TAFMER DF740 (Mitsui Chemicals) is a very low density ethylene-α-olefin copolymer whose reduced crystalline fraction allows it to form a discrete elastomer phase when compounded into isotactic polypropylene homopolymer.

In automotive interior injection moulding, isotactic polypropylene homopolymer shifts from brittle impact behaviour to ductile response only after dispersing DF740 at 20–30 wt% on a co-rotating twin-screw extruder with 40:1 L/D and a segmented screw configuration containing three kneading blocks downstream of the side feed. Barrel temperatures from hopper to die are typically set at 180°C / 200°C / 210°C / 215°C / 210°C because the processing window is limited by the low softening point of the VLDPE phase; melt temperature above 220°C degrades the elastomer and reduces impact retention. The compounded pellet is injection moulded at 210–230°C melt temperature, mould temperature of 30–50°C, velocity-controlled filling with switchover at 95–98% of shot volume, and hold pressure of 50–70 MPa; large door trim tools normally require clamp force between 8,000 kN and 12,000 kN. Notched Charpy impact is measured under ISO 179-1/1eA at 23°C and -30°C, tensile yield stress under ISO 527-2, and melt volume-flow rate under ISO 1133-1:2022 at 230°C / 2.16 kg. The rubber-phase domain size must fall below approximately 1.5 μm for consistent low-temperature impact, but the exact dispersion depends on screw shear rate and pellet viscosity: coarser domains produce large batch-to-batch variation in door trim ductility. Terminal components include door trim panels, lower pillar garnishes, glove box surrounds, and instrument panel soft-touch carrier parts. Interior emission compliance is verified by thermogravimetric VOC testing under VDA 278, fogging under ISO 6452, and flame spread under FMVSS 302. The operational boundary is stiffness loss: glass-fibre-reinforced PP should not exceed 10 wt% DF740 addition because the flexural modulus and heat deflection temperature fall beyond acceptable limits for structural inserts, whereas unfilled opaque trim tolerates higher loading. Surface moisture from storage above 60% RH can cause feed-throat slip in the compounding extruder because the skin of the pellet adsorbs ambient water even though the polyolefin matrix is not hygroscopic; pre-drying is not required if closed silo storage remains below that value.

When Is a VLDPE Sealant Layer Preferred over Standard LLDPE in Three-Layer Blown Film?

Three-layer blown film lines produce a DF740 sealant layer when the converter requires a lower heat-seal initiation temperature than a conventional C4-LLDPE and reduced gel-related bubble instability during long runs. The layer ratio is typically 20 wt% / 60 wt% / 20 wt% or 15 wt% / 70 wt% / 15 wt% in an A/B/A structure, with the external layers based on a C6-LLDPE or metallocene LLDPE and the core layer containing DF740 blended with up to 40 wt% mLLDPE for stiffness and gauge control. The film is processed on a grooved-feed extruder with 30:1 L/D barrier screw, a die gap of 2.0–2.4 mm, and a blow-up ratio between 2.0:1 and 2.6:1. The frost line is maintained at 380–450 mm above the die face because the lower melt strength of the DF740 phase narrows the high-stalk bubble stability window relative to standard LLDPE. Adapter melt temperature is held at 180–210°C, which is sufficient for layer homogenization but low enough to avoid oxidative gel formation at the die lip. Heat seal performance is evaluated under ASTM F88/F88M at sealing temperatures from 95°C to 130°C with dwell times of 0.5 s and 1.0 s; the VLDPE layer lowers the seal initiation temperature relative to C4-LLDPE, permitting faster indexing on vertical form-fill-seal machines for frozen vegetable and liquid detergent pouches. The sealant layer satisfies US food-contact conditions under 21 CFR 177.1520 for olefin polymers and EU requirements under Regulation (EU) No 10/2011, Annex I, with overall migration tested by EN 1186-1 under OM2 aqueous and acidic simulants. The material is not an aroma or oxygen barrier; fatty food structures require an EVOH or polyamide layer plus tie resins, and retort sterilization above 110°C is outside the operating window because the low-density phase softens and deforms under sustained autoclave pressure.

A thermally sensitive masterbatch carrier based on TAFMER DF740 is produced by dispersing 40–60 wt% organic pigments and processing aids in a 32:1 L/D twin-screw extruder with main-throat feeding and a second feed port at 16 D downstream. The low crystalline melting range of the VLDPE carrier allows melt discharge at 150–170°C, which reduces thermal degradation of yellow and red organic pigments compared with LDPE carriers that require processing above 190°C. The finished masterbatch is let down at 2–5 wt% in polyethylene bottle caps and injection-moulded polypropylene closures, where the carrier does not shift the base resin melt flow rate beyond the converter’s tolerance under ISO 1133-1:2022.

If Halogen-Free Flame Retardant Jacketing Requires High Filler Loading

When a halogen-free flame retardant wire and cable jacket uses TAFMER DF740 as a low-modulus base resin or as a modifier for linear polyethylene, the dominant process control variable is the dehydration point of aluminum trihydrate. The compound is mixed with 150–180 phr of precipitated ATH or a mixed ATH/MDH filler system; this solids loading raises melt viscosity and adiabatic temperature rise, so a co-kneader or intermeshing twin-screw extruder with 36:1 L/D is operated with reverse-conveying elements only after the final filler feed. Barrel temperatures are set in a descending profile, for example 160°C / 165°C / 160°C / 155°C / 150°C, while the melt temperature at the die is kept below 170°C to prevent steam porosity from ATH dehydration. A 40-mesh breaker plate is placed before the straining die to remove filler agglomerates, and strand die pressure is monitored because a rise above 8 MPa signals filtration blockage and requires screen-pack change. Jacketing is applied to insulated conductors by tube-on or semi-pressure extrusion with a crosshead temperature of 150°C and screw speed limited to 60–80% of maximum to avoid viscous heating. The finished cable is tested for tensile strength and elongation before and after oven aging under IEC 60811-501, low-temperature bending at -40°C under IEC 60811-504, and vertical flame propagation under IEC 60332-1-2 or UL 1581 for appliance wire styles. Terminal products include internal wiring for household appliances, signal cables, and battery harness jackets where RoHS compliance under EU 2011/65/EU is mandatory. A known incompatibility is the combination with amine-containing flame retardants and certain chlorinated additives that can accelerate polyolefin degradation during long extrusion runs; zinc stearate lubricant above 0.5 wt% should also be avoided because it may reduce ATH decomposition temperature and generate surface bloom. Specific limiting oxygen index values for DF740-based HFFR formulations are not available in public supplier documentation, so flame performance must be confirmed on the finished cable assembly rather than predicted from resin datasheet data.

Extrusion Coating and Laminating Adhesion to Aluminum Foil

Extrusion coating of TAFMER DF740 onto aluminium foil is run on a coextrusion coating line with a 30:1 L/D extruder and a flat die gap of 0.6–0.8 mm. The air gap between die exit and nip is set to 150–200 mm; shorter gaps reduce neck-in but also reduce oxidation time, while longer gaps improve adhesion to porous paperboard but increase edge instability. Melt temperature at the die is controlled between 260°C and 290°C, lower than conventional LDPE coating temperatures because prolonged residence at higher temperature generates gel lenses in the thin web. Coating weight is controlled from 15 g/m² to 25 g/m² for lamination of paperboard and polyethylene terephthalate film; adhesion is measured under ASTM F904 after conditioning at 23°C / 50% RH. When foil adhesion is required, a tie layer of anhydride-modified polyethylene is coextruded at 5–10 g/m² because unmodified DF740 does not chemically bond to aluminium oxide, and the structure fails at the foil interface during peel. Terminal structures include aseptic carton lamination, insulation facing, and sachet lamination for dry beverage powders. Edge neck-in is monitored with an optical width gauge; DF740 typically shows higher neck-in than LDPE at equivalent melt temperature and line speed, so die edge bead settings are adjusted manually at the start of each production order. Pinholing is detected by optical inspection or ASTM E154, and moisture vapour transmission through the coated film is measured under ASTM F1249 at 38°C / 90% RH.

Thermal Decomposition of Azodicarbonamide Governs Cell Morphology in DF740-Modified Foam

In low-density polyolefin foam sheet, TAFMER DF740 is added at 10–30 wt% to an LDPE or mLLDPE base to reduce gel fraction sensitivity and soften the cell walls without destabilizing the blowing process. A tandem extruder configuration uses a primary screw with 32:1 L/D for compounding and a secondary cooling extruder with 24:1 L/D to bring the melt temperature down to 105–115°C before the annular die. Azodicarbonamide is fed at 0.5–1.5 wt% with a decomposition peak between 195°C and 220°C, above the crystalline melt range of the VLDPE, so the primary extruder must be zoned to fully decompose the blowing agent before the cooling stage. Published data for DF740 in azodicarbonamide foam is limited, so the exact cell density and compression set must be established by pilot runs; the process is sensitive to melt strength variation at the die lip because premature nucleation produces collapsed cells and high scrap rates. Terminal products include cushioning sheets, pipe insulation, and gasket profiles, where compression set is measured under ISO 1856 and water-vapour transmission under ASTM D2842 depending on closed-cell content.