Plastics are integral to modern manufacturing, valued for their lightweight properties, durability, and adaptability. Yet, their unique physical characteristics—such as a tendency to flex, expand, and contract—present a significant challenge when a flexible, durable seal is required. For manufacturers and professionals, selecting the right sealant is not just about stopping a leak; it’s about ensuring the long-term reliability and performance of an assembly.

While many adhesives and sealants exist, the “best” one is determined by the specific demands of the plastic and the application itself. This guide will clarify the different types of flexible sealants and provide key insights into choosing a solution that is engineered for lasting success.

The Two-Fold Challenge: Surface and Flexibility

Plastics can be categorized into two main groups based on their surface energy, which dictates how easily a sealant will adhere.

• High Surface Energy (HSE) Plastics: These materials, such as ABS, PVC, and polycarbonate, are relatively receptive to adhesives and sealants. They are the easier of the two to bond and seal.
• Low Surface Energy (LSE) Plastics: This group includes common materials like polyethylene (PE) and polypropylene (PP). Their slick, non-porous surfaces make them notoriously difficult to bond. A specialized sealant or a primer is almost always required to achieve a durable seal.

Furthermore, a flexible plastic assembly needs a sealant that can move with it. A rigid sealant will crack and fail under thermal expansion, vibration, and impact. The key is to find a solution that remains elastic and maintains its bond under dynamic stress.

Common Sealant Types and Their Properties

The industry offers several types of sealants designed to address these challenges. The choice often comes down to balancing strength, flexibility, and application method.

• Silicone Sealants: These are the most widely recognized flexible sealants. They are known for their high elasticity, resistance to extreme temperatures, and excellent UV resistance. Silicone’s flexibility makes it ideal for joints that will experience significant movement. For plastics, it is essential to use a neutral-cure silicone to prevent the release of corrosive byproducts that could damage the substrate.
• Polyurethane Sealants: These provide a strong, flexible bond with excellent abrasion resistance. They are often a top choice for heavy-duty industrial applications where a combination of strength and flexibility is required. However, they may be more challenging to apply and can be sensitive to moisture during the curing process.

For many projects, these sealants are effective, but they can be limited by long curing times and their inability to provide a truly structural bond on a rapid assembly line.

A Modern Solution: UV-Curing Adhesives and Sealants

For manufacturers seeking a fast, high-performance solution, UV-curing adhesives and sealants offer a significant advantage. These single-component materials cure in seconds when exposed to a specific wavelength of UV light, providing on-demand bonding and sealing.

While many UV-curing adhesives are known for their rigid bonds, specialized formulations are designed with a high degree of flexibility. These products, measured by their elongation percentage, can be tailored to match the specific movement requirements of the plastic they are sealing.

How Incure Can Help Professionals

Incure’s portfolio of adhesives includes advanced UV-curing solutions specifically engineered for plastics. For projects requiring a flexible, yet robust seal, our products offer a unique blend of properties:

• On-Demand Curing: The fast curing time significantly accelerates production, reduces work-in-progress, and eliminates the need for clamping or jigs.
• Tailored Flexibility: Our UV-curing formulations are available with a wide range of elongation values, from products with minimal flexibility to those that can stretch significantly without compromising the seal. This allows for precise material selection based on the specific movement and stress a joint will endure.
• Superior Adhesion: We offer products formulated to bond to a wide variety of plastics, including difficult-to-bond LSE plastics, ensuring a reliable and long-lasting seal.
• Optical Clarity: Many of our UV-curing adhesives cure transparently, making them ideal for applications in medical devices, consumer electronics, and other products where a clean, invisible bond is critical.

By choosing a solution from our line of UV-curing products, professionals can achieve a level of control, speed, and reliability that traditional sealants simply cannot match. For a deeper understanding of how our technology can be tailored to your specific project needs, or to learn more about our flexible sealing solutions for plastics, connect with an Incure specialist.