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® JWEB50 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

Residual styrene

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

Rate of peroxide decomposition

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



Luperox® JWEB™ 50

polyether poly-tert-butylperoxycarbonate


Luperox® 231




Luperox® 331

1,1-di-(tert-butylperoxy) cyclohexane



Find the right product for your application!

Contact the Luperox® salesperson in your region to learn more

North America

Jay Divyesh SHAH
Digital & Market Manager

Central America

Monserrat ALVAREZ
Sales Manager
Arkema Mexico SA de CV
Gustavo Baz 2160 - 3, La Loma, Tlalnepantla, Mexico 54070

South America

Business Unit Manager
Arkema Quimica LTDA
Avenida Ibirapuera 2033 4° Andar - Bairro Moema CEP 04029-901 SÃO PAULO (SP) BRASIL

Europe and Africa

Business Manager
420 rue d'Estienne d'Orves 92705 Colombes Cedex FRANCE


Sales Manager
Arkema Peroxides India Private Ltd
1st Floor, Balmer Lawrie House 628, Anna Salai, Teynampet, Chennai (Madras), India 600 018

Southeast Asia

Regional Manager
10 Science Park Rd #01-01A, The Alpha, Singapore Science Park II, Singapore 117684

Far East

Jonathan CHANG
Greater China Sales Director
Arkema Changshu Chemical Co Ltd
7F Block 1, Life Hub@Daning 1868 Gonghexin Rd. Shanghai 20072 CHINA

Middle East

Sales Manager
ARKEMA FRANCE, Middle East Office
Unit 2801 Indigo Icon Tower, Dubai UAE