When approaching a design problem, automotive engineers generally have three things on their wish list for a solution. They want to find:
- The right material
- The right price
- The right quantity
It can take a while to pull this off. Sorting through the vast catalog of automotive films in search of the ideal material to meet your design specs (at a cost-effective price and in an accessible volume) is a daunting task.
Modern automotive films are also versatile materials. There are specialized options for purposes throughout the vehicle—on window sashes, as emblems or dashboard markings, inside doors and hatches, protecting body fascia, as structural adhesives, and in the engine compartment. But as synthetic films evolve, their material advantages have spread to overlap across multiple purposes. So which one should you use?
Table of Contents:
- TEMPERATURE — “It needs to survive extreme temperatures.”
- VIBRATIONS — “Vibrations between surfaces could create rattles and squeaks.”
- DISSIMILAR MATERIALS — “The two substrates I’m bonding are dissimilar.”
- CURVATURE — “The surface is curved, awkward, or irregular.”
- STRUCTURAL BONDING — “Holes for rivets would weaken the substrate and increase vehicle weight.”
- AESTHETICS — “It has to match the beauty of a painted element.”
- CHEMICAL RESISTANCE — “Harsh chemicals will contact the surface.”
- DURABILITY — “The surface will suffer impacts and abrasions.”
- LONGEVITY — “It has to last the life of the vehicle.”
- RESIDUE — “There can’t be any residue when it’s removed.”
- SEALING — “It needs to seal out moisture, sound, or light.”
- OFFGASSING — “The substrate offgasses.”
- BUDGET — “I’m on a tight budget.”
- VOLUME — “I have strict, but challenging, volume requirements.”
What’s Your Design Problem?
Here’s a rundown of the most common design problems faced by engineers, and how to find the right automotive films for the job:
TEMPERATURE — “It needs to survive extreme temperatures.”
If the temperature is your problem, you’re likely hunting for a heat-resistant film to label under-the-hood components or provide safety warnings in the engine compartment. Thermally resilient automotive films are also ideal as wire harness tapes—they protect electrical wiring by keeping it tucked up and away from the hot engine block, but are cheaper and more convenient than heavy mechanical fasteners.
Consider high-performance acrylic adhesive layers that can hold bonds on plastics and metals in blazing heat. As for the backing, polyester and heat-stabilized PVC films are popular for their tolerance of extreme temperatures—even as they swing quickly between icy and sweltering temperatures while your engine heats up in the winter. Polyester usually has an edge in heat resistance, but it’s hard to knock PVC’s general durability.
VIBRATIONS — “Vibrations between surfaces could create rattles and squeaks.”
Polyethylene foam anti-vibration tapes are the perfect solution to troublesome road vibrations. They absorb shocks and diffuse the force of vibrations to eliminate any risk of buzzing and rattling—which is very common with the many small plastic components in the cabin, on the dash, and as decorative trims. Foams reshape themselves to cushion uneven joins between surfaces so that the bonds become consistently flush.
Also, consider the rigidity gains of pressure-sensitive tapes when bonding parts that would otherwise be held together with bolts or rivets. A more rigid vehicle that takes advantage of consistent, full-surface bonds (and vibration cushioning tapes in doors/hatches) will score more favorably in noise vibration harshness (NVM) ratings.
DISSIMILAR MATERIALS — “The two substrates I’m bonding are dissimilar.”
One of the significant advantages that double-sided films and tapes have over liquid adhesives is that they can use multiple layers—they don’t need to be universal. Instead, the core can be fitted with a unique adhesive on each side that is matched to the substrates you’re bonding.
You may have two substrates with very different thermal expansion properties, like polyvinyl chloride (PVC) and glass-reinforced polycarbonate. In these cases, double-sided foam tape can offer the viscoelastic properties you need to flex as the temperature fluctuates. Because plastics and metals respond differently to heat, plastic emblems and trim on exterior panels commonly rely on acrylic foam tape.
Or, you might have a mixture of high and low surface tension materials, or the need to prevent galvanic corrosion (such as when bonding steel and aluminum). Adhesive tapes form a barrier between the two substrates (and the two adhesives) to make these bonds possible.
CURVATURE — “The surface is curved, awkward, or irregular.”
Thicker automotive films are tougher but generally offer less surface followability. Polyethylene foam bases can be an exception, as they have the flexibility to conform to unique surfaces.
For exterior uses, you’ll often want to rely on thin-gauge films such as polyurethane-based “clear bra” films or highly flexible PVC and fluoropolymer-laminated marking films. These see use as invisible (or decorative) sealing and protection over body panels. PVC-based paint replacement films can even conform to the awkward and narrow shapes required to black-out door pillars and window sashes.
STRUCTURAL BONDING — “Holes for rivets would weaken the substrate and increase vehicle weight.”
Strong permanent adhesives (such as cyanoacrylates and urethanes) can provide rigidity, structural bonding strength, and negligible weight compared to heavy mechanical fasteners. Rivets also puncture the substrate, which invites corrosion, moisture, potential for squeaks/rattles, and weakens the integrity of the panel.
Today’s automotive adhesives have the strength to outperform metal fasteners. This has led to adhesive films and tapes replacing mechanical fasteners at a rapid rate. Automotive-grade, pressure-sensitive double-sided tapes also see applications in windshield and rear view mirror components where fasteners are not an option.
AESTHETICS — “It has to match the beauty of a painted element.”
Pressure-sensitive PVC films have become the gold standard for attractive paint replacement films with their durability, ease of application, and sizable cost savings over traditional paint procedures. Used as “blackout tapes” on window sashes and pillars, they can imitate black paint while also providing a differentiation opportunity—a matte or glossy finish to match or contrast with the body paint.
Paint for such small elements is not expensive on its own, but the tricky and inefficient process of painting and curing awkward elements has made automotive film a reliable alternative that doesn’t sacrifice on beauty.
All sorts of marking films are also out there on the market to protect the paint job or provide additional decorative elements. It’s possible for films to be nearly invisible over the paint with high-clarity acrylic, polyethylene, or urethane polymers and ionomers.
CHEMICAL RESISTANCE — “Harsh chemicals will contact the surface.”
Engine compartments and gas covers deal with this issue the most (oil, gasoline, coolant, antifreeze, etc.), but any part of the vehicle that is at risk of collecting road salt, washer fluids, grease, or grime may need some form of chemical resistance. Labels, paint replacement films, and protection films alike all need to stand up to unpredictable exposures over years of use.
Fortunately, the polymers used in automotive films are far more resistant to corrosive substances than the metals in the car. The majority of automotive tape and film backings use highly chemical-resistant materials, such as:
- Polyethylene terephthalate (PET, or “polyester”)
- Polyvinyl chloride (PVC)
- Polytetrafluoroethylene (PTFE)
- Acrylic (a thermoplastic resin noted for stability in UV radiation)
DURABILITY — “The surface will suffer impacts and abrasions.”
This is where urethane-coated anti-chipping tapes and films show their real value. Modern anti-chipping tapes offer superior weatherability, transparency, and security from the chips and rust that result from kicked-up road debris. They can apply invisibly over paint and will not yellow over time in the harsh sun (a challenge with earlier generations).
Also, consider the newest ionomer pressure-sensitive films for their advancements in shock absorption. These adhesives make excellent door-and-hatch cushioning films at better cost performance than older urethane films.
LONGEVITY — “It has to last the life of the vehicle.”
Contrary to the “temporary” stigma given to tape, modern automotive adhesives can outlast mechanical fasteners that corrode or loosen over time. The most significant advantage is that automotive tapes line the entire contact surface between the substrates, while fasteners have finite points of reinforcement. This makes for a more rigid bond and prevents squeaks or buckling around fastener-points.
Even small details like emblems and logos are more secure with adhesive films than with fasteners, which often result in rattling due to road vibrations. Foam anti-vibration tapes solve this problem and remain safely adhered over the full operational life of the vehicle.
RESIDUE — “There can’t be any residue when it’s removed.”
Not all films are meant to adhere permanently. Temporary films and tapes are often used to protect components during packaging, shipping, and assembly, only to be removed on the lot when the vehicle is ready to sell. For example, you might use them to keep flooring materials clean or safeguard the luster and flawless finish of aluminum wheels. Wheel films also create a barrier that prevents corrosive moisture or substances from getting to brake discs and rotors.
These transparent automotive films are typically made from polyethylene and fitted with an easily peelable adhesive layer that is specially formulated to leave nothing behind after removal. This doesn’t mean the adhesive needs to lack strength or longevity—protection films can remain reliably adhered for months if need be without slipping or breaking the protective seal.
SEALING — “It needs to seal out moisture, sound, or light.”
Weather stripping often adheres with reliable acrylic or polyethylene foam tapes. Closed-cell foams like these don’t permit moisture to pass through and conform to uneven surfaces to create a tight seal. These materials are ideal for gasketing or lining hatches or components that need to open easily but close securely. The previously mentioned wheel films are a temporary option that can be counted on to seal out moisture that could corrode components before the sale.
Urethane foams are less suited to moisture sealing, due to their open-cell nature, but they are excellent for dampening sound. You can also consider using foam anti-vibration tapes to enhance the seal of openings that would otherwise allow residual noise from wind and engine sounds into the vehicle’s cabin.
Vinyl-based blackout tapes are heat and UV resistant, which has made them popular for covering gaps and lining edges to prevent sunlight from showing through in areas around the windows and dash.
OFFGASSING — “The substrate offgasses.”
The Low Surface Energy (LSE) plastics that are becoming more common in today’s automobiles can pose more problems than simply being difficult to adhere to. Some thermoplastics are known to create bubbles or blisters under films and labels by outgassing over time.
This calls for blister-free films and bumper stripes that allow the out-gasses to pass through. Film laminates made with cellular polymers can be applied over a variety of surface bases so that your labels stay smooth and flat—even on injection-molded plastics and polycarbonate.
BUDGET — “I’m on a tight budget.”
Budget issues are one of the most common obstacles to meeting spec. You have a maximum total number to work with, and you might have an idea of how much you can allocate towards adhesives even before the RFQ stage. As you evaluate your options for a cost-efficient solution that still meets the necessary standards for your design, there are a few strategies you can use:
- Try to spare yourself any extra features beyond exactly what you need your automotive film or adhesive to do. As with #2 in this list of tips for meeting OEM price points, a specialized product with limited useful properties may be more cost efficient than a universal solution.
- Select the material you want for a backing, but assess whether it can still meet spec with a thinner gauge or more economical adhesive layer. There’s no need to overdo it on strength for a component that won’t see heavy impacts or exterior exposure.
- Buy in bulk.
- Don’t forget that films can create savings by protecting the quality of other components that need to meet spec all the way from line to lot.
- Consult with a supplier to see if there is a lower-priced alternative that didn’t come up in your initial research as you try to meet budget and spec.
VOLUME — “I have strict, but challenging, volume requirements.”
If your concern is that you have a volume requirement that is too limited (perhaps for a prototype) to be appealing, or too massive for most suppliers to meet weekly, monthly, or annual usage, it’s crucial to meet and discuss the specifics of your project with a supplier.
Many suppliers of automotive films and tapes are motivated to work out a solution and earn your business. They may be able to collaborate with another supply chain tier to convert materials that will increase their capacity and meet your demand.