Luperox® for General Purpose and High-Impact Polystyrenes
Productivity (e.g. polymer per hour of reactor time) is higher when using peroxides vs. thermal energy alone.
General Purpose PS
The industry requirements for GPPS polymerization are:
- high molecular weight
- broad molecular weight distribution
- low level of dimers and trimers
- high reactor productivity
High-Impact PS
For HIPS the industry requirements include:
- low levels of dimers and trimers
- high space-time yield
- excellent grafting
- small particle size
- suitable mechanical properties
Luperox® JWEB™ 50
A new initiator for higher MW polystyrene and improved productivity
Luperox® JWEB™ 50 can be used alone or in combination with other initiators to synthesize higher molecular weight resin than using a more traditional di-functional initiator alone.
This table compares the molecular weights of resins produced in batch mode using a linear temperature ramp from 103 to 151°C and a constant, total active oxygen comprising various ratios of Luperox® JWEB™ 50 and Luperox® 331M80.
Luperox® JWEB™ 50 alone increases Mw by 35%. Note that Luperox® JWEB™ 50 is expected to slightly increase the polydispersity index as a result of the high molecular weight fraction produced by the multi-functional initiator fragment.
Luperox® JWEB™50 | Luperox® 331M80 | Molecular Weight | Polydispersity Index |
0 | 100 | 325,000 | 2.3 |
20 | 80 | 336,000 | 2.3 |
60 | 40 | 375,000 | 2.5 |
100 | 0 | 440,000 | 2.6 |
Data shown was produced at internal Arkema R&D by mass polymerization with a continuous stirred tank reactor (CSTR) and pseudo-plug flow reactor (PFR) making polystyrene at 2 lbs/hr.
A Range of Solutions
The chart shows how Luperox® organic peroxides can help to boost styrene monomer conversion, or molecular weight, or both! Each figure corresponds to a certain peroxide grade. The tetra-functional product, Luperox® JWEB™ 50 offers both gains in molecular weight and monomer conversion as compared with a thermal energy process alone.

Peroxide vs. thermal energy polymerization:
Higher molecular weight with the same residence time is readily obtained using Luperox® 331.
- Initial process temperature is decreased to minimizing thermal polymerization.
- Ending process temperature similar to thermal process, minimizing viscosity increase.
- A 10% increase in molecular weight is obtained in the peroxide process.
Luperox® 331 (ppm) |
Temp. Profile (°C)
|
Conversion (%) |
Molecular Weight (g/mol) |
---|---|---|---|
0 (Thermal) |
120 to 160 °C (4h) | 82 | 265.000 |
361 | 105 to 150 °C (4h) | 80 | 296.000 |
542 | 105 to 150 °C(4h) | 80 | 289.000 |
Difunctional versus Monofunctional peroxides
For polymerization of GPPS, di-functional peroxides are preferred to monofunctional options. Here is a comparison of a styrene polymerization using Luperox® P (TBPB) to Luperox® 331M50.
The monofunctional Luperox® P yields essentially the same conversion as Luperox® 331M50. The di-functional gives exceptional molecular weight.
Residual Styrene Content using Luperox® 331M50 vs. TBPB

Polyfunctional Peroxides to Increase Conversion
Combination of different peroxides drives higher conversion rates. Because styrene polymerization occurs over a broad temperature range, peroxide combinations are necessary to optimize output. Luperox® 331M50 works only in the lower temperature range of a styrene polymerization.
To complement this, Luperox® 101 can supply difunctional radicals for higher temperatures. The graph below shows the number of radicals formed per minute using either Luperox® 331M50 or Luperox® 101 over a common temperature profile.
Thermal gradient: Luperox® 331 and Luperox® 101

Browse products and solutions
Choose a recommended product and see available formulations or get technical assistance:
Luperox® 26
tert-butyl peroctoate
Luperox® 531
1,1-di-(tert-amylperoxy) cyclohexane
Luperox® 270
tert-butyl peroxyisononanoate
Luperox® 256
2,5-dimethyl-2,5-di(2-ethyl-hexanoylperoxy)hexane
Luperox® JWEB™ 50
polyether poly-tert-butylperoxycarbonate
Luperox® 231
1,1-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane
Luperox® 331
1,1-di-(tert-butylperoxy) cyclohexane