SP/PA Rubber (Super Processing/Processing Aid Rubber)

Manufacturer:  Although our main activity is in the manufacturing of latex products we have recently ventured into making rubber products using both synthetic and natural rubber in their solid/dry form. The processes used include calendaring and extrusion. We are now facing some production problems. Some one suggested that we should try incorporate SP/PA Rubber in our formulation. Can you tell us more about these materials. What are they?

 
John Woon (Senior Latex Consultant):  SP and PA stand for "Super Processing" rubber and "Processing Aid" rubber respectively.

These rubbers were developed by RRIM in Malaysia more than 50 years ago. The rubber was initially made in the form of sheets in 1950’s. With the advent of SMR Scheme in block form in 1960’s, block form of SP/PA started to be produced.

These were made by blending prevulcanised latex with unvulcanised latex concentrate to ensure good homogeneity. Different mix ratios are being used to make, for instance, SP20, SP40, and SP50 with the number indicating the percentage of vulcanized rubber.

PA rubbers are the more “concentrated” versions of  SP. Examples are PA80 with 80% vulcanized rubber and PA57 (This is PA80 with added non-staining naphthenic oil).

SP/PA are used to help overcoming processing problems with NR and synthetic rubber compounds especially during extrusion and calendaring. You are expected to have smoother surfaces with less surface defects in your calendered and extruded products.

Please let me know your results.