Factors affecting size-reduction: lots of factors are affecting size reduction Hardness, Toughness, Abrasiveness, Stickiness, Slipperiness, Softening Temperature, Material Structure, Moisture Content, Physiological Effect, Purity Required, Ratio of Feed Size to Product Ratio, and Bulk Density
Table of Contents
Factors affecting size-reduction
Hardness
Hardness is a face property of the material and is constantly confused with strength. It’s possible that material is veritably hard posing a size reduction delicate. If the material is brittle also size reduction may present no special problems. An arbitrary scale of hardness has been cooked known as Moh’s Scale. A series of mineral substances have been given hardness figures between 1 and 10, ranging from graphite to diamond. Up to 3 are known as soft and can be marked with the fingernail. Hardness above 7 is designated as hard and can not be marked with a good pen cutter blade, while those between 3 and 7 are described as intermediate. In general, the harder the material the more delicate it’s to reduce in size.
Toughness
In most cases, a material’s toughness is far more important than its hardness. Soft but robust material may have greater difficulty shrinking than a hard substance. Tough materials, such as rubber, are more difficult to break than fragile substances, such as blackboard chalk. Toughness is a characteristic of fibrous medicines that are frequently linked to moisture content. The hardness of some materials can be lowered by treating them with liquid nitrogen at temperatures below 100 to 150 °C. The method has additional advantages in that there is a reduction in the decomposition of thermolabile materials, in the loss of volatile materials, in the oxidation of constituents, and in the risk of explosion.
Abrasiveness
Abrasiveness is a property of hard materials (minerals) that limits the mill to be used for size reduction. During the grinding of some very abrasive substances, the final powder may be contaminated with more than 0.1 % of metal worn from the grinding mill.
Stickiness
The sticky nature of the material makes size reduction extremely difficult. This type of material might clog the sieve meshes or stick to the grinding surfaces. Typically, size reduction technology generates heat. Gummy or resinous substances can be difficult to shrink because their hardness varies as heat is generated and they become sticky. In some cases, adding inert material like kaolin to sulfur can help to lessen the stickiness.
Slipperiness
Slipperiness is the reverse of stickiness. This property also gives rise to size reduction difficulties, since the material acts as a lubricant and lowers the efficiency of the grinding surfaces. While size reduction material slips create problems in milling.
Softening Temperature
Heat is generated during the size reduction process, which might cause some material to melt, therefore the temperature at which this occurs is critical. Waxy substances, such as stearic acid, or medications containing oils or fats, for example, may have difficulty shrinking in size while losing functionality. This can be avoided by cooling the mill, either with a water jacket or by blowing cold air through the machinery. Liquid nitrogen is an additional option.
Material Structure
Pharmaceutical materials come in a wide range of shapes and sizes; some are homogeneous, but the majority have unique architectures. Mineral substances, for example, have weak points. These materials split into flakes along the lines of weakness, whereas vegetable medications have a cellular structure that typically leads to lengthy fibrous particles. As a result, the size of the final product may vary depending on the working conditions. The amount of energy necessary to do this task varies.
Moisture Content
The amount of moisture in a substance affects a variety of qualities that can affect size reduction. Hardness, toughness, and stickiness are examples of these qualities. In general, materials for size reduction should be dry or wet, but not completely damp. If the substance is to be ground dry, it should have less than 5% moisture, and if it is to be ground wet, it should have more than 50% moisture.
Physiological Effect
Some compounds are extremely toxic, and even little amounts of penalties can harm the operator’s health. Mills must be enclosed to avoid fines, and exhaust systems must also be supplied. Wet grinding is used if possible to completely eradicate the condition.
Purity Required
The wear and tear of the grinding surfaces are caused by some size reduction devices. When a high level of product purity is required, these machines should be avoided. Similarly, some of those machines are so complicated that cleaning between batches of various materials is impossible.
Ratio of Feed Size to Product Ratio
Machines that produce fines may need to reduce the size in numerous stages using various equipment. Preliminary crushing, coarse grinding, and finally fine grinding, for example. In such circumstances, feed size must be carefully regulated in order to achieve efficient reduction.
Bulk Density
The capacity of most batch mills is determined by the amount of material processed. Solid materials, rather than liquids, are frequently required by these mills. The mill’s output is proportional to the substance’s bulk density. The greater the bulk density, the more valuable the product.
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