Ningbo Changhong SBS CH332 is identified as a linear styrene-butadiene-styrene block copolymer of the non-oil-extended class. Manufacturer-published datasheet values for the specific CH332 designation are not available in this technical compilation; published data for this specific configuration is limited. The following description therefore defines the behavioural envelope of linear SBS triblock copolymers with a bound-styrene content of 30–33 wt% and a diblock content below 1.0 wt%, which is the compositional envelope most commonly associated with this grade family. Lot-specific certificate-of-analysis data should be obtained from Ningbo Changhong before compounding or specification setting.

When the material falls within that envelope, typical bulk properties are measured under ASTM D638 at a crosshead speed of 500 mm/min and include tensile strength between 18 MPa and 26 MPa, elongation at break between 600% and 850%, and Shore A hardness between 70 and 85 using ASTM D2240 with a 15 s delay. Melt flow rate under ISO 1133-1:2022 at 190 °C with a 5.0 kg load is typically 0.5–5.0 g/10 min, depending on the molecular-weight distribution of the specific lot. Specific gravity measured by ISO 2781 is generally 0.94–0.96, and volatile matter according to ASTM D5668 should be held below 0.5 wt%. These values are comparative boundaries rather than CH332 release specifications.

Thermal analysis by ISO 11357-2 typically reveals two glass transition events for this polymer class: a low-temperature transition in the polybutadiene-rich phase near −85 °C to −80 °C and a high-temperature transition in the polystyrene domains near 90 °C to 100 °C. The styrenic domains are responsible for physical crosslinking below their transition. Compression set under ASTM D395 Method B at 70 °C for 22 h is commonly 20–35% for non-oil-extended linear SBS, though the value depends on molecular weight and test conditioning. These thermal and compression-set boundaries are used in quality-control comparisons against oil-extended and radial grades rather than as release values for CH332.

What Distinguishes a Non-Oil-Extended Linear SBS from Oil-Extended, Radial, and Hydrogenated Grades?

The differentiation is governed by molecular architecture and mid-block unsaturation. The linear non-oil-extended SBS class reaches phase inversion in bitumen within the 170–190 °C digestion window more rapidly than radial SBS because branch-free chains diffuse and disentangle at lower shear. Tensile strength measured under ASTM D638 may be 2–5 MPa lower than radial grades of equivalent styrene content because the absence of a central coupling point reduces melt elasticity and cohesive strength. Oil-extended grades contain 25–35 phr of high-boiling paraffinic or naphthenic oil; the oil lowers Shore A hardness and tensile strength while raising melt flow and filler loading capacity. SEBS grades replace the unsaturated butadiene mid-block with ethylene-butylene sequences, removing labile double bonds and improving oxidative service ceilings to 100–120 °C, but reducing compatibility with bitumen and many C5 tackifier systems.

For a non-oil-extended linear SBS such as CH332, tensile strength and Shore A hardness are retained at higher levels than oil-extended grades, but melt viscosity is also higher. In twin-screw compounding, the screw torque at a given throughput is 15–25% higher than that of an oil-extended linear grade with equivalent mid-block molecular weight. The practical consequence is that barrel temperature settings, screw speed, and feeder calibration must be adjusted before switching from oil-extended to non-oil-extended material; otherwise vent plugging and degraded stock may occur.

High-Shear Bitumen Modification, Thermal Limits, and Equipment-Dependent Phase Inversion

On a production-scale polymer-modified bitumen line, CH332-class pellets are added to heated bitumen at 170–190 °C through a weigh-belt or screw side-feeder. A rotor-stator high-shear mill with a tip speed of 18–25 m/s and a recirculation loop through an agitated tank is commonly used. Batch-to-batch variation in mill current draw is a stronger process indicator than temperature alone: as the SBS domain size drops below 10 µm and the polymer-rich phase becomes continuous, apparent viscosity rises and the mill motor load can increase by 15–35%. If phase inversion is incomplete, the modified bitumen shows low elastic recovery and a weak plateau in the dynamic shear rheometer at 60–80 °C under ASTM D7175 or AASHTO T315.

After milling, the finished polymer-modified bitumen is stored at 160–180 °C under low-level agitation. Storage without agitation can lead to phase separation in 24–48 h for some bitumen sources; separation is quantified by the difference in softening point between top and bottom samples after 72 h at 180 °C per EN 13399. A commonly applied release limit is ≤5 °C for binder storage stability, but values for CH332 must be verified on each bitumen supply because maltene composition and asphaltene dispersion state are strong variables.

Thermal exposure beyond 230 °C is an operational boundary for this material class. At such temperatures, chain scission and butadiene double-bond addition can produce gel, which clogs static mixers, filters, and die lines. Nitrogen blanketing of storage tanks and short high-shear residence times are required when bitumen temperature control is poor. Iron and copper contact surfaces should be minimised because transition-metal residues accelerate oxidative degradation.

For dense-graded asphalt mixtures, polymer-modified bitumen based on linear SBS is evaluated by ring-and-ball softening point under EN 1427, penetration under EN 1426 or ASTM D5, elastic recovery under ASTM D6084, and multiple stress creep recovery under AASHTO T350. A well-dispersed linear SBS network commonly raises the softening point by 30–45 °C relative to the neat bitumen at 4–5 wt% polymer loading; the exact increment depends on base bitumen composition and polymer molecular weight. These test protocols allow the influence of CH332 to be separated from the influence of flux oil or crosslinker additions.

Across injection moulding plants, CH332-class linear SBS is melt-compounded with polystyrene or used as a toughening modifier in footwear and appliance compounds. The screw L/D ratio is typically 32:1–40:1, and the barrel temperature profile is held between 150 °C and 190 °C. In impact modification of high-impact polystyrene, SBS addition at 5–15 wt% raises notched Izod impact energy measured under ASTM D256 while reducing tensile modulus under ASTM D638; the exact shift depends on rubber particle size and adhesion between the SBS phase and the matrix. The material is less compatible with polypropylene than SEBS; blends with polypropylene can produce brittle interfaces unless a compatibilizer is used. Pellets stored above 60% relative humidity should be dried at 60–70 °C for 2–4 h before processing. Vent ports under −0.08 MPa vacuum reduce splay in injection-moulded footwear soles produced with clamp forces between 80 t and 150 t and gate diameters between 1.5 mm and 2.5 mm.

In compounds entering footwear soling, the double bonds in the butadiene segment permit sulfur cure. A typical cure system for SBS-based soling compounds uses sulfur at 1.5–2.0 phr, sulfenamide accelerators at 1.0–1.5 phr, zinc oxide at 3.0–5.0 phr, and stearic acid at 1.0–2.0 phr. Cure behaviour is measured on a moving die rheometer at 160 °C according to ISO 6502 or ASTM D5289; the rheometer torque increase indicates the formation of a crosslinked network. This capability distinguishes CH332-class SBS from hydrogenated SEBS, which lacks the same level of unsaturation and is typically not cured without specialty formulations. The curing step also imposes a processing boundary: the melt temperature must remain below the onset of accelerator decomposition and below the point at which chain scission dominates.

Solution adhesive compounding with CH332-class polymer is constrained by gel formation when pellet addition is too rapid. The pellets are fed into a jacketed mixer charged with toluene or a toluene/ethyl acetate blend; a batch at 20–35 wt% solids can reach 4,000–10,000 mPa·s at 25 °C, with viscosity controlled by molecular weight and diblock content. Because the diblock content is below 1.0 wt%, the material should provide higher shear strength and lower tack than diblock-rich SBS; tackifier resins such as C5 hydrocarbon resins or rosin esters are required to generate peel adhesion. The unsaturated butadiene mid-block requires phenolic antioxidant and phosphite co-stabiliser packages. Formulations exposed to ultraviolet light need carbon black or ultraviolet absorbers and should not be specified for long-term clear outdoor service.

For regulatory assessment, CH332 must be evaluated under the EU REACH registration obligations and the RoHS Directive if finished articles are intended for electrical and electronic equipment. Food-contact use requires specific verification under FDA 21 CFR 177.1810 or an equivalent national regulation; no food-contact status is implied solely by the polymer chemistry. Volatile matter, residual styrene monomer, and heavy metal content should be controlled using the manufacturer’s certificate of analysis, because these parameters affect occupational exposure and end-use compliance. No environmental or safety claim is made for CH332 without a lot-specific analysis.