Category Archive: Epoxy Resins

Epoxies vs Polyurethanes

Resin coatings are extremely useful in commercial and industrial settings and even in the art world. Resins are commonly used to coat surfaces like concrete floors or countertops, create high-gloss finishes, and make repairs. Two of the most common resins are epoxies and polyurethanes. Generally, epoxies are rigid, while polyurethanes will typically be more elastic. Both can be formulated to be extremely strong, pass biocompatibility testing, or have high resistance to UV light.

At Hapco Inc., we are a leading manufacturer and distributor of polyurethane and epoxy coatings, release agents, adhesives, and other liquid molding technologies. Since 1969, we have offered our clients quality formulations that are applicable in many industries.

What Are Epoxies

Steralloy R-Series Applications

Epoxy plastics are typically created by mixing epoxy resins (Part A) with a matching catalyst (Part B) at various ratios. The mixture then cures to form a solid material. Additives are often used in resin coatings to improve durability, UV stability, adhesion properties, and other factors. Epoxies can come in the form of a single-component resin that cures by heat or UV light, and it can be formulated as a liquid resin, powder, or putty.

Epoxies have a wide range of applications, including:

  • Electronics and Electrical Systems: Epoxy resins and powders are excellent insulators and offer protection from short circuits. Because of this, they are used in the manufacturing of generators, transformers, insulators, and motors.
  • Coating and Sealant: Epoxies are commonly used in the manufacturing of ships, UAVs, military vehicles, and aircraft to protect surfaces, strengthen materials, and keep them from rust and deterioration. Due to the naturally thicker viscosity, epoxy resins can create very hard, durable finishes with adequate thickness after one or two coats.
  • Repairs: Epoxy resins are often used to repair industrial manufacturing equipment due to their strong adhesive properties. Fragile objects like ceramic and glass, and stronger materials like metals, woods, and other synthetic materials, are frequently coated, repaired, or bonded using epoxy resins.
  • Filter & Ultrafilter Manufacture

Advantages of Epoxies

Depending on the application, epoxies offer a range of benefits, including:

  • Lower Cost: Epoxies are typically more affordable than polyurethane alternatives.
  • Adhesion Properties: Epoxies can adhere to most substrates without a primer.
  • Excellent Dielectric Properties: As an insulating material, epoxies can transmit electricity without acting as a conductor.
  • Versatile: Depending on the resin and hardener used, epoxies can be rigid or flexible to suit the application requirements.
  • Moisture Resistant: Epoxies are suitable for applications with high moisture exposure due to their high resistance to humidity and moisture.
  • No VOCs: Epoxies don’t require a solvent for most applications, so they do not release harmful fumes into the air.

Disadvantages of Epoxies

  • Higher Viscosity
  • Yellowing: Epoxies will yellow over time when exposed to UV rays.
  • Brittle: Rigid epoxies are prone to chipping and cracking if not properly maintained.

What are Polyurethanes

Ultralloy 200 Series Group
There are two types of polyurethanes: thermoset and thermoplastic. Hapco manufactures thermoset polyurethanes, which are formed by reacting a polyol with an isocyanate. The resulting polymer (Part A) is then cured with a catalyst (Part B). Once they’re set, they can’t be melted or softened. Thermoplastic polyurethanes, on the other hand, can be reheated and reprocessed multiple times without losing their properties. Polyurethanes have many desirable properties, including high tensile strength, natural UV stability, and abrasion resistance. They also have good thermal and chemical resistance and are generally non-toxic.


The possible applications for polyurethane resin include:

  • Medical: Polyurethanes are used in many hospital applications because they are safe for individuals with latex allergies. They are used in beddings, gloves, wound dressing, and tubing.
  • Insulation: Polyurethane foam is an energy-saving insulation option for cars, homes, and electronics. Polyurethane reduces external noise in buildings and vehicles and maintains a desirable temperature.
  • Electronics: Polyurethane can be used to encapsulate, seal, and insulate different electronic components. They are also used to make microelectronic components and cables.
  • Automotive: Polyurethane foams are used in cars to provide insulation and impact protection to keep passengers safe in the event of a crash. Polyurethane can also be used to create plastic interior parts such as console covers, door panels, and headliners because it’s soft and pliable.
  • Packaging: Because polyurethanes can come in expanding foam form, you can use it for packaging items in different shapes. It also reduces the weight of the package.

Advantages of Polyurethanes

Click to Expand Epoxies vs Polyurethanes Infographic

Many industries choose polyurethanes for their applications due to their range of benefits, which include:

  • Hardness Range: Polyurethanes can be made flexible or rigid, and can fall anywhere between 20 SHORE A to 85 SHORE D on the hardness scale.
  • UV Resistant: Polyurethanes are naturally resistant to ultraviolet rays and have much better color stability over time.
  • Abrasion & Impact Resistant: Polyurethanes are suitable for applications in extreme environments because they resist surface damage and can withstand extreme force.
  • Water, Oil, & Grease Resistant: Ideal for subsea applications, polyurethanes keep their structural integrity when exposed to water, oil, and grease.
  • Thermal Shock Resistant: Thermoset polyurethanes are incredibly resilient to thermal shock and resist rapid and significant temperature drops without shattering.
  • Low Odor

Disadvantages of Polyurethanes

  • Higher Cost: Although polyurethane has a long lifespan, some businesses can’t afford the high upfront cost. You might have to opt for polyester or epoxy resins because they’re cheaper, although they won’t last as long as PU.
  • Moisture Sensitive: While still in their liquid state, polyurethanes are susceptible to humidity and moisture, and will crystallize in the containers if too much moisture is present. When mixed, an excess of bubbles will appear or the resin may behave like an expanding foam.
  • Shorter Lifespan: Flexible PUs, especially the lower durometers, will degrade over time. Being under stress will cause molecular bonds to break down much faster than rigid materials.

Epoxies and Polyurethanes at Hapco Inc.

Resins are tough, flexible, and versatile, making them the perfect choice for a wide range of applications. Hapco Inc. offers multiple polyurethane and epoxy products for different applications. With over 50 years of experience in this industry, we have the expertise and skills to produce the best resin materials in the market. We are an ISO 9001-certified company dedicated to meeting all our customers’ needs. Contact us today for more details about our materials or request a quote to get started.

Filters: A Key Tool in the Fight Against Covid-19

For over 4,000 years, the evolution of the filter has been directly linked to the improvement of human health and life expectancy. The first great civilizations, like the ancient Egyptians, used sand and gravel as filter media to improve the taste and appearance of water. Today, filters have become an essential component to our entire way of life. They are found in countless industries, manufacturing facilities, processes, and in many cases, the end products themselves. More importantly, filters are enabling the tools and devices that are essential to defeating this invisible enemy and returning the world to some semblance of normalcy.


Since the onset of this pandemic, our society has gained a new appreciation for respirators, ventilators, and vaccines, as well as the vital role they play in saving lives and preventing future outbreaks. Like everything else in our modern industrial society, these life-saving tools all rely on specialized filter media and advanced filtration technology to function. It is obvious how filters are utilized in equipment like respirators and ventilators, but when it comes to vaccines the use of filter technology is not immediately apparent.

How are filters used for making vaccines?

Covid 19 Vaccine

A successful vaccine is the result of complex scientific processes that include the concentration of proteins and enzymes, blood plasma purification, virus and bacteria concentration and removal, as well as cell harvesting, clarification and washing. These procedures are all enabled by specialized filters and equipment.

Some common methods used in bioprocessing include membrane filtration, tangential flow filtration, centrifugation, and depth filtration. Implementing the proper filtration technology can have a positive effect on yield, product consistency, and overall efficiency of the entire operation.

What types of filters are used?

Hollow Fiber Filters

Hollow fiber filters possess excellent filtration performance and are commonly used in dialysis, water purification, reverse osmosis, separation of components from biological fluids, and cell culture devices to name a few.

Cartridge Tangential Flow Filter

Tangential flow filtration (TFF) systems are used extensively in the production of vaccines and other pharmaceutical drugs. They can be used to remove virus particles from solutions, clarify cell lysates, harvest and retain cells, and they can concentrate and desalt sample solutions ranging in volume from a few milliliters up to thousands of liters.

Hepa Filter Small

HEPA (High Efficiency Particulate Air) filter works by forcing air through a fine mesh that traps harmful particles such as dust mites, pollen, pet dander, smoke, and even airborne viruses. HEPA filters are used in applications where contamination control is required, such as the manufacturing of semiconductors, disk drives, medical devices, food and pharmaceutical products, as well as in homes, vehicles, and hospitals.

How is Hapco involved in the filtration and ultrafiltration industry?

Hapco has been custom formulating adhesives, sealants, and potting compounds for some of the world’s largest filter manufacturers for over 40 years. Our materials and processing equipment are a key component to manufacturing a wide variety of specialized filters. As a preferred supplier to corporations like MilliporeSigma, Pall Life Sciences, and Koch Membranes, we take pride in our ability to provide customers with the highest quality polymers and the most reliable processing equipment available.

BPA Free

As we look to a post-pandemic future, our chemists are developing new formulations and processing methods to meet the needs of filter manufacturers around the world. We are currently conducting in-house testing on Filter-bond™ R-3590: a new epoxy formulation for the filtration market that is both Bisphenol-A (BPA) and nonylphenol-free.

What other Hapco products are used to manufacture filters?

Filter Bond 2020 Cover

The Filter-bond™ series was first developed in the 1980’s for various filtration and ultrafiltration applications. It includes formulations that do not contain aromatic amines or carcinogenic or mutagenic materials, systems that can be used to pot moist membrane material in place without foaming, and systems that are easily trimmed when used for pre-potting filters. Filter-bond™ includes a line of flexible and rigid materials to meet a wide variety of filtration applications. All Filter-bond™ products are compatible with Hapco’s MiniFIL and RapidFIL dispensing machines, which are used for potting or encapsulating various filter media.

Final Thoughts

Filters are one of mankind’s greatest achievements and a major reason our life expectancy has increased dramatically over the past 200 years. They clean the air we breathe, the water we drink, the fuel that moves us forward, and the medicine that keeps us healthy. Without them, there is simply no way to manufacture the life-saving and preventative drugs that offer us a light at the end of this tunnel.


Fun Fact: Hippocrates (460-370BC) was the first major proponent of water filtration in recorded history. He advised people to first boil, then filter water through two sewn together pieces of cloth which eventually came to be known as a Hippocrates’ Sleeve.

River Cribbage Board Using Hapco Resins

Over the past year, the wood and resin craft market has hit its stride. A quick search on Etsy or YouTube yields thousands of results. We’ve fielded numerous calls from artists, furniture makers, and entrepreneurs trying to find a good epoxy to use for casting river tables, wood/resin jewelry, lamps, and various other artistic endeavors.

River Epoxy Examples

Examples of high end goods that marry wood and epoxy with incredible results.

We were prepared to formulate a new material to meet the demands of the market, but first we wanted to gauge how our current formulations performed. We decided to test some of our high-end epoxies to get an idea of the handling properties that would be important, and also to gain insight into some of the challenges facing end-users.

Ultraclear Coaster

One of the many tests. This was made using Ultraclear 480N-10 with a drop of TD-23 blue tint.

After months of testing, we found that our Sympoxy™ 1010-CA810 yielded the best results. It has a 1:1 ratio, great viscosity for coating, a 45 minute gel time, 24 hour cure time, and it has a beautiful, glossy finish. To really put this material to the test and to gain more first-hand experience, I decided to use the Sympoxy for a personal project that I had been planning for a few months: A ‘Game of Thrones’-inspired, epoxy river cribbage board.

A Helpful Guide to Processing High Viscosity Resins

High Viscosity Epoxy

The term “viscosity” refers to the thickness or flowability of a liquid. Viscosity numbers range from 1 (water) to millions of centipoise (cP) or pascal seconds (Pa.s), 1cP = 0.001 Pa.s. Refer to our viscosity comparison chart here.

Urethane and epoxy resins with viscosities ranging from <100cP to 1,000cP are ideal for most generic casting applications. They de-air very well on their own and flow easily into closed molds, whether mixed and poured by hand or dispensed using meter-mixing equipment. However, there are many specialty materials, such as, Hapco’s Steralloy™, Filterbond™ and Hapflex™ resins that are formulated for highly-engineered applications, and because of their unique chemistries, they have a thicker viscosity than other products, making them a bit trickier to process.

Vacuum Degassing

When mixing and pouring by hand, Hapco always recommends vacuum degassing the mixed resin prior to pouring. With viscous materials, it can be helpful to add a few drops of a surfactant, such as Hapco’s

Anti-Air™ product, which reduces surface tension and allows the resin to degas more easily. However, vacuum degassing alone does not always alleviate air bubbles due to cavitation of the material as it flows through the mold. It may also be necessary to cure your parts under pressure using a pressure-pot or molding chamber, like Hapco’s unique X-Series Molding Chambers.

X-11 Molding Chamber by Hapco, Inc.

When using meter-mix dispensing, Hapco recommends designing a mold that fills from the bottom up. A general rule in this case is to design the mold so that the output opening(s) equals 2-4 times that of the input. In simple terms, if you have a 0.50” diameter input, your out-put should equal 1”-2” in diameter. This enables a “pressure drop,” which minimizes any back-pressure build-up caused by shooting a viscous material into a closed mold.

Filling Mold

When dealing with complex mold geometry, it may be beneficial to use a two-step degassing process. After initially degassing the resin mix, fill the molds and place them under vacuum again for an additional few minutes. This not only helps to release trapped air caused by material cavitation, but it will also “pull” the viscous material into the cavity to ensure a complete fill, especially if your mold has thin walls or complex geometry. While degassing the molds, the material inside will not swell up as it did during the initial degassing step, however, it may continue to “boil” somewhat. Therefore, it is advisable to fabricate a small “chimney” around the top of your mold to prevent material from spilling out. You can do this easily with wax, putty, or a simple strip of packaging/duct tape wrapped around the top of the mold. After secondary degassing you may find the need to top off the molds to ensure they are filled to proper height, in which case you should be able to do so without the need for further degassing

Vacuum and Pressure

Other suggestions for thinning higher viscosity materials are as follows: Pre-heat the resin to 80° – 110°F. It is really only necessary to pre-heat the thicker component which is typically the Part A for most materials. As a general rule, for every 10° you heat the material above room temperature, the material viscosity is cut in half. Bear in mind though, that heat will also cause the material to gel faster, thereby reducing your overall work time. In lieu of pre-heating the resin, you can pre-heat the molds instead. This will maintain work time for mixing, and still thin the resin viscosity as it flows into the warm molds. Another suggestion would be to add a small amount of solvent, such as, isopropyl alcohol or acetone into the resin mix. Solvents will cut the viscosity without impacting curing or material properties in most cases, as they will flash off quickly once the material starts its exothermic reaction.

The bottom line is that you will need to incorporate the proper equipment and techniques into your process in order accommodate using viscous materials. Water-thin materials require very little in the way of specialized equipment and they certainly make things easier. However, limiting your material offerings can also limit your opportunities for getting more of those “high-dollar” projects. My advice for expanding your business opportunities is to think “outside of the mold-box,” and have enough flexibility in your process to take on those jobs that nobody else wants!

Choosing the Best Epoxy or Urethane for Electrical Applications

In our previous post, we discussed the application of potting and encapsulating using urethanes and epoxies. When choosing the proper urethane or epoxy for an electrical application, there are some important considerations to keep in mind. In this article, we will discuss those considerations and how they apply to the world of urethanes and epoxies.

Potting Electronics with Epoxy

Here are some examples of electrical applications using urethanes and epoxies:

Di-Pak R-Series Group

The 3 most commonly sought after resins for electrical applications can be classified as electrically conductive, electrically insulative, and statically dissipative.


Electrically conductive materials have a low electric resistance and electrons flow easily across the surface or bulk of the material. Charges go to ground or to another conductive object that the material contacts. These materials have a surface resistivity less than 1 x10^5 Ohm/sq or a volume resistivity less than 1 x 10^4 Ohm-cm. Electrically conductive resins are typically filled with metallic or conductive particles.


Electrically insulative materials prevent or limit the flow of electrons across their surface or through their volume. Insulative materials are difficult to ground and have a high electrical resistance. Static charges remain in place on these materials for a very long time. These materials are defined as having a surface resistivity of at least 1 x 10^12 Ohm/sq or a volume resistivity of at least 1 x 10^11 Ohm-cm.

Di-Pak E-Series Group

Statically dissipative materials have a surface resistivity equal to or greater than 1 x 10^5 Ohm/sq but less than 1 x 10^12 W/sq. They have a volume resistivity equal to or greater than 1 x 10^4 Ohm-cm but less than 1 x 10^11 Ohm-cm. For these materials, the charges flow to ground more slowly and in a somewhat more controlled manner than with conductive materials.


RoHS Compliance

What is RoHS Compliance?

The European Union set forth the RoHS (Restriction of Hazardous Substances) Directive to establish environmental guidelines and legislation to reduce the presence of six (6) materials deemed hazardous to the environment. To comply, products entering the EU must not have a homogeneous presence of these materials above the following levels by weight percentage:

Lead (Pb) < 0.1%

Mercury (Hg) < 0.1%

Cadmium (Cd) < 0.01%

Hexavalent Chromium (CrVI) < 0.1%

Polybrominated Biphenyls (PBB) < 0.1%

Polybrominated Diphenyl Esters (PBDE) < 0.1%

As of July 2019, certain raw ingredients have been added to the list of restricted chemicals. Some Hapco products contain these restricted ingredients and no longer meet RoHS requirements; however, the majority of our product line still complies. If you require a material certification for a specific Hapco product please contact us.

Toxics Use Reduction Act

Enacted in 1989 and amended most recently in 2006, The Toxics Use Reduction Act(TURA) requires Massachusetts companies that use large quantities of specific toxic chemicals to evaluate and plan for pollution prevention opportunities, implement them if practical, and annually measure and report the results. Learn more.

TURA Reporting & Fees

Each company considered a Large Quantity Toxics User is required to file an annual toxics use report for every listed chemical it manufactures, processes, or otherwise uses above applicable thresholds.

TURA Planning Requirements

A Toxics Use Reduction (TUR) Plan is a document that provides both economic and technical evaluations of the toxics use reduction opportunities available to a company, and identifies those methods if any, that the company intends to implement.

Hapco’s Status

Under the requirements of the Massachusetts Toxics Use Reduction Act (TURA), Hapco has been submitting annual chemical use reporting forms for di-isocyanates. As part of this TURA compliance program, Hapco expects to prepare a Toxics Use Reduction Plan update by July 1, 2014 aimed at reducing the use of our reportable chemicals. This TURA Plan must address the location and performance of our process equipment, and the plan must be approved by a certified Massachusetts Toxics Use Reduction Planner to assure that it demonstrates a good faith effort to identify toxic use reduction options and it meets the requirements of the Massachusetts Department of Environmental Protection.

Potting and Encapsulation Using Urethanes and Epoxies

Potting consists of immersing the part or assembly in a liquid resin, and then curing it. Although often confused for each other, potting is different from encapsulation in that it retains the shell that is used to contain the thermoset resin while it’s curing.

Potting Electronics with Epoxy

Encapsulation involves building a mold or frame around an object, e.g., wires, filling the space between the frame and the object with a thermosetting material such as Di-Pak™, waiting for the resin to cure, and then removing the frame.

Encapsulated Parts Polyurethane Hapco

These processes are commonly employed to protect semiconductor components from moisture and mechanical damage. They are also used in high voltage products to allow live parts to be placed much closer together, so that the product can be smaller. They keep dirt and conductive contaminants such as impure water out of sensitive areas and serve as structural reinforcement, protecting sonar transducers and other deep submergence items from collapsing under extreme pressure. Potting with black or opaque epoxies and polyurethanes can be used to discourage reverse engineering of proprietary products such as printed circuit modules.

Potting and Encapsulating Underwater Components