Section
| HS Code | 134135 |
| Product Name | Rubber Adhesive RA |
| Product Type | Rubber-based contact adhesive |
| Base Polymer | Polychloroprene rubber |
| Appearance | Black viscous liquid |
| Solvent Carrier | Toluene and hexane blend |
| Solids Content | 25-35% |
| Viscosity | 800-1500 mPa·s |
| Density | 0.85-0.95 g/cm³ |
| Flash Point | -4°C to 0°C |
| Open Time | 5-15 minutes |
| Cure Mechanism | Solvent evaporation |
| Service Temperature Range | -40°C to 100°C |
| Application Method | Brush, roller, or spray |
| Shelf Life | 12 months |
| Packaging | 1 L cans; 5 L pails |
As an accredited Rubber Adhesive RA factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Rubber Adhesive RA is packaged in 5 L steel pails with tamper-evident lids, batch labels, and chemical hazard markings. |
| Container Loading (20′ FCL) | Rubber Adhesive RA is palletized and loaded into a 20-foot FCL container, secured, labeled, and protected from moisture and heat during shipment. |
| Shipping | Ship **Rubber Adhesive RA** in approved, sealed, labeled containers with the SDS available. Classify and package per applicable DOT/IMDG/IATA regulations; solvent-based adhesives may require flammable-liquid shipping (e.g., UN 1133). Keep cool, ventilated, away from ignition, and protect from leaks, heat, and freezing. |
| Storage | Store Rubber Adhesive RA in a cool, dry, well-ventilated area away from heat, sparks, flames, and direct sunlight. Keep containers tightly closed and upright, grounded/bonded during transfer, and separate from oxidizers, acids, and incompatible materials. Use secondary containment, prevent spills, and follow SDS and local fire-code requirements. Keep out of reach of unauthorized personnel. |
| Shelf Life | Store Rubber Adhesive RA sealed in a cool, dry, well-ventilated area; shelf life is typically 12 months from date of manufacture. |
In radial tire steel cord skim compounds, Rubber Adhesive RA is used as the resorcinol-type methylene acceptor in a donor-acceptor network with hexamethoxymethylmelamine. The compound is mixed in two passes on an intermeshing internal mixer with ram pressure 0.55 MPa and rotor speed 40 rpm. First-pass dump temperature is held at 155 °C to 160 °C. Rubber Adhesive RA is not added in the first pass. It is added in the second pass at 95 °C to 105 °C, together with insoluble sulfur and DCBS. This temperature limit prevents premature condensation of resorcinol nuclei with the methylene donor. A typical truck and bus radial skim formulation contains 80 phr natural rubber, 20 phr butadiene rubber, 50 phr carbon black N326, 15 phr silica, 1.5 phr TESPT silane, 2.5 phr Rubber Adhesive RA, 2.0 phr hexamethoxymethylmelamine, 1.0 phr cobalt neodecanoate, 4.5 phr insoluble sulfur, and 0.8 phr DCBS. The cobalt carboxylate influences brass-oxide stabilisation at the wire interface. The brass plating on the steel cord is maintained at approximately 63.5 % copper and 36.5 % zinc. The RA:HMMM ratio is kept between 1:1 and 1:1.5 in this construction.
| Parameter | Method | Set point |
|---|---|---|
| Mooney viscosity | ASTM D1646 | 55–70 MU at 100 °C |
| Mooney scorch t5 | ASTM D1646 | 18–24 min at 127 °C |
| Rheometer t90 | ASTM D5289 | 12–18 min at 160 °C |
| H-test adhesion | ASTM D4776 | 10 mm embedment, 100 mm/min |
| Humid ageing | 90 °C/85 % RH/14 days | ≥70 % retention |
Rheological control is measured by ASTM D1646. Mooney viscosity ML(1+4) at 100 °C is held at 55 MU to 70 MU. Mooney scorch t5 at 127 °C is specified at 18 min to 24 min. The cure reaction is followed by ASTM D5289. t90 at 160 °C is 12 min to 18 min. The skim is calendered to wire coat dimensions between 0.55 mm and 0.75 mm. Calender roll temperature is set at 85 °C to 95 °C. Insufficient Rubber Adhesive RA produces low unaged wire adhesion. Excess Rubber Adhesive RA produces high modulus and low fatigue crack growth resistance. The boundary is sharp. An increase from 3.5 phr to 4.5 phr causes a measurable drop in extensibility and a rise in Shore A hardness of 4 to 6 points under ASTM D2240.
Adhesion testing follows ASTM D4776. Wire cord is embedded 10 mm into the cured skim. Crosshead speed is 100 mm/min. Rubber coverage is classified under ISO 5603. Humid ageing is carried out at 90 °C and 85 % relative humidity for 14 days. Retention below 70 % of the unaged average indicates an imbalance in the donor-acceptor system or excessive brass dezincification. The steel cord skim compound is used in the belt and carcass regions of truck and bus radial tires. The terminal product is the rubber-coated steel cord layer in the pneumatic tire crown.
The carcass adhesion compound for hard rock mining conveyor belts is formulated around a 60:40 natural rubber/SBR blend with fire-resistant filler loadings. Rubber Adhesive RA is included at 2.0 phr with hexamethoxymethylmelamine at 1.5 phr. The filler system contains 35 phr carbon black N330, 30 phr aluminium hydroxide, 5 phr zinc borate, and 4 phr silica. The first mixing stage is discharged at 150 °C. Rubber Adhesive RA and the cure system are added in the second stage at 95 °C. Published data for this fire-resistant configuration is limited because supplier-specific flame-retardant packages change interface pH by up to 0.5 pH units.
Ply separation in fire-resistant conveyor belt compounds is driven by cyclic tension at the drum and trough transition. The tie gum is calendered onto RFL-dipped EP fabric at 0.40 mm to 0.50 mm thickness. Three-roll calender roll temperature is 85 °C. Multi-daylight press cure is performed at 160 °C for 10 min to 12 min. Adhesion is tested under ISO 252:2014 and DIN 22102-1. The static adhesion is supplemented by ASTM D413 peel after hot air ageing under ASTM D573 at 70 °C for 168 h. Rubber Adhesive RA improves the retention of bond strength after the flame-retardant package has migrated to the interface. Without the resin, adhesion loss can exceed 30 % after the same ageing interval in compounds containing antimony oxide and aluminium hydroxide. The terminal products are underground mine conveyor belts and overland coal belts with safety class flame resistance.
Hydraulic hose reinforcement compounds are built around NBR with an acrylonitrile content of 33 % to 35 %. The adhesion layer between the extruded inner tube and the steel wire braid contains Rubber Adhesive RA at 1.0 phr to 1.5 phr and hexamethoxymethylmelamine at 0.8 phr to 1.2 phr. The lower range is necessary because NBR compounds are extruded through a cold-feed pin-barrel extruder with L/D 16:1 and the adhesion layer is only 0.3 mm to 0.5 mm thick. Extrudate surface temperature must remain below 105 °C. At 110 °C the thin adhesion layer begins to show micro-crumb due to premature Rubber Adhesive RA condensation. This is a narrow processing window of ±5 °C. Hexamethoxymethylmelamine is preferred over hexamethylenetetramine in wire-reinforced hose stock because it does not release ammonia into the braid void.
The braided hose is cured in a salt bath at 190 °C for a shaft speed calibrated to cure the cover without overcuring the thin adhesion layer. Adhesion between the inner tube and braid is tested under ISO 8033. The hose construction is validated under ISO 18752 for pressure impulse. The terminal product is a steel wire braided hydraulic hose for 35 MPa to 42 MPa working pressure. Rubber Adhesive RA also improves oil-exposure bond retention after immersion in IRM 903 oil at 100 °C for 168 h under ASTM D471. This is a critical requirement for phosphate ester and mineral oil hydraulic lines.
Shot-blasted steel inserts for heavy-duty suspension bushings are coated with a two-coat primer-cover system before the mould closes. The elastomer is injection moulded from a natural rubber/SBR blend containing 45 phr N550, 2.0 phr Rubber Adhesive RA, and 1.5 phr hexamethoxymethylmelamine. The injection unit runs at barrel temperature 75 °C to 85 °C, mould temperature 165 °C, and cure time 5 min. The phosphated insert substrate improves wet-bond stability.
Rubber Adhesive RA is not the primary metal-to-rubber bonding agent. It functions as a compound-side migration barrier. The vulcanisate resists salt-water undercutting of the bond line. Bond specimens are tested under ASTM D429 Method B. The 90° peel is measured after vulcanisation and after 96 h neutral salt spray under ASTM B117. A retention above 80 % is required for suspension bushings. The method is paired with ISO 813 for metal units. Failure under ASTM D429 Method B should be cohesive tearing within the rubber body. Adhesive-side failure signals primer contamination or excess Rubber Adhesive RA bloom. Excess Rubber Adhesive RA above 2.5 phr blooms to the moulded surface and defects the paint or primer coverage. The upper limit is therefore strict in smooth-surface bushings. The terminal products are bonded engine mounts, damper bushings, and stabiliser bar links for passenger cars and commercial vehicles.
Aramid cord is pre-dipped with a waterborne epoxy layer before the resorcinol-formaldehyde-latex bath. Rubber Adhesive RA is used as the RF carrier resin in the second bath. The resin is pre-condensed to a resorcinol-to-formaldehyde molar ratio between 1:1.5 and 1:2.5. The bath solids contain 8 to 12 parts of Rubber Adhesive RA per 100 parts of vinylpyridine latex. Sodium hydroxide adjusts pH to 9.2 to 10.0. The total solids target is 18 %. Free resorcinol content in the resin is maintained below 5 % to reduce fuming and skin sensitisation risk in the dipping area.
The dip line is run at 15 % to 18 % pick-up. Drying is set at 140 °C. Curing is set at 220 °C for 60 s to 90 s. A pH drift greater than 0.2 pH units causes resin precipitation in the dip pan. The circulation system is sized with a plate heat exchanger to keep the bath at 5 °C during line stops. Cord adhesion is tested with ASTM D4776 H-pull. Cord tensile retention is determined under ASTM D885. The terminal products are aramid-reinforced radial tire carcass caps and aramid power transmission belts. Published data for this specific aramid configuration is limited because dip formulations are controlled by line-specific resin age and latex compatibility.
Beneath the tooth jacket of wrapped V-belts, Rubber Adhesive RA is mixed into a friction compound that bonds the dipped polyester jacket to the vulcanised belt body. The compound is based on a 70:30 natural rubber/chloroprene blend with 40 phr N550, 6 phr silica, 2.2 phr Rubber Adhesive RA, and 1.4 phr hexamethoxymethylmelamine. The chloroprene phase requires zinc oxide as acid acceptor. The zinc chloride formed during cure influences the resorcinol-formaldehyde condensation at the fabric interface.
The calendered skim is applied to the polyester jacket at 85 °C. The assembled belt is cured in a wrapped autoclave at 150 °C and 0.5 MPa for 45 min. The adhesion at the flex zone is measured by ISO 36 tensile-adhesion testing and ASTM D413 peel. Rubber Adhesive RA limits the loss of textile-to-rubber adhesion under cyclic shear. The resorcinol-formaldehyde interphase forms with the RFL dip layer on the jacket fabric. At RA additions above 2.5 phr, the chloroprene phase shows increased modulus and reduced flex tolerance. The terminal products are wrapped classical V-belts and hexagonal double belts for industrial drives.
Calendered tie gum stock for steel mill roll covers is used between a blasted steel core and a soft NR/IR cover compound. Rubber Adhesive RA is added at 2.5 phr to 3.0 phr with hexamethoxymethylmelamine at 2.0 phr to 2.5 phr. The tie gum is formulated to 45 Shore A to 55 Shore A. The steel core is grit-blasted to Sa 2.5 under ISO 8501-1. The primer is applied after dust extraction.
The tie gum is calendered at 3 mm to 5 mm. The roll cover is wrapped in nylon tape and cured in an autoclave at 135 °C for 4 h. Bond strength is checked under ASTM D429 Method B and ISO 813. Rubber Adhesive RA in the tie gum improves adhesion retention when the roll cover is exposed to 80 °C demineralised water and dissolved process chemicals under ISO 1817 immersion. The upper addition limit is set by the need to avoid hardness drift in the soft tie gum. The terminal products are rubber-covered steel mill rollers, pump impeller linings, and large storage tank bonded linings.
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A solvent-borne polychloroprene contact adhesive designated Rubber Adhesive RA is supplied in three production grades—RA-30, RA-30HV, and RA-30TS—for bonding vulcanized natural rubber, SBR, chloroprene rubber, polyurethane foam, and fabric-backed rubber sheeting. Manufacturer-published data list RA-30 as a 22 ± 1% solids formulation with a Brookfield viscosity of 2500 ± 500 mPa·s at 25°C when tested in accordance with ISO 2555:2018. RA-30HV and RA-30TS contain the same resin base but are thickened for vertical laydown; RA-30TS exhibits a thixotropic index of 2.8 determined from apparent viscosity at 2 rpm and 20 rpm on a Brookfield RVT spindle. The product is not a structural adhesive and is not formulated for continuous immersion in aggressive solvents or for service above 100°C.
Initial tack is governed by the chloroprene-to-masticated natural rubber ratio, the softening point of the alkyl phenolic tackifier, and the evaporation profile of the solvent blend. For RA-30, the manufacturer reports an open time of 15–25 minutes at 23°C and 50% relative humidity at a wet film thickness of 80 µm. Crystallization of the chloroprene phase after solvent loss develops green strength; RA-30HV uses a higher molecular weight chloroprene fraction to reach a viscosity of 4500 ± 800 mPa·s and reduce sag on vertical EPDM profiles. RA-30TS is modified with fumed silica and maintains a 125 µm wet film on a 90° inclined surface for 10 minutes without sag.
After 24 hours at 23°C, lap shear on solvent-wiped SBR substrates is reported as 1.8 MPa under ISO 4587:2003, and T-peel on untreated SBR is 3.2 N/mm under ASTM D1876-08. The cured film retains a low modulus, which reduces stress concentration at the bond line when the assembly is flexed. Shear performance is sensitive to residual solvent; forced-air drying to a residual solvent content below 50 mg/kg is required before heat activation.
On production lines, RA-30 is sprayed with HVLP equipment fitted with a 1.4 mm nozzle and 0.25 MPa atomizing air. When spray viscosity exceeds 3000 mPa·s, the material is diluted with RA-40 thinner at 5–10 wt%. Roller coater application uses a 60 Shore A engraved roller at 50–80 µm wet film and 6–12 m/min line speed. The coated substrate passes through a drying tunnel at 55–65°C for 120–180 s, leaving an open-time window of 2–4 minutes before assembly. Contact bonding is then carried out in a hydraulic nip press at 0.2–0.5 MPa surface pressure for 15–30 s. At RH above 60%, the substrate is pre-dried; otherwise, evaporative cooling at the bond line can produce blushing and reduced peel strength on impermeable rubber grades.
Closed containers stored at 20 ± 2°C exhibit viscosity drift of less than 15% over 12 months when measured by ISO 2555:2018. Partially used drums exposed to workshop air form a surface skin within 24 hours; the skin is removed before sampling because dispersed gel particles can plug a 200 µm spray filter. Solvent separation in RA-30 is reversible by gentle mechanical mixing. High-shear mixing is not recommended because entrained air raises apparent viscosity to 3600 mPa·s and reduces diaphragm pump metering accuracy. Batch-to-batch viscosity variation on production lots is reported as ± 500 mPa·s; automated spray cells are therefore fitted with a low-pressure diaphragm pump and a 45 µm in-line filter.
RA is selected over one-part moisture-cure polyurethane adhesives for humid lamination of EPDM and SBR because RA contains no free isocyanate groups and does not generate carbon dioxide during warm curing. In a forced-air tunnel at 70°C and 35% exhaust humidity, RA-30 reaches residual solvent below 50 mg/kg after 180 s, reducing bubble formation during heated lamination at 90°C. The operational boundary is defined by solvent resistance and thermal exposure: continuous immersion in ASTM D471 reference fuels or aromatic solvents causes the chloroprene phase to swell and reduces peel strength to less than 30% of the dry value. The adhesive is therefore limited to intermittent splash contact with mineral oil and dry-heat exposure below 100°C. Amine-based accelerators are incompatible with RA and can cause premature gelation of the adhesive bath.
RA is differentiated from cyanoacrylate systems by open time, gap-filling capability, and peel behavior on flexible elastomers. Cyanoacrylate reaches fixture strength in 10–15 seconds but produces a brittle bond on rubber; RA requires 10–15 minutes for green strength at 23°C but can accommodate bond-line gaps of 0.3 mm without starvation. In comparison with two-part epoxy adhesives, RA develops lower lap shear on metals—epoxies commonly reach 15–20 MPa on grit-blasted steel under ISO 4587:2003, whereas RA is intended for elastomer substrates—but RA does not rupture a flexing rubber sole or fabric-backed gasket. RA also differs from heat-cure rubber-to-metal bonding systems because it cures by solvent loss rather than a 150–170°C vulcanization cycle.
| Property | Rubber Adhesive RA-30 | Cyanoacrylate | Two-part epoxy | Moisture-cure polyurethane | Method |
|---|---|---|---|---|---|
| T-peel on untreated SBR | 3.2 N/mm | <0.5 N/mm | <0.5 N/mm | 2.0–2.8 N/mm | ASTM D1876-08 |
| Lap shear on solvent-wiped SBR | 1.6–2.0 MPa | 0.4–0.8 MPa | 2.5–4.0 MPa | 1.8–2.5 MPa | ISO 4587:2003 |
| Open time at 23°C | 15–25 min | <1 min | 30–60 min | 10–20 min | Internal method |
| Heat resistance | 100°C | 80°C | 150°C | 120°C | ASTM E1640-18 |
| Gap filling | 0.3 mm | 0.1 mm | 1.0 mm | 0.5 mm | Internal fixture |
Regulatory control is exercised under REACH (EC) 1907/2006 Annex XVII; RA-30 contains toluene and methyl ethyl ketone and therefore requires local exhaust ventilation and explosive-atmosphere zoning in accordance with ATEX 2014/34/EU where solvent vapour concentrations exceed 10% of the lower explosive limit. RoHS directive 2011/65/EU restrictions on lead, mercury, cadmium, and hexavalent chromium are met by the RA series under supplier declaration. The adhesive is not intended for direct food contact or for medical device bonding under ISO 10993-1:2018.
