ELVAX PV1300Z Ethylene Vinyl Acetate Copolymer

ELVAX PV1300Z is processed as the base polymer in peroxide-curable photovoltaic encapsulant films. The grade carries a nominal vinyl acetate content of 28 wt% and a nominal melt flow rate of 25 g/10 min when measured in accordance with ASTM D1238-20 at 190 °C and 2.16 kg. Vinyl acetate comonomer in this range depresses the crystalline melting point to approximately 70 °C and increases amorphous-phase transparency relative to lower-VA copolymers. In a module encapsulant, the resin is dry-blended with a peroxide initiator, a silane coupling agent, a hindered amine light stabilizer, and a phosphite antioxidant. The peroxide is commonly an OO-tert-butyl-O-(2-ethylhexyl) monoperoxycarbonate with a 1 h half-life temperature in the range of 116–118 °C. The formulated compound is extruded into a monolayer film, typically between 0.4 mm and 0.6 mm thickness, through a flat die. The extrusion line uses a single-screw extruder with an L/D ratio of 24:1 to 30:1 and a barrel temperature profile kept below 100 °C. The die zone is controlled at 90–110 °C. At these temperatures, peroxide decomposition is minimized, and premature crosslinking in the extruder is avoided. The melt exits the die and is drawn through polished chill rolls that set surface finish and thickness profile. The film is then wound with a release liner or embossed interleaf. During module lamination, the film is placed between the glass frontsheet and the cell string, with a second layer between the cell string and the backsheet. The stack is heated in a vacuum laminator. Lamination temperature is typically raised to 145–150 °C and held for 12–20 min. The peroxide decomposes, generating free radicals that abstract hydrogen from the EVA backbone and form covalent crosslinks. The result is a thermoset encapsulant with a gel content above 70% when measured by solvent extraction in xylene or toluene according to ASTM D2765-16. The silane coupling agent reacts with glass and cell surfaces to improve interfacial adhesion. The encapsulant must maintain adhesion to glass, backsheet films, solder-coated copper ribbons, and busbars. The processing window is narrow. A lamination temperature below 140 °C leaves unreacted peroxide and low gel content. A temperature above 160 °C can cause bubble evolution from decomposition by-products, particularly in thick stacks. The viscosity of the molten EVA during lamination is low enough to fill gaps around 5-busbar or 6-busbar cell metallization. The same low viscosity can create flash or edge bleed if platen pressure is ramped too quickly. Published data for this specific formulation configuration is limited, but module makers commonly specify gel content of 70–90%, glass adhesion of 50–120 N/cm, and light transmittance of at least 90% in the 380–1100 nm range. The cured encapsulant is tested as part of the module according to IEC 61215-1:2021 and IEC 61730-1:2016. The encapsulant film itself is not the sole determinant of module certification. The EVA electrical insulation contribution is reflected in wet leakage current testing and dry insulation resistance testing on the module. Volume resistivity of a well-crosslinked EVA encapsulant is typically above 1 × 10¹⁴ Ω·cm when conditioned at 23 °C and 50% relative humidity. Moisture ingress into the polymer is higher than that of ionomer or polyolefin encapsulants, and this is an operational boundary. The film must be stored sealed with desiccant in a moisture-barrier pouch. Ambient exposure above 60% relative humidity leads to moisture absorption that can create voids during lamination unless the film is pre-dried at 55–65 °C for 6–8 h.

What Conditions Extend Open Time in Low-Melt Packaging Adhesives Based on 28% Vinyl Acetate Copolymer?

Hot-melt adhesive compounding with ELVAX PV1300Z relies on the balance between crystalline ethylene sequences and amorphous vinyl acetate sequences. The 28 wt% vinyl acetate content raises adhesive tack and low-temperature flexibility compared with 18 wt% copolymers, while the 25 g/10 min melt flow rate permits wet-out at relatively low application temperatures. Typical adhesive formulations are prepared in a heated sigma-blade mixer or a heated vessel with a high-shear rotor-stator mixer. The base resin is combined with a tackifying resin, such as a hydrogenated rosin ester or a C5 aliphatic resin, at 150–170 °C. Tackifier level is normally between 30 wt% and 50 wt% of the total formulation. A Fischer-Tropsch wax or a paraffin wax is added at 5–15 wt% to reduce melt viscosity and control set speed. An antioxidant such as Irganox 1010 is added at 0.1–0.5 wt% to suppress thermal degradation during melt holding. The adhesive is applied at 120–160 °C. Open time is controlled by the rate of EVA crystallization after adhesive application. In corrugated board bonding, the fast crystallization from a 28% VA EVA gives a set time of 1–3 s when the adhesive is applied at 140 °C to a 20–30 µm coating weight. The same formulation with an 18% VA EVA would set faster, while a 33% VA EVA would remain tacky longer. The 28% VA balance allows compression of spring-back in folded carton stock without blocking on the guide rails of the packaging line. The formulation can be used in slot-coating, bead application, and spiral-wound tube lamination. Bond strength measured by T-peel according to ASTM D1876-08 on polyolefin film laminates is typically in the range of 30–100 N/25 mm, depending on substrate and tackifier. The polymer is incompatible with low-density polyethylene in a molten blend above 30 wt% addition due to phase separation. This causes surface haze and inconsistent adhesion. The blend can be stabilized with a styrene-ethylene-butylene-styrene block copolymer at 5–10 wt% to improve cohesive strength. Isocyanate moisture-cure hot melts are not generally formulated with EVA because the secondary hydroxyl content is low and vinyl acetate groups hydrolyse under accelerated aging conditions. For polyamide film adhesion applications, corona treatment of the substrate above 40 dyn/cm is required before adhesive application. The adhesive bond must be evaluated according to ASTM D1876-08 or ASTM D903-98 because the cohesive failure mode shifts with coating weight. At coating weights below 15 g/m², adhesive failure at the substrate interface is dominant. At coating weights above 40 g/m², cohesive failure within the EVA-tackifier phase is observed. This transition is a critical threshold for packaging converters because it defines the minimum film weight for durable bond formation.

Substitution of PE-wax carriers with ELVAX PV1300Z in colour masterbatch and additive concentrates changes the dispersion mechanism in twin-screw compounding. The copolymer has a melt flow rate of 25 g/10 min and a vinyl acetate content of 28 wt%, placing its processing viscosity between that of a high-flow LDPE carrier and a 33% VA EVA. In a co-rotating twin-screw extruder with an L/D ratio of 40:1, the carrier is fed as the continuous phase at 15–25 wt% of the masterbatch. Organic pigments such as phthalocyanine blue are added at 40–60 wt%, with low-molecular-weight polyethylene wax at 5–10 wt% to reduce surface energy. The vinyl acetate dipole improves pigment wetting and lowers the tendency of pigment agglomerates to reform after dispersion. This results in lower filter pressure values after a 400-mesh screen-pack. The specific energy input required to achieve a Hegman grind of 7+ is often 0.12–0.18 kWh/kg, compared with 0.18–0.25 kWh/kg when a PE-wax carrier is used. The masterbatch is used by the processor at a let-down ratio of 3–6 wt% in polyolefin film or injection moulding. The high VA content of the carrier increases the risk of plate-out on injection mould vents and extrusion die lips when the concentrate is used at high temperature above 230 °C. Acetaldehyde and acetic acid release from the carrier during prolonged residence time can attack polycarbonate when the masterbatch is used in polycarbonate compounding. Therefore, the carrier is not recommended for polycarbonate or polyoxymethylene applications. The masterbatch carrier is compatible with LDPE, LLDPE, EVA, and ethylene-butyl acrylate. It is not compatible with polypropylene at addition levels above 10% because of phase separation and formation of surface delamination. The concentrate should be dried at 60–70 °C for 4 h before processing if stored in high-humidity conditions. Residual moisture content should be below 0.05 wt% to prevent hydrolysis in the extruder. The carrier can be used in cable compound colour masterbatches. In such applications, the same VA content avoids interference with silane-grafted EVA and ethylene-octene copolymers used in jacket compounds.

When Azodicarbonamide Decomposition Overlaps the EVA Crystallization Plateau

Expanded EVA footwear soles are produced by mixing ELVAX PV1300Z with chemical blowing agents, crosslinking agents, and fillers in a closed internal mixer. The compound is then milled into sheets, cut into preforms, and heat-pressed in a mould. The polymer 28 wt% vinyl acetate content lowers crystallinity and permits a large expansion window before the melt tears during gas expansion. The melt flow rate of 25 g/10 min allows the compound to fill complex midsole mould cavities. Azodicarbonamide is typically added at 2.5–5.0 phr. Its decomposition exotherm begins at approximately 190–200 °C, while the EVA crystallization plateau during cooling starts near 55–65 °C. Expansion must be completed before the cooling phase drops the compound below the melting range. If mould pressure is released before the crystallization front is established, cell walls rupture and the sole shows internal splits. Dicumyl peroxide is used as the crosslinking agent at 0.6–1.2 phr. The peroxide cure must generate enough melt strength to prevent gas bubble coalescence, but not crosslink the EVA too early and restrict expansion. Typical mould temperature is 160–175 °C for 6–10 min, depending on sole thickness. The compounding step must avoid reaching 120 °C in the internal mixer for more than 3 min, because dicumyl peroxide begins to undergo significant decomposition. Batch-to-batch variation in EVA viscosity is a known source of moulding inconsistency. The 25 g/10 min melt flow rate must be verified for each lot, because a shift of ±2 g/10 min changes preform flow length in the mould and final sole density. Density of the expanded sole is usually specified between 0.18 g/cm³ and 0.25 g/cm³ for lightweight running footwear. The cured sole is tested for hardness with ASTM D2240, tensile strength with ASTM D412, and rebound resilience with ISO 4662. The EVA foam has a typical Shore A hardness of 50–65. A higher VA content would reduce hardness and increase resilience, while a lower VA content would increase hardness but reduce low-temperature flexibility. The presence of vinyl acetate comonomer improves adhesion of solventborne or waterborne polyurethane coatings used on sole sidewalls. Without corona or primer treatment, the unfoamed EVA surface has a surface energy of approximately 31–34 mN/m, which is below the 40 mN/m threshold for reliable bonding with many waterborne adhesives. Corona treatment above 44 dyn/cm is recommended prior to sidewall cementing. The foam is not suitable for direct contact with PVC compounds during storage because plasticiser migration from PVC can soften the EVA surface and reduce coating adhesion.

Halogen-Free Flame Retardant Jacketing and Silane-Grafted Moisture-Cure Compounds

ELVAX PV1300Z functions as a base resin or modifier in halogen-free flame retardant cable jackets. The 28 wt% vinyl acetate content enhances filler loading capacity for aluminium trihydroxide and magnesium dihydroxide. A typical low-smoke zero-halogen jacketing compound contains 40–60 wt% filler. The EVA phase is compounded in a twin-screw extruder with a low-shear screw configuration to avoid premature release of water from the hydrated mineral filler. Barrel temperature is kept between 120 °C and 160 °C, because filler begins to decompose above 180 °C. Melt temperature at the die is maintained below 170 °C. The EVA amorphous domains provide flexibility needed for cable jacket installation at low temperatures. The compound is tested for tensile strength and elongation at break according to IEC 60811-501 or ASTM D638. Limiting oxygen index is measured according to ISO 4589-2. Typical values for the compound are in the range of 28–36%, depending on filler level and addition of a char-forming agent. Cone calorimeter testing according to ISO 5660-1 provides peak heat release rate data. The EVA carrier alone does not provide flame retardancy. The filler network is responsible for endothermic decomposition and water release that dilutes the fuel supply. A high melt flow resin improves filler wetting but can reduce mechanical strength. The 25 g/10 min melt flow rate is therefore balanced with a higher molecular weight EVA or ethylene-octene copolymer to achieve cable jacket tensile strength above 10 MPa. The silane-grafted moisture-cure system is an alternative for low-voltage insulation. The EVA is grafted with vinyl trimethoxysilane in the presence of a peroxide initiator. The grafted polymer is then blended with a tin catalyst masterbatch and extruded onto the conductor. Crosslinking occurs after extrusion through moisture exposure in a water bath at 80–90 °C for 6–12 h. The cured insulation is tested for hot-set elongation under 0.2 MPa load according to IEC 60811-507. An acceptable hot-set value is typically below 100% after 15 min at 200 °C. The EVA resin must be stored dry because methoxy silane groups are moisture-sensitive after grafting. The compound should not be processed on equipment also used for peroxide-curable PE without a thorough purge, because residual peroxide and silane can interact to form gel specks. Die build-up from vinyl acetate decomposition begins to appear when melt temperature exceeds 200 °C for more than 20 min. This operational boundary is observed in production-scale extrusion as a gradual increase in die pressure and appearance of brown specks in the jacket. The compound can be coloured with polar masterbatches but should not be blended with amine-based flame retardants, because vinyl acetate groups can undergo ester-amide exchange under high-temperature processing.

ELVAX PV1300Z is used as a compounding modifier in impact modification and adhesion-promoting layers. In bonded aluminium-polyolefin composite panels, a film of the copolymer is laminated between the aluminium coil and a polyethylene outer layer. The copolymer film acts as a tie layer with peel adhesion to aluminium above 40 N/25 mm after corona treatment of the aluminium coil. The film is extruded at 120–150 °C through a T-die and cooled on a matte chill roll to maintain surface roughness. Surface roughness ensures that air is not trapped during the lamination step. The roll stack is laminated at 160–180 °C under nip pressure. The resulting composite is used in wall cladding and ceiling panels. The EVA tie layer provides moisture resistance and low-temperature peel strength. However, adhesion to untreated aluminium decays after 1000 h of salt spray exposure according to ISO 9227. The aluminium coil must be chromate-free passivated and primed to maintain durability. In profile extrusion, the resin is blended with an ionomer or polyolefin elastomer to produce anti-slip profiles and edge protection strips. The addition of 15–25 wt% of the EVA to a high-density polyethylene profile lowers the flexural modulus and improves coefficient of friction. Abrasion resistance is measured by the Taber test according to ASTM D4060. The wear index increases when EVA content exceeds 30 wt%, and the profile shows surface tack. The compound is not suitable for continuous service above 70 °C because the EVA phase softens and the profile loses dimensional stability. Heat deflection temperature of the blend drops from 75 °C for unmodified HDPE to approximately 55 °C at 25 wt% EVA. This limitation must be specified in the technical data sheet for building and construction profiles.