SINOPEC Sanren EVA 14/15

During two-stage compression moulding of crosslinked closed-cell EVA compounds, the semi-crystalline character of a 14% vinyl acetate copolymer with MFR 15 g/10 min (190 °C/2.16 kg, ASTM D1238-23) governs the partitioning of azodicarbonamide decomposition gas between polymer melt and nucleating filler, and this partitioning is the principal control on mould splitting. In a Banbury internal mixer with ram pressure held at 0.5–0.6 MPa, EVA 14/15 is charged at rotor temperatures of 90–110 °C; zinc oxide 0.5–1.2 phr, zinc stearate 0.4–0.8 phr, and precipitated calcium carbonate 0–20 wt% are added before the blowing agent azodicarbonamide 2.5–4.5 phr and dicumyl peroxide 0.7–1.2 phr are incorporated on a two-roll mill at 85–105 °C. The peroxide is the limiting thermal boundary: single-point temperature excursions above 120 °C during compounding initiate scorch, visible as hard gel particles in the calendered sheet and as irregular cell size after expansion. The 14% VA content is low enough to retain sufficient crystalline domains for dimensional stability after demoulding, yet high enough to prevent the excessive stiffness associated with LDPE foam at densities below 0.20 g/cm³.

The forming sequence for midsole preforms consists of calendering the compounded sheet at roll temperatures of 75–85 °C, blanking, then placing the preform into a compression mould at 160–175 °C under 10–20 MPa for 15–20 min, followed by cold-stabilisation in the opened press before ejection. Multi-zone foaming ovens used in continuous sheet production are typically configured with a first zone at 155–165 °C, a second at 170–180 °C, and a cooling zone below 50 °C; density drift is observed when zone-to-zone variation exceeds ±3 °C because ADC decomposition kinetics change by roughly a two-fold rate factor over a 10 °C interval. Overblowing with ADC above 4.5 phr in thick sections produces coalesced internal voids and a characteristic split along the heat-sealed edge; underblowing below 2.5 phr leaves a high-density skin and a partially fused core, causing hardness variation across the sheet of more than 5 Shore A points when tested to ISO 868:2003.

Compliance for foamed EVA articles is not a single resin certification but a matrix of article-based restrictions: footwear and skin-contact mats are commonly evaluated against REACH (EC) No 1907/2006 Annex XVII entries 50 and 51 for restricted polycyclic aromatic hydrocarbons and phthalates; children’s play mats fall under EN 71-3:2019+A1:2021 migration limits for nineteen elements when the material is classified as a toy. Physical property reporting for quality control of the foam is anchored to ISO 1798:2008 for tensile strength and elongation, ISO 1856:2018 for compression set at 50% constant deflection, and ASTM D3574-17 shall not be applied because the substrate is not polyurethane. Terminal article types produced from this process are EVA midsoles, slippers, anti-fatigue mats, impact-protective padding, and crosslinked EVA foam sheet subsequently dyed or embossed.

A slot-die coating line for packaging hot-melt adhesives using EVA 14/15 requires controlled melt temperatures above 160 °C because the MFR 15 g/10 min (ISO 1133-1:2022) places the copolymer near the low-viscosity end of standard EVA packaging grades, and below 150 °C the melt pressure upstream of the coat hanger die may limit coating-weight control, causing edge bleed and uneven deposition. EVA 14/15 is incorporated at 25–35 wt% with a hydrogenated hydrocarbon tackifier at 35–45 wt%, microcrystalline wax at 15–25 wt%, and hindered phenolic antioxidant at 0.3–0.8 wt%; the low 14% vinyl acetate content is deliberately selected when heat resistance and reduced surface tack of the finished adhesive film are more important than aggressive peel strength, so the tackifier phase should be selected to avoid brittle failure during carton side-seam flexing at low board temperatures.

Production-scale mixing is performed in a jacketed sigma-blade mixer at 140–170 °C under nitrogen blanketing; melt residence time is limited to 60–120 min, because prolonged exposure of low-vinyl acetate EVA in aliphatic tackifier systems leads to viscosity drift and oxidation, although published data for this specific Sanren grade in high-tackifier formulations is limited. A gear pump transfers the melt to a slot-die coater with lip gap 0.25–0.40 mm, applying 18–40 g/m² onto clay-coated board or kraft paper; line speeds between 40 m/min and 80 m/min are feasible only when the adhesive film temperature at the nip remains above 90 °C. Indirect food-contact formulations are governed by FDA 21 CFR 175.105 for adhesives used in packaging, while EU compliance is evaluated under Regulation (EC) No 1935/2004 through end-article testing; no direct food-contact declaration is available for the raw EVA 14/15 unless the finished article passes specific migration limits under Commission Regulation (EU) No 10/2011 where applicable. Terminal types are case and carton sealing, bookbinding adhesives, paper-to-board lamination, and profile wrapping; the grade is not recommended for pressure-sensitive adhesive tapes or freezer-grade label adhesives, where a vinyl acetate content above 18% is normally required to maintain tack below -20 °C.

What Happens to Melt Filtration Pressure When Carbon Black Loading Exceeds 35 wt%?

In twin-screw compounding of carbon-black additive masterbatches, EVA 14/15 functions as a high-flow carrier at filler loadings between 30 wt% and 50 wt%; the low crystallinity relative to LDPE allows wetting of high-surface-area carbon black without requiring melt temperatures above 170 °C. Screen-pack differential pressure remains stable below 35 wt% carbon black when a 250 μm screen is preceded by a 600 μm breaker plate; above 40 wt% carbon black, agglomerate bridging increases pressure drop across a 100 cm² screen pack beyond the linear mass-flow trend, and filtration capacity must be increased rather than accepting lower throughput. Published data for this exact EVA 14/15 grade at the upper filler limit is limited; in-line melt pressure logging is required for scale-up. The formulation range consists of EVA carrier at 50–70 wt%, pigment or filler at 30–50 wt%, and processing lubricant at 0.5–2.0 wt%.

The compounding process is operated on a co-rotating twin-screw extruder with L/D 40:1 to 48:1 and barrel zones set at 120–170 °C; screw speed is held between 300 rpm and 600 rpm depending on black grade and specific energy input, which typically remains below 0.30 kWh/kg. Strand and underwater pelletizing are both used; strand pelletizing gives lower dust but requires cooling water below 20 °C to prevent pellet fusion at the EVA carrier’s low Vicat softening point. Compliance for masterbatches is controlled by the final article rather than by the carrier alone: packaging applications are assessed under EU Directive 94/62/EC for combined lead, cadmium, mercury, and hexavalent chromium below 100 mg/kg, electrical and electronic accessories under RoHS 2011/65/EU Annex II, and toy-related colorants under EN 71-3:2019+A1:2021. Terminal article types include black masterbatch for polyolefin extrusion and injection moulding, flame-retardant additive concentrates, anti-block concentrates for film, and processing-aid masterbatches used at let-down ratios between 2% and 8%.

Cold-Runner Pressure Drop Characteristics in 14% VA EVA

Injection moulding of EVA 14/15 into thin-wall flexible articles is performed with melt temperature set at 150–180 °C and nozzle pressure between 40 MPa and 80 MPa; the comparatively low melt elasticity of a 14% VA copolymer with MFR 15 g/10 min (ASTM D1238-23) reduces gate blush but increases cold-runner pressure drop when the runner diameter falls below 4.0 mm or the flow length exceeds 80 mm. EVA 14/15 is used neat or in blends with LDPE/LLDPE at 20–40 wt% to shift flexural modulus below that of pure LDPE; a higher addition fraction lowers the Vicat softening point, so thin-wall parts needing hot-water resistance are not formulated above 30 wt% EVA unless testing to ISO 306:2022 confirms the application boundary.

Process parameters include mould cooling at 20–50 °C, hold pressure 50–70% of peak injection pressure, and back pressure 0.5–1.5 MPa; screw recovery is set to keep melt residence below 15 min because EVA is prone to oxidation at processing temperatures when ventilation is inadequate. For direct food-contact parts such as jar lid liners, the raw EVA must conform to FDA 21 CFR 177.1350 for ethylene-vinyl acetate copolymers, subject to extraction limits and end-use temperature restrictions; EU declarations follow Regulation (EC) No 1935/2004 with migration testing under Commission Regulation (EU) No 10/2011 for the finished article. Terminal article types are anti-slip pads, appliance feet, flexible grip inserts, jar closure liners, and flexible floor-tile edge strips; the grade is not intended for transparent optical parts or high-pressure closures, where dimensional tolerance and gas-barrier performance require a different material class.

If Calender Roll Temperatures Exceed 85 °C, Surface Plate-Out Becomes the Controlling Defect

Solid extruded EVA sheet and non-slip profile lines operate on a 90 mm single-screw extruder with L/D 24:1 and a barrel profile of 130–165 °C; at these temperatures EVA 14/15 delivers a stable melt cone into a three-roll calender with roll surface temperatures held below 70 °C. The formulation uses EVA 14/15 at 85–100 phr, mineral filler 0–15 phr, and stearate processing aid 0.2–0.8 phr; no blowing agent or peroxide is present, so the process remains reversible and trims can be reground at 5–15 wt% without severe screw torque fluctuation. If the calender roll temperature drifts above 85 °C, low-molecular-weight VA-rich fractions migrate to the roll surface and deposit as a tacky film, producing surface defects on the sheet at intervals corresponding to the roll circumference; the corrective action is a roll-temperature reduction to 65–70 °C and a temporary increase in anti-blocking agent to 0.5 phr.

Article compliance for extruded EVA mats and profiles is destination-specific: EU general product safety is supported by REACH (EC) No 1907/2006 Annex XVII restrictions for phthalates and PAH in skin-contact articles; RoHS 2011/65/EU applies only if the profile is incorporated into an electrical appliance. Physical performance is normally reported by ISO 527-2:2021 for tensile properties and ISO 868:2003 for Shore A hardness; surface slip resistance of floor-contact mats is tested to AS 4586:2013 or equivalent national methods when the mat claims wet-area slip resistance. Terminal products are solid non-slip desk pads, kitchen drawer liners, industrial anti-vibration pads, edge protectors, and extruded bumper profiles; the absence of foaming permits a homogeneous skin with higher tear resistance than open-cell sheet but with reduced cushioning capacity.

Torque Rise and Cure Compatibility in EPDM/EVA Blends

In polymer blending operations, EVA 14/15 is introduced into EPDM at 15–30 phr in an internal mixer at 100–120 °C; the EVA phase reduces blend crystallinity and improves filler dispersion, but dicumyl peroxide addition at 0.5–1.5 phr with triallyl cyanurate co-agent at 0.5–1.0 phr causes a measurable torque rise during cure at 150–170 °C in moving-die rheometer testing to ISO 6502-2:2018. The maximum torque increases with EVA level because the vinyl acetate side groups participate in radical grafting and chain extension; published data for this specific Sanren grade in EPDM/EVA blends is limited, so blend scorch time must be measured before production lot release.

Mixing is completed on an internal mixer followed by a two-roll mill at 85–100 °C, then the batch is sheeted and fed either to a single-screw extruder or to compression/injection moulding; the presence of EVA lowers the blend’s oil resistance relative to pure EPDM when tested under ASTM D471-16a, so the blend boundary is set by the end-use environment. Compliance is assessed under REACH (EC) No 1907/2006 and RoHS 2011/65/EU when the vulcanizate enters electronic enclosures; automotive interior specifications may additionally require low-odour and low-VOC testing under VDA 278:2011 for emissions from non-metallic materials. Terminal article types are anti-vibration pads, flexible coupling components, soft-touch grip layers, and extruded sealing profiles where a compromise between EPDM weatherability and EVA processability is required.