Copolímero de acetato de vinilo de etileno EVAtech EVA 160I/62D

EVAtech EVA 160I/62D ethylene vinyl acetate copolymer is supplied as a pelletized thermoplastic resin in which the 160I series prefix is the manufacturer’s internal designation and the suffix 62D corresponds to a nominal Shore D hardness of 62. The material is produced by high-pressure radical copolymerization of ethylene and vinyl acetate, yielding a partially crystalline backbone with polar acetate side groups. This structure lowers the melting endotherm and increases adhesion to polar substrates when compared with a non-polar low-density polyethylene of equivalent melt flow rate. Lot-specific conformity is verified by ISO 8985 for vinyl acetate content, ISO 1133-1:2022 at 190 °C and 2.16 kg for melt mass-flow rate, ISO 1183-1 for density, ISO 868 for Shore D hardness, ISO 527-2 for tensile stress at break and elongation at break, and ISO 306 method A50 for Vicat softening temperature. The grade is not a direct replacement for high-density polyethylene in rigid load-bearing components because the flexural modulus and heat deflection profile differ; any substitution must be validated with the test standards applied to the finished article. Published data for this specific configuration is limited when processing conditions depart from the manufacturer’s technical data sheet.

What Reference Methods Define Conformance for the 160I/62D Grade?

The principal specification parameters are listed below. Values printed on the supplier’s certificate of analysis control lot release; the table identifies the accepted test methodology and the engineering role of each result.

Incoming resin release is governed by the certificate of analysis because the 160I/62D grade may vary across production campaigns. Fourier-transform infrared spectroscopy under ISO 8985 is used to confirm vinyl acetate content, while melt mass-flow rate by ISO 1133-1:2022 is checked on dried pellets. If the melt flow rate shifts beyond the supplier’s specified control band, the fill rate and screw speed on the conversion line must be adjusted. Hardness specimens are prepared by injection moulding or compression moulding after conditioning for 88 h at 23 °C and 50% relative humidity according to ISO 291; testing before conditioning will produce inflated hardness and reduced elongation. Density by ISO 1183-1 method A is used to convert extruder throughput from kg/h to volumetric output. These incoming checks detect off-specification material that could otherwise appear only as a processing failure, such as screw slippage or non-uniform melt temperature at the die. Published data for the tolerance bands used by the manufacturer for this specific grade is limited; the supplied certificate of analysis is the controlling reference.

Before melt conversion of the 160I/62D grade is attempted on a 25:1 L/D single-screw extruder, the hopper and feed throat are maintained below 45 °C to prevent pellet bridging. A general-purpose screw with a compression ratio of 2.5:1 to 3.5:1 is used, and the barrel profile is normally set from 150 °C in the rear zone to 190 °C in the metering zone, with the die held at 190–210 °C. These values are typical for ethylene-vinyl acetate copolymers in the Shore D 62 hardness class and must be adjusted for screw speed, backpressure, and throughput. The melt temperature is limited to 230 °C because thermal deacetylation releases acetic acid, which corrodes equipment and forms carbonized gel particles. On a 40 L/D co-rotating twin-screw extruder used for filler let-down, the mixing-section barrel temperatures are often set 5–10 °C below the feed section to compensate for viscous dissipation, and screw speed is capped at 200–250 rpm for this hardness class. Published data for the 160I/62D grade at the upper screw-speed boundary is limited; torque monitoring and melt-pressure deviation are used to define the stable operating window.

Thermal Degradation Thresholds and Purging Practice on Twin-Screw Lines

The main processing conflict in ethylene-vinyl acetate copolymer conversion is the narrow separation between the melt temperature required for homogenization and the onset of deacetylation. Acetic acid formation is inferred on the production line from an increase in melt-pressure fluctuation, a reduction in melt strength, and a sharp odour at the vent. For grades in this hardness class, melt residence time at 200 °C should not exceed 15–20 min, and the vacuum vent should be operated at -0.08 MPa to -0.09 MPa to strip low-molecular-weight volatiles. If the line stops for more than 30 min, the barrel is purged with low-density polyethylene or a commercial purge compound with a melt mass-flow rate of 2–4 g/10 min until head pressure stabilizes. Without such purging, carbonized acetoxy residue can accumulate on the screw root and barrel wall, producing black specks and reducing elongation at break measured by ISO 527-2. The resin is hygroscopically benign under normal ambient storage, but condensation exposure or relative humidity above 60% requires dehumidified drying at 60–70 °C for 2–4 h. If dynamic rheology is used for process evaluation, capillary rheometry under ISO 11443 at 190 °C and 230 °C provides shear-viscosity data; a universal master curve across all lots is not valid because comonomer sequence distribution shifts shear sensitivity.

Kinetic analysis of the deacetylation reaction by thermogravimetric analysis under ISO 11358-1 shows a mass-loss onset that depends on heating rate, atmosphere, and vinyl acetate content. In nitrogen at 10 K/min, the initial mass-loss step for ethylene-vinyl acetate copolymers in this class is commonly detected above 250 °C; under air the oxidative onset may be lower. These values are not finished-article service temperatures, because the melt residence time is far longer than the dynamic scan. Processing therefore uses the lower practical limit of 230 °C as a safety boundary. Acetic acid corrosion is particularly severe in condensation zones near the vent and in vacuum-pump exhaust; stainless-steel vent hardware and base-resistant seals are used where continuous operation above 200 °C is required. The purging material should have a melt flow rate of 2–4 g/10 min to provide adequate shear cleaning without excessive dilution. If the next production lot is a polyolefin with a lower processing temperature, the transition is performed by temperature ramping rather than an abrupt setpoint change to avoid formation of crosslinked gel particles at the interface.

In extruded profiles and injection-moulded components, the 160I/62D grade is selected for applications requiring a balance of Shore D 62 hardness, polar filler acceptance, and environmental stress crack resistance. On a 110-tonne hydraulic injection moulding machine, the shot volume is normally maintained between 30% and 70% of barrel capacity to limit residence time, and the melt cushion is held at 3–5 mm to avoid screw bottoming. Cavity pressure in ethylene-vinyl acetate copolymer is commonly observed in the 25–40 MPa range, but the value must be confirmed by short-shot studies on the specific mould. For extruded gaskets and profiles, a breaker plate with a 60/80/100 mesh screen pack is used to build backpressure and improve dispersion of calcium carbonate, silica, or flame-retardant additives. Adhesion to untreated aluminium or polar substrates is evaluated by ISO 4587 for lap shear or ASTM D903 for peel; results are strongly dependent on substrate surface energy, adhesive layer thickness, and vinyl acetate migration to the interface. In hot-melt adhesive systems, higher vinyl acetate grades are normally preferred because they provide lower melt viscosity and longer open time; the 160I/62D designation falls outside the typical hot-melt window based on its Shore D hardness and melt-viscosity class.

In wire and cable compounds, ethylene-vinyl acetate copolymers in this hardness class are used as the base resin for semiconductive screens or low-smoke halogen-free jackets when formulated with magnesium hydroxide or aluminium trihydrate. Filler loadings of 50–65 wt% are common in low-smoke halogen-free systems, and the vinyl acetate group improves filler wetting relative to LDPE. Because the flame-retardant filler increases melt viscosity and heat dissipation during mixing, the rotor speed and ram pressure of an internal mixer are adjusted to keep the batch temperature below 180 °C. Dispersion is assessed by ash content and by tensile elongation retention after ageing; the relevant test methods include ISO 527-2 and ISO 188 for accelerated ageing. Published data for this specific grade in heavily filled low-smoke halogen-free jackets is limited, and a pilot batch on the target production line is required before scale-up.

The 160I/62D grade may also be employed as a modifier for polyethylene or polypropylene to improve impact strength and filler acceptance. When blended at 5–20 wt% into recycled polyethylene, the vinyl acetate phase lowers the brittle transition temperature and increases melt strength of the blend. The blend is typically prepared on a twin-screw extruder with distributive mixing elements; the dispersed EVA domain size is measured by scanning electron microscopy after cryo-fracture and is correlated with notched impact energy under ISO 179-1. Addition above 20 wt% can reduce tensile modulus below the target specification; the optimum loading is determined by a design-of-experiments matrix rather than a fixed rule.

When the 160I/62D Grade Is Compared with LDPE and EMA in Flexible Sealing Applications

The selection among ethylene-vinyl acetate copolymer, low-density polyethylene, and ethylene-methyl acrylate is governed by adhesion to polar substrates, thermal stability during melt conversion, and low-temperature flexibility. Under ISO 4587 lap-shear testing on untreated aluminium, ethylene-vinyl acetate grades in the Shore D 62 class generally show higher joint strength than LDPE of equivalent melt flow rate because the acetate carbonyl increases surface polarity. This adhesive advantage decreases on corona-treated polypropylene, where the substrate surface energy becomes the limiting variable. By contrast, ethylene-methyl acrylate has no acetate side group; it therefore generates less acetic acid during prolonged melt processing at temperatures above 220 °C and may exhibit better colour retention and lower vent corrosion in white or colour-compounded articles. The 160I/62D grade is differentiated from lower-hardness EVA grades by higher Vicat softening temperature and lower elongation at break, which may favour dimensional stability under light load. Comparative substitution studies should be conducted on the same injection moulding machine and with identical specimen preparation protocols; published data for direct substitution of the 160I/62D grade in all sealing formulations is limited.

Regulatory suitability of the 160I/62D grade is established only by the supplier’s food-contact statement and lot-specific compliance documentation. Ethylene-vinyl acetate copolymers may be formulated to comply with 21 CFR 177.1350 for food-contact articles and with EU 10/2011 as amended for plastic materials intended to contact food, subject to vinyl acetate monomer migration limits and specific migration testing under EN 1186 and EN 13130. The grade is normally expected to contain no intentionally added cadmium, lead, mercury, or hexavalent chromium and to meet the restriction limits referenced in IEC 62321 when accompanied by a RoHS conformance certificate. REACH compliance is an article-level obligation under Regulation (EC) No 1272/2008 and Regulation (EC) No 1907/2006; the safety data sheet identifies registration numbers, harmonized classification, and any substances of very high concern. No claim of FDA, EU, REACH, or RoHS approval is made from this technical introduction without the lot-specific compliance documentation.