A-Z of gypsum and plaster properties
Due to their diverse properties gypsum and plaster are used in a wide variety of products, processes and applications.
- Absorbent properties : plaster’s absorption properties are key to producing quality ceramic pieces
- Acoustic properties: plaster is used in interior construction applications due to its capacity to absorb air-borne sounds.
- Adhesion properties : plaster is used in construction materials for its capacity to adhere to a variety of surface backgrounds
- Binding properties : plaster is used a binding or gelling agent for plaster bandages,
- Bulk density / bulking agent : gypsum is used as an extender or filler to give bulk to products
- Chemical inertness : gypsum is a chemically inert mineral which makes it compatible in a wide range of formulations.
- Compressive strength: where strength is important plaster can be formulated using alpha plaster and additives to optimise performance.
- Conductivity properties: plaster has low conductivity making it an energy saving, insulating material in construction applications.
- Controlled expansion: required for dimensional accuracy in moulding applications.
- Expansion : plaster expands during setting, and expansion may be controlled to meet application requirements
- Exothermic properties : plaster produces heat on setting
- Fire resistance properties: Plaster is classed as an A1 material (not contributing to fire). Finished plaster products which contain less than 1% in weight or volume (whichever is higher) of organic material, are also classed as A1 in accordance with 96/603/CE.Plaster does not contribute to the progression of fire, due to the chemically combined water which is released when the product is exposed to temperatures > 40°C.Plaster also has a high water uptake during mixing and this water is also released when the product is exposed to high temperatures, which contributes to retarding the progression of fire. Plaster produces low levels of non-toxic smoke in the event of a fire.
- Flexural strength : plaster can be formulated to improve its ability to bend
- Flocculating properties: gypsum is used as a flocculating aid in agricultural and water treatment applications.
- Hardness: plaster can be formulated to optimise surface hardness
- Impact resistance : plaster can be formulated to optimise impact resistance
- Mechanical strength / resistance: where strength is important plaster can be formulated using alpha plaster and additives to optimise performance.
- Moisture resistance properties : Plaster is relatively stable under “normal” air humidity conditions, and will not be subject to mould or fungus growth
- Opacifying properties : gypsum is used in paints to increase opacity and adjust gloss level
- Particle size distribution: controlled during manufacturing to adapt to meet application requirements
- Permeability: a key property in plaster ceramic moulds, plaster can be formulated for use under varying air pressure conditions.
- pH buffer : gypsum is used in water and agricultural treatments for its neutral pH level
- Porosity: a key property in plaster ceramic moulds, plaster porosity can be adapted to individual needs.
- Purity: by carefully selecting and processing natural gypsum rock, high purity grades are achieved, which are necessary to produce high performance industrial plasters.
- Radiation shielding properties: gypsum has a capacity to absorb neutrons, and is therefore useful in the radiation protection of buildings containing medical linear accelerators, used for cancer treatment.
- Reflectance: high reflectance (colour) is achieved through carefully selecting and processing natural gypsum rock.
- Reinforcement: plaster may be used with a variety of reinforcement materials such as natural or glass fibres.
- Setting properties: plaster setting properties may be controlled through formulation to meet application requirements.
- Shrinkage: gypsum / plaster can be used to compensate for shrinkage in construction formulations.
- Solubility : gypsum may be used in water based formulations for agriculture due to its solubility in water
- Thermal reaction : in cosmetics, the thermal reaction during curing is a recognised benefit
- Whiteness : this property is particularly required in wall finishing applications and decorative interior applications where the desired finished surface will be white