Jampilen PP Terpolymer RP128M is a propylene–ethylene–1-butene random terpolymer produced for low-temperature heat-seal layers, high-transparency cast film, and thin-wall injection-molded packaging. Melt mass-flow rate determined according to ISO 1133-1:2022 at 230°C and 2.16 kg load is 8 g/10 min; density by ISO 1183-1:2019 is 0.900–0.905 g/cm³. The terpolymer architecture places ethylene and 1-butene defects along the polypropylene chain, reducing isotactic sequence length and lowering the melting endotherm to 127–132°C by ASTM D3418-21 at 10°C/min heating rate. A propylene–ethylene random copolymer typically shows a melting peak between 140°C and 148°C under the same method, while a polypropylene homopolymer grade frequently exceeds 160°C. The lower melting point is the basis for differentiated heat-seal performance in multilayer structures. In food-contact applications the grade is intended to fall within the scope of EU 10/2011 and FDA 21 CFR 177.1520, but final compliance must be verified with the producer’s lot-specific declaration because additive package, film orientation, and conversion temperature influence overall migration and organoleptic acceptance.

How Does the Crystallization and Sealing Behavior of RP128M Compare with Random Copolymer Grades?

Under differential scanning calorimetry with indium calibration at 10°C/min, RP128M exhibits a melting peak at 127–132°C and a recrystallization exotherm onset near 92–96°C. The recrystallization exotherm shape is broad, with a half-height width of 8–12°C, which indicates a wider crystal size distribution and contributes to low-temperature seal consistency. These values are lower than those of propylene–ethylene random copolymers, which typically recrystallize at 100–110°C. The lower onset shifts heat-seal initiation downward. In laboratory seal testing per ASTM F88/F88M-21 using 50 µm cast film, 0.5 s dwell, and 0.7 N/mm² jaw pressure, a seal initiation temperature of 105–112°C is required to achieve a peel strength of 4.0 N/15 mm. At 120°C seal bar temperature, failure typically occurs by cohesive tearing of the film rather than adhesive peel, indicating that the seal strength exceeds the substrate yield strength. The practical implication is that RP128M can be used in reverse-printed multilayer structures where heat exposure must remain below the distortion temperature of ink and outer layers. Published isothermal crystallization half-time data for this specific grade are limited; producer technical support should be consulted when designing high-line-speed sealing operations above 60 m/min.

Capillary rheometry under ISO 11443:2021 at 230°C gives a shear viscosity from 200 Pa·s to 500 Pa·s over 100–1,000 s^-1, with a power-law index of 0.35–0.45. The relatively shear-thinning response permits extrusion through 0.8–1.2 mm die gaps without excessive head pressure, but it also means that viscosity recovery after die exit is slower than for a homopolymer. The melt strength is low; sagging of the web between die and chill roll becomes measurable when the air gap exceeds 12 mm and melt temperature exceeds 240°C. Therefore, a short air gap and vacuum box are specified for cast film lines. In injection molding, the same shear-thinning behavior supports filling of thin-wall parts with nominal wall thickness 0.5–1.5 mm, but hold pressure should be kept below 60 MPa to avoid flash.

On cast film extrusion lines with a single-screw extruder of 30:1 L/D and barrier screw, barrel temperatures are profiled from 180°C at the feed throat to 230°C at the die, with melt temperature maintained at 220–240°C. A flex-lip die gap of 0.8–1.2 mm, chill roll temperature of 18–25°C, and line speed of 40–90 m/min are used to stabilize the low-crystallinity web. Temperatures above 260°C produce measurable yellowing and molecular weight loss; residence times longer than 5 min at 250°C may cause gate blush and localized carbonyl formation in injection molding. A chill roll excursion of 5°C above the upper setpoint can increase unwinding force in 50 µm film by more than 30% measured by ASTM D3354-15, particularly when winding tension exceeds 0.15 N/mm. To offset blocking, 0.5–1.0 wt% silica antiblock masterbatch and 300–500 ppm erucamide slip are used; these loadings are balanced because excess antiblock raises haze above 2.0% measured by ASTM D1003-21. On injection molding machines with 80–120 t clamp force, melt temperature is set at 220–250°C with mold temperature 20–40°C. Thin-wall transparent parts are ejected with hot runner systems and low transfer pressure. Pre-drying is not normally required below 60% relative humidity; above that, 80°C for 2 h in a desiccant dryer avoids splay caused by additive moisture uptake.

Optical measurements on 50 µm cast film show haze below 2.0% and 45° gloss above 85 GU by ASTM D1003-21 and ASTM D2457-21. The low haze is retained only when film is quenched rapidly; slow cooling produces spherulitic growth and increases haze above 4.0% because the terpolymer crystallizes into larger crystal domains when the chill roll is above 30°C.

When 1-Butene Comonomer Sequences Alter Heat-Seal, Stiffness, and Organoleptic Boundaries

Relative to a propylene homopolymer with flexural modulus 1,400–1,700 MPa and haze typically above 20% in 2 mm injection-molded plaques, RP128M exhibits lower stiffness but substantially higher transparency. The presence of butene in the chain produces shorter isotactic propylene sequences and lower crystalline content, therefore the flexural modulus falls to 850–1,000 MPa by ISO 178:2019. This stiffness reduction is functionally relevant in closure applications because lower modulus can reduce torque retention if the sealing surface is not designed with adequate ribs. Compared with a standard propylene–ethylene random copolymer, the additional butene reduces the seal initiation temperature by 5–10°C and widens the heat-seal plateau between 105°C and 135°C as measured by ASTM F88/F88M-21 on 50 µm films. However, lower isotactic content also reduces thermal resistance; oxygen transmission rate may be 10–20% higher than a random copolymer at equivalent film thickness when measured by ASTM D3985-17 at 23°C and 0% RH. The grade is therefore used as a sealant layer rather than as a structural or barrier layer. Compared with metallocene ethylene-based plastomers, RP128M retains polypropylene-like surface hardness and is compatible with PP regrind streams, but its seal strength at 90°C is lower than an ethylene-based sealant because the polypropylene backbone begins to crystallize above the seal bar setpoint.

Nucleation is deliberately avoided in RP128M because high-clarity applications require fine, random crystallite sizes. If a nucleating masterbatch is added above 0.2 wt%, the crystallization temperature increases and the seal initiation temperature rises by 3–5°C, offsetting the terpolymer’s low-temperature advantage.

In coextruded cast film with an A/B/A feedblock, RP128M is used as the sealing skin at 5–8 µm thickness over a homopolymer PP core. The core layer maintains overall film stiffness and reduces the influence of the low-modulus skin on machine-direction modulus. During layer distribution, the viscosity ratio between skin and core at 230°C and 100–500 s^-1 should remain below 2:1 to prevent interfacial instability; line trials with a feedblock equipped with layer-thickness profiling are required because published data for this specific layer configuration are limited.

Regulatory Compliance Boundaries and Incompatibilities in Food-Contact Lines

The terpolymer’s low melting point imposes operational boundaries in food-contact converting. For compliance under EU 10/2011, overall migration into 3% w/v acetic acid, 20% v/v ethanol, and vegetable oil simulants is tested according to EN 1186 and must not exceed 10 mg/dm². In the U.S., the grade is intended to meet FDA 21 CFR 177.1520 for olefin polymers used in contact with food, but the producer’s declaration of compliance must confirm use limitations for hot-fill and retort conditions because terpolymer seal layers can soften at high temperature. Under REACH 1907/2006, substances of very high concern in the additive package must remain below 0.1 wt% per SVHC.

Formulation compatibility is limited by the interaction of acid scavengers and slip agents; excess metal stearates above the producer-recommended dosage can increase die lip deposit and raise haze in 50 µm film above 2.0% measured by ASTM D1003-21. The grade should not be processed at temperatures above 260°C in the presence of oxygen because the terpolymer’s lower crystallinity permits faster oxygen diffusion and higher susceptibility to chain scission. Avoid combination with amine-based additives unless explicitly approved, because amine chemistry can interfere with peroxide-based antioxidant packages and shift the melt pH in recycling streams. Storage should be below 40°C and away from direct sunlight to prevent additive bloom and oxidative yellowing.

Oxidation induction time at 210°C in oxygen, measured by ISO 11357-6:2018, should remain above 20 min for conversion stability; lower values indicate antioxidant depletion and require reducing melt temperature or increasing antioxidant masterbatch addition.