The MLW‑400C computer‑controlled twin‑barrel capillary rheometer adopts a twin‑barrel and twin‑ram structure, supports Bagley die‑end correction, and is capable of measuring shear viscosity and extensional viscosity simultaneously. It can perform various rheological tests including constant‑speed, constant‑pressure, step‑shear and flow‑no‑flow tests, and output complete rheological curves such as shear stress‑shear rate and viscosity‑shear rate curves. Compared with single‑barrel models, it delivers higher‑precision viscosity test data and supports parallel comparison tests. It is suitable for plastic, modified composite and elastomer factories for raw material inspection, formula research & development, process simulation, failure analysis and product quality control.

I. Incoming Raw Material Inspection and Batch Consistency Control

Rheological tests are carried out on incoming resin, filled modified materials and elastomer raw materials to obtain apparent viscosity and shear viscosity, so as to evaluate the melt flow behavior of raw materials from different batches of the same grade. Fluctuations in polymerization degree and additives of raw materials of the same grade will lead to differences in fluidity under high‑shear conditions. While the melt flow index tester only works at a single shear point, this instrument covers a wide shear‑rate range, which is closer to the actual shear conditions of injection molding and extrusion processes. It can identify hidden quality fluctuations of incoming materials and reject unqualified raw materials to avoid mass waste caused by defective materials on production lines.

Advantages of the twin‑barrel design: Parallel tests can be conducted on the same sample in two groups to quickly verify test repeatability. Meanwhile, new‑batch and old‑batch raw materials can be tested synchronously for intuitive batch‑difference comparison, assisting grade verification and identification of wrong‑feeding or material mixing faults. It is also applicable to recycled regrind materials: viscosity changes caused by molecular degradation of recycled materials can be detected to guide the addition ratio of regrind materials.

II. Formula Research and New‑Material Development

When developing formulas for modified plastics, filled blends and elastomers, the instrument tests viscosity variations of materials with different filler and additive ratios over a wide shear‑rate range, evaluates the influences of fillers, plasticizers and lubricants on melt shear viscosity and extensional viscosity, and helps select optimal formulas rapidly, reducing trial‑production runs on manufacturing lines and saving material and time costs.

Step‑shear and flow‑no‑flow tests can determine the minimum flow temperature of materials, observe melt fracture and unstable flow phenomena, predict the upper processing limit of new materials, and assess whether the formula is compatible with in‑house extrusion and injection‑molding processes. Both shear viscosity and extensional viscosity can be obtained in one test. For processes with remarkable extensional effects such as film blowing, foaming and fiber spinning, the instrument can evaluate the extensional processing performance of materials, a function unavailable for ordinary melt flow index testers.

III. Simulation of Actual Processing Conditions and Optimization of Production Process Parameters

The rheometer can simulate various shear‑rate, temperature and pressure conditions on‑site during injection molding, extrusion and film‑blowing production. Factories can set processing temperature, screw speed, back‑pressure and other process parameters according to rheological curves, shortening production‑line commissioning cycles and reducing trial‑run waste.

It studies the coupling effects of temperature and shear on material viscosity, determines the safe processing window of materials, and avoids processing defects such as shear‑induced thermal degradation, melt fracture and unstable discharge. Real‑time Bagley die‑end correction eliminates test errors from die pressure loss and obtains authentic viscosity data of materials, providing a reliable basis for process design.

IV. Reverse Analysis of Production Defects and Troubleshooting

When production‑line defects occur, including silver streaks, melt fracture, unstable discharge, unstable bubble in film‑blown products, uneven thickness and fiber breakage, qualified samples and defective samples can be tested for rheological comparison. Viscosity‑shear‑rate curves help distinguish root causes: raw‑material batch fluctuation, thermal‑shear degradation of materials or unreasonable process parameters.

The twin‑barrel structure allows synchronous testing of qualified samples and problematic samples under identical conditions, eliminating interference from variable test conditions, accelerating fault analysis and shortening production‑line downtime.

V. Quality Archive, Customer Audit and Data Accumulation

Establish an in‑house rheological database for materials, and archive complete parameters of various materials, including shear viscosity, extensional viscosity, critical shear rate for melt fracture and minimum flow temperature. Historical data can be retrieved directly for rapid production changeover when switching material grades or adjusting formulas.

The software outputs complete rheological curves and test reports for internal quality archiving, downstream‑customer technical audits and third‑party inspection. Multi‑curve superposition comparison is supported to facilitate technical analysis.

VI. Summary of Cost‑Reduction and Efficiency‑Improvement Benefits

1. Higher test accuracy: With Bagley correction and twin‑barrel parallel comparison, the instrument reduces systematic errors compared with single‑barrel capillary rheometers, and its test data better reflects the authentic rheological behavior of materials under processing conditions.
2. Savings on R&D and trial‑production costs: Formula evaluation under wide‑range shear conditions is completed in the laboratory, avoiding repeated large‑scale production trials and lowering raw‑material consumption.
3. Mass‑production risk prevention: Hidden raw‑material hazards and formula‑related processing defects are identified in advance to prevent mass‑produced defective products.
4. High multi‑task testing efficiency: Two samples can be tested synchronously in twin barrels to shorten testing cycles. Shear viscosity and extensional viscosity are acquired at the same time to evaluate injection‑molding, extrusion, film‑blowing and foaming processes.
5. Independent process control: Full‑range rheological data can be obtained in‑house instead of relying entirely on information provided by raw‑material suppliers.

Applicable factories: Modified plastic manufacturers, composite material plants, elastomer / rubber processors, film‑blowing / foaming / fiber‑spinning material enterprises, engineering‑plastic producers and recycled‑plastic pelletizing factories.

Supplementary comparison: Melt flow index testers perform tests under a single‑shear condition; capillary rheometers cover a wide shear‑rate range; torque rheometers focus on internal mixing and screw‑extrusion simulation. The three types of instruments complement each other.

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