Technical Deep Dive · Process Engineering · Korean ISBM 2026
Conditioning temperature is the single parameter that most Korean ISBM operators adjust most frequently and understand least precisely. It controls orientation quality, clarity, wall distribution, and cycle time simultaneously — and its process window is narrower than most Korean production teams assume. This guide maps the window for PET, PETG, and PP with the precision that EV servo machines make achievable.
Conditioning Temperature Process Windows — Korean ISBM 2026
| Harpiks | Tg (°C) | Lower Limit | Optimal Centre | Upper Limit | Window Width | Under-Temp Failure |
|---|---|---|---|---|---|---|
| PET (standard) | 72–80°C | 95°C | 103°C | 112°C | ~17°C | Thin shoulder, poor top-load |
| PET (CSD, high-orient) | 72–80°C | 100°C | 106°C | 112°C | ~12°C | Base rollout, CO₂ loss |
| PETG | 78–82°C | 75°C | 83°C | 92°C | ~17°C | Haze, poor clarity |
| Tritan (TX1001) | 110–115°C | 80°C | 88°C | 98°C | ~18°C | Thin body, high scrap |
| PP (random copolymer) | −20 to 0°C | 15°C | 28°C | 40°C | ~25°C | Thick wall, poor clarity |
All temperatures are measured at preform surface in the conditioning station under steady-state production conditions (not during first 15 minutes of production). EV servo systems maintain ±0.3°C at setpoint; hydraulic systems typically show ±1.5–2.5°C variation. Window width values represent the range across which bottle quality passes standard commercial specification — not the range for premium applications.
The conditioning station in Korean 4-station ISBM performs one function: raising the preform temperature from the injection temperature (typically 5–15°C above ambient by the time it arrives at conditioning) to the orientation temperature — the specific temperature at which the plastic’s polymer chains are mobile enough to stretch and orient without either failing (too cold) or flowing uncontrollably (too hot). The temperature at which this “Goldilocks” state exists is defined by the resin’s glass transition temperature (Tg) — the boundary between glassy (rigid, brittle) and rubbery (soft, stretchable) polymer behaviour.
What makes conditioning temperature so powerful is that it simultaneously controls four independent bottle quality parameters: (1) orientation quality and hence bottle strength — higher orientation temperature generally produces better crystallinity and chain alignment in PET; (2) wall thickness distribution — conditioning temperature controls how readily material flows during stretch rod extension; (3) optical clarity — over-conditioning causes surface crystallisation that produces haze, while under-conditioning leaves insufficient orientation for the clarity that K-Beauty PETG requires; (4) cycle time — conditioning temperature directly affects the minimum conditioning dwell time needed before blow, which is a primary component of cycle time. Adjusting conditioning temperature to improve one parameter always affects the other three — understanding these interactions prevents the trial-and-error parameter adjustment that consumes Korean ISBM production time. The molecular science underpinning the orientation state is explained in the biaxial molekylær orienteringsvejledning.
The preform temperature in the conditioning station is measured at the preform surface — but the parameter that drives orientation behaviour is the preform bulk temperature (average through-wall temperature). For thin-wall preforms (wall ≤ 3.0mm), surface and bulk temperatures equilibrate rapidly (within 8–12 seconds of conditioning at temperature). For thick-wall preforms (wall ≥ 4.5mm, typical for CSD and large-format bottles), the thermal gradient between surface and core can remain 8–15°C even after 18–22 seconds of conditioning — meaning the surface may be at the correct orientation temperature while the core is still below Tg, producing inadequate orientation in the inner wall layer. Korean CSD and large-format ISBM producers should account for this gradient in their conditioning time specification, not just their conditioning temperature specification.
Standard PET ISBM has a conditioning temperature process window of approximately 95–112°C — a 17°C span that represents the full range from “barely adequate orientation” to “crystallisation-induced haze.” Within this span, Korean ISBM operators have a quality optimum that varies by bottle format:
95–99°C — Low End of Window
The preform is at the minimum temperature for meaningful biaxial orientation. Material flows reluctantly under stretch rod force, concentrating distribution toward the lower body. Shoulder zone wall is thin. Top-load performance is borderline. Clarity is excellent (low crystallisation rate at this temperature). Korean producers who run at this temperature to extend the conditioning heater life or reduce energy consumption pay the cost in higher top-load failure rates, particularly on shoulder-critical formats like K-Beauty cosmetic bottles.
100–107°C — Optimal Production Zone (most Korean PET applications)
The preform has excellent orientation mobility. Wall distribution is even. Top-load meets specification. Cycle time is at or near minimum for the preform geometry. Clarity is high (crystallinity is developing but haze threshold not yet reached for standard wall thickness). This is where Korean ever-power production is targeted for standard PET food, beverage, and personal care formats. Korean producers running in this range on an EV servo machine should see consistent bottle weight CV% below 4% at Zone 4 and below 6% at Zone 6.
108–112°C — Upper End of Window
The preform is approaching the over-conditioning zone. Material flows very freely, improving shoulder distribution and top-load — but surface crystallisation begins, manifesting as a white haziness at the shoulder and neck transition zone in K-Beauty PETG production. For standard clear PET beverage bottles, the haziness is less visible (lower crystallisation rate in PET vs PETG at equivalent temperature), but clarity is measurably lower than at 100–107°C. Korean producers should not target this zone as a standard operating point — it is the emergency correction zone for persistent thin-shoulder defects that have not responded to rod timing and speed adjustments.
The over-conditioning failure mode — shoulder haze specifically — is caused by the onset of strain-induced crystallisation at temperatures above 108°C in PET. The crystallites that form at over-conditioning temperature are fine and numerous, scattering light and producing the characteristic “milky” appearance at the neck-shoulder zone that Korean K-Beauty brand auditors immediately identify. This haze cannot be removed in post-processing; it requires a process correction (reducing conditioning temperature 3–5°C) and the rejection or downgrading of all bottles produced in the over-conditioned state. The over-conditioning haze defect and its diagnosis are catalogued in the Korean ISBM bottle defects field guide.
PETG’s conditioning temperature window (75–92°C) is similar in absolute width to PET (approximately 17°C), but the consequences of straying outside the window are more severe for Korean K-Beauty applications where optical clarity is the primary quality specification. PETG does not develop strain-induced crystallinity the same way PET does — the glycol comonomer disrupts crystallisation — but it has a different sensitivity: at temperatures below 78°C, PETG orientation efficiency drops sharply, producing bottles with visible stress-whitening in the shoulder zone from inadequate chain alignment (the chains cannot orient at temperature this close to Tg). At temperatures above 88°C, PETG over-softens and the fine melt-flow lines that are always present in PETG melt (from the gate fill path) become permanently visible as streaks or “tiger lines” in the bottle wall, visible under direct light at retail.
For Korean K-Beauty PETG production, the effective usable window is narrower than the absolute window — approximately 80–87°C is the range where both optical quality criteria (no stress-whitening, no streaking) and mechanical performance (adequate top-load, adequate drop impact) are simultaneously achievable. This 7°C effective window requires EV servo conditioning temperature control at ±0.3°C to consistently stay within it — on a hydraulic machine with ±2°C temperature variation, the effective window is consumed by machine variation alone, and the production alternates unpredictably between stress-whitening and streaking without any operator intervention.
The fundamental difference between PET and PETG that drives the different temperature sensitivity — specifically the glycol modification’s effect on chain mobility and crystallisation kinetics — is detailed in the PET vs PETG resin selection guide, which provides the molecular chemistry context for the process window differences.
Tritan’s Tg is substantially higher than PET and PETG (110–115°C for Eastman TX1001), which creates an important conditioning temperature paradox: Tritan is conditioned and blown at 80–98°C — which is below its Tg. This appears to contradict the fundamental principle that orientation occurs above Tg. The explanation is that Tritan’s broad amorphous relaxation temperature range means the secondary beta transition (below the main Tg peak) provides sufficient chain mobility for biaxial orientation at temperatures 12–30°C below the main Tg — a property that enables Tritan’s steam-sterilisation resistance (the oriented network resists deformation below Tg) while still allowing ISBM processing.
Practically, this means Korean Tritan ISBM operates in a conditioning zone where the preform feels stiffer than PET at equivalent conditioning temperature — requiring higher stretch rod force and creating a narrower window between “not stretched” and “over-forced.” The EV servo stretch rod force feedback on Korean Ever-Power EV platforms provides the data to manage this precisely: monitoring the servo current draw during stretch rod extension gives real-time preform resistance data that indicates whether the conditioning temperature is producing adequately mobile material. A sudden increase in stretch rod servo current at constant temperature indicates the preform has cooled below the effective orientation zone — a condition that typically precedes a bubble-burst or thin-shoulder defect event. This real-time feedback loop is the EV system capability that Tritan ISBM production depends on, and it is not available on standard hydraulic platforms.
PP ISBM conditioning temperature operates near room temperature — 15–40°C for PP random copolymer — which creates a conditioning challenge opposite to PET: the conditioning station must provide controlled cooling rather than heating. Korean PP ISBM machines use chilled water conditioning (typically 10–18°C water temperature) to bring the PP preform from its injection temperature (approximately 50–70°C above ambient by the time it arrives at conditioning) down to the orientation zone.
PP’s crystallisation behaviour during conditioning creates the paradox: PP crystallises faster than PET in the 30–80°C temperature range (the crystallisation half-time for PP is approximately 2–8 minutes at 30°C versus 6–12 minutes for PET). This means if the PP preform spends too long at conditioning temperature before blow, crystallinity increases and orientation quality decreases — the opposite of PET, where longer conditioning improves orientation quality. Korean PP ISBM conditioning dwell time must therefore be minimised (typically 6–10 seconds at 20–30°C) to blow the PP before excessive crystallinity develops.
The practical consequence is that Korean PP ISBM cycle times tend to be shorter than equivalent PET production — not because PP conditioning temperature is lower, but because the conditioning dwell time is minimised to prevent crystallisation. This shorter dwell time partially compensates for PP’s other cycle time disadvantages (lower blow pressure acceptance, slower cooling due to lower thermal conductivity than PET). The relationship between conditioning time, cycle time, and production economics is modelled in the 5-lever Korean ISBM cycle time optimisation framework.
Korean 4-station ISBM conditioning stations divide the preform height into 3 independent temperature zones: base zone (lower 30% of preform, covering the gate area and base-forming material), body zone (middle 45% of preform, covering the primary body wall), and shoulder zone (upper 25% of preform, covering the material that will form the shoulder and upper body). Each zone is independently controlled, allowing deliberate axial temperature gradients that compensate for preform geometry and wall distribution requirements.
| Zone | Standard Setting (PET) | Thin Shoulder Correction | Thick Base Correction | Effect of Zone Increase |
|---|---|---|---|---|
| Base zone (Z1) | 100–103°C | −2 to −3°C | +2 to +4°C | More material flows toward base → thicker base, thinner body |
| Body zone (Z2) | 103–106°C | ±0 (reference) | ±0 (reference) | Primary orientation quality control — do not adjust without necessity |
| Shoulder zone (Z3) | 106–109°C | +3 to +5°C | −2 to −3°C | More material flows toward shoulder → thicker shoulder, better top-load |
The zone temperature gradient table above shows that thin-shoulder correction in Korean ISBM is primarily achieved by increasing the shoulder zone (Z3) temperature relative to the body zone (Z2) — not by increasing the overall average conditioning temperature. This zone-differential approach corrects the distribution problem without entering the over-conditioning zone that causes shoulder haze. Korean ISBM producers who resolve thin-shoulder problems by increasing overall conditioning temperature — the most common “quick fix” — are trading a distribution problem for a clarity problem. Zone-selective correction is the engineered solution; overall temperature increase is a workaround that creates its own consequences. The preform design foundations that determine the achievable distribution from a given zone temperature profile are in the ISBM preform design guide.
Under-Conditioning Failure Signatures
Thin shoulder: Zone 6 wall below minimum; top-load failure. Cause: Z3 temperature below effective orientation threshold.
Preform burst: Bubble-burst during blow at stretch rod mid-point. Cause: Material too cold to stretch without fracture; occurs below 92°C in PET.
Stress whitening: Opaque white patches at stretch points. Cause: Excessive force applied to cold-zone material — chains break rather than orient.
Thick wrist/lean body: Material piling up at shoulder-body junction. Cause: Insufficient material mobility at Z3 prevents shoulder zone from forming.
Over-Conditioning Failure Signatures
Shoulder haze: Milky-white cloudiness at shoulder-neck zone in PET/PETG. Cause: Strain-induced crystallisation at elevated temperature; fine crystallite light scattering.
Tiger-line streaking: Parallel flow lines visible in PETG bottle body under light. Cause: Over-softened PETG retains melt-flow lines from gate fill at excessive temperature.
Thin body / thick shoulder: Distribution reversal. Cause: Over-mobile material flows from base/body toward shoulder under gravity during conditioning dwell.
Poor top-load despite thick shoulder: Wall thickness adequate but orientation quality low. Cause: Over-crystallised material at shoulder has reduced uniaxial strength despite adequate thickness.
The production economic argument for all-servo EV drive systems in Korean ISBM is typically made on energy savings (35–45% lower energy consumption) and machine longevity. The conditioning temperature precision argument is equally compelling but less widely quantified. A Korean ISBM operation running a hydraulic machine with ±2°C conditioning temperature variation on a PET process window that is 17°C wide loses approximately 23% of the window to machine variation alone — spending 23% of its production time outside the optimal zone, generating borderline-quality bottles that may or may not pass final QC.
For PETG K-Beauty production with an effective 7°C window, ±2°C variation from a hydraulic system consumes 57% of the window — the machine spends more than half its time outside the zone that simultaneously satisfies clarity and mechanical performance requirements. The resulting defect rates (shoulder haze events, tiger-line batches, stress-whitening episodes) create scrap and quality rejection costs that typically exceed the energy saving and depreciation premium of an EV servo machine within 18–30 months of production. This calculation should be explicit in any Korean EV vs hydraulic machine ROI analysis for K-Beauty and premium supplement ISBM investment.
The conditioning temperature precision argument is one of 10 factors evaluated in the Korean ISBM machine selection framework. For applications where conditioning window width is below 10°C (PETG K-Beauty, Tritan, CSD PET), EV servo is the correct specification regardless of volume. For applications where the window is above 15°C and the product specification is standard beverage quality, hydraulic remains an economically defensible platform choice.
Q1 — How do we measure conditioning temperature accurately in production?
The correct measurement is preform surface temperature at the exit of the conditioning station, measured with a calibrated infrared pyrometer (emissivity set to 0.94 for PET, 0.92 for PP) immediately before transfer to the blow station. The machine’s internal conditioning thermocouple measures the conditioning mandrel or insert temperature — not the preform surface temperature — and typically reads 3–8°C above actual preform surface temperature due to the air gap between the mandrel and preform inner wall. Korean ISBM producers who calibrate their process based on machine thermocouple readings without cross-checking against actual preform IR temperature are operating on systematically incorrect temperature data. Check preform IR temperature against machine thermocouple on each new preform geometry and after each conditioning element replacement — the gap changes with element age and preform wall thickness.
Q2 — Why does the optimal conditioning temperature change between different preform batches of the same resin?
Conditioning temperature optimum shifts between preform batches for three reasons. First, IV variation: a PET resin lot with IV 0.84 dl/g requires approximately 2–3°C lower conditioning temperature than a lot with IV 0.80 dl/g at equivalent wall thickness, because higher IV material has more chain entanglement providing orientation resistance that is overcome at lower temperature. Second, moisture: preforms with higher residual moisture (from inadequate drying) have lower effective Tg because moisture acts as a plasticiser — optimum conditioning temperature drops by approximately 1°C per 50 ppm excess moisture. Third, crystallinity variation in the preform: if injection conditions vary between batches, the preform’s pre-blow crystallinity differs, affecting the temperature needed to achieve equivalent orientation mobility. Korean ISBM producers who set conditioning temperature once during mould commissioning and never revisit it accumulate quality drift as preform batches and ambient conditions change.
Q3 — How does ambient temperature in the Korean production facility affect conditioning performance?
Significantly — particularly for PP ISBM and for the low end of the PET conditioning window. In Korean summers (July–August, factory ambient 32–38°C), the preform arrives at the conditioning station approximately 3–5°C warmer than in winter (December–January, ambient 5–12°C). For PP ISBM at 20°C setpoint, this means the conditioning system must actively cool a warmer preform in summer — requiring longer conditioning dwell time or lower cooling water temperature to achieve the same preform surface temperature. For PET ISBM at 103°C setpoint, the 3–5°C warmer preform arrival means the conditioning heaters do less work and the actual preform surface temperature at fixed dwell time is approximately 1–2°C higher in summer. Korean ISBM producers with consistent seasonal quality variation (better quality in winter, shoulder haze in summer) are often experiencing this ambient temperature effect and should implement a seasonal conditioning setpoint compensation protocol (typically −2 to −3°C summer vs winter setpoint adjustment).
Q4 — Can rPET blends be conditioned at the same temperature as virgin PET?
Not without verification. rPET at 10–30% inclusion typically has lower average IV (0.72–0.80 dl/g) and higher crystallinity variation than virgin PET. The lower IV shifts the optimal conditioning temperature downward by 1–3°C at 30% rPET inclusion — because the shorter chains of rPET reach orientation mobility at a slightly lower temperature. The practical approach: when qualifying rPET blend production, run a conditioning temperature sweep (98°C → 104°C in 1°C increments, 20 bottles per step) and measure shoulder wall thickness and clarity at each step. The optimal temperature for the rPET blend will typically be 1.5–3°C lower than the optimum for the pure virgin production that previously ran on the same mould. Document this as a rPET-specific conditioning programme in the machine’s recipe library — not a manual adjustment that operators must remember to make.
Q5 — What is the recommended conditioning temperature startup procedure on a Korean ISBM machine?
Korean ISBM conditioning startup protocol: set conditioning elements to 10°C below target setpoint at machine start; allow 8–10 minutes for conditioning elements to reach steady-state before running preforms; run the first 15–20 shots at the reduced setpoint and discard (the thermal mass of the conditioning mandrels requires several cycles to stabilise at target temperature); increase to full target setpoint; run another 10 shots and perform a full 7-zone wall thickness check before accepting production. The time from setpoint change to steady-state temperature at the conditioning station is typically 6–10 minutes on EV servo machines and 8–15 minutes on hydraulic machines (slower thermal response without servo heating control). Running production during the thermal stabilisation period produces bottles with systematically low conditioning temperature that typically show thin-shoulder or stress-whitening defects — a production loss that the startup protocol eliminates.
Q6 — How does conditioning temperature affect acetaldehyde generation in Korean food contact PET production?
Acetaldehyde (AA) is a thermal degradation byproduct of PET at elevated temperatures — primarily generated during injection moulding (barrel temperatures 275–295°C) rather than during conditioning. However, conditioning temperature does contribute marginally to total AA generation: PET held at 110°C conditioning temperature generates approximately 0.8–1.2 ppb additional AA per preform pass versus PET conditioned at 100°C, through slow ester bond cleavage at the elevated conditioning temperature. For Korean food packaging applications with strict AA specifications (still water: ≤3 ppb AA in headspace), this marginal contribution can be significant if the base AA from injection is already near the specification limit. Korean food contact ISBM producers targeting ultra-low AA levels should minimise conditioning temperature to the minimum that achieves specification quality — typically 100–103°C — rather than running at 108–110°C for the convenience of extended process windows.
Process Engineering Support
Korean Ever-Power’s process engineers diagnose conditioning temperature problems remotely using your production data — preform IR temperature readings, wall thickness zone data, and bottle defect photos — and provide a specific zone temperature correction programme within 48 hours.
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