Epoxy resins.

Epoxy resins

Epoxy resins are also known as polyepoxides.
They belong to the category of reactive prepolymers and polymers that contain the epoxide group. The epoxide group is also called oxirane group, is shown below.

Epoxide group.
Most common epoxy resins are produced from a reaction between epichlorohydrin (ECH) and bisphenol-A (BPA), though the latter may be replaced by other raw materials.
Diglycidyl ether of bisphenol-A (DGEBA) and novolac epoxy resins are most commonly used epoxies.
Diglycidyl ether of bisphenol-A (DGEBA) is a typical commercial epoxy resins and are synthesized by reacting bisphenol-A with epichlorohydrin in presence of a basic catalyst.

Diglycidyl ether of bisphenol-A.
There are two main categories of epoxy resins, namely the glycidyl epoxy resins and non glycidyl epoxy resins.
The glycidyl epoxies are further classified as glycidyl ether, glycidyl ester and glycidyl amine.
The non glycidyl epoxies are either aliphatic or cycloaliphatic epoxy resins.
Epoxy resins are available in the form of liquid as well as high viscosity solid.
The epoxy resins are thermosetting polymers and have excellent electrical properties, low shrinkage and resistance to moisture, thermal and mechanical shocks.
The epoxy resins are used as adhesives and as coatings. NEXT

Uses of epoxy resins.

Comments

Determination of molecular weight of polymers by viscosity method.

Determination of molecular weight of polymers by viscosity method. It is a simple method for determining the molecular weight of polymers. Addition of polymers in the solvent increases the viscosity of the solvent, due to introduction of inhomogeneities by the polymers. If η₀ is the viscosity of the solvent and η is the viscosity of the solution at the same temperature, then the relative viscosity is given by Relative viscosity. Specific viscosity: It is defined as the relative increase in viscosity and is given as Specific viscosity. Reduced viscosity: It is defined as the relative increase in viscosity per unit concentration (C) of polymer and is given as Reduced viscosity. Intrinsic viscosity: The reduced viscosity is dependent on concentration (C). If a graph is plotted between reduced viscosity vs concentration then the extraplotation value when C=0 is called intrinsic viscosity. Intrinsic viscosity. Graph of reduced viscosity vs concentr

Determination of molecular weight by Light scattering method.

Determination of molecular weight by Light scattering method. Due to big size macromolecules in solution, turbidity is produced. The light rays get scattered, when pass through macromolecule solution due to turbidity. The turbidity T is given by Where I₀ is the intensity of incident light. Iₜ is the intensity of transmitted light after passing through a solution of length l. In case of proteins or higher polymers the turbidity is small and is determine from the intensity of light scattered at 90° to the beam. This can be done by using a simple photometer as shown in figure below. Turbidity increase with increase in concentration as well as molecular weight. The Turbidity is related to molecular weight by the equation given by Debye. Hc/T=1/M+2Bc Where B is second virial coefficient and H is a constant. If we plot a graph between Hc/T vs c we get a straight line with intercept 1/M. Thus This curve was plotted by Zimm, so is called Zimm's Curve. Thus the c

Polypropylene (PP)

Polypropylene (PP). Polypropylene (PP) is also known as polypropene. Polypropylene is made from the polymerisation of propylene gas in the presence of Zeiglar Natta catalyst or metallocene catalyst. Polypropylene. Thus propene (or propylene) is the monomer of polypropylene. Polypropylene is a highly flammable material. It is sensitive to microbial attacks, such as bacteria and mold. It exhibits excellent resistance to diluted and concentrated acids, alcohols and bases. Polypropylene is used to make lunch boxes, margarine containers, yogurt pots, syrup bottles etc. Disposable syringes is the most common medical application of polypropylene. Polypropylene rope and twine are very strong and moisture resistant very suitable for marine applications. Polypropylene, highly colorfast, is widely used in manufacturing carpets, rugs and mats. Uses of Polypropylene. Questions on polypropylene; Q1) What is polypropylene? Ans) Polypropylene is a polymer of propylen

Polymers

Search This Blog