High Performance Polyurethane Foam Tapes

I always feel a little sorry for polyurethane foam tapes. Why? They tend to get lost in the shuffle between the acrylic foam tapes on the one side, and the lower cost polyolefin foam tapes on the other.

Despite this, polyurethane foam tapes have some formidable physical properties and have an excellent performance to cost relationship.

What are Polyurethane Foam Tapes?

Polyurethane foam is produced by reacting polyols with diisocyanates to create highly resilient foams that we use every day in mattresses, car seats, and foam for tapes and gaskets. Various additives are incorporated to help tailor the urethane for particular applications.

These foams are coated acrylic adhesive systems that yield a high performance bonding tape that can:

  • Dissipate energy and stresses along the entire bond line
  • Resist weather, extreme temperatures, UV light, and fungus

One of the premier manufacturers of polyurethane foam tapes is Saint Gobain. They produce an excellent range that includes the V2800, V4600, and V8800 for severe exterior applications, V1300 for interior applications, the V900 series for electronic applications needing a UL rating and the Z500 series for automotive applications.


V2800 Series Physical Properties


Pay particular attention to the high dynamic shear and dynamic tensile values. These high values translate well into bonding tape applications for roof bows and panel stiffeners in truck and utility trailers and RVs,

  Other applications for polyurethane foam tapes include:

  • Body side molding
  • Wheel weight attachment
  • Composite panel bonding
  • Emblems and nameplate attachment
  • Sign framing
  • Wheel well and door edge moldings
  • Bumper trim and inserts
  • Rocker panels

Polyurethane foam bonding tapes might lack the popularity of the acrylic foams and polyolefins, but they perform reliably in heavy duty applications every day. They have an excellent cost benefit balance and should be considered for your next high performance assembly application. Want to know more about polyurethane foam tapes? Contact Tom Brown, Inc. today!

Foam Tapes for Muntin Bar Attachment

Simulated divided lites are a popular design option for residential and even light commercial windows. The design intent is to create the look of individual panes of glass by applying muntin bars or grilles internally (called “G-B-G” for glass/bar/glass) or externally by using foam bonding tapes. Muntin bars attached with high performance tapes having a pleasing visual appearance, have secure bonds if installed correctly, and save production time.

Types of Foam Tapes for Muntin Bar Attachment

The two most common types of foam tape used for bar attachment are acrylics and polyolefins.

Acrylic Tapes

Acrylic foams include the popular VHB brand from 3M and the Norbond brand from Saint Gobain. Other suppliers of high quality acrylic foam tapes include the AS series from Scapa, the ACX series from Tesa, and the SFB series from Avery Dennsion.

These tapes can be monolithic meaning the adhesive and foam core are extruded in simultaneously in a single layer or they can be multi-layer where an extruded acrylic foam core is coated with the acrylic adhesive system. In either case, these tapes exhibit excellent viscoelastic behavior. This means the “viscous” behavior allows the tape to absorb and damp energy that occur from sudden wind gusts or other forces while the elastic behavior allows the tape to recover (think of stretching a rubber band and then letting it come back to its normal shape).

 

Saint Gobain A7300 Series Performance Data

Polyolefin Foam Tapes

Polyolefin foam tapes are made from a foam core extruded from polyethylene that is often modified with varying amounts of EVA and polypropylene. Additional coatings can be extruded onto the foam core to create a very smooth surface onto which the acrylic adhesive will be coated. High quality polyolefin foams are produced by Adhesives Research as well as Berry Plastics, Adhesive Applications, and others.

The polyolefin foams don’t have the same viscoelastic behavior of the acrylic foam tapes but they exhibit very good dynamic shear and tensile (T block) values along with a very favorable price that can make them worth considering especially for lighter weight muntin bars made from cellular PVC and other lightweight materials.

Adhesives Research 8645 Muntin Tape Performance Data

 

Foam Core Stress /Strain Capabilities

The chart below demonstrates the capabilities of each basic type of foam core and how they differ.

 

Want to know more about muntin bar tapes? Contact Tom Brown, Inc. today for samples, technical data, or to discuss your application further.

Understanding the Effect of Coefficient of Thermal Expansion on Tape Products

The coefficient of thermal expansion is used to understand the rate at which a certain material expand as a function of temperature. This understanding is very important when designing adhesive bonded joints to determine if failure by thermal stresses might occur.

Definition

The coefficient of thermal expansion (CTE) is defined as the change in length or volume of a material for a unit change in temperature. The coefficient is reported as the linear thermal expansion in inches or millimeters per degree Fahrenheit or Celsius.


Why is this Important?

One of the major benefits of tape products is their ability to bond dissimilar materials. It is quite common for plastics to have 8-10 times the thermal expansion of metals.

These thermal stresses become important to understand when bonding glass to metals especially in architectural applications where failures can be extremely expensive or even catastrophic.

Design engineers can calculate the joint movement by two equations and determine if the tape system can handle the expansion over the desired temperature range.



Different foam cores have differing abilities to help manage thermal expansion stresses.

Want to know more about how tapes can help manage thermal expansion? Contact Tom Brown, Inc. today.

Die Cut Foam Tape Products for Bonding and Assembly Applications

People don’t realize how often they touch or interact with products that are assembled with die-cut foam tapes. The most common one would be the cell phones most of us use every day but there are our appliances, our cars and trucks, utility trailers, and a host of other gadgets that are put together with die-cut foam bonding tapes.

Why use foam tapes?

It comes down to two words- consistency and reliability. Foam tapes are manufactured to precise specifications in terms of thickness, physical properties, and cut part dimensions. This means that you’re applying the same amount of product every time and that translates to consistency.

By contrast, liquid adhesives have much high variability and mess associated with their application and mechanical fasteners require tools and often the bond lines exhibit point pressure where the fastener is installed. With foam tapes, stresses are uniformly distributed around the perimeter or bond line evenly.

Tapes are viscoelastic and have excellent fatigue resistance. While vibration and joint flexing can compromise mechanical fasteners, tapes dampen vibration and absorb shocks allowing the joint to recover time after time.

Common Types of Foam Bonding Tapes

The most common types of foam tapes are acrylics, polyurethanes, and polyethylenes.

Die cut acrylic and urethane foam tapes provide superior bond strength when applied to a clean, dry surface. They exhibit high dynamic shear values. These values are high enough to make them equivalent to one rivet every four inches. If you’re assembling a side panel onto a utility trailer, you get a smooth appearance without any distortion or splitting.

If you use a urethane foam tape to bond a roof panel onto a roof bow support member, you get a joint with exceptional tensile strength and vibration damping capability that translates into longer trailer life without fear of corrosion due to drilled holes.

Polyethylene foam tapes are less expensive than acrylics and urethanes and are an excellent choice for less demanding applications such as appliances, medical devices, and electronic housings.

Other Benefits of Using Foam Bonding Tapes

Foam tapes allow the joining of dissimilar materials such as metal, plastics, and glass. They also permit lighter, thinner materials to be successfully incorporated into a design. This means that materials that cannot be welded or easily riveted can be considered.

Foam tapes seal and bond in one step. You achieve a strong bond that seals out water, dust, and other contaminants.

Products assembled with die-cut foam tapes have improved appearance and aesthetics. The tape is hidden in the bond line and eliminates the need for pre-drilled holes that can act as a site for corrosion. The absence of holes and welds means no additional clean up steps thus reducing production steps and costs.

Are die-cut foam tapes right for you? Contact Tom Brown, Inc. today to discuss your application!

Understanding Silicone Pressure-Sensitive Tapes

In the two preceding blogs, we discussed the historical importance of rubber based pressure-sensitive adhesives and their continued use in today’s applications as well as the “workhorse” adhesive family- acrylics.

In this post, we will consider silicone pressure-sensitive adhesives and their role in current tape applications.

What are they?

Silicone adhesives contain two major components- a flexible silicone gum and a crystalline siloxane resin. By varying the concentrations of these two ingredients, the adhesive properties can be adjusted to meet the demands of various applications.

What’s unique about them?

Silicone pressure-sensitive adhesives are highly specialized and are selected in applications that demand resistance to extremely high or low temperature, moisture, and chemicals.

They are considerably more expensive than either rubber-based or acrylic adhesives and tend to be used in niche applications.

As you can see in the above table, their low glass transition temperature (Tg) allows them to perform in extreme cold without debonding or at an extremely elevated temperature without drying out. Silicone adhesives don’t typically exhibit aggressive tack or high peel values BUT they adhere extremely well to low surface energy materials such as silicone rubber, release liners and fluoropolymers that acrylics and rubber based adhesives cannot. They also exhibit high dielectric strength and are used extensively in electronic and electrical applications.

Common Applications

Silicone adhesive applications include splicing tapes for silicone release liners, fabrics, and elastomers, electrical tapes for insulation resistance, plating, masking, and soldering tapes for electronic applications, and masking tapes for plasma an flame spray processing where high-temperature resistance and clean removability are required.

Silicone adhesives are truly for niche applications but they punch above their weight and can handle conditions that rubber-based and acrylics just can’t. Want to know more about silicone tape products? Call Tom Brown, Inc. to learn more!

Gasketing and Sealing Materials for Indoor and Outdoor Lighting Applications

Indoor and outdoor lighting systems require different types of gasket materials to provide reliable seals against various environmental conditions. These die-cut parts can be used as housing gaskets, lens seals and to assist with thermal management.

Housing Gaskets

Indoor housings or enclosures are often made from painted metals and need to be sealed against moisture, dust, and air. PVC foams can provide an ideal seal and an economical solution. They are easy to apply, can be delivered in die-cut form, strips, or rolls, and provide a tight seal if they are compressed at least 30%. PVC gaskets meet the FMVSS 302 flammability standard, however, PVC is not recommended if the operating temperature of the housing will exceed 150°F.

Outdoor Lighting Seals

Outdoor lighting will typically see more temperature extremes and the gaskets will need to be much more robust to seal against windborne dust, dirt, snow, etc…  Silicone materials are a much better choice for these types of applications.

Silicone gasket materials include silicone foam, solid rubber, and reinforced sponge rubber. These materials offer good compression set resistance and can tolerate temperature extremes from -100° to +500°F. The reinforced sponge rubber incorporates a fiberglass mesh and eliminates any outward extrusion under pressure.

The silicone sponge rubber is a UL recognized weather seal gasket material and fire retardants can be included to meet UL 94V-0 flammability rating.

Solid silicone rubber can be provided in various durometers from soft 30Shore A to firm 70 Shore A. These materials also can be formulated to be low outgassing. Outgassing becomes critical in Led lighting where excessive outgassing can degrade the output and performance of the LED light source.

Adhesive Options

PVC foams typically feature an acrylic adhesive system. These adhesives typically bond very well to painted and unpainted metals and tend to serve as a fixturing adhesive until the gasket is placed under compression.

Higher performance acrylics can be applied to some of the silicone materials and offer temperature performance from -40°-+350°F. These adhesives can handle many outdoor applications for all but the most demanding applications.

Silicone pressure –sensitive adhesives can also be applied to most of the highest performance gasket material and can match the -100° -+500°F range of the gasket itself.

Tom Brown, Inc. supplies die cut and roll form gasket and sealing materials that meet tight tolerances, meet industry standards for flammability and outgassing properties and perform as intended in almost any environment. Contact us today for design assistance and help with your gasket and adhesive selection.

Understanding Rubber-Based Pressure Sensitive Adhesives in Tape Products

History

In 1845, a surgeon named Dr. Horace Day made the first crude surgical tape by combining India rubber, pine gum, turpentine, litharge (a yellow lead oxide), and turpentine extract of cayenne pepper and applying that mixture to strips of fabric. It was the first “rubber-based” adhesive and Dr. Day used it in his practice as a surgical plaster.

Larger scale manufacturing of similar medical tapes began in 1874 by Robert Wood Johnson and George Seaburg in East Orange, NJ. That company would soon become the Johnson & Johnson Company we know today. Later in 1921, Earle Dickson who bought cotton for Johnson & Johnson noticed that the surgical tape kept falling off his wife Josephine’s fingers after cutting them in the kitchen. He fixed a piece of gauze to some cloth backed tape and the first Band-Aid ® was invented.

It took almost 75 years from Dr. Day’s first crude tape until the early 1920’s when the first industrial tape application appeared. The application was electrical tape (although the adhesive was more of a cohesive film than the electrical tape we know today) to prevent wires from shorting.

The second major industrial tape application was a result of the rise of the American automobile in the 1920’s. Two-toned automobiles were becoming popular and automakers needed a way to produce clean, sharp paint lines while using the new automatic paint spray gun. They started using the surgical tape that was available but the paint wicked through the cloth backing and caused defective paint jobs.

Richard Drew, an engineer at Minnesota Mining and Manufacturing (3M) happened to be at a local body shop testing their WetorDry® brand sandpaper in 1925 and he saw the workers struggling to get clean paint lines. He went back to his lab and created a 2-inch wide crimp backed paper tape that became the first “masking tape” for painting.

Jumping ahead to 1942 and World War II, Johnson & Johnson developed duct tape to seal canisters and repair equipment for the military. The tape was a basically a polyethylene coated cloth tape with good “quick stick” properties that made it easy to use in the field for emergency repairs. The world never looked back and duct tape can be found in almost any home or toolbox.

What are Rubber Based Adhesives?

In simple terms, a rubber based pressure-sensitive consists of a natural or synthetic rubber to which various tackifying resins are added along with plasticizers, antioxidants, pigments, and UV stabilizers. These formulations can be delivered to the coating machine dissolved in organic solvents, dispersed in water, or in molten form as a hot melt. Some synthetic elastomers are also curable by radiation such as UV or electron beam(EB).

Natural Rubber Based Adhesives

The naturally occurring rubber harvested from rubber trees is the oldest type of adhesive base and is still in use today in various masking tapes and applications tapes used in the graphics industry. They are inexpensive, can be formulated with predictable adhesion properties, and work well in applications with low shear requirements.  These adhesives work well in ambient and low-temperature applications but will struggle when the temperature exceeds about 120°F.

Synthetic Elastomers

Adhesives and the resultant tapes made from this class of elastomers is very versatile and the most frequently used.

These adhesives typically use styrene butadiene rubber (SBR) or styrene block copolymers such as styrene-butadiene styrene (SBS) , styrene –isoprene-styrene(SIS), or SEBS(styrene-ethyelene/butylene-styrene.. Block copolymers have thermoplastic styrene end blocks with an elastomeric midblock.  Different tackifying resins can be used for each distinct phase of the base and the resulting adhesives can be tailored to exhibit aggressive tack, high peel, and excellent cohesive strength.

There are a variety of tape products made from these systems including double coated film tapes, transfer adhesives, foam tapes, and carton sealing tapes. These tapes can be used for interior bonding and assembly applications, fabricating foam gaskets and seals, and of course duct tape.

Strengths and Weaknesses

In general, rubber based adhesives are not UV or oxidation resistant which is why they tend to be used predominantly in interior applications. Having said that, antioxidants and UV stabilizer packages can be added to the formulation to help mitigate these weaknesses. Some synthetic elastomers exhibit vastly improved UV stability over natural rubbers. Chemical resistance can also be problematic as is resistance to elevated service temperatures (typically 180- 200°F at the top end).

The great strength of rubber-based adhesives is their wide formulation latitude.  These adhesives can be compounded to be removable, repositionable, or extremely permanent. High strength foam bonding tapes can be made from rubber based adhesives or easily removable masking products can also be offered.

Rubber based adhesive adhere to many surfaces including low surface energy plastics such as polypropylene and polyethylene. And to top it all off, rubber based adhesives are economical. They get the job done at a very fair price!

Adhesive tapes made from rubber based adhesives have come a long way since Dr. Day’s first surgical tape and they still offer a cost-effective way to bond, seal, and protect. Contact Tom Brown, Inc. today for samples or more information.

Understanding Acrylic Pressure Sensitive Adhesives in Tape Products

I had great trepidation in writing a blog post on this topic. Firstly, acrylic pressure-sensitive technology is so broad in scope that the relevant information could easily fill a book rather than a brief blog. Secondly, there are many qualified chemists who would be the ideal authors for any writing on this topic.

Despite these reasons, I think that it’s important for readers to at least have some basic knowledge of tapes based on acrylic adhesives. Acrylics are truly the “workhorse’ adhesive platform in the tape world. Various estimates of market size have been published but in general, tape products based on acrylic PSAs are at least 60% of the total square footage produced annually.

This is also not to denigrate rubber based adhesive tapes or tapes based on silicone PSAs. They have their place and do some pretty special things that we will cover in another blog post.

What are they?

Acrylic copolymers are widely used due to their relatively low cost and their relative thermal stability and resistance to oxidation. There are a variety of monomers (the basic building blocks of acrylic adhesives) that can be selected to provide a wide range of performance characteristics in the final adhesive and resulting tape.

Some of the monomers are listed in the table below (1).


Without boring you with too many details, you pick a base and then you can modify the base with other monomers that change the modulus and the resulting adhesion, peel and shear strength you can achieve. These acrylic polymers can be made using various carriers including waterborne, solvent-borne, hot melts, and radiation curable syrups. The type of coating equipment the tape manufacturer has, the cost structure of the market/application they wish to serve, and the performance requirements will dictate the choices they make.

In his work, “Viscoelastic Windows of Pressure Sensitive Adhesives” E.P. Chang (2), used an analytical technique known as DMA (Dynamic Mechanical Analysis) to understand and classify the flow behavior of polymeric adhesives. He divides the types into quadrants:


Chang’s Quadrant Approach to Polymer Material Classification


Now by understanding the flow characteristics, you can map the resulting types of tape products you can produce and the types of performance that can be expected.

 

Adhesive Quadrants and Types


So what does it all mean?

Acrylic pressure-sensitive adhesives offer a broad range of performance characteristics. If you examine the product offerings of the major tape manufacturers and their converters you will notice a myriad of acrylic adhesive tapes from which to choose. There is as you can see a broad range of properties that can be achieved with acrylic chemistry. By understanding the how acrylic adhesives are formulated, the resulting tapes that can be produced from these adhesives, and the performance characteristics needed in the field, the best tape products can be selected for evaluation and qualification in many bonding, assembly, and protection applications.

Want to know more about acrylic adhesive tapes, contact us at Tom Brown, Inc. for more information and samples.

References

  • Bartholomew, E. “Acrylic Pressure Sensitive Adhesives Exhibiting Enhanced Adhesion to Low Surface Energy Substrates” Pressure Sensitive Tape Council, 2017
  • Chang, E.P. “Viscolelastic Properties of Pressure Sensitive Adhesives”, The Journal of Adhesion, 1997, Vol. 60, pp. 233-248

Critical Considerations for Choosing a Die Cut Parts Supplier

Time is precious on the manufacturing line, and no one wants to spend it fiddling with tape and gaskets. Die cut parts simplify assembly work and ensure consistency unit to unit, but only if the supplier can deliver a quality product. Here’s a quick primer on the benefits of die cut parts and a run- through the critical points to consider during sourcing.

Why buy die cut parts?

Yes, die cutting sometimes resembles a  “cookie cutter” method, but when done right it’s a robust industrial process. In its’ most basic version, a steel rule die shaped to the correct dimensions required is pressed into the material to cut a shape.  It can be cut all the way through into a discrete part or “kiss-cutt” to leave the backing layer or release liner intact.  Kiss cutting keeps the parts in a sheet or on a roll and often simplifies storage. Then, when needed, it’s just a case of peeling each piece from the roll for application.

Die cutting machines take several forms. There’s the flatbed or platen press, which moves up and down to cut shapes from a sheet or roll, and there’s rotary die cutting.  A rotary machine has the cutting tool embedded on the outside of a hardened steel cylinder. Material in roll form such as tapes or label materials are fed underneath the die and the die cuts the shape as high speeds.  There is another common method of cutting loosely referred to as “digital die cutting”. These methods utilize a CNC interface where a CAD file can be loaded into a machine and parts can be cut individually. The “cutting tool” may be a high-pressure water jet, a high-speed reciprocating knife, or a laser. These methods are extremely useful for large parts or lower volume requirements.

The big advantage of die cut parts is that the shapes are pre-cut when the materials reach the line or job site.  All the installer or operator does is peel and stick. A secondary benefit is  quality. As die cutting is highly repeatable, every piece is the same size and shape, reducing variability in the final assembly. And third, there’s less waste compared to cutting shapes on site.

Choosing a supplier

Here are some of the most important points to consider when evaluating potential suppliers:

  • Material range and manufacturers. Do they deal with more than one highly rated raw material vendor? High-quality raw material suppliers and validated processes yield high-quality parts.
  • Does the supplier have more than one cutting process to match the specifications and volumes required?
  • Would kiss-cutting make life easier, or are individual discrete parts acceptable? As mentioned previously, kiss cut parts are very easy to handle and can be automatically dispensed.
  • Dos the supplier have the knowledge to help engineer the composition and dimensions of the parts to the intended application?
  • What accuracy is required? Die cutting machines and tools have different tolerances. Over specifying, tolerances can result in unnecessary tooling costs but under specifying creates waste by having parts that don’t fit or can’t do the job needed.

Pick your partner carefully

Die cut parts eliminate waste while improving consistency, but not every supplier can deliver what manufacturers need. Consider the points raised here and evaluate parts suppliers with care.

Questions Your Tape Supplier Should Ask

Many companies convert and sell tape products. Far fewer are interested in becoming a real partner. While the term “partner” is often overused in today’s business lingo, a reliable and knowledgeable supplier is a very valuable resource. Building a partnership takes time and effort, but the payoff is worth it with better service and the knowledge that you’re using the best tapes for your products or projects.

What tapes?

Tapes have become indispensable in construction, transportation, and many other industries. Adhesive tapes are used to assemble panels, secure cladding and join other components. Glazing tape holds windows together while muntin mounting tapes allow attachment of trim parts that give them that classic architectural appeal. Tapes aren’t an afterthought; they’re an essential component in many construction and assembly tasks.

Does your tape supplier have the knowledge to be a real partner?

The best tape suppliers take the time to understand their customers’ particular demands of their business and industry. They speak the language. They’re committed to their customer’s success, and that means selling the tape products that work best, not what’s in inventory or hard to move.

A deeper knowledge of what you’re doing helps a supplier recommend alternative products that might perform better while saving you time and money. A good way to gauge a supplier’s expertise and level of commitment is through the questions they ask. Here, separated out under four headings, are some to look for:

About the operating environment

  • What temperature range is needed? (Consider both the upper and lower limits as well as application temperature.)
  • Is UV resistance required? (This should always be considered when exposure to sunlight is likely.)
  • Will it be exposed to moisture rain, or other chemicals?
  • How much flexing or sway should be expected? (Buildings and vehicles all flex under load. It’s essential the tapes used in assembly can handle this movement.)

About how the tape itself

  • What materials are being bonded, protected, or sealed?
  • Is adhesive needed on one side or both?
  • Will it be applied by hand or by a dispenser?
  • What adhesive properties are needed?
    • Quick stick? Ultimate peel or cohesive strength?
    • The ability to be repositioned or removed at a later time ?
    • What is the current assembly and manufacturing process? What cost improvements can be made with labor, reduction of steps, materials workflow, etc..?

About form factor

  • Can you use rolls or do you need die cut parts?
  • What dimensions are required?
  • Would longer length spools help you to reduce changeovers? (great choice if you’re an extruder)
  • Do you need individual discrete parts or would having them kiss cut on a roll make more sense?

Regarding logistics

  • Would frequent small deliveries be more convenient than one large shipment?
  • Are there any special requirements for pack formats or protective packaging?

Good suppliers invest time in relationship-building

Asking questions to learn about their needs takes time. Some tape suppliers don’t want to invest time or effort to build a relationship; they’d rather just take the order and move on. That short-term approach is  not going to benefit the tape buyer.

Whether you’re in the construction industry or elsewhere, it pays to find suppliers who want to be partners. Partnerships are about a long-term approach to solving problems and delivering results. One way to evaluate prospective partners is by looking closely at questions they ask.