Acrylic Family

Chemical structure

History• The first acrylic acid was created in 1843. Methacrylic acid,

derived from acrylic acid, was formulated in 1865. The reaction between methacrylic acid and methanol results in the ester methyl methacrylate.

• The German chemists Fittig and Paul discovered in 1877 the polymerization process that turns methyl methacrylate into polymethyl methacrylate.

• In 1933 the German chemist Otto Röhm patented and registered the brand name PLEXIGLAS. In 1936 the first commercially viable production of acrylic safety glass began.

• During World War II acrylic glass was used for submarine periscopes, and windshields, canopies, and gun turrets for airplanes.

Preparation• PMMA is routinely produced by emulsion

polymerization, solution polymerization and bulk polymerization.

• Generally radical initiation is used (including living polymerization methods), but anionic polymerization of PMMA can also be performed.

• PMMA produced by radical polymerization (all commercial PMMA) is atactic and completely amorphous.

• To produce 1 kg (2.2 lb) of PMMA, about 2 kg (4.4 lb) of petroleum is needed.

Processing:• The glass transition temperature (Tg) of atactic PMMA is

105 °C. The Tg values of commercial grades of PMMA range from 85 to 165 °C (185 to 329 °F)

• All common molding processes may be used, including injection molding, compression molding, and extrusion.

• The highest quality PMMA sheets are produced by cell casting, but in this case, the polymerization and molding steps occur concurrently.

Preparation of monomer

C

C

H3C

O

H3C

O

CH2

Methyl methacrylate

H2SO4

125 OC

C

C

H3C

NH2 .H2SO4

O

CH2 CH3OH

H2OC

H3C

CH3HO

CN

Acetonecyanohydrin

Methacrylamidesulphate

Preparation

C

C

CH3

O

CH3

O

H2C C

C

CH3

O

CH3

O

H2C n

Methyl methacrylate Poly(methyl methacrylate)

polymerisation

Synthesis of PMMA via new techniques

• PMMA can be obtained by conventional methods of polymerization in emulsion resulting in particles in the range of 1 to 20 μm.

• Recently, other methods has been used for the synthesis of this polymer,among them sonochemistry using ultrasound waves as the source of energy.

Synthesis of PMMA…….

• Polymerization was carried out via free radicals from an aqueous solution of different concentrations of a cationic surfactant cetyltrimethylammonium bromide (CTAB) and different concentrations of the insoluble monomer Methyl Methacrylate (MMA) as the disperse phase.

• The reaction was carried out at a frequency of 20 kHz for 1 h under N2 atmosphere.

New method of preparation

H3C CH3

OH

CHO

2-hydroxy-2-methylpropanal

O

KMnO4H3C CH3

OH

COOH

H2SO4

H2C CH3

COOH

2-hydroxy-2-methylpropanoic acid methacrylic acid

CH3OHH2SO4

H3C

O

O CH3

methylmethacrylate

polymerisation

H3C

CH2

O

O CH3

n

polymethyl methacrylate

Chemical properties• PMMA is a linear thermoplastic about 70-75%

syndiotactic. Because of its lack of complete stereoregularity and bulky side groups, it is amorphous.

• Both isotactic and syndiotactic PMMA have been prepared but have not been offered commercially.

H3C

O

H3C

H3C

O

H3C

H3C

O

H3C

H3C

O

H3C

O O O O

The Isotactic PMMA chain

Chemical………• PMMA swells and dissolves in many organic solvents; it

also has poor resistance to many other chemicals on account of its easily hydrolyzed ester groups.

• It undergoes pyrolysis almost completely to monomer by a chain reaction because of the active radical and the α-methyl group that blocks the possibility of chain transfer reaction.

Physical properties• PMMA is strong and lightweight.• Outstanding properties include weatherability and

scratch resistance. • It has a density of 1.150–1.190 g/cm3 about less than

half that of glass and similar other plastics. • It also has good impact strength, higher than both glass

and polystyrene; however, PMMA's impact strength is still significantly lower than polycarbonate and some engineered polymers.

• PMMA ignites at 460 °C (860 °F) and burns, forming carbon dioxide, water, carbon monoxide and low molecular weight compounds, including formaldehyde.

• Comonomers such as butyl acrylate are often added to improve impact strength.

• Dyes may be added to give color for decorative applications, or to protect against (or filter) UV light.

• Fillers may be added to improve cost-effectiveness.

• Comonomers such as methacrylic acid can be added to increase the glass transition temperature of the polymer for higher temperature use such as in lighting applications.

:Modification of properties

• Transparent glass substitute• Daylight redirection• Medical technologies and implants• Artistic and aesthetic uses

Applications:

Applica……..• William Feinbloom introduced lenses made from PMMA,

contacts became much more convenient. These PMMA lenses are commonly referred to as "hard" lenses.

• PMMA is used as a shield to stop beta radiation emitted from radioisotopes.

• PMMA was used in laserdisc optical media and in 3D optical data storage

• PMMA, in a purified form, is used as the matrix in dye-doped solid-state gain media for solid state dye lasers.

• Artificial fingernails are made of acrylic. • Small strips of PMMA are used as dosimeter devices

during the Gamma Irradiation process.

• For many years, PMMA has been successfully depolymerised by contact with molten lead at about 500° C.; the monomer MMA can be obtained in a purity of more than 98%.

• Although this process gives MMA of high purity, the use of lead is undesirable, from an environmental viewpoint.

:PMMA Recycling

• It can be synthesized as a simple linear-chain structure or cross-linked. Polyacrylamide is not toxic. However, unpolymerized acrylamide, which is a neurotoxin, can be present in very small amounts in the polymerized acrylamide

:Polyacrylamide

Stability:• Chemical degradation occurs when the labile amine moiety

hydrolyzes at elevated temperature or pH, resulting in the evolution of ammonia and a remaining carboxyl group.Thus, the degree of anionicity of the molecule increases.

• Thermal degradation of the vinyl backbone can occur through several possible radical mechanisms, including the autooxidation of small amounts of iron and reactions between oxygen and residual impurities from polymerization at elevated temperature

• Mechanical degradation can also be an issue at the high shear rates experienced in the near-wellbore region.

Uses of polyacrylamide:

• One of the largest uses for polyacrylamide is to flocculate solids in a liquid.

• Another common use of polyacrylamide and its derivatives is in subsurface applications such as Enhanced Oil Recovery.

• It has also been advertised as a soil conditioner called Krilium by Monsanto Company in the 1950s.

• The ionic form of polyacrylamide has found an important role in the potable water treatment industry.

Sodium polyacrylate:

• Sodium polyacrylate, also known as waterlock, is a polymer with the chemical formula [-CH2-CH(COONa)-]n widely used in consumer products. It has the ability to absorb as much as 200 to 300 times its mass in water. Acrylate polymers generally are considered to possess an anionic charge. While sodium neutralized polyacrylates are the most common form used in industry, there are also other salts available including potassium, lithium and ammonium.

Mechanism:• Sodium Polyacrylate polymer can retain excessive

amounts of water because of the osmotic pressure (i.e. movement of water through a semipermeable membrane).Osmotic pressure induced by the high water concentration outside a sodium polyacrylate molecule draws the water into the center of the molecule. Sodium polyacrylate continues to absorb the water until there is an equal pressure of water inside and outside the sodium polyacrylate molecule.

Applications:• Sequestering agents in detergents. (By binding

hard water elements such as calcium and magnesium)• Thickening agents • Coatings• Fake snow • Super absorbent polymers

References:• From Wikipedia, the free encyclopedia• http://www.ehow.com• http://www.pslc.ws• http://www.heathland.nl/index.html• Microsc Microanal 11(Suppl 2), 2005 Copyright 2005

Microscopy Society of America• Journal of Microencapsulation, 2012, 1–15, Early Online

2012 Informa UK Ltd.• http://www.theinformedgardener.com