Heat Sealer 101 Basics and Benefits

Heat-sealed packaging offers protection and preservation for various products by securely bonding two ends together to create a sealed enclosure. With the right materials, this process ensures durability and reliability. There are numerous types and configurations of heat sealers available. This guide explores the fundamentals of heat-sealed packaging, its different variations, key benefits, and best practices for optimal use.

Certain polymers are thermo-reactive, meaning they change shape and form when exposed to high temperatures. Commonly used in bags and packaging, materials like polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) can be fused together when heated to approximately 140°F. This process, known as heat sealing, involves applying heat and pressure to bond two layers into a secure seal.  

The choice of sealer depends on factors such as the type of polymer, its thickness, and the required production volume.

The type of sealer used depends on the polymer material being sealed, its thickness, and desired production levels. Heat-sealed packaging is quick, efficient, and perfect for high-speed operations. It also provides all-around coverage and complete enclosure of individual or multi-product packs.

As a packaging application, heat sealing has fewer initial investment requirements and is more cost-effective than other forms.

Do You Need a Heat Sealer for Shrink Wrap?  

Heat sealers are essential in the shrink-wrapping process, ensuring that the plastic film fully encloses the contents before heat is applied. To create a secure wrap, the film must be sealed shut, transforming a flat sheet into a bag-like enclosure or closing an open bag. Shrink wrap seals are typically thinner compared to those used for thicker packaging materials.  

However, not all shrink wrap applications require a heat sealer. Processes like shrink banding and shrink sleeves, which are used for branding or tamper-evidence rather than full enclosure, do not require sealing to apply the material.

What Temperature is Needed to Heat Seal Products?  

The required heat-sealing temperature varies depending on the type and thickness of the thermo-reactive plastic being used. To achieve a strong, secure seal, the sealing machine must reach the appropriate temperature for the specific material.  

- Polyolefin shrinks at 280–350°F (138–177°C).  

- Polyethylene (PE) seals at approximately 140°F (60°C).  

- Polypropylene (PP) requires a sealing temperature of 248–253°F (120–123°C).  

In addition to temperature, seal time and cooldown play a crucial role in achieving a durable seal. Thicker films and bags typically require higher temperatures and longer sealing and cooling periods to ensure proper adhesion.

Can You Use Any Bag with a Heat Sealer?  

While most plastic bags are thermo-reactive and can technically be heat-sealed, not all are designed for this purpose. Different plastics have varying melting points, and some materials are not mendable, meaning they may melt excessively or fail to form a proper seal. Using non-sealable plastics can compromise packaging integrity and safety, resulting in an unattractive or ineffective seal.  

To ensure safe and effective sealing, always use heat seal-approved packaging. The material must be mendable, allowing the heat-sealing process to create a secure and durable bond without burning or damaging the product inside.  

Beyond sealability, consider whether the bag meets functional requirements. Factors such as thickness, oxygen barrier properties, anti-static features, and resealability can impact performance. The type of plastic used will significantly affect the final result after heat sealing.

Which Heat Sealer Is Best?  

There are various types of heat sealers, including impulse sealers (L-bar and I-bar sealers), constant heat sealers, foot switch-operated sealers, and direct sealers. The best choice depends on the specific needs of your project.  

Key Factors to Consider:  

- Size & Portability – Compact, portable machines work well for small-scale or individual projects.  

- Energy Usage – Some sealers require more power than others, impacting cost and efficiency.  

- Volume & Durability – High-volume operations benefit from heavy-duty, long-lasting sealers.  

- Material Type & Thickness – Thin seals with rounded edges work best for shrink wrap, while thicker materials require a flat seal for added flexibility and spill prevention. 

- Cost – Balancing budget and performance is essential for choosing the right machine.  

Sealer Types & Best Uses:  

- L-Bar & I-Bar Sealers – Ideal for shrink-wrapping projects, creating a secure seal before the film is shrunk down.  

- Constant Heat Sealers – Durable and cost-effective for high-volume production, capable of handling higher-grade materials.  

- Flat Wire Seals – Can be ¼ to 2 inches thick, providing extra strength for heavy-duty packaging.  

- Round Wire Seals – Typically around 1 inch thick, commonly used for shrink wrap applications.  

What Are the Different Types of Heat Sealers?

Heat sealers come in various types, each with its own unique features, benefits, and potential drawbacks. Here's a breakdown of the main categories:

1. Impulse Heat Sealers: These are among the most common heat sealers. They feature one or two heating elements covered with Teflon tape to prevent polymers from sticking. The elements are pressed together over the seal, and a microswitch activates the heat. Importantly, heat is not applied while the bar is open, which helps reduce the risk of accidental burns. Impulse sealers are typically more affordable and safe, with sealing times usually lasting around two seconds.

2. Foot Operated Sealer (PSB): Typically mounted on desks, these sealers are activated using a foot pedal. They can be programmed to open and close at specific intervals, making them ideal for high-volume sealing operations, often used on factory conveyor belts for continuous output.

3. Direct Heat Sealer (PSF): Also known as constant heat sealers, these devices can be pre-programmed to heat to different temperatures, which is ideal for sealing various types of plastic bags with different melting points. They offer a stronger, more durable seal—typically around 10mm—providing additional protection for packages during transport.

4. Continuous Motion Sealers: These sealers feature continuous sealing ribbons and are designed for high-speed applications. They can seal light to medium-thickness bags as they move along a conveyor belt, making them ideal for fast-paced environments where large quantities of seals are required.

Which Is the Most Durable Sealer?

The durability of a sealer mainly depends on the quality of its sealing blade. Impulse sealing blades, especially thinner ones, can wear out quickly. More durable options, like hot knife or constant heat sealers with wider sealing bands, can last for hundreds of thousands of seals with proper maintenance.

What Is the Difference Between Impulse and Constant Heat Sealers?

Impulse heat sealers use short heat pulses for a few seconds, while constant heat sealers provide continuous heat. Constant heat sealers are better for sealing thicker materials but come with a higher risk of burns due to continuous heat. Impulse sealers are ideal for lower production and lighter materials.

Is a Heat Sealer the Same as a Vacuum Sealer?

Heat sealers only seal the bag, while vacuum sealers remove air before sealing, making them ideal for preserving perishables like food. The absence of oxygen in vacuum-sealed bags extends shelf life.