Product designation Ningbo Keyuan SBS KY1401H identifies a linear styrene-butadiene-styrene triblock copolymer supplied in porous white pellet form. The 1401 series nomenclature is associated in thermoplastic elastomer trade literature with a nominal styrene mass fraction of 40 wt%, while the butadiene midblock retains a mixed microstructure of 1,4-cis, 1,4-trans, and 1,2-vinyl units. The unsaturation in the midblock reduces resistance to UV, ozone, and long-term thermo-oxidative ageing compared with hydrogenated styrenic block copolymers, but it also provides the double-bond character used in some vulcanisable and bitumen-modified systems. At ambient temperatures the material behaves as a crosslinked rubber because the polystyrene endblock domains are below their glass transition, which for SBS of this composition is commonly reported between 90 °C and 100 °C by ISO 11357-2 differential scanning calorimetry. Published data for the specific KY1401H producer certificate are limited in the public domain, so the class-typical ranges described in this document must not be substituted for a lot-specific certificate of analysis. Typical values for 1401-type linear SBS tested according to ISO 37:2017 include tensile strength between 18 MPa and 22 MPa and elongation at break between 700% and 900%. Hardness measured by ISO 48-4 is typically reported from 80 to 86 Shore A. Melt mass-flow rate for such grades is frequently reported between 0.5 g/10 min and 2.0 g/10 min under ISO 1133-1:2022 conditions of 200 °C and 5 kg load. Such values define a class envelope, not a certified KY1401H specification.

Specification envelope and thermal analysis methods for KY1401H

Lot-to-lot conformity is normally assessed on compression-moulded sheets conditioned at 23 °C and 50% relative humidity for 24 h before physical testing. Tensile stress-strain data are obtained under ISO 37:2017 or ASTM D412-16 at a crosshead speed of 500 mm/min, using Type 1 dumbbell specimens. The melt mass-flow rate is measured by ASTM D1238-20 or ISO 1133-1:2022 after purging to avoid oxidative residence. Hardness is determined on a specimen of at least 6 mm thickness according to ISO 48-4 or ASTM D2240-15, with a 15 s reading after indenter contact. Density is measured by water displacement or gas pycnometry following ISO 1183-1:2019 or ASTM D792-20. The specification table below presents class-typical data for unsaturated linear SBS grades with 40 wt% styrene; KY1401H may exhibit tighter or shifted windows depending on the producer’s current production technology.

The above values are derived from published class data, not from a controlled interlaboratory study on KY1401H. End users should request a producer certificate of analysis and, when possible, compare incoming lots against retained reference samples under ISO 2859-1 sampling plans. The primary difference between KY1401H and lower-styrene linear SBS grades is the hard-block fraction. In classification systems for 1401-type materials, a styrene mass fraction near 40 wt% produces a higher Shore A hardness and elastic modulus than grades near 30 wt% styrene but lowers low-temperature flexibility. Conversely, a higher-styrene grade above 45 wt% styrene tends to increase modulus but may reduce melt flow at a given molecular weight. These comparisons are class-based, not specific to KY1401H lot data.

What limits melt-processing stability in linear unsaturated SBS at low screw speeds?

In melt-compounding operations, the limiting factor is rarely plastication but rather thermo-oxidative chain scission and crosslinking in the unsaturated midblock. For a co-rotating twin-screw extruder with an L/D ratio of 40:1, linear SBS grades of this type are generally processed with barrel set-points from 150 °C to 180 °C and a die temperature not exceeding 190 °C. Higher melt temperatures, especially at high shear and low screw speed, extend residence time and accelerate double-bond oxidation, resulting in gel formation, yellowing, and a reduction in tensile elongation. The porous pellet structure equilibrates with ambient humidity; in manufacturing areas with relative humidity greater than 60%, pre-drying at 60 °C to 70 °C for 2 h to 3 h in a forced-air dryer is advisable to reach a residual moisture level below 0.1 wt%. Drying above 80 °C for extended periods may soften the pellet and cause a lumpy feed. Processing stabilisation packages are normally included, but additional hindered phenolic antioxidant at 0.1–0.3 wt% may be incorporated if high regrind ratios exceed 20 wt%. Direct mixing with strong oxidising agents, transition metal stearates, or high-acid-number fillers should be avoided because these species catalyse midblock oxidation. The non-Newtonian shear-thinning behaviour of linear SBS requires capillary rheometry data for die sizing; published apparent viscosity data are limited, so a rheology test at the intended shear rate is necessary for robust tool design.

In injection moulding, gate dimensions and clamp capacity are matched to the melt viscosity rather than to solid-state hardness. Vertical clamp units with a shot size of 60% to 80% of barrel capacity reduce hold-up and reduce thermal history. Mould temperatures between 20 °C and 40 °C are sufficient for rapid setup of the polystyrene endblocks. After demoulding, dimensional stabilisation proceeds by endblock vitrification; final hardness values are reached after 24 h of storage at 23 °C and should be measured by ISO 48-4. Shrinkage under ISO 294-4 should be determined on a standard plaque because anisotropic flow orientation in the butadiene phase controls dimensional change. Published data for KY1401H injection-moulded shrinkage are limited.

In polymer-modified bitumen, the SBS phase absorbs maltenes while the polystyrene endblock domains remain associated, producing a continuous elastic network that raises softening point and elastic recovery. For 1401-type linear SBS, addition levels of 3–5 wt% based on total bitumen are common in paving-grade binders, whereas waterproofing membranes may employ 6–8 wt% to meet low-temperature flexibility requirements. The actual solubility and swelling of KY1401H in a specific bitumen depend on asphaltene content and maltene aromaticity, so pilot trials are required. A high-shear rotor-stator mixer operating at 180–190 °C for 45–90 min disperses the pellet into a penetration-grade or oxidised bitumen; after dispersion, low-shear agitation at 160–170 °C limits phase separation. Modified binders are evaluated for softening point under ASTM D36, penetration under ASTM D5, elastic recovery under ASTM D6084, and storage stability under ASTM D7173. The European specification EN 14023:2010 and performance-graded binder specification ASTM D6373 or AASHTO M320 provide comparative frameworks. Published data for KY1401H in a specific bitumen formulation are limited; therefore the addition level and mixing time must be established on the production bitumen lot rather than transferred from published 1401-series data.

When linear SBS replaces SIS in hot-melt pressure-sensitive adhesive systems

Selecting a linear SBS such as KY1401H instead of a styrene-isoprene-styrene block copolymer generally shifts the adhesive balance toward higher cohesive strength and elevated-temperature shear resistance, but reduces initial tack and may require a more aggressive tackifier system. A typical hot-melt formulation may contain 100 phr SBS, 100–125 phr rosin ester or C5 tackifier, 20–40 phr naphthenic oil, and 0.5–1.0 phr hindered phenolic antioxidant. Mixing is conducted in a horizontal sigma-blade mixer at 160–180 °C under inert gas or in a twin-screw extruder with a short feed section. Adhesive performance is measured by loop tack under ASTM D6195, 180° peel under ASTM D3330, and shear adhesion failure temperature under ASTM D4498. The unsaturated butadiene midblock has a lower glass transition than isoprene, but the molecular mobility and entanglement characteristics differ; as a result, formulations formulated with SBS often require higher tackifier addition to approach the surface tack of an SIS system. SEBS, by comparison, has a saturated midblock and improved thermo-oxidative stability but typically requires higher processing temperatures and synthetic or fully saturated tackifiers to achieve comparable compatibility. Published data specific to KY1401H in hot-melt adhesives are limited; benchmark formulation work is necessary before commercial substitution.

Compounding of KY1401H with polystyrene, polypropylene, or ethylene-vinyl acetate is used to improve impact strength, reduce brittleness, or add low-temperature flexibility. In polystyrene blends, addition of 10–30 wt% SBS increases notched Izod impact strength measured under ISO 180:2023 or ASTM D256-23, but reduces tensile modulus and heat deflection temperature. Calcium carbonate filler at 20–40 wt% raises modulus, while oil extension with naphthenic oil at 30–50 phr reduces hardness by 10–20 Shore A points in compression-moulded test sheets. The resulting two-phase morphology is sensitive to mixer speed and temperature during compounding; a high-shear mixer or twin-screw extruder with medium screw severity disperses the filler without destroying the polystyrene domain structure. Morphological change can be monitored by dynamic mechanical analysis according to ISO 6721-1, with the loss tangent peak of the polybutadiene midblock used as an indicator of phase integration. In footwear soling, the compound is often injection moulded with a material temperature below 190 °C and a mould temperature below 40 °C. Slip resistance and abrasion resistance are application-specific and must be tested under the relevant footwear standards, such as ISO 4643 for moulded footwear or ASTM D1630 for abrasion of rubber. Published data for KY1401H in these specific filled compounds are limited.

Because the unsaturated midblock is susceptible to ozone and ultraviolet degradation, finished articles intended for outdoor service should include UV stabilisers or be protected by an opaque surface layer. Continuous service in air above 70–80 °C may cause progressive hardening as a result of oxidative crosslinking, and dynamic fatigue under repeated strain should be evaluated by ASTM D7791. When direct food-contact status is required, the converter must establish compliance with 21 CFR 177.1640 or 21 CFR 177.2600 under the intended use conditions, because the supplier’s REACH registration and RoHS 2 Directive 2011/65/EU Annex II declarations apply to the polymer as supplied and do not transfer unchanged after compounding. Low-molecular-weight additives, residual monomers, and processing oils migrate under end-use thermal history and should be assessed by migration testing under ISO 10106-1 or the applicable food-contact method. The product is not intended for implantable medical use, and no USP Class VI or ISO 10993 biological evaluation should be inferred without specific qualification.