Melt grafting of metal salts onto LLDPE backbone - An FTIR study

Article abstract of DOI:10.1016/j.saa.2010.02.042

The melt graft functionalization of metal di(meth)acrylates onto linear low density poly(ethylene) (LLDPE) at 160 °C under inert atmosphere is reported here. The post melt grafting FTIR-RI method was used to find out the % grafting of metal salts onto LLDPE backbone. Further, DSC, TGA and HRTEM techniques were introduced to explain the results. A plausible reaction mechanism was proposed.

Full text of DOI:10.1016/j.saa.2010.02.042

Spectrochimica Acta Part A 76 (2010) 37–44
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Melt grafting of metal salts onto LLDPE backbone – An FTIR study
R. Anbarasana,∗, V. Dhanalakshmib
a Department of Mechanical Engineering, MEMS Thermal Control Lab, National Taiwan University, Taipei – 10617, Taiwan, ROC
b Department of Polymer Technology, KCET, Virudhunagar 626 001, Tamil Nadu, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The melt graft functionalization of metal di(meth)acrylates onto linear low density poly(ethylene)
(LLDPE) at 160 ◦C under inert atmosphere is reported here. The post melt grafting FTIR–RI method
was used to find out the % grafting of metal salts onto LLDPE backbone. Further, DSC, TGA and HRTEM
techniques were introduced to explain the results. A plausible reaction mechanism was proposed.
© 2010 Elsevier B.V. All rights reserved.
Received 16 November 2009
Received in revised form 12 February 2010
Accepted 26 February 2010
Keywords:
Melt grafting
Polyethylene
Metal esters
FTIR–RI kinetics
DSC
TGA
HRTEM
1. Introduction
et al. [7] with the basic kinetic reports. By thorough literature
survey, we could not find any report based on the melt graft-
Polyolefins particularly, polyethylenes, found applications in
various science and engineering fields. The widely usable fields are
packaging and automobile sectors. After their better utilizations,
simply they are thrown into open environment and resulted with
environmental pollution. The environmental pollution of poly-
olefins is due to the absence of hydrolysable or polar groups in its
backbone. Polyolefins are functionalized by various methods with
different functional groups. In the present investigation, we are
very much interested in the functionalization of LLDPE by thermol-
ysis method, an environmental green method, with different metal
acrylates and metal methacrylates. The following is the reason for
selecting the metal ester as a functional candidate. (1) Having two
easily hydrolysable ester groups. (2) During the bio-degradation
process there will be a chain scission process in two different places
of LLDPE backbone. Recently, Walker et al. [1] reported about the
synthesis and characterizations of acrylates of La, Sr and Mn. Cd
acrylate core report is also available in the literature [2]. LLDPE
backbone was melt grafted with tetrahydrophthalic anhydride [3],
non ionic surfactants [4], maleic anhydride [5] and diethylmalonate
[6] and their structure–property relationships were closely ana-
lyzed. Radiation induced graft polymerization of Mn, Cr, Co, Ni
and Cu acrylate monomer onto PE was reported by Savostyanov
ing of Ba, Mg and Mn di(meth) acrylates onto LLDPE backbone.
In the present investigation, we took this job as a challenge and
successfully grafted the same onto LLDPE backbone for the first
time.
The amount of ester group chemically grafted onto the LLDPE
surface can be determined by chemical as well as spectroscopy
methods. The chemical method leads to the environmental pol-
lution problem because of utilization of larger quantities of toxic
and hazardous solvents. Due to these reasons we are not inter-
ested in chemical estimation method. The amount of ester group
grafted onto the LLDPE backbone can be determined by the spec-
troscopy method but this method is an eco-friendly one. Hence,
we preferred this spectroscopy method, particularly with the FTIR
spectroscopy method. Moreover, this method is an economically
cheaper than the chemical method with more accuracy. FTIR spec-
trometer is a useful tool in various science and engineering fields,
because of its high sensitivity or detectivity towards traces amount
of sample, low noise to signal ratio and this method is an easy
and inexpensive one. FTIR spectroscopy is used for both qualitative
[8–12] and quantitative [13–25] analysis. By thorough literature
survey, we could not find any report based on the FTIR kinetics
of melt functionalization of Ba, Mg and Mn diesters onto LLDPE
backbone. In the present investigation, for the first time, we are
reporting about the melt functionalization of the above-mentioned
metal esters with LLDPE and further characterized by FTIR–RI
kinetics.
∗
Corresponding author. Tel.: +886 2 3366 4945; fax: +886 2 2363 1755.
E-mail address: anbu may3@yahoo.co.in (R. Anbarasan).
1386-1425/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2010.02.042

38
R. Anbarasan, V. Dhanalakshmi / Spectrochimica Acta Part A 76 (2010) 37–44
2. Materials
2.1. Methods
After degassing, the temperature of the reactor was kept at 160 ◦C
for 2.5 h without stirring. After the melt functionalization reac-
tion was completed, the reactor was removed from the oil bath,
cooled to room temperature and the functionalized LLDPE sam-
ples were collected and cut into small pieces. These were put in
toluene at 140 ◦C for 30 min for the isolation purpose. The func-
tionalized, non-cross linked samples were dissolved in toluene
while the functionalized cross-linked samples did not dissolve in
toluene. The dissolved samples were re-precipitated by adding
600 mL of acetone and the cross-linked samples were isolated. The
non-cross linked sample was collected and dried under vacuum at
60 ◦C. After drying, the sample was weighed and stored in a zip-
per bag. FTIR spectrum was obtained and quantitative calculations
have done with the non-cross linked, functionalized polymers.
The same grafting procedure was followed for other metal esters
too.
Carbonates of Ba, Mg and Mn were purchased from SD Fine
Chemicals, AR grade, India. Acrylic acid and methacrylic acid (CDH
Chemicals, India) were purchased and used after distillation under
vacuum. Linear low density poly(ethylene) (LLDPE) (Rayson, India,
Mw – 1,00,000 Da) was purchased and purified by the procedure
followed in our earlier publication [22]. Toluene (Chemspure, AR,
India) and acetone (Merck, India) were received and used without
further purification. Dicumyl peroxide initiator (DCP, Across Chem-
icals, UK) and cyclohexane (Paxy Chemicals, AR, India) were used
as received.
2.1.1. Synthesis of barium diacrylate (Ba DA)
10 g of BaCO3 was dissolved in 200 mL of double distilled water
(DD) in a three-necked round bottom (RB) flask. 10 mL of acrylic
acid was added drop by drop to the BaCO3 solution followed by
0.03 g of antimony trioxide, the esterification catalyst, to catalyze
the metal ester formation process. The contents were sparged with
nitrogen gas to create an inert atmosphere inside the flask. The RB
flask was connected to a water condenser and the solution was
boiled for 3 h continuously with vigorous stirring at 90 ◦C. Finally,
the precipitate obtained {Ba DA} was washed with acetone and the
sample was dried, weighed and stored in a zipper bag. The same
procedure was adopted for the synthesis of other metal esters [26]
and abbreviated as Ba DMA, Mg DA, Mg DMA, Mn DA and Mn DMA.
2.2. Characterizations
FTIR spectra were recorded using 8400 S Shimadzu FTIR
spectrometer, Japan, by KBr pelletization method from 400 to
4000 cm−1. In order to avoid the error while recording FTIR spec-
trum, the corrected peak area was considered. To cross check
the corrected peak area values, the FTIR spectrum was recorded
for the same sample disc in different parts. After proper base
line correction with the aid of FTIR software, again one can
get the same corrected peak area values. FTIR spectrum was
recorded for three times for the same sample disc, one can get
the same and repeated corrected peak area values. The FTIR spec-
trum was recorded without predicting the lower and upper limits
of peak, because the software itself predicted exactly the lower
and upper limits to nullify the errors. In such a way the errors
were nullified. Further, one can cross check the efficiency of
FTIR software by manually predicting the lower and upper lim-
its and the corrected peak area was determined. In this case one
can get the same corrected peak area value as reported previ-
ously (without predicting the lower and upper peak limits). For
the quantitative determination of % ester grafting, the follow-
ing corrected areas of the peaks, which were assigned at 1730
(C O form) and 721 (C–H out of plane bending vibration) cm−1
were determined and the relative intensity (RI) was calculated as
follows:
2.1.2. Purification of LLDPE
5 g of LLDPE pellet sample was dissolved in 100 mL of toluene
solvent at 140 ◦C for 3 h in order to remove the antioxidants, added
during its long storage process. Once all the LLDPE powder sam-
ples were dissolved in toluene, the contents became clear viscous
solution, then cooled and 800 mL of acetone was added to precipi-
tate the LLDPE [22]. Filtered the contents and dried at 60 ◦C for 24 h
under vacuum. In order to confirm the complete removal of toluene
from the purified LLDPE, the purified sample was weighed and com-
pared with the amount of LLDPE pellet taken initially. Further, it can
be analyzed by recording the FTIR spectrum for the purified sam-
ple. The absence of an aromatic rocking and wagging stretching in
the finger print region of FTIR spectrum confirmed the absence of
toluene solvent after the vacuum drying at 60 ◦C for 24 h. The dis-
solution and precipitation process were repeated for three times
to further purify the LLDPE sample. Finally, the dried samples were
weighed and stored in a zipper bag.
RI of ester carbonyl (RI[C=O/C−H]) = A1730/A721
RI[C=O/C−H] × W
(1)
(2)
% Ester grafting =
× 100
C × 1.5
Where, W is the weight of non-cross linked ester grafted poly-
mer taken for FTIR study, C is the % weight of peroxide used, 1.5 is
the proportionalityconstantasmentionedin our earlier publication
[25]. The % cross-linking was determined by using the following
formula:
2.1.3. Synthesis of LLDPE-g-Ba DA
1 g of pure LLDPE powder sample was added with 1% weight
of Ba DA in 25 mL of cyclohexane–dichloromethane (1:9 v/v)
[Weight of polymer taken for functionalization] − [Weight of non-cross linked polymer obtained after functionalization]
% cross-linking =
× 100
(3)
Weight of polymer taken for functionalization
TGA was recorded using Universal V4.3A TA instrument, Japan
under air atmosphere from room temperature to 800 ◦C at the
heating rate of 10 ◦C/min. DSC of the sample was recorded using
Universal V4.3A TA instrument under nitrogen atmosphere at the
heating rate of 10 ◦C/min from room temperature to 300 ◦C. HRTEM
was recorded for Mg DMA by using a TEM 3010, a product of JEOL.
solvent mixture in a 100 mL beaker with mild stirring. The solvent
mixture was used to distribute the DCP and Ba DA onto LLDPE
backbone uniformly, otherwise agglomeration occurred. Then 1%
weight of DCP was mixed with the content of the beaker and
the stirring was continued for 1 h. In the present investigation,
both DCP and esters or Ba DA were used in equal concentra-
tions, particularly with 1:1 ratio, after many trial experiments.
After 1 h of mixing, the solvent was removed by rotary evap-
oration. The reaction mixture was transferred into a test tube
reactor and de-aerated for 30 min with sulphur free nitrogen gas.
3. Results and discussion
For the sake of convenience the results and discussion part is
sub-divided into two parts namely, (1) synthesis and characteri-

R. Anbarasan, V. Dhanalakshmi / Spectrochimica Acta Part A 76 (2010) 37–44
39
zations of metal containing divinyl monomers, (2) melt grafting of
metal containing divinyl monomer onto LLDPE backbone.
3.1. Synthesis and characterizations of metal containing divinyl
monomers
3.1.1. FTIR study
Fig. 1 shows the FTIR spectra of metal acrylates and metal
methacrylates. Fig. 1a represents the FTIR spectrum of Ba DA. The
important peaks are characterized below. A broad peak around
3500 cm−1 is due to the OH stretching of water molecules attached
with the central metal ion. The C–H symmetric and anti-symmetric
stretching is observed as a hump at 2909 and 2973 cm−1 respec-
tively. The C O stretching is observed at 1721 cm−1. The C
C
stretch can be seen at 1647 cm−1. The same peak is also corre-
sponding to the bending vibration of water molecules as well as
the CO2−M+ stretching. The C–H bending vibration is observed
at 1562 cm−1. The metal ester linkage (C–O–M) is appeared at
1076 cm−1. A twin peak appears at 637 and 600 cm−1 are respon-
sible for the C–H out of plane bending and metal oxide stretching
respectively.
Fig. 1b exhibits the FTIR spectrum of Ba DMA. A sharp peak at
3561 cm−1 is accounted by the stretching of existence of two Ba ions
in the same crystalline plane. The 2917 and 1977 cm−1 peaks are
corresponding to the C–H symmetric and anti-symmetric stretch-
ing of Ba DMA. A small hump appeared at 1738 cm−1 is responsible
for the carbonyl stretching. A sharp peak at 1648 cm−1 is due to
the C C stretching. The metal ester linkage, C–H out of plane bend-
ing vibration and metal oxide stretching are observed at 1011, 833
and 506 cm−1 respectively. The shifting of peak is due to the influ-
ence of bulky methyl substituent present in the Ba DMA. Thus FTIR
spectrum confirmed the presence of functional groups in Ba salts.
Fig. 1c and d represent the FTIR spectra of Mg DA and Mg
DMA respectively. Here also one can observe the above-mentioned
peaks. The FTIR spectrum of Mn DA and Mn DMA are given in Fig. 1e
and f respectively. These systems too exhibited the same peaks as
mentioned above.
Fig. 2. TGA of (a) Ba DA, (b) Ba DMA, (c) Mg DA, (d) Mg DMA, (e) Mn DA, (f) Mn DMA.
age. The third major weight loss step is started at 450 ◦C and extend
up to 529 ◦C, due to the degradation of ester linkage with simulta-
neous evolution of CO2. Above 750 ◦C, the system exhibited 69.9%
weight residue remained due to the formation of BaO. This is sim-
ilar to our earlier communication [26]. The data is mentioned in
Table 1. The first minor weight loss step due to the removal of water
molecule is supporting the FTIR spectrum of Ba DA.
The TGA thermogram of Ba DMA is shown in Fig. 2b. The ther-
mogram exhibited a four-step degradation process. The first minor
weight loss step before 100 ◦C is associated with the removal
of moisture and physisorbed water molecules. The chemisorbed
water molecules are expelled before 210 ◦C. In comparison, the
Ba DMA had more physisorbed and chemisorbed water molecules
than the Ba DA system. This can be evidenced by seeing the weight
loss step below 210 ◦C for both the systems. This can be explained
as follows: (1) during the preparation of Ba DMA, the central Ba
ion might be in nano size and it should be smaller than the Ba DA.
(2) Availability of more surface area for holding the physisorbed
or chemisorbed water molecules. (3) Due to the presence of steric
effect caused by the methyl groups, nano porous structure might
be formed and which must be responsible for holding the water
molecules. Further research work on HRTEM of Ba DA and Ba DMA
is going on in our research lab. Third and fourth weight loss steps
are corresponding to the dissociation and degradation of metal
ester linkage as mentioned above. Above 750 ◦C, it showed 55.1%
weight residue remained. The metal ester degradation was started
at 393 ◦C. When compared with Ba DA, the present system showed
a lower thermal stability due to the presence of bulky methyl
substituent in Ba DMA, which caused steric effect. The data is men-
tioned in Table 1.
3.1.2. TGA history
The TGA thermogram of Ba DA is shown in Fig. 2a. The ther-
mogram showed a three-step degradation process. The first minor
weight loss step up to 133 ◦C is due to the removal of physisorbed
and chemisorbed water molecules. The second minor weight loss
step up to 442 ◦C is ascribed to the dissociation of metal ester link-
Fig. 2c exhibits the TGA thermogram of Mg DA. It showed
a four-step degradation process, as mentioned above. Here the
metal ester degradation was started at 421 ◦C and above 750 ◦C it
showed 18.2% weight residue remained. Fig. 2d reveals the ther-
mogram of Mg DMA. It showed a three-step degradation process.
The third major weight loss step and dissociation of metal ester
were startedat458 ◦C. Above750 ◦C, it yielded15.6% weight residue
remained. The data is mentioned in Table 1. In comparison, the Mg
DA system showed the higher % weight residue remained above
750 ◦C whereas the Mg DMA system exhibited a higher metal ester
degradation temperature. In comparison with previous Ba system,
the metal ester degradation temperature is higher for Mg system
whereas the % weight residue remained above 750 ◦C is higher for
Ba system. This is due to the smaller size of Mg ion (3s2 level con-
figuration) [27].
Fig. 1. FTIR spectra of (a) Ba DA, (b) Ba DMA, (c) Mg DA, (d) Mg DMA, (e) Mn DA, (f)
Mn DMA.

40
R. Anbarasan, V. Dhanalakshmi / Spectrochimica Acta Part A 76 (2010) 37–44
Table 1
TGA and DSC data of metal esters.
System
Metal ester degradation
% weight residue
Removal of physisorbed
Removal of chemisorbed
water (◦C)
temperature (◦C)
remained above 750 ◦
C
water (◦C)
Ba DA
Ba DMA
Mg DA
Mg DMA
Mn DA
Mn DMA
450
392
429
458
413
278
69.9
55.1
18.2
15.6
26.7
25.1
88.3
79.6
90.6
116.7
97.9
81.6
119.1
110.4
130.2
153.6
–
110.7
Fig. 2e reveals the TGA thermogram of Mn DA. This system
exhibited a four-step degradation process as explained for previ-
ous systems. The metal ester degradation was started at 413 ◦C and
it showed 26.7% weight residue remained above 750 ◦C. The TGA
thermogram of Mn DMA is shown in Fig. 2f with four-step degra-
dation process. The metal ester degradation was started at 278.6 ◦C
and above 750 ◦C it showed 25.1% weight residue remained. The
data is mentioned in Table 1. In comparison, the Mn DA showed
higher thermal stability than the Mn DMA. This can be explained
on the basis of steric repulsion. In the case of Mn DMA, the bulky
size methyl substituent caused steric effect and de-stabilized the
thermal stability of Mn DMA.
In overall comparison, the Mn DMA system exhibited lower
metal ester degradation temperature due to 3d5 4s2 configuration
[27] whereas the Ba DA showed higher % weight residue remained
above 750 ◦C due to the 6s2 configuration level. The TGA thermo-
gram also supported the FTIR spectrum for the presence of water
molecules attached with the central metal ion.
temperature. (2) While introducing a methyl substituent in the
acrylate group which has not only increased the molecular weight
but also improved the hydrophobic character (non-homogeneity).
Hence, due to these two reasons the water molecules were removed
from the central metal ion at lower temperature.
The DSC heating scan of Mg DA and Mg DMA is indicated in
Fig. 3c and d respectively. The Td.w of Mg system is higher than that
of Ba system (Table 1). This can be explained as follows. During
the synthesis of Mg DA or Mg DMA, the size of central metal ion
was reduced to the nano size. When the size of the metal ion is
reduced to smaller and smaller, the inorganic phase of metal ion is
transferred to organic phase. This concept is similar to that of disso-
lution of Ag nano particles in both water and toluene medium [28].
The same principle is applied to the present system. The reduction
in size of central metal ion led to the formation of homogeneity
(i.e.) organic phase. The formation of homogeneity can be further
confirmed with Mg DMA. While introducing a bulky methyl sub-
stituent in the acrylate, which further increased the hydrophobic
character with the simultaneous reduction in size of Mg2+ ion. The
reduction in size (i.e.) nano size of Mg2+ ion can be confirmed by
observing the topography of the same. Fig. 4 represents the HRTEM
images of Mg DMA. Fig. 4a indicates the ordered structure of Mg
ions with the length of 3 nm. Fig. 4b represents the nano hexagon
and with distorted spherical morphology of central Mg ions. Fig. 4
confirms the nano size of the central metal ion. The nano sized Mg2+
ion expelled the water molecules at somewhat higher temperature
due to its larger surface area. The surface area of nano sized Mg ion
is responsible for holding the water molecules.
The DSC heating scan of Mn DA and DMA is given in Fig. 3e
and f respectively. Fig. 3e (Mn DA) shows only one endothermic
peak (94.5 ◦C), corresponding to the removal of physisorbed water
molecules from the central metal ion. Fig. 3f represents the DSC
heating scan of Mn DMA with two endothermic peaks, correspond-
ing to the removal of physisorbed (82 ◦C) and chemisorbed (112 ◦C)
water molecules. The Mn DMA system showed a lower Td.w. due to
the increase in hydrophobicity. In 2004, Walker et al. [1] reported
about the DSC and TGA of various metal acrylates. An endother-
mic peak appeared around 125 ◦C in DSC analysis was explained
well by them based on the removal of superficial and structural
water molecules. Further, the water removal from the metal salt
was confirmed through TGA method. Our report is co-inside with
them [1].
3.1.3. DSC profile
The FTIR spectrum showed the attachment of water molecules
with the central metal ion. Further, it was supported by TGA anal-
ysis. The DSC profile confirmed the presence of water molecules in
the metal esters. Fig. 3 shows the DSC thermogram of various metal
esters. Fig. 3a represents the DSC heating scan of Ba DA. It showed
two endothermic peaks at 88.3 and 119.1 ◦C corresponding to the
removal of physisorbed and chemisorbed water molecules. Fig. 3b
indicates the DSC heating scan of Ba DMA. This system too exhib-
ited two endothermic peaks at 79.6 and 110.4 ◦C (Table 1) due to the
both physisorbed and chemisorbed water molecules respectively.
Appearance of these two endothermic peaks confirmed the pres-
ence of water molecules attached with the central metal ion [26]. In
comparison, the Ba DMA system showed lower de-watering tem-
perature (Td.w.) than the Ba DA system. The decrease in Td.w. of Ba
DMA can be explained as follows. (1) Presence of bulky methyl sub-
stituent de-stabilize the thermal stability as well as phase transition
In overall comparison, the Mg salts particularly Mg DMA exhib-
ited higher Td.w due to its nano size with larger surface area. The
water molecules were adsorbed on the surface of the central metal
ion strongly and yielded higher Td.w. The DSC heating scan of metal
esters confirmed the presence of water molecules attached with
the central metal ion.
3.2. Melt grafting of metal containing divinyl monomers onto
LLDPE backbone
3.2.1. FTIR study
Fig. 5 indicates the FTIR spectra of 1–5% weight Ba DA loaded
LLDPE systems. Fig. 5a reveals the FTIR spectrum of pristine LLDPE.
Fig. 3. DSC of (a) Ba DA, (b) Ba DMA, (c) Mg DA, (d) Mg DMA, (e) Mn DA, (f) Mn DMA.

R. Anbarasan, V. Dhanalakshmi / Spectrochimica Acta Part A 76 (2010) 37–44
41
Fig. 4. HRTEM of Mg DMA, (a) ordered nano structure, (b) nano hexagon morphology.
The important peaks are characterized below. A broad peak around
2896 cm−1 is due to the anti-symmetric stretching. The C–H sym-
metric stretching vibration is observed at 2655 cm−1. The C–H
bending and out of plane bending vibration are seen at 1460 and
721 cm−1 respectively. Fig. 5 (b–f) indicates the FTIR spectra of
1–5% weight Ba DA loaded LLDPE. The spectra showed some new
peaks apart from the peaks of pristine LLDPE. They are character-
ized below. A broad peak around 3500 cm−1 is ascribed to the OH
stretching of water molecules attached with Ba DA. Two molecules
of water are attached with the central Ba metal ion. This is in accor-
dance with our earlier publication [26]. The ester grafting can be
confirmed by representing a peak at 1721 cm−1 due to the ester car-
bonyl group. The bending vibration of water and CO2 M+ stretching
−
are merged and observed as a broad peak at 1556 cm−1. A broad
peak around 1038 cm−1 is responsible for the metal ester, C–O–M
linkage. The Ba–O stretching is seen at 553 cm−1. Appearance of
these new peaks confirmed the chemical grafting of Ba DA onto
LLDPE backbone.
Fig. 6. Effect of (% weight of DCP) on RI[C=O/C–H] of (a) Ba DA, (b) Ba DMA, (c) Mg DA,
(d) Mg DMA, (e) Mn DA, (f) Mn DMA systems.
The interesting point observed here is while increasing the %
weight loading of Ba DA, the RI of [C O/C–H] is also increased. This
argued that the chemical grafting increased with the increase of %
weight loading of Ba DA. We know that the metal esters are hav-
ing the melting temperature above 400 ◦C and the grafting reaction
is occurred through the dissolution of metal esters in the molten
state of LLDPE. In the present investigation, the DCP and Ba DA were
used in equal concentration. Fig. 6a shows the plot of log(% weight
of DCP) vs. log(RI[C O/C–H]). The normalized values are presented
in Fig. 6. The plot showed a straight line with the slope value of
1.93, which declared the 2.0 order dependence of grafting reac-
tion with respect to % weight of DCP. It means that 2 mol of DCP
are required to functionalize 1 mol of LLDPE. The rate of function-
alization reaction (Rf) can be written as follows: Rf ␣ (% weight of
DCP)1.93. The second order of functionalization reaction inferred
that the termination reaction occurred through the bi-molecular
termination mechanism. The % grafting values are mentioned in
Table 2. Recently, Parthasarathi et al. [25] found similar type of
results during the melt graft functionalization of mercapto esters
Table 2
Effect of Ba DA and Ba DMA on % functionalization and % cross-linking.
% weight loading
Ba DA
Ba DMA
% funct.
% funct.
% C.L.
% C.L.
1
2
3
4
5
46.7
49.5
53.1
57.5
62.6
30.8
38.2
51.5
65.7
80.1
33.8
37.5
41.3
48.7
55.1
36.2
45.7
61.4
72.8
85.3
Fig. 5. FTIR spectra of LLDPE loaded with Ba DA at (a) 0% weight, (b) 1% weight, (c)
2% weight, (d) 3% weight, (e) 4% weight, (f) 5% weight.

42
R. Anbarasan, V. Dhanalakshmi / Spectrochimica Acta Part A 76 (2010) 37–44
Fig. 8. FTIR spectra of LLDPE loaded with Mg DA at (a) 1% weight, (b) 2% weight, (c)
3% weight, (d) 4% weight, (e) 5% weight.
Fig. 7. FTIR spectra of LLDPE loaded with Ba DMA at (a) 1% weight, (b) 2% weight,
(c) 3% weight, (d) 4% weight, (e) 5% weight.
Table 3
with HDPE. The Ba DA contains two C C double bonds. A broad
peak at 1571 cm−1 is due to the combination of OH bending vibra-
tion and CO2−M+ stretching vibrations. Hence the grafting of Ba
Effect of Mg DA and Mg DMA on % functionalization and % cross-linking.
% weight loading
Mg DA
Mg DMA
% funct.
DA onto LLDPE backbone occurred through the cleavage of C
C
% funct.
% C.L.
% C.L.
double bonds. The competitive reaction during the melt graft func-
tionalization reaction is the C.L reaction. C.L is due to the coupling
between LLDPE macro radicals. Table 2 indicates the % C.L values.
The % C.L values increased with the increase of % weight loading of
Ba DA.
1
2
3
4
5
50.1
56.4
65.3
74.8
85.7
10.4
14.6
19.3
25.7
29.8
42.6
48.5
57.3
66.8
75.6
16.2
22.1
27.6
32.6
38.4
Fig. 7 explains the FTIR spectra of 1–5% weight Ba DMA
loaded LLDPE system. The DCP concentration and metal ester
concentration was varied equally. Here also one can observe the
above-mentioned peaks. While increasing the % weight loading of
DCP, the RI of [C O/C–H] is also increased. This is due to the more
and more chemical grafting of Ba DMA onto LLDPE backbone. In
order to find out the order of functionalization reaction, the fol-
lowing universal log–log plot was made. Fig. 6b shows the plot of
log(% weight of DCP) vs. log(RI[C=O/C–H]). The plot showed a straight
line with the slope value of 1.98. Rf ␣ (% weight of DCP)1.98. This
claimed the 2.0 order of melt functionalization reaction. The Ba
DMA system also yielded the bi-molecular termination reaction. In
the case of Ba DMA, 2 mol of Ba DMA are required to functionalize
1 mol of LLDPE. The % grafting values and % C.L values are included
in Table 2. In critical comparison, Ba DA system exhibited higher %
grafting values due to the absence of steric effect. The Ba DMA sys-
tem revealed the higher % C.L. values due to slow rate of formation
of Ba DMA radicals.
slope value of 1.05. Rf ␣ (% weight of DCP)1.05. 1 mol of Mg DMA is
required to functionalize 1 mol of LLDPE. The % functionalization
and % C.L values are represented in Table 3. In comparison, the %
grafting values are greater than that of % C.L. Mg DA system exhib-
ited a higher % functionalization values due to the absence of steric
effect and the Mg DMA system revealed the higher % C.L. due to
the presence of steric effect and slow production of Mg DMA radi-
cals. Even though, the Mg DMA maintained the homogeneity with
LLDPE in its molten condition, due to the presence of bulky size
methyl substituent that led to the steric effect and resulted with
lower % grafting. By comparing Ba and Mg systems, the Mg system
The FTIR spectra of 1–5% weight Mg DA loaded LLDPE is shown in
Fig. 8. While increasing the % weight of Mg DA, the RI of [C O/C–H]
is also increased. At higher % weight of loading of Mg DA, the car-
bonyl stretching and the bending vibration of water molecules were
merged and the carbonyl peak was observed like a hump. The
remaining peaks are similar to that of Ba DA–LLDPE system. The
order of functionalization reaction can be determined by plotting
log(% weight of DCP) vs. log(RI[C=O/C–H]) (Fig. 6c). The plot exhib-
ited a straight line with a slope value of 0.63, which concluded
the 0.50 order of functionalization reaction (i.e.) Rf ␣ (% weight of
DCP)0.63. 0.50 mol of Mg DA is required to functionalize 1 mol of
LLDPE. This is in accordance with literature report [26]. The % graft-
ing and % C.L. values are mentioned in Table 3. Fig. 9 exhibits the
FTIR spectra of 1–5% weight Mg DMA loaded LLDPE system. The
RI of [C O/C–H] is increased with the simultaneous increase of %
weight loading of Mg DMA. Fig. 6d indicates the plot of log(% weight
of DCP) vs. log(RI[C=O/C–H]). The plot showed a straight line with the
Fig. 9. FTIR spectra of LLDPE loaded with Mg DMA at (a) 1% weight, (b) 2% weight,
(c) 3% weight, (d) 4% weight, (e) 5% weight.

R. Anbarasan, V. Dhanalakshmi / Spectrochimica Acta Part A 76 (2010) 37–44
43
Table 4
Effect of Mn DA and Mn DMA on % functionalization and % cross-linking.
% weight loading
Mn DA
Mn DMA
% funct.
% funct.
% C.L.
% C.L.
1
2
3
4
5
54.5
59.8
63.4
68.7
74.9
24.6
36.1
47.4
56.7
65.8
48.9
52.5
57.3
62.8
68.7
32.8
44.5
52.1
62.4
73.7
the increase of % weight of Mn DA. This confirmed the chemical
grafting of Mn DA onto LLDPE backbone. The order of functionaliza-
tion reaction can be determined by drawing a plot of log(% weight
of DCP) vs. log(RI[C=O/C–H]) (Fig. 6e). The plot yielded a straight
line with the slope value of 1.56. Rf ␣ (% weight of DCP)1.56. The
slope value confirmed the 1.50 order of functionalization reaction
with respect to % weight of DCP. The % grafting and % C.L. values
are mentioned in Table 4. Fig. 11 shows the FTIR spectra of 1–5%
weight Mn DMA loaded LLDPE system. The order of functional-
ization reaction was determined by plotting log(% weight of DCP)
vs. log(RI[C=O/C–H]) (Fig. 6f) as 1.70. Rf ␣ (% weight of DCP)1.70. This
inferred that 1.75 mol of Mn DMA was required to functionalize
1 mol of LLDPE. On comparison, the Mn DA system gave higher %
grafting due to smaller in size without steric effect and Mn DMA sys-
tem yielded higher % C.L values due to the presence of steric effect
Fig. 10. FTIR spectra of LLDPE loaded with Mn DA at (a) 1% weight, (b) 2% weight,
(c) 3% weight, (d) 4% weight, (e) 5% weight.
yielded higher % functionalization and the Ba system gave higher %
C.L. values.
Fig. 10 represents the FTIR spectra of 1–5% weight Mn DA loaded
LLDPE system. Here also the RI of [C O/C–H] was increased with
Scheme 1. Melt functionalization of metal ester with LLDPE.

44
R. Anbarasan, V. Dhanalakshmi / Spectrochimica Acta Part A 76 (2010) 37–44
tion. By this way, the experimental results obtained through various
chemical reactions and proposed reactions scheme are matching
with each other. Reactions are mentioned in Scheme 1.
4. Conclusions
From the above kinetic study the important points are presented
here as conclusions. (1) The DAs yielded the higher % functionaliza-
tion and DMAs produced the higher % C.L. values. (2) The Mg salts
exhibited the higher Td.w and % functionalization values due to the
homogeneity with LLDPE in its molten state. (3) The Mg DA showed
the 0.50 order of functionalization reaction whereas the Mg DMA
exhibited the 1.0 order of functionalization reaction with respect to
% weight of DCP. (4) Ba DA showed 69.9% weight residue remained
above 750 ◦C in TGA analysis. (5) The RI[C=O/C–H] was increased with
the increase of % weight of metal salts due to more and more chemi-
cal grafting onto LLDPE backbone in the presence of DCP under inert
atmosphere at 160 ◦C. (6) The kinetics of Ba salts declared that the
melt functionalization reaction occurred through the bi-molecular
termination reaction.
Fig. 11. FTIR spectra of LLDPE loaded with Mn DMA at (a) 1% weight, (b) 2% weight,
(c) 3% weight, (d) 4% weight, (e) 5% weight.
Acknowledgement
[26] and slow production of Mn DMA radicals. Table 4 exhibits the
% grafting as well as % C.L values.
DST, New Delhi is gratefully acknowledged for the financial sup-
port (Ref. No. SR/FTP /CS-39/2005).
In overall comparison, Mg DA monomer yielded higher % graft-
ing due to the nano size, better miscibility with LLDPE in its
molten condition and the absence of steric effect. The Ba con-
taining monomers gave higher % C.L values due to the presence
of steric effect and very slow production of radicals with non-
homogeneity. These results inferred that both grafting and C.L
efficiency depended on the size and homogeneity (miscibility) of
monomer with LLDPE in its molten state.
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Parthasarathi et al. [25] explained the mechanism of free radical
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DCP, the free radical initiator, produced two cumyloxy radicals
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