Water retention is an important property for many industries that use hydrophilic substances such as cellulose ethers. Hydroxypropylmethylcellulose (HPMC) is one of the cellulose ethers with high water retention properties. HPMC is a semi-synthetic polymer derived from cellulose and is commonly used in a variety of applications in the construction, pharmaceutical and food industries.
HPMC is widely used as a thickener, stabilizer and emulsifier in various food products such as ice cream, sauces and dressings to enhance their texture, consistency and shelf life. HPMC is also used in the production of pharmaceuticals in the pharmaceutical industry as a binder, disintegrant and film coating agent. It is also used as a water-retaining agent in building materials, mainly in cement and mortar.
Water retention is an important property in construction because it helps keep freshly mixed cement and mortar from drying out. Drying can cause shrinkage and cracking, resulting in weak and unstable structures. HPMC helps maintain the water content in cement and mortar by absorbing water molecules and slowly releasing them over time, allowing building materials to properly cure and harden.
The water retention principle of HPMC is based on its hydrophilicity. Due to the presence of hydroxyl groups (-OH) in its molecular structure, HPMC has a high affinity for water. The hydroxyl groups interact with water molecules to form hydrogen bonds, resulting in the formation of a hydration shell around the polymer chains. The hydrated shell allows the polymer chains to expand, increasing the volume of HPMC.
Swelling of HPMC is a dynamic process that depends on various factors such as degree of substitution (DS), particle size, temperature and pH. The degree of substitution refers to the number of substituted hydroxyl groups per anhydroglucose unit in the cellulose chain. The higher the DS value, the higher the hydrophilicity and the better the water retention performance. The particle size of HPMC also affects water retention, as smaller particles have a greater surface area per unit mass, resulting in greater water absorption. Temperature and pH value affect the degree of swelling and water retention, and higher temperature and lower pH value enhance the swelling and water retention properties of HPMC.
The water retention mechanism of HPMC involves two processes: absorption and desorption. During absorption, HPMC absorbs water molecules from the surrounding environment, forming a hydration shell around the polymer chains. The hydration shell prevents the polymer chains from collapsing and keeps them separated, leading to swelling of the HPMC. The absorbed water molecules form hydrogen bonds with the hydroxyl groups in HPMC, enhancing the water retention performance.
During desorption, HPMC slowly releases water molecules, allowing the building material to cure properly. The slow release of water molecules ensures that the cement and mortar remain fully hydrated, resulting in a stable and durable structure. The slow release of water molecules also provides a constant water supply to cement and mortar, enhancing the curing process and increasing the strength and stability of the final product.
In summary, water retention is an important property for many industries that use hydrophilic substances such as cellulose ethers. HPMC is one of the cellulose ethers with high water retention properties and is widely used in construction, pharmaceutical and food industries. The water retention properties of HPMC are based on its hydrophilicity, which enables it to absorb water molecules from the surrounding environment, forming a hydration shell around the polymer chains. The hydrated shell causes the HPMC to swell, and the slow release of water molecules ensures that the building material remains fully hydrated, resulting in a stable and durable structure.
Post time: Aug-24-2023