WENEW Braskem America DVR 002A Copolímero EVA, 50% Conteúdo Reciclado, Espuma e Grado de Calçados

For foam and footwear processors seeking a 50% recycled-content ethylene-vinyl acetate copolymer, WENEW Braskem America DVR 002A is supplied as a pelletized EVA grade positioned for injection-molded, compression-molded, and extruded foam components. The designation carries a nominal recycled fraction of 50% by mass; the recycled feedstock may include post-industrial or post-consumer sources, and the exact origin must be verified on the Certificate of Analysis before compounding. The polymer backbone remains ethylene-vinyl acetate, but the reprocessing history of the recycled fraction can alter molecular weight distribution relative to first-pass EVA. Consequently, the material should be characterized against the same test battery used for virgin EVA foam: melt flow rate under ASTM D1238 at 190°C/2.16 kg, solid density under ASTM D792, and Shore hardness under ASTM D2240. Because the recycled fraction may shift these values relative to a virgin reference, DVR 002A should be qualified on the intended production line rather than by direct substitution without testing.

The product’s primary application space is footwear midsole and outsole production, foam sheet, and thermoformable foam blanks. In compression-molded midsole compounding, the recycled fraction can introduce a broader gel-particle distribution, particularly if the recycled feedstock includes crosslinked EVA foam scrap. A screen pack of 40/60 mesh is therefore recommended during melt filtration to protect downstream injection nozzles and hot-runner gates. Processors should monitor pressure upstream of the screen pack; a pressure rise above 8–10 MPa within a single shift indicates gel accumulation and requires screen replacement. These operational boundaries derive from production-scale twin-screw compounding lines with L/D ratios of 40:1 to 52:1; published data for DVR 002A in this specific configuration is limited. The recycled fraction can also affect color consistency, requiring inline optical inspection or spectrophotometric lot checks if visible surface uniformity is a finished-part requirement.

What limits the substitution of DVR 002A in crosslinked foam versus virgin EVA?

The main substitution limit is the cure/rheology interaction in crosslinked EVA foam. In typical midsole formulations, dicumyl peroxide decomposes between 150°C and 180°C to generate free radicals for crosslinking, while azodicarbonamide decomposes between 190°C and 210°C to release the gas that forms the cell structure. The recycled fraction may contain residual peroxide decomposition products, partial gel, or oxidized species that consume free radicals, thereby shifting scorch time and optimum cure time. A moving die rheometer test per ASTM D5289 should be run on every compounded batch to establish the lot-specific cure curve. Virgin EVA foam grades typically show a scorch time t_s2 of 1.5–3.0 min at 170°C; DVR 002A may deviate from this range, and published data for this specific configuration is limited. The formulation should not use amine-based additives, because they can accelerate peroxide decomposition or interfere with the acid-base balance of the blowing-agent system.

When the material is processed on injection-molding machines, the melt temperature should remain within the EVA foam processing window of 170–190°C, with mold temperatures between 160°C and 185°C to allow foam expansion without surface splay. Clamp force requirements on medium-format footwear molds range from 1,500 kN to 4,000 kN depending on cavity count and projected area; venting depth of 0.03–0.05 mm on parting lines is critical because residual moisture and low-molecular-weight volatiles from recycled content can cause gas entrapment. Pre-drying at 60–70°C for 2–4 h is required when ambient relative humidity exceeds 60% or surface moisture exceeds 0.1 wt% by Karl Fischer titration. The use of desiccant-bed dryers is preferred; hot-air hopper dryers may not achieve the required dew point below -20°C. Screw-back pressure should be set between 5–10 MPa to homogenize the melt without excessive shear heating from the recycled fraction.

Property verification across recycled-content footwear foam

The values above represent general EVA foam and footwear-grade ranges and are not DVR 002A lot specifications. Each property must be re-established on the actual recycled-content batch because the recycled fraction can influence density and hardness through microgel formation, foaming-agent efficiency loss, or ash content. The product should be compared with a virgin EVA reference compound in the same cavity and same cycle time to isolate the effect of recycled content on demolding and cell structure.

Relative to Braskem’s virgin EVA foam grades, DVR 002A differs primarily in melt-filtration requirement, odor management, and traceability documentation rather than in basic polymer class. In high-volume footwear lines, recycled content can create batch-to-batch odor fluctuations from residual adhesives, printing inks, or packaging residues; gas chromatography–mass spectrometry headspace screening is recommended when the molded part is enclosed in retail packaging. The product is not positioned for transparent film, medical film, or food-contact packaging unless the specific lot has been independently validated under FDA 21 CFR 177.1520 or equivalent migration test conditions. For footwear, REACH Annex XVII restricted-substance testing is required on the finished article because recycled feedstocks may introduce trace heavy metals, phthalates, or chlorinated paraffins at concentrations that virgin EVA would not contain.

The specification difference from a general-purpose EVA copolymer is the intended foam and footwear end-use. Grades for film or hot-melt adhesives typically have vinyl acetate contents above 28 wt% and melt flow rates above 10 g/10 min; DVR 002A is positioned for foam and footwear where vinyl acetate content is typically 15–28 wt% and melt flow is lower to provide melt strength during cell growth. The exact comonomer content of DVR 002A is not stated in this document because the published datasheet may be revised; lot-specific values should be confirmed by Fourier transform infrared spectroscopy or the method indicated on the Certificate of Analysis. Melt strength remains a controlling variable for cell coalescence prevention; standard capillary rheometry with haul-off attachment per ISO 16790 or equivalent can be used on the compounded lot.

In compression-molded midsole production, the compound is typically pre-blended with 2.0–4.0 phr azodicarbonamide and 0.5–1.5 phr dicumyl peroxide, then sheeted on a two-roll mill at 80–100°C and cured in a multi-opening press at 150–170°C for 8–15 min. The recycled fraction may reduce the effective blowing-agent yield because some volatiles escape during early mastication. To maintain expansion ratio, the blowing-agent dose may require an incremental adjustment of 0.2–0.5 phr, but only after expansion-ratio trials are conducted on the same press. Expansion ratio is measured by comparing the density of the crosslinked foam to the solid compound density per ASTM D792; typical footwear midsole foams target 0.20–0.35 g/cm³.

Injection-molded EVA foam for full-shoe clogs or footbeds requires a different balance: the melt is injected into a cooled or partially cooled mold cavity and the foaming occurs during mold opening or core-back. For DVR 002A, the injection speed should be kept moderate to high, with a filling time of 0.3–1.0 s for thin wall sections, because prolonged residence time at melt temperatures above 190°C can degrade the recycled fraction and produce black specks. A check ring with a clearance below 0.05 mm is recommended to prevent melt leakage caused by viscosity fluctuations. Cavity pressure sensors can identify the point at which foam expansion begins; mold opening should be delayed until the part surface reaches 70–85°C to reduce cell collapse.

Sheet foam extrusion on a single-screw extruder with a cooled blown-film-style die requires a screw with a barrier section and L/D ratio of 30:1 to 36:1. The head pressure should remain below 25 MPa to avoid premature gas release at the die lip. For DVR 002A, processing starts at a die temperature of 120–140°C and a melt temperature of 165–185°C; the actual conditions depend on blowing agent type. Recycled content may require a finer melt filter, typically a 40/60/100 mesh stack, to remove particles larger than 150 µm. The sheet line should include thickness scanning at the die exit because the recycled fraction can produce local density bands that affect downstream thermoforming wall-thickness consistency.

Lot-to-lot variability in recycled-content EVA is managed through incoming inspection. A standard receiving protocol should include melt flow rate per ASTM D1238, moisture by Karl Fischer titration, ash content per ASTM D5630 or ISO 3451-1, and a pressed-film gel count using a 0.5 mm film and a transmitted light viewer. The gel count specification must be agreed with the supplier; published data for this specific configuration is limited. Fourier transform infrared spectroscopy can verify the vinyl acetate content by the ratio of the 1240 cm⁻¹ and 1465 cm⁻¹ absorbances. The recycled content claim of 50% should be supported by the supplier’s mass balance or segregated supply-chain documentation, and retained lot samples should be stored for at least 24 months to allow retrospective testing if finished footwear complaints arise.

Within the WENEW portfolio, grades intended for rigid packaging or film may have different rheology packages, additive loading, and cleanliness standards. DVR 002A is specifically designated for foam and footwear; substituting a general-purpose recycled EVA from another portfolio position may result in poor cell structure because of insufficient melt strength or excessive volatiles. The foam and footwear grade designation implies that the producer has selected feedstocks and controlled ash and gel levels appropriate for expanded parts; this is not automatically true of recycled EVA grades developed for extruded profiles or adhesives. Storage conditions before processing should be dry and below 35°C ambient temperature, with opened packages consumed within 72 h or resealed under nitrogen to prevent moisture uptake and aldehyde-generating oxidation.