Hot-melt pressure-sensitive adhesive compounding with linear SIS 2600 starts with a pelletized triblock feedstock having a styrene mass fraction near 26 wt% and a melt flow rate reported under ISO 1133-1:2022 at 200 °C/5 kg in the range of 8 g/10 min to 15 g/10 min. The triblock structure supplies elastic recovery because the styrene end-blocks form a physical network at service temperatures below 95 °C, while the isoprene midblock provides tack when compounded with C5 hydrocarbon tackifier resins. Compounding is performed on a co-rotating twin-screw extruder with an L/D ratio between 40:1 and 64:1. Barrel temperatures are set at 150 °C to 170 °C in the feed zone, 170 °C to 185 °C in the mixing zone, and 160 °C to 170 °C at the discharge. Residence time is limited to 45 s to 90 s because prolonged exposure above 190 °C accelerates thermo-oxidative chain scission of the isoprene block. A stabilizer package is added at the feed throat using 0.3 phr to 0.8 phr of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and 0.2 phr to 0.5 phr of tris(2,4-di-tert-butylphenyl)phosphite. Nitrogen blanketing of the feed hopper is maintained when ambient relative humidity exceeds 60 % to avoid moisture-induced void formation in the melt.

A starting formulation for removable label adhesive uses SIS 2600 at 100 phr, a hydrogenated C5 aliphatic tackifier with a softening point of 95 °C to 105 °C at 80 phr to 120 phr, white mineral oil at 20 phr to 40 phr, and the stabilizer package at 1.0 phr total. Increasing the tackifier from 80 phr to 120 phr raises loop tack and lowers static shear resistance. The opposite shift occurs when the oil is raised from 20 phr to 40 phr. This trade-off is quantified by ASTM D6195 loop tack, ASTM D3330/D3330M peel adhesion, and ASTM D3654/D3654M static shear on stainless steel. Published data for linear SIS grades with 26 wt% styrene report peel values of 4 N/25 mm to 12 N/25 mm on stainless steel after 24 h dwell. Static shear failure at 1 kg load generally moves from below 2 h to above 48 h when tackifier loading is reduced from 120 phr to 80 phr. The same formulation is checked for cold flow by measuring dimensional change on a 50 °C slit plate over 7 days. High oil levels above 40 phr are not used for permanent packaging tapes because they produce excessive cold flow and edge bleed.

Slot-die coating of the compounded adhesive is carried out at 160 °C to 180 °C with a coat weight window of 15 g/m² to 50 g/m² on siliconized release liner. The coated web is chill-set on a roll held at 10 °C to 20 °C before transfer to facestocks. Suitable facestocks include corona-treated BOPP, PET film, and machine-finished kraft paper. Line speeds vary from 150 m/min to 400 m/min depending on die gap and coat weight. Foaming is suppressed by maintaining melt pressure above 5 MPa at the die inlet. For food packaging label stock, the adhesive must satisfy FDA 21 CFR 175.105 indirect food-contact adhesive requirements and REACH Article 33 communication requirements if an SVHC substance is present above 0.1 wt%. The formulated adhesive is also screened against RoHS 2011/65/EU Annex II restricted substances. End products include pressure-sensitive labels, carton sealing tapes, masking tapes, and low-tack protective films for automotive transit protection.

When Does Solvent-Borne Spray Adhesive Based on SIS 2600 Pass REACH and IMO/MED Compliance Screening?

The dissolution step is carried out in a jacketed high-shear dissolver equipped with a condenser and a nitrogen purge. A solvent blend of methylcyclohexane, ethyl acetate, and isoparaffin is charged first. SIS 2600 is added at a concentration of 18 wt% to 28 wt% total solids. The polymer is dissolved at 45 °C to 60 °C under agitation speeds of 300 rpm to 800 rpm. Tackifier resin is introduced after the polymer has completely dissolved to avoid lumping. A typical formulation is SIS 2600 at 100 phr, glycerol ester of hydrogenated rosin at 70 phr to 110 phr, naphthenic oil at 10 phr to 30 phr, and antioxidant at 1.0 phr. Final viscosity is controlled to 500 mPa·s to 2,500 mPa·s at 25 °C measured by Brookfield viscometer spindle 3 at 20 rpm under ISO 2555. Viscosity is lowered by raising the oil content or by increasing the ethyl acetate fraction. The adhesive is filtered through a 100 μm bag filter before filling.

Spray application on automotive headliner and foam-to-fabric laminates uses air-assisted spray or high-volume low-pressure equipment. Atomizing pressure is held between 0.2 MPa and 0.4 MPa. Drying tunnels have three zones at 60 °C, 70 °C, and 80 °C. Residual solvent after drying is maintained below 1,500 mg/m² by on-line flame ionization detection. Open time is controlled by adjusting solvent evaporation rate. Adhesive performance is tested by ASTM D3330/D3330M peel and by compression shear after lamination. For marine interior applications, the adhesive layer is assessed under IMO Resolution MSC.307(88) FTP Code Part 5 for surface flammability, with smoke density measured according to ISO 5659-2. Formulators must also verify that the final mixture does not contain a substance on the REACH SVHC candidate list above 0.1 wt%. Toluene-free solvent blends are preferred because toluene is classified as reproductive toxicity Category 2 under EU CLP and triggers additional exposure monitoring under Directive 98/24/EC.

Published data for this specific configuration is limited regarding long-term hydrolysis stability in marine environments. Therefore bond durability is evaluated on aluminum and melamine-faced panels after 7 days immersion in 40 °C water and after 500 h salt spray exposure under ISO 9227. End products include automotive trim laminates, bedding foam assembly adhesives, marine deck coverings, and footwear midsole bonding lines.

Oil-Extended TPE Compounds for Injection-Molded Soft-Touch Grips

Dry blending of SIS 2600 with polypropylene homopolymer and high-impact polystyrene is performed in a ribbon mixer at 40 °C for 20 min. The PP homopolymer should have a melt flow rate of 12 g/10 min to 20 g/10 min under ISO 1133-1:2022 at 230 °C/2.16 kg. A compounded formulation for a 35 Shore A grip uses SIS 2600 at 100 phr, polypropylene homopolymer at 50 phr, HIPS at 30 phr, naphthenic process oil at 100 phr, calcium carbonate at 15 phr, and antioxidant at 1.0 phr. The oil is injected at barrel segment 6 of a co-rotating twin-screw extruder with an L/D ratio of 48:1. Extruder barrel temperatures are held between 170 °C and 210 °C. Vacuum venting at -0.085 MPa removes volatiles before the underwater pelletizer. Stranding is avoided because the compound has low melt strength at discharge temperatures above 190 °C.

Injection molding of the compounded TPE is performed at melt temperatures of 180 °C to 210 °C and mold temperatures of 20 °C to 50 °C. Injection pressure is set from 60 MPa to 90 MPa, with holding pressure at 40 MPa to 60 MPa and back pressure at 2 MPa to 5 MPa. Shrinkage after 24 h is measured in the range 1.0 % to 2.0 % according to ISO 294-4. Hardness ranges from 20 Shore A to 60 Shore A depending on oil and filler loadings. Tensile strength is tested under ISO 37 with dumbbell specimens and generally falls between 4 MPa and 12 MPa. Tear strength under ISO 34-1 is 15 kN/m to 30 kN/m. The compound is overmolded onto polypropylene or polycarbonate substrates. Adhesion to PP is improved by raising the PP content in the TPE formulation above 40 phr. For polycarbonate, substrate preheating to 80 °C to 100 °C reduces surface skin delamination.

Regulatory screening for soft-touch grips uses RoHS 2011/65/EU Annex II and REACH Annex XVII restrictions. Toy applications require compliance with EN 71-3 migration limits for elements in Category III scraped-off materials. Medical device handle applications are evaluated under ISO 10993-5 for cytotoxicity and ISO 10993-10 for irritation. End products include power tool soft-grip overmolds, toothbrush haptic zones, razor handle inserts, and medical instrument grips. If high humidity storage exceeds 60 % RH, pellets are pre-dried at 70 °C for 2 h before molding to avoid surface splay.

If Thickness Uniformity Below 0.5 % Is Required in Elastic Hygiene Films

On a cast film line, the melt temperature at the die lip is held between 190 °C and 215 °C. The SIS 2600-rich compound is fed through a single-screw extruder with an L/D ratio of 30:1 and a barrier screw designed for elastomers. The die is a coat-hanger slot die with automatic lip adjustment. Thickness variation is controlled within ±0.5 % by an infrared thickness gauge and lip-bolt thermal expansion. Chill roll temperature is set at 15 °C to 25 °C. A secondary cooling roll at 10 °C reduces blocking during slitting and winding. Winding tension is kept between 0.1 N/mm and 0.3 N/mm to prevent gauge banding. Blown film extrusion is not recommended because the low melt strength of SIS 2600-rich compounds causes bubble instability below 210 °C.

A formulated elastic layer uses SIS 2600 at 60 wt% to 80 wt%, a hydrogenated SEBS at 10 wt% to 20 wt%, a hydrogenated C5 tackifier at 5 wt% to 15 wt%, white mineral oil at 5 wt% to 10 wt%, and a silica antiblock at 2 wt% to 5 wt%. The SEBS fraction is added to raise service-temperature stability and reduce room-temperature cold flow. The tackifier is limited to 15 wt% because higher loadings produce excessive unwind force and machine-direction neck-in. The film is tested for load at 100 % elongation under ISO 527-3 and for hysteresis set after two cycles to 100 % elongation under ASTM D5459. Elastic films based on SIS 2600 typically show a load at 100 % elongation of 1.0 MPa to 2.5 MPa and a hysteresis set of 10 % to 20 %. The caliper of the film ranges from 40 μm to 120 μm. Below 40 μm, pinhole counts increase unless melt filtration at 25 μm is installed.

Hygiene applications require compliance with OEKO-TEX Standard 100 product class I for infant skin contact and with the European Union General Product Safety Directive 2001/95/EC. Medical bedding films are additionally screened under ISO 10993-5 and ISO 10993-10. Unmodified SIS films block within 24 h at 25 °C when wound under tension above 0.5 N/mm. The silica antiblock increases surface roughness without affecting elastic recovery beyond 3 % of initial set. End products include elastic ear strips for baby diapers, side panels for adult incontinence briefs, and leg cuffs for pull-up training pants.

Cold-pour electrical filling compounds use a mineral-oil matrix gelled by SIS 2600 at polymer loadings of 5 wt% to 15 wt%. The gel is produced in a heated planetary mixer with vacuum deaeration. The mixer is charged with naphthenic or paraffinic process oil at 120 °C, then SIS 2600 pellets are added under low-speed agitation at 30 rpm. The batch temperature is raised to 150 °C to 170 °C and held until a clear homogeneous melt is obtained. Vacuum is applied at -0.095 MPa for 30 min to remove entrained air and moisture. A stabilizer package of 0.2 wt% to 1.0 wt% is added to prevent oxidative viscosity drift. Fumed silica at 1 wt% to 5 wt% may be dispersed after the polymer is dissolved to impart thixotropy and reduce oil separation.

Finished gel is tested for cone penetration under ISO 2137. Values in the range 150 × 0.1 mm to 400 × 0.1 mm cover soft void-fill grades to firm cable-sealing grades. Dropping point measured by an equivalent cup-and-ball method is generally 100 °C to 130 °C. Dielectric strength under IEC 60243-1 is commonly 15 kV/mm to 25 kV/mm for a 2 mm gap. Volume resistivity under IEC 62631-3-1 is maintained above 1 × 10¹² Ω·m after 7 days at 80 °C. Oil separation is evaluated by holding a 100 g sample in a lined container at 80 °C for 24 h; the separated oil fraction is kept below 2 wt%. If oil separation exceeds 5 wt%, the polymer content is increased by 2 wt% or the fumed silica level is raised by 1 wt%.

In two-part cold-pour cable joint systems, the gel is poured into the joint body and cured by cooling below the styrene-block glass transition. The system does not require chemical crosslinking. This property allows re-entry and re-pouring after cable maintenance. Compliance screening uses REACH Article 33 and RoHS 2011/65/EU. Published data for this specific configuration is limited regarding long-term adhesion to XLPE cable jackets, so laboratory tests are required on actual jacket grades. End products include telecommunication closure seals, low-voltage cable void fill, and re-enterable splice encapsulation compounds.