Page 8 - Solutions for Plastic Evaluation

Evaluation of Raw Materials
Structure and Isomers
FTIR

Evaluation of Plastic Materials FTIR Analysis of Polybutadiene Microstructure Using Single Reflection ATR
Polybutadiene is a polymer with characteristics of both plastic and rubber. It is a collective term for multiple polymer configurations of
1,3-butadiene monomers. These can polymerize into three types of structures, the cis structure (cis-1,4-polybutadiene), the trans structure
(trans-1,4-polybutadiene), and the vinyl structure (1,2-polybutadiene). Of these structures, polybutadienes containing larger amounts of
the plastic-like vinyl structure are used for applications such as wrapping films, whereas polybutadienes containing larger concentrations of
the rubber-like cis structure are used for rubber products, such as tires and belts.

Evaluation of Raw Materials -CH2 CH2- -CH2 -(CH2CHCHCH2)n-
1,3-butadiene: CH2=CH-CH=CH2

-CH2-CH-

CH CH CH CH CH- CH2
CH2- Vinyl Structure
Product Evaluation The proportion of cis, trans, and vinyl structures in a polybutadiene can be determined using NMR spectra, infrared spectra, and
Trans Structure
Cis Structure

other methods. The Morero method using infrared spectra is considered useful if the polymer contains a high proportion of cis
structures. The Morero method involves dissolving the sample in carbon disulfide and measuring the transmittance using a fixed
cell with 1 mm optical path length. Then the proportion of each structure is determined from the absorbance of the cis, trans,
Product Information using dispersive IR systems for quantitation. However, this method requires weighing and dissolving samples, cleaning cells, and
and vinyl group peaks. Since this method uses transmittance measured using a fixed cell, it provides good sensitivity and enables
other processing. It also requires a significant amount of carbon disulfide. In contrast, the ATR method allows measuring samples
directly, without requiring any pretreatment, and the prism can be cleaned with a tiny amount of alcohol or other cleaner.

Shown below are spectra of polybutadiene with 90% or
higher cis content obtained using a DuraSamplIR II single
reflection ATR attachment. The peaks near 733 cm , 912 cm ,
-1
-1
and 966 cm correspond to cis, vinyl, and trans groups,
-1
respectively. Calibration curves for each group are shown to
the right, all of which show good linearity. 5
Cis
3.0
Tr
%
r=

0.2 0.3 0.4 0
Trans Concentration contrast, Wavenumber range : 944.9-

ATR Spectra of Polybutadiene Calibration Curves for Cis, Trans, and Vinyl Groups

8 LAAN-D-XX006