Sofprene TR for shoe soles

Sofprene ® (TPR)

Thermoplastic Rubber Compound
Sofprene® is the trade name of SO.F.TER. footwear compounds based on SBS (Styrene-Butadiene-Styrene block co-polymers) thermoplastic rubbers having a high degree of elasticity thanks to their peculiar block structure. The great success of these polymers relies on their cost-effective and easy processability allowing the production of rubber-like soles without bearing the long and expensive curing process.



SO.F.TER developed a wide range of materials including the compact and micro-light rubber-like grades, the expanded grades with an aged effect and also the transparent and translucent types. All of these materials are available in a choice of fashion colours and can be supplied, on request, in a version for direct injection onto upper.



Besides the wide choice of existing formulations, SO.F.TER. can offer a technical assistance service for developing tailor-made materials so to meet any request coming from customers
The Sofprene® footwear compounds have the following general characteristics:
  • Available in a hardness range from 40 to 85 ShA
  • High elastic recovery both at low and room temperature
  • Operating temperature from -40 °C to +50 °C
  • Excellent colourability
  • Good price/quality ratio
  • Easy processability.
The Sofprene® footwear compounds are normally processed by injection moulding machines. Extrusion is only used for the production of rands.
The injection process can be carried out with the simple screw type, controrotating screw type or transfer type machines.
By use of proper equipment it is possible to inject soles composed of 2 or 3 different colours and/or directly inject onto upper.
The following indications are intended as general guidelines and they must be adjusted to the equipment used. PLASTICIZING SCREW: screws having L/D ratio >= 20 are the most suitable
INJECTION SPEED: medium-high
RUNNERS: it is recommended to use runners which are as short as possible, having a circular section and a gradually decreasing flow-through diameter
INJECTION POINTS: usually having circular section and diameter > 2 mm. For micro-light and expanded compound a diameter of 6- 8 mm is recommended.
AIR VENTS: the mould should be provided with appropriate air vents (diameter 0.03 - 0.05 mm) SHRINKAGE: ranging from 0,4% to 1,2% according to the material hardness and type.
DRYING: usually not necessary
Sofprene® is a fully recyclable material and it can be reused after regrinding. The user shall always verify that the compound obtained by mixing virgin and reground material is suitable for the specific application and that its properties meet the requirements.
This product should be stored in a covered facility and kept away from moisture and heat. When properly stored, away from moisture, do not need drying before processing.
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