By Naoki Oguri and Poongzag Kirn

DESIGN AND APPLICATIONS OF
A Curie point pirolyzer
THE TECHNIQUS of pyrolysisi
analysis or analysis of thethermal decomposition products of a substance brought about
by heat has been used successfullyin the manufacture or the Pyroroil(Japan Analytical Industry Co.,Ltd., Japan) Curie point pyrolyzer(PCPP) for the characterization or
rubbers and industrial polymers(Figure 1 ).
The most important requirementsor pyrolysis are: 1 ) Good reproducibility-the sample should be heatedto a high and constant temperature
with good reproducibility so that accurate analysis can be obtained; 2)
Rapid rise time-the pyrolyzed
sample should not be allowed to induce secondary reactions during theprimary pyrolysis step: 3) Sample
preparation-any form or sample
may be analyzed directly without
any sample preparation by simply
wrapping and dipping the sample in
the foil or wire; 4) Accurate temperature measurement-because theCurie point temperature is so accurate and reproducible. accuratequantitative analyses are ensured
time after time.

Principle
To understand the operation of theCPP, it is necessary to understandthe basic principle on which this operation is based. When a strong ferromagnetic material is placed inside
a conducting coil, and a direct current is passed through the coil, theferromagnetic material is transformed into a magnet, and a magnetic field is created. If the directionof the current is changed, the polarity of the magnet is reversed, i.e"
N→S is reversed to S→N. Whenthe polarity of the coil is changed
rapidly. heat is generated from theferromagnetic material. Heat generated by this action causes the ferromagnetic material to reach its
Curie point temperature. where themagnetic property is lost, and thetemperature is maintained constant
The time taken to reach the Curie
point temperature is less than 0.2
sec. By varying the alloy or theferromagnetic materials, it is possible to accurately choose different
Curie point temperatures. Japan

Analytical Industry offers a range
or nineteen different temperaturesfrom l60℃ to 1140℃.

System description
The Pyrofoil Curie point pyrolyzer meets and exceeds the abovementioned requirements of pyrolysis. When each ferromagnetic
pyrofoil reaches its Curie point. it
maintains an exact temperature(Figure 2). No significant secondary reactions lake place because orafter cleaning with solvents or acids.

Experimental
When a radio frequency (RF)field is applied to the coil, the ferromagnetic foil or wire reaches its
respective Curie point temperature.
The pyrolysis time is controlled bya timer. The pyrolysis products fromthe pyrofoil or the wire are thentransferred to the gas chromatograph(GC-MS/GC-IR) via a heated transfer line by the carrier gas. The instrument has a long transfer line tointerface it with any type of GC or
GC-IR, or GC-MS. The quartz Sample tube can be cleaned by solvents,acids, or by firing.

the extremely rapid rise time. Asolid sample can be wrapped in apyrofoil prior to being inserted into
the pyrolyzer. Since Only a minutequantity of sample is needed for thepyrolysis, a liquid sample can beplaced on the pyrofoil with a microsyringe. As each foil has its own
Curie point temperature, it is notnecessary to set the pyrolysis temperature. The Curie point tempera-ture of the foil selected is alreadyknown (Figure 3).
A block diagram of the Pyrofoil
Curie point pyrolyzer model JHP-22
is shown in Figure 4. It consists ofa quartz tube and a pyrofoil or pyrowire in the middle of the system.
Solid samples are simply weighed
and wrapped in the pyrofoil. Liquidsamples can be coated on a pyrofoilor pyrowire. Both can be reused

Advantages of the Curie point
pyrolyzer
The Pyrofoil Curie point pyrolyzer-GC (GC-MS/GC-IR) method
is simple and very effective for theidentification of synthetic polymers.
The results give information on thestructural composition, microstructure identification, thermal stability,and quantitative distribution of polymers. In order to obtain reliable
data, the aforementioned criteria
must again be emphasized. Figure

5a and b shows the difference inpyrograms obtained from styrene
butadiene rubber (SSR) with theCurie point pyrolyzer and the furnace-type pyrolyzer. Figure 5ashows sharp characteristic peaks.
Figure 5b demonstrates longer reten(ion times, broad peak shapes.
and interference peaks at the shoulder of the butadiene peak. As a result. good quantitation cannot be expected from this pyrogram. Figure
6 shows the difference between
three types of pyrolysis when NR/
SBR is pyrolyzed. In the pyrolysis
tube of the furnace-type pyrolyzer,
the temperature distribution is large
and therefore the reproducibility is
not good. The pyrolysis temperature
varies depending on the position of
the sample insert.

In addition, lower molecular species are produced in the furnace-type
pyrolyzer which may be due to thesecondary reactions occurring in along tube where the temperature distribution is large or the rise time islong. For the filament type and theCurie point type, reproducibility isgood. But the yield of the pyrolysis
products depends on the sample
amount in the filament type.
Selection of the pyrolysis temperature plays an important role in thepyrolysis. Figure 7 shows the relationship between the pyrolysis
temperature and the yield of thecharacteristic pyrolysis products ofSBR. From Figure 7a (obtainedfrom the furnace-type pyrolyzer),
one can clearly see that one of thecharacteristic peaks, namely butadiene, is missing. and the yield islow. Figtlre 7b (obtained from thefilament-type pyrolyzer) gives threecharacteristic pyrolysis products of

SBR, but the yield is somewhat
lower than those seen in Figure 7c(obtained from the Curie pointpyrolyzer).
In the pyrolysis of polymers, obtaining reproducible data is a problem. This problem is normally attributed to the reproducible pyrolyzing
temperature, and the reproducibilityof the sample preparation. In sodoing, the quantity of sample pyrolyzed becomes an important factor. As we can see from Figures 8and 9, the Curie point pyrolyzerdemonstrates a constant yield of thepyrolysis products where the sample
weight increases by a factor of 3,
while the filament type pyrolyzer
shows an immediate fan off of theyield as the sample amount increases. This fact is due to the poor
heat transfer in the filament typewhen a large quantity of sample isplaced on a thin film. while in theCurie point pyrolyzer a good heattransfer occurs as Ions as the sample
contacts the large size of thepyrofoil.
The Pyrofoil Curie point pyrolyzer when coupled with a GC (GCMS or GC-IR), demonstrates a superiority to other analytical techniques. For the analysis of residual
solvent in magnetic wire, thermogravimetdc analysis (TGA), differential scanning calorimetry (DSC),
or cure test is commonly employed.
However, none of these methods
gives reproducible and accurate re-sults. The Pyrofoil Curie point pyrolyzer was found to overcome theproblems encountered in the abovementioned methods.
A PGC (pyrolyzer gas chromatograph) was also found to be a useful
tool to study the microstructures ofcopolymers.3.4
A few examples are given here.
Random and alternating copolymer
of vinyl chloride-methyl methacrylate and of vinyl vhloride-acrylonitrile were studied .5 Similarly, fivekinds of butadiene copolymers havebeen investigated.6 The sequential
distribution of copolymers was alsostudied on methyl methacrylate copolymers with styrene or α-methylstyrene.7 The pyrolysis - gas chromatographic behavior of poly (3methyl-1-butenes) and poly (3methyl-1-perltenes) with different
monomer units was investigated,
and the microstructure of the polymers was obtained.8
Therml degradation mechanism9of aromatic polyesters10 and thecross-link density of vulcanizedpolyisoprene11 were studied using a
Curie poirlt pyrolyzer and GC-MS.
Pyrolysis can be utilized as a fingerprint of polymer materials and biological samples. It can also can beused for the quantitative analysis ofthese types of materials.

Conclusion
PGC is an effective tool foranalyzing polymers and other typesof material. The fact that a minuteamount of sample composition canbe analyzed makes PGC superior toother techniques. Ease of sample
preparation, reproducibility, and accuracy of data are important in thiskind of work. Qualitative analysis
and quantitative analysis can be performed on the Pyrofoil Curie point
pyrolyzer. The ease in interfacing
the Pyrofoil Curie point pyrolyzer
to a GC, GC-MS, or GC-IR also
plays an important role.