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.

Questions to Ask Your Die Cut Parts Supplier

Price and cost are two very different things. The cheapest parts often carry a lot of associated costs, while those with the higher price tag arrive on time, install easily and with little waste. That’s why it’s essential to ask any potential vendor a lot of questions, not just about the products they carry but also the service they provide.

Poor quality and service cost time and money.

Die cut parts, like gaskets and tapes, easily “slip under the radar,” going unnoticed until the installation team starts to complain. Common problems include supposedly kiss-cut shapes that weren’t, shapes that don’t fit the way they should, poor quality pressure sensitive adhesive application, torn release paper and of course, lack of inventory. (Nothing brings work to a halt faster than that last one!)

These problems can be avoided by partnering with a reputable, established die cut parts supplier. The best ones will support your business and help you grow, but how you decide who they are? Here are some questions to ask.

How long have they been in the die cut parts supply business?

Building a partnership means looking toward the long term. Past performance is often indicative of what’s to come, so find a vendor with a track record of dependable performance.

Do they carry plenty of raw materials inventory or only order once they’ve got your business?

Inventory is expensive, so some parts suppliers only buy what they need when they need it. That extends delivery dates, which can be a major problem when you need to keep the project moving.

Do they keep cut shapes in inventory or is theirs a cut-to-order business model?

Ideally, they’ll do whatever is best for you. Holding inventory has a cost but minimizes lead time. Alternatively, do they have the processes and skills to provide a rapid order turnaround?

What cutting methods/technologies do they have?

If they only use flat bed and rotary die cutting, there could be setup charges and minimum order quantities. If they have water jet processing in addition to die cutting, they’ll be positioned to handle orders from prototype quantities up to thousands of pieces.

How quickly can they deliver?

A supplier on the other side of country can’t respond as quickly as one that’s across the street. Check where they’re located, where they’ve put their warehouses and where your parts will ship from.

What tooling do they use?

Steel rule dies are the least expensive, and are often good enough for many components. For higher accuracy though, it’s best to look for a supplier who can handle solid milled and matched metal dies. While steel rule tools will typically achieve +/- 0.010” tolerances, matched metal can maintain as tight as +/-0.001”.

Choose your partner with care

By wasting your time and money, unreliable suppliers and substandard materials will delay a project and also make you look bad. That’s why it pays to evaluate potential vendors with the utmost care. The questions listed here will help you identify companies to buy from -not just once but over and over.

Multipurpose Medium Density PVC Foams

Medium density, closed cell PVC foams are considered a “workhorse” type product in  gasketing and sealing applications. It’s like that handy screwdriver or utility knife we all have. You don’t miss it until you don’t have it. One of the premier medium density PVC product lines is the V-740 series from Saint Gobain.

V-740 Series Product Features and Properties

The V-740 series utilizes a 9 lbs. per cubic foot density PVC foam core. This means you have a very cost effective way to produce seals and gaskets as compared to hand applied sealants and caulks.

One side of the foam core is coated with a pressure-sensitive  acrylic adhesive system designed to adhere to a variety of surfaces; helping to fixture the foam in place until it is put under compression. The foam is dimensionally stable, resistant to weather, fungus, and oxidation, and maintains its’ flexibility at low temperatures.

Applications

This product can truly handle a wide variety of sealing jobs and do them very well. The V-740 series excels at sealing out water, air, and dirt in truck and trailer bodies. In the construction industries, it seals exterior wall panels, HVAC joints, foundation to sill gaskets, and a host of other window and door weather stripping applications.

Product Options

The V-740 series is available in black or gray with or without adhesive (although the adhesive coated version is the most popular) and it comes in 5 thicknesses.

Workhorse products like the V-740 series are easy to overlook. They do so many things so well  that it’s easy to take them for granted. Contact Tom Brown, Inc. today for a sample roll or a die cut V-740 gasket.

Swirl-Free PVC Foams- The V-710 Series

Many sealing and gasketing applications require subsequent drilling for the insertion of screws, bolts or rivets to complete an assembly. The auguring action of a drill bit or screw can cause the foam gasket or seal to rip or tear. This compromises the integrity of the seal itself.

The V-710 series from Saint Gobain solves this problem by taking a medium density PVC foam and adjusting the PVC formulation so that the foam won’t move or twist when the fastener is inserted.

V-710 Series Product Features and Properties

The V-710 series utilizes a 10 lb per cubic foot density PVC foam core. This means you have a very cost effective way to produce seals and gaskets that will work hand in hand with drilling and various mechanical fasteners.

One side of the foam core is coated with a pressure-sensitve  acrylic adhesive system designed to adhere to a variety of surfaces; helping to fixture the foam in place until it is drilled, mechnical fasteners inserted, and then put under compression. The foam is dimensionally stable, resistant to weather, fungus, and oxidation, and maintains its’ flexbilty at low temperatures.

Applications

This product works exceptionally well in product assembly operations.. The V-710 series excels at sealing out water, air,and dirt in truck cab roofline seals and vehicle overlap seals.  In the construction industry, it is an excellent choice for corrugated panels, modualr wall systems, HVAC seals, and outdoor lighting fixtures.

Product Options

The V-710 series is available in gray with a pressure sensitive acrylic adhesive on one side for easy fixturing and it comes in 5 thicknesses.

The V-710 series is truly a unique product line that solves distortion and tearing issues that compromise seal integrity when mechanical fasteners are used for final assembly operations.  Contact Tom Brown, Inc. today for a sample roll or a die cut V-710 gasket.

Light-Weighting with Adhesives and Tapes

stronger adhesive

Light-weighting is a popular topic in a variety of industries including transportation, general industrial applications, and even the building and construction market. In transportation applications, the reduction in fuel consumption is a primary driver along with the associated environmental impact. However there are other benefits to light-weighting initiatives- reduced costs, flexible product designs, and improved product performance.

Light-weighting strategies typically rely on the use of plastics, foams and thinner metals. It is critical to understand the bonding and assembly challenges associated with these material choices.

Let’s take a look at some of the main challenges of bonding and assembly in a new lightweight design and see how adhesives and tapes can assist the design engineer.

Dissimilar Materials

New lightweight designs often involve the bonding of two dissimilar materials such as a foam or plastic and a light gauge metal. These materials not only possess very different weights but more importantly vastly different chemistries.  The metal might exhibit a high surface energy and be relatively easy to bond to with an adhesive while the foam or plastic might have much lower surface energy. The goal is to achieve structural strength and integrity while avoiding concentrating stress in any one area.

Obviously it is not easy to weld plastic to metal so that method is not feasible. Rivets or other mechanical fasteners add weight and the holes associated with them can create an ingress path for moisture, air, or dirt and create weaknesses. Adhesives and tapes typically weigh less than mechanical fasteners and they enable stress to be distributed along the entire joint. 

Bond and Seal In One Step

Mechanical fasteners typically involve drilling or punching holes into the materials. Those holes can lead to moisture ingress, airflow, or create an initiation point  for corrosion.

Adhesives and tapes can bond and seal large or small surface areas. They are often both watertight and airtight while still providing a strong, lightweight bond.  

Thermal Expansion and Contraction

Materials expand or contract as the ambient temperature changes and they often do so at very different rates which can produce stress in the bonded area. 

Mechanical fasteners tend to concentrate stress in one area. When that area is stressed by thermal expansion or contraction, there is no ability for the fastener to absorb or redirect any of the stress and material fracturing can occur. When this happens pathways are opened for water and air ingress

Tapes and adhesives are able to bond materials with different coefficients of thermal expansion and contraction with superior bonding performance.

Noise, Vibration and Harshness (NVH)

The automotive industry first comes to mind when thinking about reducing all those unwanted rattles, vibrations, engine noise, etc… but that is not the only industry where this is important. The truck and utility trailer industry along with the fire and emergency vehicle market is constantly trying to extend trailer or emergency vehicle service life and all those rattles and vibrations cause wear and tear on components over an extended time period.

Tapes and adhesives excel with NVH problems. Tapes in particular are viscoelastic meaning that they exhibit both viscous and elastic properties when undergoing stress and deformation. This property allows the tape to turn vibrational energy into heat and reduce or eliminate the vibration.

Aesthetic Considerations

Looks matter. Rivets, bolts, screws, and holes affect the visual design and can sometimes detract from the overall product appearance.

Adhesive and tape bonded joints are largely invisible. The tape or adhesive is hidden between the bonded materials. The surfaces stay smooth for any additional finishes or graphic application.

The Right Adhesive or Tape System

Using adhesives and tapes for light-weighting requires an understanding of the overall design objectives and the subsequent assembly processes. It is not hard but with a knowledge of the basics and an understanding the capabilities of different adhesives success is very achievable.

Adhesive technology has progressed tremendously in recent year and systems that address light-weighting bonding challenges with different materials, thermal expansion rates, flexibility and environmental exposures are readily available. Adhesives are delivered in different form factors including liquids, sprays, and tapes making them easier to integrate into an assembly process.

Light-weighting will continue to be a dominant trend in product design. Selecting the best possible bonding method will play a more critical role as designers and engineers try to remove as much weight as possible. The good news is that adhesives and tapes are an enabling technology, one that can help companies solve light-weighting  challenges for years to come.  

Understanding Pressure Sensitive Tape Properties

When it comes to pressure sensitive adhesive tapes, there isn’t a convenient single rating system for how “strong” the tape might be. The adhesive systems on these tapes operate differently in a variety of environments, and there are performance properties that can be judged as more important than others for certain applications.

Generally tack, peel, and shear resistance are the primary physical properties that are measured and reported. There are many more tests that can be performed to develop a more in depth understanding of a tape’s properties. These might include testing for fire or burn properties, solvent resistance, and a host of other specialized tests but if you have a basic grasp of peel, tack, and shear, you can make some reasonable inferences about how a tape might perform.

Environmental Factors

Pressure sensitive adhesive tapes all exhibit some degree of sensitivity to temperature fluctuations. As a general rule, when the temperature increases, the adhesive system can become “softer” to some degree depending on how it’s formulated. When the temperature becomes colder, the adhesive can become “harder”.  This is a function of each adhesive’s glass transition temperature (abbreviated Tg). In simple terms, glass transition temperature is that crossroad temperature where the adhesive ‘transitions” from “rubber-like” (softer) to more “glasslike” (firmer).

Some adhesive systems can tolerate larger temperature ranges than others due to their base chemistry and the way they are formulated and processed-although these temperature extremes may potentially be unnecessary for certain applications.

Measuring Shear Resistance

Shear testing measures the ability of the adhesive system to maintain a bond under a constant load. It provides insight into the internal strength of the adhesive itself. The testing can be performed in a static mode and in a dynamic mode. Static shear testing is useful when a tape may be asked to support a constant load in an application. (think of holding a panel onto a vertical frame system). Dynamic shear testing can provide useful information on how well the tape can resist a sudden load such as a shock or a sudden wind load.

Testing Tack

Tack is the property that controls how quickly a bond is formed when it is brought into contact with a surface with very slight pressure. It is ability of the adhesive to “wet” the surface that it contacts. The most common way we experience tack is with our thumb. We stick our thumb onto the tape’s adhesive surface and pull it away. The more it “grabs” our thumb, the tackier we perceive the tape to be. The thumb however is not a reliable predictor for  how a tape will function in an application.

There are applications where tack(specifically high tack) is very important. Flying splices on paper or film converting machines and wire management hooks and clips for appliances are two applications where immediate loads will be applied and the tape must hold without delay.

Tack is sensitive to a variety of factors including the properties of the adhered (typically roughness or topography) along with temperature and processing conditions.

There are 4 principle test methods for measuring tack- loop tack, rolling ball tack, probe tack, and quick stick. Without going into too much detail about individual test methods, loop tack is often viewed as the most repeatable and consistent and many tape manufacturers now report it routinely. A loop of tape is formed and brought into contact with a test plate.  The loop is then pulled away on a tensile testing machine and the value recorded. The downside of loop tack is that the substrate the adhesive is coated on can have a significant effect on the results.

Probe tack was popular for many years since it more or less resembled the “thumb tack” test but wide variability in the test data has often been observed. In this test, a metal probe is brought into contact with tape surface, allowed to dwell for a specified time, and then pulled away. The force of removal is reported in grams.

Rolling ball tack is a simplistic test where a ball bearing is released down a ramp onto a tape specimen. The adhesive “arrests” the motion of the ball bearing due to grab and a “plowing effect” and the distance need to stop the ball is reported. This test is often used as a quick QC test on a production line.

Quick stick also uses a tensile or peel tester as in the loop tack test to pull a tape specimen off at a 90° angle with short or no dwell time. This differs from normal peel adhesion testing since only the weight of the tape itself is used to initiate the bond or a very light 25 gram roller.

Peel Testing

Peel adhesion testing is measuring the force required to remove a tape specimen from a test panel at a controlled angle (usually 180°or 90°), at standard rate, and with a defined dwell time.

The tape is applied using a weighted rubber roller to a stainless steel (or other panel material that is defined) and then allowed to dwell on that panel. The tape can be peeled away immediately but dwell times from 5 minutes up to 72 hours are common.

Some adhesive applications require temporary fixing of the tape to the surface with the intent of removing it in the future without adhesive residue. Think of the surface protection films used on appliances or paint masking tapes. In these applications, lower peel levels(and likely tack) are needed to impart stable removal over time.

In more permanent applications, higher peel forces will likely be needed in order to permanently affix the tape to the substrate or to bond two surfaces together. This does not necessarily mean that the tape must exhibit high tack (whether you test it with your thumb or a loop tack method). Many high tack tape systems depending on how they’re formulated might have lower ultimate peel strength versus a tape that seems “not as tacky” but develops very high peel adhesion to specific surfaces.

One final note- peel testing on a standard stainless steel panel can be useful but it is imperative that peel testing also take place on the surfaces to which it will actually be applied. That peel testing will yield a much richer date set. Those panels can also subjected to various humidity conditions, high or low temperatures and chemical exposures that the tape will actually see. A much deeper understanding of field performance can be realized (and it may or may not have anything to do with tack as we perceive it).

Accelerated Aging Studies

Tapes are typically subjected to various types of accelerated aging. This may involve aging the actual roll of tape at some elevated temperature and/or humidity to gain insight into how well the tape will survive shipping and storage conditions once it is in the field. These studies provide data that helps the manufacturer set a shelf life for the tape so the customer can be reasonably assured that the tape will work when they receive it.

Other aging studies can be significantly more involved. They might include making test panels and exposing the panels to the sun in a state such as Florida or Arizona for a year and then performing peel and shear tests on those panels. In other cases, actual mock ups of the finished product might be fabricated and then subjected to artificial sunlight, humidity, cold chambers, or all of these in some cycling sequence in order to understand how these environments affect the tape’s performance and behavior over time.

If you’d like to learn more about adhesive tape testing or to discuss the specifics of an application, contact Tom Brown, Inc. today.