EVAtech 160I/21 EVA Copolymer Compound,Crosslinkable Foam Grade

Chemically Crosslinked Footwear Midsole Foam: Peroxide Cure and Blowing Agent Window

EVAtech 160I/21, with a nominal vinyl acetate content of 16 wt% and a melt flow index of 2.1 g/10 min under ISO 1133-1:2022 conditions, is dry-blended at 100 phr with 3.0–4.0 phr azodicarbonamide, 0.9–1.2 phr dicumyl peroxide, 1.0–2.0 phr zinc oxide, 0.5–1.0 phr zinc stearate, and 5–15 phr calcium carbonate for chemically crosslinked footwear midsole stock. Mixing is performed in an internal mixer with a 75 L net chamber volume at rotor speed 35–40 rpm; the drop temperature is controlled between 115°C and 120°C because peroxide scavenging accelerates sharply above 125°C. The discharged batch is sheeted on a two-roll mill at 100–110°C with a nip gap of 1.5–3.0 mm and then cooled to 40–50°C before preform cutting. Molding is executed in a multi-platen compression press at 165–172°C for 10–14 min under 4–6 MPa; the functional processing window is approximately ±5°C because the dicumyl peroxide half-life at 170°C is close to 1 min, while zinc oxide-activated azodicarbonamide decomposition onset is depressed into the 155–165°C range. If crosslink density develops before sufficient gas liberation, expansion stalls above target density; if gas evolution outpaces melt strength, cell coalescence and split voids appear. Midsole foam density is controlled at 180–220 kg/m³, with Asker C hardness of 48–55, compression set below 30% after 6 h at 50°C under 25% deflection per ASTM D395-18 Method B, and tensile strength above 2.0 MPa when tested per ASTM D3575-20 Suffix T. Terminal products include die-cut midsoles, full-length wedge soles, molded sock liners, and heel inserts. Footwear components exported to the EU are normally screened for dimethyl fumarate under EU 2009/251/EC, REACH Annex XVII restrictions, and AFIRM RSL limits for extractable heavy metals, phthalates, and polycyclic aromatic hydrocarbons. Amine-based additives and sulfur donors must be excluded from regrind streams because they scavenge peroxide radicals and depress cure efficiency. Packed cartons should not be stored above 50°C to avoid permanent indentation and density gradients in finished midsoles.

For thermally insulating pipe sleeves and HVAC duct liner, EVAtech 160I/21 is formulated at substantially higher blowing-agent loading because the target density is far below footwear-grade foam. A starting-point formulation uses 100 phr compound, 12–16 phr azodicarbonamide, 0.6–0.8 phr dicumyl peroxide, 1.0–2.0 phr zinc oxide, 1.0–2.5 phr zinc stearate, and 10–30 phr magnesium hydroxide or aluminium trihydroxide where flame-retardant classification is required. The batch is fed to a single-screw extruder with L/D 24:1 and a screw compression ratio of 1:2.5; barrel temperatures are held at 95–115°C from feed throat to metering zone, while the die head is maintained at 105–120°C to prevent premature blowing inside the screw channel. The extrudate enters a continuous hot-air vulcanization oven at 190–230°C with line speed between 3 m/min and 8 m/min, where peroxide crosslinking and azodicarbonamide decomposition proceed simultaneously. The critical threshold is blowing-agent dosage: below 4 phr, density rises above 45 kg/m³ and thermal conductivity exceeds 0.042 W/(m·K); above 18 phr, cell walls rupture, closed-cell content drops below 90%, and visible internal fissures form. Target foam properties for pipe insulation are density 25–35 kg/m³, thermal conductivity 0.036–0.040 W/(m·K) at 25°C per ASTM C518-21, water vapour transmission below 0.10 perm·inch per ASTM E96/E96M-21, and water absorption by volume below 1% after 24 h immersion per ASTM D1056-20. The expanded sleeves, sheets, and duct liner are cut in thicknesses from 6 mm to 50 mm, often with acrylic adhesive backing applied after corona treatment to 38–40 dyn/cm surface energy. Compliance for chilled-water and HVAC service commonly references ASTM C534/C534M-23 for elastomeric cellular insulation and local building-code smoke and flame indexes. The main production bottleneck is oven temperature stratification: a cross-web temperature drop greater than 10°C creates a dense skin and low-density core, which increases post-compression thickness loss under insulation cladding.

Closed-Cell Lamination Rollstock for Automotive Interior Trim

Because automotive interior laminates require a thermoformable closed-cell core, EVAtech 160I/21 is calendered into rollstock with target density 45–70 kg/m³ and thickness 2–6 mm. A production-start formulation uses 100 phr compound, 4.5–7.0 phr azodicarbonamide, 0.8–1.1 phr dicumyl peroxide, 0.5–1.0 phr zinc oxide, 0.5–1.0 phr zinc stearate, and 1–3 phr color masterbatch. Calendering is run on a four-roll inverted-L calender with roll temperatures of 100–115°C; the final nip gap is matched to the calculated green-sheet thickness required for the expansion ratio. The sheet is then expanded in a rotocure oven at 170–190°C, followed by a post-cure tunnel at 80°C for 24 h to strip residual acetaldehyde and azodicarbonamide decomposition odor. Lamination to polyester, polypropylene nonwoven, or PVC facing is performed at 130–150°C with nip pressure of 0.5–1.0 MPa. The foam surface is embossed in-line to improve drape and reduce delamination on contoured door-panel substrates. The key process boundary is thermoformability: the crosslinked foam must soften between 120°C and 140°C without melting or shrinking more than 2% after forming. High crosslink density locks the cell structure and prevents deep-draw door-panel contours, while insufficient crosslink density permits cell collapse in the forming tool. Flammability is measured per FMVSS 302 or ISO 3795:1989/Amd 1:2016; the horizontal burn rate must not exceed 100 mm/min for automotive interior panels. Tensile strength above 0.3 MPa and elongation above 120% per ASTM D3575-20 Suffix T are commonly specified. Emission testing is referenced to VDA 278 or equivalent OEM methods when the rollstock is destined for passenger-compartment parts. Terminal products include die-cut headliner pads, door-panel cushion layers, dashboard crash-pad backing, parcel shelf liners, and HVAC blend-door seals. Compliance with REACH Annex XVII and the EU End-of-Life Vehicle Directive 2000/53/EC is relevant for EU-trimmed vehicles, and the compounded rollstock must be free from polybrominated diphenyl ethers for RoHS 2011/65/EU Annex II where applicable.

What Limits Compression Set in Appliance Gasket Foam Formulations?

Compression-set resistance in appliance gasket foam is governed by crosslink density and closed-cell geometry rather than bulk polymer hardness alone. For refrigerator door seals, HVAC access-panel gaskets, and air-filter frame seals, EVAtech 160I/21 is compounded with 100 phr polymer, 2.0–3.5 phr azodicarbonamide, 0.7–1.0 phr dicumyl peroxide, 0.5–1.0 phr zinc oxide, 0.3–0.8 phr zinc stearate, and 15–30 phr calcium carbonate or talc where dimensional stability is required. Mixing is conducted below 120°C to avoid scorch; the sheet is compression molded at 165–175°C under 3–5 MPa and then die-cut into gasket profiles. Target density is 120–180 kg/m³, firmness is usually in the Shore A 15–25 range when measured per ASTM D2240-15, and compression set after 22 h at 70°C under 25% deflection is held below 30% per ASTM D1056-20. The processing boundary is narrow: increasing dicumyl peroxide beyond 1.1 phr drives compression set below 20% but raises hardness above Shore A 30, producing closure force that exceeds refrigerator door-seal magnet pull and creates gapping in low-temperature service. Reducing peroxide below 0.6 phr leaves uncrosslinked domains that creep under repeated door-slam loading. Water absorption by weight should remain below 5% after 24 h immersion, and closed-cell content above 85% is required to prevent condensate uptake during freezer defrost cycles. Flame classification is frequently requested as UL 94 HF-1 on the final gasket profile. Because appliance gaskets must survive repeated compression at low temperatures, the foam is conditioned at -20°C for 4 h before compression testing to check cell-wall embrittlement. Terminal products include magnetic refrigerator door gaskets, HVAC panel seals, air-conditioner filter seals, and appliance access covers.

In fitness mat production, the calendered preform is expanded in a multi-opening press to produce sheet stock with density 50–70 kg/m³, tensile strength above 0.25 MPa, elongation above 150%, and tear strength above 1.5 N/mm per ASTM D624-00(2020) Die C. The starting formulation for EVAtech 160I/21 uses 100 phr compound, 5.0–8.0 phr azodicarbonamide, 0.8–1.2 phr dicumyl peroxide, 1.0–1.5 phr zinc oxide, 0.5–1.0 phr zinc stearate, and 10–20 phr calcium carbonate. Mixing is performed in a Banbury internal mixer at 35–40 rpm; the batch is dropped at 115–120°C and sheeted through a two-roll mill at 100–110°C. The preform is then crosslinked and expanded in a hydraulic press at 170–180°C for 12–18 min, with pressure released in a controlled step to prevent post-expansion shrinkage. The production conflict is the requirement for high tear strength in thin 8–15 mm mat stock without excessive density from overcrosslinking; increasing peroxide beyond 1.4 phr improves tear strength but pushes density above 75 kg/m³ and reduces perceived cushioning. For childcare and yoga products, compliance with EN 71-3:2019+A1:2021 migration limits for soluble elements is tested on the final mat, and REACH candidate-list screening is required for EU import. Gym flooring applications may specify surface resistivity below 10⁹ Ω per IEC 61340-2-3 only when antistatic carbon black is added; the base foam is not intrinsically antistatic. Terminal products include yoga mats, gymnastics landing mats, fitness mats, mobility pads, and die-cut protective floor tiles for martial arts studios.

If Blowing Agent Decomposition Is Depressed, Marine Buoyancy Foam Closed-Cell Content Falls Sharply

Pre-drying at 60°C for 2 h is applied when storage humidity exceeds 60% because moisture accelerates azodicarbonamide decomposition before the melt reaches full crosslink temperature and creates open porosity. For marine buoyancy inserts and fender pads, EVAtech 160I/21 is compounded with 100 phr polymer, 6–9 phr azodicarbonamide, 0.6–0.9 phr dicumyl peroxide, 1.0–1.5 phr zinc oxide, and 0.5–1.0 phr zinc stearate. The compound is extruded into rod or sheet profile and expanded in a heated mold at 170–180°C, then cooled under 0.3–0.5 MPa to stabilize cell dimensions. Target density is 35–55 kg/m³, closed-cell content above 90% when measured by gas displacement per ASTM D6226-21, and water absorption below 1 vol% after 7 days immersion per ISO 2896:2001. If the molding temperature falls below the azodicarbonamide decomposition window or blowing-agent dispersion is poor, closed-cell content drops below 90%, water uptake increases beyond 5 vol% after repeated compression cycles, and buoyancy retention in service is reduced below the design margin. Buoyancy aids using such foam are generally tested to ISO 12402-5 for personal flotation devices or ISO 12402-7 for materials and components, but the foam alone does not constitute a certified device without the full garment assembly and approval. Terminal products include foam inserts for life jackets, buoyancy blocks for floating cables, dock fender cores, aquatic therapy kickboards, and impact-absorbing hull gaskets. Mixing equipment must be thoroughly purged when switching from EPDM formulations because sulfur donors and amines depress peroxide efficiency and create surface tack in the final foam.