what is ultrasonic welding plastic

Ultrasonic technology can be used for welding plastics, metals, and composite materials, which has gradually been understood by most people. Ultrasonic welding of plastics is a cold welding process that uses the piezoelectric effect of piezoelectric ceramics to convert electrical energy into ultrasonic waves and uses the high-frequency vibration of ultrasonic waves to weld thermoplastic plastics.

Rotary Ultrasonic Welding process
ultrasonic plastic welding process gif

how does ultrasonic plastic welding work

Ultrasonic welding converts electrical energy into acoustic energy through the piezoelectric effect of ceramic plates. The ultrasonic waves are transmitted to the plastic parts via a welding horn, causing high-frequency vibrations. During these high-frequency vibrations, the temperature of the plastic parts rises to the glass transition temperature or melting point, causing the molecular chains of the plastic to start moving and recombining. Finally, applying pressure and cooling achieves a welding effect with a strength comparable to that of the raw material.

advantages of ultrasonic welding plastic

  • High Efficiency: Short welding time (0.1–2 seconds), suitable for automated production lines.
  • Clean Process: No need for solders or solvents, eliminating chemical contamination.
  • Precision: Welding area can be controlled to millimeter-level accuracy, with no obvious surface damage.
  • Energy Saving: Energy consumption is only 30–50% of traditional thermal welding processes.
  • Excellent sealing: It can achieve good air tightness and water tightness, extend the shelf life of the product, and prevent chemical oxidation.

what materials can be ultrasonically welded

Ultrasonic welding applies to most thermoplastics（PP、PE、ABS、PS、PC, etc）, which are categorized into amorphous plastics and semi-crystalline plastics. These two types require different welding conditions:
  • Amorphous Plastics (e.g., PS, PC, PMMA):
    When heated by high-frequency vibrations to their glass transition temperature (Tg), the molecular chains within the plastic start to slide and recombine. After cooling under pressure, a new molecular structure forms, achieving the welding effect.
  • Semi-Crystalline Plastics (e.g., PE, PP, PA (Nylon)):
    Semi-crystalline plastics have both amorphous and crystalline regions. The amorphous regions allow molecular movement at the glass transition temperature (Tg), while the crystalline regions require heating to their melting point (Tm) for melting and welding. However, rapid cooling after melting may reduce weld strength due to crystalline shrinkage. Therefore, higher ultrasonic amplitudes or specialized energy-directing structures are typically needed to concentrate heat and ensure optimal welding results.

Common plastics that can be welded and their properties

Polypropylene (PP)

PP can be ultrasonically welded. PP, a semi-crystalline thermoplastic, is highly suitable for ultrasonic welding. Its chemical resistance and flexibility make it a popular choice in packaging, automotive, and consumer goods industries. Welding requirements: PP’s semi-crystalline structure allows for efficient heat generation during the welding process. However, material thickness and joint design play crucial roles. Custom-tailored welding strategies are often needed for complex PP components.

PP plastic
pvc plastic
Polyvinyl Chloride (PVC)
PVC can be ultrasonically welded. Yes, with precautions. PVC offers excellent mechanical strength and fire resistance, but its chlorine content means overheating can release harmful gases. Welding requirements: Specialized techniques are required to control heat generation and ensure safety. Surface preparation is also key to achieving a strong bond. Unsure how to safely weld PVC? 
Acrylonitrile Butadiene Styrene (ABS)
ABS can be ultrasonically welded. Absolutely. ABS is known for its impact resistance and ease of processing, making it a staple in electronics and automotive manufacturing. Welding requirements: Pure ABS welds well, but composites like ABS with glass fiber (GF) pose challenges. The presence of GF disrupts ultrasonic energy transmission, demanding advanced welding approaches. 
 
abs plastic
Polytetrafluoroethylene (PTFE)
PTFE can be ultrasonically welded, but it’s complex. PTFE’s non-stick and chemically inert properties, along with its high melting point (327°C) and low surface energy, make welding difficult. Welding requirements: Surface pretreatment, such as plasma treatment or chemical etching, is essential. Customized ultrasonic equipment and precise control over the welding process are also necessary. Struggling with PTFE welding? 

 

Materials like Polycarbonate (PC), Nylon (PA), Polyethylene (PE), Polymethyl Methacrylate (PMMA), Polyphenylene Oxide (PPO), and Ethylene-Vinyl Acetate (EVA) are all weldable with ultrasonic technology. Welding requirements vary: PC’s high melting point requires careful heat management; PA’s hygroscopic nature demands proper drying; PE’s different grades (HDPE, LDPE) have distinct welding behaviors. Curious about how to optimize ultrasonic welding for these materials? We have the expertise to help. Contact us now!

Thermoplastic Composites

Glass Fiber Reinforced Plastics: Such as PP – GF, PA – GF, etc. Glass fibers enhance performance but increase welding difficulty, requiring customized molds and parameter adjustments. They are used in the automotive and aerospace fields.

Mineral-Filled Plastics: Containing calcium carbonate, etc., these plastics improve hardness. They have little impact on ultrasonic energy transmission, and parameters are adjusted according to the filling ratio. They are applied to home appliances and pipes.

Flame – Retardant Reinforced Plastics: Flame retardants are added for fire prevention. Some affect welding, so it’s necessary to understand the composition, optimize parameters, and pay attention to volatiles. They are used in electronics and construction materials. 

Plastic Alloys: Like ABS – PC alloy, they combine multiple advantages. Welding requires comprehensive consideration of their characteristics and is used in high-end equipment and automotive interiors.

Application of Ultrasonic Welding Plastic

Ultrasonic welding plastic has been widely used in the welding of thermoplastic plastics or composite materials in fields such as medical, electronics, packaging, and automotive.

Ultrasonic welding hemodialysis components
Medical
Ultrasonic welding of door panels&interior trim panels
Automotive
Ultrasonic welding of flexible circuit boards
Electronic
Toiletries packaging
Packaging and sealing

Ultrasonic welding plastics in different industries case videos

Ultrasonic welding of plastics is highly suitable for mass production in fields such as medical, electronics, packaging, and food due to its excellent airtightness, precision, clean welding process, and fast welding time.

How to Choose Ultrasonic Plastic Welder

To select a suitable ultrasonic plastic welding machine, follow these key considerations:
  1. Material Compatibility
    First, verify if the materials to be welded are suitable for ultrasonic welding. Most thermoplastic plastics and some composite materials (requiring validation) are compatible.
  2. Welding Requirements
    Clarify product-specific welding standards, including precision, strength, and yield rate, to match the appropriate grade of ultrasonic plastic welding machine.
  3. Reliable Manufacturer
    Choose a trustworthy manufacturer (many traders and small-scale manufacturers lack reliable service and after-sales support) to conduct welding tests and validate the solution.

Hyusonic is a Chinese manufacturer of ultrasonic welding machines with 20 years of industry experience. We offer ultrasonic plastic welding machines of various grades and excellent quality. From ordinary machines for simple requirements to intelligent production lines with extremely high requirements for precision and yield, we are fully capable. As a reliable manufacturer, you can always turn to us for repair, warranty, and after-sales service.

ultrasonic plastic welding machine 8800st

Ultrasonic Plastic Welding Machine Standard Type
ST Series

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ultrasonic plastic welder 2000iq

Ultrasonic Plastic Welding Machine Intelligent Typ
iQ Series

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ultrasonic plastic welding machine-2000X-1

Ultrasonic Plastic Welding Machine High-end Type
X Series

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