Resin is a versatile material that is commonly used in the manufacturing, construction, and art industries. Its versatility comes from its ability to adhere to a wide range of surfaces. however, as not all surfaces are compatible with resin, it is important to understand what surfaces resin does and does not stick to. 

Why Resin does not Stick to Some Materials

The reason that resin sticks to some materials and not others depends on several factors, including the surface energy, porosity, chemical and physical properties of both the resin and the surface, the type of resin being used, the surface it’s being applied to, and the environmental conditions in which the work upon resin is being done.

Materials with a low surface energy, such as some types of silicone and Teflon, tend to have poor adhesion to resin because it cannot form a strong bond with the material. The porosity of the material can also affect the ability of resin to stick to it. Resin is less likely to adhere well to materials such as paper or wood, as it can penetrate into the pores of the material and weaken the bond.

Importance of Understanding What Resin doesn’t Stick to

It is important to understand what surfaces resin does not stick to because a weak bond can result in the resin peeling or flaking off the surface, potentially ruining your project. By selecting the right surface and preparing it properly, the bond between resin and the surface can be improved, ensuring a strong and lasting adhesion.

This is why it is important to understand the properties of the materials being used and to take the necessary steps to improve adhesion, such as cleaning and degreasing the surface, and using a primer designed for resin when creating any project.

Surfaces Resin does not Stick to

• Oil or Wax-treated Surfaces

Surfaces that have been treated with oil or wax are not receptive to resin and can cause it to peel. These treatments create a barrier that prevents the resin from adhering to the surface.

• Powder-coated Surfaces

Powder-coated surfaces, such as those found on outdoor furniture, are not receptive to resin and can cause it to peel or crack as well. Powder coating creates a smooth surface that does not allow resin to penetrate and create bond.

• Dusty or Dirty Surfaces

Resin may not adhere well to surfaces that are not thoroughly cleaned and free of dust, dirt, or other contaminants.

• Pure Metals

Resin does not typically stick well to pure metals because these metals are very smooth and non-porous, providing little surface area for resin to adhere to. Pure metals often have a naturally occurring oxide layer on their surface as well that acts as a barrier, preventing resin from making a strong bond.

• Most Plastics

Some plastics, such as polyethylene, polypropylene, vinyl, and PTFE, are not compatible with resin and can cause it to peel or crack. These plastics are often used in applications that require resistance to chemicals and UV light, which can weaken the bond of resin.

• Polyethylene and Polypropylene Plastics

Polyethylene and polypropylene plastics have a non-polar molecular structure which makes them resistant to adhesion by most resins. 

• Vinyl

Resin and vinyl are two different materials with different chemical compositions and properties, and as a result, they may not adhere well to each other without proper preparation or treatment.

• PTFE or Teflon

PTFE, or Teflon, is known for its non-reactive, non-stick, and almost friction-less surface that does not allow resin to adhere to it, making it difficult to bond. This material is commonly used in cookware, and any attempt to bond resin to it will result in a weak and unsustainable bond. Hence, it is often used as a release surface for resin casting.

• Polystyrene

Polystyrene is a type of plastic that is hydrophobic as it repels water. Resin, on the other hand, is a water-based substance that requires a porous surface to bond properly. Polystyrene is also a non-porous material, which makes it difficult for resin to penetrate the surface and form a strong bond.

• Silicone

Silicone has a natural resistance to adhesion, and nothing sticks to it except for silicone itself. This makes it a popular choice for applications where a flexible and non-stick surface is required such as silicone molds for resin projects.

• Certain Types of Fabrics

Fabrics, such as those that have been treated with water-resistant or stain-resistant treatments, can cause resin to come off. These treatments change the surface of the fabric, making it difficult for resin to adhere.

• Parchment, Wax, and Freezer Paper

Parchment, wax, and freezer paper have low surface energy, making it difficult for resin to bond with them. Parchment is made from animal skin, while wax and freezer paper are treated with substances such as wax or silicone that can act as a barrier between the resin and the material, preventing a strong bond from forming. The slippery nature of wax and some treatments on freezer paper can also make it difficult for resin to grip and form a strong bond.

• Painter’s Tape and Sheathing Tape

Painter’s tape and sheathing tape are designed to be easily removable, and the bond between the tape and the surface it’s applied to is not strong enough to support the weight of resin.

• Rubber

Rubber has a natural resistance to adhesion, and resin will not stick to it. This makes it a popular choice for applications that require a flexible and durable surface.

• PVA

PVA, or polyvinyl alcohol, is commonly used as a release agent for resin casting and prevents adhesion due to its slippery surface.

• Acrylic Plastic

Resin and acrylic plastic are chemically dissimilar materials and therefore do not bond well with each other. Acrylic plastic also has a smooth surface that doesn't provide a good surface for the resin to adhere to. The resin may form a weak bond with the surface, but it will not create a strong and durable bond. Acrylic plastic also has a high level of surface energy, making it difficult for resins to establish a strong bond with its surface.

• PVC

PVC, or polyvinyl chloride, has a smooth surface that makes it difficult for resins to grip and adhere to it. PVC can also easily be contaminated by dust, oils, or other substances, which can act as a barrier between the resin and the material, preventing a strong bond from forming.

• ABS Plastic

ABS plastic, also called as Acrylonitrile Butadiene Styrene, is known for its low adhesion and contains polymers with a low surface energy, making it difficult for resin to bond with it. So, it is commonly used in applications where high strength is required.

• Polycarbonate (Most Plastic Containers)

Polycarbonate is a type of plastic that is known to be difficult to bond due to its smooth, non-porous surface. This makes it difficult for adhesives, including resins, to adhere properly. Additionally, polycarbonate can have a low surface energy, which can reduce the effectiveness of adhesion.

• Plastic Bags

Plastic bags, including sandwich bags, are made of low surface energy materials, which makes it difficult for resins to establish a bond with them.

• Hot Glue

Resin and hot glue have different chemical compositions and cure differently, which can make it difficult for resin to adhere to hot glue. Hot glue is also a thermoplastic polymer that melts and solidifies when cooled, while resin is typically an epoxy-based material that cures through a chemical reaction. Furthermore, the surface of hot glue can be slick and non-porous, which can prevent the resin from bonding properly. Additionally, hot glue can release gases as it cures, which can cause bubbles to form in the resin and weaken the bond.

• Silicone Sealant Caulk

Silicone sealant caulk is a non-stick material that is used for sealing and bonding applications but is not suitable for use with resins.

• Plexiglass

Resin and plexiglass can be difficult to bond because plexiglass lacks surface texture or roughness that makes it challenging for resin to grip onto the plexiglass, causing it to slide off or not adhere at all. Additionally, plexiglass often has a release agent applied to its surface during manufacturing to prevent it from sticking to the mold used to create it. This release agent can also prevent resin from adhering to the surface of the plexiglass.

Tips for Improving Adhesion

Surface Preparation

Sufficient surface preparation is crucial for ensuring that resin sticks to a surface properly. Cleaning and degreasing the surface is essential to remove any oils, waxes, or other substances that can prevent the resin from bonding. Roughening smooth surfaces can also help improve adhesion.

Using a Primer

Using a primer specifically designed for resin can improve its adhesion. These primers are designed to promote adhesion by creating a rough surface that allows resin to penetrate and create a strong bond.

Before using resin, it's always a good idea to do a small test to see if it will adhere properly to the surface you are working with. It is also important to thoroughly clean and prepare surfaces prior to applying resin as it proves to be of utmost importance for creating successful resin projects.