Polyvinyl chloride (PVC) is one of the most widely used thermoplastic materials in our daily life due to its special feature of durability , versatility and cost-effectiveness . PVC material are commonly used in various industries, from wire insulation to flooring, pipes, and profile etc. It is also widely used in automotive parts, furniture, and consumer goods like credit cards and artificial leather
However, when it comes to processing PVC on two roll mixing mills, temperature control is one crucial factor that we need to consider .
Different from natural rubber ,elastomer or other thermoplastics, PVC is highly sensitive to heat — just a small temperature rise can cause degradation, color change, or even release of hydrogen chloride gas..
Therefore , without proper cooling , it can degrade rapidly during mixing process, which would release harmful gases and ruining the material quality.
That’s why on the process of PVC compound in laboratory , it is very essential to equip water cooling system to control temperature , so that achieve stable processing, high-quality compounds, and safe operation.
1. Why PVC Needs Strict Temperature Control
To process PVC material , the processing temperature window is very narrow
Around 80–110 °C, PVC material starts to soften and mix ; If it is above 140–160 °C , it then begins to decompose and release hydrogen chloride (HCl) gas if not properly stabilized.
During milling on a two roll mill, mechanical shearing generates a large amount of frictional heat .
If the roll temperature rises too high ,it would cause several result ,such as:
* Yellowing or browning of PVC compound
* Loss of physical properties
* Strong odor or HCl fumes
* Poor dispersion and rough sheet surface
To avoid this, a proper cooling water circulation inside the rolls keeps the surface temperature stable, usually around 20–60 °C, preventing such thermal degradation — this is only possible with an efficient water cooling system.
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2. How the Water Cooling System Works
Uniform temperature across both rolls is essential for two roll mill to knead, blend, and homogenize the PVC compound. As it can ensure several good result ,for example Consistent melting and softening of PVC powder , Even distribution of stabilizers, plasticizers, and fillers and Uniform sheet thickness and texture
Basically , a two roll mill for PVC processing features as follows:
* Hollow rolls with internal channels or spiral passages
* Water inlet and outlet ports for continuous circulation
* Thermostatic water control unit or chiller to maintain a stable set temperature (usually 20–60 °C)
When the cold water enters the roll, it absorbs the heat generated by mixing process and that generated by friction action and take away the exssive heat away.
This continuous heat exchange keeps the roll surface temperature uniform and low, preventing PVC from overheating.
If without water cooling, one side of the roll could overheat, resulting in uneven gelation and inconsistent product quality.
3. Benefits of Water Cooling for PVC Compounding
Cooler rolls prevent the compound from sticking or adhere to the roll surface.
Even roll temperatures mean consistent gelation, smoother dispersion of additives, and homogeneous sheet formation — essential for lab testing or production compounding.
In addition, when rolls, bearings, and seals are kept at moderate temperatures, they last much longer.
Overheating can warp the roll surface, damage seals, and shorten the lifespan of the entire mixing mill.
Therefore , with water cooling system ,it bring several benefit as follows:
* Prevents sticking and scorching
* Makes sheet take-off easier with cleaner edges
* No HCl release , or Reduces smoke and unpleasant odors
* Enhances operator safety and laboratory cleanliness
* No yellowing or black spots
* Stable color and mechanical properties
* Extends Machine Life
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4.Typical Cooling Configurations for PVC Compounds Two Roll Mills
For PVC processing , a quality PVC two roll mill usually includes:
* Material of rolls: High-chrome or nickel-plated steel with polished surface
* Hollow rolls with spiral or axial water channels inside
Water inlet and outlet ports for each roll
* Temperature sensors to monitor roll surface temperature
* Thermostatic water circulator or chiller for precise control
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5. Water Cooling System Details
For these material which are sensitive to heat , like PVC etc ,it is better to consider a chilled circulating unit but not tap water to keep temperature stable under heavy shear and knead action.
* Water-filled hollow rolls with internal channels (standard).
* Chilled water or temperature-controlled circulator (chiller or thermostatic unit) to control inlet temperature and remove process heat.
* Temperature sensors (thermocouples) embedded in or on the roll to monitor surface temperature. Prefer a closed-loop controller for safety.
In laboratory applications, users often set roll surface temperatures between 25 °C and 50 °C, depending on the PVC formulation.
This combination ensures stable operation and consistent material properties for every batch.
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In conclusion , since PVC is sensitive to heat , thus it is essential makes to ensure stable temperature on the process of compounding.
The water cooling system protects your compound from thermal degradation, stabilizes your mixing process, and extends the lifetime of your equipment.
A two roll mill with an efficient cooling system ensures smooth processing, better material quality, and a longer-lasting machine.
No matter you are this two roll mill machine for laboratory or production plant, investing in a two roll mill with efficient water cooling system ensures consistent PVC quality, safer working conditions, and more reliable operation for over years.
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