Dow INNATE™ TF80 is a metallocene-catalysed ethylene/1-octene linear low-density polyethylene supplied as an mLLDPE for cast-sheet tenter-frame biaxial orientation. The nominal density is 0.920 g/cm³ determined by ASTM D792, and the melt flow index is 0.85 g/10 min measured at 190°C under 2.16 kg load using ASTM D1238 or ISO 1133-1:2022. Differential scanning calorimetry according to ASTM D3418 places the peak melting endotherm at approximately 123°C. The resin is produced in a solution polymerisation unit using a constrained-geometry catalyst system, which creates a short-chain branching distribution that concentrates octene in the lower-density amorphous fraction while retaining longer ethylene sequences in the higher-molecular-weight fraction. Conventional Ziegler–Natta C4-LLDPE of similar density typically incorporates comonomer preferentially in the low-molecular-weight fraction, producing lower orientational strength, broader shear thinning, and a narrower processing window for tenter-frame stretching. The molecular architecture of TF80 therefore supports stable melt extension without LDPE blending or polypropylene addition. Table 1 summarises the primary resin characteristics used for incoming inspection and extrusion screening.

Where thermal and rheological limits define stable tenter-frame orientation

Cast-sheet extrusion of TF80 operates within relatively strict thermal boundaries because the narrow molecular weight distribution reduces shear thinning compared with conventional LLDPE. Melt temperatures should be maintained between 230°C and 250°C at the die. Below 215°C, the resin approaches the melt fracture regime and can produce sharkskin as well as transverse gauge bands; above 265°C, thermal-oxidative degradation becomes visible as gel formation and reduced seal strength after orientation. A single-screw extruder with an L/D ratio of at least 30:1 and a barrier-type screw with a mixing element is acceptable for pilot lines. Production lines commonly use L/D ratios of 33:1 to 40:1 and cavity-transfer mixing because TF80 requires additional dispersive work at high screw speeds. Die gap settings of 1.8–2.2 mm are used to limit draw resonance, and the air gap between die exit and chill roll should be controlled to 15–25 mm. Larger air gaps increase neck-in and edge bead thickness non-uniformity beyond ±2 µm at 25 µm nominal sheet thickness. Chill roll temperatures between 20°C and 30°C quench the cast sheet below the crystallisation range; chill roll temperatures above 35°C enlarge spherulite size and can raise oriented film haze above 6% as measured by ASTM D1003.

Machine-direction orientation is performed on differential-speed roller stretchers at 110–120°C, followed by transverse orientation in a tenter frame with preheat at 118–125°C, stretching at 122–128°C, and annealing at 105–115°C. The material tolerates MD stretch ratios of 4:1 to 6:1 and TD stretch ratios of 4:1 to 8:1, but the upper TD ratio requires uniform clip-chain temperature because local cold spots below 118°C generate microvoids and stress whitening. Stretching below 110°C is not recommended; the oriented crystalline network has not reached sufficient alpha-crystallite mobility, and web breaks occur on standard tenter chains. Above 130°C, the sealant surface becomes tacky and can adhere to clips, while residual free shrink at 100°C measured by ASTM D2732 after 30 s can exceed 3% if annealing is below 105°C or residence time is insufficient. The exact limits vary with die width, clip speed, and heating capacity; published data for a specific production line are limited, and commissioning should include thermal mapping across the preheat, stretching, and annealing zones.

Unlike conventional C8 mLLDPE of equivalent density, TF80 does not require LDPE modification for melt strength in cast-tenter film processes. It is common practice to add 5–20 wt% LDPE to metallocene LLDPE to improve bubble stability and tenter web strength; TF80 is designed to reduce or eliminate this addition, preserving an all-polyethylene structure that is compatible with PE flexible packaging recycling streams. Oscillatory shear rheology according to ISO 6721-10 reveals higher low-frequency storage modulus values than comparable conventional C8 mLLDPE, corresponding to longer relaxation times and improved strain hardening without the density loss that accompanies LDPE addition. The oriented film produced from TF80 differs from BOPP and BOPET in that the sealant function is intrinsic to the substrate; no additional sealant coating is required. Compared with HDPE sealant webs, the lower melting peak of 123°C reduces seal initiation temperature and avoids the embrittlement associated with high crystallinity. TF80 is intended for tenter-frame orientation use and is not recommended for high-stretch cast film lines where puncture resistance at very low thickness is the primary requirement.

What constitutes a recycle-ready sealant web in TF80-based structures?

Coextruded films pairing a TF80 sealant layer with an MDPE or HDPE core are used for form-fill-seal pouches, lamination webs, and overwrap. Seal initiation depends on film thickness, dwell time, and jaw pressure. For a 25 µm monolayer cast-tenter film, onset values typically cluster between 100°C and 110°C when measured with a heat-seal tester operating to ASTM F2029. Those values must not be transferred directly to laminates; a finished structure sealed at 120°C for 0.5 s under 0.3 MPa jaw pressure should meet a minimum heat seal strength of 8 N/25 mm by ASTM F88 for vertical form-fill-seal lines. Commercial filling lines typically operate with seal-bar temperatures between 120°C and 140°C, but dwell times below 0.3 s can produce weak seals at thick gusset folds. Because TF80 has a narrower melting distribution than Ziegler–Natta octene LLDPE, the heat-seal strength curve rises steeply after seal initiation; this creates a narrow seal window that demands precise seal-jaw temperature control but reduces stringing and improves package edge integrity.

The oriented polyethylene structure has oxygen and water-vapour transmission rates in the range expected for an uncoated PE film of 0.920 g/cm³ density. If the package requires oxygen transmission below 50 cm³/(m²·day·atm) at 23°C and 0% RH or water-vapour transmission below 5 g/(m²·day) at 38°C and 90% RH, the TF80 web must be coated or coextruded with a barrier layer. Oxygen transmission is measured by ASTM D3985 and water-vapour transmission by ASTM F1249. Structures with EVOH barrier layers above 5 wt% may not be widely accepted in PE recycling streams according to RecyClass guidelines; converters should verify the final structure against the relevant recycling protocol before making recyclability claims.

Surface treatment and additive handling for TF80-based films require attention because the standard neat resin does not contain intentionally added slip or antiblock. On high-speed packaging lines, a slip-antiblock masterbatch is metered at 2–5 wt%, with coefficient of friction controlled by ASTM D1894 to a static value below 0.30 and a kinetic value below 0.25 for horizontal form-fill-seal applications. These targets vary with sealant layer thickness and package geometry; loadings above 5 wt% can reduce optical clarity and interlayer adhesion. Corona treatment to 38–42 mN/m is required before lamination or printing; surface energy is verified by ASTM D2578. Post-corona decay is slower on tenter-oriented TF80 than on conventional LLDPE, but laminators should verify surface energy within 48 h if the film is stored under uncontrolled humidity. Moisture adsorption on pellets is not hydrolytically significant, but surface moisture above 0.1 wt% can generate steam splay in cast sheet; if regrind or silo storage shows condensation, drying at 80°C for 2–4 h with hot-air or desiccant dryers is required. Direct contact with amine-based antistatic concentrates above 0.2 wt% should be avoided because amine migration can destabilise corona-treated surfaces and reduce lamination bond strength.

Compliance matrix and regulatory citations

Regulatory compliance must be confirmed on the finished article because converting aids, inks, coatings, and masterbatches change the overall migration profile. The resin as supplied is designed to meet direct food-contact requirements for olefin polymers under FDA 21 CFR 177.1520(c), subject to the conditions of use in paragraph (b). For European Union flexible food packaging, the relevant framework is Regulation (EU) No 10/2011; the overall migration limit is 10 mg/dm² of food-contact surface area under Article 12. REACH registration under Regulation (EC) No 1907/2006 applies to the monomer and supplied resin; substances of very high concern are not expected above 0.1 wt% per Article 57 and Annex XIV. The resin is not classified as hazardous under CLP Regulation (EC) No 1272/2008 for the standard granular form, but dust from regrind can form a combustible dust cloud. Processors should follow dust explosion protection standards such as EN 1127-1 when handling fine regrind. The following matrix summarises the principal citations.