Bostik ROLL MT35 is a contact dry adhesive supplied as a continuous, non-blocking web in roll format. The model designation places the material in the Bostik dry adhesive portfolio rather than in the solvent-borne polychloroprene, waterborne, or pressure-sensitive adhesives used for similar lamination applications. At ambient temperature the web exhibits no tack; bond formation proceeds through inline heating and nip or platen pressure. This format eliminates liquid coating stations, forced-air drying tunnels, solvent recovery systems, and open-time management associated with liquid contact adhesives. The technical data sheet from Bostik remains the controlling reference for lot-specific basis weight, width, and activation parameters. Published data for this specific configuration is limited, so converter qualification should include substrate-specific bond testing rather than relying solely on nominal product-class values.

The sequence MT35 is commonly interpreted within Bostik dry web nomenclature as a nominal basis weight of 35 g/m²; however, this reading must be verified against the certificate of analysis because basis weight tolerance and coating uniformity can vary with slitting and embossing. Roll widths are typically slit to converter specification between 1,200 mm and 1,800 mm, with 76 mm or 152 mm core diameters. The adhesive layer is neither foamed nor fiber-reinforced unless specified. Storage is recommended below 30°C and below 60% RH to exclude moisture uptake and blocking. The web should be allowed to equilibrate to the converting room for at least 24 h before unwinding to avoid tension variation and telescoping.

What separates a dry contact web from liquid polychloroprene and pressure-sensitive adhesives?

The principal difference is the absence of a carrier solvent or continuous water phase. Solvent-borne contact adhesives require open-time allowance for solvent flash-off before mating, and they emit volatile organic compounds governed by local air quality regulations. Waterborne contact adhesives require forced-air drying and may contain coalescing solvents, surfactants, and biocides. A dry web such as Bostik ROLL MT35 contains essentially 100% nonvolatile polymeric binder by applied mass; therefore, no drying step exists. Unlike pressure-sensitive adhesives, the dry web is non-tacky at room temperature. This property allows slitting, die-cutting, and interleaving without release liners, provided the roll is not stored beyond the maximum recommended temperature. In comparison with reactive hot-melt polyurethane adhesives, the dry contact web does not require moisture-cure regulation; it can be reheated and repositioned during the activation stage up to the gel point or crystallization point.

The roll format confers a uniform adhesive thickness across the web width, which is difficult to achieve with spray-applied liquid adhesives. Weight variation across the web can influence bond thickness and T-peel distribution. On production laminators, dry web systems exhibit lower changeover time because no mixing, viscosity adjustment, or solvent ratio control is required. This does not imply universal substrate compatibility; low-surface-energy polyolefins may require corona or plasma pretreatment because the dry adhesive alone cannot overcome surface energies below 38 mN/m without an adhesion promoter. The absence of volatile solvents also reduces the risk of solvent attack on expanded polystyrene foams and sensitive barrier films.

Thermal Degradation and Processing Window Controls in Flat-Bed Lamination

Because the dry web is heated from one side, the through-thickness temperature gradient can be the main source of process variation. For a 35 g/m² web, the thermal resistance of the adhesive itself is low; the controlling resistance is the facing substrate. Above the melt onset, polymer viscosity drops and flow into the substrate asperities becomes possible. The zero-shear viscosity in the molten state is not published for this product; it should be obtained by rheometry if penetration into open-cell foam must be predicted. Flow into the substrate is influenced by dwell time, surface tension, and the pressure field in the nip. A low-pressure, long-dwell belt press produces a different bond morphology than a high-pressure, short-dwell calender. Thick laminates run at high speed may show an apparent bond after cooling that passes initial hand-peel checks but fails humidity ageing because the adhesive did not reach the full melt state at the interface.

Heated-nip rolling presses, flat-bed laminators, and belt presses are suitable classes of equipment. Heated rolls should have a surface temperature deviation not greater than ±5°C across the width; otherwise edge bond strength can diverge from center-bond strength. Nip pressure in the range of 1–4 bar is common for dry web lamination, but the optimum depends on substrate compressibility. Open-cell foam under excessive pressure loses thickness; rigid substrates under insufficient pressure retain entrapped air, producing a textured or tunnelled bond. The converting line should use closed-loop tension control because tension above 4–8 N/cm on low-grammage facings can cause edge lift and telescoping of the finished roll.

When roll-to-roll laminators run below the activation temperature

Initial heat transfer in dry web bonding is governed by the nip surface temperature, line speed, and contact pressure. If the exposed surface remains below the melt onset by more than 5°C to 10°C, only partial melting occurs. The web may show visual clarity but remain weakly fused to the substrate; subsequent T-peel values can drop below 50% of the plateau established for fully molten lamination. This is a critical processing threshold, not a linear softening response. On flat-bed presses, dwell time must allow heat to penetrate through the facing layer to the adhesive interface. For low-thermal-conductivity facings such as polyurethane foam or closed-cell polyolefin foam, the required dwell time can be several seconds longer than for aluminum foil. The MT35-specific melting range and open activation window should be read from the lot-specific differential scanning calorimetry trace. Published data for this specific configuration is limited; running a thermal profile across the web width with contact thermocouples is recommended before setting production parameters.

Bond strength in dry web laminates fails in three primary modes: adhesive-substrate interfacial separation, cohesive failure within the adhesive layer, and substrate tearing. Interfacial separation indicates incomplete wetting or surface energy mismatch, while cohesive failure indicates the polymer film itself was weaker than the interface and may be caused by underheating, plastication, or ageing. Substrate tearing is the target failure mode for many product designs but is not sufficient evidence of long-term durability. Tensile lap-shear tests under ISO 4587:2003 can distinguish these modes if the fractured surface is examined microscopically. A high proportion of interfacial failure on cleaned, primed substrates suggests the activation temperature was too low, the dwell time was too short, or the pressure was insufficient to break through the boundary layer.

Bond Strength, Thermal Resistance, and Environmental Exposure Benchmarks

Qualification of dry contact adhesive bonds should follow test methods that separate adhesion, cohesion, and substrate failure modes. Flexible-to-flexible T-peel testing under ISO 11339:2022 is preferred for laminates in which both adherends deform; flexible-to-rigid peel resistance is covered by ASTM D903 and ASTM D1876. Structural shear is measured by ISO 4587:2003 or ASTM D1002. The adhesive melting range is determined by ISO 11357-3; melt mass-flow rate, where relevant for penetration into porous substrates, is determined under ISO 1133-1:2022. Table 1 lists applicable methods and specimen roles. When reporting values, the failure mode must be recorded because a high T-peel value with substrate delamination does not indicate adhesive shear strength. Durability testing for automotive laminates may include heat ageing at 90°C for 168 h and humidity ageing at 85°C/85% RH for 168 h, but acceptance limits are set by the end-use specification and are not supplied by the adhesive datasheet.

Plasticized PVC and certain nitrile rubber foams can function as a slow diffusing source of plasticizer and antiozonant. In bonded assemblies, these migrating species may reduce bond strength after thermal ageing. A barrier film or a tie-coat should be considered when the laminate is subjected to continuous service above 60°C. Low surface energy substrates below 38 mN/m require corona, plasma, or chemical priming before activation; untreated polypropylene and polyethylene are not expected to form durable structural bonds with a dry contact adhesive alone. Condensation on chilled substrates should be avoided because the presence of a monolayer of moisture can inhibit wetting and produce microvoids at the interface. If the substrate is stored below the dewpoint, the converting room should include an induction or infrared pre-drying station before lamination.

Does the dry web format alter regulatory compliance and industrial hygiene duties?

A dry contact adhesive with substantially 100% solids content influences workplace exposure control differently from solvent-based adhesives. The absence of organic solvents reduces the release of volatile organic compounds during storage and lamination; however, thermal activation can generate low-level process emissions if the polymer is overheated. Local exhaust ventilation and thermal oxidizer design are governed by the resin decomposition products and by the specific plant permit, not by the absence of a solvent carrier. Compliance with REACH registration and SVHC communication duties remains mandatory for industrial use in the European Union. Where the product is used in food-contact laminates, converters must request Bostik documentation for the specific structure and migration testing under the applicable EU or FDA framework; classification under a general polymer regulation cannot be inferred from the product being solvent-free. End-use specifications for automotive interior laminates may additionally require odour and fogging tests under ISO 6452 or VDA 278; the adhesive supplier should provide raw-material declarations but not the finished laminate certificate.

Within the broader Bostik portfolio, dry web products differ from solvent-borne contact adhesives by format rather than by chemistry. A solvent-borne neoprene contact adhesive can be applied by brush, roll, or spray and offers instant tack after solvent flash-off; however, it introduces open-time interdependence, viscosity drift, and solvent exposure. A dry web eliminates flash-off but requires lamination equipment with heat. Compared to Bostik waterborne polychloroprene adhesives, the dry web does not need drying ovens or emulsion stability control. Compared to moisture-curing polyurethane hot melts, the dry web does not rely on ambient humidity to achieve strength; after cooling below the crystalline or glass transition, it can develop immediate handling strength. These differences determine capital equipment choice, energy consumption, and occupational exposure profiles rather than merely adhesive cost per kilogram.

Incoming quality control should include roll width, unwind tension, basis weight, and spot checks of web continuity. Even minor basis weight variations of ±3 g/m² across the web can cause visible bondline thickness variation and altered stiffness in flexible laminates. The certificate of analysis may report only average values; converters running optical film or leather laminates should request roll mapping of basis weight and thickness. Storage stability of dry webs is finite because aging can change crystallinity and tack; lots stored beyond the supplier specified shelf life should be revalidated with T-peel and DSC before use.

Before activation, the dry web can be trimmed and repositioned; once the polymer has cooled below its recrystallization temperature, the bond becomes fixed. This behavior differs from pressure-sensitive adhesives, which build immediate tack at room temperature, and from moisture-cure hot melts, which continue to crosslink over hours. Rework of a cooled dry web laminate usually requires reheating above the softening point and peeling while hot. If the laminate contains heat-sensitive textiles, localized infrared heating may be preferable to full-oven reheating. The presence of an adhesive web across the entire surface distinguishes the product from hot-melt dot patterns and printed adhesive coatings; the continuous layer provides high surface contact but may increase stiffness and gas barrier properties of thin laminates.