Plasticizers for plastics | Triphenyl phosphate | Safer plasticizers

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Plasticizer

Plasticizers are additives that increase the plasticity or fluidity the material to which they are added, these include plastics, cement, concrete and clay bodies. Although the same compounds are often used for both plastics and concretes, the desired effect is slightly different. The plasticizers for plastics soften the final product increasing its flexibility. Plasticizers for concrete soften the mix before it hardens, increasing its workability, and are usually not intended to affect the properties of the final product after it hardens.


Plasticizers for plastics

Plasticizers for plastics are additive, most commonly phthalates, that give hard plastics like PVC the desired flexibility and durability. They are often based on esters of polycarboxylic acids with linear or branched aliphatic alcohols of moderate chain length. Plasticizers work by embedding themselves between the chains of polymers, spacing them apart (increasing of the "free volume"), and thus significantly lowering the glass transition temperature for the plastic and making it softer. For plastics such as PVC, the more plasticiser added, the lower its cold flex temperature will be. This means that it will be more flexible, though its strength and hardness will decrease as a result of it. Some plasticizers evaporate and tend to concentrate in an enclosed space; the "new car smell" is caused mostly by plasticizers evaporating from the car interior.

Dicarboxylic/tricarboxylic ester-based plasticizers

Phthalate-based plasticizers are used in situations where good resistance to water and oils is required. Some common phthalate plasticizers are:

Bis(2-ethylhexyl) phthalate (DEHP), used in construction materials, food packaging, children toys, medical devices, and cling wrap

Diisononyl phthalate (DINP), found in garden hoses, shoes, toys, and building materials

Bis(n-butyl)phthalate (DnBP, DBP), used for cellulose plastics, food wraps, adhesives, perfumes and also in cosmetics - about a third of nail polishes, glosses, enamels and hardeners contain it, together with some shampoos, sunscreens, skin emollients, and insect repellents

Butyl benzyl phthalate (BBzP) is found in vinyl tiles, traffic cones, food conveyor belts, artificial leather and plastic foams

Diisodecyl phthalate (DIDP), used for insulation of wires and cables, car undercoating, shoes, carpets, pool liners

Di-n-octyl phthalate (DOP or DnOP), used in flooring materials, carpets, notebook covers, and high explosives, such as Semtex. Together with DEHP it was the most common plasticizers, but now is suspected of causing cancer

Diisooctyl phthalate (DIOP), all-purpose plasticizer for polyvinyl chloride, polyvinyl acetate, rubbers, cellulose plastics and polyurethane.

Diethyl phthalate (DEP)

Diisobutyl phthalate (DIBP)

Di-n-hexyl phthalate, used in flooring materials, tool handles and automobile parts

Trimellitates are used in automobile interiors and other applications where resistance to high temperature is required. They have extremely low volatility.

Trimethyl trimellitate (TMTM)

Tri-(2-ethylhexyl) trimellitate (TEHTM-MG)

Tri-(n-octyl,n-decyl) trimellitate (ATM)

Tri-(heptyl,nonyl) trimellitate (LTM)

n-octyl trimellitate (OTM)

Adipate-based plasticizers are used for low-temperature or resistance to ultraviolet light. Some examples are:

Bis(2-ethylhexyl)adipate (DEHA)

Dimethyl adipate (DMAD)

Monomethyl adipate (MMAD)

Dioctyl adipate (DOA)

Sebacate-based plasticiser

Dibutyl sebacate (DBS)

Maleates

Dibutyl maleate (DBM)

Diisobutyl maleate (DIBM)

Other plasticisers

Benzoates
Epoxidized vegetable oils
Sulfonamides
N-ethyl toluene sulfonamide (o/p ETSA), ortho and para isomers
N-(2-hydroxypropyl) benzene sulfonamide (HP BSA)
N-(n-butyl) benzene sulfonamide (BBSA-NBBS)
Organophosphates
Tricresyl phosphate (TCP)
Tributyl phosphate (TBP)
Glycols/polyethers
Triethylene glycol dihexanoate (3G6, 3GH)
Tetraethylene glycol diheptanoate (4G7)


Polymeric plasticizers

Some other chemicals working as plasticizers are nitrobenzene, carbon disulfide and β-naphthyl salicylate. Plasticizers, such as DEHP and DOA, were found to be carcinogens and endocrine disruptors.


Safer plasticizers

Safer plasticizers with better biodegradability and less biochemical effects are being developed. Some such plasticizers are:

Acetylated monoglycerides; these can be used as food additives

Alkyl citrates, used in food packagings, medical products, cosmetics and children toys

Triethyl citrate (TEC)

Acetyl triethyl citrate (ATEC), higher boiling point and lower volatility than TEC

Tributyl citrate (TBC)

Acetyl tributyl citrate (ATBC), compatible with PVC and vinyl chloride copolymers

Trioctyl citrate (TOC), also used for gums and controlled release medicines

Acetyl trioctyl citrate (ATOC), also used for printing ink

Trihexyl citrate (THC), compatible with PVC, also used for controlled release medicines

Acetyl trihexyl citrate (ATHC), compatible with PVC

Butyryl trihexyl citrate (BTHC, trihexyl o-butyryl citrate), compatible with PVC

Trimethyl citrate (TMC), compatible with PVC


Plasticizers for energetic materials

For energetic materials, especially propellants (eg. smokeless powders), plasticizers based on nitrates are frequently employed. Some such plasticizers are:

Nitroglycerine (NG)
Butanetriol trinitrate (BTTN)
Dinitrotoluene (DNT)
Metriol trinitrate (METN)
Diethylene glycol dinitrate (DEGN)
Bis(2,2-dinitropropyl)formal (BDNPF)
Bis(2,2-dinitropropyl)acetal (BDNPA)
2,2,2-Trinitroethyl 2-nitroxyethyl ether (TNEN)

Due to the secondary alcohol groups, NG and BTTN have relatively low thermal stability. METN, DEGN, BDNPF and BDNPA have relatively low energies. NG and DEGN have relatively high vapor pressure.


Plasticizers for concrete production

Superplasticizers are chemical admixtures that can be added to concrete mixtures to improve workability. Strength of concrete is inversely proportional to the amount of water added or water-cement (w/c) ratio. In order to produce stronger concrete, less water is added, which makes the concrete mixture very unworkable and difficult to mix, necessitating the use of plasticizers and superplasticizers.

Superplasticizers are also often used when pozzolanic ash is added to concrete to improve strength. This method of mix proportioning is especially popular when producing high strength concrete and fiber reinforced concrete.

Adding 2% superplasticizer per unit weight of cement is usually sufficient. However, note that most commercially available superplasticizers come dissolved in water, so the extra water added has to be accounted for in mix proportioning. Adding an excessive amount of superplasticizer will result in excessive segregation of concrete and is not advisable. Some studies also show that too much superplasticizer will result in a retarding effect.

Plasticizers are commonly manufactured from lignosulfonates, a by-product from the paper industry. Superplasticizers have generally been manufactured from sulfonated naphthalene formaldehyde or sulfonated melamine formaldehyde, although new generation products based on polycarboxylic ethers are now available. Traditional lignosulfonate based plasticisers and naphthalene and melamine based superplasticisers disperse the flocculated cement particles through a mechanism of electrostatic repulsion (see colloid). In normal plasticisers, the active substances are adsorbed on to the cement particles, giving them a negative charge, which leads to repulsion between particles. Naphthalene and melamine superplasticisers are organic polymers. The long molecules wrap themselves around the cement particles, giving them a highly negative charge so that they repel each other.

Polycarboxylate Ethers (PCE), the new generation of superplasticisers are not only chemically different from the older sulphonated melamine and naphthalene based products but their action mechanism is also different, giving cement dispersion by steric stabilisation, instead of electrostatic repulsion. This form of dispersion is more powerful in its effect and gives improved workability retention to the cementitious mix. Furthermore, the chemical structure of PCE allows for a greater degree of chemical modification than the older generation products, offering a range of performance that can be tailored to meet specific needs.

In ancient times, the Romans used blood as a superplasticizer for their concrete mixes.
Plasticisers can be obtained by your local concrete manufacturerHousehold washing up liquid may also be used as a simple plasticizer.

ORGANO PHOSPHATE ESTERS

Triphenyl Phosphate (T.P.P)

Chemical Name : Triphenyl Phosphate

Uses
Polyester fibers, Poly Carbonate triacetate,
NC, Photographic films, Cellulose acetate,
ethyl cellulose & cellulose acetate butyrate.

Typical properties :
Physical appearance :White flake
Phosphorus content: wt % 9.5
Specific gravity @ 60° C / 60 ° C :1.220
Melting Point °C :48° C
Acidity as phosphoric acid: % 0.003
Applications :


PAC’S TPP ( Triphenyl Phosphate ), a white flake having low iron content, meets the known specification of all major manufacturers of photographic safety film, It is a recognized organophosphorus flame retardant used in films sheetings, mouldings and certain coatings. Others important properties are its toughening ability and extremely low volatility in cellulose acetate and triacetate, its good resistance to extremely low volatility in cellulose Acetate and triacetate its good resistance to moisture, and its lack of odour. In most applications, it is combined with other plasticizers but it can be used as a primary flame retardant plasticizers in cast triacetate film and sheeting. These products are clear, tough and tack free, It also improves dimensional stability and dielectric strength. Other applications are in moulded acetate products and in coating based in nitrocellulose , ethyl cellulose and cellulose acetate butyrate.PAC’ S TPP when used in large proportions is usually combined with a solvent plasticizer to avoid crystallization and a consequent separation, as it is a solid at room temperature. It is more compatible with cellulose triacetate than with secondary cellulose acetate, but can be incorporated in the latter up to about 30 phr without separation. In secondary cellulose acetate, cellulose acetate butyrate, and ethyl cellulose, for film sheeting or moulding material, it is generally combined with other more active plasticizer such as dimethyl phthalate, dimethoxy ethyl phthalate or diethyl phthalate. It can be used alone in cast triacetate film and sheeting, where, as a very approximate guide, the top limit is 35 phr, or less ( 20-25 phr) under severe service conditions. The approximate top limit in melt-extruded sheeting of film is 15 phr of triphenyl phosphate, and injection moulding material it is about 20 phr. Triphenyl phosphate is compatible with cellulose nitrate in amounts up to equal proportions of plasticizer and resin.

Other films and sheetings :

Triphenyl phosphate as a plasticizer toughens cellulose acetate and imparts a good balance of properties in other films and sheeting. A solvent plasticizer is generally used along with triphenyl phosphate will reduce cold flow and improved tensile strength. Impact strength is correspondingly reduced. Ultraviolet-light stability is average. Whereas phthalate plasticizers and triacetin tend to increase the flammability of a cellulose acctate composition, triphenyl phosphate reduces flammability considerably. Cellulose acetate sheeting containing 20 phr or more triphenyl phosphate will not continue to burn when ignited and the flame withdrawnMoulding compostions : Typical moulding applications of triphenyl phosphate are in cellulose acetate, cellulose acetate butyrate, and vinyl copolymer compound which are used in records, vacuum cleaner parts, housings for clocks and appliances, and parts for Christmas tree lighting sets. Triphenyl phosphate is recommended for use in compounds for records based on vinyl chloride-vinyl acetate copolymer for several reasons. Up to 50 % by weight of fillers must be added to the resin to prevent heat distortion, and up to 5 phr triphenyl phosphate is added to wet these fillers. Its wetting actions is possible because it melts at a slightly lower temperature than the resin. It also functions as a surface – active agent in the calendaring process, and as an internal lubricant improving flow characteristics when the records is moulded. As a plasticizer, it controls brittleness in the final product. Its heat stability, low water absorption and low volatility are all advantages over other plasticizer that has been used in these applications.

Benefits :
It is used principally as a non-solvent plasticizer for cellulose acetate films having up to 80% retentivity and giving flexibility and toughness to the films An excellent catalyst/inhibitor/chain terminator for the growing polymer chain for the manufacture of polyester fibre An excellent fire retardant and plasticizer for synthetic resins viz. Phenol formal-dehyde, decorative laminated sheets etc. It is also used in making stencil blanks, dopes films, varnishes, enamels, plastics, lacquers and for impregnating roofing paper


Tricresyl Phosphate (T.C.P.)
Phosphorus Flame Retardant

TCP ( Tricresyl Phosphate ) is a low viscosity synthetic phosphate ester, Tricresyl Phosphate finds uses in wide variety of applications as Flame retardant plasticizer.

Uses
Leather cloth (PVC) : Upholstery, Book binding, Seat covers
Utility articles : Footwear, Raincoats, Handbags, Fiber glass cellulose acetate
Extruded articles : Cables (PVC & rubber), hoses, flexible pipe, coal mining, conveyor belts
Coatings : Nitrocellulose lacquers, phenolic resins, lube oils

Typical properties :

Physical appearance:Clear Liquid
Phosphorus content:wt % 8.4
Specific gravity @ 25° C :1.17±0.01
Boiling Point (decomposes )°C :415° C
Flash Point °C :220°C
Solubility (G/100 g Solvent) :Water Insoluble ,Completely soluble in Toluene, Methyl Ethyl Ketone, Methanol

TCP is recommended for use in plastisols for fabrics coating & other applications where its low, stable viscosity offers improved processing. TCP can give a driver finish to coated fabrics. TCP has high plasticizing efficiency that enables formulator to achieve better flame retardance at lower cost. It can also be used as flame retardant in phenolic laminatesThe use of proper equipment is recommended. Excess exposure to the product should be avioded. Wash thoroughly after handling.
Product should be stored in cool, dry and well ventilated area away from incompatible materials.
Unless stated, shelf life of the product will be 12 months from the date of packing. For additional handling & toxicological information, consult PAC Material safety Data sheet. Triaryl Phosphate (T.A.P.)
Phosphorus Flame RetardantTAP ( Triaryl Phosphate ) is a low viscosity synthetic Triaryl phosphate ester, Triaryl Phosphate finds uses in wide variety of application as Flame retardant plasticizer

Synthesis of Bombycol

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Synthesis of Bombycol

Structure of Bombycol

Synthesis of Bombycol


Synthesis:


Paterno-Büchi Reaction

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Paterno-Büchi Reaction

In this reaction photoinduced oxetane is formed by the photochemical [2+2] cycloaddition of a carbonyl with an olefin.







Mechanism:
The possible transitions (C=O) are shown below:
Once the carbonyl ground state has been photoexcited, either a singlet or triplet state may be formed:






Either type of transition (n,π* and π,π*) and electronic state (singlet, triplet) may participate in the first stage of this reaction, which is rationalized by invoking diradical intermediates:





Breaking of the new σ-bonds requires more energy, and the reverse reaction is not possible using same light frequency.
Application:





















Diatropic ring | Ring currents in large [4n + 2]-annulenes

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Ring currents in large [4n + 2]-annulenes

Alessandro Soncini, Patrick W. Fowler and Leonardus W. Jenneskens

Reported computational results for large [4n + 2]-annulenes indicate a falling off of aromaticity in D3h geometries but its retention in D6h geometries, as diagnosed on both energetic and magnetic criteria. Ipsocentric pseudo- mapping of the current density induced by a perpendicular external magnetic field shows that ring currents follow this trend.
Diatropic ring currents are quenched in D3h geometries but survive in D6h geometries of [4n + 2]-annulenes (4n + 2 = 30, 42, 54, 66). Ipsocentric orbital contributions explain this distinction in terms of the translational/diatropic, rotational/paratropic selection rules for current in monocycles, coupled with an account of differential angular-momentum mixing in D3h and D6h symmetries. The orbital model rationalises the differences between D6h and D3h geometries, accounts for the decay of aromaticity with ring size for D3h[4n + 2]-annulenes, and predicts trends for anti-aromatic [4n]-annulenes in the two symmetry groups.

• Mass Spectrometry | Ultraviolet-Visible Spectroscopy | Infrared Spectroscopy

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Spectroscopy

The spectroscopic techniques described below do not provide a three-dimensional picture of a molecule, but instead yield information about certain characteristic features. A brief summary of this information follows:

• Mass Spectrometry: Sample molecules are ionized by high energy electrons. The mass to charge ratio of these ions is measured very accurately by electrostatic acceleration and magnetic field perturbation, providing a precise molecular weight. Ion fragmentation patterns may be related to the structure of the molecular ion.

Ultraviolet-Visible Spectroscopy:

Absorption of this relatively high-energy light causes electronic excitation. The easily accessible part of this region (wavelengths of 200 to 800 nm) shows absorption only if conjugated pi-electron systems are present.

• Infrared Spectroscopy:

Absorption of this lower energy radiation causes vibrational and rotational excitation of groups of atoms. within the molecule. Because of their characteristic absorptions identification of functional groups is easily accomplished.

Types of Phospholipid | Phosphoglycerides | Sphingomyelin

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Phospholipid

Phosphatidyl choline is the major component of lecithin. It is also a source for choline in the synthesis of acetylcholine in cholinergic neurons.
Phospholipids are a class of lipids, and a major component of all biological membranes, along with glycolipids, cholesterol and proteins. Understanding of the aggregation properties of these molecules is known as lipid polymorphism and forms part of current academic research.
Components
They are built upon to a nitrogen-containing alcohol like ethanolamine or an organic compound such as choline. The "head" of the phospholipid is polar and the "tails" are non-polar.

Types of Phospholipid

Phosphoglycerides

In phosphoglycerides, the carboxyl group of each fatty acid is esterified to the hydroxyl groups on carbon-1 and carbon-2 of the glycerol molecule. The phosphate group is attached to carbon-3 by an ester link. This molecule, known as a phosphatidate, is present in small quantities in membranes, but is also a precursor for the other phosphoglycerides.
In phosphoglyceride synthesis, phosphatidates must be activated first. Phospholipids can be formed from an activated diacylglycerol or an activated alcohol.

Phosphatidyl serine and phosphatidyl inositol are formed from a phosphoester linkage between the hydroxyl of an alcohol (serine or inositol) and cytidine diphosphodiacylglycerol (CDP-diacylglycerol).
In animals, plants and yeast the synthesis of phospatidyl ethanolamine, the alcohol is phosphorylated by ATP first, and subsequently reacts with cytidine triphosphate (CTP) to form the activated alcohol (CDP-ethanolamine). The alcohol then reacts with a diacylglycerol to form the final product. In bacteria, the serine moiety of Phosphatidyl serine is decarboxylated to give phospatidyl ethanolamine.
In mammals, phosphatidyl choline can be synthesized via two separate pathways; a series of reactions similar to phosphatidyl ethanolamine synthesis, and the methylation of phosphatidyl ethanolamine, which is catalyzed by phosphatidyl ethanolamine methyltransferase, an enzyme produced in the liver.

Phosphatidyl ethanolamine is the major component of cephalin.

Sphingomyelin

The backbone of sphingomyelin is sphingosine, an amino alcohol formed from palmitate and serine. The amino terminal is acylated with a long-chain acyl CoA to yield ceramide. Subsequent substitution of the terminal hydroxyl group by phosphatidyl choline forms sphingomyelin.

Sphingomyelin is also present in all eukaryotic cell membranes, especially the plasma membrane, and is particularly concentrated in the nervous system because sphingomyelin is a major component of myelin, the fatty insulation wrapped around nerve cells by Schwann cells or oligodendrocytes. Multiple sclerosis is a disease characterised by deterioration of the myelin sheath, leading to impairment of nervous conduction.


Amphipathic character

Due to its polar nature, the head of a phospholipid is hydrophilic (attracted to water); the lipophilic (or often known as hydrophobic) tails are not attracted to water. When placed in water, phospholipids form one of a number of lipid phases. In biological systems this is restricted to bilayers, in which the lipophilic tails line up against one another, forming a membrane with hydrophilic heads on both sides facing the water. This allows it to form liposomes spontaneously, or small lipid vesicles, which can then be used to transport materials into living organisms and study diffusion rates into or out of a cell membrane.

This membrane is partially permeable, capable of elastic movement, and has fluid properties, in which embedded proteins (integral or peripheral proteins) and phospholipid molecules are able to move laterally. Such movement can be described by the Fluid Mosaic Model, that
describes the membrane as a mosaic of lipid molecules that act as a solvent for all the substances and proteins within it, so proteins and lipid molecules are then free to diffuse laterally through the lipid matrix and migrate over the membrane. Cholesterol contributes to membrane fluidity by hindering the packing together of phospholipids. However, this model has now been superseded, as through the study of lipid polymorphism it is now known that the behaviour of lipids under physiological (and other) conditions is not simple.

Heat Temperature and the Particle Theory | Expanding and Contracting

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Heat, Temperature, and the Particle Theory

What actually is the difference between water at 20ºC and water at 50ºC?
What is the difference between heat and temperature?
How are these questions related?
Can any one hypothesis answer both questions?

The Particle Theory

Scientists over the years came up with many ideas, or hypotheses, to try to explain the difference between heat and temperature. One such hypothesis was thought of by Lavoisier. He suggested that heat might be a substance with mass, which he called caloric. But Lavoisier's idea was not supported by experimental observations, and scientists looked for other ways to explain heat.
Scientists now use the kinetic molecular theory, or particle theory, to explain heat and temperature and the difference between, say, 20ºC and 50ºC. The particle theory is based on a model that suggests that all matter is made up of tiny particles too small to be seen. According to this model, these particles are always moving- they have energy. The more energy they have, the faster they move. So far, all the evidence is made up of moving particles. That is why we call the particle model for matter a theory.


So what is the difference between heat and temperature? According to the particle theory, heat is energy, and it is transferred from hotter substances to colder ones. Temperature is a measure of the average energy level of the particles in a substance.
Both hot and cold water are made up of moving particles, some moving quickly, and some moving slowly. But on average, the particles move faster in hot water than in cold water.

Expanding and Contracting

The particle theory is a useful model to explain why substances expand when they are heated and contract when they are cooled. At high temperatures, particles have more energy, move more quickly, and have more collisions. As a result, they take up more space, and the substance expands. At lower temperatures, particles have less energy, move more slowly, and have fewer collisions. They take up less space, and the substance contracts.

Self Check
In your own words, describe the difference between heat and temperature.
Two cups contain the same amount of water. a) What device would be best for comparing the average energy of the particles of each sample of water? b) Explain how this device would help you compare the energies of the particles.
Apply
Use the particle theory to explain how an outdoor thermometer works.
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