A heat sealer is a device that uses heat and pressure to bond thermoplastic materials, creating a strong, airtight seal for packaging. It works by fusing layers of plastic, such as polyethylene (PE) and polypropylene (PP), together to protect contents from moisture, dust, and contamination. These sealers are used across industries like food, medical, and electronics, with options ranging from simple, manual tabletop models to large, automated industrial machines.