EVAtech EVA 150I/15A Ethylene Vinyl Acetate Copolymer

EVAtech EVA 150I/15A is a high-melt-flow ethylene-vinyl acetate copolymer supplied in pellet form. The grade designation encodes a nominal melt flow rate of 150 g/10 min at 190°C and 2.16 kg, and a nominal vinyl acetate content of 15 wt%. The polymer is a random copolymer of ethylene and vinyl acetate produced by high-pressure radical polymerization; the incorporated acetate groups shorten the continuous ethylene sequences, reduce crystallinity, and create a semi-flexible polyolefin with greater polarity than low-density polyethylene. The material is neither chemically crosslinked nor reactive; it remains a thermoplastic that can be re-melted and diluted with olefinic polymers, tackifiers, oils, or fillers. Typical uses include injection moulding, thin-wall flow, compounding, and adhesive intermediates where low melt viscosity, low processing temperature, and moderate adhesion to polar surfaces are required. All numerical values quoted here are designation-level or representative reference ranges; the lot certificate of analysis remains the authoritative source for a specific production batch.

Material Identity and Grade Nomenclature

The EVAtech EVA 150I/15A falls within the medium-VA segment of the EVA product family. The 150I portion of the designation is read as melt flow rate of 150 g/10 min under ISO 1133-1:2022 or ASTM D1238-20 at 190°C/2.16 kg. The 15A portion is read as 15 wt% vinyl acetate, which is commonly reported on the certificate of analysis by infrared spectroscopy or saponification titration. The density of a 15 wt% VA EVA is generally in the range of 0.937 to 0.940 g/cm³ when measured by ISO 1183-1:2019; this places it above EVA grades with 28 wt% VA and below LDPE. The melting peak measured by differential scanning calorimetry is typically observed between 88°C and 96°C depending on cooling rate and thermal history. Because VA content inversely affects stiffness and MFR inversely affects melt viscosity, this grade occupies a narrow processing window: low enough VA to retain usable strength and thermoplastic set, but high enough MFR to fill thin sections at moderate injection pressure.

For injection moulding operations, the 150I/15A grade is usually processed at melt temperatures between 170°C and 210°C. The high MFR allows filling of thin-wall cavities at lower hydraulic pressure than a 25 g/10 min EVA; however, the same high MFR increases flash sensitivity in worn tooling, so clamp force and parting-line maintenance are more critical than for lower-flow grades. General-purpose polyolefin screws with compression ratios between 2.5:1 and 3.5:1 are adequate; high-shear barrier screws are not required, and excessive shear should be avoided because the ethylene-vinyl acetate backbone is less thermally stable than polyethylene homopolymer. Pre-drying is not mandatory for dry, room-temperature storage, but pellets exposed to relative humidity above 60% for more than 48 h may require tray drying at 60°C to 70°C for 2–4 h to prevent splay. On co-rotating twin-screw compounding lines with L/D ratios of 40:1 to 52:1, pelletized 150I/15A feeds reliably when the feed throat is water-cooled; bridging is more common with high-regrind blends or with wax-coated masterbatch pellets. Melt pressure during compounding typically builds along the first kneading block; a barrel profile with a flat 170–190°C initial zone and short residence above 200°C reduces deacetylation and screw corrosion.

Capillary rheometry on high-melt-flow EVA demonstrates shear-thinning with substantially lower viscosity than a 25 g/10 min EVA; the exact curve for 150I/15A should be measured on the production lot because melt flow rate does not fully define shear viscosity. In thin-wall injection moulding, the low zero-shear viscosity reduces gate pressure and enables filling of sections as thin as 0.8 mm in multi-cavity tools, provided that mold surface temperature is maintained above 15°C and venting depth is kept appropriate for polyolefin moulding. Short-shot defects in this grade are more commonly caused by insufficient venting or premature gate freeze than by high melt viscosity. Gate-freeze time is short because of the high MFR; this is beneficial for cycle time but restricts packing efficacy in thick sections. In sections above 4 mm, packing pressure must be applied before gate freeze, and a screw cushion of 3–5 mm is recommended. Because the copolymer has low thermal conductivity, cooling time scales with the square of wall thickness; mold temperature control units with turbulent flow and water-line diameters of at least 10 mm are used to maintain surface finish and reduce warpage.

What Changes When Vinyl Acetate Content Moves to 28 wt%?

The distinction between a 15 wt% VA grade and a 28 wt% VA grade is not only polarity; it changes melting point, tensile set, chemical resistance, and adhesion. A 15 wt% VA EVA retains enough crystallinity to provide mechanical integrity at room temperature, while the 28 wt% VA material becomes softer, lower in modulus, and tackier. Published DSC data for EVA copolymers show peak melting endotherms moving from roughly 90°C at 15 wt% VA to below 80°C at 28 wt% VA; the exact value depends on thermal history and comonomer sequence distribution. The EVAtech 150I/15A therefore differs from many 28 wt% EVA products less in melt flow than in final part character: it is selected when a polyolefin must remain semi-rigid, easier to demould, and less sensitive to blocking, while still offering better stress-crack resistance and low-temperature flexibility than LDPE. Conversely, if the application requires maximum adhesion to polar substrates, low Shore hardness, or high filler acceptance, a 28 wt% or 40 wt% VA grade is normally substituted. Compared with metallocene ethylene-octene plastomers of similar density, the EVA grade exhibits stronger acid-base interactions with cellulosic and metal oxide substrates but lower hydrolytic stability; prolonged water exposure can lead to surface haze and loss of adhesion. Compared with maleic anhydride-grafted EVA, 150I/15A has no reactive polar functionality; adhesion to metals and glass is therefore physical rather than covalent. In polymer blends, the unmodified EVA is used as a non-reactive flexibilizer, whereas anhydride-modified EVA is required when covalent bond formation with polyamide or polyester is needed.

Application selection for EVAtech EVA 150I/15A is governed by the balance of high flow and moderate VA content. Injection-moulded footwear components such as midsoles, insoles, and footbeds are common because the material flows long distances in multi-cavity tools and can be blended with LDPE, EPDM, or SEBS to tune compression set and hardness. In flexible packaging, the copolymer is not usually used alone as a sealant because the 15 wt% VA level gives a higher seal initiation temperature than EVA grades with 18–28 wt% VA; however, it is added as a processing aid to low-MFR LLDPE film grades to reduce extrusion pressure and improve bubble stability. In hot-melt adhesive formulations, the high MFR of the 150I/15A allows fast wet-out when combined with rosin ester or hydrocarbon tackifiers and paraffin wax; the 15 wt% VA level limits low-temperature adhesion relative to 28 wt% EVA, making the grade better suited to medium-temperature packaging and bookbinding rather than deep-freeze label systems. Published data for this specific configuration in high-speed hot-melt coating lines is limited; line-speed trials on equipment with slot-die coaters at 160–180°C are recommended before specifying the grade. In polymer compounding, the product is also used as a carrier-free viscosity modifier in masterbatch formulations where high let-down ratios require fast melt incorporation.

Thermal Degradation and Corrosion Management in Processing Equipment

Thermal degradation of EVA is dominated by deacetylation of the vinyl acetate comonomer. At temperatures above 220°C, acetic acid is liberated, which contributes to odour, discolouration, and corrosion of carbon steel tools, barrel surfaces, and mold vents. The 150I/15A is therefore not processed on equipment without corrosion-resistant facings when melt temperatures exceed 210°C. Production lines using hardened steel screws and bimetallic barrels can still be affected at the die plate, where acidic vapour condenses on cold surfaces. Stainless steel or chrome-plated die faces and vent port liners are recommended for continuous operation above 200°C. When vented barrels are used, vacuum devolatilization at -0.08 to -0.09 MPa assists removal of acetic acid and low-molecular-weight degraded products. The practical melt-temperature ceiling for a 15 wt% VA grade in injection moulding is 210°C for residence times below 5 min; higher temperatures are tolerated only with short-cycle injection or in continuous compounding where residence time is controlled. Additive packages containing amine-based antistatic agents, ammonium-based flame retardants, or high-pH metal oxides can accelerate yellowing and should be avoided unless specifically validated. Because the comonomer also reduces oxidative stability compared with LDPE, standard phenolic and phosphite antioxidant packages are required; the absence of antioxidants in regrind or masterbatch dilutions is a common cause of gel formation and viscosity shift.

Storage in an unheated warehouse does not degrade the resin, but the pellet surface may condense moisture during rapid temperature swings. Bags should be kept closed and pallets should be conditioned for 24 h before opening if the outdoor temperature is below 10°C and the production hall is above 25°C. The product is not hygroscopic in the same manner as polyamide, but surface moisture is sufficient to cause splay in high-flow injection moulding. If a hot-melt adhesive line uses 150I/15A as a base polymer, preblending with tackifier resins in a sigma-blade mixer at 140–160°C should be performed under nitrogen or vacuum to limit oxidative yellowing. Fourier-transform infrared spectroscopy of pressed films is recommended for positive identification, because the pellet surface alone cannot distinguish EVA from similar ethylene ester copolymers.

Lot-to-lot variance in EVAtech EVA 150I/15A should be evaluated by melt flow rate and VA content rather than by visual appearance. A variation of ±1 wt% VA can shift heat seal and adhesion performance enough to be detected in high-speed adhesive lines. Density and hardness are secondary indicators; density is insensitive to small changes in VA content and cannot substitute for infrared or titration measurements. The pellet size distribution is likewise important for gravimetric dosing: granules finer than 2 mm may segregate in bulk railcars, while oversized pellets can cause feed-throat blockages. For incoming inspection, a retained sample should be tested under ISO 1133-1:2022 with a 190°C, 2.16 kg condition, and the melt viscosity at 100 s⁻¹ may be measured on a capillary rheometer when a processing plant requires gate-freeze data for mold-fill simulation. Published data for this specific configuration is limited; mold-fill simulation should therefore be calibrated with in-house spiral-flow experiments at the intended melt temperature.