Calprene® SBS 412 is a linear styrene-butadiene-styrene block copolymer produced by Dynasol. The grade is non-oil-extended and is classified under CAS 9003-55-8. Bound styrene content is reported at 30 wt% under ASTM D5775. The material is differentiated in the Dynasol SBS range by a comparatively low solution viscosity and a melt mass-flow rate suitable for high-shear processing without plasticizer extension. The following table consolidates publicly reported typical property ranges used for incoming material reconciliation.

The low diblock content, typically below 1 wt% by gel permeation chromatography, limits the concentration of unattached diblock chains that plasticize the styrenic network and reduce cohesive strength at 70°C in adhesive films. Volatile matter is controlled below 0.5 wt% per ASTM D5668, which reduces vacuum-vent fouling in compounding extruders. Ash residue below 0.2 wt% per ASTM D5667 reduces abrasive wear in pelletizing die plates and injection-mould screws. Tensile strength and hardness values are generated on compression-moulded sheets after conditioning for 24 h at 23±2°C and 50±5% RH according to ISO 23529.

Incoming inspection of Calprene 412 on a production scale normally verifies melt mass-flow rate, solution viscosity, and ash content before release to a high-shear asphalt or adhesive line. A lot at the upper end of the melt flow range can reduce pressure drop across a hot-melt coater die by 10–18% relative to a lot at the lower end when the same barrel temperature profile is retained. Therefore, temperature set points in continuous adhesive coaters are adjusted by 5–10°C after a lot change if slot-die exit thickness varies by more than ±5%. The porous crumb absorbs moisture at relative humidities above 60% RH; surface moisture not removed before melt processing expands in the melt and causes bubble formation in coatings. Hopper drying with dehumidified air at 45–50°C for 2–3 h is applied only when opened bags have been exposed to condensation. In twin-screw compounding, a co-rotating intermeshing extruder with L/D 40:1 and segmented elements operates with feed-throat temperature below 40°C to prevent crumb bridging; barrel temperatures are ramped from 140°C at the feed section to 180°C at the die. Melt temperature above 220°C for more than 20 min produces chain scission in the polybutadiene midblock, observed as a solution-viscosity decrease of 10–15% and a measurable yellowing increase. Amine-based antistatic additives and transition-metal stearates should be excluded from heat-stabilized compounds because they accelerate oxidative degradation. The product should not be combined with chlorinated paraffins at processing temperatures above 160°C because dehydrohalogenation releases hydrogen chloride that catalyzes midblock chain scission.

Regulatory documentation for Calprene 412 is supplier-controlled under EU REACH and RoHS Directive 2011/65/EU. Food-contact use is not automatic; a formulation intended for food-contact articles must be confirmed under FDA 21 CFR Part 177 or EU Regulation 10/2011 after migration testing because residual oligomers and antioxidant additives are formulation-dependent. For industrial footwear, automotive, and asphalt modification, the material is handled under standard industrial hygiene practices; airborne crumb dust must be controlled below applicable workplace exposure limits. Spillage on hot surfaces above 220°C releases decomposition products requiring local exhaust ventilation.

What occurs when Calprene 412 is dispersed into bitumen under high-shear conditions?

Asphalt modification with Calprene 412 usually employs a two-stage process to avoid phase inversion. The crumb is initially added to 160–170°C bitumen under paddle agitation for 15–30 min, allowing maltenes to penetrate the porous crumb and soften the styrenic domains. The mixture is then passed through a rotor-stator high-shear mill with tip speeds of 18–25 m/s at 175–185°C. Under these conditions, the polymer phase is typically reduced to particles below 10 µm; residual agglomerates above 50 µm correlate with phase separation and high viscosity at low shear. A typical dosage of 3.0–4.5 wt% on a 60/70 pen base bitumen raises the ASTM D36 softening point from approximately 48°C to 78–85°C. Complex shear modulus at 64°C under AASHTO M332 conditions shifts into a higher performance grade; multiple-stress creep recovery non-recoverable compliance at 3.2 kPa typically falls below 0.5 kPa⁻¹, indicating substantial elastic response. Viscosity at 135°C under ASTM D4402 is commonly 1.8–2.5 Pa·s at 12 s⁻¹. Storage stability is checked by EN 13399 after 72 h at 180°C; a difference in softening point between the top and bottom fractions greater than 3°C is rejected for tank storage. Processing above 190°C for more than 60 min accelerates crosslinking reactions with bitumen radicals, increasing the EN 13399 top-bottom softening-point difference and reducing ductility. Field reports from high-shear plants indicate that a lot with an MFI near the upper limit reaches maximum dispersion approximately 25–35% faster than a lot near the lower limit; however, published data for this specific configuration is limited.

Solvent-borne and hot-melt adhesive rheological boundaries

In hot-melt pressure-sensitive adhesives, Calprene 412 is mixed with C5 or C9 hydrocarbon tackifiers and naphthenic or paraffinic oil at 150–170°C in vertical change-can mixers with scraped-wall agitation or in recirculating screw melters. A starting tackifier-to-polymer mass ratio of 1:1 to 1.5:1 is used for general-purpose tape applications; oil loading is limited to 20–35 phr because higher plasticizer content reduces 180° peel adhesion on stainless steel below 2 N/cm under ASTM D3330. Loop tack at 23°C under ASTM D6195 is typically 15–25 N/25 mm for a 25 µm adhesive film on biaxially oriented polypropylene. Shear adhesion failure temperature under ASTM D4498 with a 1 kg load remains above 70°C for plasticizer-free formulations. In solvent-borne systems, a 25 wt% toluene solution shows Brookfield viscosity of 900–1300 mPa·s at 23°C using spindle 2 at 20 min⁻¹. This range permits reverse-roll coating at line speeds of 15–30 m/min without edge-tailing; methyl ethyl ketone may be added to accelerate drying but can reduce solution stability when C5 tackifier polarity is high. Amine-cured or chlorinated-paraffin systems are avoided for the degradation reasons described above. Processing temperatures are held below 190°C in hot-melt mixers to protect the antioxidant package; when temperature excursions occur, the pressure-sensitive adhesive shows a decline in shear adhesion failure temperature of approximately 5–10°C after 2 h of hold time.

When Calprene 412 replaces higher molecular weight SBS grades in thermoplastic compounding

Calprene 412 is differentiated from higher molecular weight linear SBS grades such as Calprene 411 and from oil-extended grades such as Calprene 416 by melt viscosity, tensile strength, and oil tolerance. The melt mass-flow rate of Calprene 412 under ASTM D1238 is approximately 3–5 times higher than that of Calprene 411, and the 25 wt% toluene solution viscosity is roughly 50% lower. In injection-moulded footwear, this difference reduces filling pressure by 15–25% at a melt temperature of 180°C and a mould temperature of 30°C, but also lowers tensile strength by 10–20% relative to a higher molecular weight SBS compound with the same styrene content. The lower molecular weight increases compression set at 70°C under ISO 815-1 method A after 22 h; thin-walled soles may show earlier loss of cushioning. Calprene 416 is oil-extended; direct substitution into an existing compound without reducing extender oil by the same phr is invalid because hardness drops by 5–10 Shore A for every 20 phr of extender oil present. Compared with radial SBS grades, Calprene 412 produces lower elastic recovery in bitumen but completes dispersion earlier in high-shear mixing. The selection of Calprene 412 is therefore limited to applications where low melt viscosity and high-shear processability are the primary constraints, rather than maximum tensile, abrasion, or elastic-recovery performance.