Filter Pressure Value (FPV) Testing and its Role in Masterbatch Manufacturing
Masterbatches can be described as essential components in the vibrant world of plastics manufacturing, that serve as concentrated formulations (pigment and/or additive concentrates) and perform the crucial function of imparting color, enhancing properties, and introducing functionalities to a wide array of plastic products. These formulations, comprising pigments, additives, or other modifiers, play a pivotal role in the transformation of raw polymers into a diverse range of end-use plastics. The meticulous control of masterbatch quality is paramount in ensuring the consistent and desired characteristics of the final plastic products. One crucial aspect of quality control in masterbatch production involves Filter Pressure Value (FPV) testing—an important process that scrutinizes the stability, integrity, and efficiency of the manufacturing process. In this context, understanding the role of filter pressure testing is fundamental to guaranteeing the reliability and performance of masterbatches throughout the intricate journey from production to the end product.
EN 13900-5 standard specifies the required equipment, including the extruder, melt pump, sieves, and breaker plate along with delineating the composition of the mixture, the testing protocol, and the evaluation criteria. FPV is introduced to gauge the quality and dispersion of pigments. Through standardized quality control measures, improvements in product quality become achievable. Furthermore, comparing FPV results facilitates the ranking of similar products from different vendors. Employing the FPV test for raw material assessments ensures product quality, while also enhancing the predictability of screen changer uptime. In terms of application and operation, it is suited for testing colorants presented as color concentrates in all polymers utilized for extrusion in melt-spinning processes. The testing mixture undergoes processing in a single screw extruder featuring a non-grooved barrel and a compression screw without additional mixing elements. The polymer melt is consistently delivered with a pressure range of 30 to 60 bar (435 to 870 psi) to the melt pump, maintaining a volume of 50 to 60 cm³/min (setting 660 on the Melt pump). As the polymer passes through the filter package, particles and agglomerates above a specific size are retained, causing a pressure increase that correlates with the colorant's quality. The pressure difference between the initial and peak pressures is then employed in calculating the FPV, providing a comprehensive measure of filter performance.
Schematics of a Filter Test setup
(Picture Credits: https://slideplayer.com/slide/10801649/)
Typical FPV Test Analysis Sheet
(Picture Credits: https://www.collin-solutions.com/en/blog/2020/11/13/determination-pressure-filter-value-of-masterbatches-and-compounds/)
The polymer melt is ensured to flow through the finer screen first in order to prepare for the test. An aluminium rim of the screen pack serves as a seal to prevent undermining. Next, the breaker plate and screen pack are heated and the machine is purged with basic test polymer to expedite temperature equalization while maintaining a stable melt temperature within ±2°C. The basic test polymer is plasticized in the extruder, pumping it through the screen pack until melt temperature and pressure stabilize. The melt pump feeding pressure should be 30 to 60 bar (435 to 870 psi), with a volume flow of 50 to 60 cm³/min. The equipment must be maintained at a constant melt temperature with deviations less than ±2°C. The pressure (Ps) developed by the basic test polymer just in front of the screen pack is measured for a constant value. When the hopper is empty, and the feed-screw is visible, the test mixture is introduced. A pressure drop due to differing rheological properties can be expected. With the hopper being empty and the feed-screw visible, refilling is done with the basic test polymer. The test is concluded after 100 g of basic test polymer pass through the screen pack and pressure stabilizes.
Filter pressure testing plays a crucial role in the quality control (QC) of masterbatches, offering a comprehensive assessment of various aspects during the manufacturing process. This testing method serves as a key tool in ensuring the optimal performance and consistency of masterbatches, providing valuable insights into potential issues and allowing for proactive measures to maintain product quality. Here's a closer look at the multifaceted role of filter pressure testing in facilitating the Quality Control (QC) process of masterbatches.
- Filter Blockage Assessment: Masterbatches are typically added to the base polymer during the manufacturing process. Over time, the masterbatch may cause the accumulation of particles or agglomerates that can lead to filter blockages in processing equipment. Filter pressure testing helps assess the risk of blockages by measuring the pressure drop across the filter.
- Process Stability: Filter pressure testing provides insights into the stability of the manufacturing process. Sudden increases in filter pressure may indicate variations in the quality of the masterbatch or inconsistencies in the manufacturing process.
- Contaminant Detection: Any foreign particles, contaminants, or undispersed elements in the masterbatch can result in increased filter pressure. By monitoring filter pressure during production, manufacturers can detect the presence of contaminants that may adversely affect the final product.
- Prevention of Processing Issues: High filter pressure can lead to disruptions in the production process, such as unplanned shutdowns and increased maintenance requirements. By regularly testing and monitoring filter pressure, manufacturers can proactively address issues, preventing costly production interruptions.
- Quality Assurance: Filter pressure testing is a quality assurance measure that helps ensure that the masterbatch meets the specified standards and maintains consistent quality. Consistency in filter pressure values indicates a stable and controlled production process.
- Optimization of Formulation: By understanding how the masterbatch affects filter pressure, manufacturers can optimize the formulation to reduce the risk of filter blockages and enhance the overall efficiency of the processing equipment.
- Troubleshooting: In the event of unexpected variations in the production process or product quality, filter pressure testing can be a valuable tool for troubleshooting. Identifying the source of increased pressure can help in implementing corrective actions.
Filter Pressure Value (FPV) testing is a critical tool for ensuring the precision and reliability of concentrated formulations in the plastic industry. Guided by the EN 13900-5 standard, this testing procedure not only enhances the comparability of masterbatch tests but also facilitates standardized quality control, leading to improved product quality. From detecting contaminants and preventing processing issues to optimizing formulations and troubleshooting, FPV testing plays a multifaceted role in maintaining the desired characteristics of masterbatches. Its application, particularly in colorant testing across various polymers, ensures a standardized evaluation of filter performance, contributing to the efficiency and overall quality of end-use plastic products.
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Author
Dr. Prashant Gupta
Faculty, Polymerupdate Academy
