In the world of polymer research and development, mixing is one of the most important and complex processes, it is a key and complex process in rubber processing, and its quality affects the quality of the product. The lab two-roll mill equipment play key role in mixing tool—especially when working with PVC (Polyvinyl Chloride) compounds. Compact, versatile, and precise, it’s widely used to knea, plasticize, and masticat small batches of material formulations. But how exactly does it work? Let’s take a closer look.
What Is a Lab Two-Roll Mill?
A open mixing mill, also known as two-roll mill, it is engineered to provide unmatched performance for blending ,masticating and kneading natural rubber,synthetic rubber , pigment , EVA , color master batch polyolefi ,composites ,plastic ,polymer or PVC pellets with various chemical materials.
The Laboratory mixing mill is a small-scale version of the industrial two-roll mixing mill, specially designed for R&D and quality control. It consists of two horizontally opposed rolls (usually made of hardened steel or chrome-plated alloy) that rotate towards each other at slightly different speeds. Due to the different speed in two roller ,it generate create the shearing action needed for mixing and blending for the material compound , ensures the perfect and uniform blending of natural and synthetic rubber with other raw materials.
Key Components
* Two Rolls: Made of chilled cast alloy iron whose hardness reach to 70HB. Heated internally with oil or electric heating for consistent temperature control. The constrution of rolls may be drilled roll, bored roll or grooved roll .
* Nip Gap: The adjustable space between this pair of rolls where compounding occurs.
* Frame, frame cap and base are welded and treated by annealing for stress relieving.
* Safety Features: Brake and emergency stop device can ensure the safety of operators , also equipped with safety covers, and overload protection.
* Control Panel: For setting roll speeds, direction, and temperature.
* Methods of adjusting roll nip: manual or electric
With Intelligent Touch Screen PLC Control System:
1. Real-time data record and export of kneading time, temperature (mixing chamber and front/rear rotors), ram pressure, current,torque and recipe code.
2. The control system can be set up to 20 mixing steps, save 20 recipe spaces.
The Working Principle for PVC Compounds
PVC is a thermoplastic with rigid or flexible properties which depends on the plasticizers and additives used. During processing, the raw material is heated, crushed, and thoroughly mixed when rolling between rolls. Basically , there are several factors affect the quality of the mixture include uneven dispersion of compounding agents, blooming, scorching, hardness fluctuations, etc., Here’s talk how the two-roll mill machine work for PVC compound as follows:
1. Preheating the Rolls
Firstly ,the two rolls are preheated to a desired temperature (typically between 150–180°C for PVC) to promote softening and homogenization.
2. Charging the PVC Compound
The PVC compound are usually fed into between the rolls as shape of dry blend or powder. As the rolls rotate, the compound material is pulled into the nip and undergoes mechanical shearing.
3. Plasticization and Mixing
* As the PVC blend is passed repeatedly through the nip:
* The material heats up due to friction and roll temperature.
* Plasticizers are absorbed.
* Additives are uniformly dispersed.
* Agglomerates are broken down.
On the mixing process ,operators can use small knives to remove the compound, fold it, and return it to the nip of two roll requently for recirculating.
4. PVC Sheeting
After sufficient mixing and plasticization about several mimuters, the PVC compound is sheeted as uniform thickness for further testing or molding. Maybe extruder or calender process .
Why Use a Lab Two-Roll Mill for PVC?
* Precise control over temperature and shear rate.
* Repeatable and consistent batch processing.
* Ideal for small batch trials and formulation comparisons.
* Provides insight into melt behavior and processability.
In conclusion , by way of using a lab two-roll mill for PVC compounding , it allows researchers and formulators to replicate real-world mixing on a lab scale. The lab two roll equipment helps in optimizing recipes, testing new stabilizers or plasticizers, and ensuring consistent quality—before scaling up to production.
If you’re working in PVC development or QC, the lab two-roll mill is not just a machine—it’s a critical window into your material’s behavior.