An Overview of Melt Pressure Measurement Technologies in Polymer Processing

Dynisco

10.09.2025

An Overview of Melt Pressure Measurement Technologies in Polymer Processing

Pressure is a key parameter in polymer processing, influencing dimensional stability, throughput efficiency, and equipment safety. Whether the process involves extrusion, molding, or compounding, precise melt pressure monitoring ensures product quality and operational reliability.

At Dynisco, we have over six decades of expertise in melt pressure sensing. From early mechanical gauges to modern digital sensors, our innovations have shaped the way processors monitor this critical variable. This article outlines the key melt pressure measurement technologies available today, including traditional strain-gauge sensors, mercury-free options, and fill-free capacitance-based designs.

From Analog Gauges to Electronic Strain-Gauge Transducers

Historical Evolution

• Mechanical pressure gauges and hydraulic transducers were standard on early extrusion lines.
• These tools offered basic safety feedback but lacked the precision and digital outputs needed for modern automation.

The Strain-Gauge Breakthrough

• Strain-gauge melt pressure transducers introduced electronic signal output.
• They use a diaphragm and fill fluid to transmit melt pressure to a strain gauge.
• This enabled closed-loop process control, marking a significant step toward automation.

This foundational design remains central to many current pressure sensors.

Moving Beyond Mercury: Alternative Fill Fluids

While mercury has been favored for its thermal stability and pressure fidelity, evolving health and environmental regulations have prompted the development of safer alternatives. Dynisco offers several non-mercury fill options:

Fill Fluid Alternatives

• HTF (High Temperature Fluid): A sustainable, mercury-free fill with stability up to 350°C. Ideal for general polymer extrusion.
• NaK (Sodium-Potassium Alloy): Suited for high-temperature applications (up to ~530°C), including PEEK and fluoropolymer processing.
• Food-Grade Oil: FDA-approved for food and medical extrusion, ensuring regulatory compliance without contamination risk.

These fills allow processors to align sensor choice with process temperature, compliance requirements, and environmental priorities.

Fill-Free Capacitance Sensors: The Vertex® Innovation

Some applications demand a fluid-free solution. The Vertex® Series eliminates fill fluids entirely by employing capacitance-based technology.

Vertex Benefits

• No contamination risk: Ideal for sensitive applications in food and medical sectors.
• High accuracy: ±0.25% full scale.
• Rapid response: Critical for detecting transient pressure variations.
• Sustainability: Longer lifespan, no hazardous materials, and less sensor waste.

Vertex sensors represent a leap forward in combining safety, performance, and environmental stewardship.

Dynisco Sensor Families: Purpose-Built for Diverse Needs

Dynisco organizes its melt pressure solutions into specialized sensor families, each engineered for specific use cases:

• SPX Series: Versatile strain-gauge sensors with configurable fill options (HTF, NaK, oil, mercury). Designed for durability and digital integration.
• Vertex®: Capacitance-based, fill-free sensors optimized for high-purity, high-safety applications.
• PTX/MDX (BenchMark™): Economical strain-gauge models offering dependable accuracy for standard extrusion lines.
• ECHO: Budget-friendly sensors for non-critical applications requiring basic performance.
• Guardian Options: Safety-enhanced versions that trigger alarms or shut down processes when pressure thresholds are exceeded.

These sensor families enable processors to balance accuracy, regulatory compliance, durability, and budget constraints.

Application-Specific Use Cases

Melt pressure measurement technologies are widely deployed across polymer sectors:

• Blown Film Extrusion: SPX or ECHO sensors ensure uniform gauge and pressure stability.
• Medical Extrusion: Vertex or food-grade oil sensors provide contamination-free pressure monitoring.
• High-Temperature Polymers: NaK-filled SPX sensors deliver stable readings under extreme thermal loads.
• Food Packaging: Oil-filled sensors meet FDA standards while ensuring extrusion quality.

Accurate pressure monitoring in these applications reduces scrap, improves throughput, and enhances product consistency.

Future Trends in Melt Pressure Technology

Innovation continues to drive the field forward. Emerging trends include:

• Mercury-free standardization: Regulatory and environmental pressure is accelerating adoption of safer fill alternatives.

• Fill-free expansion: Capacitance sensors like Vertex will gain traction in safety-critical and sustainable applications.

• Digital integration: Enhanced connectivity with plant MES, SCADA, and cloud platforms for real-time analytics.

• Predictive diagnostics: Embedded sensor intelligence to detect anomalies and preempt failures.

• Rebuildable designs: Extended service life through user-serviceable components.

Dynisco remains committed to meeting the industry's growing demands for performance, compliance, and sustainability.

Conclusion

Melt pressure sensing has evolved from analog gauges to a sophisticated portfolio of digital, accurate, and safe sensors. With solutions ranging from high-temperature NaK-filled transducers to fill-free Vertex® technology, Dynisco offers a tailored approach for every polymer process.

Our sensor families — SPX, Vertex, PTX, MDX, and ECHO — reflect our commitment to innovation, reliability, and regulatory readiness. With each advancement, we aim to provide processors with greater insight, higher safety, and increased operational control.

Accurate pressure data isn’t just a number; it's a strategic asset. When measured precisely and interpreted correctly, it empowers manufacturers to minimize risk, improve yield, and future-proof their operations. Contact us today if you have any questions not answered below.

FAQs

What is the difference between fill and fill-free melt pressure sensors?

Fill sensors use fluids like mercury, HTF, or NaK to transmit pressure to a strain gauge. Fill-free sensors (e.g., Vertex) use capacitance-based measurement with no internal fluid, eliminating contamination risk and improving response.

When should I use a NaK-filled sensor instead of HTF?

Use NaK-filled sensors for very high-temperature processes (above 350°C), such as those involving engineering polymers like PEEK. HTF is better suited for general extrusion applications with lower temperature requirements.

Why choose a fill-free sensor?

Fill-free sensors eliminate the risk of contamination and reduce maintenance. They are ideal for food, medical, or environmentally sensitive applications requiring high accuracy and safety.