In-Line Monitoring and Spectral Analysis of Polymer Blend Dispersion in Microcompounder

Article abstract of DOI:10.1080/15421406.2019.1651071

Microcompounders are the most common compounding machines for making polymer composites. The torque rheometry is an effective tool for predicting the processing characteristics of thermoplastic polymers. It provides continuous monitoring of torque and tem

Full text of DOI:10.1080/15421406.2019.1651071

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: https://www.tandfonline.com/loi/gmcl20
In-Line Monitoring and Spectral Analysis of
Polymer Blend Dispersion in Microcompounder
Won Taek Oh, Myung Ho Kim, Quyen Do, Namchul Cho & Tae-Dong Kim
To cite this article: Won Taek Oh, Myung Ho Kim, Quyen Do, Namchul Cho & Tae-Dong Kim
(2019) In-Line Monitoring and Spectral Analysis of Polymer Blend Dispersion in Microcompounder,
Molecular Crystals and Liquid Crystals, 688:1, 75-81, DOI: 10.1080/15421406.2019.1651071
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MOLECULAR CRYSTALS AND LIQUID CRYSTALS
2019, VOL. 688, NO. 1, 75–81
https://doi.org/10.1080/15421406.2019.1651071
In-Line Monitoring and Spectral Analysis of Polymer Blend
Dispersion in Microcompounder
Won Taek Oha, Myung Ho Kima, Quyen Dob, Namchul Chob, and Tae-Dong Kima
b
aDepartment of Chemical Engineering and Advanced Materials, Hannam University; Department of
Energy Systems Engineering, Soonchunhyang University, Asan 31538, Republic of Korea
KEYWORDS
ABSTRACT
Microcompounders;
extrusion; tracers;
fluorescent
Microcompounders are the most common compounding machines
for making polymer composites. The torque rheometry is an effective
tool for predicting the processing characteristics of thermoplastic
polymers. It provides continuous monitoring of torque and tempera-
ture data during compounding which is a measure of processability.
In this work, we have studied the influence of processing parameters
on the dispersion degree of an anthracene derivative (AMA) in a
polystyrene matrix with respect to the rheological, structural, and
optical properties. The chemical structure of the synthesized AMA as
a tracer was confirmed by 1H NMR and thermal properties were
examined by DSC. In addition, a blend of polystyrene and AMA was
spin-coated on a glass substrate to investigate oxidation stability
confirmed by UV measurement. By using microcompounder, the
polymer blend with the AMA tracer was mixed and it was visually
indicated by fluorescent images.
images; monitoring
1. Introduction
Hot-melt extrusion (HME) is one of the most widely used processing techniques for the
plastic, pharmaceutical, and food industries [1–3]. It is a fully continuous manufacturing
technology in which raw materials are converted into products by forcing the formula-
tion through a die under various controlled conditions. Process monitoring systems
equipped in the HME provide information on die temperatures, feed rate or through-
put, screw speed, torque and drive amperage, melt pressure, and viscosity [4,5].
Classical process control based on measurements of these parameters is in many cases
not sufficient to explain process variations in material properties and to monitor the
extrudate quality attributes. Non-destructive in-line monitoring equipment such as
UV-vis absorption, photoluminescence, FT-IR, and Raman spectroscopy are useful tools
for product screening and quantitative as well as qualitative analysis of HME formula-
tions [6–10]. Furthermore, the use of spectroscopic methods in manufacturing provides
important information on a molecular level because of the use of superposed informa-
tion about the chemical composition by monitoring the wavelength-dependent absorp-
tion spectra. Wang et al. applied the UV-vis spectroscopy technique to monitor the
CONTACT Namchul Cho
chon7@sch.ac.kr; Tae-Dong Kim
tdkim@hnu.kr
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gmcl.
ß 2019 Taylor & Francis Group, LLC

76
W. T. OH ET AL.
process-induced degradation of poly-L-lactic acid during extrusion [11]. Gilmor et al.
developed an in-line color monitoring system with the fiber-optic reflection probe
inserted into the die of a single-screw extruder [12]. Carneiro et al. determined the resi-
dence time distribution (RTD) along a kneading block via in-line monitoring of the
light emission of a perylene fluorescent tracer in a slit die attached to a single-screw
extruder and at several locations along a corotating twin-screw extruder [13]. Due to
providing information on the mixing history of the melt, fluorescent in-line monitoring
is the one of powerful tools to determine the RTD of a formulation and to measure
accurate melt temperatures. Here, we present synthesis and characterization of an
anthracene derivative (AMA), 9,10-bis(f5-phenyl-[1,1’-biphenyl]-3-ylg)anthracene, as a
fluorescent tracer blended with a polystyrene for HME. Because the anthracene mole-
cules have been utilized for the use of blue host materials in light-emitting diodes appli-
cations, it can be a good candidate for the fluorescent tracers. They are also known that
the 9,10-disubstitution on anthracene improves their photochemical stability [14]. A
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lab-scale microcompounder composed with RheoComp BIM Series has been utilized
and in-line monitored in the extrusion barrel as function of the process settings in
order to evaluate the material behavior.
2. Experimental details
2.1. Materials
All reagents were purchased from commercial sources and solvents were purified by dis-
tillation prior to use. All reaction containers were flame dried under vacuum before use.
2.1.1. 3,5-(diphenyl)bromobenzene
To a solution of 1,3,5-tribromobenzene (12.0 g, 0.030 mol) in 30 mL of dry tetrahydro-
furan (THF) was added 0.1 g of bis(triphenylphosphine)palladium (II) chloride under
nitrogen. After the solution was purged with nitrogen for 5 minutes, a solution of phe-
nylmagnesium bromide, which was freshly prepared from 12.6 g (0.080 mol) of bromo-
benzene in 15 mL of dry THF with 2.0 g of magnesium in 10 mL of dry THF, was
added through an addition funnel at room temperature. The reaction mixture was
stirred overnight. Then it was quenched by slowly adding 15 mL of 0.5 N HCl with stir-
ring. The solvents were removed via a rotary evaporator. The residue was dissolved in
hexane and washed with 0.1 M HCl followed by water. After removal of solvents, crude
residues were purified chromatography on silica gel using hexane as an eluent. After
drying, 3.6 g of pure 3,5-(diphenyl)bromobenzene was collected, yielding 30.0%. 1H
NMR (CDCl3, ppm): d ¼ 7.71 (s, 3H), 7.60 (d, 4H), 7.45 (t, 4H), 7.37 (t, 2H).
2.1.2. 9,10-bis(f5-phenyl-[1,1’-biphenyl]-3-ylg)anthracene (AMA)
A solution of 3,5-(diphenyl)bromobenzene (5.0 g, 0.016 mol) in 50 mL of THF was
cooled to ꢀ78 ꢁC under nitrogen, and t-BuLi (1.7 M in pentane, 11.8 mL, 0.020 mol)
was added dropwise during 10 minutes. After 30 minutes, B(OMe)3 (2.0 g, 0.019 mol)
was added, and the mixture was stirred at ꢀ78 ꢁC for 30 minutes and then at room tem-
perature for 3 hours. The mixture was poured into 2 N HCl solution and stirred for

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
77
overnight to produce a solid. The resulting white precipitate was dried to give a 3.5 g of
3,5-(diphenyl)phenylboronic acid. Then, 3,5-(diphenyl)phenylboronic acid (3.5 g,
0.013 mol) and 9,10-dibromoanthracene (2.0 g, 0.006 mmol) were dissolved in 50 mL of
THF and 40 mL of 2M aqueous potassium carbonate. After the reaction mixture was
degassed four times, 0.5 g of tetrakis(triphenylphosphine)palladium was added and vig-
orously refluxed under flowing nitrogen for 48 hours. When the reaction mixture was
cooled down to room temperature, it was poured into 100 mL of methanol and deion-
ized water (9:1). After the crude product was purified by flash chromatography with
hexane/methylene chloride (5:1), 1.3 g of 9,10-bis(f5-phenyl-[1,10-biphenyl]-3-
1
ylg)anthracene was obtained (yield: 56%). H NMR (CDCl3, ppm): d ¼ 8.03 (s, 2H),
7.85 (d, 4H), 7.78-7.72 (m, 12H), 7.51-7.43 (m, 12H), 7.35 (m, 4H). EIþ -Mass: 635,
Anal. calcd for C50H34: C 94.6, H 5.40; found: C 94.76, H 5.27%.
2.2. Characterization
1H NMR spectra (300 MHz) were taken on a Varian 300 spectrometer. UV-vis spectra
were obtained on a Perkin-Elmer spectrophotometer. Elemental analyses were per-
formed on a Vario EL Elemental Analysis Instrument (Elementar Co.). Differential
scanning calorimetry (DSC) was performed on a TA instruments Q50 at a ramping rate
of 10 ꢁC/min. Visualization experiment with a batch internal mixer for microcom-
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pounding was carried out by RheoComp BIM Series. Scanning electron microscopy
(SEM) was used to characterize the morphology of the extruded polymer mixer.
3. Results and discussion
The structure and synthetic route of AMA, which is a fluorescent tracer for polymer
extrusion are shown in Scheme 1. 3,5-(diphenyl)bromobenzene is synthesized from
1,3,5-tribromobenzene by reacting with a Grignard reagent of phenylmagnesium brom-
ide. 3,5-(diphenyl)phenylboronic acid, then, is obtained from lithiated 3,5-(diphenyl)-
bromobenzene and trimethylborate. The Suzuki coupling reaction was employed for the
Scheme 1. Synthetic routes of a fluorescent tracer, AMA

78
W. T. OH ET AL.
AMA
Tm: 231oC
200
10oC/min in air
50
100
150
250
Temperature (oC)
Figure 1. DSC curve for AMA
Figure 2. (a) UV-vis absorption spectra of AMA (1.0wt%) blended with PS in thin films (b) the
absorption intensity (401 nm) changes of the film as a function of time annealed at 170 ꢁC in air

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
79
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Figure 3. In-line monitoring in the extrusion barrel composed with RheoComp BIM Series with a
function of the time versus torque power at 180 ꢁC.
synthesis of AMA between 9,10-dibromoanthracene and 3,5-(diphenyl)phenylboronic
1
acid. The resulting intermediates and AMA were characterized by H NMR, UV-vis
absorption spectroscopy, HR-MS, and EA analysis.
The AMA is soluble in common organic solvents such as acetone, ethyl acetate, tetra-
hydrofuran, toluene, and chlorinated solvents due to the bulky phenyl groups. For an
example, measured quantitative solubility of AMA in chlorobenzene solvent at 25 ꢁC
was found to be 36 mg/mL. The thermal property of AMA was determined by DSC in
air atmosphere at 10 ꢁC/min of heating rate. Upon heating, one endothermic peak at
231 ꢁC indicating the transition to the isotropic melt was observed (Figure 1). It is gen-
erally known that anthracene molecules undergo a reaction with oxygen when they
exposed to the air at high temperature to give endoperoxides. The endoperoxides have
a bridge structure with an oxygen molecule, which bonds to anthracene at the C-9, C-
10 positions. Therefore, the 9,10-disubstituted anthracene derivatives can provide
improved photochemical stability by protecting these active core sites from oxygen.
The oxydation properties have been investigated by UV-vis absorption spectra
recorded at regular intervals enabling a determination of absorption-time profiles. The
absorption spectra of a thin film for the blend of 1.0wt% of AMA in polystyrene (PS)
are shown in Figure 2(a). Before heating, the film has absorption at 359, 378, and
401 nm corresponding to the intrinsic absorption of anthracene molecules. There is
slightly reduced absorption intensity remained over 95% after annealing at 170 ꢁC in air
condition for 300 sec (Figure 2(b)). These results indicate that AMA has remarkable
thermal and chemical stability even in atmospheric air condition.

80
W. T. OH ET AL.
Figure 4. SEM images of AMA/PS composites mixed for (a) 300 and (b) 600 seconds.
The melt mixing has been performed in a lab-scale microcompounder composed
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with RheoComp BIM Series. The optimized amount of AMA was added in 1.0% by
weight in the mixing batch at 100 ꢁC. Then, the processing temperature was increased
to 180 ꢁC and kept at that temperature to ensure proper viscosity for the mixing while
at the same time minimizing degradation of both the AMA and PS. The rotational
screw speed was set at 100 rpm. Figure 3 shows in-line monitoring in the extrusion bar-
rel as function of the process settings. The initial toque was increased to ꢂ180 Nm due
to high viscosity of the mixture during rising temperature. The toque power started to
rapidly decrease at 100 seconds. As shown in the inserted picture at 350 seconds, there
is still remained fluorescent tracers especially in the barrel inlet. However, we could not
observe these agglomerated tracers after 600 seconds.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
81
Figure 4 shows the SEM micrographs of AMA/PS composites obtained by two mixing
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times from the RheoComp BIM extruder. The surface morphology of the sample col-
lected after 5 min was found to be inhomogeneous which the AMA was quite agglomer-
ated and not well dispersed in PS matrix. In Figure 4(a) it is clearly indicated that
phase separation between AMA and PS occurred in circled areas. However, the AMA
aggregates were completely disappeared after 10 min of mixing. (Figure 4(b)).
4. Conclusion
We have successfully developed a fluorescent tracer, AMA, for predicting the HME
processing characteristics of a polystyrene in a lab-scale microcompounder composed
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with RheoComp BIM Series. A blend of polystyrene and AMA was spin-coated on a
glass substrate to investigate oxidation stability confirmed by UV measurement. We
have found that the AMA has remarkable thermal and chemical stability in atmospheric
air condition proper to use HME. By using microcompounder, the polymer blend with
the AMA was mixed and it was visually indicated by fluorescent images during the
material process. We have observed that the mixture has well dispersed after being last
for 600 seconds at 180 ꢁC.
Acknowledgement
This work was supported by University Research Program in Hannam University (2019) and the
Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of
Trade, Industry & Energy (MOTIE) of Republic of Korea (20184030202130).
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