High-Temperature Melt Pressure Transmitter for Plastics and Polymers

1. Why You Need It

Plastic extrusion, injection molding and rubber processing run at melt temperatures up to 350°C — conditions that destroy ordinary pressure transmitters. This melt pressure transmitter is purpose-built for molten polymer measurement, with an integrated finned heat sink (and optional water cooling) that protects the electronics from the heat, and a 17-4PH or Inconel 718 diaphragm for durability. It delivers the stable melt-pressure signal that keeps extrusion and molding processes consistent and product quality high.

2. Working Principle

A diaphragm at the process end contacts the molten polymer and transmits pressure through a filling medium (NaK or high-temperature silicone oil) to the sensing element, located behind an integrated heat-dissipation system. The finned heat sink — and optional water cooling jacket — keeps the electronics below their temperature limit while the diaphragm handles melt temperatures up to 350°C. The measured pressure is output as 4-20 mA, 0-10 V or RS485 Modbus.

3. Key Advantages

• Rated to 350°C (400°C peak)
• Integrated finned heat sink
• Optional water cooling jacket
• 17-4PH / Inconel 718 diaphragm
• NaK or silicone oil fill
• 4-20 mA / 0-10 V / RS485
• 1/2-20 UNF, M14×1.5, M18×1.5
• Flexible capillary option
• Purpose-built for polymer melt
• Stable, repeatable melt pressure

Common Pain Points & Solutions

Application Cases

Technical Specifications

FAQ

Q: What is a melt pressure transmitter?

A melt pressure transmitter is a specialized pressure sensor designed to measure the pressure of molten polymers and plastics in extrusion, injection molding and rubber processing. It is built to withstand the high temperatures (up to 350°C) and the viscous, often abrasive nature of polymer melts, providing the melt-pressure signal needed for consistent process control.

Q: How does it withstand 350°C?

The transmitter uses an integrated heat dissipation system — a finned heat sink with an optional water cooling jacket — to keep the electronics below their temperature limit while the process-end diaphragm contacts the molten polymer. The diaphragm transmits pressure through a high-temperature filling medium (NaK or silicone oil), isolating the sensor from the heat.

Q: What diaphragm materials are available?

The diaphragm is available in 17-4PH stainless steel and Inconel 718. 17-4PH provides good strength and durability for general polymer service, while Inconel 718 offers superior corrosion and high-temperature resistance for aggressive or abrasive polymer formulations.

Q: What filling medium is used?

The transmitter uses NaK (sodium-potassium alloy) or high-temperature silicone oil as the pressure-transmitting filling medium. NaK offers excellent high-temperature performance, while silicone oil is suitable for many polymer applications. The fill is selected to match the temperature and the application requirements.

Q: What output does it provide?

It provides 4-20 mA, 0-10 V and RS485 Modbus RTU outputs. The 4-20 mA loop is standard for process control, the 0-10 V suits data acquisition, and RS485 provides digital networking for multi-instrument extrusion and molding lines.

Q: What process connections are available?

Process connections include 1/2-20 UNF, M14×1.5 and M18×1.5, which are the standard melt-pressure threads used in extrusion and injection molding equipment. These connections allow the transmitter to mount directly into the extruder barrel or mold.

Q: What is the optional capillary for?

A flexible capillary with remote electronics is available for ultra-high temperature or space-constrained applications. The capillary moves the electronics further from the hot process, providing additional thermal isolation, which is useful where the standard heat sink is insufficient.

Q: Why is melt pressure measurement important?

Melt pressure is a critical process variable in extrusion and injection molding. It directly affects material flow, product density and surface quality. Stable melt-pressure measurement enables consistent product quality, reduces scrap and prevents equipment damage from overpressure or unstable flow.

Q: How is it installed?

The transmitter is mounted into the extruder barrel or mold using the standard melt-pressure thread (1/2-20 UNF, M14×1.5 or M18×1.5). The finned heat sink faces outward to dissipate heat, and the water cooling jacket (if used) is connected to a cooling water supply. The output is wired to the control system.

Q: Where is it used?

It is used in plastic extrusion, injection molding, rubber processing and polymer manufacturing. Anywhere molten polymer or rubber pressure must be measured reliably at temperatures up to 350°C, the melt pressure transmitter provides the durable, heat-protected measurement required.