How Turkish BOPET Film Producers Configure Single Screw Extrusion Lines With Downstream MDO Stretching for High Clarity Packaging Film

Why BOPET Film Lines in Turkey Are a Different Engineering Conversation

Anyone who has toured a packaging film plant in the Istanbul, Izmir, or Gaziantep industrial corridors knows that Turkish BOPET converters run hot. The Turkish packaging market — driven by food, beverage, and personal care sectors that increasingly demand high-transparency film for retail shelf appeal — has installed more BOPET capacity in the last five years than any other European or Mediterranean country except Italy. The engineering conversation that drives these capacity decisions is the upstream extrusion line that feeds the downstream MDO stretching and biaxial orientation line.

We at Jurry have commissioned BOPET lines in Turkey, Saudi Arabia, Egypt, and Pakistan over the past decade, and our process engineering team has accumulated a service knowledge base that goes well beyond what the equipment catalog can communicate. The converter teams that come to us for a new BOPET line typically arrive with a film thickness target and a throughput target, but they often underestimate the importance of the resin drying system, the melt filtration specification, and the line balance between the extruder and the MDO. Our engineering response is to walk the converter team through each of these subsystems before the line specification is finalized.

BOPET (biaxially oriented polyethylene terephthalate) is not the same engineering exercise as commodity film extrusion. The polymer is hygroscopic, the melt is sensitive to residence time distribution, the output rates run higher than commodity film, and the optical clarity target leaves no room for gel particles or unmelted resin. A single Screw Extruder that runs HDPE pipe on a 1,500 kg/h throughput target may not deliver the melt homogeneity that a 500 kg/h BOPET film line demands.Jurry single screw extruder line and our main Jurry catalog has been engineered to bridge that gap, with configurations that serve both HDPE and PP processing in pipe and pelletizing service and the higher-homogeneity service that BOPET, CPP, and BOPP film converters require.

The Line Balance: Extruder Output Versus Downstream MDO

The most common engineering mistake on a new BOPET line is to size the extruder for a throughput that the downstream MDO stretching section cannot accept. The MDO (machine direction orienter) is the rate-limiting element in the line, because the polymer chains have to align under controlled strain and temperature, and the stretching ratio sets the throughput ceiling. A typical packaging-grade BOPET line runs the MDO at 4.0-4.5x machine direction stretch ratio, which translates to a line speed of 120-180 m/min depending on film thickness.

The single screw extruder has to feed the die at exactly the throughput that the MDO section can absorb without starving or overfeeding. Overfeeding causes melt accumulation between the die and the cast roll, which shows up as thickness variation. Starving causes line speed reductions, which translate directly into lost capacity. The correct line balance is to select an extruder with a maximum throughput that is 10-15 percent above the MDO design throughput, then operate the extruder at 85-90 percent of its maximum for steady-state production. Jurry specifies single screw extruders with L/D ratios of 30:1 or higher for BOPET service precisely to give the converter headroom to operate at the 85-90 percent sweet spot rather than at the extruder's mechanical limit.

Why Single Screw and Not Twin Screw for BOPET Film

Twin screw extruders are common in PET recycle and compounding service because their high-shear mixing geometry handles the residence time distribution of recycle-content streams. BOPET film production, however, is a different process. The melt has to be homogeneous to a tighter specification than compounding requires, and the polymer has to spend less total time at high temperature than it would in a twin screw extruder of equivalent throughput. A single screw extruder with a properly designed mixing section delivers the melt homogeneity that BOPET requires while keeping the melt residence time short enough to prevent thermal degradation.

The mixing section is the critical design element. A Maddock mixer at the end of the screw breaks up the laminar flow that a standard metering section produces and forces the melt through a restrictive channel that creates back-mixing. A pineapple mixer is a milder alternative that provides distributive mixing without the pressure drop of a Maddock mixer. For BOPET service, the Maddock mixer is preferred because the pressure drop forces back-mixing that homogenizes the melt more thoroughly. The trade-off is a slight increase in melt temperature that the cooling system has to remove before the die.

The MDO Stretching Section That Follows the Extruder

The machine direction orienter is where the BOPET film receives its machine-direction tensile strength and stiffness. The MDO consists of a slow roll and a fast roll running at a precisely controlled speed differential, with a heated stretching zone between them. The polymer chains align in the direction of the speed differential, which becomes the machine direction of the finished film. Typical MDO stretch ratios for packaging-grade BOPET run 4.0-4.5x, with higher ratios (up to 5.0x) reserved for film that requires higher tensile strength for lamination or metallizing.

The MDO stretch temperature has to be controlled within ±2°C across the film width to prevent uneven orientation that shows up as thickness banding. The stretch rolls have to be heated with a thermal transfer fluid system that maintains the roll surface temperature within the required tolerance. After the MDO, the film passes through a transverse direction orienter (TDO) that performs the cross-direction stretching in a separate heated oven section. The combination of MDO and TDO gives the biaxial orientation that defines BOPET as a film grade.

Resin Drying: The Pre-Stage That Determines Line Performance

PET is hygroscopic. It absorbs moisture from the atmosphere during storage and handling, and that moisture hydrolyzes the polymer chain during extrusion if it is not removed first. The hydrolysis reaction shows up in the finished film as a drop in intrinsic viscosity, which translates into reduced tensile strength, reduced impact resistance, and increased brittleness. For packaging-grade BOPET, the resin has to be dried to below 50 ppm moisture before extrusion, which requires a desiccant dryer system sized to the extruder throughput.

A 90-120 mm single screw extruder running 400-600 kg/h PET throughput needs a desiccant dryer with 1,200-2,000 kg hopper capacity and a regeneration air system that cycles the desiccant beds on a four-hour interval. The dryer has to be located close enough to the extruder feed throat that the dried resin does not re-absorb moisture during the transfer. Jurry typically specifies a gravity-feed arrangement from the dryer hopper directly into the extruder feed throat to minimize the transfer exposure. Jurry's pelletizing extrusion line package includes the dryer sizing as part of the line balance calculation.

Screw Geometry for PET Service

The standard screw geometry that works for HDPE and PP does not deliver the melt homogeneity that PET requires. PET has a narrower processing window and a sharper melt viscosity curve than polyolefins. A PET-grade screw typically runs a lower compression ratio (2.5:1 to 3.0:1 versus the 3.0:1 to 3.5:1 used for polyolefins), a longer metering section, and a dedicated mixing section at the screw tip. The metering section has to be long enough to bring the melt to a uniform temperature before the mixing section.

For BOPET film service, the screw also needs a vented section in the middle third of the barrel to remove any residual moisture or volatile contaminants that survive the dryer. The vent has to be sized to handle the expected volatile flow without flooding the vacuum system or producing a melt drool that contaminates the line. Jurry's PET-grade screws use a deep-channel vent section with a long vent opening to give the vacuum system the residence time it needs to strip volatiles from the melt before the compression and metering sections.

Melt Filtration and Gear Pump Considerations

BOPET film lines typically include a gear pump between the extruder and the die, plus a continuous melt filter that removes gel particles and contaminants that would otherwise show up in the finished film as optical defects. The gear pump decouples the extruder throughput from the die pressure, which lets the extruder run at a steady speed while the die pressure varies with the melt filter contamination level. This decoupling is critical for BOPET service because the die pressure has to remain constant to hold film thickness uniformity within ±2 percent across the roll.

The continuous melt filter runs a screen pack that catches contaminants while the melt continues to flow through the filter body. When the screen pack reaches a preset pressure differential, a portion of the screen rotates to bring a fresh screen section into the flow path while the contaminated section is cleaned or replaced. The cycle time between screen changes depends on the resin cleanliness, the throughput, and the screen mesh size. For packaging-grade BOPET film, a 40-60 mesh screen is typical, with cycle times of 8-24 hours between screen changes depending on the resin source.

Process Control and the Sensors That Drive It

A modern BOPET film line includes pressure transducers at the extruder discharge, the gear pump inlet, the gear pump outlet, the filter inlet, the filter outlet, and the die inlet. Melt temperature sensors are located at the extruder discharge, the gear pump outlet, the filter outlet, and across the die width. A throughput sensor on the gear pump or downstream of the die measures the actual line throughput in kg/h.

The control system ties these sensors together in a closed-loop architecture that holds melt pressure, melt temperature, and throughput at the setpoints that the recipe specifies. For packaging-grade BOPET, the recipe management is critical because the line runs different film grades on different days. Our engineering team has developed standardized recipe sets for the most common packaging-grade BOPET constructions including 12-micron clear film, 23-micron metallizable film, and 36-micron laminate film. Each recipe specifies the extruder temperature profile, the gear pump speed, the melt filter pressure differential setpoint, the MDO stretch ratio, and the MDO stretch temperature, and the transition between grades has to be controlled to prevent off-spec film during the transition. Jurry specifies a control system architecture that holds 50-plus recipe parameters per film grade and manages the transition between recipes with a controlled ramp that minimizes off-spec material.

Line Configuration for BOPET Versus Other Film Grades

Single screw extrusion lines are not exclusive to BOPET. CPP (cast polypropylene), BOPP (biaxially oriented polypropylene), BOPA (biaxially oriented polyamide), and various multilayer barrier film constructions all use single screw extruders of similar architecture. The differences between these film grades and BOPET show up in the screw geometry, the die design, the MDO and TDO stretching temperatures, and the downstream surface treatment.

BOPET film lines typically run narrower thickness ranges than CPP or BOPP, with the packaging-grade BOPET thickness range sitting at 8-50 micrometers. The MDO stretching temperature runs higher for BOPET (110-130°C) than for BOPP (120-140°C) or CPP (which does not stretch). The TDO stretching temperature also runs higher. Jurry's complete product line covers extruders for all these film grades. Our die head product line and vacuum calibration tank product line support the downstream sections of BOPET, BOPP, and pipe extrusion lines, with the screw geometry, barrel heating, and downstream configurations tailored to the specific film grade the converter produces.

Turkey-Specific Logistics and Installation

Shipping a single screw extruder from Jurry's Shanghai facility to a Turkish BOPET converter runs 35-45 days by sea to Istanbul or Izmir. The shipment includes the extruder, the gear pump, the melt filter, the control panel, and the spare parts package. Jurry's installation team travels to the Turkish converter site for the commissioning period, which typically runs 4-6 weeks from the arrival of the equipment through the first saleable film production.

For Turkish converters that are new to BOPET production, Jurry's commissioning team includes a process engineer who trains the converter's operators on the resin drying procedure, the extruder startup sequence, the die adjustment procedure, and the MDO/TDO stretching optimization. This commissioning support is the difference between a line that reaches its design throughput within the first three months of operation and one that spends the first six months troubleshooting the process. Converters that complete the full Jurry commissioning program typically reach 90 percent of design throughput within 90 days of first film production.

From Specification to Saleable Film: A Practical Roadmap

The right procurement sequence for a Jurry single screw extrusion line for BOPET film production in Turkey runs in five steps. First, document the target film grades and the corresponding throughput targets. Second, select the extruder size based on the throughput target plus 10-15 percent headroom for line balance. Third, specify the screw geometry for PET service with a vented barrel and a mixing section. Fourth, include the gear pump, the continuous melt filter, and the resin drying system in the line balance. Fifth, plan the commissioning support as part of the contract, with on-site process engineering for the first 4-6 weeks of operation.

That sequence gets a Turkish BOPET converter from initial order through first saleable film production in 7-9 months, including the equipment build time, the sea freight transit, the installation, and the commissioning. Across the typical 15-20 year service life of a BOPET extrusion line, the production throughput lost during commissioning is a small fraction of the total, but the difference between a 7-month commissioning and a 12-month commissioning is significant for the converter's payback period. Jurry commissioning support is structured to keep the line on the short commissioning timeline.

The Jurry engineering team supports Turkish converters throughout the warranty period and beyond with on-site service visits, remote process diagnostics, and spare parts inventory programs that match the converter production schedule. Our standard warranty on a single screw extrusion line is 18 months from commissioning or 24 months from shipment, whichever comes first. Extended warranty programs are available for converters that want to lock in maintenance cost predictability for the first five years of operation. Across our installed base in Turkey, converters under extended warranty programs report line availability above 96 percent, which is the benchmark that BOPET film converters target for capacity utilization.

Energy Consumption and the Sustainability Conversation

I have noticed that BOPET converters in Turkey are increasingly asking about the energy consumption of the extrusion line as part of their procurement decision. This is partly driven by the sustainability reporting requirements that multinational consumer brands impose on their packaging suppliers, and partly by the local electricity cost structure that makes high-consumption extrusion lines expensive to operate. Our Jurry single screw extruders for BOPET service now ship with energy-efficient drive motors, optimized barrel heating zones, and heat recovery options that reduce the line's total energy consumption by 15-25 percent compared to the previous generation of extruders we built before 2022.

The specific energy consumption (SEC) of a modern BOPET line running packaging-grade film sits in the range of 0.45-0.55 kWh per kilogram of finished film, depending on the film thickness, the line throughput, and the MDO stretch ratio. The largest energy consumers on the line are the extruder drive motor, the barrel heating zones, the MDO and TDO stretching motors, and the resin dryer. Each of these subsystems has been optimized in the current Jurry product line to keep the SEC at the low end of the range. The exact SEC for a specific line configuration can be calculated during the proposal stage using our engineering calculator, which takes the throughput target, the film thickness target, the resin type, and the dryer specification as inputs.

For converters that are pursuing ISCC PLUS certification or similar sustainability frameworks for their BOPET film production, the Jurry engineering team can document the energy consumption profile of the proposed line as part of the certification audit package. This documentation includes the rated power of each motor on the line, the average power draw under typical operating conditions, and the heat recovery options that can be specified to further reduce the line's carbon footprint. Turkish converters that supply into European consumer brand supply chains typically request this documentation as part of their line specification, and our engineering team has built it into the standard proposal format.