Pyrolysis is an environmentally friendly method, which is often used for the recycling of the plastics included in waste electric and electronic equipment (WEEE); since secondary valuable materials can be produced. Brominated flame retardants (BFRs) are usually added into these plastics to reduce their flammability; but they are toxic substances. The aim of this work is to examine the thermal behaviour and the products obtained after pyrolysis of polymer blends that consist of acrylonitrile-butadiene-styrene (ABS), high-impact polystyrene (HIPS), polycarbonate (PC) and polypropylene (PP) with composition that simulates real WEEE; in the absence and presence of a common BFR, tetrabromobisphenol A (TBBPA), in order to investigate its effect on pyrolysis products. Blends were prepared via the solvent casting method and the melt-mixing in an extruder; it was revealed that the latter method may be a better choice for blends preparation, since it didn’t affect the products obtained. The chemical structure of each polymeric blend was identified by Fourier Transform Infrared spectroscopy (FTIR). Thermal degradation of the blends was evaluated by thermogravimetric (TG) experiments performed using a thermal analyser (TGA) and a pyrolyser for evolved gas analysis (EGA). It was observed that blends had a similar behaviour during their thermal degradation; and in most cases, they followed a one-step mechanism. Pyrolysis products were identified by the pyrolyser combined with a Gas Chromatographer/Mass Spectrometer (GC/MS); and comprised various useful compounds, such as monomers, aromatic hydrocarbons, phenolic compounds, etc. that could be used as chemical feedstock. Furthermore, it was found that TBBPA affected products’ distribution by enhancing the formation of phenolic compounds and on the other hand by resulting in brominated compounds, such as dibromophenol.
Research Article
Effect of brominated flame retardant on the pyrolysis products of polymers originating in WEEE
https://doi.org/10.21203/rs.3.rs-468383/v1
This work is licensed under a CC BY 4.0 License
Journal Publication
published 26 Jul, 2021
Read the published version in Environmental Science and Pollution Research →
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WEEE
chemical recycling
pyrolysis
brominated flame retardant
TBBPA
polymer blends
The rapid economic and technological advances along with the shorter and shorter products’ lifespan have led to an increase in the production and consumption of Electric and Electronic Equipment (EEE) and so, in huge amounts of end-of-life electronic devices (Grause et al. 2015). The main difficulty as regards the recycling of Waste Electric and Electronic Equipment (WEEE) is its inhomogeneous composition; since WEEE consists of various materials, including, metals, glass and plastics that may be reused. Plastics represent a big percentage (~ 20–30%) of WEEE and include many, different types of polymers, such as acrylonitrile-butadiene-styrene (ABS), high-impact polystyrene (HIPS), polycarbonate (PC), polypropylene (PP), etc. as well as blends of them (Ma et al. 2016; Siddiqui et al. 2019). Another important obstacle in WEEE’s recycling is the fact that plastics found in WEEE, more often than not comprise toxic additives, such as brominated flame retardants (BFRs) (Ma et al. 2016). BFRs are added into plastics in order to reduce their flammability. Among them TBBPA is the most widely used flame retardant in plastics of the electronic industry. However, brominated plastics require safe handling in order to avoid environmental contamination (Charitopoulou et al. 2020).
Until now large amounts of WEEE end up in landfilling, which causes serious health and environmental issues (Anuar Sharuddin et al. 2016). In order to eliminate landfilling, research has focused on recycling methods, which are primary recycling, energy recovery, mechanical or secondary recycling and chemical recycling. Among these techniques, chemical recycling seems to have more advantages that limit the applicability of the other mentioned techniques, and result in its selection, as an environmentally friendly method, by many researchers (Siddiqui et al. 2019). Pyrolysis is a thermo-chemical method in which monomers can be recovered and secondary valuable chemicals can be used as fuels or chemical feedstock for the production of new products (Achilias et al. 2012; Ma et al. 2016). It takes place in an inert atmosphere, high temperatures (300–900°C) and in the absence or presence of catalysts. During pyrolysis, plastic waste is converted into liquids, gases, and solid residues (chars) (Miandad et al. 2016; Sahin and Kirim 2018). It should be highlighted that pyrolysis enables material and energy recovery from polymer waste, since only ~ 10% of the energy content of plastic waste is used in order to convert scrap into valuable hydrocarbon products (Nnorom and Osibanjo 2008; Liu et al. 2016). As regards the quality and distribution of the derived pyrolysis products, they are affected by many parameters, including pyrolysis temperature, residence time, heating rate, operating pressure, the presence of catalysts, etc. (Charitopoulou et al. 2020).
Due to pyrolysis great importance, research has focused on pyrolysis of polymers, blends or real plastics from WEEE, with the aim of finding the appropriate experimental conditions; while enhancing the formation of valuable products and eliminating the formation of undesirable ones, such as brominated compounds, that can be formed during pyrolysis (Hall and Williams 2006; Acomb et al. 2013; Caballero et al. 2016; Dias et al. 2017). For instance, Kowalska et al. (2006) applied thermogravimetric analysis (TG) on two different samples originating from WEEE (a mixture of three types of printed circuit boards and a mixture of electronic junctions with metal wires) so as to determine their appropriate degradation conditions. They found, by X-ray fluorescence measurements, that brominated flame retardant was present in the first sample, whereas chlorinated flame retardant might be present in the second one; also, the hydrocarbons formed during pyrolysis might be used as fuel. Other studies investigated printed circuit boards, mobile phones and other samples coming from WEEE by applying pyrolysis at 500°C (de Marco et al. 2008; Molto et al. 2009). In the latter work they found, by X-ray Fluorescence, that bromine was present in the samples; and after pyrolysis, some brominated compounds, such as bromophenols and dibromophenols were produced (Molto et al. 2009).
This work investigated pyrolysis of polymer blends that consisted of ABS, HIPS, PC and PP; with composition that simulates their composition in real WEEE. Firstly, attention was given on two different methods used for blends’ preparation and their effect on the derived pyrolysis products. The methods applied were the solvent casting method and the melt-mixing in an extruder. The main goal of this research was to evaluate the effect of tetrabromobisphenol A (TBBPA), the most common BFR used in WEEE, on products’ distribution, since more often than not WEEE comprises BFRs. So, blends were also prepared in the presence of TBBPA, applying the latter method that was found to be more beneficial. Thermal degradation of the blends was investigated using a thermal analyser (TGA) and a pyrolyser for evolved gas analysis (EGA). Pyrolysis was held at the maximum degradation temperature that was received from EGA analysis, for each blend. The composition of pyrolysis products was identified using a pyrolyser combined with a Gas Chromatography/ Mass Spectrometry (GC/MS) chromatographer.
2.1 Materials
The polymers used for the experiments were commercially available: ABS [(C15H17N)n, FW = 211.3, batch# 01519EB, melt index: 6 g/10 min], HIPS [(C8H8)x∙(C4H6)z, CAS 9003-55-8, lot# 02122CEV, melt index: 6 g/10 min, butadiene content 4%], PC (C15H16O2, CAS 25037-45-0, lot# 07624KHV, melt index: 7 g/10 min) and PP ([CH2CH(CH3)]n, CAS 9003-07-0, batch# 04227KC) supplied by Sigma-Aldrich (USA). TBBPA (3, 3′, 5, 5′-Tetrabromobisphenol A, CAS 79-94-7) was also purchased from Sigma-Aldrich (USA). All polymers’ pellets were ground using a mill Arthur H. Thomas Co., to reduce particle size (~ 0.2 mm) and enable the surface augmentation for the pyrolysis experiments.
2.2 Blends’ Preparation
As mentioned in the introduction, there were prepared some polymeric blends, using two different methods the solvent casting method and the melt-mixing in an extruder. It should be underlined that the polymers’ percentages were based on polymers’ percentages in real WEEE (Yang et al. 2013). TBBPA’s percentage was also based on literature data (Wäger et al. 2012; Ortuño et al. 2014) where it is referred that TBBPA in plastics in WEEE varies between 0.1–1 %.
In case of the solvent casting method, the appropriate amounts of polymers were dissolved in chlorobenzene (C6H5Cl, MW = 112.56) at ~ 131.6°C (boiling point) and were left for ~ 5 h in a reflux apparatus. Then, the solution was inserted into an oven (Melag) which was set at ~ 60°C, in order to let the solvent evaporate. Finally, the blend was received in the form of flakes. This blend was named as ‘blend’ and consisted of 46% ABS, 39% HIPS and 15% PC.
In case of the melt-mixing method in an extruder, the appropriate amounts of polymers were inserted into a twin-screw extruder (Thermo Scientific HAAKE MiniLab) at 210°C and 30 rpm. The extrudates were further processed into thin films by hot pressing at 200°C. In this case there were prepared 6 blends: ‘sample 4’ that consisted of 46% ABS, 39% HIPS and 15% PC, ‘sample 5’ that consisted of 46% ABS, 39% HIPS, 15% PC and 0.9% TBBPA, ‘sample 6’ that consisted of 41% ABS, 34% HIPS, 14% PC and 11% PP, ‘sample 7’ that consisted of 41% ABS, 34% HIPS, 14% PC, 11% PP and 0.9% TBBPA, ‘sample 8’ that consisted of 46% ABS, 39% HIPS, 15% PC and 9% TBBPA and ‘sample 9’ that consisted of 41% ABS, 34% HIPS, 14% PC, 11% PP and 9% TBBPA (Table 1). The last two blends with the higher percentage of TBBPA were prepared in order to ensure better accuracy in our results.
| Sample | Preparation method | ABS | HIPS | PC | PP | TBBPA* |
|---|---|---|---|---|---|---|
| blend | solution casting | 46 | 39 | 15 | - | - |
| sample 4 | melt mixing | 46 | 39 | 15 | - | - |
| sample 5 | melt mixing | 46 | 39 | 15 | - | 0.9 |
| sample 6 | melt mixing | 41 | 34 | 14 | 11 | - |
| sample 7 | melt mixing | 41 | 34 | 14 | 11 | 0.9 |
| sample 8 | melt mixing | 46 | 39 | 15 | - | 9.0 |
| sample 9 | melt mixing | 41 | 34 | 14 | 11 | 9.0 |
| * Amount relative to the whole polymer blend | ||||||
2.3 Fourier Transform Infrared Spectroscopy (FTIR)
The chemical structure of the polymer blends was confirmed by recording their IR spectra. FTIR analysis was conducted using a FTIR spectrometer, Spectrum One, from Perkin Elmer accompanied by the analogous software. All spectra were received within the range of 4000 − 600 cm− 1. The resolution of the equipment was 4 cm− 1; and a total of 16 scans per spectrum was applied.
2.4 Thermogravimetric analysis (TGA)
Thermogravimetric (TG) measurements were performed on a Pyris 1 TGA thermal analyzer (Perkin Elmer). Each sample weighted < 8 mg and was placed in a platinum (Pt) sample-pan. Specimens were heated from 40 to 700°C in nitrogen (99.9%) atmosphere under a 20 mL/min constant flow. The heating rate employed was 20°C/min for each experiment. Sample mass was plotted and recorded versus temperature continuously. The thermograms were treated using the Pyris Manager Software that was connected with the instrument. The sample-pan contained black residue traces when measurement was completed.
2.5 Evolved Gas Analysis (EGA) and Single Shot Analysis
EGA and Single Shot Analysis were carried out on a Pyrolyser (EGA/PY-3030D Frontier Laboratories) and in both methods the purge gas was He. The sample’s mass in both cases was ~ 1 mg. EGA was applied in order to obtain information about the decomposition temperature range of each blend. During EGA there was used a metal capillary tube and samples were heated in the range of 100–700°C with a rate of 20°C/min, under satisfactory vacuum.
Single Shot Analysis was applied for the determination of pyrolysis products, after pyrolysis at a specific temperature that was chosen for each sample. During it there was used an Ultra Alloy 5% diphenyl-95% dimethyl polysiloxane capillary and the Pyrolyser (EGA/PY-3030D) was coupled with Gas Chromatographer/Mass Spectrometer (Py-GC/MS) (QP-2010 Ultra Plus, Shimadzu, Japan). In this case it took place flash pyrolysis (0.5 min) at the maximum degradation temperature received from EGA; and in almost each case the temperature program lasted 40 min. The detailed method parameters that were finally applied after some optimization experiments are presented here. The injection temperature was 300°C and the column oven was held initially at 50°C for 1 min, then ramped to 300°C, with a heating rate of 10°C/min; and was held there for 14 min. In case of PP the column oven program was modified a little, in order to last more, since products continued to form after the total time of 40min. The chromatographs received, after each experiment, were subjected to interpretation through Shimadzu post-run software (NIST 17 Library). During post-run analysis only clear, intensive peaks were taken into account to ensure safe conclusions. Apart from applying the SCAN mode in the settings before pyrolysis, so as to scan the whole spectrum; selected ion monitoring (SIM) mode was also applied with the aim of targeting specific ions for the determination of some possible brominated compounds formed in order to indicate their presence according to the NIST 17 Library.
2.6 X-ray Fluorescence (XRF)
With a view to ensuring that bromine (from TBBPA) was present in the whole mass of our samples, X-ray Fluorescence (XRF) was also applied. XRF analysis was carried out by a S4-Pioneer (Bruker-AMS, Deutschland) wavelength dispersive spectrometer at the Scanning Electron Microscopy Laboratory of Aristotle University of Thessaloniki. Films of all blends were cut into small parts appropriate for the measurements.
3.1 Bromine content
The bromine content of all blends prepared by the melt-mixing method and measured via X-ray Fluorescence, is presented in Table 2. As observed, bromine was indeed present in all ‘brominated’ blends prepared via the extruder; in order to assure the repeatability of the blend preparation, random samples, from many, different sample-films were analysed and the mean value is presented in the Table. All values of weight percentages for each blend examined were very close, something that may be indicative of the fact that the blends were homogeneous enough, since the bromine content was almost the same in all samples of each blend examined.
|
Blend’s name |
wt % Br measured |
|---|---|
|
sample 4 |
0 |
|
sample 5 |
0.562 |
|
sample 6 |
0 |
|
sample 7 |
0.506 |
|
sample 8 |
5.528 |
|
sample 9 |
6.026 |
3.2 FTIR measurements
From FTIR measurements the polymers that were present in each blend were confirmed; and four representative spectra are presented here in Fig. 1, as an example. It can be noticed that blends retain characteristics of styrenics (including ABS and HIPS) and polyesters, such as PC. The former observation is based on the bands at 3000-3100cm− 1 (vC−H), ~ 2236 cm− 1 (vC−N) which is due to acrylonitrile units in ABS, ~ 1600 cm− 1 (vC=C), ~ 1492 cm− 1 and ~ 1453 cm− 1 (due to the aromatic ring stretching vibrations), ~ 754 cm− 1 and ~ 703 cm− 1 (due to the styrene units in HIPS). The latter observation, about PC, can be based on the bands at ~ 1770 cm− 1 (vC=O), ~ 1084 cm− 1 and ~ 1011 cm− 1 (due to the para aryloxy group) (Achilias et al. 2009; Rosi et al. 2018). TBBPA could not be identified by FTIR, because of its presence in such small amounts.
3.3 Thermal degradation via TG and EGA
For all blends tested TG and DTG curves as well as EGA curves were received so as to obtain important information, such as the degradation steps, the initial, maximum and final degradation temperature and the maximum sample loss (only from TG and DTG). Firstly, there is presented the thermal degradation of all pure polymers: ABS, HIPS, PC and PP in order to compare their degradation with that of the blends. In Figs. 2a and b there are presented the TG and DTG curves for the four mentioned polymers.
From Fig. 2 it is obvious that the thermal degradation of ABS and HIPS is quite similar since their degradation begins and ends at very close temperatures. Specifically, ABS completes its degradation at Tfin = 515°C (residual mass ~ 2.3%) and HIPS at Tfin = 509°C (residual mass ~ 1.1%). PP’s degradation starts at a higher temperature than that of ABS and HIPS; but it is completed at a very close temperature (Tfin = 499°C and residual mass ~ 3.2%). On the other hand, PC’s decomposition starts and ends (Tfin = 664°C, residual mass ~ 23%) at higher temperatures showing greater heat endurance, due to the aromatic rings in the chain backbone. The fact that its residual mass is that much may be attributed to the char, which is formed from the aromatic parts (Vouvoudi et al. 2017). According to the DTG curves (2b), the maximum degradation of HIPS, PP and PC follows a one-step mechanism and their Tmax are 449, 482 and 545°C respectively; whereas in case of ABS there are two maximum peaks corresponding to 448 and 461°C.
All these temperature results were confirmed from EGA analysis with only small temperature differences (for instance, Tmax = 442°C for HIPS and 530°C for PC) that are reasonable and may be attributed to to the different principles of each method; in TGA there are recorded the mass losses versus temperature, whereas in EGA the relative intensity (%) versus temperature. As a result, these different, function principles governing the two techniques lead to different sensitivity.
As for the thermal degradation of the blends, in Figs. 3a and b there are presented the TG and EGA curves obtained for all of them.
From Figs. 3a and b it can be outlined that the thermal degradation of the different blends is quite similar and seems to follow a one-step mechanism. The maximum mass loss, occurs at temperatures higher than 400°C. If we compare ‘blend’ (solvent casting method) with ‘sample 4’ (melt-mixing in an extruder), it is noticeable that the different preparation method doesn’t affect the degradation behaviour of the blends; since their Tmax are ~ 441 and ~ 437°C respectively. As regards the effect of the BFR (TBBPA) on the Tmax, it seems that its presence in such small amounts doesn’t have an impact on the degradation behaviour of the blends, since Tmax remains almost the same in cases of ‘sample 4’ (when TBBPA was absent), ‘sample 5’ (~ 0.9% TBBPA) and ‘sample 8’ (~ 9% TBBPA).
In Fig. 4 there is presented the EGA curve received for TBBPA. According to literature, TBBPA starts its thermal degradation at temperatures higher than 200°C; since although its degradation begins from lower temperatures (~ 185°C) it becomes significant only at T > 230°C (Marsanich et al. 2004; Altarawneh et al. 2019). Its degradation occurs at two steps – stages, with the main degradation taking place in the range of ~ 275–345°C, depending on the heating rate applied (M. Al-Harahsheh et al. 2018); for instance, Luda et al. 2003, found that for a heating rate of 10°C/min the first stage ranged from 200–290°C (Luda et al. 2003). The second stage with a significantly smaller peak occurs at higher temperatures (T > 350°C), when the heating rate is 10°C/min (M. Al-Harahsheh et al. 2018). Generally, during the first stage most of the sample’s mass is consumed (Luda et al. 2003; Altarawneh et al. 2019). Figure 4 is in accordance with the mentioned literature data and shows that TBBPA’s main degradation starts at lower temperatures than the blends (T < 200°C), reaches the maximum loss at Tmax = 273°C and is completed at T < 400°C (Tfin ~367°C). The second and extremely smaller peak (which is almost invisible in Fig. 4) appears at higher temperatures 400 < T < 500°C.
Pyrolysis of each polymer, blend or BFR was held at the maximum degradation temperature that was received from EGA analysis, which was in accordance with Tmax received from TGA experiments. So, in Table 3 there are presented the Tmax for all samples, in which flash pyrolysis took place.
|
Sample examined |
Tmax (oC) from EGA |
|---|---|
|
ABS |
428 |
|
HIPS |
442 |
|
PC |
530 |
|
PP |
482 |
|
TBBPA |
273 |
|
blend |
441 |
|
sample 4 |
437 |
|
sample 5 |
437 |
|
sample 6 |
440 |
|
sample 7 |
440 |
|
sample 8 |
437 |
|
sample 9 |
433 |
3.4 Pyrolysis product distribution via Single Shot Analysis
In this unit there are presented the GC/MS chromatographs received after flash pyrolysis (0.5 min) at Tmax firstly, for all polymers and TBBPA, for comparison reasons and then for the tested blends (Figs. 5a-e and 6a-e respectively); along with the possible compounds formed during pyrolysis (Tables 4–13).
From the chromatographs above, it can be noticed that the dominant – higher peaks were received in the range of ~ 3 to ~ 25 min, with the exception of PP; whereas before and after that range only some peaks of lower intensity were received. Specifically, during the last 5 to 10 min no peaks were obtained, which is indicative of the fact that no other products could be formed after the retention time of 30–35 min; with the exception of PP, as mentioned previously, where products continued to form after the first 40min.
Comparing the chromatograph of ‘blend’ with that of ‘sample 4’, one could say that they are almost the same. But if they are compared with the chromatograph of ‘sample 8’, it can be noticed that the main differences are the peaks’ intensity and the number of the peaks formed; since in case of ‘sample 8’ the relative intensity of the peaks is higher and the chromatograph is denser due to the fact that more peaks are visible now. The same trend was observed after drawing a comparison between ‘sample 6’ and ‘sample 9’; where again in the latter case more peaks were formed and peaks’ intensity became higher.
|
Peak |
Retention Time |
Name |
Possibility (%) |
|---|---|---|---|
|
1 |
1.185 |
Hydrazine |
82 |
|
2 |
1.658 |
Propenenitrile (or Acrylonitrile) |
94 |
|
3 |
3.566 |
Styrene |
86 |
|
4 |
4.739 |
alpha-methylstyrene |
86 |
|
5 |
6.014 |
2-methylene-pentanedinitrile |
95 |
|
6 |
9.777 |
Benzenebutanenitrile |
94 |
|
7 |
10.834 |
3-Phenyl-2-pentenenitrile |
84 |
|
8 |
13.550 |
1,3-Diphenylpropane |
77 |
|
9 |
14.332 |
Cyclohexane, 1,3,5-triphenyl- |
80 |
|
10 |
15.390 |
1,4-diphenyl-2-butene |
78 |
|
11 |
15.923 |
2-Propen-1-amine, N-(phenylmethylene)- |
78 |
|
12 |
16.131 |
2-Phenyl-1-pentene |
77 |
|
13 |
18.360 |
1,3-Diphenylpropane |
90 |
|
14 |
18.784 |
Hexane-3,4-dicarboisonitrile, 3,4-diphenyl- |
78 |
|
15 |
19.058 |
Tetracyclo[5.2.1.0(2,6).0(3,5)]non-8-ene, 4-methyl-4-phenyl-, exo- |
74 |
|
16 |
20.624 |
Cyclopentane, 1-phenyl-3-phenylmethylene- |
73 |
|
17 |
21.160 |
Benzenemethanamine, N-(phenylmethylene)- |
70 |
|
18 |
22.571 |
2,6-Diphenyl-1,6-heptadiene |
80 |
|
Peak |
Retention Time |
Name |
Possibility (%) |
|---|---|---|---|
|
1 |
1.429 |
1,3-Butadiene |
96 |
|
2 |
2.802 |
Cyclohexene, 4-ethenyl- |
96 |
|
3 |
3.648 |
1,3,5,7-Cyclooctatetraene |
86 |
|
4 |
13.580 |
1,3-Diphenylpropane |
96 |
|
5 |
14.450 |
1,2,3,4-Tetrahydro-2-phenylnaphthalene |
76 |
|
6 |
15.214 |
1,3-Diphenyl-1-butene |
91 |
|
7 |
15.436 |
Benzene, 1,1'-(1-butene-1,4-diyl)bis-, (Z)- |
94 |
|
8 |
16.163 |
2,5-Diphenyl-1,5-hexadiene |
97 |
|
9 |
17.336 |
1,5-Diphenyl-1,5-hexadiene |
90 |
|
10 |
21.370 |
Cyclohexane, 1,3,5-triphenyl- |
67 |
|
11 |
22.117 |
[3-(2-Cyclopenten-1-yl)-2-methyl-1-phenyl-1-propenyl]benzene |
82 |
|
12 |
22.523 |
3-Butenylbenzene |
77 |
|
13 |
23.233 |
Benzene, 1,1',1''-[5-methyl-1-pentene-1,3,5-triyl]tris- |
75 |
|
14 |
26.033 |
(2,3-Dibenzyl-4-phenyl-2-butenyl)benzene |
72 |
|
15 |
26.644 |
[3,3-Dimethyl-1-(2-phenylethyl)-4-pentenyl]benzene |
70 |
|
16 |
33.311 |
(2,3-Dibenzyl-4-phenyl-2-butenyl)benzene |
66 |
|
Peak |
Retention Time |
Name |
Possibility (%) |
|---|---|---|---|
|
1 |
1.26 |
Oxygen |
87 |
|
2 |
5.882 |
p-Cresol |
97 |
|
3 |
7.324 |
p-Ethylphenol |
97 |
|
4 |
8.225 |
m-Isopropylphenol |
84 |
|
5 |
9.379 |
p-Isopropenylphenol |
90 |
|
6 |
15.882 |
4-(1-Methyl-1-phenylethyl)phenol |
90 |
|
7 |
16.850 |
4-tert-Butyldiphenyl ether |
77 |
|
8 |
19.058 |
Bisphenol A |
86 |
|
9 |
26.125 |
2,4-Bis-[1-methyl-1-(4-hydroxyphenyl)ethyl]phenol |
62 |
|
Peak |
Retention Time |
Name |
Possibility (%) |
|---|---|---|---|
|
1 |
1.423 |
Propene |
98 |
|
2 |
1.630 |
Cyclohexane |
78 |
|
3 |
3.667 |
1-Undecene |
88 |
|
4 |
4.545 |
4-Undecene, 7-methyl- |
88 |
|
5 |
9.510 |
1-Decene, 2,4-dimethyl- |
91 |
|
6 |
10.820 |
1-Undecene, 7-methyl- |
90 |
|
7 |
11.530 |
(2,4,6-Trimethylcyclohexyl) methanol |
88 |
|
8, 9 |
17.007 - 17.857 |
1-Undecene, 7-methyl- |
90 |
|
10 |
19.142 |
1-Tricosene |
89 |
|
11 |
20.848 |
1,19-Eicosadiene |
86 |
|
12–14 |
29.360 - 30.827 |
1-Dodecanol, 2-octyl- |
90 |
|
15 |
31.780 |
Cyclohexane, 1,1'-(1,2-dimethyl-1,2-ethanediyl)bis- |
86 |
|
16, 17 |
36.578, 37.832 |
1-Decanol, 2-octyl- |
91 |
|
18 |
39.970 |
Cyclohexane, 1,1'-(1,2-dimethyl-1,2-ethanediyl)bis- |
85 |
|
19 |
47.428 |
1-Dodecanol, 2-octyl- |
90 |
|
20 |
49.885 |
4-Tetradecene, 2,3,4-trimethyl- |
84 |
|
21 |
53.543 |
1-Hentetracontanol |
89 |
|
22 |
55.573 |
1-Cyclopentyleicosane |
85 |
|
23–27 |
70.613 - 90.080 |
Cyclohexane, 1,2,3,5-tetraisopropyl- |
85 |
|
28–29 |
90.453 - 91.883 |
1-Hentetracontanol |
85 |
|
30 |
93.565 |
Cyclohexane, 1,2,3,5-tetraisopropyl- |
82 |
|
31–32 |
93.907 - 95.365 |
1-Hentetracontanol |
84 |
|
33 |
97.422 |
Cyclohexane, 1,2,3,5-tetraisopropyl- |
82 |
|
34–37 |
97.917 - 106.525 |
1-Hentetracontanol |
85 |
|
Peak |
Retention Time |
Name |
Possibility (%) |
|---|---|---|---|
|
1 |
6.062 |
4-Bromophenol |
94 |
|
2 |
10.272 |
2,4-Dibromophenol |
93 |
|
3 |
13.463 |
1,3-Diphenylpropane |
70 |
|
4 |
14.087 |
3-Methyl-benzofuran |
69 |
|
5 |
14.280 |
Cyclohexane, 1,3,5-triphenyl- |
82 |
|
6 |
17.567 |
2-Bromo-1-indanone |
73 |
|
7 |
19.006 |
Biphenol A |
92 |
|
8 |
21.182 |
Cyclohexane, 1,3,5-triphenyl- |
90 |
|
9 |
23.572 |
Benzoic acid, 2-hydroxy-3-(phenylmethyl)-, methyl ester |
43 |
|
10 |
25.732–26.259 |
Methyl 4-(4-bromophenyl)benzoate |
48 |
|
11 |
27.148 |
9-Hexadecenoic acid, octadecyl ester, (Z) |
61 |
|
12 |
37.051 |
Tetrapentacontane, 1,54-dibromo- |
83 |
Taking into account the products mentioned in Tables 4–7 it’s worth mentioning that after pyrolysis of all polymers examined there were received their monomers. In case of ABS there was produced styrene and propenenitrile (acrylonitrile), in case of HIPS butadiene, in case of PC Bisphenol A and in case of PP propylene. Pyrolysis of ABS produced benzene derivatives (in the range of C8 – C10) such as styrene and alpha-methylstyrene which are chemicals with high value since they can be used as fuels or chemicals for the production of new products (Brebu et al. 2005) as well as other aromatic hydrocarbons with one or two aromatic rings, such as 1,3-diphenylpropane (styrene dimer). It should be highlighted that styrene is one of the most important monomer building blocks in the production of plastic materials and a-methylstyrene is used as a co-monomer for the production of ABS (Franck and Stadelhofer 1988). Furthermore, there were formed both aliphatic (acrylonitrile and 2-methylene-pentanedinitrile) and aromatic nitrogenated compounds (benzenebutanenitrile and 3-phenyl-2-pentenenitrile). Among them benzenebutanenitrile was formed in larger amounts (higher peak in the chromatograph) and its formation may be owed to the reaction of acrylonitrile and styrene (Brebu et al. 2005; Jung et al. 2012). Thermal degradation of ABS is radical and includes end-chain and random chain scission (Polli et al. 2009).
As regards the products obtained after pyrolysis of HIPS, they were rich in hydrocarbons both aromatic with one, two or three aromatic rings, such as 1,3-diphenylpropane (styrene dimer), cyclohexane, 1,3,5-triphenyl- (styrene trimer) which was in large amounts – the second highest peak; and not aromatic, such as 1,3,5,7-cyclooctatetraene which was the highest peak obtained. These results are in accordance with literature data (Antonakou et al. 2014) and it is worth mentioning that aromatic hydrocarbons are high added value products that can be used as chemical feedstock for the production of new products. Thermal decomposition of HIPS follows the radical chain mechanism which includes: initiation, propagation, transfer and termination. The initiation includes chain scission and the formation of primary and secondary radicals (Hu and Li 2007; Chrissafis et al. 2014). Pyrolysis of PC resulted in the formation of various phenolic compounds, either with one aromatic ring (such as p-cresol, p-ethylphenol, etc.) or with two aromatic rings (such as 4-(1-methyl-1-phenylethyl)phenol and its monomer, bisphenol A), which is in accordance with literature data (Antonakou et al. 2014). It should be mentioned that bisphenol A was obtained in large amounts, since its peak was the highest. Phenols are also valuable chemicals since they can be used for the production of phenolic resins, bisphenol A, etc. (Franck and Stadelhofer 1988). PC’s thermal degradation includes chain scission reactions (Jang and Wilkie 2005).
As for the products obtained after pyrolysis of PP, they were mostly rich in unsaturated aliphatic hydrocarbons, including; alkenes, such as: propene (monomer), 1-undecene (the highest peak obtained), 7-methyl- 4-undecene, 1-tricosene, etc., cycloalkanes, such as: cyclohexane (the second highest peak) and 1,2,3,5-tetraisopropyl-cyclohexane and alkadienes. There were also formed some alcohols, such as 2-octyl-1-dodecanol, 2-octyl-1-decanol, 1-hentetracontanol, etc. These results are in accordance with literature data where it is referred that PP’s degradation mainly leads to the formation of hydrocarbons (Kiran Ciliz et al. 2004; Brebu et al. 2005). PP’s thermal degradation follows the free radical route and includes random chain scission reactions (Kiang et al. 1980; Ahmad et al. 2014).
In case of TBBPA there were produced some brominated phenolic compounds with one or two bromine atoms, such as bromophenol and dibromophenol (both in large amounts, especially dibromophenol - high peak in the chromatograph) as well as other brominated compounds in smaller amounts, such as 1,54-dibromo-tetrapentacontane (brominated hydrocarbon) etc. These results are in accordance with literature data (Marsanich et al. 2004; Ortuño et al. 2014) where again bromophenols were formed. The production of dibromophenol in large amounts may be attributed to the chemical structure of TBBPA which enables scissions between positions 4 or 4’ and the propylene structure (scissions of isopropylidene bridges) (Ortuño et al. 2014; Altarawneh et al. 2014). Apart from brominated compounds there were also formed aromatic compounds with two rings, such as 1,3-diphenylpropane (styrene dimer) and bisphenol A (monomer) or three rings such as 1,3,5-triphenyl-cyclohexane and some partially oxygenated compounds, such as furan derivatives (3-methyl-benzofuran, the highest peak in the chromatograph) and others (benzoic acid, 2-hydroxy-3-(phenylmethyl)-, methyl ester). The formation of these non-brominated compounds may be owed to the fission of aromatic-Br bonds that take place at elevated temperatures (Altarawneh et al. 2014). Thermal degradation of TBBPA is quite complicated since various competing processes and reactions occur. During its thermal degradation evaporation phenomena take place (Marsanich et al. 2004; Altarawneh et al. 2014). Also, a very important step for TBBPA’s decomposition is the previously mentioned fission of isopropylidene bridges (Altarawneh et al. 2014).
|
Peak |
Retention Time |
Name |
Possibility (%) |
|---|---|---|---|
|
1 |
3.570 |
Styrene |
92 |
|
2 |
4.787 |
alpha-methylstyrene |
87 |
|
3 |
9.709 |
Benzenebutanenitrile |
94 |
|
4 |
10.795 |
3-Phenyl-2-pentenenitrile |
84 |
|
5,6 |
11.754, 12.711 |
2-Chlorobiphenyl |
97 |
|
7 |
13.566 |
1,3-Diphenylpropane |
97 |
|
8 |
14.354 |
Cyclohexane, 1,3,5-triphenyl- |
80 |
|
9 |
15.340 |
1,4-Diphenylbutane |
81 |
|
10 |
15.728 |
2-Propen-1-amine, N-(phenylmethylene)- |
78 |
|
11 |
15.946 |
4-(1-Methyl-1-phenylethyl)phenol |
88 |
|
12 |
18.285 |
Cyclohexane, 1,3,5-triphenyl- |
82 |
|
13 |
18.699 |
Hexane-3,4-dicarboisonitrile, 3,4-diphenyl- |
77 |
|
14 |
18.924 |
3-Phenyl-3-cyclohepten-1-ol |
75 |
|
15 |
19.172 |
Biphenol A |
91 |
|
16 |
20.470 |
Benzyl butyl phthalate |
96 |
|
17 |
21.233 |
Cyclohexane, 1,3,5-triphenyl- |
79 |
|
Peak |
Retention Time |
Name |
Possibility (%) |
|---|---|---|---|
|
1 |
1.198 |
Oxygen |
94 |
|
2 |
3.548 |
Styrene |
94 |
|
3 |
4.763 |
alpha-methylstyrene |
90 |
|
4 |
9.708 |
Benzenebutanenitrile |
93 |
|
5 |
10.790 |
3-Phenyl-2-pentenenitrile |
84 |
|
6 |
13.566 |
1,3-Diphenylpropane |
97 |
|
7 |
14.354 |
Cyclohexane, 1,3,5-triphenyl- |
79 |
|
8 |
15.329 |
1,2,3,4,5,8-Hexahydronaphthalene |
77 |
|
9 |
15.711 |
2-propen-1-amine,N-(phenylmethylene) |
78 |
|
10 |
15.945 |
2,6-Diphenyl-1,6-heptadiene |
73 |
|
11 |
18.279 |
Cyclohexane, 1,3,5-triphenyl- |
81 |
|
12 |
18.694 |
Hexane-3,4-dicarboisonitrile, 3,4-diphenyl- |
76 |
|
13 |
18.916 |
3-Phenyl-3-cyclohepten-1-ol |
74 |
|
14 |
19.132 |
Biphenol A |
91 |
|
15 |
20.455 |
Benzyl butyl phthalate |
96 |
|
16 |
21.240 |
Cyclohexane, 1,3,5-triphenyl- |
77 |
|
Peak |
Retention Time |
Name |
Possibility (%) |
|---|---|---|---|
|
1 |
1.236 |
Oxygen |
90 |
|
2 |
2.801 |
2,4-Dimethyl-1-heptene |
93 |
|
3 |
3.422 |
Styrene |
90 |
|
4 |
4.731 |
Phenol |
97 |
|
5 |
8.116 |
p-Isopropylphenol |
96 |
|
6 |
8,988 |
7-Methyl-1-undecene |
91 |
|
7 |
9.281 |
p-Isopropenylphenol |
87 |
|
8 |
9.567 |
Benzenebutanenitrile |
92 |
|
9 |
9.756 |
Phenol, 2,5-dibromo- |
65 |
|
10 |
10.608 |
3-Phenyl-2-pentenenitrile |
83 |
|
11 |
11.774 |
2-Hexyl-1-decanol |
86 |
|
12 |
13.367 |
1,3-Diphenylpropane |
95 |
|
13 |
14.136 |
4-[Benzylamino]benzo-1,2,3-triazine |
79 |
|
14 |
14.561 |
1-Dodecanol, 2-hexyl- |
91 |
|
15 |
15.592 |
2-Propen-1-amine, N-(phenylmethylene)- |
79 |
|
16 |
15.742 |
4-(1-Methyl-1-phenylethyl)phenol |
90 |
|
17 |
16.455 |
2-Octyl-1-dodecanol |
90 |
|
18 |
18.078 |
Cyclohexane, 1,3,5-triphenyl- |
79 |
|
19 |
18.723 |
3-Phenyl-3-cyclohepten-1-ol |
74 |
|
20 |
19.067 |
3,4'-Isopropylidenediphenol |
89 |
|
21 |
20.282 |
Benzyl butyl phthalate |
96 |
|
22 |
21.012 |
Cyclohexane, 1,3,5-triphenyl- |
74 |
|
23 |
21.864 |
1-Propene, 3-(2-cyclopentenyl)-2-methyl-1,1-diphenyl- |
81 |
|
24, 25, 26 |
22.582, 25.537, 28.829 |
1,2,3,5-Tetraisopropylcyclohexane |
84 |
|
Peak |
Retention Time |
Name |
Possibility (%) |
|---|---|---|---|
|
1 |
3.547 |
Styrene |
93 |
|
2 |
4.730 |
alpha-methylstyrene |
92 |
|
3 |
9.705 |
Benzenebutanenitrile |
93 |
|
4 |
10.791 |
3-Phenyl-2-pentenenitrile |
84 |
|
5 |
13.566 |
1,3-Diphenylpropane |
95 |
|
6 |
14.354 |
Cyclohexane, 1,3,5-triphenyl- |
79 |
|
7 |
15.328 |
1,2,3,4,5,8-Hexahydronaphthalene |
77 |
|
8 |
15.702 |
2-Propen-1-amine, N-(phenylmethylene)- |
78 |
|
9 |
15.942 |
2,6-Diphenyl-1,6-heptadiene |
71 |
|
10 |
18.276 |
Cyclohexane, 1,3,5-triphenyl- |
81 |
|
11 |
18.691 |
Hexane-3,4-dicarboisonitrile, 3,4-diphenyl- |
76 |
|
12 |
18.913 |
3-Cyclohepten-1-ol, 3-phenyl- |
75 |
|
13 |
19.148 |
3,4'-Isopropylidenediphenol |
92 |
|
14 |
20.455 |
Benzyl butyl phthalate |
96 |
|
15 |
21.235 |
Cyclohexane, 1,3,5-triphenyl- |
78 |
|
Peak |
Retention Time |
Name |
Possibility (%) |
|---|---|---|---|
|
1 |
3.390 |
Styrene |
90 |
|
2 |
4.665 |
Phenol |
98 |
|
3 |
8.078 |
p-Isopropylphenol |
97 |
|
4 |
8.954 |
7-Methyl-1-undecene |
91 |
|
5 |
9.232 |
p-Isopropenylphenol |
88 |
|
6 |
9.565 |
Benzenebutanenitrile |
93 |
|
7 |
9.698 |
Phenol, 2,5-dibromo- |
84 |
|
8 |
10.581 |
3-Phenyl-2-pentenenitrile |
84 |
|
9 |
13.350 |
1,3-Diphenylpropane |
94 |
|
10 |
14.114 |
4-[Benzylamino]benzo-1,2,3-triazine |
79 |
|
11 |
14.964 |
1,3-Diphenyl-1-butene |
91 |
|
12 |
15.126 |
1,2,3,4,5,8-Hexahydronaphthalene |
71 |
|
13 |
15.552 |
2-Propen-1-amine, N-(phenylmethylene)- |
79 |
|
14 |
15.701 |
4-(1-Methyl-1-phenylethyl)phenol |
82 |
|
15 |
18.052 |
Cyclohexane, 1,3,5-triphenyl- |
80 |
|
16 |
18.449 |
4-Isopropylphenylacetonitrile |
70 |
|
17 |
18.707 |
3-Phenyl-3-cyclohepten-1-ol |
74 |
|
18 |
18.969 |
3,4'-Isopropylidenediphenol |
90 |
|
19 |
20.236 |
Benzyl butyl phthalate |
97 |
|
20 |
21.017 |
Cyclohexane, 1,3,5-triphenyl- |
77 |
|
21 |
21.842 |
1-Propene, 3-(2-cyclopentenyl)-2-methyl-1,1-diphenyl- |
82 |
|
22 |
25.288 |
Cyclohexane, 1,2,3,4,5,6-hexaethyl- |
81 |
The chromatographs and the main products obtained after pyrolysis of ‘sample 5’ and ‘sample 7’ are not presented here since they were exactly the same with those of ‘sample 4’ and ‘sample 6’, respectively. Furthermore, during the post-run analysis of these two samples no brominated compounds could be identified, which may be attributed to the very low bromine content. Therefore, as regards the effect of TBBPA on products’ distribution, there were taken into account only ‘sample 8’ and ‘sample 9’, the blends with the higher percentage of bromine.
From Tables 9–13 it is noticeable that many of the products obtained after pyrolysis of all blends examined are the same (such as styrene, benzenebutanenitrile, etc.) appearing also at almost the same retention times. The non-brominated compounds that were formed are owed to the degradation of the polymers present in the blends. Specifically, all blends show a main peak at ~ 3.5 min that corresponds to styrene, which is a valuable chemical; and was formed because of the degradation of ABS. At ~ 9.7 min there was obtained benzenebutanenitrile, an aromatic nitrogenated compound, which was also formed because of ABS’s degradation. Another important peak at ~ 13.5 min is that of 1,3-diphenylpropane (styrene dimer) which was formed due to pyrolysis of both ABS and HIPS. The formation of 1,3,5-triphenyl- cyclohexane (styrene trimer), may be attributed to the degradation of ABS and HIPS; and TBBPA as well in case of ‘sample 8’ and ‘sample 9’. As mentioned previously these aromatic hydrocarbons are high added value products that can be used as chemical feedstock for the production of new products (Antonakou et al. 2014).
As regards the effect of the different preparation method on the products’ distribution it can be concluded that after pyrolysis of ‘blend’ and ‘sample 4’ almost all products were the same, which is reasonable, since they have the same composition. Nevertheless, the main difference lies on the fact that in case of ‘blend’ there were received two extra peaks (at 11.754 and 12.711 min); where the product was 2-chlorobiphenyl, which isn’t a desirable one. The formation of this chlorinated compound may be owed to traces of solvent that perhaps didn’t evaporate completely during blend’s preparation. So, the melt-mixing method (in an extruder) seems to be more advantageous than the solvent casting method, because the former has no (negative) effect on pyrolysis products.
As for the effect of TBBPA on the products’ distribution, it’s worth mentioning that its presence enhances the formation of phenolic compounds, which are useful products. On the other hand, it leads to the formation of brominated compounds, which are undesirable and need to be removed. Specifically, in case of ‘sample 4’ and ‘sample 6’ (absence of BFR) only one phenolic compound (at ~ 19.1 min) was obtained, bisphenol A (monomer) and 3,4'-isopropylidenediphenol, respectively, due to PC’s degradation; whereas in case of ‘sample 8’ and ‘sample 9’ there were formed more phenolic compounds, such as: p-isopropylphenol, p-isopropenylphenol, 4-(1-methyl-1-phenylethyl)phenol and 3,4'-isopropylidenediphenol. The phenolic compounds formed in the latter cases are owed to PC’s degradation in combination with the presence of TBBPA that according to literature (Hall et al. 2008) enhances their formation. As it is shown in Tables 11 and 13, at ~ 9.7 min there was produced dibromophenol, because of TBBPA’s presence. Dibromophenol’s peak was very low, which is quite expected, considering that TBBPA was added in low percentage, in comparison with the polymers that were abundant in both blends. So, in order to ensure dibromophenol’s presence, SIM analysis was also performed, targeting some specific ions (250, 252, and 254) for its determination; and it was indicated that dibromophenol was indeed formed in both cases. Furthermore, for both ‘sample 8’ and ‘sample 9’ during the SCAN mode it was found that at ~ 6 min, (Bromomethyl)benzene could be obtained with 96% possibility. Nevertheless, its presence was not confirmed when applying the SIM analysis targeting specific ions (39, 63, 65, 91, 170 and 172); so further investigation may be needed.
This paper thoroughly investigated pyrolysis of polymer blends that consisted of four different polymers abundant in WEEE (ABS, HIPS, PC and PP) as well as TBBPA, one of the most common BFR used in WEEE; since their co-existence can simulate real scenarios. Polymers’ presence in blends was confirmed by FTIR analysis. Pyrolysis took place using a TGA apparatus and a pyrolyser (Py-GC/MS) for EGA and flash pyrolysis. In this way important information such as the degradation steps and the maximum degradation temperature were obtained for all blends examined. TG and EGA curves showed that the thermal degradation of blends was quite similar and seemed to follow a one-step mechanism. Flash pyrolysis was held at the maximum degradation temperature and by using the post-run software all derived pyrolysis products were identified. It was found that in all cases tested there were obtained monomers along with high value products (phenols, aromatic HC, etc.) that could be used as fuels or chemical feedstock. This indicates that pyrolysis process can be applied as an environmentally friendly, recycling method for WEEE’s handling.
It was proved that the preparation method didn’t influence the degradation behaviour of the blends; since for instance their Tmax were very close. Nevertheless, as regards its effect on pyrolysis products, it was found that in case of the solvent casting method there were obtained two peaks giving a chlorinated compound (2-chlorobiphenyl), due to incomplete evaporation of chlorobenzene (solvent) during the preparation. According to this observation the melt-mixing method (in an extruder) may be considered as a more advantageous method than the solvent casting, taking into account that during the former method pyrolysis products were not affected.
As for the effect of the BFR (TBBPA) on the Tmax, it was found that its presence in such small amounts had no impact on the degradation behaviour of the blends; Tmax in its absence and presence were very close. However, it was proved that TBBPA’s presence influenced the composition of pyrolysis products, since it favoured the formation of phenolic compounds (which are useful and desirable products); however, it also led to the production of brominated compounds that are undesirable and toxic. Dibromophenol was obtained as the main brominated compound, since its presence was ensured with SIM analysis. On the other hand, more investigation is needed in order to make sure if (bromomethyl)benzene was also formed.
Ethics approval and consent to participate: Not applicable.
Consent for publication: Not applicable.
Competing interests: The authors declare that they have no competing interests.
Availability of data and materials: All data generated or analysed during this study are included in this published article.
Funding: This work was partially funded by the Hellenic Foundation for Research and Innovation under a Ph.D Fellowship grant (Number 853) to M.-A. Charitopoulou.
Author contribution: MAC and DA contributed to the study conception, methodology and design. MAC performed material preparation, data collection and analysis. LP performed the XRF experiments and analyzed the results. Supervision: DSA. MAC wrote the first draft of the manuscript and all authors reviewed and commented on previous versions of the manuscript. All authors read and approved the final version of the manuscript.
Acknowledgments
Achilias DS, Antonakou EV, Koutsokosta E, Lappas AA (2009) Chemical Recycling of Polymers from Waste Electric and Electronic Equipment. Journal of Applied Polymer Science 114:212–221. DOI 10.1002/app.30533
Achilias D, Andriotis L, Koutsidis IA, Louka DA, Nianias NP, Siafaka P, Tsagkalias I, Tsintzou G (2012) Recent Advances in the Chemical Recycling of Polymers (PP, PS, LDPE, HDPE, PVC, PC, Nylon, PMMA) In: Achilias D (ed) Material Recycling - Trends and Perspectives, IntechOpen, London, UK, http://dx.doi.org/10.5772/33457
Acomb JC, Nahil MA, Williams PT (2013) Thermal processing of plastics from waste electrical and electronic equipment for hydrogen production. Journal of Analytical and Applied Pyrolysis 103:320–327. http://dx.doi.org/10.1016/j.jaap.2012.09.014
Ahmad I, Khan MI, Khan H, Ishaq M, Tariq R, Gul K, Ahmad W (2014) Pyrolysis Study of Polypropylene and Polyethylene in to Premium Oil Products. International Journal of Green Energy 12(7):140303064405005. DOI: 10.1080/15435075.2014.880146
Al-Harahsheh M, Aljarrah M, Al-Otoom A, Altarawneh M, Kingman S (2018) Pyrolysis kinetics of tetrabromobisphenol a (TBBPA) and electric arc furnace dust mixtures. Thermochimica Acta 660:61–69
Altarawneh M, Saeed A, Al-Harahsheh M, Dlugogorski BZ (2019) Thermal decomposition of brominated flame retardants (BFRs): Products and mechanisms. Progress in Energy and Combustion Science 70:212–259
Antonakou EV, Kalogiannis KG, Stephanidis SD, Triantafyllidis KS, Lappas AA, Achilias DS (2014) Pyrolysis and catalytic pyrolysis as a recycling method of waste CDs originating from polycarbonate and HIPS. Waste Management 34(12): 2487–2493
Anuar Sharuddin SD, Abnisa F, Wan Daud WMA, Aroua MK (2016) A review on pyrolysis of plastic wastes. Energy Conversion and Management 115:308–326. http://dx.doi.org/10.1016/j.enconman.2016.02.037
Brebu M, Bhaskar T, Murai K, Muto A, Sakata Y, Uddin MdA (2005) Removal of nitrogen, bromine, and chlorine from PP/PE/PS/PVC/ABS-Br pyrolysis liquid products using Fe- and Ca-based catalysts. Polymer Degradation and Stability 87: 225-230
Caballero BM, de Marco I, Adrados A, López-Urionabarrenechea A, Solar J, Gastelu N (2016) Possibilities and limits of pyrolysis for recycling plastic rich waste streams rejected from phones recycling plants. Waste Management 57:226–234.
http://dx.doi.org/10.1016/j.wasman.2016.01.002
Charitopoulou MA, Kalogiannis KG, Lappas AA, Achilias DS (2020) Novel trends in the thermo-chemical recycling of plastics from WEEE containing brominated flame retardants. Environmental Science and Pollution Research https://doi.org/10.1007/s11356-020-09932-5
Chrissafis K, Pavlidou E, Vouvoudi E, Bikiaris D (2014) Decomposition kinetic and mechanism of syndiotactic polystyrenenanocomposites with MWCNTs and nanodiamonds studied by TGA and Py-GC/MS. Thermochimica Acta 583: 15–24
de Marco I, Caballero BM, Chomon MJ, Laresgoiti MF, Torres A, Fernandez G, Arnaiz S (2008) Pyrolysis of electrical and electronic wastes. J. Anal. Appl. Pyrolysis 82:179–183. https://doi.org/10.1016/j.jaap.2008.03.011
Dias P, Javimczik S, Benevit M, Veit H (2017) Recycling WEEE: Polymer characterization and pyrolysis study for waste of crystalline silicon photovoltaic modules. Waste Management 60:716–722. http://dx.doi.org/10.1016/j.wasman.2016.08.036
Franck H-G, Stadelhofer JW (1988) Production and uses of benzene derivatives. In: Franck H-G, Stadelhofer JW (eds) Industrial Aromatic Chemistry, pp. 132–235. Springer, Heidelberg. doi:10.1007/978-3-642-73432-8_5
Grause G, Fonseca JD, Tanaka H, Bhaskar T, Kameda T, Yoshioka T (2015) A novel process for the removal of bromine from styrene polymers containing brominated flame retardant. Polymer Degradation and Stability 112:86-93. http://dx.doi.org/10.1016/j.polymdegradstab.2014.12.017
Hall WJ, Williams PT (2006) Pyrolysis of brominated feedstock plastic in a fluidised bed reactor. J. Anal. Appl. Pyrolysis 77:75–82. https://doi.org/10.1016/j.jaap.2006.01.006
Hall WJ, Miskolczi N, Onwudili J, Williams PT (2008) Thermal Processing of Toxic Flame-Retarded Polymers Using a Waste Fluidized Catalytic Cracker (FCC) Catalyst. Energy & Fuels 22:1691–1697
Hu Y, Li S (2007) The effects of magnesium hydroxide on flash pyrolysis of polystyrene. J. Anal. Appl. Pyrolysis 78:32–39
Jang BN, Wilkie CA (2005) The thermal degradation of bisphenol A polycarbonate in air. Thermochimica Acta 426:73–84
Jung S-H, Kim S-J, Kim J-S (2012) Thermal degradation of acrylonitrile–butadiene–styrene (ABS) containing flame retardants using a fluidized bed reactor: The effects of Ca-based additives on halogen removal. Fuel Processing Technology 96:265–270 doi: 10.1016/j.fuproc.2011.12.039
Kiang JKY, Uden PC, Chien JCW (1980) POLYMER REACTIONS-PART VII: THERMAL PYROLYSIS OF POLYPROPYLENE. Polymer Degradation and Stability 2:113-127
Kiran Ciliz N, Ekinci E, Snape CE (2004) Pyrolysis of virgin and waste polypropylene and its mixtures with waste polyethylene and polystyrene. Waste Management 24:173–181
Kowalska E, Radomska J, Konarski P, Diduszko R, Oszczudlowski J, Opalinska T, Wiech M, Duszyc Z (2006) Thermogravimetric investigation of wastes from electrical and electronic equipment (WEEE). J Therm Anal Calorim 86:137–140. https://doi.org/10.1007/s10973-006-7589-z
Liu W-J, Tian K, Jiang H, Yu H-Q (2016) Lab-scale thermal analysis of electronic waste plastics. J Hazard Mater 310:217–225. https://doi.org/10.1016/j.jhazmat.2016.02.044
Luda MP, Balabanovich AI, Hornung A, Camino G (2003) Thermal Degradation of a Brominated Bisphenol A Derivative. Polym. Adv. Technol. 14:741–748
Ma C, Yu J, Wang B, Song Z, Xiang J, Hu S, Su S, Sun L (2016) Chemical recycling of brominated flame retarded plastics from e-waste for clean fuels production: A review. Renewable and Sustainable Energy Reviews 61:433–450. http://dx.doi.org/10.1016/j.rser.2016.04.020
Marsanich K, Zanelli S, Barontini F, Cozzani V (2004) Evaporation and thermal degradation of tetrabromobisphenol A above the melting point. Thermochimica Acta 421:95–103
Miandad R, Barakat MA, Aburiazaiza AS, Rehan M, Nizami AS (2016) Catalytic pyrolysis of plastic waste: a review. Process Saf Environ Prot 102:822–838. https://doi.org/10.1016/j.psep.2016.06.022
Molto J, Font R, Galvez A, Conesa JA (2009) Pyrolysis and combustion of electronic wastes. J. Anal. Appl. Pyrolysis 84:68–78. http://dx.doi.org/10.1016/j.jaap.2008.10.023
Nnorom IC, Osibanjo O (2008) Sound management of brominated flame retarded (BFR) plastics from electronic wastes: state of the art and options in Nigeria. Resour Conserv Recycl 52:1362–1372. https://doi.org/10.1016/j.resconrec.2008.08.001
Ortuño N, Moltó J, Conesa JA, Font R (2014) Formation of brominated pollutants during the pyrolysis and combustion of tetrabromobisphenol A at different temperatures. Environmental Pollution 191:31-37. https://doi.org/10.1016/j.envpol.2014.04.006
Polli H, Pontes LAM, Araujo AS, Barros JMF, Fernandes Jr VJ (2009) DEGRADATION BEHAVIOR AND KINETIC STUDY OF ABS POLYMER. Journal of Thermal Analysis and Calorimetry 95(1):131–134
Rosi L, Bartoli M, Frediani M (2018) Microwave assisted pyrolysis of halogenated plastics recovered from waste computers. Waste Management 73:511–522
Sahin O, Kirim Y (2018) Material recycling. In: Dincer I (ed) Comprehensive energy systems. Elsevier, pp 1018–1042
Siddiqui MN, Antonakou EV, Redhwi HH, Achilias DS (2019) Kinetic analysis of thermal and catalytic degradation of polymers found in waste electric and electronic equipment. Thermochimica Acta 675:69–76. https://doi.org/10.1016/j.tca.2019.03.001
Vouvoudi EC, Rousi AT, Achilias DS (2017) Thermal degradation characteristics and products obtained after pyrolysis of specific polymers found in Waste Electrical and Electronic Equipment. Front. Environ. Sci. Eng. 11(5):9. DOI 10.1007/s11783-017-0996-5
Wäger PA, Schluep M, Müller E, Gloor R (2012) RoHS regulated substances in mixed plastics from waste electrical and electronic equipment. Environ. Sci. Technol. 46(2):628-635. dx.doi.org/10.1021/es202518n
Yang X, Sun L, Xiang J, Hu S, Su S (2013) Pyrolysis and dehalogenation of plastics from waste electrical and electronic equipment (WEEE): A review. Waste Management 33:462–473. http://dx.doi.org/10.1016/j.wasman.2012.07.025