Polydimethyl Siloxane Fluids example essay topic

Polydimethyl siloxane is one of the most common silicones in the world. Polydimethyl siloxane is the simplest of the silicones. Polydimethyl siloxane is also known as, poly (dimethyl siloxane), dimethyl silicone and dimethyl silane diol. Its applications range from medical devices to elastomers, caulking, lubricating oil and heat resistant tiles.

Polydimethyl siloxanes chemical formula is (C 2 H 6 OSi) n and its structural formula is: chain: Polydimethyl siloxane is an inorganic polymer; there are no carbons in the backbone of the chain. The backbone is made up of alternating oxygen and silicon atoms. The silicon atoms' each have two methyl (CH 3) groups attached to it. Polydimethyl siloxane belongs to the elastomer group. Elastomers are special because of the fact that they bounce. Elastomers can be stretched to many times their original length, and can bounce back into their original shape without permanent deformation.

Polydimethyl siloxane is formed by condensation polymerization... Two general methods of polymerization are employed. Gums and non-silanol terminated fluids are produced by base-catalyzed polymerization. Under typical conditions potassium, sodium or tetramethylammonium silanolate catalysts are introduced into a mixture of monomers and endcappers.

Heating under moderate conditions equilibrates the mixtures. Polydimethyl siloxanes may be prepared from hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane or decamethylcyclopentasiloxane monomers with an end capper like hexamethyldisiloxane or the less volatile decamethyltetrasiloxane. This method is used primarily for low molecular weight silanol terminated, or hydride functional siloxanes. The physical and chemical properties of polydimethyl siloxane are, in its physical state, its appearance is clear, colourless oily liquid, the boiling point is 400 C, the melting point is -34 C, density is 0.97, flash point 200 C, Tg is -123 C, viscosity is 60,000 cp at 25 C, the refractive index is 1.403, solubility parameter is 7.2 and it is insoluble in water. Polydimethyl siloxane (silicone fluids) have unique properties because they are not products of organic chemistry.

They were the first, and are still only, major class of polymers that are products of inorganic chemistry. Silicone fluids consist of a broad range of different materials with the following characteristics, wide temperature range, thermal stability, low flammability, high compressibility, low surface tension and low toxicity. Conventional silicone fluids are composed of polymer chains with unique flexibility. Polydimethyl siloxane has virtually no energy barrier for rotation. This results in one of the lowest glass-transition temperatures of any polymer. The liquid surface tension of polydimethyl siloxane is lower than the critical surface tension of wetting (24 dynes / cm ).

This causes polymers to spread over their own adsorbed films. An important consequence of the low intermolecular forces in poly siloxanes is the highest permeability coefficients of any polymer for oxygen and nitrogen. Polydimethyl siloxane is normally stable. Hazardous Polymerization will not occur.

Oxidizing compounds can cause a reaction avoid contact with alkali, acids and oxidizing agents. Polydimethyl siloxane decomposes on heating producing formaldehyde in small amounts. The substance can be absorbed into the body by inhalation, but there is no indication about the rate at which a harmful concentration in the air is reached on evaporation of this substance. Avoid contact with eyes, skin and avoid inhalation and ingestion of product. If contact occurs with eyes flush with clean soap and water for 15 minutes and consult a physician. Contact with skin, scrub with soap and water.

Protective gloves and safety goggles should been warn as a precaution. In case of a spillage, collect leaking and spilled liquid in seal able container as far as possible. Absorb remaining liquid in sand or inert absorbent and remove to safe location. Polydimethyl siloxane fluids are used in a wide variety of consumer and industrial applications such as personal care products, foods medicine, release agents, antifoams and dielectric fluids. A large fraction of the total material produced is used in applications that do not result in down-the-drain disposal. Only about 14% of the total used is released to the environment in down the drain disposal.

It is expected that most of this 14% will enter the environment adsorbed to sewage sludge where it is expected to undergo soil-catalyzed hydrolysis. The initial fate of applications such as personal care products and detergent antifoams is wastewater. Some applications such as polishes and household products are dispersed in the environment following their use and are not likely contained by wastewater treatment. Although polydimethyl siloxane will either be absorbed to sludge or discharged with liquid effluent to a body of water, wastewater treatment plant effluent levels are generally below detection limits. Laboratory and field studies have demonstrated the potential for polydimethyl siloxane to degrade in soils and sediments. No adverse effects were observed in terrestrial or aquatic organisms exposed to Polydimethyl siloxane at concentrations that were many times higher than those observed in the field.

The toxicity of Polydimethyl siloxane to environmental organisms is low. The comparison of polydimethyl siloxane environmental levels to measured no effect levels aquatic organisms showed that polydimethyl siloxane is not predicted to pose a risk to the environment. Polydimethyl siloxanes have a wide range of uses. Polydimethyl siloxanes are typically used as additives in personal care, household and automotive products to impart water repellency, shine and feel. In detergents, food processing and healthcare applications they are mainly used as antifoams additives.

Other typical applications include lubricants, caulking, mold releases, paper coatings or textile finishing's to impart water repellence, feel or release. Polydimethyl siloxanes are also used as electrical or mechanical fluids. Because polydimethyl siloxane has many unique features and properties, they are able to adapt to uses in silicones as dielectric, hydraulic, heat transfer, power transmission and damping fluids. They have found applications when incorporated as additives into plastics and rubbers as process and release aids, into coatings for flow and level control and into process streams as antifoams. Other unique properties have led to their introduction in acoustical applications such as ultrasonic sensor and sonar buoys. Light refractive and index matching properties have allowed the use of silicones in fiber optics and opt electronics.

The large number of applications has made many improvements and refinements of silicone fluids. Polymers have impacted our lives greatly. They have made our daily lives easier and more convenient. We use polymers such as plastics, rubbers and silicones almost everyday. Polydimethyl siloxane we use as lubricant, caulking and it's used with additives in our personal care product. With continuing research many more applications for polydimethyl siloxane will be discovered.