PHENOLIC RESINS PROF. PRAKASH MAHANWAR PROF. PRAKASH MAHANWAR HEAD, DEPT.OF POLYMER TECHNOLOGY & DEPT. OF SURFACE COATINGS INSTITUTE OF CHEMICAL TECHNOLOGY MATUNGA, MUMBAI-400 019
Phenolic resins are the oldest commercially manufactured synthetic polymer. They were first 'invented' by Leo Hendrik Baekland in 1907. He was the one to develop an economical method to was the one to develop an economical method to convert these resins to moldable formulations which were transformed by heat and pressure to hard and resistant molded parts.
Why Phenolic Resins?? � Phenolic resins are distinguished by broad array of application areas amongst Thermosetting and Thermoplastic resins. � They are relatively inexpensive and highly versatile having vital role in construction, automotive, electrical, and appliance industries. � They are irreplaceable materials for selective high technology applications offering high reliability under severe circumstances.
Continued… � Prominent features of Phenolic Resins are: - Excellent thermal behavior -High Strength level -Long thermal and mechanical stability. -Excellent fire, smoke,and low toxicity characteristics. -Excellent electrical and thermal insulating capabilities. -Excellent cost performance characteristics.
Market scenario � According to the Chemical Economics the global market for Phenolic resins had reached 2.46 million tonnes by 1997 (on a 100% resin weight basis) with 39% of demand in NAFTA, 24% in Europe, 5% in 39% of demand in NAFTA, 24% in Europe, 5% in Japan and the balance of 33% in other regions in 2005 where as in 2008 the rate of increase in worldwide market was 8-12% than 2005.
world consumption of Phenolic resins
Basic Chemistry Phenolic resins are obtained by step growth polymerization of difunctional monomers (aldehydes) with monomers of functionality greater than 2 (Viz, Phenol, substituted Phenols or combination of phenols). Key factors in the design of the desired phenolic resin are: - Molar ratio of F to P - Mode of catalysis: Acid, base, metal salt, enzyme. - Mode of catalysis: Acid, base, metal salt, enzyme. -Liquid, Solid, dispersion -Thermoplastics or thermosetting Low to medium Mw are considered as “ Reactive intermediates which can be cured or undergo various transformation reactions via reactive hydroxyl group viz, Epoxy,allyl, cyanate or form new ring structure. REACTION OF PHENOLAND ALDEHYDE UNDER ACIDIC OR BASIC CATALYST ARE EXOTHERMIC REACTIONS ( SIDE REACTIONS DUE TO EXOTHERM NEEDS TO BE AVOIDED)
PHENOLIC RESINS THERMOSETTING RESINS RESOL THERMOPLASTIC RESINS NOVOLAC RESINS RESINS FIP< 1 MONOMERS: FIP>1 A. Phenol- OH OH OH OH OH CH 3 C C CH 3 CH 3 (CH 2 ) 7 CH 3 (CH 2 ) 7 CH 3 CH 3 CH CH 3 p-PHENYL PHENOL CRESOL p-t-BUTYL p-OCTYL (o/m/p) PHENOL PHENOL PHENOL OH OH OH CH 3 HO C OH OH CH 3 C 15 H 27 CH 3 (CH 2 ) 8 p-NONYL RESORCINOL CARDANOL BISPHENOL 'A' PHENOL
RAW MATERIAL AND CATALYST � - Phenol, o,m,p-Cresol, p-tert Butylphenol, p-tert Octylphenol, p-Tert Nonylphenol, (2,3), (2,4), (2,5), (2,6), (3,4), (3,5) – Xylenol, Resorcinol, Bisphenol A, Bisphenol-F, CNSL, BNSL , etc. � - Formaldehyde, Acetaldehyde, Propionaldehyde, n- butyraldehyde, Isobutyraldehyde, Glyoxal, Furfural, etc. butyraldehyde, Isobutyraldehyde, Glyoxal, Furfural, etc. � Catalyst: -Acid: Organic Acids and Mineral acids -Base: NaOH, KOH -Metal salts -Enzymes
Contd. � Mode of catalysis and molar ratio of F to P decides the type and property of Phenolic resin. � Mode of Catalysis dictates the overall property of Resin. � Depending on type of catalyst and ratio: � Base catalyst: Resol, F/P >1, Liquid, solid, solution/limited stability � Acid Catalyst: : Novolak, F/p <1, Solid, stable � Metal Salts: Resol/Novolak, F/P >1, Liquid/Solid , Varying stability � Enzymes: Pseudo Novolak, No ( CH 2 O), Solid, stable. � Phenols of lower functionality are used to incorporate special properties in the resin. � Formaldehyde is preferred because of its high reactivity and freedom from side reactions VARYING F/P RATIO, TYPE OF CATALYST ONE CAN TAILOR THE PRODUCT WITH: - Required Melting Range - Required Molecular weight - Required functional groups available for modifications. Three reaction sequences must be considered: 1. Formaldehyde addition to phenol. 2. Chain growth or prepolymer formation. 3. Cross linking or curing reaction.
PHENOLIC RESIN PROCESSSES PHENOL PHENOL (EXCESS) + + FORMALDEHYDE (EXCESS) FORMALDEHYDE + + BASIC CATALYST ACIDIC CATALYST RESOLES NOVOLAC NOVOLAC (THERMOSETTING RESINS) (THERMOSETTING RESINS) RESITE CURED RESINS ONE STAGE PROCESS TWO STAGE PROCESS
Phenolic Resin Chemistry Formaldehyde Reactions - Monomers react with formaldehyde under different conditions to make different products -Reacting under acid conditions yields thermoplastic resins (Novolaks) resins (Novolaks) -Reacting under base conditions yields reactive resins (Resoles) -Resole resins can be used for curing of elastomers
Curing Of Resin � Complex polymer with multiple reactive sites (resole resin) � Undergoes multiple reactions simultaneously � Activated by halogens (resinous, elastomeric,or metallic salts) � Activated by halogens (resinous, elastomeric,or metallic salts) � Requires zinc source for best results
Two prepolymers types are obtained depending on pH Type of phenolic resin Novolac Resols Type of reaction Electrophilic aromatic Nucleophilic substitution mechanism Medium (pH) Acidic medium(1-5) Alkaline medium(>7) Molar ratio P/F 1:0.80 1 : 1 to 1 : 3 Type of polymer Linear or slightly Branched branched Characteristic property Low MW, soluble and Insoluble and infusible permanently fusible
Varients and their Effect General Ratio: p,p’:o,p’:o,o’1:2:1 � Catalyst: � F/P Ratio : Softening Range � 4-6 pH With Divalent metal salts as � 1:065 : 60-70 catalyst: High Ortho (57-58%: o-o, 40-42%: o-p and 2-3% p-p) � 1:075 : 70-75 � 1:075 : 70-75 � Oxalic Acid: (25-26%: o-o, 48-50%: o- � 1:085 : 80-100 p and 25-30% p-p) � Phosphoric Acid: (23-25%: o-o, 50- 52%: o-p and 25-30% p-p) � Sulphuric Acid : (25-26%: o-o, 45- 50%: o-p and 25-30% p-p)
Batch Calculations: Novolak � 100 gm batch of Novolak: Phenol + Formaline---- � 100 gm Novolak Resin +n Water 1 n ( Mole wt of Phenol) + 0.8 n ( Mol wt of HCHO)= 100 gm+ 18xn gms 94n + 0.8n x 30 = 100+18n 94n + 24n =100 100n = 100 n = 1 Quantity of 100% pure Phenol= 94 x1.18gms Quantity of 100% pure Phenol= 94 x1.18gms Assume 96% pure Phenol Actual weight of Phenol = 97.91 gms Quantity of 100% pure formaldehyde= 24 gms Assume 35% solution of Formaldehyde Actual weight of Formaldehyde = 68.57 Catalyst ( Oxylic Acid) 1.5% mole on Phenol = 0.944 gms Actual weight of Oxalic Acid = H00C-COOH.2H 2 O ( Mole wt 126 , Eq Wt. 63)
Resol � 100 gm batch of Resol: Phenol + Formaline---- � 100 gm Resol Resin + 1n Water 1 n ( Mole wt of Phenol) + 1.5 n ( Mol wt of HCHO)= 100 gm+ 18n gms 94n + 1.5n x 30 = 100+18n 94n + 45n =100+18n 121n = 100 n = 0.826 n = 0.826 Quantity of 100% pure Phenol= 77.644 gms Assume 96% pure Phenol Actual weight of Phenol = 80.88 gms Quantity of 100% pure formaldehyde= 24.7 gms Assume 35% solution of Formaldehyde Actual weight of Formaldehyde = 70.8gm Catalyst ( NaOH) 1.5% mole on Phenol = 1.21 gms Actual weight of NaOH = ( Mole wt 40 , Eq. Wt. 40)
Steps in Resin Manufacture (Bettleheim and Nihlberg) � Warming up time; � Ripening, the time at condensation temperature before the time starts to precipitates; � Post ripening, the time is held at condensation temperature after resin separates from the aqueous phase; � End Point Check: Alcohol Solubility, Free Phenol Content, and � End Point Check: Alcohol Solubility, Free Phenol Content, and Gelation time � Distillation; � Concentration, the period the resin is held under vacuum and heated to advanced to the desired viscosity; � Cooling.
Chek Points � A. Free Formalin: Sample+ Acetone+25ml, 10% Hydroxylamine Hydrochloride + Bromophenol Blue V/s 0.1N NaOH (Yellow to Violet) % Free Formalin= ( B-S) X NX 3.003 ----------------------- W B. Free Phenol: B. Free Phenol: Sample ( distillate)+ 25 ml Brominating Solution+ 10 ml of 10% KI V/s 0.1N Sodium Thisulphate using Starch solution ( Blue to) Colorless % Free Phenol= ( B-S) x 0.001566x100xV -------------------------------- V
Different types of phenolic resins There are two types of phenolic resin - Novolac and Resol Where Novolac is two stage compound. And Resol is one stage compound.
Phenolic resin Modifications � Use of phenol derivatives like alkyl phenols. � Etherification of the methylol group or phenolic hydroxyl group. � Reaction with unsaturated compounds like reactions with rosins. � Physical modification such as mixing with vinyl resins or rubber. � Reaction with epoxide compounds or poly isocyanates. � Reaction with inorganic acids or inorganic compounds.
Different Modification of Phenolic Resin Epoxy Modification: The resulting products exhibit high strength, strong adhesion, excellent dielectric properties and improved oxidation resistance. CH 2 -Cl O-CH 2 -CH-CH2-0- O + OH CH 2 CH 2 CH 2 O O O CH CH CH CH 2 CH 2 CH 2 O O O CH 2 CH 2 n
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