Glossary

Air classification is a particle separation process that uses controlled airflow to separate powder or granule particles based on their size, shape, and density. Lighter, finer particles are carried upward or outward by the airstream and collected separately, while heavier, coarser particles fall out of the airstream into a different collection stream. Air classification produces a tighter, more controlled particle size distribution than mechanical screening alone and can achieve separation at finer cut points that are impractical with physical screens. The air classifier mill integrates impact milling and air classification in a single machine, recirculating oversized particles back into the milling zone until they reach the target size. Air classification is commonly used for polymer additives, specialty chemicals, and fine mineral powders where a sharp upper particle size cutoff is required. Toll Compaction operates an air classifier mill at its facilities as part of its size reduction service offering.

Blending is the process of uniformly mixing two or more powder components to achieve consistent composition, distribution, and performance across a production batch. In industrial chemical and polymer additive manufacturing, effective blending ensures that each unit of the finished product contains the correct proportion of every ingredient, which directly affects product quality, reactivity, and downstream processing behavior. Common blending equipment includes ribbon blenders, paddle blenders, and tumble blenders, each suited to different material types and batch sizes. Poor blending results in segregation, inconsistent dosing, and batch failures that are costly to diagnose and correct. Toll blending allows manufacturers to outsource this step to a certified processor without investing in dedicated equipment or facility space.

Bulk density is the mass of a powder per unit volume, including the air spaces between individual particles. It is one of the most practically important physical properties in powder processing because it directly affects how much material fits in a given container, how powders behave in automated feeding and dosing equipment, and what freight and packaging costs look like on a per-unit basis. Two forms are commonly measured: loose bulk density, which is the density of a powder poured freely into a container, and tapped bulk density, which is measured after the container has been mechanically tapped to settle the powder. A low bulk density means higher freight costs, larger packaging requirements, and potential flow problems in production equipment. Dry granulation and roller compaction are commonly used to increase bulk density by converting fine, airy powders into denser granules without changing the material's chemistry.

Caking is the unwanted agglomeration of powder particles into hardened lumps or masses due to exposure to moisture, heat, pressure, or extended storage time. It is one of the most common and costly problems in industrial powder manufacturing, causing production delays, dosing inconsistencies, and potential batch rejections. Caking occurs when surface moisture or hygroscopic material properties allow particles to form solid bridges at their contact points, which then harden as conditions change. Materials prone to caking include water-soluble salts, hygroscopic chemicals, and fine powders with high surface area. Preventing caking requires careful control of moisture during processing, appropriate packaging to exclude humidity, and in some cases granulation to reduce surface area and improve the physical stability of the powder during storage and transport.

Classification is the separation of a powder or granule mixture into fractions based on particle size. In powder processing, classification is used to remove oversized particles (overs) and undersized particles (fines) from a batch, ensuring that the finished product falls within a defined particle size range. The two primary classification methods are mechanical screening, which uses vibrating mesh screens to separate particles by size, and air classification, which uses controlled airflow to separate particles based on their aerodynamic properties. Classification is a critical quality control step after milling or granulation and is also used as a standalone service to bring off-spec material into specification. For industrial chemicals, polymer additives, and specialty powders, tight classification improves downstream processing performance, product consistency, and customer satisfaction.

Compaction is the process of mechanically compressing a powder into a denser, more solid form under controlled pressure. In industrial powder processing, compaction is used to increase bulk density, improve flowability, reduce dust, and prepare materials for downstream applications such as tableting, briquetting, or pelletizing. Roller compaction is the most common form of compaction used in toll processing, in which powder is fed between two counter-rotating rollers that compress it into a dense ribbon or sheet. This ribbon is then milled and screened to produce uniform granules. Because roller compaction is a dry process that requires no liquids, binders, or drying steps, it is particularly well-suited for moisture-sensitive and heat-sensitive materials including many polymer additives and specialty industrial chemicals. Compaction is distinct from granulation in that it refers specifically to the mechanical densification step rather than the overall particle enlargement process.

De-agglomeration is the process of breaking apart clusters of bonded or fused powder particles back into their individual, free-flowing form. Agglomerates form during storage, transport, or processing when particles bond together due to moisture, static charge, mechanical compression, or surface adhesion forces. Left unaddressed, agglomerates cause inconsistent dosing, poor blend uniformity, and equipment bridging and blockages throughout the production line. De-agglomeration is typically achieved using milling equipment such as a Fitzmill, lump breaker, or hammer mill operated at low intensity, with the goal of breaking the bonds between particles rather than reducing individual particle size. It is commonly performed as a pre-processing step before blending, granulation, or classification to ensure that incoming material is in a suitable state for further processing. Toll Compaction performs de-agglomeration as part of its size reduction and powder processing services.

Dry granulation is a particle size enlargement process that converts fine powders into larger, more uniform granules using only mechanical force, without introducing any liquid, solvent, binder, or heat. The most common dry granulation method is roller compaction, in which powder is compacted between two rollers into a dense ribbon that is subsequently milled and screened to the target granule size. Dry granulation is the preferred choice for moisture-sensitive materials, heat-sensitive compounds, and materials that are incompatible with the liquid binders used in wet granulation. The resulting granules exhibit significantly improved flowability, higher bulk density, reduced dust generation, and better blend uniformity compared to the original fine powder. Because no drying step is required, dry granulation is faster, more energy-efficient, and gentler on chemically sensitive materials than wet granulation processes. Dry granulation is one of the core processing capabilities at Toll Compaction's NJ and WV facilities.

A Fitzmill is a rotating knife and screen impact mill manufactured by the Fitzpatrick Company, widely used in industrial chemical, pharmaceutical, and food ingredient processing for particle size reduction. Material is fed into the milling chamber where rotating blades strike and reduce particles through a combination of impact, cutting, and attrition. A screen at the outlet controls the maximum particle size passing through, allowing the target size range to be set by selecting the appropriate screen. The Fitzmill is highly versatile and can be configured with different blade types and screen sizes to process a wide range of materials and target particle sizes, typically in the range of 150 to 2000 microns. It operates at relatively low temperatures compared to hammer mills, making it suitable for moderately heat-sensitive materials including polymer additives, pharmaceutical excipients, and food-grade powders. Toll Compaction operates Fitzmills at its NJ and WV facilities as part of its size reduction services.

Granulation is the process of forming fine powder particles into larger, more uniform granules to improve flowability, reduce dust, increase bulk density, and enhance downstream processing performance. There are two primary approaches: wet granulation, which uses liquid binders to agglomerate particles and requires a subsequent drying step, and dry granulation, which uses mechanical compaction pressure alone without introducing any liquid. Dry granulation via roller compaction is the preferred method for heat-sensitive and moisture-sensitive materials including many polymer additives, specialty industrial chemicals, and pharmaceutical excipients, because it preserves material chemistry while achieving the same physical improvements as wet granulation. Granulated materials flow more reliably through production equipment, pack more consistently into containers, generate less airborne dust, and disperse more uniformly in downstream compounding or formulation processes. Granulation is one of the core services offered at Toll Compaction's NJ and WV facilities.

A hygroscopic material is one that actively attracts and absorbs water vapor from the surrounding air, even at relatively low ambient humidity levels. Hygroscopic powders present particular challenges in processing and storage because moisture absorption can cause caking, agglomeration, changes in bulk density, degradation of active components, and significant shifts in particle size distribution over time. The distinction between hygroscopic and simply moisture-sensitive is important: hygroscopic materials actively draw in moisture from the environment, while moisture-sensitive materials are affected by moisture but do not necessarily attract it. Many polymer additives, pharmaceutical excipients, and specialty industrial chemicals are hygroscopic, and processing them requires controlled-humidity handling environments, moisture-barrier packaging, and in most cases dry processing methods such as dry granulation rather than wet granulation to avoid introducing additional moisture into the material during processing.

Moisture sensitivity describes the tendency of a powder or granule to absorb water vapor from the surrounding environment, which can alter its flowability, stability, bulk density, chemical reactivity, and shelf life. Hygroscopic powders, those that readily attract and hold moisture, are a particularly challenging subset. Even small amounts of absorbed water can cause caking, agglomeration, degradation of active components, and significant changes in particle size distribution. Moisture-sensitive materials require careful handling throughout the processing chain, including controlled humidity environments during processing, moisture-barrier packaging, and in some cases the use of dry granulation rather than wet granulation to avoid introducing liquid into the process. Many polymer additives, pharmaceutical excipients, and specialty industrial chemicals are moisture-sensitive, and processing them correctly requires an experienced toll processor with the right equipment and facility controls.

Particle size distribution (PSD) is the range and proportion of particle sizes present within a powder or granule sample, typically expressed as the percentage of particles falling within defined size ranges. PSD is one of the most critical quality attributes in industrial powder processing because it governs how a material flows, compacts, blends, dissolves, reacts, and performs in downstream applications. A narrow PSD means particles are relatively uniform in size, which typically improves flowability, blend homogeneity, and dosing accuracy. A broad PSD means a wider mix of sizes, which can lead to segregation during blending and transport. PSD is measured using techniques such as laser diffraction, sieve analysis, or dynamic image analysis, and results are reported as parameters including D10, D50, and D90 values representing the 10th, 50th, and 90th percentile particle sizes. Controlling PSD through precision granulation, milling, and classification is a core capability at Toll Compaction.

Particle size reduction is the mechanical process of breaking solid particles from a larger size into a smaller, more controlled size range. Also referred to as milling, comminution, or grinding depending on the context and industry, it is one of the most fundamental operations in industrial powder processing. Particle size reduction is used to achieve a target particle size distribution that improves flowability, increases reactivity, enhances blend uniformity, accelerates dissolution, or meets downstream processing specifications required by customers. The primary methods used for industrial chemical and specialty powder applications include impact milling via Fitzmill or hammer mill, and precision classification milling via air classifier mill. The choice of method depends on the target particle size, material hardness, heat sensitivity, and required throughput. Toll Compaction provides particle size reduction services for industrial chemicals, polymer additives, minerals, and food-grade materials at its NJ and WV facilities.

Pelletizing is the process of compressing fine powder into dense, uniform pellets of controlled size and shape through mechanical compaction or extrusion. Unlike granulation, which produces irregularly shaped agglomerates, pelletizing produces highly consistent cylindrical or spherical pellets with a tighter size distribution and typically higher density. Pelletizing improves flowability, significantly reduces airborne dust, increases bulk density to lower freight and packaging costs, and produces a more user-friendly, market-ready product form for industrial customers. It is particularly valuable for materials destined for agricultural, water treatment, oilfield, or industrial chemical applications where a free-flowing, dustless pellet is a standard customer expectation. Pelletizing is also used to convert multi-component blends into a stable, non-segregating pellet form that maintains blend uniformity during transport and handling. Toll Compaction provides pelletizing services at its NJ and WV facilities for industrial chemicals, polymer additives, minerals, and food-grade materials.

Powder flowability is a measure of how easily a powder or granule moves through processing equipment, filling systems, and packaging machinery under its own weight or with applied force. It is one of the most practically important properties in powder manufacturing because poor flowability causes bridging and arching in hoppers, inconsistent feed rates, inaccurate dosing, production downtime, and high material waste. Flowability is influenced by particle size and shape, surface area, bulk density, moisture content, and electrostatic charge. Fine powders with high surface area typically flow poorly due to high cohesive forces between particles. Improving flowability is one of the primary reasons manufacturers choose to granulate or pelletize their powders: larger, denser, more spherical particles flow far more reliably than fine, irregular ones. Flowability is commonly measured using angle of repose, Carr Index, Hausner Ratio, and flow-through-orifice tests.

Roller compaction is a dry granulation process in which fine powder is fed between two counter-rotating rollers under controlled pressure, compressing it into a dense ribbon or flake. That ribbon is then milled and screened to produce uniform granules at a target particle size distribution. Unlike wet granulation, roller compaction uses no liquids, solvents, binders, or drying steps, making it the preferred method for heat-sensitive and moisture-sensitive materials including polymer additives, specialty industrial chemicals, and pharmaceutical excipients. The process simultaneously improves flowability, increases bulk density, and reduces airborne dust, addressing the most common challenges associated with fine powder handling in a single operation. Compaction pressure, roller gap, and roller speed can all be adjusted to dial in the target granule density and size for each specific material. Toll Compaction uses Fitzpatrick roller compactors with stainless steel contact parts at its Washington, West Virginia facility for polymer additive and industrial chemical processing.

Screening is the mechanical separation of powder or granule particles by size using vibrating mesh screens or sieves. Material is passed over or through a screen with a defined mesh opening, and particles either pass through (unders) or are retained on the screen (overs), allowing the product to be classified into distinct size fractions. Screening is used after milling or granulation to ensure the finished product falls within the target particle size specification, to remove fines or oversize material that would cause problems in downstream processing, and as a quality control step to verify that material meets customer or internal specifications. Industrial screening can achieve separations from very coarse fractions of several millimeters down to fine separations below 100 microns, depending on the screen type and equipment configuration. Toll Compaction provides industrial screening and classification services at its NJ and WV facilities for chemicals, polymer additives, minerals, and food-grade materials.

Toll blending is a contract service arrangement in which a manufacturer outsources the blending of two or more powder or granule components to a specialized processor, without transferring ownership of the materials or the formulation. The customer supplies the raw materials and blend specifications. The toll blender provides the equipment, facility, labor, and quality management to perform the blending operation and return or ship the finished blend as directed. Toll blending is used by industrial chemical producers, polymer additive manufacturers, and food ingredient suppliers who need blending capacity without the capital investment of purchasing and operating dedicated equipment. It differs from contract manufacturing in that the customer retains full ownership and responsibility for the materials throughout the process. Toll Compaction provides toll blending services using stainless steel ribbon blenders at its ISO 9001:2015 certified NJ and WV facilities.

Toll processing is a service model in which a manufacturer outsources one or more powder processing operations to a specialized contract processor without transferring ownership of the material. Operations covered under toll processing include blending, granulation, size reduction, classification, pelletizing, compaction, and repackaging, among others. The customer supplies the raw material and specifications. The toll processor provides the equipment, facility, labor, quality management, and expertise to perform the processing and return or ship the finished material as directed. Toll processing is distinct from contract manufacturing in that the customer retains full ownership of and responsibility for the material throughout. It is used by industrial chemical producers, polymer additive manufacturers, mineral processors, and food ingredient suppliers who need access to specialized processing equipment without the capital investment of owning and operating it in-house. Toll Compaction has provided toll processing services from its NJ and WV facilities since 1978, serving industrial chemical, polymer additive, mineral, and food-grade applications.