Thermokinetic Study of Thermal Degradation of Resin
Derived from
1-Naphthol-4-sulphonic acid
Jeevan Dontulwar1*, Manjiri Nagmote2,
Rajesh Singru3
1Principal,
Jawaharlal Nehru
Arts Commerce and Science College, Wadi, Nagpur, Maharashtra, India
2Department of Chemistry, Priyadarshini Institute of
Engineering and Technology,Nagpur, Maharashtra, India
3 Principal, Tai Gowalkar Science College, Ramtek,
Maharashtra, India
*Corresponding Author E-mail: jdontulwar@yahoo.co.in
The novel terpolymer (1-N-4-SAPPDF-Resin-I) has been
synthesized by polycondensation of 1-Naphthol-4- sulphonic acid and p-Phenylene
diamine with Formaldehyde in an acidic medium with molar proportion of
reactants (1:1:2). To reveal the structure of the resin, the resin was
characterized by elemental analysis and a spectral method, i.e. composition of
terpolymer has been determined on the basis of its elemental analysis. The
terpolymer resin has been characterized by FT-IR, NMR (1H and13C)
spectra and by SEM. For thermal decomposition studies, 1-N-4-SAPPDF-Resin-I
terpolymer has been studied by Thermo Gravimetric Analysis (TGA) at heating
rate 10°C min-1 in nitrogen atmosphere. Detailed thermal degradation
studies of the 1-N-4-SAHPPF Resin-I terpolymer has been carried out to
ascertain its thermal stability. Thermal degradation plot has been discussed in
order to determine their mode of decomposition, order of reaction(n), thermal
activation energy(Ea), frequency factor(Z), free energy change(ΔF),
entropy change(ΔS). Freeman – Carroll and Sharp- Wentworth methods have
been applied for the calculation of kinetic parameters while the data from the
Freeman – Carroll method has been used to determine various thermodynamic
parameters. Thermal activation energy (Ea) values determined by these two
methods were in good agreement with each other.
KEYWORDS: Polycondensation, Resins, Semiconductor, Synthesis, Thermogravimetric
analysis.
INTRODUCTION:
Thermogravimetric analysis of urea formaldehyde
polycondensate (UFPS) has been reported by Zeman and Tokarova.6
Terpolymer resins having good thermal stability have enhanced the scope for
development of some polymeric materials. The study of the thermal degradation
of terpolymer resins have recently become a subject of interest. Zhao Hong et
al. studied the thermal decomposition behaviour of phosphorous containing
copolystar.7 In an earlier communication8-11 from this
department numbers of studies on such terpolymers have been reported. However
no work seems to have been carried out on thermo analytical and kinetic studies
of the terpolymer resins from 1-Naphthol-4- sulphonic acid and Hexamethylene
diamine with formaldehyde. The present paper explores the thermal analysis
giving their relative thermal stabilities by applying the Sharp-Wentworth and
Freeman-Carroll methods. Energy of activation (Ea), Kinetic parameter viz.
Z, DS, DF, S*, and order of reaction (n) were determined by applying
Freeman-Carroll Method.
EXPERIMENTS AND EXPERIMENTAL TECHNIQUES:
Materials
The chemicals used in the synthesis of new terpolymer 1-N-4-SAPPDF-Resin-I
were procured from the market and were Sigma-Aldrich or chemically pure grade.
Whenever required they were further purified by standard procedure.
Synthesis of 1-N-4-SAPPDF-Resin-I terpolymer
The new terpolymer 1-N-4-SAPPDF-Resin-I was
synthesized by condensing 1-Naphthol-4-sulphonic acid (0.1 mol) and p-Phenylene
Diamine (0.1 mol) with 37% formaldehyde (0.2 mol) in a mol ratio of 1:1:2 in
the presence of 200 ml 2M HCl as a catalyst at 140°C ± 20°C for 6h in an oil
bath with occasional shaking to ensure thorough mixing. The separated
terpolymer was washed with hot water and methanol to remove unreacted starting
materials and acid monomers. The properly washed resin was dried, powdered and
then extracted with diethyl ether and then with petroleum ether to remove
1-Naphthol-4-sulphonic acid formaldehyde copolymer which might be present along
with 1-N-4-SAPPDF-Resin-I terpolymer. The reddish brown coloured powdery
product was immediately removed from the flask as soon as reaction period was
over and then purified. The reaction and suggested structure of 1-N-4-
SAPPDF-Resin-I in shown in Fig. 1.
The terpolymer was purified by dissolving in 10%
aqueous sodium hydroxide solution, filtered and reprecipitated by gradual drop
wise addition of ice cold 1:1 (v/v) concentrated hydrochloric acid / distilled
water with constant and rapid stirring to avoid lump formation. The process of
reprecipitation was repeated twice. The terpolymer sample 1- N-4-SAPPDF-Resin-I
thus obtained was filtered, washed several times with hot water, dried in air,
powdered and kept in vacuum desiccators over silica gel. The yield of the
terpolymer resin was found to be 81.9%.
Figure1: Proposed reaction for 1-N-4-SAPPDF-I
Characterization:
1-N-4-SAPPDF-Resin-I terpolymer resin was subjected to
microanalysis for C, H, S and N at STIC, Cochin. The number average molecular
weight (Mn) was determined by conductometric titration in non aqueous medium
such as dimethylsulphoxide (DMSO) using ethanolic KOH as a titrant. From the
graph of specific conductance against milliequivalents of base, first and last
break were noted from which degree of polymerization (DP) and the number
average molecular weight (Mn) has been calculated for terpolymer resin under
investigation. An infra-red spectrum of 1-N-4-SAPPDF-Resin-I was recorded on
Perkin-Elmer-R-XR Spectrophotometer in KBr pallets in the wave number region of
4000-400 cm-1 at Sophisticated Analytical Instrumentation Facility
(SAIF), Punjab University; Chandigarh. Both 1H and13C NMR
spectrum of newly synthesized terpolymer resin has been scanned on Bruker
Avance II 400 MHz NMR spectrometer using DMSO-d6 at Sophisticated Analytical
Instrumentation Facility, Punjab University, Chandigarh. SEM has been scanned
by FEI-Philips XL-30 electron microscope at STIC, Cochin.
THERMOGRAVIMETRIC ANALYSIS
The non-isothermal thermogravimetric analysis was
performed in air atmosphere with heating rate of 10 °C .min-1 from
temperature range of 50 °C to 1000 °C using Perkin Elmer Diamond 3 II
thermogravimetric analyzer inNitrogen environment. The thermograms were
recorded at VNIT, Nagpur. The thermal stability of copolymer, basedon the
initial decomposition temperature, has also been used here to define their
relative thermal stability, neglectingthe degree of decomposition. A plot of
percentage mass loss versus temperature i.e. thermogram is shown in the Fig.6
for a representative 1-N-4-SAPPDF-Resin-I. From the TG curves, the
thermoanalytical data and the decomposition temperatures were determined for
different stages. To obtain the relative thermal stability of the terpolymer,
the method described by Sharp-Wentworth and Freeman- Carroll were implemented.
RESULT AND DISCUSSION:
Newly synthesized, purified 1-N-4-SAPPDF-Resin-I was
found to be amorphous and reddish brown in colour. The terpolymers are soluble
in solvents such as DMF, DMSO, THF and aq. NaOH while insoluble in almost all
other organic solvents. The resin synthesized did not show sharp melting point
but undergo decomposition above 240°C. These resins were analysed for carbon,
hydrogen, nitrogen and sulphur content. The Mn of the terpolymer resin was
determined by non-aqueous conductometric titration in DMSO against KOH in 50%
(v/v) DMSO-Alcohol mixture using 100mg of resin sample. A plot of specific
conductance against the milliequivalents of potassium hydroxide required for
neutralization of 100 g of terpolymer was made. Inspection of such a plot
revealed that there are many breaks in plot. From this plot the first break and
the last break were noted. The calculation of (Mn) by this method is based on
the following considerations. (1) The first break corresponds to neutralization
of the more acidic phenolic hydroxyl group of all the repeating units and (2)
the break in the plot beyond which a continuous increase in conductance is
observed represents the stage at which phenolic hydroxyl group of all repeating
units are neutralized.
On the basis of the average, degree of polymerization
(Dp) is given by the following relation.
Total milliequivalent of base
required for complete neutralization
Dp
=
-------------------------------------------------------------------------------
Milliequivalent of base required for smallest
interval neutralization
Mn =
Dp X Weight of repeat unit (Monomer)
Repeat unit weight was determined by elemental
analysis. On the basis of degree of polymerization (DP), the average number
molecular weight (Mn) is calculated by multiplying the (DP) by the formula
weight of repeating unit. 12 The details of Elemental analysis,
molecular weight determination are incorporated in Table 1.
Table 1: Elemental analysis and molecular weight
determination of 1-N-4-SAPPDF-Resin-I
|
Empirical formula
of repeat unit
|
Carbon%
|
Hydrogen %
|
Nitrogen%
|
Sulphur%
|
Empirical weight
of repeat unit, g
|
Average
degree of
polymerization
(DP)
|
Average
molecular
weight
(Mn)
|
|
C18H16O4N2S1
|
60.67 Cal)
|
4.49 (Cal)
|
7.67 (Cal)
|
8.98 (Cal)
|
356
|
11.5
|
4094
|
|
60.97 (F)
|
4.36 (F)
|
7.85 (F)
|
9.1 (F)
|
Infrared spectra
IR-spectra of
1-N-4-SAPPDF-I terpolymer resins have been represented in Figure 2 which
reveals that all these terpolymers give rise to nearly same pattern of spectra
having similar peaks at expected values. Important IR peaks for observed values
with their assignments are reported in Table 3.16.
A broad
absorption band appeared in the region 3430-3440cm-1 may be assigned
to the stretching vibrations of phenolic hydroxyl (-OH) groups exhibiting
intramolecular hydrogen bonding. In line with this, The peak at 3400-3407 cm-1
bridging the monomers in terpolymer chain which was not found in IR spectra of
reactant monomers.11-13 The bands appeared at 3086-3097 cm-1
(Aryl C-H stretching), 1540-1542 cm-1 (C=C stretching), 2990-3000 cm-1
(=C-H stretching) and band at 1287-1290 (Aromatic C-O stretching) may be
strongly attributing to aromatic ring. The medium and sharp band appeared at
1344-1347 cm-1 exclusively indicates the presence of -SO3H
group, whereas band at 1183-1185 cm-1 (S=O asymmetric Stretching),
band at 1042-1043 cm-1(S=O symmetric Stretching) and medium band at
720 cm-1 (C-S stretching) also support to presence of -SO3H
on aromatic ring. The band at 856-857 cm-1 indicates the presence of
tetra substituted aromatic ring. 1,2,4,7 substitution on aromatic ring was
confirmed by the bands appeared at 952-956 cm-1, 1028-1030 cm-1,
1140-1142 cm-1. Results obtained in these studies are in well
agreement with those reported in literature. 14
Figure 2 : Infra-red spectra of 1-N-4-SAPPDF
Resin- I
1H Nuclear magnetic resonance spectra
The 1H NMR spectrum of 1-N-4-SAPPDF- I
terpolymers is scanned in DMSO-d6 and has been shown in Figure 3.
The 1-N-4-SAPPDF-Resin-I terpolymer resin shows multiplate signals at δ
7.8 ppm which may be attributed to proton of Aromatic-CH. The signals in the
range at δ 8.0 ppm may be due to phenolic hydroxyl protons. The much
downfield chemical shift for phenolic –OH indicates clearly the intramolecular
hydrogen bonding of -OH group.15, 16 We get doublet signal for -OH
and -SO3H groups in 1-N-4-SAPPDF terpolymer resins. It may be due to
the intramolecular hydrogen bonding, intermediate proton exchange reaction or
Ar-OH polymeric association. Proton exchange occurs rapidly in compounds in
which hydrogen is attached with N, O or S as there is no coupling is observed
between protons of the functional groups such as amines, sulphonic etc. with
the protons of the adjacent carbon atom. But intramolecular hydrogen bonding is
due to causing the attraction between protons of any group with electronegative
atom in same molecule. In 1-N-4-SAPPDF terpolymer the -OH and -SO3H
groups are responsible for intramolecular hydrogen bonding. Due to
intramolecular hydrogen bonding the signal of -OH and SO3H group
splits into doublets even though they are not coupled with neighbouring proton,
1-N-4-SAPPDF terpolymer therefore shows doublet at the region of 8.0 – 8.4
() ppm, the signal may be due to -SO3H group, which show
intramolecular hydrogen bonding with other neighbouring protons.17
The multiplates at δ 1.3 ppm, 1.4ppm and 2.5ppm may be due to -CH2-CH2-CH2-
moiety of diamine whereas multiplate at 2.0ppm may be attributed to –NH-
moiety.
Figure 3: 1H-NMR spectra of 1-N-4-SAPPDF-I
13C-Nuclear Magnetic
Resonance Spectra
Spectra of
1-N-4-SAPPDF- I terpolymers is shown in Figure 4. 13C NMR spectra
display signals arising from all the carbon atoms and hence provide direct
information about the carbon skeleton of the terpolymer. To economize the
space, only one 13C-NMR spectral data of a 1-N-4-SAPPDF-I terpolymer
is discussed in this section.
The 13C NMR spectrum of 1-N-4-SAPPDF-Resins
shows the corresponding peaks at 155.1, 107.8, 126.1, 133.8, 130.2, 126.6,
127.4, 126.32, 122.45, 126.21 ppm with respect to C 1 to C10 of
the aromatic naphthalene ring. Actually naphthalene ring shows peaks within the
range of 120 to 125ppm, but the shifting of signals is due to the substitution
in naphthalene ring. More
electronegative group is bonded to Carbon atom, deshielding
shifts increases.18 Thus, the peak of C1 near 155.56 ppm
may be because of deshielding effect by –OH grp and peak of C4 near
134.0 ppm may be obtained on naphthalene ring because of deshielding effect by
– SO3H grp. The signal at 114.3ppm may be assigned to Carbon of
Ar-NH of p-Phenylene diamine moiety. One more peak is obtained for p-Phenylene
diamine, which may be because of -CH- of Phenylene ring.
This is strongly supporting the proposed structure of
polymers. The 13C NMR spectrum after analysis minutely confirmed
that the monomers are arranged in a straight manner, giving the linear
structure for terpolymer, which we have proposed is obliviously correct given
in Figure 1.
Figure 4: 13C-NMR spectra of 1-N-4-SAPPDF terpolymers
Thermogravimetric Analysis
In order to explore the thermal degradation study of
1-N-4-SAPPDF-Resin-I, the thermogram has been studied minutely. Decomposition
pattern of 1-N-4-SAPPDF-Resin-I is shown in Figure 5.The data of
thermogravimetric analysis reveals the decomposition between 40 to 100ºC
corresponds to 5.14% loss which may be attributed to loss of water molecule
against calculated 4.81% present per repeat unit of the polymer. This initial
weight loss may be due to the loss of water of crystallization associated with
terpolymer resin.19, 20 After loss of water molecule thermograph of
1-N-4-SAPPDF-I has depicted three stages decomposition. The first decomposition
step start with gradual decrease in mass loss due to degradation of phenolic
hydroxyl group and sulphonic group substituted to naphthalene ring, in the
temperature range of 150-450ºC, corresponded the weight loss of 31.42% found
and 31.01% calculated. The weight loss by increasing temperature may be due to
activating the macromolecules which may develop the cross linking in the
molecules. Cross linking developed the strain in the macromolecule with result
of weight loss to acquire the stability. The second stage of decomposition of
1-N-4-SAPPDF-I has been started by increasing temperature from 450 – 700ºC, when
observed a rapid mass loss corresponding to 65.72% found and 64.17% calculated
weight loss, which may be due to the loss of naphthalene ring due to unzipping
of cross linking, high strain, unstability and depolymerization occurred in the
resin. In the third stage, the temperature has been increased from 730-980ºC
which might increasing the strain in the molecule, cross linking increased,
unstability increased, leading to weight loss of about 98.79% found and 100%
calculated and the rigid prepolymeric part after the third stage is left as the
char residue which is negligible in 1-N-4- SAPPDF-I terpolymer decomposition .
Figure 5: Decomposition pattern of 1-N-4-
SAPPDF -I terpolymer
In the present investigation Sharp-Wentworth and
Freeman-Carroll methods have been used to determine the kinetic parameters of
1-N-4-SAPPDF-Resin-I terpolymer sample.
Sharp-Wentworth method: In this method following expression is used.
Log [dc / dt /Δ (1-c)] = log (A/β) – Ea /
2.303 R – 1/T
Where, β is the linear heating rate. The graph of
Log [dc / dt /Δ (1-c)] versus 1/T has been plotted. The graph is a
straight line with Ea as slope and A as intercept. The linear relationship
confirms that the assumed order (n) = 1 is correct.
Freeman-Carroll method: In this method following expression is used.
Δ log (dw/dt)/ Δ log Wr = (- Ea/2.303R) –
Δ (1/T)/Δ log Wr + n
where dw/dt = rate of change of weight of terpolymer
sample with respect to time Wr = Wc-W, where Wc is the weight loss at the
completion of the terpolymer reaction or at definite time and W is the total
weight loss up to time t. T is the temperature, R is the gas constant and n is
the order of reaction. Hence the graph of Δ log (dw/dt)/ Δ log Wr
versus Δ(1/T)/Δ log Wr Should give on Y axis (x=0) an intercept for
the value of n, the order of reaction and the slope m = -Ea/2.303R. A plot of
percentage mass loss versus temperature is shown in Fig. 5
for1-N-4-SAHDF-Resin-I terpolymer. From the TG curve, the thermoanalytical and
the decomposition temperature were determined (Table 2) to obtain the thermal
stability of the polymer. The method described by Sharp –Wentworth was adopted.
Based on the initial decomposition temperature, the thermal stability of the
terpolymer has been used here to define its thermal stability, neglecting the
degree of decomposition (Table 2).9
Table 2: Results of Thermogravimetric Analysis of
1-N-4-SAPPDF- I Terpolymer Resins
|
Terpolymer
resins
|
Half
Decomposition Temp. K
|
Activation Energy
Ea (KJ)/mol
|
Entropy change
ΔS
(J)
|
Free energy
ΔF
(KJ)
|
Frequency
factor
(Z)
(Sec.-1)
|
Apparent entropy
(S*)
(KJ)
|
Order of reaction
(n)
|
|
FC
|
SW
|
|
1-N-4-SAPPDF-I
|
843
|
18.21
|
19.34
|
-193.03
|
292.87
|
689
|
-20.41
|
0.98
|
FC – Freeman–Carroll Method; SW – Sharp-Wentworth
Method
|
|
|
|
Figure 5: Thermal activation energy plot
byFreeman-Carroll method of 1-N-4-SAPPDF-I
|
Figure 6: Freeman-Carroll plot of 1-N-4-SAPPDF-I
terpolymer
|
|
|
|
Figure 7: Sharp-Wentworth plot of 1-N-4-SAPPDF
-I terpolymer
|
Using thermal decomposition data and then applying the
Sharp-Wentworth method, activation energy is calculated which is in agreement
with the activation energy calculated by Freeman-Carroll method.10
Thermal activation energy plot of Sharp-Wentworth method (Fig. 7) and
Freeman-Carroll method (Fig. 5) for the polymer have been shown. Thermodynamic
parameters such as entropy change (ΔS), free energy change (ΔF),
frequency factor (Z) and Apparent entropy (S*) calculated on the basis of
thermal activation energy are given in Table 2. From the abnormally low values
of frequency factor, it may be concluded that the decomposition reaction of
1-N-4-SAPPDF terpolymers can be classed as a ‘slow’ reaction. There is no other
obvious reason.11 Fairly good straight line plots are obtained using
the two methods. This is expected since the decomposition of terpolymer is
known not to obey first order kinetics perfectly. 11
CONCLUSION:
1. A terpolymer 1-N-4-SAPPDF-I, based on the
condensation reaction of 1Naphthol-4-sulphonic acid-p- phenylene
diamine-formaldehyde in the presence of acid catalyst, was prepared.
2. As the degradation of the terpolymer under
investigation started at high temperature which indicates that the terpolymer
1-N-4-SAPPDF-I is thermally stable at elevated temperature.
3. Low value of frequency factor may be concluded that
the decomposition reaction of 1-Naphthol-4-sulphonic acid- p- Phenylene
diamine-formaldehyde terpolymer can be classified as ‘slow reaction’.
REFERENCES:
1.
M. A. Riswan Ahmad, R.
S. Azarudeen, M. Karunakaran, A. R. Barkanudeen, Iran Poly J., 2010, 9(8),
635-646.
2.
Freeman E S And Carroll
B, J. Physc. Chem., 1958, 62, 394.
3.
S. S. Rahangdale, W. B.
Gurnule, Arch. Appl. Sci. Res., 2010, 2(6), 53-68.
4.
R. N. Singru, Der Pharma
Chemica, 2011, 3(5), 128-134
5.
D. T. Masram, K. P.
Kariya, N. S. Bhave, Arch. Appl. Sci. Res., 2010, 2(2), 153-161.
6.
S. D. Bompilwara, S. B.
Kondawarb, V. A. Tabhanec, R. SnehalKargirward, Advances In Applied Science
Research, 2010, 1 (1), 166-173
7.
B. Shah, A. Shah, N.
Patel, Iran. Polym. J., 2008, 17, 17
8.
N. K. Prajapati, Jignesh
A. Patel, Janki Vyas, Asha D. Patel And G. R. Patel, Der ChemicaSinica, 2011, 2
(2), 125-129
9.
S. C. Das, J. Ind. Chem.
Soc., 2000, 77, 69
10. W. B. Gurnule, P. K. Rahandale, L. J.
Paliwal, R. B. Kharat, J. Appl. Polym. Sci., 2003, 89(3), 886
11. M. M. Patel, M. A. Kapadia, D. P. Patel, J.
D. Joshi, React. Funct. Polym., 2007, 67, 757.
12. W. Kemp, Organic Spectroscopy, The Macmillan
Press: Hong Kong, (1975).
13. S. S. Butoliya, W. B. Gurnule A. B. Zade,
E-Journal of Chemistry, (2010) 7(3),
1101-1107.
14. Nagmote M, Dontulwar J, Singru R., Discovery
Chemistry, 2015, 1(1), 37-45
15. Camhan, James Claude, Gundlach, Paul Edward,
“Methods and apparatus for rapid determination of polymer molecular weight”,
U.S. Patent 6868715 (2005).
16. Cervantes J. M., Cauich T. V., Rodriguez,
Vazquez-Torres H., Lica – Calveric A., Polym. Degrad. Stab. 91(2), 3312-3321
(2006).
17. Jeevan Dontulwar, ManjiriNagmote, Rajesh
Singru, Journal of Chemical and Pharmaceutical Research, 2016, 8(5):713-720
17. Silverstein RM,Webster FX, Spectrometric
Identification of Organic Compounds, 6th Edition, Willy: New York, 1998
18. M. M. Jadhao, L. J. Paliwal, N. S. Bhave,
Ind J. Chem, (2005) 44-A, 1110.
19. M. M. Jadhao, L. J. Paliwal, N. S. Bhave, J.
ApplPolym Sci, (2005) 96, 1605.