IV Drop and Acetaldehyde Control in Carbonated Soft Drink Preform Molding

Preform injection of YS-C02 on 48-cavity to 144-cavity hot-runner systems is run with rear barrel zones at 245–260°C, center zones at 265–275°C, and nozzle setting at 275–285°C. The narrow band between center and nozzle is held because localized melt temperature above 290°C for more than a few seconds causes ester pyrolysis and acetaldehyde formation. Virgin pellets are dried at 160–170°C for 4–6 h with supply air dew point below -40°C, reducing moisture to 35 ppm or lower. Moisture above 40 ppm at feed enters the melt and produces hydrolytic chain scission that can be measured as intrinsic viscosity loss under ASTM D4603-18. In cold-fill preforms, the loss relative to pellet is held at ≤0.02 dL/g; when loss exceeds 0.04 dL/g, the reheat blow window narrows and preform haze increases when inspected under polarized light. A hot-runner temperature set 5–10°C below the nozzle prevents gate crust and premature nucleation; gate diameters below 1.8 mm raise shear heating and acetaldehyde in the gate vicinity, which is quantified by ASTM F2013-10.

Preform weight variation above ±0.5 g in a 96-cavity line causes wall-thickness distribution in the blow container to exceed ±0.15 mm and can increase sidewall burst failure at the stretch panel transition. Food-grade bottle-to-bottle rPET is metered at 10–25 wt% for cold-fill preforms where the rPET stream carries a migration clearance; higher addition levels widen the preform intrinsic viscosity distribution because the rPET pellet IV is lower than virgin YS-C02. The preform body wall for a 500 mL carbonated soft drink bottle is maintained between 2.2 mm and 3.6 mm depending on fill pressure and bottle geometry. Reheat blow molding sets preform surface temperatures at 105–115°C for CSD-grade sidewall distribution. Surface temperature below 100°C causes stretch whitening; temperature above 120°C shifts the natural draw ratio and produces petaloid base folds. Axial stretch ratio is specified between 2.6:1 and 3.1:1, while hoop stretch ratio is specified between 3.3:1 and 3.8:1. Cold mold temperature is held at 8–12°C, and base cooling channels are separately controlled at 10–14°C because the petaloid geometry has the highest residual wall thickness and slowest heat removal.

Finished containers on CSD lines are sampled for carbonation retention by ASTM F1115-95(2011), burst strength by internal pressurization, and top load after 24 h at 38°C. Food-contact compliance is controlled under FDA 21 CFR 177.1630 for PET used with aqueous and carbonated beverages, European Commission Regulation (EU) No 10/2011 with EN 1186 migration testing, and GB 4806.7-2016 for China market entries. The terminal products are still water bottles, carbonated soft drink bottles, and mineral water bottles in volume ranges from 250 mL to 2.0 L. The same resin lot may be run across all formats, but tool-specific preform mass must be recalculated to avoid shifting from the validated stretch ratio band when cavity count and neck finish change.

Heat-set blow molding diverts YS-C02 from the standard cold-fill path when pasteurized juice and tea require sidewall crystallinity above the ambient-mold baseline. Mold temperatures are raised to 125–145°C instead of 8–12°C, and the preform body is held against the hot cavity for 1.8–2.5 s; shorter contact gives sidewall shrinkage after hot filling above 85°C, while longer contact reduces throughput and raises bottle release problems. The sidewall crystallinity after heat-set blowing is measured by differential scanning calorimetry in the range 30–35%; at levels below 25%, the bottle can lose more than 1.5 vol% after an 88°C fill. The neck and thread region remains largely amorphous because it is not in intimate contact with the heated cavity; this creates a mismatch in creep resistance, so closure bridges are specified with deeper thread engagement to avoid unseating at fill temperatures above 65°C.

The preform design for hot-fill differs from cold-fill in that shoulder and lower body wall sections are thickened by 0.3–0.5 mm; this supplies material for vacuum panel movement and compensates for the absence of a gas-pressure support in the filled bottle. Injection parameters are kept at the same barrel settings as cold-fill preform, but cycle time increases by 5–10% due to the higher gate mass. No nucleating additive is blended into YS-C02 for heat-set applications; the crystallinity is induced by mold contact, not by a chemical nucleation package. Hot-fill body diameter after filling may show asymmetric shrinkage across mold halves if moving-side and stationary-side cavity temperatures differ by more than 5°C; blow-machine mold channel balancing is used to limit side-to-side variation to 2–3°C. If vacuum panel geometry is too shallow, internal vacuum after sealing draws the panel inward and may cause crease whitening during distribution. The terminal products are 300–1000 mL hot-filled juice bottles, isotonic drinks, and ready-to-drink tea bottles. Compliance for hot-filled packaging still requires FDA 21 CFR 177.1630 or EU (EU) No 10/2011 because the container shell is a monolayer PET in direct contact with aqueous acidic food; the fill and pasteurization temperature is not exempt from migration verification.

When Sheet Extrusion Feed Moisture Exceeds 40 ppm at the Die Lip

Moisture entering a flat-die sheet line above 40 ppm changes PET melt viscosity through hydrolysis before the primary calendering rolls. The result is a loss in melt strength that appears as draw resonance, edge waver, and die-lip deposit formation. YS-C02 sheet is dried at 160–170°C for 4–6 h to ≤45 ppm moisture, using desiccant-bed dryers with a dew point of -40°C or below. A single-screw extruder with 30:1 L/D and a barrier screw produces melt temperature of 270–280°C; barrel settings range from 245°C at the feed throat to 275°C at the die adapter. Higher melt temperatures produce yellowing and gel formation; lower temperatures raise melt pressure above 120 bar and cause uneven die flow. Regrind particle size and fines can alter bulk density and drying uniformity; screening above 6 mm and fines removal below 0.5 mm is typical before reintroduction.

After exit from the flat die, the melt enters a three-roll polishing stack with roll temperatures of 40–60°C to quench the sheet before winding. Sheet thickness for thermoformed food packaging is typically 0.35–1.10 mm; line speed is adjusted to maintain polished contact time within 3–6 s. Edge trim is reintroduced at 20–40 wt% by proportioning feeder, but the trim must be ground and redried because its intrinsic viscosity is normally 0.03–0.07 dL/g below virgin YS-C02 after one extrusion cycle. The extruded sheet is reheated in a forming oven at 130–150°C, then plug-assisted thermoformed into trays, clamshells, bakery containers, and fruit punnets. Forming mold temperature is held at 70–90°C; above 90°C, the sheet can stick to the plug assist and create ghost marks, while below 70°C, part shrinkage after trimming increases. Final food-contact status is assessed under FDA 21 CFR 177.1630 and EU (EU) No 10/2011; migration testing per EN 1186-1 through EN 1186-15 is required on the finished article because thermoforming changes surface area-to-volume ratio and draw-induced thickness distribution. Terminal products include refrigerated dairy cups, bakery clamshells, produce trays, and egg carton inserts.

In high-tension polyester strapping, orientation-induced crystallinity rather than preform clarity determines whether YS-C02 reaches minimum break strength under ASTM D3950. The resin is extruded on a single-screw line at 270–285°C, quenched in a water bath at 55–70°C, and drawn through a heated orientation stage at draw ratios from 5.0:1 to 6.5:1. If draw ratio drops below 4.5:1, the final strap tensile strength remains below 300 N/mm² and may fail on sharp coil edges; if draw ratio exceeds 6.8:1, fibrillation and width variation appear. After orientation, a relaxation zone permits 2–5% retraction to reduce residual shrinkage when the strap is stored in high-temperature logistics environments.

Strap width and thickness are tool-specific, commonly 12–19 mm and 0.6–1.2 mm for steel coil packaging; the embossing pattern is impressed before winding to raise bundle friction without creating crack initiation points. YS-C02 processed into strapping must be dried to ≤50 ppm moisture; hydrolysis in the extruder lowers melt strength and produces gels that appear as periodic weak spots in the oriented strand. Because strapping is a heavy-walled oriented article, edge fibrillation and die swell are more sensitive to resin lot-to-lot IV variation than container preforms; published data for YS-C02 in high-speed strapping dies is limited, so line trials are required to quantify the pressure coefficient of the melt pump at throughput beyond 300 kg/h. The terminal products are polyester strapping for steel coils, glass bundles, pallets, and unitized loads; unlike textile yarn, strapping is not subject to food-contact migration testing but must comply with REACH registration and the buyer’s heavy-metal and phthalate limits in packaging waste directives.

What Limits the Use of YS-C02 in Fatty Food Simulant D2 for Edible Oil Bottles?

Fatty food contact imposes a different stress-cracking and migration profile than still water. The preform injection and blow molding parameters for edible oil bottles are similar to CSD, but the stretch ratio is often reduced in the body to leave slightly thicker walls, because oil-filled bottles are not gas-pressure-stabilized and must resist buckling under column load. Typical body wall thickness after blowing is 0.40–0.60 mm for a 1 L oil bottle, compared with 0.25–0.35 mm for a carbonated drink bottle of the same volume. The neck finish is reinforced to prevent oil-induced environmental stress cracking; oil contact can accelerate craze growth in the threaded finish under top load, especially at warehouse temperatures above 35°C. Injection melt temperatures are maintained at 270–285°C, and preform surface temperature before blowing is set at 105–115°C, with mold chillers at 10–14°C.

Migration testing for oil-filled PET uses fatty food simulant D2 under EU (EU) No 10/2011, not simulant A (10% ethanol) used for aqueous foods; the FDA route uses food-type conditions under 21 CFR 177.1630 and, if applicable, the oil’s actual fill volume and surface area. Vinegar filling at acetic acidity above 3% may require simulant B migration testing under EU (EU) No 10/2011, and the cap liner is a separate migration source that must be included in the finished-article verification. The terminal products are 250 mL–5 L edible oil bottles, vinegar bottles, and condiment bottles with cap and pull-ring sealing systems. Long-term storage of oil-filled YS-C02 bottles at freezing temperatures is limited by reduced impact resistance; the material’s ductile-to-brittle transition can be approached in refrigerated distribution, so drop tests at 4°C are recommended before specifying lightweighted sidewalls. Acetaldehyde is less organoleptic-critical in oil than in water, but migration of low-molecular-weight esters and aldehydes into mild-flavoured oils must be verified if the filling line uses post-consumer recycle in the melt.