Innovation is essential in driving growth for the $22 billion global fabric coating market.  Applications encompass products we often take for granted including house wrap, fabric buildings, advertisement banners, aviation evacuation, waste management systems and reservoir liners. As the fabric coating segment continues to evolve, processors should be prepared to take advantage of the exciting opportunities ahead. This blog covers key machine design considerations to ensure quality products and flexibility to participate in growth.

Machine Design Considerations

First and foremost, it’s important to understand the vital role each major component in a fabric coating line plays in ensuring a positive outcome. Extrusion system design is central in terms of polymers used, outputs, coating thickness, blending and drying. Co-extrusion arrangements allow for operational flexibility, which is significant as processors seek to expand their product offering. Roll and shaft handling influences diameters and cycle times during roll changes. Web handling capabilities determine line speeds and tension ranges.

When evaluating machine design, both product structure and output requirements must be addressed. This is especially important for high-volume applications such as lumber and metal wrap, house wrap and tarpaulines, and high-value engineered textile composites such as protective garments, footwear and evacuation systems. The following are guidelines to assist in assessing existing equipment and determining upgrades to support fabric coating processes.

Extrusion System

• Polymers being used:
  • PE / PP blends vs. TPU / PA / TPO, etc.
• Extrusion system features:
  • Extruder motor and gearbox ratio with correct torque to process a wide range of polymers
  • Screw removal features to minimize downtime during screw changes
  • Filtration requirement (breaker plate, hydraulic screen changer, candle filter)
  • Resin blending; in-line gravimetric vs. off-line batch
  • Resin drying; TPU and CaCO3
  • Extruder output range (do not oversize the extruder)
  • Polymer coating thickness range (evaluate die technology)

Roll and Shaft Handling

• Cycle time and handling features:
  • No more than five changes per hour or every 12 minutes
  • Roll and shaft handing available
  • Shaft-less capabilities available
• Tension control parameters:
  • Not to exceed 10:1 ratio between core O.D. and roll diameter
• Minimum roll diameter requirement:
  • High-speed auto splicing requires 15 to 10 inches (380-500mm) per minute

Web Handling

• Process speed range:
  • Tension control not to exceed 15-20:1 turndown ratio
• Web tension factors:
  • Use the least amount of web tension to transport the web
  • Total web tension should not exceed 10:1 ratio
  • Minimum web width; concerns with bending web transport rolls
  • Two sets of load cells or web paths to assist in wide tension range
  • Web isolation units assist high process tension points
• Web treatment:
  • Adhesion between the coating/substrate and substrate/ink via corona/flame/ozone treatment or pre-heat web to activate the primer
  • Use a web cleaner to remove dirt

Davis-Standard offers process optimization action plans by doing on-site audits to affirm customer confidence. Contact marketing if you wish to set up an appointment.

Do not hesitate to contact our service team if you need assistance (844 MYDAVIS).

Stay safe and healthy! For any other questions, e-mail marketing.

Cheers,

The D-S Connect Blog Team

In our last blog, we discussed key ROI factors to consider when purchasing medical tubing equipment. In this blog, we’ll highlight best practices to achieve strict cleanroom standards with regard to equipment construction, surface treatments and extruder design features. These suggestions also promote effective and efficient disinfection and sterilization procedures, while supporting regulatory standards set forth by the ISO certification system.

Machine Construction

• Use stainless steel or rust corrosion-proof materials where coatings are not practical
• Ensure wipe-down zones are accessible
• Minimize potential collection areas for dust and debris stagnation
• Design containment options for possible fluid or residual lubricant leaks
• Employ compact designs to minimize floor space

Machine Surfaces/Treatments

• Apply water-based or epoxy-based paint in areas not constructed with rust or corrosion-resistant materials
• Polish surfaces and design with smooth, tapered or round edges for effective wipe-down
• Use stainless steel surfaces to avoid contamination in product “contact” areas; stainless steel hoods and guards included for ease of cleaning

Extruder Design Features

• Utilize direct drive systems where applicable
  • Water-cooled motors (eliminate turbulent air movement from cooling blowers)
  • Permanent magent synchronous motors (eliminate the need for gearbox/oils/mechanical drive train; less noise and more energy efficient)
• Include barrel cooling blower designs that minimize dust generation
• Route control cabling and wiring to simplify cleaning measures
• Affix polyurethane casters for ease of equipment movement and cleaning while also protecting the cleanroom floor

Have questions or comments about this blog post? Comment below! We would love to hear from you.

As always, don’t hesitate to contact our service team if you need assistance (844 MYDAVIS).

Stay safe and healthy! For any other questions, e-mail marketing at marketing@davis-standard.com.

Cheers,

The D-S Connect Blog Team

Medical tubing applications continue to evolve while also playing a vital role in the delivery of quality healthcare worldwide. As we’ve seen with COVID-19, single-use plastics have been important to every industry, but even more critical for medical applications. Tubing equipment options are vast and cost-efficiency is essential, requiring processors to plan ahead to achieve maximum ROI. In this blog, we will cover some of the ways Davis-Standard addresses important ROI factors, including:

• Product versatility
• Options for expanded capabilities
• Precise and consistent product development
• Cleanroom factors
• Space limitations

Product versatility and being able to expand capabilities is essential in a high-growth market such as medical tubing. Equipment that supports efficiency, maximum line speeds, consistent and measurable quality, and the ability to process a wide variety of materials is typically worth the investment. For medical tubing manufacturers, materials can range from FPVC, polyurethane and nylons to PEEK and FEP. Davis-Standard can customize a tubing line based on customer application. Typical line speeds range anywhere from 100 feet per minute to more than 800 feet per minute depending on the materials, tubing application and requirements. Types of tubing applications include:

• Microbore
• Alternate polymer
• Multi-lumen catheter
• Endotracheal and tracheotomy
• Radio-opaque striped
• Cannula tube
• Pipettes and
• Multi-layer tubing compositions

Choosing the right equipment from the onset, including extruder design, control systems and feedscrews, is the best way to ensure a faster ROI. Timely upgrades can also offer a cost-effective option when needed.

As with any precision process where technology advances are made on a regular basis, it’s important to have access to an R&D line. Testing new resins, making parts for proof-of-concept and conducting trials is paramount to maintaining a competitive advantage. It also helps validate processes before making equipment investments or going into large-scale production. Some companies have their own R&D capabilities. For those that do not, Davis-Standard has a dedicated medical tubing lab in a climate-controlled, cleanroom environment in their Pawcatuck, Connecticut facility. Customers can access the latest technology, extruder through downstream, to assist with R&D trails at a minimal expense.

Cleanroom factors and space limitations should also be considered to maximize ROI. Machine construction, machine surfaces and treatments, extrusion drive and control systems are all part of creating a hygienic environment. For example, Davis-Standard’s MEDD extruder is a direct drive design eliminating the need for a gearbox and oil for cleanroom applications. It also allows for flexibility to change between a ¾- and 1-inch machine sizes using the quick-change barrel feature.

For tight spaces or where coextrusion capabilities are necessary, smaller machine designs that do not sacrifice torque and processing versatility are the way to go. In this area, Davis-Standard’s HPE models provide high-torque and direct couple motors in a compact design. The HPE-A model has height adjustments and swivels and tilts on a column to be positioned at any angle, while the HPE-H is a fixed height horizontal extruder.

For resins that are especially challenging to process, Davis-Standard can integrate a melt pump into the control system to be coordinated with extruder pressure and speed, which provides a more stable output. In some cases, melt pumps can provide greater process control and can be sold and integrated on a line new or added at a later date if the customer changes materials or adds new material to be processed.

We hope you enjoyed learning how to maximize your ROI. If you have any comments or questions regarding this blog, comment below. If you would like to learn more about Davis-Standard’s medical tubing solutions, please visit https://davis-standard.com/extrusion_system/pipe-profile-and-tubing/

Stay tuned for the next blog, Necessities to Keep the Clean Room “Clean”.

As always, don’t hesitate to contact our service team if you need assistance (844 MYDAVIS). Stay safe and healthy!

Cheers,

The D-S Connect Blog Team

In this third blog post of our blown film series, Laura Martin, Director of Blown Film Technology at Brampton Engineering, discusses different blown film dies offered by Davis Standard and Brampton Engineering.

The coextrusion die is the heart of a multi-layer blown film system, where the layers of extruded polymers are brought together. After the die, the layers are stretched into the final film structure. Davis-Standard offers numerous die designs to ensure your blown film line has the die type best suited for your process. This could be a high-output Vertex, flexible Optiflow, extremely large Centrex, or highly versatile SCD® Streamlined Coextrusion Die. It could also be a dual, tri or quad die system.

To select a die style, first consider the number of layers and required die lip size. The minimum number of layers is determined by the most complex film structures to be made. Remember, you can always make a three-material film with a seven-layer die. The die lip size is a function of the film layflat width and the suitable BUR (blow-up ratio) range for the film structure and air ring. There is a maximum and minimum BUR, so it’s important not to choose a die lip that is too large or too small for the range of layflat widths required. Once you know the number of layers and the die lip diameter, consult the chart shown here.

For monolayer to seven layers between 6 and 24 inches, the Vertex side-fed cylindrical die is a workhorse. This die offers high outputs by virtue of the large center opening that accommodates an insulated IBC to direct cool air to the inside of the bubble.

The center-fed design of the Optiflow and Centrex dies minimizes the flow path prior to the spirals, reducing resin degradation in larger dies with many concentric cylindrical layers. As long as the lip size is 20 inches or more, the IBC capacity is quite high. Optiflow is offered with one to nine layers and with die lips up to 40-inches. Centrex is designed for large agricultural applications requiring die lips up to 100 inches and with three to seven layers.

The Brampton Engineering SCD^® Streamlined Coextrusion Die was the first pancake-style die. Introduced in 1990, it is side-fed with a large opening for IBC (like the Vertex), but the layers are stacked horizontally instead of nested concentrically. This design is advantageous because every layer has the same flow path length from entry to the co-extrusion chamber, and adding more layers is simply a matter of stacking more modules. Dies up to 13 layers have been run successfully. Layers can be added to existing dies to upgrade capabilities while protecting your existing die investment.

There are four types of SCD modules, most of which allow each die module to be set at the optimal temperature for the resin in that layer. This gives blown film processers a much wider process window to make complex coextruded films successfully. This is especially important for films incorporating nylon layers, as running these in a cylindrical die requires the entire die to be heated to the temperature of the nylon.

No matter the number of layers, the type of resins, output requirements or application size, Davis-Standard has a die platform for your process. This includes rotating or oscillating monodies and co-extrusion dies up to thirteen layers, and with die lip diameters from four to 100 inches. We can also upgrade the die technology on your existing lines regardless of the original manufacturer.

In our next blog post, we’ll discuss what to look for in an air ring.

Do you have questions regarding this blog? Comment below!

Anything else we can help you with, please contact marketing or visit the Brampton Engineering blown film page for more info.

Cheers,

The D-S Connect Blog Team

In the last blog, we provided tips to help establish a baseline for application requirements and provided information on coater selection and coating formulations. In this blog, we’ll take that a step further by looking at the types of liquid coating substrates and characteristics, substrate surface tension/corona treatment guidelines and dryer selection.

What types of substrates are you coating? These can include paper, film, tissue, metal, foam and non-wovens. What are the characteristics of those substrates? Factors to consider include absorbency, surface tension, strength, smoothness, caliper, softening temperature and bend radius. This helps us determine corona treatment guidelines. Here is an example showing the substrate surface tension for different materials.

Dryer selection is the next aspect of building your ideal liquid coating line. When choosing a dryer design, evaluate the following:

• Type of substrate
• Coating formulation
• Evaporation rate
• Solvent or water-based
• Temperature limitations
• Cure and dwell requirements
• Nozzle design
• Floatation or roll support
• Quiet zone
• Cooling zone

The dryer design determines the length for silicone curing. The heat-up is based on the amount of energy required to heat the web to the cure temperature of the silicone. The length can be shortened if the temperature is increased, but web temperature will also increase. Excessive web temperature may cause damage to the substrate and may also cause silicone dusting. Here is a helpful equation to help avoid negative results:

Dryer length for silicone curing = length of dwell + heat-up time

For adhesive drying, there are three primary stages to ensure quality results. These include:

Stage 1: Heat-up to the point of evaporation; slow heat-up rate to prevent skinning

Stage 2: Drying; avoid boiling of liquid in the adhesive layer

Stage 3: Final moisture removal; avoid blistering of the adhesive layer

We hope this blog assists you in improving your liquid coating processes. Have questions about this blog post? Comment below.

For any other questions or inquires, please e-mail marketing at marketing@davis-standard.com.

Stay safe and healthy!

Cheers,

The D-S Connect Blog Team

The first step in building a world-class liquid coating line is properly defining the application. Product development in flexible packaging, labels, tapes, window film and paint protection present challenges to both converters and machinery manufacturers. Whether considering a new coating line or running new applications on an existing line, it’s important to evaluate various parameters to optimize production. This first blog will cover key questions to help establish a baseline as well as information on coater selection and coating formulations.

Key Questions:

1. What substrates are to be coated?
2. In what order are the webs coated?
3. What are the limitations of the web temperature and tension?
4. What are the parameters for web handling, tension, roll diameters and weight?
5. What are the surface treatment levels and requirements (i.e. corona, flame)
6. What are the formulations?
7. How do the formulations get applied to the web?
8. How do you dry the formulation?
9. What are the safety and design parameters of the formulation?

Here is a generic product structure defining the order in which the product is produced.

After answering those questions, take a look at coater selection.

Parameters considered here include:

• Line speed
• Substrates
• Coating formulation
• Finished criteria
• End-use
• And appearance

You’ll also want to consider your geographic location, local regulations and workforce capabilities.

Basic coater types include:

• Gravure
• Reverse roll
• Slot die
• Rod coater
• Smooth roll
• Air-knife
• Curtain coater
• Dip and squeeze
• Knife-over-roll
• Hot melt
• And other variations

Evaluating coating formulations comes next.

Properties for assessment include:

• Functionality
• Coat weight
• Wet thickness
• Solids
• Viscosity
• Shear stability
• Percentage of each component
• Percentage of coverage
• pH, whether it is solvent or water-based
• And application speed and temperature

In the next blog, we will take a look at the types of liquid coating substrates and characteristics, substrate surface tension/corona treatment guidelines and dryer selection.

Do you have questions or comments about this blog post? We’re happy to hear from you – comment below.

If you have any questions regarding our liquid coating machines, please visit: https://davis-standard.com/converting_system/liquid-coating/ or e-mail marketing at marketing@davis-standard.com.

Cheers,

The D-S Connect Blog Team

The COVID-19 pandemic has certainly put a spotlight on the importance of hygienic and protective films. These films have become essential to limiting the spread of the virus and in many cases, saving lives. The added demand requires that global processors keep their cast film operations running as efficiently as possible. Producing single and multi-layer cast film structures with excellent melt quality, high tensile strength and reliable barrier properties leave little room for error. To support product consistency, limited waste and reduced downtime, we’ve put together a list of 10 common cast film issues and how to troubleshoot them.

Gels, Un-melts, Charred Polymer: Overheated/degraded polymer, poor melting of polymer, foreign impurities in resin stream,

• Reduce melt temperature or if un-melts, increase extruder barrel temperatures
• Check thermocouple installation and accurate heater control
• Worn or Damaged Extruder Screw – Inspect & measure screw dimensions
• Worn or Damaged Extruder Barrel – Inspect & measure barrel ID
• Check resins and material handling for foreign contamination

Melt Fracture “Sharkskin”: Low melt temperature or die gap too narrow

• Raise melt temperature via heater setpoints
• Activate die lip heaters if equipped
• Increase die gap

Poor or Non-uniform Optical Clarity: Indicates inadequate extrudate quenching

• Extrudate melt temperature too low, raise melt temperature
• Cast roll quenching temperature too high, reduce cooling water temperature
• Needs improved film to cast roll contact, Increase vacuum box, increase air knife
• Co-extrusion interfacial instabilities – adjust layer thicknesses via extruder outputs

Voids, or Gray Streaks: Indicates potential moisture in resin stream

• Identify the cause of moisture in the material handling system
• Water condensation on extruder feed section can occur (hot, humid environment)
• Ensure raw materials are dry

Milky areas: Indicates contamination by an incompatible polymer

• Identify where the contamination is occurring and eliminate it
• Clean/purge the resin material handling system, hopper and dryer
• Purge the extruder with an un-blended neat base resin
• Disassemble and clean the extruder barrel, feedscrew and die (if needed)

Discoloration: Indicates the extrudate melt temperature is too high

• Lower the barrel temperature to recommended levels

Poor pigment dispersion: Indicates poor mixing or uneven melting

• Residence time improper for accurate mixing, Increase back pressure/residence time
• Melt temperature improper for accurate mixing, Lower temperature to increase shear
• Inspect blending dosing unit for accurate & consistent color masterbatch feeding
• Evaluate the feedscrew design; change or modify if needed
• Evaluate the resin rheology compatibility

Gauge Bands, Die Lines, Film Lines: Indicates contamination at die lips, die adjustment issues, & vacuum box adjustments

• Die lip is dirty – Clean (shim) die lips at localized lines
• Die manifold is dirty – Split, clean, and inspect die
• Die lip out of adjustment – check die gap and re-gap
• Inspect vacuum box for leaks and localized high air velocities, re-adjust
• Inspect air knife for localized high or low air velocities, clean & adjust air knife gap

Plate-out / Chill roll deposits: High entrapped air between chill roll and film, poor nip contact with plate-out roll

• Inspect plate-roll surface condition, replace if poor
• Inspect for even nip contact force across plate-out roll & cast roll
• Increase plate-out roll contact nip pressure
• Reducing plate-out -Increase vacuum, reduce melt temperature, increase cast roll temperature, reduce resin additives (slip, anti-blocking)

Film blocking: Indicates the winding tension or corona treatment level is too high

• Reduce winding tension
• Lower treatment levels
• Inadequate film cooling/quenching, reduce cooling roll temps &/or reduce line-speed
• Inadequate levels of anti-block additive, increase anti-block

Do you have questions or comments about this post? Drop a line below – we’re happy to hear from you!

If you need assistance on your cast film line, don’t hesitate to contact our service team via our website or by calling 844-MYDAVIS.

Stay safe and healthy!

Any other questions, e-mail marketing at marketing@davis-standard.com.

Cheers,

The D-S Connect Blog Team

Building upon our last wire and cable blog on capstan technology, we’ll cover the most significant reel handling components of a wire and cable line – takeups and payoffs. These machines are used for winding and unwinding wire and cable for SZ stranding, secondary coating, sheathing and insulation. Davis-Standard and Maillefer, a Davis-Standard company, offer several models of takeups and payoffs to support wire and cable applications including fiber optic, low-voltage and telecom cable, building wire, MV, HV and EHV wire. Machine selection depends on factors such as reel weight, flange diameter, cable diameter, automation features and line speed requirements. Reel handling equipment also includes dancers, cutters and optical traverse control, which can be incorporated into a reel handling package.

Following is a brief summary of the different types of takeups and payoffs and typical applications:

Dual reel take-ups: This design offers changeover reliability for any application at top-line speeds. These speeds can be upward of  9,500 feet (2,896 meters) per minute and for reels up to 50 inches (1,270mm) in diameter and 5,000 pounds. Operation can be fully automatic with various reel handling options, or semi-automatic, requiring tending only for loading and unloading of reels. These machines can work independently from line controls for easy adaptation and installation.

Applications: Automotive wire, building wire, low-voltage wire

Flyer pay-offs: Excellent for high-speed and uninterrupted continuous wire unwinding with constant tension required for cable insulation. These machines are comprised of two conical fly-off cones, two-reel lifting carts (displaceable over rails), one pair of fly-off flanges and one pair of reel shaft adapters.

Floor traversing take-ups and pay-offs: These shaftless models offer space-saving, low profile construction to support heavy loads and a broad reel range due to the capacity to extend production lengths. These machines can be equipped with low, medium and high tension dancers, with mechanical or electrical braking and reel engagement, and various options for reel loading and unloading.

Moveable arm take-ups and pay-offs: Also referred to as PORA/TURA take-ups and pay-offs, these models are shaftless in design with pneumatic reel lift or dual-electric screw jack actuators on 84 to 120-inch (2,100 to 3,000mm) units. Larger units use independent arm movement for reel arrangement while single actuation capabilities are supplied on models 36 inches and smaller.

Applications: Low voltage wire, MV, HV and EHV

Portal take-ups and pay-offs: These machines are ideal for heavy loads and a wide reel range. They are built with a shaftless roll-thru design that allows reel loading from the rear or front of the machine. The frame can be supplied in single, double or triple widths to support flange diameters of 42 to 144 inches (1,066 to 3,600mm), weighing up to 60,000 pounds. All functions such as reel rotation, traversing, pintle movements and auto reel handling are activated and controlled from a hanging control panel.

Applications: Building wire, fiber optic cable, low voltage wire, MV, HV and EHV

Have a question regarding this blog? Comments below! We would love to hear from you.

E-mail marketing at marketing@davis-standard.com to let us know how we can help you evaluate extrusion line components or seek to upgrade a current line.

Cheers,

The D-S Connect Blog Team

Davis-Standard has been a leader in wire and cable extrusion since the company sold its first extruder in 1948. Seventy-two years later, Davis-Standard’s leadership in the wire and cable marketplace continues with wireline components and complete systems to support applications ranging from aerial cable, building wire, coaxial and composite cable, video pair cable, CATV, THHN and THWN wire among others. This includes an impressive equipment line-up from Maillefer, a Davis-Standard company.

Wire and cable systems involve many components including payoffs and take-ups, dancers and accumulators and capstans to ensure consistency, quality and efficiency. Knowing which type is needed based on application is essential. In this blog, we’ll focus on the component that ensures line speed stability – the capstan. There are three main types of capstans – belted caterpillar, belt-wrap and drum. Following is a summary of each and examples of applications.

Belted caterpillar capstans are generally used for heavy pulling jobs, larger diameter wires, and for slower production speeds. These machines are engineered for longer runs and high pulling forces. Stable line speed minimizes cable diameter variations. Applications include low-voltage cable, MV, HV & EHV, insulation and sheathing.

These capstans are often used in pairs, and in some cases, there may be more than two on a line. Based on application, this could include a “pullout” capstan to pull the wire and maintain wire tension; or a “metering” capstan to hold back on the wire, allowing the pullout capstan to pull the wire at a specific speed. Belted capstans have a relatively soft belt with good gripping properties. Tracks are moveable and typically actuated by air cylinder in order to squeeze the cable. Squeeze strength and track length determine how much wire tension the belted capstan can pull. New designs incorporate individual cylinders/support plates to allow the machine to better handle diameter changes on the fly.

Belt wrap capstans are the most versatile enabling a range of tensions and speed variations. These machines support inline processes for optical fiber through larger wire and cable. Both horizontal and vertical types are available. Applications include low voltage as well as medium and high voltage CV lines. The use of this capstan is particularly useful in applications where there are horizontal accumulators in the line.

These capstans use pneumatic cylinders that press the belt against the drive wheel, and the drive wheel provides the pulling force. The pressing force is adjusted from the control panel where the pressure gauges are located. The belt is opened and closed from the same panel.

Drum capstans are typically used on small wire for applications requiring high speeds, precision (reduced vibration) and accurate tensions. They are often integrated into trough capstans. Multiple passes can be used around the drums to multiply the contact length for improved friction and precision control. Applications include data and aerospace cables.

Davis-Standard and Maillefer have an extensive inventory of capstans to best suite your wire and cable operation. Let us know how we can help you as you evaluate extrusion line components or seek to upgrade a current line.

Do you have questions or comments about this post? We would love to hear from you! Please comment below or email marketing at marketing@davis-standard.com.

Cheers,

The D-S Connect Blog Team

In this second blog post of our blown film series, Laura Martin, Director of Blown Film Technology at Brampton Engineering, explains the basic characteristics of key resins used in blown film structures. 

Multilayer films require various resins to achieve specific properties in the final structure and also to improve processability during film production and converting. Choosing these resin grades is also about balancing raw material cost, typically accounting for 80 percent of the overall cost of making film! Different resin families and grades enable functions such as barrier, sealing, adhesion, stiffness, toughness, formability, and simply making up the bulk of film thickness.

Polyethylene (PE)

All types of PE are chemically identical: a wide range of processing and product properties results from different forms of branching, crystallinity levels and densities.

• PE is the basis of most coextruded blown film structures
• Used in sealant layers and in-forming film bulk
• Often blended together to optimize property profiles, processability and cost
• Excellent chemical resistance

High-density PE (HDPE)

This resin produces a stiffer barrier film that offers moisture protection to keep products dry and fresh.

• Highest density of the PE types due to lack of branching and high crystallinity levels – packs well in a 3-D array
• ρ = 0.93-0.97 g/cc
• Process temperature is roughly 220°C
• Used in bulk or outside layers
• Good water vapor barrier – protects EVOH
• Moderate stiffness and toughness
• More haze (due to crystallinity)

Low-Density PE (LDPE)

For clear, abuse-resistant films, which are easier to process and use on packaging lines.

• p = 0.91-0.93 g/cc due to high degree of long-chain branching and low crystallinity (doesn’t pack well)
• Process temperature is roughly 210°C
• Used in bulk or sealant layers
• Superior clarity, toughness, dart impact strength
• Good seal and hot tack strength, low seal initiation T
• Long branches improve melt strength in blends

Linear Low-Density PE (LLDPE)

These are the lowest cost grades with a good balance of properties but can be difficult to process without the right equipment.

• p = 0.91-0.94 g/cc with many short branches and low crystallinity levels
• Process temperature is roughly 220°C
• Used in bulk and sealant layers
• High strength, good low-temperature properties, low shrink temperature
• More difficult to process (low shear-thinning)

Metallocene PE (mLLDPE)

Similar to LLDPE, but made via a different catalyst chemistry (metallocene), resulting in more precise chain lengths and branching. Resin producers can  fine-tune grades for specific applications, and new tailored grades are now available for niche needs. For the most common mLLDPE grades:

• Process temperature is roughly 225°C
• Improves properties over similar LLDPE
• Improves optics (clarity, gloss)
• Better sealing properties
• Can be more difficult to process (low shear-thinning)

Polypropylene (PP)

Excellent clarity and moisture barrier, with better heat resistance than PE – often used on the outside of a barrier film for liquids, to permit higher sealing bar temperatures and better seals.

• p = 0.90-0.91 g/cc
• Process temperature is roughly 230°C
• Used in bulk or outside layers
• Good water vapor barrier, with much better optical appearance than PE

Polyamide Family – Nylons (PA)

Just like polyethylenes, nylons can be designed to bring a wide range of properties to films. PAs are used for robust, thermoformable barrier films with good stiffness and puncture resistance. New terpolymer grades are available to solve processing issues that can arise due to high density and low melt strength.

• p = 1.12-1.15 g/cc
• Barrier for oxygen, oil and flavors
• Stiff, strong, tough, formable, seal bar release
• PA6 – better O₂ barrier, poorer H₂O barrier, 250°C
• PA6/66 – clearer, better physical properties, 240°C
• Amorphous PA – blend <20% with PA6 or PA6/66 for better clarity and moisture resistance (retain barrier)

Ethylene Vinyl Alcohol Family (EVOH)

Excellent barrier to oxygen, oils, and aromas – if kept dry.

• Copolymers with varying Vinyl Alcohol content to adjust barrier properties
• Process temperature is roughly 220°C
• Always used in core layers
• Adheres to PA and tie resins, but not PE
• Minimum five layers: PE/tie/EVOH/tie/PE
• Often coextruded between two layers of PA: PE/tie/PA/EVOH/PA/tie/PE

Ethylene Vinyl Acetate (EVA)

This sticky copolymer resin with adjustable properties is usually coextruded as the inner (sealant) or outer layer.

• Physical properties vary with VA content
• Process temperature is roughly 190-200°C
• High clarity, flexibility, low seal initiation temperature, good adhesion, impact and puncture resistance

Tie Layers

Tie layers enable chemically dissimilar materials to be “tied” together.

• Many different modified polymers or blends can function as tie layers between resins which do not adhere to each other
• Must have either backbone or functional groups which are compatible with each resin
• Can be preformulated or supplied as concentrates to be blended with a primary resin

Designing a coextruded film with the right balance of properties for the final application, the converting process, and the blown film process can be a tricky juggling act that is easier with collaboration and the right equipment. Regardless of the number of layers, resins, outputs, or size your application requires, Davis-Standard has the right die platform to best suit your processing needs – which is the topic of the next post in the Blown Film Series.

Do you have questions or comments about this post? We would love to hear from you! Comments welcome below.

For blown film resin and equipment suggestions, do not hesitate to contact us and we’ll put you in touch with the right person based on application. E-mail marketing at marketing@davis-standard.com.

Cheers,

The D-S Connect Blog Team