See discussions, st ats, and author pr ofiles f or this public ation at : https:www .researchgate.ne tpublic ation270647887 [628001]

See discussions, st ats, and author pr ofiles f or this public ation at : https://www .researchgate.ne t/public ation/270647887
Thermal degradation study of PVA derivative with pendant
phenylthionecarbamate grou ps by DSC/TGA and GC/MS
Article    in  Polymer De gradation and St ability · Januar y 2015
DOI: 10.1016/ j.polymde gradst ab.2014.12.027
CITATIONS
12READS
410
8 author s, including:
Some o f the author s of this public ation ar e also w orking on these r elat ed pr ojects:
Tiour eas furánic as View pr oject
Evaluación del ef ecto genot óxico de c ontaminant es ambient ales View pr oject
Iraís Góme z Lópe z
4 PUBLICA TIONS    16 CITATIONS    
SEE PROFILE
Elena M Ot azo-Sánche z
Hidalg o St ate Autonomous Univ ersity
107 PUBLICA TIONS    522 CITATIONS    
SEE PROFILE
Jenar o Leocadio V arela Caselis
Benemérit a Univ ersidad A utónoma de Puebla
18 PUBLICA TIONS    56 CITATIONS    
SEE PROFILE
Albert o José Gor dillo Martíne z
Autonomous Univ ersity of Hidalg o
80 PUBLICA TIONS    260 CITATIONS    
SEE PROFILE
All c ontent f ollo wing this p age was uplo aded b y Iraís Góme z Lópe z on 23 Januar y 2019.
The user has r equest ed enhanc ement of the do wnlo aded file.

Thermal degradation study of PVA derivative with pendant
phenylthionecarbamate groups by DSC/TGA and GC/MS
I. G/C19omeza, E.M. Otazoa,*, H. Hern /C19andezc, E. Rubiod, J. Varelad, M. Ramírezb, I. Barajasa,
A.J. Gordilloa
a/C19Area Acad /C19emica de Química (AAQ), Universidad Aut /C19onoma del Estado de Hidalgo, Ciudad Universitaria, Carretera Pachuca-Tulancingo Km 4.5,
Mineral de la Reforma, Hidalgo C.P.42184, Mexico
b/C19Area Acad /C19emica de Ciencias de la Tierra y Materiales (AACTyM), Universidad Aut /C19onoma del Estado de Hidalgo, Ciudad Universitaria,
Carretera Pachuca-Tulancingo Km 4.5, Mineral de la Reforma, Hidalgo C.P.42184, Mexico
cFacultad de Ingeniería Química, Benem /C19erita Universidad Aut /C19onoma de Puebla, 4 Sur 104, Centro Hist /C19orico, Puebla C.P. 72000, Mexico
dCentro Universitario de Vinculaci /C19on y Transferencia de Tecnología, Benem /C19erita Universidad Aut /C19onoma de Puebla, 4 Sur 104, Centro Hist /C19orico,
Puebla C.P. 72000, Mexico
article info
Article history:
Received 5 June 2014
Received in revised form
13 November 2014Accepted 23 December 2014Available online 3 January 2015
Keywords:
Poly(vinyl phenylthionecarbamate)DSC/TGAPyrolysisGC/MSabstract
The thermal study of poly(vinyl phenylthionecarbamate) was carried out through DSC and TGA analysis.
DSC curve affords five decomposition steps whose temperature ranges were consistent with the TGA
weight loss graphic. Tg transition takes place at 219/C14C. The largest PVA-PT mass loss occurs at 120
e340/C14C, within two overlapped process with an average DH¼170.4 J/g. These processes were assigned
to the vicinal hydroxyl groups' water elimination, followed by the polymer defunctionalization. The PVA
derivative thermal decomposition mechanism was proposed based on GC/MS results.
©2015 Elsevier Ltd. All rights reserved.
1. Introduction
Thermal degradation of functionalized polymers has been
studied in order to control the accessibility of polymers in solid and
liquid states, increase the fire retardation properties, for to secure
the performance of the material over long periods of time under
changeable environmental conditions and increase the commercial
value of these materials [1e4].
Functionalized sulphur polymers have been studied and design
for metal polluted water remediation [5e9]. SH containing resins
show highly selective adsorption towards heavy metals, but the
interaction with heavy metal cations is not reversible or de-
composes the material [8]. The CS sulphur atom as in thioureas,
thioamides and thionecarbamates is likely to be a better ligand
than SH, concerning reversibility and oxidability [10].
We have reported a new derivative of polyvinyl alcohol (PVA)
polymer material contain the C ]S function: poly(vinylphenylthionecarbamate), PVA-PT. This material proved to be a good
absorber of Mn2țin water [11]. Microwave action improved the
reaction conditions between PVA and phenylisothiocyanate (PITC)
[12],a22factorial design was performed and the polynomials
explained the in fluence of temperature and time on the % yields of
PVA-PT and diphenylthiourea (DPT) and % functionalization.
In this work, the thermal study of PVA-PT is carried out. DSC and
TGA analyses identi fied the degradation steps and pyrolysis with
GC/MS allowed the identi fication of the processes present in each
one. Based on results, the decomposition reactions are proposed to
provide a widespread PVA-PT characterization.
2. Experimental section
Microwave-assisted method [12] was selected on the basis of
safety and as reproducible PVA-PT preparation. Fig. 1 shows the
procedure. The functionalization of PVA in these conditions is 60%.
The polymer was crushed and sieving separating the product
with 850 microns particle size. Samples of 14.2 and 500 mg were
then used for DCS/TGA and pyrolysis analyses respectively. TGA and
DSC curves were achieved in an STA 449 F3 Jupiter- TG-DSC*Corresponding author. Tel.: ț52 7717172000×2208; fax: ț52 7717172000×6502.
E-mail address: elenamariaotazo@gmail.com (E.M. Otazo).
Contents lists available at ScienceDirect
Polymer Degradation and Stability
journal homepage: www.elsevier.com/locate/polydegstab
http://dx.doi.org/10.1016/j.polymdegradstab.2014.12.027
0141-3910/ ©2015 Elsevier Ltd. All rights reserved.Polymer Degradation and Stability 112 (2015) 132 e136

simultaneous thermal analyzer, under nitrogen atmosphere in the
range of 27 e800 C at 10/C14C min/C01heating rate.
Moreover, a pyrolysis was carried out in a 10 cm deep Schlenk
flask. Before heating, it was purged three times with pure He
(99.99%). Pyrolysis was carried out under helium and the flask was
heated at 100, 180 and 250/C14C. Each temperature pyrolysis was
maintained during 5 min. After each process, a gas sample was
taken with a syringe and the vacuum opened before pass to the
next higher temperature. The gas sample was injected into a
Hewlett Packard 5890 Series II gas chromatograph coupled to a
Hewlett Packard 5989A mass spectrometer (GC/MS). Mass spectra
were achieved with 70 eV electron impact energy. The chro-
matograms and mass spectra were recorded. The Schlenk flask
final residue was extracted with CHCl 3a n da l s oa n a l y z e dw i t hG C /
MS. The sequenced temperature pyrolysis experiments were run
twice.
3. Results and discussion
3.1. Thermal analysis
Fig. 2 illustrates the TGA and DSC plots. According to them, PVA-
PT shows six steps: loss of humidity (I), one phase transition (II) and
four degradation processes (III eVI). They are described in Table 1 .
The initial endothermic first stage occurs in the range 27 e130/C14C,
with a weight loss of 1.32%, attributed to water evaporation. The
same observable fact was reported for the thermal analysis of PVA
[13], whose water content ranges between 3 and 5%. The lower
PVA-PT water content might be due to the consuming functional-
izing treatment, that involves collateral DPT formation reaction
[12].
The endothermic small peak at 219/C14C is assigned to the glass
transition temperature (Tg), as the PVA-PT does not melt andcalculated DCp¼0.273 Jg/C01K/C01. The high Tg value is probably due
to the presence of functional groups with a phenyl group.
The third and fourth stages lie between 120 and 340/C14C which
correspond to the pyrolytic endothermic PVA-PT degradation re-
actions. Both together are the steepest drop in the TGA curve
(Fig. 3 ). The processes' initial and final temperatures were best
defined by the TGA first derivative curve. Fig. 3 also shows a total
weight loss of 62.57%. The third can be attributed to the dehydra-
tion of vicinal hydroxyl groups with elimination of H 2O, as was
reported for PVA [14] at a similar temperature, with an enthalpy of
31.82e38.17 kJ/mol [15]. The fourth stage can be assigned to
defunctionalization reactions that involve gas losses. Both pro-
cesses were not allowed to split and the total enthalpy was deter-
minated (170.4 J/g).
Thefifth and sixth processes are also overlapped and observed
between 335 and 600/C14C. These correspond to exothermic chain
decomposition reactions with a total weight loss of 26.63%. After
600/C14C, no longer decomposition is noticeable.
3.2. Pyrolysis mechanism
The PVA-PT pyrolytic processes were studied by GC/MS. The
gases evolved near 180/C14C heating produce the mass spectrum
showed in Fig. 4 . Main m/zpeaks are: 18, 28, 32 and 44; corre-
sponding to H 2Oț/C15,C H 2]CHț$
2or Nț$
2,Sț/C15or Oț$
2and C ]Sț/C15
respectively. The 250/C14C evolved gases produce the same peaks in
MS spectrum. This fact suggests a simultaneous decomposition of:
1) the eOH chain elimination with water formation, previously
reported for PVA pyrolysis [13], and 2) the eO(CS)-NH-Phenyl
functional group cleavage. The water elimination is in agreement
with the reported 60% functionalization of the former polymer [12].
The GC/MS residue is shown in Fig. 5 . Identi fied substances are:
at 8.09 min phenylisocyanate ( m/z119); 8.39 min, aniline ( m/z93);
12.46 min, phenylisothiocyanate ( m/z135) formed by the rupture of
thionocarbamate bonds and 14.26 min, quinolein ( m/zpeak 143).
The azacycloheptatretraene ( m/zpeak 91) is formed by loses of CO
and CS from phenylisocyanate and phenylisothiocyanate ( Fig. 5 a
and c).
The proposed whole pyrolytic processes are shown in Fig. 6 ,
with the GC/MS data support. The elimination of H 2O(m/z18) by a
dehydration of vicinal hydroxyl groups near 200/C14C was con firmed
(Path A), similar to PVA thermal decomposition [13]. This path gives
intermediate (I). Furthermore, (I) undergoes defunctionalization
Fig. 1. Synthesis of PVA-PT.
Fig. 2. TGA and DSC curves of the thermal degradation of PVA-PT.I. G/C19omez et al. / Polymer Degradation and Stability 112 (2015) 132 e136 133

and produces (II) and a polyene, due to phenylcarbamothioic S-acid
elimination (B) via a possible cyclic mechanism that involves the
C]O formation and S eH with the bchain hydrogen, as it was re-
ported in the literature [16] in thionecarbamates. Due to the
experimental ending temperature (250/C14C), the polyene degrada-
tion reactions [14] were not studied.
As a consequence of path B, the produced phenylcarbamothioic
S-acid (II) presents three cleavage possibilities: The route (a) yields
aniline ( m/z93) and carbon oxide sul fide (m/z60), shown in Fig. 5 b.
The mechanism involves a state in which the transfer of the SH
hydrogen atom and the cleavage of C-S might occur simultaneously.
The ruptures (b) and (c) provide molecular peaks m/z119 (PhNCO)
and m/z135 (PhNCS) respectively, shown in Fig. 5 a and c. The
elimination mechanism proceeds through a deprotonation, fol-
lowed by the formation of isocyanate or isothiocyanate. Possible
isomerization reactions giving phenylthiocyanates and phenyl-
cyanates respectively are not discarded [17,18] .Table 1
Thermal process from TGA curve of PVA-PT and interpretation of pyrolysis processes showed in Fig. 5 based on mass spectra interpretation.
DSC TGA Chrom mass
Process T (/C14C)
(onset-endset)T(/C14C)
(peak)DH (J/g) Interpretation T (/C14C) % Mass
lossIdenti fied substances
I2 7 e130 100** 21.89 Humidity 27 e130 1.32 H 2O (locked)
II 206 e224 219 * Tg ee e
IIIeIV 120 e340 261 170.40 Side eOH elimination
and defunctionalization reactions120e340 62.57 H 2O and Phenylisocyanate,
phenylthiocyanate, benzene, aniline
V 335 e419 377 11.76 C eC cleavage.
Chain rupture335e419 18.64 Charcoal, tars
VI 419 e600 509 130.60 Carbonization Tars. 419 e600 7.99 Charcoal, tars
*:DCp¼0.273 Jg/C01K/C01.
Fig. 3. TGA and TGA first derivative curve.
Fig. 4. Chromatogram and mass spectrum of the PVA-PT 180 and 250/C14C.I. G/C19omez et al. / Polymer Degradation and Stability 112 (2015) 132 e136 134

Furthermore, a new pyrolytic path was proposed in this paper.
The path (C) describes another defunctionalization process, that
might go through the COS elimination and formation of interme-
diate (III) by migration of aniline groups to the carbon chain. This
intermediate would be fast transformed to the more stable 2-
methyl quinoline (C 10H9N,m/z143) through Skraup-like cycliza-
tion. The MS spectrum of C 10H9N is shown in Fig. 5 d matches with
the reported spectrum [19]. Starting from C 10H9N, C 2H3and C 2H4
elimination gives C 8H6N(m/z116) and C 8H5N(m/z115), respec-
tively. Both undergo acetonitrile (C 2H3N) elimination to produce
C6H3(m/z75) and C 6H2(m/z74), which con firms the 2-methyl
substitution in quinoline.The PVA-PT DSC/TGA and pyrolysis analysis con firmed that the
thermal PVA-PT decomposition begins above 130/C14C after the loss
of the trapped water within the polymeric chains. The proposed
decomposition reactions are con firmed by MS.
4. Conclusions
The DSC and TGA analyses of PVA-PT show six steps at
120e340/C14C range. The third and four processes are overlapped
with an average DH¼170.4 J/g. These showed the larger weight
loss (62.57%) of the whole decomposition. These processes are
assigned to the elimination of H 2O from vicinal eOH groups (A) and
Fig. 5. Chromatogram and mass spectrum of the residue PVA-PT after the pyrolysis process at 250/C14C.I. G/C19omez et al. / Polymer Degradation and Stability 112 (2015) 132 e136 135

the defunctionalization reactions B and C. Mass spectra con firm the
thermal degradation proposed reactions.
Acknowledgements
IGL would like to thank CONACyT-Mexico, (The National Council
of Science and Technology) for the financial support awarded for
this research. The Authors also acknowledge and express their
appreciation to National Network PROMEP funding, provided to
Hidalgo State Autonomous University (project PROMEP/UAEH), as
well as contributions from the Public Education Secretary of Mexico
(SEP).References
[1]Cochez M, Ferriol M, Weber JV, Chaudron P, Oget N, Mieloszynski JL. Thermal
degradation of methyl methacrylate polymers functionalized by phosphorus-
containing molecules I. TGA/FT eIR experiments on polymers with the
monomeric formula CH 2C(CH 3)C(O)OCHRP(O)(OC 2H5)2(RH, (CH 2)4CH3,
C6H5Br, C 10H7). Polym Degrad Stab 2000;70:455 e62.
[2]Pitchaimari G, Vijayakumar CT. Functionalized N-(4-hydroxy phenyl) mal-
eimide monomers: kinetics of thermal polymerization and degradation using
model-free approach. J Appl Polym Sci 2014;131:39935 .
[3]Ten E, Vermerris W. Functionalized polymers from lignocellulosic biomass:
state of the art. Polymers 2013;5:600 e42.
[4]Guo Z, Pereira T, Choi O, Wang Y, Hahn HT. Surface functionalized alumina
nanoparticle filled polymeric nanocomposites with enhanced mechanical
properties. J Mater Chem 2006;16:2800 e8.
[5]Bilba D, Bilba N, Moroi G. Removal of mercury (II) ions from aqueous solutions
by the polyacrylamidoxime chelating fiber. Sep Sci Technol 2007;42:171 e84.
[6]Chen Y-Y, Gu Z-M, Ren X-M, Cheng X-L. Synthesis of a dithiocarbamate
chelate resin and its oxidized form and their adsorption properties for heavy
metal ions. J Macromol Sci Part A Chem 1987;24:319 e31.
[7]Chen Y, Zhao Y. Synthesis and characterization of polyacrylonitrile-2-amino-
2-thiazoline resin and its sorption behaviors for noble metal ions. React Funct
Polym 2003;55:89 e98.
[8]Ritter JA, Bibler JP. Removal of mercury from waste water: large-scale per-
formance of an ion exchange process. Water Sci Technol 1992;25:165 e72.
[9]Egawa H, Nonaka T. Studies of selective adsorption resin. XXIV. Preparation
and properties of macroreticular chelating resins containing both poly-
ethylenepolyamine side chains and mercapto groups. J Appl Polym Sci
1986;31:1677 e85.
[10] Kukushkin VY, Bokach NA. Reactivity of ligands. Russ J General Chem
2007;77:194 e205.
[11] Richards R, Otazo E, Prieto F, Gordillo A, Gonzalez C. Synthesis, thermal and
spectroscopic characterization of new PVA derivative for metal ion water
contaminants absorption: poly(vinylphenylthionecarbamate). In:
Sanderson R, editor. 10th Annual UNESCO/IUPAC Conference on macromol-ecules &materials. Mpumalanga, South Africa: UNESCO Associated Center for
Macromolecules &Materials University of Stellenbosch; 2008. p. 32 .
[12] G/C19omez I, Otazo EM, Prieto F, Guevara A, Villag /C19omez JR. Experimental design of
the microwave assisted synthesis of the poly(vinyl phenylthionecarbamate).
Tetrahedron Lett 2013;54:4285 e8.
[13] Barrera J, Rodríguez J, Perilla J, Algecira N. Estudio de la degradaci /C19on t /C19ermica
de poli(alcohol vinílico) mediante termogravimetría y termogravimetríadiferencial. Ing Investig 2007;27:100 e5.
[14] Gilman JW, VanderHart DL, Kashiwagi T. Thermal decomposition chemistry of
poly(vinyl alcohol). Symposium Series 599. In: Society AC, editor. Fire and
polymers II: materials and Tests for Hazard Prevention national Meeting,208th ACS Symposium series, vol. 599. Washington, DC: ACS; 1994.p. 161 e85.
[15] Shehap AM. Thermal and spectroscopic studies of polyvinyl alcohol/sodium
carboxy methyl cellulose blends. Egypt J Solids 2008;31:75 e91.
[16] Newman MS, Hetzel FW. Preparation of ole fins by pyrolysis of O-alkyldime-
thythiocarbamates. J Org Chem 1969;34:3604 e6.
[17] Silva D, Norberto F, Santos S, Herv /C19es P. Chemistry of aryl N-(2-pyridyl) thio-
nocarbamates in basic media. J Phys Org Chem 2009;22:221 e8.
[18] Hennicke H. Ueber die Einwirkung von Senf €olen auf Aminocrotons €aureester.
Justus Liebigs Ann Chem 1906;344:19 e29.
[19] Horai H, Arita M, Kanaya S, Nihei Y, Ikeda T, Suwa K, et al. MassBank: a public
repository for sharing mass spectral data for life sciences. J Mass Spectrom
2010;45:703 e14.
Fig. 6. PVA-PT-pathways decomposition by pyrolysis.I. G/C19omez et al. / Polymer Degradation and Stability 112 (2015) 132 e136 136
View publication statsView publication stats