The production of cold-fill dairy packaging—yogurt cups, dessert pots, and portion packs—begins with a monolayer sheet extruded from PP 1304E5 through a single-screw extruder with an L/D ratio of
30:1 to
36:1 and a barrier screw to limit shear overheating. Melt temperature is maintained at
225 ±5 °C to avoid degradation of the slip agent while ensuring homogeneous plastication. A flat die with a lip gap of
1.8 – 2.2 mm delivers a melt curtain onto a three-roll polishing stack set at
25 °C (top),
40 °C (middle), and
20 °C (bottom), yielding a sheet thickness tolerance of
±0.02 mm.For food-contact compliance under
FDA 21 CFR 177.1520(c) condition of use A through H and
EU Regulation 10/2011 with simulant D1 (50 % ethanol) for dairy, the formulation incorporates a binary antioxidant system of
0.08 wt% Irganox 1010 and
0.08 wt% Irgafos 168, neither exceeding the SML of
300 µg/kg food. An erucamide slip additive dosed at
800 – 1 200 ppm reduces the coefficient of friction on the formed cup rim, essential for high-speed denesting in filling lines. Nucleation with
0.12 % DMDBS-based clarifier enables rapid crystallization during plug-assist thermoforming; mold cavity temperature is held at
85 – 95 °C to achieve a cycle time below
2.8 seconds.The process window is narrow: if the sheet surface temperature drops below
155 °C before forming, microcracks appear at the cup shoulder due to frozen-in orientation, whereas exceeding
168 °C causes excessive sag and wall thinning beyond
0.25 mm. Regular monitoring of the dynamic melt flow rate on the shop floor with an
ISO 1133‑1:2022 procedure is recommended; a deviation greater than
0.3 g/10 min from the nominal
4.0 g/10 min signals contamination or thermal history shift. The final yogurt cup must pass a
3.0 joule drop impact test at
4 °C without bursting—a requirement that dictates the absence of excessive mold-release additive which can initiate crack propagation.
Can High-Transparency Tumbler Production Be Achieved Without Sacrificing Cycle Time?
Manufacture of transparent drinking cups from PP 1304E5 requires a shift from a standard nucleation package to a milled sorbitol-type clarifier, typically
1 800 – 2 200 ppm of 1,3:2,4-bis(4-methylbenzylidene) sorbitol, dispersed via a
40 % talc-free masterbatch on a co-rotating twin-screw extruder with an L/D of
40:1 to achieve clarity values below
12 % haze on a
1 mm plaque per
ASTM D1003. The formulation must exclude erucamide at levels above
200 ppm because bloom accelerates with high clarifier loading, resulting in visible haze after
48 hours of storage; instead, a synthetic silica anti-block of
1 000 – 1 500 ppm is incorporated to prevent sheet sticking without optical interference.Regulatory compliance for repeated-use tumblers falls under
FDA 21 CFR 177.1520 for olefin polymers and
EU 10/2011, but the migration testing must use simulant A (10 % ethanol) for aqueous neutral food and simulant D2 (vegetable oil) if a fatty contents line is planned; total migration must remain below
10 mg/dm². During sheet extrusion, a reduced melt temperature of
210 – 220 °C is maintained to preserve the crystal lattice of the clarifier network, and the die gap is narrowed to
1.5 mm to limit post-extrusion die swell. Thermoforming utilizes a plug made of syntactic foam with a temperature of
60 °C, and the female mold is operated at
18 °C to lock in clarity, as a mold above
40 °C promotes spherulite growth and haze.A critical failure mode observed on production lines is the formation of micro-bubbles at the gate area when the melt backpressure is set below
80 bar, preventing complete wetting of the clarifier agglomerates. Moreover, the presence of any polypropylene copolymer contamination exceeding
3 % results in a hazy patch due to rubber domains. Therefore, dedicated stainless-steel storage and conveying for the clarified compound are mandatory. The finished tumbler is tested for stacking load at
60 °C per
ASTM D2659 with a maximum deformation of
1.5 mm.When PP 1304E5 is selected as the base resin for microwaveable food trays—commonly compartmentalised ready-meal trays—the compound is reinforced with
20 wt% high-aspect-ratio talc (
d50 ≤ 2.5 µm) to raise the heat deflection temperature (HDT) to at least
125 °C under
0.45 MPa per
ASTM D648, and to reduce warpage during microwave reheating cycles of up to
3 minutes at
900 W. The masterbatch blending is performed at the extruder throat using a gravimetric feeder with an accuracy of
±0.5 %, and the compound is melt-mixed in a single-screw extruder with a grooved feed section and a dispersion mixing head, melt temperature
235 – 245 °C, to ensure talc platelet exfoliation without polymer chain scission.Compliance for these trays demands the more stringent testing conditions of
EU 10/2011 article 12 for fatty foods, using simulant D2 at
100 °C for
2 hours for microwave use, and specific migration testing for the talc purity, which must show no more than
0.1 mg/kg of soluble aluminium as per
EN 71‑3 adapted for food contact. Antioxidant loading is increased to
0.25 wt% of a high-molecular-weight phenolic stabilizer and
0.15 wt% of a phosphite to compensate for oxidative conditions during microwave heating; the total extractives must not exceed
50 mg/kg finished article. During sheet extrusion, the die is designed with a coat-hanger manifold and a restrictor bar gap of
2.5 mm to accommodate the higher viscosity of the filled melt, and the sheet is polished at
80 °C/
90 °C rolls to minimize surface defects.Thermoforming of the filled sheet is more demanding: the heater zones in the forming station are set to deliver a surface temperature of
165 – 172 °C over
30 seconds for a
1.1 mm sheet, and a pre-stretch plug with a PTFE coating is used to avoid marring. Mold temperature is kept at
110 °C to guarantee shrinkage control—a deviation of merely
±3 °C causes inconsistent lid fitment. On the plant floor, operators regularly encounter a phenomenon known as “pitting” on the tray bottom when the melt cushion is less than
3 mm; therefore, the extruder screw speed is capped at
95 rpm for a
90 mm diameter machine. The final tray must pass a microwave cycling test of
5 cycles without cracking or migrating odor, confirmed by
DIN 10955 sensory analysis.Extruded sheet from PP 1304E5 for office filing products—ring binder covers, clipboard bodies, and index dividers—is typically produced at a thickness of
0.8 – 1.5 mm and relies on high rigidity in the machine direction, measured by a
1 % secant modulus exceeding
1 800 MPa per
ISO 527‑2. The compound distinguishes itself from food-grade formulations by incorporating a permanent antistatic agent, an ethoxylated alkylamine at
3 000 – 5 000 ppm, which reduces surface resistivity to
10¹¹ – 10¹² Ω/sq under
IEC 61340‑2‑3, preventing dust attraction during filing use. Where UV resistance is required for near-window display, a hindered amine light stabilizer (HALS) package of
0.15 % along with
0.1 % benzotriazole UV absorber is added, and the accelerated weathering test
ASTM G154 cycle 1 for
500 hours must show a color change ΔE
< 2.0 without surface chalking.Regulatory compliance moves away from food-contact statutes; the material must instead meet
REACH Regulation (EC) 1907/2006 for substances of very high concern, and the specific migration of antistatic degradates into water is irrelevant, replaced by a requirement for low VOC emission per
VDA 278 when the product is destined for indoor office environments in the EU. The sheet is extruded with a matte finish by using a hair-cell engraved cooling roller at
15 °C, and die lines are minimized by maintaining a constant die pressure of
110 – 130 bar. During cutting and punching of the final product, the material must exhibit a notched impact strength greater than
4.5 kJ/m² at
23 °C (
ISO 180/1A) to prevent cracking at rivet holes; this is achieved by keeping the melt temperature at a high end of
240 °C to eliminate frozen-in stresses and by using a downstream annealing oven set at
110 °C for
90 seconds. Tool wear in punching dies is monitored because the antistatic agent slightly corrodes untreated steel edges over
200 000 cycles; a switch to D2-grade carbide inserts is standard in high-output facilities.
When 35 % Post-Industrial Recyclate Is Incorporated into Industrial Dunnage Trays
Non-food, heavy-duty dunnage trays manufactured with PP 1304E5 as the virgin cap layer or as a blending partner for
35 % post-industrial scrap reclaim the extruder’s inherent melt stability at
4 g/10 min to counteract the viscosity drop introduced by reprocessed material. The blend is prepared offline in a heating-cooling mixer before being fed to a single-screw extruder with a vented barrel (L/D
36:1) that removes volatiles from the recyclate at a vacuum of
-0.8 bar. Melt temperature is kept at
215 – 225 °C to avoid thermal scission of the recycled fraction, and the screen changer is fitted with a
125 µm mesh to capture unmelted gels that would cause pinholes in the
2.5 mm thick sheet.Since this application is not intended for food contact, the compliance framework shifts to
ISO 14021:2016 for recycled content claims and
AFPS GS 2014:01 PAK for heavy metal limitations if the tray is exported to the German packaging market. The additive recipe is simplified:
0.05 % process stabilizer Irgafos 168 and
1 % carbon black masterbatch for UV opacity are sufficient; no costly clarifier or anti-slip agent is needed because surface defects from recyclate particles are hidden by the black color.A critical operational limit appears at the calender stack: with increasing recycled content beyond
40 %, the sheet sag in the thermoforming oven becomes uneven, resulting in a thickness variation greater than
±0.15 mm across the tray bottom. Therefore, the line speed is reduced to
4.5 m/min for a
1 200 mm wide sheet, and the bottom mold vacuum holes are resized to
0.8 mm diameter to avoid plugging by low-molecular-weight fractions. The thermoforming tool, constructed from epoxy resin rather than aluminum to handle the abrasive nature of the recycle stream, operates at a cavity vacuum of
-0.95 bar and a cycle time of
5.2 seconds. Surliness documented in production logs shows that batch-to-batch fluctuations in ash content of the recyclate exceeding
1.5 % correlate directly with pock marks on the tray walls; thus, incoming recyclate is screened through a
2 mm sieve and ash analysis by
ASTM D5630 is performed every
8 hours. Finished trays are stacked and tested for compression at
200 kg for
24 hours; creep must remain under
2 mm displacement.
| Application Scenario | Primary Food Contact Regulation | Mig. Test Condition | Specific SML Concern |
|---|
| Cold-fill dairy cup | FDA 21 CFR 177.1520, EU 10/2011 | Simulant D1 (50% EtOH), 40 °C/10 d | Irganox 1010 ≤ 300 µg/kg |
| Transparent tumbler | FDA 21 CFR 177.1520, EU 10/2011 | Simulant A (10% EtOH) & D2, 70 °C/2 h | Total migration ≤ 10 mg/dm² |
| Microwaveable tray | EU 10/2011 Art. 12 | Simulant D2, 100 °C/2 h | Aluminium ≤ 0.1 mg/kg (EN 71-3) |
| Stationery covers | REACH (EC) 1907/2006, VDA 278 | N/A (emission, not migration) | VOC ≤ 50 µg/g |
| Recycled dunnage tray | ISO 14021, AFPS GS 2014 | N/A | Heavy metals (Pb, Cd, Hg, Cr-VI) < 100 ppm sum |
| Additive Function | Food Cup | Clear Tumbler | Microwave Tray | Stationery | Recycled Tray |
|---|
| Clarifier / Nucleator | DMDBS 0.12% | Sorbitol 0.2% | N/A (talc acts) | N/A | N/A |
| Antioxidant | 0.08/0.08% 1010/168 | 0.06/0.10% 1010/168 | 0.25/0.15% HP136/168 | 0.12/0.12% B225 | 0.05% 168 only |
| Slip / Anti-block | Erucamide 1 000 ppm | Silica 1 200 ppm | N/A | N/A | N/A |
| Antistatic | N/A | N/A | N/A | Alkylamine 3 000 ppm | N/A |
| UV Stabilizer | N/A | N/A | N/A | 0.15% HALS + 0.1% BTA | 1% carbon black |
| Filler | N/A | N/A | 20% talc d50 ≤ 2.5 µm | N/A | N/A |
ExxonMobil PP 1304E5 is a polypropylene homopolymer resin formulated with a medium-slip and medium-antiblock additive package, targeted primarily at chill‑roll sheet extrusion and subsequent thermoforming operations for rigid packaging. The polymer carries a nominal melt mass‑flow rate of
4.0 g/10 min (
ISO 1133‑1:2022, 230 °C/2.16 kg) and a density of
0.905 g/cm³ (
ISO 1183‑1). Its molecular architecture, designed around a broad molecular‑weight distribution, imparts sufficient melt strength to draw sheet in the melt phase without excessive sag while maintaining a practical balance between processability and stiffness in the solid state. Typical solid‑state tensile yield strength, measured according to
ISO 527‑2:2012 on injection‑moulded test specimens, falls at
34 MPa, with a flexural modulus of
1450 MPa (
ISO 178) and a Charpy notched impact strength of
4.0 kJ/m² at
23 °C (
ISO 179‑1/1eA). The additive package, typically comprising erucamide and a synthetic silica antiblock, lowers the dynamic coefficient of friction to the range
0.25–0.35 (
ASTM D1894) and restricts film‑to‑film blocking during roll‑stack winding, allowing sheet to be unwound at high line speeds on downstream forming equipment. These attributes position 1304E5 for shallow‑ and medium‑draw thermoformed articles—dairy tubs, margarine containers, portion packs, and thin‑walled trays—where consistent de‑nesting and rapid mould release are production‑critical.
What distinguishes PP 1304E5 from standard extrusion homopolymers?
The primary differentiator is the built‑in slip‑antiblock system, which removes the need for a masterbatch let‑down at the extruder throat and thereby eliminates the concentration variability that frequently causes gauge‑band disturbances during sheet take‑off. In contrast to a non‑slip, non‑nucleated extrusion grade such as ExxonMobil PP 1304E1, 1304E5 sacrifices a small increment of stiffness—flexural modulus typically
50–150 MPa lower and heat deflection temperature (
ISO 75‑2, Method Bf, 0.45 MPa) reduced by about
5–10 °C relative to nucleated analogues—in exchange for far broader operational latitude across varying line speeds and chill‑roll temperatures. PP 1304E1 relies on a nucleating package that accelerates crystallisation, pushing the Vicat softening point (
ISO 306, A50) above
155 °C and the HDT toward
100 °C, but simultaneously narrows the thermoforming window because the recrystallised sheet develops a high frozen‑in stress profile when cooled rapidly on a polished roll. For converters running multi‑cavity vacuum‑forming tools with cycle times shorter than
3 seconds, the slower crystallisation kinetics of the non‑nucleated 1304E5 translates into lower post‑mould distortion and a wider processing plateau. The absence of a nucleating agent also eliminates the characteristic “whitening” effect sometimes observed in thermoformed corner radii when pigmented nucleated sheet undergoes deep drawing.
Crystallisation kinetics and the avoidance of post‑forming warpage
On a chill‑roll sheet line, PP 1304E5 solidifies under a thermal gradient that creates a skin‑core morphology: a highly quenched, amorphous‑rich skin sandwiched around a slowly cooled, spherulitic core. The isothermal crystallisation half‑time, determined by differential scanning calorimetry at
130 °C, is approximately
30 seconds for this non‑nucleated homopolymer, whereas nucleated formulations crystallise in under
10 seconds under identical conditions. The longer half‑time allows the crystallisation front to propagate more gradually, reducing residual stress anisotropy that otherwise manifests as out‑of‑plane warpage after the sheet is reheated to the forming temperature of
130–150 °C. For sheet gauges exceeding
1.0 mm, this relaxation‑friendly behaviour is decisive: converters who substitute a nucleated grade frequently report corner‑curl in flat rectangular trays, necessitating post‑forming annealing steps that are entirely avoidable with 1304E5. The upper service limit of the formed article, governed largely by the heat deflection temperature under low load (
90 °C at
0.45 MPa, ISO 75‑2 Method B), remains sufficient for hot‑fill applications up to
85 °C when wall thickness is designed to
0.8–1.2 mm. Processors should note that blending 1304E5 with regrind containing nucleated material from an upstream line can inadvertently accelerate crystallisation and reintroduce the warpage problem; a regrind fraction above
30 wt% of mixed‑grade material has been observed on commercial lines to shift the sheet’s relaxation shrinkage by more than
0.5 % in the transverse direction.
When processing PP 1304E5 on a single‑screw extruder with an L/D ratio of
24:1 to
30:1 and a compression ratio of
2.8:1 to
3.2:1, the melt temperature measured at the die adapter should be maintained between
220 °C and
240 °C. Operation below
210 °C risks sharkskin melt fracture at the die lip, particularly when the polymer contains process‑stabilised peroxide residues from controlled‑rheology production. The extruder barrel profile is typically set with a feed zone at
180 °C, a compression zone at
200–220 °C, and a metering zone at
220–230 °C, with the screen changer and melt pump maintained at
230 °C. A gear pump positioned between the extruder and the flat‑sheet die is strongly recommended for any line targeting sheet‑thickness variation tighter than
±3 % of nominal gauge. With a melt pump, the pressure fluctuation at the die entry can be held below
0.5 MPa, enabling a polished roll‑stack finish that meets Class‑A surface quality demands for in‑mould labelling.
Regulatory compliance in food contact applications rests on the homopolymer backbone’s conformity with the positive lists of
FDA 21 CFR 177.1520(c) item 1.1 for olefin polymers and
EU Regulation 10/2011 for plastic materials and articles intended to come into contact with food. The slip and antiblock additives employed are generally recognised as safe for use under the same frameworks, provided the overall migration limit of
10 mg/dm² (EU) is respected. The grade is also suitable for appliances covered by
RoHS Directive 2011/65/EU and is registered under
REACH (EC) 1907/2006.
Regulatory compliance matrix for PP 1304E5 in food‑contact packaging
| Regulatory framework | Relevant clause / item | Condition of use |
|---|
| FDA 21 CFR | 177.1520(c) Item 1.1 | All food types up to boiling‑water sterilisation, provided wall thickness ≥ 0.5 mm |
| EU 10/2011 | Annex I, PM/REF 14200 (homopolymer) | Overall migration ≤ 10 mg/dm²; specific migration of erucamide ≤ 5 mg/kg (simulant D) |
| RoHS 2011/65/EU | Article 4, Annex II | Lead, mercury, cadmium, hexavalent chromium, PBBs, PBDEs below threshold |
| REACH (EC) 1907/2006 | Title VIII (authorisation list) | No substances of very high concern present above 0.1 wt% |
When gauge uniformity demands exceed ±3 % of nominal sheet thickness
Stable melt delivery becomes the limiting factor well before the polymer rheology itself. Although the Carreau‑Yasuda fit of the viscosity curve for PP 1304E5 shows a zero‑shear viscosity of approximately
2800 Pa·s at
230 °C and a power‑law index of
0.35 in the shear rate window of
100–1000 s⁻¹, the actual sheet‑thickness variation measured downstream is dominated by extruder screw beat (typically
2–4 Hz on a
90 mm screw rotating at
70 min⁻¹) and melt‑pump synchronization errors. Commercial lines producing sheet at a target gauge of
0.8 mm with a tolerance of
±0.025 mm (±3 %) routinely employ a horizontally fed, continuously metered gear pump coupled with a closed‑loop die‑bolt actuation system that references a traversing beta gauge at the roll stack. The melt temperature at the pump inlet must be held above
230 °C to prevent the formation of a cold plug near the pump seals; a temperature dip as small as
5 °C has been documented on a
120‑mm extruder line to increase pressure variation from
0.3 MPa to
0.8 MPa, enough to exceed the gauge window within
20 minutes of production. A flexible‑lip die with a final land length of
20–25 mm and a die gap set to
0.5–0.7 mm above the intended final sheet thickness allows the draw‑down ratio to be kept below
1.5:1, minimising both edge‑bead and transverse‑direction orientation that could later cause differential shrinkage in the thermoforming oven.
Comparative physical properties of selected ExxonMobil polypropylene grades (typical values, not specifications)
| Property | Test method | PP 1304E5 | PP 1304E1 | PP 1104E5 |
|---|
| MFR (230 °C, 2.16 kg) | ISO 1133‑1 | 4.0 g/10 min | 4.0 g/10 min | 11 g/10 min |
| Tensile stress at yield | ISO 527‑2 | 34 MPa | 35 MPa | 33 MPa |
| Flexural modulus | ISO 178 | 1450 MPa | 1650 MPa | 1500 MPa |
| Charpy notched impact, 23 °C | ISO 179‑1/1eA | 4.0 kJ/m² | 3.5 kJ/m² | 3.0 kJ/m² |
| HDT (0.45 MPa) | ISO 75‑2 Method B | 90 °C | 100 °C | 88 °C |
| Vicat softening point (A50) | ISO 306 | 155 °C | 158 °C | 152 °C |
| Coefficient of friction (film‑to‑film) | ASTM D1894 | 0.25–0.35 | 0.50–0.70 | 0.30–0.40 |
In direct contrast to high‑fluidity injection‑moulding grades, PP 1304E5 operates in a melt‑strength‑limited regime where excessive melt temperature, although lowering viscosity, leads to sheet sag between the die and the primary chill roll. Thermoforming trials on a
300 mm‑wide flat‑sheet line at a take‑off speed of
12 m/min have demonstrated that a melt‑temperature increase from
230 °C to
250 °C can cause sag‑induced thickness reduction at the sheet centre by as much as
7 % relative to the edges, worsening with wider sheet widths. Therefore, converters aiming for a sheet width above
800 mm are advised to equip the air gap with an edge‑pin stabilisation system and to keep the gap below
25 mm. Simultaneously, the chill‑roll temperature must be controlled between
15 °C and
30 °C to impart a high surface gloss without quenching the core so rapidly that the depth of the amorphous skin exceeds
15 µm, a threshold beyond which subsequent reheating in a quartz‑tube oven produces an uneven temperature profile through the sheet thickness, leading to plug‑assist sticking and local thinning. Published data for this specific combination of roll‑gap and melt‑temperature setpoints is limited, making on‑line infrared thermography an essential complement to the standard sag‑eye visual inspection.
Where cycle‑time economics push thermoformers towards polypropylene random copolymers, a comparison with ExxonMobil PP 6234E5 (ethylene‑propylene copolymer, MFR
4.0 g/10 min) highlights the rigidity‑clarity trade‑off. The random copolymer offers superior optical properties—haze below
15 % in
1 mm sheet—at the cost of a flexural modulus drop to approximately
1100 MPa and a lower HDT, around
78 °C, rendering it unsuitable for hot‑fill applications without a secondary crystallinity‑enhancing extrusion step. PP 1304E5 retains the homopolymer modulus and thermal resistance while accepting a slightly hazy appearance (haze typically
25–40 % at
1 mm) that is routinely masked by pigmentation or opaque printing in its target dairy and margarine end uses. The slip‑antiblock system of 1304E5 further differentiates it from a random copolymer containing only an antiblock agent, where the absence of a migratory amide leads to blocking forces that can stop automatic de‑stacking stations after prolonged warehouse storage at temperatures exceeding
35 °C.
Storage and pre‑processing handling of PP 1304E5 are subject to the moisture sensitivity typical of polypropylene homopolymers containing no hygroscopic filler. The pellets, supplied in
25‑kg bags or octabins, may be fed directly to the extruder throat without pre‑drying, provided ambient relative humidity has remained below
60 %. Exposure to high‑humidity environments for periods longer than
48 hours can result in surface moisture that, although not causing hydrolytic degradation of the polymer backbone, generates splay and pinhole‑sized depressions on the extruded sheet, detectable at the beta gauge as periodic low‑density spots. In such cases, a dehumidifying dryer operating at
80 °C for
2 hours with a dew point of
−30 °C restores a surface‑dry condition. The product must not be blended with amine‑based processing aids, as the primary amide slip additive (erucamide) can competitively react under extrusion‑grade shear and temperature, reducing the effective concentration of both species.
