Kraton Kraton™G SEBS G1643 M
- Product Name: Kraton Kraton™G SEBS G1643 M
- Factroy Site: Yinchuan, Ningxia, China
- Price Inquiry: sales8@ascent-chem.com
- Manufacturer: Ascent Petrochem Holdings Co., Limited
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- Kraton Kraton™G SEBS G1643 M is typically used in formulations when hardness, tensile strength, and melt flow and processing temperature and shear rate must be controlled within specific ranges.
| HS Code | 344584 |
| Polymertype | SEBS linear triblock copolymer |
| Physicalform | Powder |
| Styrenecontent | 20 wt% |
| Density | 0.91 g/cm3 |
| Bulkdensity | 0.40 g/cm3 |
| Meltflowrate | 3 g/10 min (230 °C/2.16 kg) |
| Shoreahardness | 65 Shore A |
| Tensilestrength | Approximately 22 MPa |
| Elongationatbreak | Approximately 500% |
| 300percentmodulus | Approximately 3.0 MPa |
| Solutionviscosity | Approximately 1,200 mPa·s (25% in toluene at 25 °C) |
| Volatilematter | <0.5 wt% |
| Ashcontent | <0.1 wt% |
As an accredited Kraton Kraton™G SEBS G1643 M factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Kraton™ G SEBS G1643 M is supplied in 25 kg moisture-resistant paper bags, palletized for industrial handling and storage. |
| Container Loading (20′ FCL) | Kraton™G SEBS G1643 M is palletized, shrink-wrapped, and securely loaded into a 20′ FCL container for ocean shipment. |
| Shipping | Kraton™ G SEBS G1643 M is shipped as a non-hazardous solid polymer in sealed moisture-barrier bags or boxes on pallets. It has no UN number and is not regulated under DOT, IMDG, or IATA. Store dry at ambient temperature, protect from heat and direct sunlight, and follow the SDS. |
| Storage | Store Kraton™G SEBS G1643 M in a cool, dry, well-ventilated area away from direct sunlight, heat, ignition sources, and strong oxidizing agents. Keep containers tightly closed and clearly labeled. Protect from moisture, dust, and contamination. Avoid prolonged high-temperature exposure. Use appropriate housekeeping and PPE; clean pellet spills promptly because they may create slip hazards. |
| Shelf Life | Kraton G1643 M has a shelf life of 2 years when stored dry in its original sealed packaging at ambient conditions. |
For non-PVC medical film and tubing compounds running on high-shear co-rotating twin-screw compounding lines, the substitution of liquid PVC plasticizers with Kraton G1643 M-based elastomer systems introduces a measurable shift in torque, melt pressure, and extractables profile. All addition ratios in this section are mass fractions of the total compound. Kraton G1643 M, a linear triblock SEBS with a bound styrene mass fraction near 20 wt%, is typically incorporated at 25–40 wt% alongside a random propylene copolymer at 15–30 wt%, medical white mineral oil at 20–35 wt%, hindered phenolic antioxidant at 0.05–0.2 wt%, and a non-migrating process lubricant at 0.5–2 wt%. The compliance matrix spans ISO 10993-5:2009 for cytotoxicity, ISO 10993-10:2010 for skin sensitization and irritation, ISO 10993-11:2017 for systemic toxicity, ISO 10993-4:2017 for hemocompatibility, and USP <88> Class VI for systemic injection and intracutaneous testing. On the production floor, the compound is processed on a co-rotating twin-screw extruder with an L/D ratio of 40:1, barrel temperatures from 180°C to 210°C, atmospheric venting at the L/D 22–26 position, and vacuum devolatilization at −0.08 MPa to −0.095 MPa across the final two barrel zones to pull residual moisture and low-molecular-weight oils from the melt. The melt is pelletized underwater at 35–45°C and then converted by a single-screw extruder with a barrier screw design into monolayer blown or cast film at die temperatures between 190°C and 205°C, or into micro-extrusion tubing with a 1.0–4.0 mm outer diameter and wall thickness controlled to ±0.05 mm. Terminal product types include enteral feeding tubes, peristaltic pump tubing, wound drainage conduits, portable oxygen delivery tubing, and flexible medical packaging film. Operating limitations include pre-drying at 70–80°C for 2–4 h when warehouse relative humidity exceeds 60%, avoidance of steam autoclave temperatures above 121°C for load-bearing components due to creep-induced dimensional change, and validation of post-gamma sterilization yellowing at 25–40 kGy because SEBS can undergo oxidative discoloration without sufficient phenolic-phosphite stabilization.
| Test | Standard designation | Typical acceptance criterion |
|---|---|---|
| Cytotoxicity | ISO 10993-5:2009 | ≤ grade 2 |
| Irritation and sensitization | ISO 10993-10:2010 | no erythema or edema above grade 1 |
| Hemolysis | ISO 10993-4:2017 | ≤ 5% hemolysis |
| Systemic toxicity | ISO 10993-11:2017 | no mortality; no significant clinical signs |
| Class VI | USP <88> | no systemic toxicity |
Hot-Melt Adhesive Rheology and Elastic Strand Failure: Where Does the Formulation Window Narrow?
The formulation window for styrenic block copolymer-based assembly and elastic attachment adhesives is constrained on the low-viscosity end by strand sag and on the high-viscosity end by pump cavitation in gear-driven hot-melt transfer systems. Kraton G1643 M is added at 15–35 wt% of the adhesive formulation, with hydrogenated tackifying resin at 35–55 wt%, paraffinic or naphthenic process oil at 15–30 wt%, and stabilizer package at 0.5–1.5 wt%. The adhesive system is mixed in a jacketed sigma-blade kneader or continuous twin-screw compounder at 160–180°C under nitrogen to limit carbonyl formation, then transferred to a slot-die coating head or multi-roll applicator maintained at 150–165°C. Conformance testing draws on ASTM D3236 for apparent viscosity at 175°C, ASTM D1876 for 180° T-peel adhesion to polyethylene film, ASTM D4498 for heat-fail temperature under shear, and ASTM D638-14 for tensile set of cast free films. For disposable hygiene elastic attachment, the compound must retain strand elasticity during high-speed lamination at line speeds above 200 m/min; a modulus drop below 0.8 MPa at 37°C typically produces finished laminate creep in diaper waistbands. Terminal products include disposable diaper leg and waist elastic attachment, mattress foam assembly, filter frame bonding, and repositionable industrial tapes. Published data for this specific configuration is limited with respect to long-term oxidative aging under nonwoven contact, so validation should include 70°C forced-air aging for 168 h with viscosity change measured per ASTM D4498. The main operational incompatibility is with strong polar ester plasticizers and low-molecular-weight acrylate tackifiers, which partition into the styrene domains and reduce the upper service temperature of the bonded assembly.
Because soft-touch overmolding compounds based on Kraton G1643 M reach their adhesion limit when the thermoplastic substrate surface temperature drops below the styrene block glass transition temperature of approximately 95°C, molders run insert and two-shot tools with oil-heated core pins and avoid mold temperatures below 20°C or above 60°C. A compound formulated with 30–50 wt% Kraton G1643 M, 15–35 wt% polypropylene random copolymer, 15–30 wt% white mineral oil, and up to 10 wt% calcium carbonate or talc is first compounded on a twin-screw extruder at 190–220°C and pelletized. The compound is then fed into a two-shot injection molding machine with a clamp force sufficient to maintain a cavity pressure of 35–55 MPa during second-shot packing. For polypropylene and polyethylene substrates, adhesion is primarily interdiffusion-driven; for polyamide and polycarbonate substrates, surface treatment with plasma or a compatibilizer tie-layer is required, otherwise peel failure occurs at the interface at values below 2.0 N/mm when tested on a universal tensile tester with a 90° peel fixture at a crosshead speed of 50 mm/min. Compliance for consumer and power tool applications typically cites RoHS Directive 2011/65/EU for hazardous substance restrictions, REACH Regulation (EC) No 1907/2006 for substance registration, and ASTM D2240 for Shore A durometer target ranges between 30 A and 65 A. Terminal products include power tool housings, hand tool grips, personal care device bodies, remote control shells, and toothbrush handles. The main process conflict arises when mold surface temperatures exceed 70°C because the unvulcanized SEBS network undergoes melt relaxation and the overmolded layer delaminates during demolding; conversely, below 10°C ambient storage after molding, the compound can exhibit a temporary hardness increase of 5–8 Shore A points due to polystyrene domain reinforcement, requiring conditioning at 23°C for 24 h before durometer measurement.
When SEBS Acts as a Polypropylene Impact Modifier Under High-Speed Puncture
In polypropylene homo- and random-copolymer matrices, the incorporation of Kraton G1643 M at 5–15 wt% shifts the brittle-ductile transition and reduces the sharpness of crack propagation under notched and high-speed puncture loading. The blend is prepared by either dry blending pellets with a twin-screw feeder or side-feeding the SEBS downstream of the PP melt zone, using a corotating extruder with an L/D ratio of 36:1 to 44:1, barrel temperatures of 200–235°C, and a screw speed of 400–650 rpm depending on torque limitations. The relevant property tests are ISO 180/A notched Izod impact at 23°C and −20°C, ASTM D3763 instrumented puncture at 1.0 m/s, and ISO 1133-1:2022 melt mass-flow rate to verify that the modified resin remains above 5 g/10 min. Below 5 wt% SEBS addition, the low-temperature notched impact improvement is often below 20%; above 15 wt%, tensile modulus in ISO 527-2:2012 drops by more than 30%, and the continuous PP phase can transition to a co-continuous morphology that reduces thermoformability. Terminal products include freezer-grade food containers, appliance housings, automotive interior trim, crates, and thin-wall food packaging. Compliance statements for these applications are anchored to EU No 10/2011 for plastic food-contact migration, FDA 21 CFR 177.1520 for olefin polymers when the PP fraction governs food-contact, and FDA 21 CFR 177.1810 for styrene block polymers when the SEBS domain is present at the food-contact surface. Published data for this specific configuration is limited, particularly for instrumented puncture at −20°C on 0.8 mm injection molded plaques, so internal validation against a control PP lot is required before release to mass production.
Food-Contact Seal Durometer Stability Under Retort and Microwave Cycling
Sealing components for food-contact closures and kitchen appliances operate under intermittent compressive stress at temperatures that range from −20°C freezer storage to 121°C retort cycles. Compounds for these seals contain Kraton G1643 M at 20–40 wt% with polypropylene or high-density polyethylene at 20–40 wt%, white mineral oil at 10–25 wt%, and optional precipitated calcium carbonate at 5–15 wt% to raise compression modulus without exceeding Shore A 60. The compounding process uses a corotating twin-screw extruder at 185–215°C with a downstream side-stuffer for filler to prevent barrel wear, followed by underwater pelletizing at 30–40°C and drying to a moisture content below 0.05 wt% before injection molding. Seals are molded on a single-stage injection machine with a melt temperature of 190–220°C, holding pressure of 30–50 MPa, and mold surface temperature of 20–50°C. Conformance references FDA 21 CFR 177.1810 for styrene block polymers, EU No 10/2011 with overall migration below 10 mg/dm², and ASTM D395-18 compression set at 70°C for 22 h. Terminal products include bottle cap liners, blender jar gaskets, food storage container lids, infant feeding accessory seals, and reusable coffee cup sealing rings. A critical boundary is prolonged contact with high-fat food above 100°C, where oil migration from the SEBS phase can increase surface tack and alter seal release forces; repeated microwave use should be limited to intermittent exposure rather than continuous 150°C hot oil contact.
Flexible cable jacket compounds formulated with Kraton G1643 M are processed on wire coating lines where the limiting parameter is not melt temperature alone but the ratio of drawdown tension to melt strength at the die exit. The compound contains 25–45 wt% SEBS, 15–30 wt% polypropylene or linear low-density polyethylene, 10–25 wt% paraffinic oil, 15–35 wt% magnesium hydroxide or aluminum trihydrate flame retardant, and 0.5–2 wt% processing stabilizer. Compounding is performed on a 44:1 L/D twin-screw extruder with side-feeding of flame-retardant filler at L/D 26, melt temperatures of 180–210°C, and a downstream gear pump to damp pressure pulsation before strand pelletizing. Cable extrusion then uses a barrier screw single-screw extruder with a 20:1 compression ratio, a crosshead die temperature of 190–215°C, and a water trough temperature of 20–40°C to prevent micro-void formation. Relevant standards are IEC 60227 for flexible cable dimensions and voltage ratings, UL 62 for flexible cord and fixture wire constructions, and ASTM D2863 for limiting oxygen index above 30% in flame-retardant compounds. Terminal products include industrial robot drag-chain cable jackets, power tool cord sheaths, appliance cord jackets, and data cable outer sheaths. Published data for this specific configuration is limited with respect to dynamic flex fatigue at bend radii below 5× cable diameter; end-use qualification should therefore include a wire-bend test of no fewer than 10,000 cycles under −20°C low-temperature flex conditions. The compound should not be combined with antimony trioxide-brominated flame-retardant systems in high-UV exposure environments unless a high-molecular-weight hindered amine stabilizer is added at 0.5–1.0 wt%, because the styrenic domains can undergo photo-oxidative chain scission at the jacket surface.
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- Kraton Kraton™G SEBS G1643 M is manufactured under an ISO 9001 quality system and complies with relevant regulatory requirements.
- COA, SDS/MSDS, and related certificates are available upon request. For certificate requests or inquiries, contact: sales8@ascent-chem.com.
Kraton™ G1643 M is a linear triblock copolymer composed of styrene end-blocks and a hydrogenated ethylene/butylene midblock. Bound styrene content is 20% by mass, and specific gravity is 0.91 g/cm³ measured under ASTM D792-20. The product is supplied as dense pellets. Melt volume-flow rate is determined under ISO 1133-1:2022 at 230 °C with a 5 kg load; because this is a lot-specific value, the certificate of analysis must be consulted before machine settings are fixed. The saturated midblock provides resistance to oxidative degradation and ultraviolet light in exposed applications, but at the expense of a higher processing window than unsaturated styrene-butadiene-styrene block copolymers. Kraton™ G1643 M is used in medical device compounding, flexible tubing, film, low-hardness seals, and impact modification. The polymer forms a thermoreversible physical network through polystyrene domains, so it can be reprocessed without the scorch and irreversible network breakdown associated with vulcanized elastomers.
At ambient temperature, the morphology consists of glassy styrene domains dispersed in a continuous ethylene/butylene matrix. The lower styrene mass fraction relative to 30% styrene SEBS grades produces a lower rubbery plateau modulus and a softer tactile response. This structural difference creates a useful position between very soft polyolefin plastomers and high-styrene SEBS materials. However, mechanical integrity declines as the styrene domains soften; sustained-load applications must be evaluated above 70 °C, where creep is dominated by the onset of domain relaxation.
Flexible PVC replacement is one of the principal applications. In tubing formulations, Kraton™ G1643 M is compounded with polypropylene, mineral oil, and a nucleation agent to balance kink resistance, hardness, and extraction resistance. The saturated midblock does not require the same stabilizer package as unsaturated butadiene-based block copolymers, but downstream additives such as oils and tackifiers still govern long-term oxidative stability.
Where Does 20% Bound Styrene Position Kraton™ G1643 M Relative to 30% Styrene SEBS Grades?
Lower bound styrene reduces the glassy domain volume fraction, which lowers Shore A hardness, tensile strength at break, and 300% modulus when measured under ASTM D638-14 and ASTM D2240-15. Elongation and low-temperature flexibility are generally improved. This places Kraton™ G1643 M in applications where conformability, clarity, and low modulus are more important than load-bearing resistance. In comparison, Kraton™ G1650 M and Kraton™ G1652 M at 30% bound styrene provide higher tensile strength and better retention of shape under load, but they require higher processing temperatures and exhibit higher hardness.
Melt viscosity of Kraton™ G1643 M is lower at equivalent shear rate than high-molecular-weight or higher-styrene SEBS grades. This improves cavity filling in multi-cavity injection molds and allows higher screw speeds in extrusion without excessive melt pressure. The lower viscosity also reduces orientation stresses in thin-wall tubing and film, which can improve dimensional stability after reheating. Conversely, melt strength in blow molding is lower, and parison sag may occur in large-part blow molding unless a higher-viscosity grade or polyolefin modifier is included.
Film and tubing extrusion lines running Kraton™ G1643 M require a barrier screw with a length-to-diameter ratio of at least 24:1 and a compression ratio of 2.5:1 to 3.5:1. Melt temperature at the adapter should be held at 200–220 °C to maintain clarity and avoid flow instabilities. Draw-down and melt strength are lower than those of high-styrene or high-molecular-weight SEBS; therefore, vertical blown-film lines should use low draw ratios and an air ring with low pressure.
In co-rotating twin-screw compounding of unfilled Kraton™ G1643 M, barrel temperatures are typically profiled from 160 °C in the feed zone to 210 °C at the die. Melt temperature should be maintained below 240 °C, with brief excursions not exceeding 260 °C. Above that temperature, thermo-oxidative degradation of the saturated midblock can form gel particles and increase yellowing. A screw configuration with distributive mixing elements and an L/D ratio of 32:1 to 48:1 is generally suitable; excessive intensive kneading elements can create local temperature spikes. If the material is stored at relative humidity above 60%, pre-drying at 80 °C for 2–4 h in a dehumidified hopper dryer is recommended to prevent moisture-induced surface porosity.
Oil extension is a common modification. White mineral oil is metered into the melt after the softening zone to prevent screw slip. Addition levels of 10–50 phr lower hardness and melt viscosity; above 100 phr, tensile properties decline sharply unless the formulation contains polypropylene or end-block reinforcing resin. Stabilization with hindered phenol and phosphite antioxidants at 0.1–0.3% by mass is typical for melt stability and color retention. Batch-to-batch variance in melt flow and color is controlled by raw material feed accuracy and screw temperature profiles rather than vulcanization kinetics, because the polymer does not contain cure systems.
Polypropylene is added at 10–30% by mass to raise upper service temperature and tensile stiffness. Blends of Kraton™ G1643 M with polypropylene can display a co-continuous morphology at intermediate compositions; the exact phase inversion depends on viscosity ratio and screw mixing. Such blends are used in medical device housings and instrument grips.
If a Flexible Component Is Subjected to 121 °C Steam Sterilization
Steam autoclave exposure at 121 °C subjects the styrene domains to near-transition conditions, and unstiffened Kraton™ G1643 M may creep under sustained load. Parts that are sterilized in an unstressed condition generally retain dimensions, but load-bearing geometries require compounding with polypropylene, a higher-styrene block copolymer, or mineral filler. Multiple cycles at 121 °C or exposure above 134 °C should be validated for surface tack and discoloration. The saturated midblock is more resistant to oxidative degradation than SBS, but autoclave ageing can still generate polar oxidation products at the surface and shift extractables.
Gamma irradiation should be assessed under ISO 11137. The ethylene/butylene midblock has lower sensitivity to radiation-induced chain scission than a butadiene midblock, but additive composition governs color shift and extractables. Ethylene oxide sterilization is generally compatible; residual ethylene oxide levels in thick sections must be measured under ISO 10993-7. Cytotoxicity testing of the final compound should follow ISO 10993-5. Because these tests are compound-specific, published data for this specific polymer in final device configurations is limited, and each sterilized article must be validated.
Because the ethylene/butylene midblock is saturated, hot-melt formulations based on Kraton™ G1643 M show lower tendency toward thermal degradation and UV yellowing in adhesive and sealant processing than SIS or SBS. The polymer is compatible with aliphatic and cycloaliphatic hydrocarbon tackifiers; aromatic-modified resins can be added at limited concentrations to increase peel strength. Peel adhesion is measured under ASTM D903 or ASTM D1876; loop tack is measured under ASTM D6195. The low styrene content produces low cohesive strength, so pressure-sensitive adhesive formulations may require endblock reinforcing resin to prevent adhesive transfer. Plasticizer selection should avoid polar esters and phthalates that are incompatible with the saturated midblock and can exude over time.
In hot-melt mixing, temperatures of 180–200 °C are common; nitrogen blanketing reduces oxidative degradation during long batch cycles. Aliphatic oil is added at 10–50 phr to control application viscosity and softness. At higher oil loadings, oil bleed and a rapid reduction in shear adhesion can occur. The polymer is also used in clear sealants because the styrene domains are small and melt clarity is high when crystalline waxes and high-polarity resins are excluded.
Extractables, Migration, and Regulatory Verification in Medical-Grade Compounding
The extractables profile of a final compound is controlled by low-molecular-weight additives as well as the base polymer. Kraton™ G1643 M is supplied under controlled packaging protocols, but no generic polymer certification can substitute for final-device testing under ISO 10993-12. Biological reactivity is frequently assessed using USP Class VI protocols and ISO 10993-5 cytotoxicity. Food-contact suitability may be evaluated under FDA 21 CFR 177.2600 for rubber articles; formulators must confirm that the oil, tackifier, and stabilizer package also meet the relevant end-use conditions. Compliance under REACH and RoHS 2011/65/EU should be verified on the supplied formulation, because the producer cannot control downstream additives.
Migration kinetics in polymer matrices depend on molecular weight distribution, plasticizer content, sterilization, and storage temperature. Accelerated ageing at 40 °C and low relative humidity is not sufficient to predict migration in humid clinical storage environments. A bracketing study across proposed formulation versions is therefore used to set acceptance limits for extractables and leachables.
Under high-shear injection molding conditions, Kraton™ G1643 M can show gate blush and surface streaks if the melt temperature is below 190 °C or if injection speed is too high for the runner diameter. Cold-runner tools with gate diameters of 0.8–1.5 mm reduce shear heating and permit lower injection pressure. Hot-runner manifolds are acceptable when residence time is below 2 min and temperature variation is within ±5 °C. Mold temperature is usually set between 25 °C and 50 °C; higher values improve surface gloss but extend cooling time. Clamp force requirements are moderate because the melt viscosity is low, but pack pressure should be limited to avoid overpacking and gate-stringing.
Nozzle drool and die-face buildup have been reported in production when melt temperature is maintained above 230 °C for extended periods. The polymer is shear-thinning, so capillary rheometry under ISO 11443 is needed to predict filling pressure; melt flow values alone do not capture the shear-rate dependence. After hot shutdowns, purging with polypropylene or a commercial purging compound is used to remove degraded polymer from the screw and hot-runner channels.
What Separates a Linear Low-Styrene SEBS from Unsaturated SBS and Crosslinked TPV?
SBS triblock copolymers contain unsaturated butadiene midblocks that are vulnerable to ozone and thermo-oxidative attack. Kraton™ G1643 M is hydrogenated to an ethylene/butylene midblock, which removes allylic unsaturation and improves weathering and thermal stability. Compared with a crosslinked thermoplastic vulcanizate, the styrenic block copolymer network is thermoreversible; no vulcanization kinetics or peroxide/sulfur cure system is required, and regrind can be reused in noncritical applications after property verification. The trade-off is lower ultimate tensile strength and lower compression-set resistance at elevated temperature. Compression set is evaluated under ASTM D395-18 at 23 °C and 70 °C. In hydrocarbon fluid service, the SEBS network may swell; a fluoropolymer or a crosslinked elastomer system should be selected when resistance to aggressive fluids is the dominant requirement.
