Dairen DA-105 vinyl acetate-ethylene (VAE) emulsion is supplied as a high-solids, carboxylated copolymer dispersion stabilized with a polyvinyl alcohol (PVOH) protective colloid. The product exhibits a non-volatile content of 55 ± 1 % (ISO 3251:2019, 105 °C, 2 h) and a Brookfield viscosity spanning 2 500 – 3 800 mPa·s at 23 °C (spindle 4, 20 rpm, ISO 2555:2018). Minimum film formation temperature (MFFT) measured per ISO 2115:2000 is ≤ 0 °C, which eliminates the need for external coalescing solvents in many adhesive and coating formulations operating above this thermal threshold.
Production-scale bulk handling records from twin-screw extruder compounding lines and continuous adhesive laminators indicate that prolonged exposure to shear rates exceeding 10⁴ s⁻¹ can induce reversible viscosity drift in PVOH-stabilized emulsions; in-line rotor–stator mixers equipped with cooling jackets maintaining jacket outlet temperatures below 35 °C have been shown to suppress this effect. The grade is classified as non-hazardous under REACH Regulation (EC) No 1907/2006 and complies with FDA 21 CFR 175.105 for indirect food contact adhesives when formulated appropriately.
What Distinguishes DA-105 from Standard Vinyl Acetate Homopolymer Emulsions?
The incorporation of ethylene as a comonomer within the VAE backbone lowers the glass transition temperature (Tg) of the base polymer to approximately −5 °C (differential scanning calorimetry, 10 K/min, second heating cycle). This internal plasticization relieves the dependence on migratory plasticizers such as dibutyl phthalate (DBP) or benzoate esters. In accelerated aging tests mimicking 10-year shelf storage (40 °C, 75 % RH), PVAc homopolymer films formulated with 12 phr DBP exhibited a 45 % loss in tensile elongation at break (ASTM D638-14, Type V specimen) due to plasticizer volatilization, whereas DA-105-based films retained 90 % of initial elongation. This difference becomes critical in laminated paper and board structures where embrittlement leads to peel failure at the substrate interface under cyclic humidity loading as described in ASTM F904-16.
Additionally, the PVOH protective colloid imparts dry tack and repulpability, features not present in surfactant-stabilized acrylic dispersions. Repulping trials conducted on a laboratory Valley beater (TAPPI T 205 sp-18) with corrugated medium bonded using DA-105 adhesive achieved fiber recovery exceeding 98 % without visible “stickies” deposition on the screen, a common contaminant when high-Tg, non-dispersible binders are used in recycling streams.
Specification Envelope and Benchmarking Matrix
The following table consolidates primary specification parameters and contrasts them with Dairen DA-101, a homopolymer PVAc dispersion of similar solids content, to highlight the functional divergence attributable to ethylene modification.
| Parameter | DA-105 (VAE) | DA-101 (PVAc) | Test Method |
|---|---|---|---|
| Solids content, % | 54 – 56 | 54 – 56 | ISO 3251:2019 |
| Brookfield viscosity, mPa·s | 2 500 – 3 800 | 3 000 – 5 000 | ISO 2555:2018 |
| pH | 4.0 – 5.0 | 3.5 – 4.5 | ISO 976:2021 |
| MFFT, °C | ≤ 0 | ≥ 15 | ISO 2115:2000 |
| Tg (DSC midpoint), °C | −5 ± 2 | +32 ± 2 | ISO 11357-2:2020 |
| Tensile strength (film, 23 °C), MPa | 5 – 8 | 25 – 35 | ASTM D638-14 |
| Elongation at break (film, 23 °C), % | 600 – 900 | 5 – 10 | ASTM D638-14 |
| Water absorption (24 h immersion), % | 10 – 15 | 40 – 60 | ISO 62:2008 |
The data illustrate that although DA-105 exhibits inherently lower tensile strength as a neat film, its elongation capacity is two orders of magnitude greater, and water resistance is substantially enhanced—a direct consequence of the hydrophobic ethylene segments reducing equilibrium moisture uptake. For load-bearing structural adhesives, strength is typically recovered through post-addition of crosslinkers (e.g., glyoxal, ammonium zirconium carbonate) or via blending with higher-modulus dispersions.
Emulsion stabilization via PVOH rather than surfactant imparts pseudoplastic flow behavior. On a controlled-stress rheometer (cone-plate geometry, 40 mm, 1°), DA-105 exhibits a shear viscosity of 0.8 – 1.2 Pa·s at 1 000 s⁻¹ compared to a low-shear viscosity often exceeding 10 Pa·s. This shear-thinning profile is advantageous for roller-coater applications where low drag at application shear is required, followed by rapid viscosity rebuild to prevent strike-through into porous substrates.
Operators running high-speed Kraft paper sack laminators (operating at 120 – 180 m/min) have documented that substitution of homopolymer PVAc with DA-105 reduces web tension-induced edge curl due to the lower elastic modulus of the dried film. However, blocking resistance at temperatures above 50 °C is inferior to that of homopolymer films; therefore, when palletized bonded stacks are warehouse-stored in summer conditions (internal stack temperatures recorded up to 55 °C), incorporation of 2 – 3 wt% of a high-Tg styrene-acrylic dispersion is advised to raise the blocking onset temperature to approximately 70 °C without sacrificing MFFT.
Application Protocol: Two-Part Crosslinked Assembly Adhesive for D3/D4 Wood Bonding
Compliance with EN 204/205 durability classes D3 (interior, frequent short-term water exposure) and D4 (exterior, frequent long-term water exposure) is attainable using DA-105 as the base emulsion within a two-part system. The following formulation has been validated on a hollow-core door assembly line using a polyvinyl acetate dispensing head (Nordson FP-200, 0.8 mm orifice) and a separate isocyanate hardener stream delivered via a static mixer manifold.
Part A is prepared by blending 100 pbw DA-105, 5 pbw triacetin (plasticizer/coalescent modifier to depress MFFT to −5 °C for cold-chamber assembly at 8–10 °C), 0.5 pbw defoamer (polysiloxane-based, 10 % active), and 3 pbw calcium carbonate filler (d50 2 μm). Part B is a polymeric MDI (pMDI) hardener with NCO content 31.5 %. The two parts are combined at a volumetric ratio of 100:15 and applied at 120 – 150 g/m² single-sided spread. Pot life of the mixed adhesive at 20 °C is 45 – 60 minutes, determined by the time required to double initial Brookfield viscosity. Open time measured on beech substrates at 23 °C / 50 % RH is 8 – 12 minutes (EN 204 method).
Cure progresses through two distinct stages: physical setting via water loss and PVOH film formation, followed by chemical crosslinking through reaction of isocyanate groups with hydroxyl functionalities on the PVOH and with residual water. Tensile shear strength on beech after 7 days conditioning at standard atmosphere (23 °C, 50 % RH) and subsequent 4 h boiling water immersion (D4 test sequence) remains above 4.0 MPa, surpassing the EN 204 D4 minimum requirement of 4.0 MPa. Without the isocyanate crosslinker, the same adhesive formulation fails the boiling-water soak with wood failure percentages dropping below 30 %.
A critical processing note: the emulsion must not be formulated with ammonia as a pH adjuster when using pMDI hardeners; residual ammonia reacts preferentially with isocyanate, generating ureas that do not contribute to wood-polymer interphase bonding. Instead, sodium bicarbonate (0.1 – 0.2 wt%) is used to buffer pH to 4.5 – 5.0 without interfering with isocyanate kinetics.
Published data for this specific configuration regarding long-term fatigue under cyclic humidity loading (EN 302-1) is limited; however, 12-month natural weathering trials in a temperate climate (Taiwan, Taichung) on maple test specimens indicated shear strength retention of 78 % relative to initial values, with primary failure occurring at the wood substrate rather than the bondline.
Pre-drying of substrates to moisture content 8 – 12 % is required when ambient relative humidity exceeds 60 %. Bonding of tropical hardwoods with high extractive content (teak, iroko) may necessitate solvent-wiping immediately prior to adhesive application to remove oily exudates that inhibit hydrogen bonding between the PVOH colloid and cellulose microfibrils.
Why Ethylene Content Matters More Than Solids in Laminating Adhesives
In flexible packaging lamination, the modulus mismatch between the aluminum foil or BOPP film and the laminating adhesive governs flex-crack resistance. A VAE with 12 – 15 wt% ethylene content, typified by DA-105, yields a dried film with storage modulus (E') of approximately 20 – 40 MPa at 23 °C (DMA, 1 Hz), whereas a 55 % solids PVAc homopolymer routinely exhibits E' values above 1 000 MPa in the glassy state. Under Gelbo flex testing (ASTM F392/F392M-21), laminated structures utilizing DA-105 consistently surpass 1 500 cycles before pinhole formation, compared to 200 – 300 cycles for a homopolymer PVAc laminating adhesive of equivalent coat weight (3 – 4 g/m² dry). This performance differential is not due to solids percentage discrepancies but rather the intrinsic flexibility conferred by the ethylene linkages, which reduce the beta-relaxation temperature of the polymer.
Machinery configuration must account for the lower heat activation temperature of DA-105. On a solventless lamination line, nip temperatures above 60 °C combined with residence times exceeding 3 seconds can induce premature film formation on the gravure cylinder, leading to streaks. Maintaining nip temperature at 45 – 50 °C with an engraved cylinder cell volume of 9 – 12 cm³/m² (quadrangular pattern, 60 l/cm) has proven effective in continuous production runs exceeding 24 hours without cleaning.
In comparison to Dairen DA-102, a surfactant-stabilized VAE of similar solids, DA-105 demonstrates superior repulpability and lower foam generation during high-speed recirculation in tray-fed laminators. However, DA-102 offers better freeze-thaw stability (passes 3 cycles of −10 °C / room temperature cycling without grit formation), attributable to the surfactant steric barrier, whereas PVOH-stabilized DA-105 may coagulate upon one freeze cycle. Therefore, for unheated warehouses in sub-zero climates, insulated transport and storage above 5 °C must be specified.
The absence of alkylphenol ethoxylate (APEO) surfactants is confirmed by third-party testing to detection limits of 10 ppm per EPA 8321B. This, combined with ultra-low residual vinyl acetate monomer content (＜ 500 ppm, gas chromatography headspace per ISO 6401:2022), addresses regulatory restrictions in the EU Ecolabel for adhesives (Commission Decision 2014/312/EU) and various Asian Green Label schemes.
Producers of wet laminations for paper-aluminum composite beverage cartons often incorporate 0.5 – 1.0 phr ammonium zirconium carbonate (AZC) as a latent crosslinker. The AZC reacts with carboxyl groups on the VAE backbone upon drying and pH drop, conferring enhanced hot water resistance. In pilot trials on a Tetra Pak-type structure (PE/paperboard/PE/Al/adhesive/PE), peel strength after 30 min in 80 °C water increased from 0.2 N/15 mm (un-crosslinked DA-105) to 1.8 N/15 mm with 0.8 phr AZC, tested per ASTM F904-16. However, pot life of the adhesive shortens to 4 – 6 hours due to progressive ionic crosslinking, demanding batch mixing rather than continuous replenishment in the coater tank.
Wash-off of dried adhesive from stainless steel equipment surfaces is more effectively performed with warm water ( 40 – 50 °C) containing 1 – 2 % sodium hydroxide by weight; this swells the PVOH colloid and disrupts adhesion. Solvent-based cleaning with ethyl acetate is not recommended as it does not dissolve the PVOH and may leave a gummy deposit.
Relative Performance in Architectural Coatings: Contrast with Styrene-Acrylics
Where DA-105 is evaluated as a sole binder in interior flat wall paints (PVC 65 – 75 %), scrub resistance per ASTM D2486-17 Method B is typically below 50 cycles, well inferior to styrene-acrylic copolymer binders that exceed 200 cycles. The limit arises from the thermoplastic nature and moisture sensitivity of PVOH. For such decorative applications, DA-105 functions not as a replacement for styrene-acrylics but as a low-cost, APEO-free co-binder for repulpable ceiling tiles and temporary peelable coatings where permanent washability is not mandated. When co-formulated with 20 – 30 wt% (based on total binder) of a hard acrylic, the scrub resistance can be elevated to 120 cycles while retaining the bio-based carbon contribution from the VAE’s ethylene-derived segment, measurable via ASTM D6866-22.
In carpet pre-coat and secondary backing applications, DA-105 offers sufficient hot tack to secure tufts during oven curing ( 130 – 150 °C, 2 – 4 minutes) without requiring fugitive acid catalysts. Peel strength values on latex-backed carpet systems range from 1.5 – 2.5 N/5 cm (ISO 11896:2000), which, while modest, satisfy commercialization requirements for residential broadloom with 10-year warranty expectations when dried film weight is maintained above 60 g/m².
The emulsion is incompatible with high-acid-number alkyd emulsions; mixing results in instantaneous coagulation due to protonation of the PVOH colloid. Trials utilizing Dairen DA-105 as a pigment-grinding vehicle for organic red and yellow pigments (toluidine, Hansa) demonstrated excellent color development equivalence to a standard PVAc vehicle, with Delta E values below 0.5 (CIELAB, D65 illuminant) when dispersed under high shear via a Dispermat CV (tooth impellor, tip speed 12 m/s, 20 minutes grind).
The final processing scenario concerns compression-set resistance of DA-105 films under localized pressure. When used as a binder in nonwoven interlinings for apparel, the polymer maintains a compression set (ASTM D395-18, Method B, 22 h at 70 °C) of approximately 85 %, an acceptable value for low-resilience fusible interlinings but unsuitable for resilient foam replacement. Substitution with a VAE of higher ethylene content (25 – 30 wt%) is required to lower compression set below 60 %. This limitation sets the operational boundary for DA-105 in cushioning applications.
