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Identification and characterisation of high impact polystyrene Ч Part I Microscopic identification of high impact polystyrene filled with titanium dioxide.

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Die Angewandte Makromobkulare Chemie 12 (1970) 131-135 ( N r . 113)
From the Application Laboratory, Aquitaine Organico, Usine de Mont,
Mont-64, France
Identification and Characterisation of High
Impact Polystyrene Part I
Microscopic Identification of High Impact Polystyrene
Filled with !l!itsnium Dioxide
By K. V. C. RAO*
(Eingegangen a m 28. Juli 1969)
Phase contrast microscopy cannot be applied for the identification and cherecteriaetion of high impact polystyrenes if the h a 1 product is filled with titanium dioxide.
In such cases, coupling the solution of high impact polystyrene in a mixture of
chloroform and ether with a diazonium salt of p-nitroaniline results specifically in
the coloration of the elastomeric particles, which can be viewed clearly under the
microscope. It has been observed that the shape, size and dispersion of the elastomeric particles remain undisturbed during the coupling reaction.
Mit Titandioxid gefiilltes schlsgfestes Polystyrol kann nicht durch Phasenkontrsstmikroskopie identifiziert und cherahrisiert warden. Dagegen erhiilt man
durch Kupplung des Polymeren in einer Liisung in Chloroform/hher mit diazotiertem p-Nitroanilin eine spezifische Ftirbung der Kautschukteilchen, die unter
dam Mikroskop beobwhtet werden kann. Form, Gr6Be und Verteilung der Kautschukpartikel werden durch die Reaktion nicht veriindert.
Phase contrast microscopy has been extensively used in the identification1
and characterization of high impact polystyrenes (HIPS). But this technique
can not be used sucessfullywhen high impact polystyrene is Wed with titanium
dioxide. To facilitate the identification of HIPS by this technique, when it is
filled with titanium dioxide, a specific color reaction has been developed and
is reported in this communication.
Present address:
Indian Institute of Petroleum, Dehra Dun, India.
K. V. C. RAO
About 0.1 g of HIPS filled with titanium dioxide is dissolved in a mixture of
chloroform and ether (3: 1 by volume). Nearly 0.05 g of phenol is then added with
constant shaking, followed by an addition of 1 ml of 1 % sodium hydroxide solution.
The solution is allowed to cool for ten minutes and p-nitrodiazonium sulfate (prepared by usual method and preserved at low temperature) solution is slowly added
with occasional shaking till the red color initially formed disappears leaving behind
the yellow colored solution. The lower organic layer is separated and evaporated in
a watch glass at 60 "C. From the polymer left behind, a microscopic slide is prepared
by heating technique and is viewed through the microscope (under phaae contrast).
T h e polybutadiene particles appear aa red globules against white background of
titanium dioxide and thus permit the identification of HIPS.
All the chemicals used are of pure grade and high impact polystyrene is of
oommercial grade.
Resub and Discussions
As pointed out earlier, grafted and blended high impact polystyrene can be
distinguished by microscopic studies under phase contrast without much
difficulty. This is evident from Fig. 1 and 2 for grafted and blended HIPS,
Fig. 1. Photomicrographs
of High Impact Polystyrene.
Leqdne 625 (Grafted Product).
Fig. 2. Photomicrograph of
HIPS (blended).
High Impact Polyatyrene I
respectively. Grafted HIPS containing no titanium dioxide, when viewed
through pham contrast microscope, shows the prominance of polybutadienegraftpolymer particles as white globules against the black background of polystyrene phase. These globules are of regular spherical shape and the average
diameter is found to be 1.80 p with a dispersion of f 42 %. The same grafted
HIPS after the above described specific color reaction is shown in Fig. 3; it is
found that the diameter of polybutadiene particles is 1.75 p with a dispersion
of f 43%.
Fig. 3. Photomicrograph of
HIPS. Laqdne 625 after coloration.
Fig. 4. Photomicrograph of
HIPS. Laqdne 625 filledwith
Ti02 without coloration.
Fig. 5 .
Photomicrograph of
HIPS. Laqdne 626filled with
Ti02 after coloration.
K. V. C. RAO
Similarly the study is conducted with the HIPS produced by blending polybutadiene and polystyrene in absence of titanium dioxide. The photomicroscope
is shown in Fig. 2. The particles of polybutadiene are found to be of irregular
size and shape.
Commercial samples of HIPS filled with titanium dioxide (Dow466 and
Laqrbne 625) are subjected to phase contrast microscopy and the views without
and with the colour reaction are presented in Fig. 4 and 5, respectively. It is
noteworthy that polybutadiene particles cannot be seen and identified when
not subjected to the color reaction. However, after such a treatment polybutadiene particles are easily identified ~ E Ired colored globules (black spots in
the photo) against the white background. The average diameter computed is
found to be 1.80 p with a dispersion of f 44%.
It is obvious from the above discussion that the presence of titanium dioxide
makes the microscopic identification of polybutadiene in HIPS impossible.
MEYER et a12 pointed out that double bond containing compounds react with
the diazonium salts giving rise to slightly colored derivatives. Polybutadiene
in the graft or in tkee state contains ethylenic double bonds and color compounds mn be expected to be formed with azo dyes. While no experimental
evidence is available yet on the basis of the above evidence
applied to
organic compounds, the following mechanistic scheme can be advanced.
It is well-knownthat diazonium salts do react by substitution to give slightly
colored compounds as e. g.
=C- CH2-]-
(Light orange color)
In the present axe,the product obtained in the absence of phenol is a light
orange colored compound but in presence of phenol an intense orange-red
colored compound is produced. The following substitution reaction presumably
takes place when p-nitro-diazoniumsalt and phenol are added:
High Impact Polyetyrene I
I.- f n-(
azo dye
(intenseorange red color)
From the preceding discussion it is quite evident that the specific color
reaction can be used successfully in the identification of high impact polystyrene by microscopy under phase contrast in presence of titanium dioxide.
The method is quicker and easier and can be used with minute quantities of
the samples in raw or finished state.
The author thanks the Director, Mr. DAUBA,
and the colleagues of Application Laboratory of Aquitaine Organico, France, for providing all the facilities
in carrying out the present work. Thanks are a180 due to Dr.S. K. BHATNAGAR
for his suggestions.
and P. A. TBAYLOR,
J. appl. Polymer Sci. 11 (1967) 2 361.
Ber. dtsch. chem. Ges. 47 (1914)
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titanium, dioxide, part, characterisation, microscopy, filled, high, identification, polystyrene, impact
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