Sometimes what you need is a little bit more than just epoxy. That’s why Arlon 55NT manufactures both epoxy and aramid laminates and prepreg. What’s the difference?
Epoxy is an adhesive commonly used to create a tough, durable surface for aircraft or other vehicles. We make Epoxies by mixing two different types of material under high pressure for the combined materials to form a thick liquid. Then we form it into a layer and allow it to harden (sometimes over several days). Its strength comes from how well it bonds various objects. One of the reasons aramid laminates are so popular is because they consist of a polymer called aramid. It has excellent tensile strength and high elongation. We use it as an industrial strengthening material for many years. We can also use it to make composite materials such as body armor.
Lately, Rayming PCB & Assembly have been combining the properties of epoxies and aramids. This helps to strengthen their products. We lay the layers onto each other to create stronger parts or coatings that are impossible with other products. These laminates can form into complex shapes and provide exciting properties.
The word “prepreg” is short for “preform,” meaning a prototype. When a firm creates a prototype, it usually needs to make the product in several pieces. We then fit them together to make one complete model. Finally, the “preform” is cut and shaped into the model so that we can assemble it with minimal material waste. This also allows the company to test out different parts at once. Also, they check how they work with each other without waiting for their manufacture.
Identification & Functionality
The Arlon 55NT epoxy and aramid laminates are a product of the same technology. The main difference is in the resin, which we use to strengthen the laminate. The epoxies usually use a combination of resins called polyphenethylenesulfides (PPS). As a result, they form hard films that can withstand a wide range of temperatures. These are also known as cross-linked polyphenylene sulfides (XPS). However, due to environmental concerns, they no longer manufacture them in large quantities.
Epoxy & Epoxy Derivatives is the chemical family that includes:
Polyphenylenesulfide is a chemical that does not contain nitrogen. Instead, it is a polymer made from phenyl groups connected to carbon atoms, with sulfide groups attached to each phenyl group. We can form PPS into various shapes, and it is often helpful as a surface coating on items like aircraft.
In addition to the uses mentioned above, PPS has many other applications. For example, it can help as a barrier material in medicine. They also work as insulation in textiles or as an adhesive material in cosmetics and personal care products. PPS is also effective for closing cellulose triacetate film tubes. This is because of its stiffness and good chemical resistance.
Composite Materials Functions:
Arlon 55NT manufactures prepreg as well as epoxy and aramid laminates. Prepreg is a laminate made of unidirectional fabric impregnated with resin. Arlon 55NT can produce a wide range of prepregs using the same manufacturing technology. Then they process them to create epoxy and aramid laminates. The difference is in the resin (the material used to strengthen the lamination).
The basic resin used in prepregs is polyester. However, Arlon 55NT can also make prepregs with other resins as needed.
Preforms are strong and hard. They are polyester that you impregnate with resin, which is then dried under high pressure so that the resin stays in place. When the material reaches room temperature, it shrinks and becomes one solid piece that is extremely hard to break or damage. The finished preform is ready for use as a coating. For example, they use it to coat an aircraft wing or other vehicle parts.
The Kevlar (Aramid) prepreg consists of a very strong material that is easy to cut and bend but not as easy to tear or break. This is the most used prepreg because we can form it into complex shapes.
The preform is formed by layering and rolling the fabric together. Next, we heat each textile layer to a high temperature and press under extremely high pressure. The pressure and heat combine to form the resin, which hardens into a strong and tough material that we can cut and shape easily by hand.
All Arlon 55NT laminates and prepregs have similar mechanical properties. A composition of resin and cloth forms a laminate with relatively high strength. However, we can rapidly cut it using hand tools.
1. Tensile Strength:
The strength of the laminate is dependent on several factors. It includes the resin composition, the type and amount of cloth used in the laminate, and how well the layers bond together. When properly bonded together, each layer has a 50% tensile strength. When we laminate two layers together, they have a 40% tensile strength. We can find these values on any product datasheet.
2. Flexural Strength:
These tests are usually done on 10–20 cm long samples to simulate a cross-section of the product. Flexural strength can resist bending, such as when a bike frame or an airplane wing bends while under pressure. The no-load strength is the maximum force (in N/mm) that a material can withstand under bending stress before it fails. It measures how much a material can bend and remain unbroken. Compression stress on the laminate has little effect on flexural strength.
3. Young’s Modulus:
Young’s modulus is a value that measures stiffness. It relates to tensile strength and flexural strength. It is often used in aircraft design to indicate how strong the material will be after bending it into an airfoil.
4. Peel Strength to Copper:
This measures how well the laminate will resist shear force. This is when we apply pressure to one side of the laminate against an object like copper. The peel strength to copper depends on the thickness of the lamination, the amount and type of cloth used, and the layers it has.
5. Shear Strength:
Shear strength and peel strength measure how well a material resists stretching. Similar to flexural strength, we can do shear tests on samples about 10–20 cm long to simulate a cross-section of the finished product.
1. Water Absorption (0.062%):
Water absorption is the amount absorbed into the material in an air-dry setting for at least 12 hours. It measures how much moisture a lamination can absorb before it affects the strength and performance of the material.
2. Specific Gravity:
It measures the density of a material. Specific gravity is the ratio of weight to volume, and it indicates how dense or low the density of a material is. We measure it either with a hydrometer or an electronic balance.
1. Thermal Conductivity:
This property measures how well heat can travel from one side of a laminate to the other. We measure it with a commercial infrared thermometer. It simulates heat moves along with the lamination under different temperatures and laminates. Infrared thermometers provide an accurate reading of the feet’ temperature. Therefore, it is essential for aircraft design.
It measures the amount of heat (in degrees Celsius) needed to evaporate a layer of resin applied in an air-dry setting to form a laminate. Tg also measures how fast the material loses its properties when it reaches certain temperatures.
Tm is the temperature at which a material loses its strength when exposed to water for long periods.
1. Arc Resistance:
Arc resistance measures how well a material conducts electricity. We measure it with a UV light that simulates how electricity moves through the material in different temperatures.
2. Dielectric Constant:
Dielectric constant measures a material’s ability to store an electric charge. When we place materials between two conductors, copper and plastic, they can store an electrical charge. It releases it simultaneously under alternating current (AC). This constant measures how the material can store much energy while remaining microscopic. A higher dielectric constant means that we can store more energy in the material during AC discharges.
3. Electrical Strength:
Electrical strength measures the amount of charge stored in a material by a capacitor. Different materials have different electrical strengths. We measure this using an electrostatic generator on the bottom side of the laminate under alternating current.
Finally, these two items are different in scale, meaning the material and thickness. Prepreg is much thinner than an aramid film and much heavier than epoxy. Arlon 55NT has been exploring ways to bring these two types of materials better together.