HANWHA EVA 1328 (em inglês)

Compounding HANWHA EVA 1328 for compression-molded footwear midsoles begins with mastication on a two-roll mill at 80–95 °C or in an intermeshing internal mixer with discharge temperature not exceeding 110 °C. The vinyl acetate content of 28 wt% reduces crystallinity relative to low-VA EVA grades and permits the addition of azodicarbonamide at 2.0–4.0 phr, dicumyl peroxide at 0.6–1.0 phr, zinc oxide at 0.5–1.5 phr, stearic acid at 0.3–0.8 phr, and precipitated calcium carbonate at 0–15 phr. DCP must be added last at a stock temperature below 105 °C; a torque rise of 10 % above the rheometer minimum torque at 150 °C is commonly used as the scorch threshold in production control. The MFR of HANWHA EVA 1328 is specified at 3 g/10 min under ISO 1133-1:2022, condition 190 °C/2.16 kg, and this moderate melt strength supports closed-cell expansion during press curing at 160–175 °C for 7–12 min. Final midsole density is controlled between 0.12 g/cm³ and 0.25 g/cm³ by adjusting blowing agent ratio, mold filling ratio, and cure ramp; tensile properties are evaluated under ASTM D3574-17 and tear resistance under ASTM D624-20. Batch-to-batch density drift is observed when recycled edge trim content exceeds 10 wt%, as crosslinked domains cannot homogenize with fresh compound.

Moisture on the vinyl acetate phase is less severe than in polyester elastomers, but pre-drying at 60 °C for 2 h is recommended when storage RH exceeds 60 %; residual moisture above 0.05 wt% produces surface blisters during expansion. Mold release agents requiring amine-functional chemistries should be excluded because basic species accelerate vinyl acetate hydrolysis above 180 °C, creating acetic acid odor and surface tack. The same restriction applies to recycled compound contaminated with polyamide edge trim.

Why Does Filler Wetting Govern IEC 60332-1-2 Performance in EVA 1328 Sheathing?

The polar vinyl acetate phase of HANWHA EVA 1328 permits aluminum trihydroxide loadings up to 180 phr without the gross phase separation observed in LLDPE-based halogen-free flame retardant compounds at equivalent filler volume fractions. A practical compounding formulation consists of EVA 1328 at 100 phr, aluminum trihydroxide at 100–180 phr, magnesium dihydrate at 20–60 phr, zinc borate at 5–12 phr, silane coupling agent at 0.3–1.0 phr, hindered phenol antioxidant at 0.3–0.8 phr, and processing aid at 1–3 phr. Because the MFR is 3 g/10 min, the melt viscosity is higher than HFFR grades designed for high-speed sheathing; twin-screw compounding should be performed on lines with L/D ≥ 40:1, downstream side feeding at 40–60 % of total filler addition, and barrel temperatures held at 130–160 °C. Processing above 180 °C triggers premature ATH dehydration, generating water vapor porosity and increasing sheath surface roughness.

Flame performance is verified by IEC 60332-1-2:2015 vertical flame propagation; compounds with ≥ 160 phr ATH commonly achieve the charred-portion criterion, but published data for this specific EVA 1328 configuration is limited and should be confirmed on the actual cable construction. Acid gas emission under IEC 60754-1:2011 requires pH ≥ 4.3 and conductivity ≤ 10 µS/mm; smoke density under IEC 61034-2:2005 is typically specified as light transmittance ≥ 60 %. The limiting oxygen index determined under ISO 4589-2:2017 can exceed 36 % with ATH loadings above 160 phr, but tensile strength drops steeply at filler volume fractions above 45 vol%.

Extrusion of closed-cell crosslinked sheet from HANWHA EVA 1328 depends on decoupling blowing agent decomposition and peroxide crosslinking kinetics. Azodicarbonamide decomposes near 195–205 °C, while dicumyl peroxide enters rapid decomposition above 170 °C; a two-stage forced-air oven with first zone set at 165–175 °C and second zone set at 200–215 °C is employed to initiate cure before full gas evolution. Sheet thickness in continuous electron-beam crosslinking is restricted to 5 mm or less at absorbed doses of 60–120 kGy, because dose penetration gradients produce uneven crosslink density. The vinyl acetate content of 28 wt% lowers the crystalline melting point and improves impact flexibility at low temperature, while final foam density between 0.08 g/cm³ and 0.20 g/cm³ is achieved by adjustment of blowing agent at 3–8 phr, not by screw speed changes alone.

Production-scale equipment behavior shows that open-mill blending before sheet extrusion must hold stock temperature below 105 °C; localized hot spots above 125 °C create pre-crosslinked gel particles that appear as hard inclusions in calendered sheet. Cell structure is assessed by image analysis of cross sections from ASTM D3574-17 foam specimens, and compression force deflection is measured under ASTM D3574-17 Test C. Pre-drying at 60 °C for 2 h is necessary when pellet moisture exceeds 0.05 wt%, particularly after storage in unlined bulk containers in ambient conditions above 70 % RH. Outdoor exposure of unpigmented EVA foam sheet causes surface oxidation; carbon black at 2–3 wt% or UV absorber packages are required for automotive interior components with service life exceeding 10 years.

Flexible Extruded Gasket Compounds and Continuous Service Temperature Boundaries

Blends of HANWHA EVA 1328 with linear low-density polyethylene in 70:30 to 50:50 ratios are extruded through single-screw lines of L/D 24:1–30:1 with compression ratio between 2.5:1 and 3.5:1. Barrel temperatures are maintained at 130–150 °C and die temperature at 150–170 °C; higher EVA fraction reduces Shore A hardness and increases elongation at break, but the continuous service temperature should remain at least 10 °C below the Vicat softening point of the compound. The density of EVA 1328 is 0.950 g/cm³ under ASTM D792-20, and melt flow rate is 3 g/10 min under ISO 1133-1:2022, which imposes lower output rates than LDPE extrusion grades and requires breaker plates with 20–30 % open area to control head pressure.

Weatherability limits are defined by vinyl acetate content. Outdoor gasket profiles in black formulations require carbon black dispersion at 2–3 wt% with a micropelletized carrier that does not introduce moisture; non-black compounds require hindered amine light stabilizer at 0.2–0.5 wt% and a benzotriazole UV absorber at 0.2–0.5 wt%. Tensile strength and elongation at break are tested under ISO 37:2017 using type 2 dumbbells, and compression set is determined under ISO 815-1:2019 at 23 °C for 24 h. Silicone-based external lubricants are preferred over amide-based slip additives because amide migration can accelerate surface oxidation of the vinyl acetate phase.

When Mass-Loaded Acoustic Barrier Compounds Require EVA 1328 as the Polymeric Matrix

In counter-rotating twin-screw compounding of mass-loaded acoustic barrier sheet, EVA 1328 serves as the binder for barium sulfate at 300–600 phr, calcium carbonate at 50–150 phr, zinc stearate at 1.5–3.0 phr, paraffinic processing oil at 5–15 phr, and stearic acid at 0.5–1.0 phr. The polar vinyl acetate phase wets high-specific-gravity filler surfaces more effectively than nonpolar polyolefin binders, and the moderate melt flow rate of 3 g/10 min permits the compound to enter a calendering gap without edge tearing. Barrel temperatures are held at 130–160 °C with vacuum venting at -0.08 MPa to remove moisture introduced by mineral fillers. Sheet thickness of 2–5 mm is calendered and cooled on polished rolls; density reaches 2.0–2.5 g/cm³ depending on filler loading.

Sound transmission loss is measured under ISO 10140-2:2021 in a coupled reverberation chamber; mass-law behavior dominates above the coincident frequency, but low-temperature flexibility remains sufficient for trimming and thermoforming. Published data for EVA 1328 in this specific configuration is limited, so pilot-scale trials should compare mass per unit area at 2 kg/m² and 5 kg/m² against candidate filled EPDM or PVC barriers. Process limitations include screw torque rise when barium sulfate loading exceeds 600 phr, and filler agglomerates above 75 µm create surface defects in thin-gauge sheet; mesh screening at 80 mesh is recommended before calendering.