked against a current catalogue.

Plants, grades and certifications by company are in the directory of [organic peroxide manufacturers and suppliers].

What Are the Alternatives to Peroxide Crosslinking?#

Peroxide is one of three industrial ways to crosslink a polyolefin, and the other two, silane moisture curing and electron-beam irradiation, win wherever the peroxide byproducts, the cure temperature or the degassing step is the problem. Each alternative trades one part of the peroxide process for a different limitation.

Silane crosslinking and electron-beam crosslinking#

Silane crosslinking replaces the peroxide network with Si-O-Si bridges formed by moisture, and it still needs a small peroxide dose, because the vinyl silane has to be grafted onto the polyethylene chain before water can cure it. The two commercial routes, Sioplas and Monosil, were patented in 1968 and 1974 respectively, and the water-cured network is unsuitable for high-voltage insulation because residual water adds charge carriers to the dielectric. In a POE/LLDPE grafting study, Dana, Zohuri and co-workers, 2019, found benzoyl peroxide outperformed dicumyl peroxide as the grafting initiator, with 0.2 wt% giving 79 % gel content and 40.4 % compression set. The two-step and one-step routes are set out in full on [silane crosslinking (Sioplas and Monosil)].

Electron-beam crosslinking runs at 50 to 150 kGy and is done below the polymer's melting point, which is why it crosslinks less uniformly through a thick wall than a peroxide cure does. Dose windows per polymer are on [radiation (e-beam) crosslinking].

Organic peroxides outside polymer crosslinking#

The phrase organic peroxide also covers chemistry that has nothing to do with compounding: MEKP hardeners for unsaturated polyester resin, bleaching agents, and the peroxides that form by themselves in stored ethers and other solvents, which is what most laboratory safety guidance is about. Peroxide-cured rubber sits in the same adjacent category, since it uses the same radical chemistry inside a different material class; the elastomer side of plastic additive use, including its own peroxide chemistry, is summarised under [plastic additives in rubber and elastomers]. This page covers additives used in plastics only, and everything above the contextual line stays inside that border.

What is organic peroxide used for?#

In the plastics industry, organic peroxides are used to crosslink polyethylene, EVA and POE, to graft silanes and maleic anhydride onto polyolefins, to visbreak polypropylene and to initiate the polymerisation of LDPE and polystyrene. Outside plastics, the same chemistry cures unsaturated polyester resin, bleaches, and forms unintentionally in stored ethers and other peroxide-forming solvents.

Why are organic peroxides hazardous?#

Organic peroxides are hazardous because the oxygen-oxygen bond that makes them useful also lets them decompose on their own once the packaging warms past the SADT, releasing heat that accelerates the reaction further. That self-accelerating behaviour is why the class has its own UN transport class, 5.2, and its own grade-specific control temperature rather than one general storage rule.

Can peroxide-crosslinked plastics be recycled?#

A peroxide crosslink is a permanent carbon-carbon bond, so XLPE and PEX cannot be remelted like a thermoplastic, and the 5 to 10 % of the polyethylene market that is crosslinked is the reason de-crosslinking and thermoplastic cable insulation are active research topics. A 2024 ACS Applied Polymer Materials review, "Cross-Linked Polyolefins: Opportunities for Fostering Circularity", covers this research directly. No recycling-rate figure for XLPE is established in our source library, so none is stated here. What crosslinking does to a recycling stream in general is covered under design for recycling.

What is the difference between a crosslinking peroxide and a polymerisation initiator?#

They are often the same molecule used at a different moment: di-tert-butyl peroxide initiates the polymerisation of LDPE and polystyrene from monomer, and the same grade crosslinks finished HDPE in a PEX-a pipe line. An initiator starts chain growth before a polymer exists; a crosslinking peroxide joins chains that are already finished, inside a compound rather than inside a reactor.

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