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
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|
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.
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)
Molecular Weight (g/mol)
||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
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tert-butyl peroxy isononanoate
Luperox® JWEB™ 50