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Butanox® M-50 VRN is the work horse in GRP curing systems, including a Vanishing Red (VR) system. Medium-reactive, general purpose methyl ethyl ketone peroxide (MEKP) with guaranteed low water content, used for curing unsaturated polyester resins in the presence of a cobalt accelerator at room and elevated temperatures.
Butanox M-50 VRN is methyl ethyl ketone peroxide (MEKP, CAS 1338-23-4) in dimethyl phthalate with a vanishing red indicator system, from Nouryon. It is a general-purpose MEKP with low water content for curing unsaturated polyester resins with a cobalt accelerator at room and elevated temperatures. Butanox M-50 VRN has replaced the earlier Butanox M-50 VR.
The red colour shows that the catalyst has been added and mixed evenly into the resin, and it virtually disappears during cure, so the colour is there when you need it and gone in the finished part. Apart from the indicator, it matches the standard Butanox M-50 in active oxygen (8.8–9.0 %), density and viscosity. If your process must be phthalate-free, choose Butanox M-50A instead. Our expert guide Butanox M-50 vs M-50A vs M-50 VRN compares all three, and our article on fading MEKP explains how the indicator works in practice. See all grades in the organic peroxide range.
| Property | Value |
|---|---|
| Chemical name | Methyl ethyl ketone peroxide, solution in dimethyl phthalate, with vanishing red indicator |
| CAS number | 1338-23-4 |
| EINECS / ELINCS | 215-661-2 |
| TSCA status | Listed on inventory |
| Appearance | Red liquid |
| Total active oxygen | 8.8–9.0 % |
| Density, 20 °C | 1.180 g/cm³ |
| Viscosity, 20 °C | 24 mPa·s |
| SADT | 55 °C |
| Maximum storage temperature (Ts max) | 25 °C |
| Transport classification | Organic peroxide type D, liquid; Division 5.2; UN 3105; PG II |
| Standard packaging | 30 L HDPE can, 25 kg net |
| Shelf life | At least 6 months after delivery when stored as recommended |
| Replaces | Butanox M-50 VR |
The Butanox M-50 VRN product data sheet (TDS/PDS) lists specifications, the vanishing red indicator system and storage limits. The safety data sheet (SDS/MSDS) covers hazard classification, transport and emergency measures. English and Chinese documents can be downloaded below or requested through the inquiry form.
-Hand lay-up and spray-up: the red colour lets operators check by eye that catalyst has been added and spread evenly before the resin gels.
-Gelcoats and coatings: cobalt-accelerated cure, with the indicator colour virtually gone after cure.
-Laminating and moulding: continuous laminating, resin transfer moulding and filament winding.
-Marine GRP: low water content and no polar compounds suit GRP parts that must resist water.
-Other uses: engineered stone, buttons and vinyl ester resins.
Store Butanox M-50 VRN below 25 °C in tightly closed original containers, in a dry, well-ventilated area away from heat, ignition sources and direct sunlight. Its SADT is 55 °C, five degrees lower than standard Butanox M-50, so keep warehouses cool in summer. Keep it away from accelerators, reducing agents such as amines, acids, alkalis and heavy metal compounds, and never mix it directly with a cobalt accelerator: add each to the resin separately.
A: Butanox M-50 VRN is Nouryon's methyl ethyl ketone peroxide in dimethyl phthalate with a vanishing red indicator, CAS 1338-23-4. It cures unsaturated polyester resins with a cobalt accelerator at room and elevated temperatures.
A: Yes. Butanox M-50 VRN has replaced Butanox M-50 VR. If your purchase specification still names M-50 VR, update it to M-50 VRN.
A: No. The red colour is visible while the catalyst is mixed into the resin and virtually disappears during cure.
A: Both have 8.8–9.0 % active oxygen and the same density and viscosity. M-50 VRN adds the vanishing red indicator, and its SADT is 55 °C compared with 60 °C for M-50.
A: Store it below 25 °C in closed original containers, away from heat, sunlight, accelerators, reducing agents, acids, alkalis and metal compounds. Under these conditions it stays within specification for at least 6 months after delivery.
A: The product data sheet and safety data sheet can be downloaded on this page or requested through the inquiry form, in English or Chinese.
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