In polypropylene impact modification, Kraton G1726 M is metered into the feed throat of a co-rotating twin-screw extruder with an L/D ratio from 40:1 to 52:1. The powder is supplied as a dusted crumb; when the bulk density is below 0.30 g/cm³, direct flood feeding produces screw-channel starvation at screw speeds greater than 600 rpm. A gravimetric loss-in-weight feeder with side stuffing into barrel zone 4 is therefore specified on compounding lines running above 400 kg/h. Barrel temperature settings begin at 180 °C in zone 1 and ramp to 230 °C at the die plate. Melt temperature measured with an immersion thermocouple at the die should remain between 230 °C and 250 °C; melt temperatures above 260 °C accelerate oxidative scission of the ethylene-butylene midblock, producing gel specks in the strand. Water bath temperature is controlled between 30 °C and 45 °C because rapid quenching below 25 °C fixes the polypropylene crystalline phase before the SEBS domains can relax, reducing impact resistance. The high melt flow of G1726 M — 65 g/10 min at 230 °C/5 kg per ASTM D1238-20 — lowers the viscosity of PP homopolymer from an MFR of 3 g/10 min to a compound MFR between 10 g/10 min and 25 g/10 min at 20 wt% loading. Notched Izod impact measured per ASTM D256-10 at -20 °C shifts from below 5 kJ/m² for the unfilled PP to a reported band of 10–20 kJ/m² at 20 wt% SEBS, depending on PP crystallinity and annealing. Tensile yield stress measured per ISO 527-2:2012 decreases from approximately 32 MPa to 22–24 MPa at the same addition level, and flexural modulus per ISO 178:2019 drops from 1,400 MPa to 900–1,100 MPa. The operational upper bound of 30 wt% is governed by melt-pressure instability in single-screw injection moulding; the lower bound of 10 wt% is set by insufficient phase-separated SEBS particle density to terminate craze propagation. Pre-drying at 80 °C for 2–4 h in a desiccant dryer is required when ambient storage exceeds 60% relative humidity for more than 24 h because surface moisture generates silver streaking in injection-moulded parts. The following test matrix is applied for release evaluation on production batches.

How Does High Melt Flow SEBS Affect Adhesive Formulation Viscosity and Cohesion?

Hot-melt adhesive formulations built on Kraton G1726 M require tackifier resin loadings between 40 wt% and 60 wt% of total formula. Hydrogenated C5 or C9 hydrocarbon resins with ring-and-ball softening points from 95 °C to 115 °C are preferred because aliphatic resins do not homogeneously mix with the EB midblock at process temperatures below 180 °C. The high melt flow of G1726 M lowers Brookfield viscosity at 180 °C to below 10,000 mPa·s in low-polymer formulations. This viscosity window permits slot-die coating at line speeds above 50 m/min without jetting or die-lip build-up. The same high flow reduces shear holding power on nonwoven substrates. Formulators counter the drop in cohesion by reducing paraffinic oil below 15 wt% or by blending in a higher-styrene SEBS grade at 10–20% of total polymer. Mixing is performed under nitrogen in a vertical anchor mixer at 160–190 °C for 60–120 min. Antioxidant packages based on hindered phenols at 0.5–1.0 wt% and phosphite co-stabilizers at 0.2–0.5 wt% are charged before the tackifier addition to suppress viscosity drift. Peel adhesion to untreated polypropylene measured per ASTM D3330/3330M-04 Procedure A at 180° peel typically exceeds 12 N/25 mm only when adhesive coating thickness is controlled above 50 µm. Below that thickness, cohesive failure at the SEBS–resin interface dominates and peel values drop below 8 N/25 mm. Ring-and-ball softening point per ASTM E28-18 remains between 85 °C and 105 °C depending on resin aromaticity. Thermal stability at 180 °C for 72 h should not exceed 20% viscosity change under internal quality protocols. Non-hydrogenated rosin ester tackifiers are not recommended because acid groups catalyze oxidative chain scission in the EB midblock. Published data for specific adhesion to coated polyethylene terephthalate in this configuration is limited; laboratory screening on production-grade corona-treated film is required before scale-up.

In soft-touch injection-moulded compounds for hand-held power tools, Kraton G1726 M is let down with a polypropylene random copolymer and a hydrotreated paraffinic oil to a Shore A hardness between 40 and 70. Oil loading is fixed between 50 phr and 110 phr relative to 100 phr of SEBS. A high-density polyethylene addition of 5–10 phr reduces surface tack and improves mar resistance. The melt is processed in injection moulding machines with clamp forces from 80 t to 120 t for tools with 4–8 cavities. Melt temperature measured at the nozzle is maintained at 190–220 °C. Mold temperature is held between 20 °C and 50 °C. Gate shear heating raises local melt temperature by 10–15 °C; nozzle thermocouple readings alone underreport the thermal load at the gate. Tensile strength measured per ISO 37:2017 falls below 8 MPa when oil loading exceeds 100 phr. Elongation at break remains above 500% at Shore A 50. A compression set under constant deflection per ASTM D395-16e1 at 70 °C for 22 h remains below 35% for Shore A 60 compounds. Oil exudation is the primary long-term failure mode. At oil loadings above 110 phr, paraffinic oil migrates to the part surface within 7–14 days of isothermal storage at 50 °C, producing visible haze on black parts. An erucamide slip additive at 0.2–0.5 wt% reduces blocking but does not prevent internal oil migration. Two-shot overmoulding onto a polypropylene substrate requires the SEBS compound melt temperature not to exceed 220 °C to prevent substrate re-melt and distortion. Published data for specific power-tool case formulations using G1726 M is limited; mould trials are required for gloss and abrasion acceptance.

When Kraton G1726 M is Melt-Blended with Recycled Polypropylene Streams

Post-consumer recycled polypropylene streams exhibit melt flow rates from 5 g/10 min to 30 g/10 min per ASTM D1238-20 and variable filler content depending on collection source. Addition of 10–20 wt% G1726 M to rPP on a co-rotating twin-screw extruder with an L/D ratio of 44:1 reduces melt-flow variation from ±8 g/10 min to ±3 g/10 min in downstream strand pelletizing. The SEBS phase encapsulates residual aluminum foil fragments smaller than 200 µm and stabilizes melt pressure before the strand die. Notched impact at -10 °C improves only when total contaminant content is below 2 wt%. Above that threshold, SEBS encapsulation does not prevent crack initiation from metal or cellulosic inclusions. A melt filter with a 200–500 µm screen pack is installed upstream of the die to prevent hot-runner valve blockage during later injection moulding. Barrel temperatures are held between 210 °C and 240 °C because landfill-derived rPP often contains polyethylene contamination that reduces phase adhesion at melt temperatures above 240 °C. Screw speeds above 500 rpm generate excessive shear heating in the high-viscosity contaminated melt and trigger localized degradation that appears as black specks. The upper addition limit of 20 wt% is set by tensile yield loss per ISO 527-2:2012 below 18 MPa, which is unacceptable for rigid packaging and automotive underhood parts. Published quantitative data for G1726 M in post-consumer rPP from specific collection schemes is limited; pilot-scale trials on a 25 mm co-rotating twin-screw extruder are required to validate mechanical performance and color stability against production specifications.

Halogen-Free Flame-Retardant Cable Jacketing Compounds Based on SEBS

Flame-retardant cable jacketing compounds use Kraton G1726 M as the elastomeric phase at 15–25 wt% of total compound. Magnesium dihydroxide loading at 55–65 wt% limits heat release but raises melt viscosity. The high melt flow of G1726 M partially offsets filler-induced viscosity; extrusion torque remains 20–30% higher than unfilled TPE at 190 °C on a 40:1 L/D twin-screw extruder. Screw configurations require low-shear distributive mixing elements rather than high-shear kneading blocks to prevent filler attrition and surface roughness. Barrel profile should not exceed 210 °C. Although magnesium dihydroxide dehydration begins near 340 °C, localized hot spots above 220 °C can generate steam-induced porosity in the jacket. Limiting oxygen index per ISO 4589-2:2017 reaches 35–40% O₂ at 60 wt% MDH loading. Elongation at break per DIN 53504:2017 falls below 150% when filler exceeds 65 wt%, which is the practical upper filler boundary for cable flexibility. Smoke density testing per IEC 61034-2:2019 and acid gas emission per IEC 60754-1:2011 are specified for halogen-free jacketing grades; the compound is not self-certifying against these standards without final formulation verification. A maleated polypropylene coupling agent at 0.5–1.5 wt% improves the filler–matrix interface and reduces water uptake after immersion in 80 °C water for 7 days to below 5 mg/cm² in internally monitored trials. Published data for specific G1726 M jacketing formulations is limited; full-scale cable extrusion trials on a 90 mm single-screw extruder with a pressure-controlled crosshead are required to establish surface finish and concentricity. The grade is not recommended for direct skin contact or medical cable applications unless additional biocompatibility testing under ISO 10993-1:2018 is completed.