EXPERIMENT- 7(A)
AIM: AIM: - To To prepare phenol formaldehyde resin. (Bakelite)
CHEMICALS USED: USED: - Glacial acetic acid, 40% formaldehyde solution, henol, conc. ! "#$4 .
APPARATUS APPARATUS REQUIRED REQU IRED:: -Glass rod, eakers, funnel, measurin& cylinder, cylinder, dropper and filter paper. filter paper. PRINCIPLE: - henol formaldehyde resins ('s) are condensation polymers and are otained y condensin& phenol ith formaldehyde in the presence of an acidic or alkaline catalyst. They ere first prepared y Backeland , an merican *hemist ho &a+e them the name as Bakelite. These are thermosettin& polymers. Thermosets:Thermosets:- The polymers hich on heatin& chan&e irre+ersily into hard ri&id and infusile materials are called thermosettin& polymers. These polymers are usually prepared y heatin& relati+ely lo molecular mass, semi fluid polymers, hich ecomes infusile and f orm an insolule hard mass on heatin&. The hardenin& on heatin& is due to the formation of etensi+e cross-linkin& eteen different polymeric chains. This lead to the formation of a -imnesional netork of on ds connectin& the polymer chains. #ince the netork structure is ri&id and does not soften on heatin&, the thermosettin& polymers can not e reprocessed. #ome important eamples of thermosettin& polymers are /rea-'ormaldehyde resin and elamine-'ormaldehyde resins.
Properties:henolhenol- formaldehyde resins ha+in& lo de&ree of polymeri1ation are soft. They possess ecellent adhesi+e properties and are usually used as ondin& &lue for l aminated ooden planks and in +arnishes and lackuers.
henol- formaldehyde resins ha+in& hi&h de&ree of polymeri1ation are hard, ri&id, scratch-resistant and infusile. They are resistant to non-oidisin& acids, salts and many or&anic sol+ents. They can ithstand +ery hi&h temperatures. They act as ecellent electrical insulators also.
Uses:They are used for makin& moulded articles such as radio and T2 parts, coms, fountain pen arrels, phono&raph records etc. They are used for makin& decorati+e laminates, all co+erin&s etc.
They are used for makin& electrical &oods such as sitches, plu&s etc.
They are used for impre&natin& farics ood and paper.
They are used as ondin& &lue for for laminated ooden planks and in +arnishes and lackuers. #ulphonated phenol-formaldehyde resins are use as ion-echan&e resins.
Preprtio!:- 's are prepared y reaction of phenol ith formaldehyde in the presence of acidic or asic catalyst. The process may e carried out as follos miture of phenol and formaldehyde are alloed to react in the presence of a catalyst. The process in+ol+es formation of methylene rid&es in ortho, para or both ortho and para positions. This results first in the formation of linear polymer (*alled NOVALAC ) and then in to cross-linked polymer called phenol-formaldehyde resin or bakelite.
PR"CEDURE: lace 3ml of &lacial acetic acid and ".3ml of 40% formaldehyde solution in a 300ml eaker and add " &rams of phenol. dd fe ml of conc. #ulphuric acid into the miture carefully. ith in 3 min. a lar&e mass of plastic is formed. The residue otained is ashed se+eral times ith distilled ater, and filtered product is dried and yield is calculated.
RESULT: - The ei&ht of the phenol formaldehyde resin is 555 &. PRECAUTI"NS: The reaction is sometimes +i&orous and it is etter to e a fe feet aay from the eaker hile addin& the ! "#$4 and until the reaction is complete. The eperiment should e preferaly carried out in fume cupoard.
QUESTI"NS #AN$: henol formaldehyde is also called as. hat do you understand y resin6 Gi+e main uses of the phenol formaldehyde resin. hat type of co-polymer is phenol formaldehyde resin6 Briefly descrie the properties of phenolic resins. rite chemical e7uations for preparation of phenolic resins.
S%et& I!str'tio!s henol:- ost phenols are harmful if inhaled, in&ested or asored throu&h skin. Thay cause se+ere irritation or dama&e to skin and eyes. #ome phenols are suspected carcino&en, should not inhale its dust or +apor, ear &lo+es and a+oid contact.
!"#$4:- 8t is poisnous and corrosi+e. *ontact or inhalation can cause se+ere dama&e to the eyes, skin and respiratory tract. ear &lo+es and dispense under a hood, a+oid contact and do not reathe the +apour
