| HS Code | 464990 |
| Product Name | Sinopec PP Terpolymer ZHP7540 (PPT-FV08-G) |
| Material Type | Polypropylene terpolymer (random, high clarity) |
| Melt Flow Rate | 7.5 g/10 min (230°C, 2.16 kg) |
| Density | 0.90 g/cm3 |
| Tensile Strength At Yield | 28 MPa |
| Elongation At Yield | 12% |
| Flexural Modulus | 1100 MPa |
| Notched Izod Impact 23 C | 55 J/m |
| Heat Deflection Temperature 0 45 Mpa | 85°C |
| Vicat Softening Temperature | 130°C |
| Haze 1 Mm Plaque | 10% |
| Melting Temperature | 145°C |
As an accredited Sinopec PP Terpolymer ZHP7540 (PPT-FV08-G) factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Sinopec PP Terpolymer ZHP7540 (PPT-FV08-G) supplied in 25 kg woven bags, palletized and wrapped for safe handling and storage. |
| Container Loading (20′ FCL) | 20′ FCL: 25kg bags of Sinopec PP Terpolymer ZHP7540, palletized, approx. 20 metric tons per container. |
| Shipping | Sinopec PP Terpolymer ZHP7540 (PPT-FV08-G) ships as non-hazardous polypropylene resin in 25kg bags or jumbo sacks. Store dry, avoid direct sunlight, and protect from moisture. Ensure clean, dry transport surfaces. Keep away from heat sources and follow standard material handling practices. |
| Storage | Store in a cool, dry, well-ventilated area away from direct sunlight, heat, and ignition sources. Keep containers sealed and protected from moisture and mechanical damage. Avoid stacking excessively high to prevent deformation. Maintain moderate temperatures, typically below 40°C, and use within one year to preserve product quality. |
| Shelf Life | Store in a cool, dry area, away from sunlight and moisture; shelf life is typically 12 months from delivery. |
In biaxially oriented polypropylene (BOPP) coextrusions, ZHP7540 (PPT-FV08-G) is evaluated as a low-seal-initiation skin layer over a high-melting homopolymer or random copolymer core. The skin is applied at 0.8–2.5 µm after biaxial orientation, which corresponds to 5–12 wt% of the finished film depending on total gauge. A representative formulation for the skin layer is 100 parts terpolymer, 0.08–0.15 phr synthetic silica antiblock, and 0.05–0.10 phr erucamide slip. The slip and antiblock loadings are constrained by the need to maintain heat-seal strength: silica above 0.20 phr can reduce seal strength through barrier-to-fusion at the seal interface, while erucamide above 0.12 phr lowers coefficient of friction but may bloom and reduce print adhesion on corona-treated surfaces. Published multi-plant data for this specific grade is limited; the processing boundaries below are class data for propylene–ethylene–butene terpolymer sealant webs and require verification against the Sinopec certificate of analysis.
On a sequential BOPP line, the coextruded sheet is quenched on a cast roll at 18–30°C, reheated to 110–140°C for machine-direction stretching, then transverse-stretched at 145–170°C. Machine-direction stretch ratios of 4.5–5.5 and transverse ratios of 8.0–10.0 are typical. The key conflict in this application is between seal initiation temperature and blocking resistance in the transverse-direction oven. Terpolymer comonomer incorporation lowers the onset of molecular diffusion at the seal interface; if the seal initiation temperature is depressed below approximately 95°C, the skin can become tacky during annealing at 120–150°C, causing blocking on steel rollers and wrinkling at the tenter clips. Operators maintain the annealing-zone temperature at least 25°C below the film blocking point measured by a gradient bar blocking test. When blocking force measured by ASTM D3354-21 exceeds 30 g/cm, the skin formulation must be adjusted by reducing comonomer content or increasing antiblock within the silica loading window. This is a critical processing threshold, not a general guideline. The sealant layer should not be coextruded with ethylene-vinyl acetate or acid-modified ethylene copolymers; acid functionalities and viscosity mismatch produce interfacial instability and gel-like specks. Pre-drying is normally unnecessary, but if stored in high-humidity conditions and exposed to a temperature swing, surface condensation must be removed by drying at 60°C for 2 h. Terminal articles from this structure include printed overwrap for confectionery, bakery, fresh produce, and carton packaging.
Table 1 summarizes class-typical values for propylene–ethylene–butene terpolymer sealant webs; ZHP7540-specific values must be confirmed on the production line and by the certificate of analysis.
| Property | Test method | Class-typical range |
|---|---|---|
| Seal initiation temperature | ASTM F88/F88M-21 | 95–115 °C |
| Hot-tack onset | ASTM F1921-18 | 98–120 °C |
| Haze | ASTM D1003-13 | 1.5–3.5 % |
| Kinetic coefficient of friction | ASTM D1894-14 | 0.20–0.45 |
| Tensile strength MD/TD | ISO 527-3:2018 | 25–45/20–35 MPa |
| Elmendorf tear MD/TD | ASTM D1922-15 | 0.5–2.5/3.0–8.0 N |
The limiting factor in high-speed cast polypropylene (CPP) sealant webs is chill-roll heat-transfer uniformity and the melt curtain’s neck-in behaviour. ZHP7540 is processed as a monolayer sealant web at 20–50 µm or as the seal layer in a two-layer or three-layer cast coextrusion at 8–15 % of total thickness. In a three-layer A/B/A structure, the outer sealant layers are ZHP7540 and the core is a polypropylene homopolymer or random copolymer with lower melt flow rate to stabilize the melt curtain. The ratio of inner core to sealant skin is typically 80/20 or 85/15 by mass; increasing the sealant layer fraction above 25 % lowers melt tension and increases neck-in above 50 mm at an air gap of 30–80 mm. Extruder barrel profiles for the sealant layer are set at 210°C, 225°C, 235°C, 240°C and the die at 240°C; melt pressure at the screen changer is maintained below 350 bar to avoid shear-induced comonomer degradation. The cast roll temperature is controlled between 10°C and 20°C with a water circulation system capable of ±1°C variation. Chill-roll temperature above 25°C lowers quench rate and produces large spherulitic structures that increase haze above 4 % measured by ASTM D1003-13; temperature below 8°C can create surface condensation and moisture-related slip-agent migration defects. The melt curtain is pinned with an air knife at 0.5–1.5 bar. Terminal articles include printed lamination film for snack foods, noodle packaging, and textile bags; the sealant web is typically laminated to BOPP or PET with solventless adhesive before forming on horizontal or vertical form-fill-seal machines. Hot-tack strength measured by ASTM F1921-18 should remain above 2.0 N/25 mm across the sealing jaw temperature range of 95°C to 125°C to avoid seal failure during product drop on vertical baggers.
Extrusion lamination coating with ZHP7540 is technically feasible on lines equipped with a 90–120 mm single-screw extruder with L/D 30:1 and barrier screw. The polymer is applied at 10–20 g/m² as a melt adhesive between a printed polyester film and a heat-sealable polypropylene or polyethylene inner web. The melt temperature at the die is 260–285°C; lower temperatures do not produce adequate draw-down to thin coating weight, whereas above 295°C the low-melting terpolymer forms gel particles and generates odorous low-molecular-weight fractions. The air gap between die exit and nip is held at 100–250 mm; shorter air gaps reduce neck-in but increase substrate heat load, particularly on 12 µm metallized PET where heat shrinkage measured by ASTM D1204-14 should not exceed 0.5 % in machine direction. Adhesion to aluminium foil is controlled by ozone treatment at 2.0–4.0 g/h or by priming the foil with an imine primer. Without surface activation, peel strength measured by ASTM D1876-08 may fall below 1.0 N/15 mm; with ozone and optimized back-side cooling, peel strength in class trials reaches 2.5–5.0 N/15 mm. The extrusion lamination line speed is typically 150–300 m/min. The end laminate structure, such as printed PET/terpolymer/LDPE or printed PET/terpolymer/cast PP, is used for retort-free flexible packaging, sachet stock, and pharmaceutical strip packaging where seal integrity below 130°C is required. Published data for this specific grade in extrusion lamination is limited; the peel-strength range above is a class expectation for propylene terpolymer coatings.
For collation shrink and light overwrap structures, a three-layer blown-film line processes ZHP7540 as the inner heat-seal layer at 8–15 µm in a total film thickness of 40–80 µm. The core is a linear low-density polyethylene or polypropylene homopolymer with sufficient melt strength to stabilize the bubble; the outer layer is a blend of low-density polyethylene and polypropylene to balance shrink force and surface slip. Blow-up ratio is maintained at 2.0–3.0, die gap at 1.2–2.0 mm, and frost line height at 4–8 die diameters. Melt temperature for the ZHP7540 layer is 220–250°C; melt temperature above 260°C causes bubble instability and creates airborne wax-like fumes from additive degradation. The sealant layer is corona-treated on the inner surface only; treatment above 40 mN/m can increase blocking and reduce heat-seal strength due to surface oxidation. Terminal products include multipack bottle collation shrink film, box overwrap, and stationery packing film. In high-speed sleeve-wrapping lines using hot-air shrink tunnels at 120–150°C, the seal layer must not delaminate from the core; interlayer adhesion above 1.5 N/15 mm by ASTM D1876-08 is required. The process boundary is set by the difference between the seal initiation temperature and the shrink-tunnel temperature: the seal layer must remain dimensionally stable during hot-air exposure while still sealing at 95–115°C on the sealing jaw. This is a narrow window that requires strict frost line and bubble cooling control.
Coextruded polypropylene sheet for thermoformed cups uses ZHP7540 as a thin sealant layer on a PP homopolymer or random copolymer base. The sheet gauge varies from 0.8–1.5 mm, with the sealant layer occupying 10–20 % of total thickness. Sheet extrusion is performed on a flat-die line with a die gap of 1.5–2.5 mm, melt temperature 230–255°C, and three-roll polishing stack temperatures of 20°C, 45°C, and 70°C. The sealant layer must not be polished above 80°C because the low-melting terpolymer can adhere to the second roll. Thermoforming is performed at sheet surface temperatures of 145–160°C, measured by infrared pyrometer, with plug-assisted forming into cup depths up to 1.5:1 draw ratio. During forming, the sealant layer migrates toward the rim as the plug stretches the sheet; this rim thinning to 40–60 % of original thickness creates the critical seal area for lidding film. If the layer thins below 30 % of original thickness, seal strength drops below 1.0 N/15 mm on the flange. The lidding seal is carried out at 100–125°C and 0.3–0.6 MPa jaw pressure for 0.5–1.0 s. Terminal products include dairy cups, margarine tubs, and deli containers where the sealant layer is in direct food contact under FDA 21 CFR 177.1520(c) conditions of use. Migration of slip additives from the sealant layer into the food simulant must comply with EU No 10/2011 overall migration limit of 10 mg/dm² and specific migration limits for erucamide if present above 0.1 %.
Horizontal flow wrappers running ZHP7540 sealant webs at 400–800 packages/min impose strict coefficient of friction (COF) control. In this application, the key variable is the rate of erucamide bloom to the film surface. At ambient storage below 15°C, bloom is delayed for 72–120 h; at warehouse temperatures above 30°C, bloom can be completed in 24 h. The kinetic COF measured by ASTM D1894-14 decreases from initial 0.40–0.60 to equilibrium 0.20–0.35 after bloom. If erucamide loading is too high, static COF falls below 0.15 and the film telescopes or slides on the forming shoulder, producing misregistered printed packaging. If loading is too low, static COF remains above 0.45 and the film jams in the forming tube. A representative slip masterbatch addition is 1.0–2.0 % of a 5 % erucamide concentrate, giving 500–1000 ppm active erucamide in the sealant layer. Blocking resistance is measured by ASTM D3354-21; blocking load should remain below 25 g/cm for roll stock stored at 35°C and 80 % RH for 7 days. Synthetic silica at 1500–2500 ppm controls blocking but increases haze; the formulation must balance COF, blocking, and clarity for printed film. High-speed wrapping lines require film stiffness sufficient to prevent sag between forming shoulder and sealing jaws; tensile modulus measured by ISO 527-3:2018 at 1 % secant should be above 500 MPa in machine direction for a 20 µm web. Terminal products include chocolate bar overwrap, wafer packs, and biscuit packaging. In these applications, seal jaws are typically set at 100–120°C, jaw pressure 0.2–0.5 MPa, and dwell 20–40 ms. The process window is narrow because excessive erucamide bloom can occur within 48 h of production; therefore, film is converted into packages within 3 days after slitting to avoid COF drift.
Regulatory references applicable to food-contact polypropylene sealant layers are listed in Table 2. Additive-specific migration limits must be confirmed from the supplier’s product declaration.
| Regulatory reference | Scope | Application boundary |
|---|---|---|
| FDA 21 CFR 177.1520(c) | Olefin polymers for food contact | Conditions of use A–H; hot-fill or retort use requires case-specific compliance |
| EU No 10/2011 | Plastic materials intended for food contact | Overall migration 10 mg/dm²; specific migration limits for slip and antiblock additives |
| REACH Regulation (EC) No 1907/2006 | SVHC concentration 0.1 % w/w | Applies to base polymer and masterbatch components |
| RoHS Directive 2011/65/EU | Restricted heavy metals and brominated flame retardants | Not expected in non-flame-retardant polypropylene; verify with XRF screening |
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Sinopec PP Terpolymer ZHP7540 (PPT-FV08-G) is a propylene-based terpolymer resin supplied in pellet form for film conversion, specifically for cast and oriented polypropylene sealant layers where a low heat-seal initiation temperature and a broad sealing window are required. The resin contains ethylene and a higher α-olefin comonomer randomly distributed along the propylene chain; this comonomer distribution suppresses crystallinity, shifts the melting endotherm downward, and reduces tensile modulus relative to propylene homopolymer. Open-source English-language datasheet values for this exact grade are limited, and the figures discussed below represent class-typical data for propylene terpolymer film grades unless a specific test method is cited. Lot-specific values for melt mass-flow rate, comonomer content, thermal transitions, and mechanical properties should be obtained from the Sinopec technical datasheet or the certificate of analysis for each delivery.
A propylene terpolymer differs from a propylene-ethylene random copolymer by the presence of an additional comonomer, frequently 1-butene, which disrupts stereoregularity and reduces lamellar thickness. The consequence is a melting peak temperature typically between 125 °C and 140 °C measured by differential scanning calorimetry according to ISO 11357-3:2018, compared with approximately 160 °C to 165 °C for propylene homopolymer. The lower melting temperature translates into a heat-seal initiation temperature approximately 20 K to 30 K below that of a standard random copolymer. In packaging operations, this permits lower seal-bar set temperatures, reduced energy input, and higher cycle rates on vertical form-fill-seal and horizontal form-fill-seal machines.
Comonomer distribution is a critical quality attribute that is not visible in the melt mass-flow rate alone. In propylene terpolymers, the reactivity ratios of ethylene and 1-butene differ; the resulting chain has compositional heterogeneity that can be characterized by temperature-rising elution fractionation or crystallization analysis fractionation. A broad chemical composition distribution can broaden the sealing window but may reduce hot-tack strength and optical clarity if high-molecular-weight, low-comonomer fractions persist. Nuclear magnetic resonance spectroscopy, specifically 13C NMR, is used to determine total comonomer content and sequence distribution. No public data for these molecular parameters are available for ZHP7540.
| Property | Test method | PP homopolymer | PP random copolymer | PP terpolymer film grade |
|---|---|---|---|---|
| Melt mass-flow rate | ISO 1133-1:2022 (230 °C, 2.16 kg) | 1.5–3.5 g/10 min | 5–10 g/10 min | 5–10 g/10 min |
| Tensile modulus | ISO 527-2:2012 | 1100–1550 MPa | 700–1000 MPa | 500–850 MPa |
| Tensile yield stress | ISO 527-2:2012 | 30–38 MPa | 22–29 MPa | 16–24 MPa |
| Melting peak | ISO 11357-3:2018 | 160–165 °C | 140–150 °C | 125–140 °C |
| Vicat softening temperature A50 | ISO 306:2022 | 150–155 °C | 120–135 °C | 100–120 °C |
| Heat-seal initiation temperature | ASTM F1921-20 or internal method | >135 °C | 115–125 °C | 100–115 °C |
| Haze | ASTM D1003-21 | 1.0–3.0% | 0.8–2.0% | 0.5–1.5% |
For ZHP7540 specifically, the manufacturer’s product code convention does not publicly map to a single melt-flow value; converters should not infer an MFR from the ZHP7540 designation alone. Similar Sinopec film grades in the PPT-FV series have been positioned for cast-film and sealant applications where the balance between low seal initiation temperature and melt strength governs layer stability. The ratio of ethylene to butene comonomer, the total comonomer content, and the reactor sequence all influence the final melting range and seal performance, and these variables are not visible in the grade designation.
Melt mass-flow rate is the first control point for terpolymer conversion and is determined at 230 °C under a 2.16 kg load according to ISO 1133-1:2022 or ASTM D1238-20. For cast-film sealant layers, the MFR commonly falls between 5 g/10 min and 10 g/10 min; higher MFR improves drawdown but may reduce melt strength and edge stability. For biaxially oriented film, a lower MFR may be preferred to sustain stretching forces during tenter-frame orientation. The thermal profile should be set to maintain a melt temperature between 220 °C and 250 °C at the die; temperatures above 260 °C should be avoided because the reduced thermal stability window of comonomer-rich polypropylene can lead to chain scission, gel formation, and volatile generation.
Crystallization kinetics are slower than homopolymer; the crystallization half-time at a given supercooling is longer, and the crystallinity developed on a chill roll is lower. This affects roll release: a chill-roll temperature of 18 °C to 25 °C is commonly sufficient to prevent blocking, but condensate management is necessary when the ambient dew point exceeds 16 °C. Slip and antiblock additives are often included to maintain film-to-film separation; the exact additive package for ZHP7540 should be verified by the supplier. The melt temperature should be controlled with a flat profile across the die; excessive shear at the die lip can lower local melt viscosity and cause edge weaving.
On a cast-film line, the extruder should be equipped with a barrier screw with an L/D ratio of at least 24:1, a screen pack of 40/60/80 mesh or finer to remove agglomerates, and a flat die with internal deckles to adjust the sealant layer width. The chill roll unit should provide closed-loop temperature control with a tolerance of ± 1 °C to prevent variation in crystallinity and surface gloss. Air knife impingement velocity and angle should be set to achieve uniform quenching without surface turbulence. In BOPP production, the cast sheet is quenched on a chill roll at 20 °C to 30 °C, reheated on preheat rolls, and stretched in the machine direction using a series of differential-speed rolls at a temperature of 130 °C to 145 °C. Transverse stretching occurs in a tenter oven at 155 °C to 170 °C, and annealing is conducted at 160 °C to 170 °C to stabilize orientation.
In a three-layer or five-layer cast-film structure, a terpolymer sealant layer is typically coextruded with a homopolymer or random copolymer core. The function of the sealant layer is to form a hermetic seal at the lowest practical bar temperature without melting or distorting the core. For a cast polypropylene film, seal initiation below 105 °C can raise line speed on high-speed packaging machines but may reduce hot-tack strength. Hot-tack testing according to ASTM F1921-20 measures seal strength while the seal is still molten; a low SIT alone is not sufficient if the seal fails before solidification. Converters should evaluate seal strength at 0.5 s dwell and 0.2 N/mm² seal-bar pressure, and compare the plateau region between 110 °C and 140 °C.
The sealant layer thickness is usually 3 µm to 8 µm in oriented films and 20 µm to 50 µm in cast films. Thicker terpolymer layers improve seal integrity but reduce film stiffness and increase blocking tendency. On production lines, the reduction of crystallinity in the seal layer has been associated with higher tack at the winding station when reel tension exceeds 0.5 N/mm² and when roll surface temperature exceeds 30 °C; lower-density film can also exhibit greater susceptibility to scratching during slitting. Adjustments to winding taper, contact pressure, and slip additive level are therefore required when replacing a random copolymer sealant with a terpolymer.
Compared with metallocene linear low-density polyethylene sealants, a propylene terpolymer sealant layer offers higher temperature resistance, lower extractables, and compatibility with polypropylene recycling streams, but it generally requires a higher seal initiation temperature than EVA or metallocene LLDPE. The selection of a terpolymer over an ethylene-based sealant depends on retort or hot-fill requirements and the target recycling classification of the finished package. Batch-to-batch variation in comonomer content can shift seal initiation temperature by 3 °C to 5 °C; converters should monitor seal initiation temperature from each lot because the specification sheet alone does not capture this variation.
The grade is ordinarily stabilized with a phenolic antioxidant and a phosphite secondary antioxidant; the specific additive formulation is proprietary but must be declared in the supplier safety data sheet and food-contact statement. Polypropylene homopolymers and copolymers intended for food-contact use are covered in the United States by 21 CFR 177.1520(c), which specifies olefin polymer requirements including extractable fraction limits in n-hexane and xylene. For European Union applications, compliance is assessed under Regulation (EU) No 10/2011 with an overall migration limit of 10 mg/dm² and specific migration limits for additives. A finished article must be tested under EN 1186-1 and EN 13130-1 using the intended food simulants; resin compliance alone does not guarantee finished-article compliance.
Additive migration in polypropylene is governed by the diffusion coefficient of the additive in the amorphous phase. At room temperature, phenolic antioxidants have very low mobility, but at seal temperatures above 120 °C the amorphous fraction increases and migration to the seal surface may become measurable. Surface migration can affect seal strength and organoleptic properties; therefore the additive package for ZHP7540 should be selected for low migration in high-temperature sealing applications. For electronic packaging or durables, RoHS Directive 2011/65/EU and its delegated acts may require supplier declaration for lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE; typical polypropylene resins are not formulated with these restricted substances, but verification by XRF analysis according to IEC 62321 is the responsibility of the converter. Reach compliance under Regulation (EC) No 1907/2006 may require a substance of very high concern declaration under Article 33 if any SVHC exceeds 0.1% w/w in the supplied resin.
| Standard or regulation | Application | Assessment method | Typical requirement |
|---|---|---|---|
| 21 CFR 177.1520(c) | United States food contact | Extraction per §177.1520(d) | Maximum soluble fraction set by section |
| Regulation (EU) No 10/2011 | EU food contact | Overall migration EN 1186-1 | ≤ 10 mg/dm² |
| REACH 1907/2006 | EU market | SVHC declaration under Article 33 | No SVHC > 0.1% w/w |
| RoHS 2011/65/EU | Electrical and electronic equipment | IEC 62321 XRF screening | Pb ≤ 1000 mg/kg, Cd ≤ 100 mg/kg, Hg ≤ 1000 mg/kg |
Because propylene terpolymer resins are non-hygroscopic, pre-drying is generally not required under normal storage; however, condensation on cold pellets above 60% relative humidity can introduce surface moisture and create splay or bubbles. If pellets have been stored below 10 °C and moved to a warmer production area, a silo or hopper residence time of 2 h to 4 h is recommended to equalize temperature and prevent condensation. Processing with melt temperatures above 270 °C should be avoided for extended residence times, as comonomer-rich polypropylene is more susceptible to chain scission and volatile generation than homopolymer.
In tenter-frame biaxial orientation, a terpolymer sealant skin is coextruded over a homopolymer core; machine-direction orientation ratios are typically 4.5:1 to 5.5:1, and transverse-direction orientation ratios are typically 7:1 to 9:1. The lower crystallinity of the terpolymer can reduce the force required for stretching but also narrows the processing window for preheat roll temperatures; a preheat roll temperature of 130 °C to 145 °C is commonly used. Published data for the exact ZHP7540 grade under these conditions is limited; line trials remain necessary because seal performance and optical properties depend on the full film structure, not only the sealant resin.
For medical packaging applications, the compatibility of propylene terpolymer films with gamma irradiation, electron beam, ethylene oxide, and steam autoclaving must be established separately. Polypropylene is known to undergo chain scission under gamma irradiation; the resulting reduction in molecular weight can reduce seal strength and increase brittleness. Published data for ZHP7540 under ISO 11137 sterilization doses of 25 kGy to 50 kGy are limited; validation under the intended sterilization method and dose is required. Ethylene oxide sterilization is generally less aggressive toward polypropylene but requires aeration to remove residual gas. Steam sterilization above 121 °C may cause distortion because the Vicat softening temperature is below autoclave temperature.
Against a propylene homopolymer, the terpolymer has lower tensile modulus, lower yield stress, lower Vicat softening temperature, lower haze, and lower seal initiation temperature. Against a propylene-ethylene random copolymer, the terpolymer generally exhibits a further reduction in seal initiation temperature and a broader sealing window, although the extent depends on the total butene content. Against a metallocene LLDPE sealant, the terpolymer has higher modulus and better scratch resistance but a higher seal initiation temperature. Against a polybutene-1 blend, the terpolymer offers easier processing and lower cost but may not match the very low SIT of a polybutene-rich sealant.
On multi-layer cast-film lines, the low-crystallinity sealant skin has been observed to adhere to polished chill rolls if the roll temperature exceeds 28 °C; this is worsened by low air-knife velocity and by static charge. The failure mode appears as web flutter, edge tear, or surface haze prior to winding. Maintaining a chill-roll temperature of 20 °C to 24 °C, adjusting the air knife to a differential pressure of 0.05 MPa to 0.10 MPa, and controlling room humidity below 55% are practical corrective measures reported from film conversion lines. These operational boundaries are commonly encountered with low-crystallinity terpolymer skins and should be incorporated into start-up procedures when trialing ZHP7540.
