Phenolic Resins

CHEMICAL TECHNOLOGY

PROJECT

THUMATI VAMSI MADHAV – B130912CH

UDIT SINGHAL – B130575CH

T.NEELAVENI – B130726CH

SUBMITTED BY :

Phenolic Resins

INDEX

•HISTORY•ABOUT•PROPERTIES•TYPES OF RESINS•APPLICATIONS•ENGINEERING PROBLEMS•SUGGESTIONS

HISTORY

•The First phenolic resins were produced by poly condensation of phenol with aldehyde in 1860.•In 1860 ‘VON BAYER’ First reported the reaction between phenol and aldehyde•The phenol resin condensation was used industrially in 1902 by ‘BLUMMER’ for production of novalacs.

What is phenolic resin?•Phenolic resins are polycondensation products of phenols and aldehydes , in particular phenol and formaldehyde .•Phenolic resin is a heat-cured plastic formed from a reaction of a carbon-based alcohol and a chemical called aldehyde.•Formaldehyde is a common raw material for this type of resin , but others related chemicals can be used. The resin is hard, heat resistant, and can be mixed with a wide range of materials for industrial and residential uses.•Old phones were made of Bakelite , phenolic resin .

PHENOL-FORMALDEHYDEREACTIONS: CONDENSATIONS AND POLYMERIZATIONS

Phenyl formaldehyde resins• The reaction of phenol or substituted phenol with an

aldehyde, in the presence of an acidic or basic catalyst is used to prepare phenol formaldehyde resins.

• Uses: Phenolic resins are used in adhesives, coatings, and molding compounds.

• Heat of reaction: -180 cal/g

OH OH

(CH2OH)n

1

(CH2OH)n

2

+ (n1+n2) HCHO

NaOH

One step resin :

In these , all the necessary reactants (phenols, formaldehyde and catalyst) required to produce a thermosetting resin are charged into resin kettle in the proper proportions and react together .

An alkaline catalyst is used.

The resin, as charged from the kettle, is thermosetting or heat-reactive and rquires only further heating to complete the reaction to an infusible, insoluble state

Two step resins :• Only part of the necessary formaldehyde is added in the kettle in making these resins, and an acid catalyst is used.•They are permanently fusible or thermoplastic when discharged from the kettle but react with additional formaldehyde to produce a thermosetting resin

Flow chart:

Why Phenolic Resin?

Superior Creep Resistance

Strength and stability under load

Low weight high strength and modulus

Strength and rigidity

Chemically Resistant

Harsh marine environment

Excellent flammability resistance and low smoke and toxicity

Increased level of safety

High carbon and char yield

Retains level of strength and integrity should fire break out

Phenolic’s high modulus and excellent heat and creep resistance resists

fracture under pressure as proven in industry “Conductivity test”

Why Phenolic Resin?

Phenolic resins are yellow to brown in colour and the coloration can be very intense. Pale phenolic resin become colored immeditately after production during storage or processing. The coloration is less intense only int eh case of phenolicresins from para-alky-substituted phenols

The Viscosity of phenolic resins or their solution is measure at hightconcentrations, e.g. in 30-80% solution.

Cross-linked phenolic resins are hard substances which only have a small fracture strain and cannot be melted. Phenolic resins can be plasticized. Their compatibility with plasticizers can be adjusted by introduction of hydrophilic or hyrdrophobic groups.

Physical Properties

There are Two Types of Phenolic Resins

NovolacMolar excess of phenol

Require an external curing agent

Usually

hexamethylenetetramine

ResolTypically there is a molar excess of

formaldehyde

Do not require an external curing

agent

Single Stage

Six month shelf life

NOVOLAC•Novolak resins are typically cured with 5–15% hexa as the cross-linking agent. The reaction mechanism and reactive intermediates have been studied by classical chemical techniques (3,4) and the results showed that as much as 75% of nitrogen is chemically bound. More recent studies of resin cure (50–53) have made use of TGA, DTA, GC, IR, and NMR . They confirm that the cure begins with the formation of benzoxazine , progresses through a benzylamine intermediate, and finally forms (hydroxy)diphenylmethanes (DPM).

•IN the formation of novolacs, substitution in condensation reactions occur simultaneous. In large reaction vessels formaldehyde is metred to a phenol –catalyst mixture and the rate of addition is controlled depending on the head evolved for safety reasons. When using smaller vessels, even under laboratory conditions, care must be take cbecause of exothermic reaction.

Used in :Tackifiers for Rubber, as a varnish, Raw materials for Epoxy resins, Thermosets, grinding wheels, printing technology, Positive offset printing plates.

Resol

The production of resols differs from that of novolacs in that the reactions

between phenol and formaldehyde are not allowed to go to completion but are

stopped at the stage where auto-cross-linking resols are still liquid or soluble.

The continuation of the condensation reactions beyond the resol stage leads

to resins which are no longer soluble but can only be swelled and which are

known as resitols.

The final cross-linking to from resitoles gives completely cross-linked plastics.

In resol production, the concentration for formaldehyde and the degree of

condensation must be controlled during the reaction.

Uses of Resol

● Interior of Vehicles.

● Construction Adhesives.

● Abrasives.

● Foamed Plastics

● Fiber Bonding

● Decorative Laminates

● Chipboard Adhesive

● Binding agents for molding sand.

Corrosive coatings for

Storage tanks, semi tank trailers, railroad tank cars, fans blowers, and fin tube coils

Other Applications

Binder for

Friction pads, brake pads, grinding wheels, plywood and particle board

Wear Resistance

Gas meter valves, pump seals, caster wheels

Dimensional Stability & Thermal Performance

Brake pistons, transmission parts, electrical motor brush cards

Electrical insulation

terminal strips, commutators, capacitor cans and caps

Engineering Problems•All the raw materials and catalyst were charged to the reactor at once followed by the addition of heat.•Heat generated exceeded the cooling capacity of the system •Excessive pressure generated by a runaway reaction. •Pressure generated could not be vented through the emergency relief system.

•Accumulation of Formaldehyde

•Deviation from process

•Poor agitation

•Improper heating or cooling

SUGGESTIONS

•Modify processes to improve inherent safety.•Minimize the potential for human error. •Understand events that may lead to an overpressure and eventually to vessel rupture. •Use lessons learned. •Evaluate Standard Operating Practices. •Evaluate employee training and oversight. •Evaluate the effectiveness of the emergency relief system.

Thank you