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Application of New, Synthesized Plasticizers
7 Application of New, Synthesized Plasticizers The properties of plasticized PVC compositions are mainly determined by the properties of the polymer and plasticizer used. In most cases (except for plastisols), the use of suspension polymers with higher molecular weights (e.g., with K 70 constants) and high grain porosity is recommended in such compositions. PVC grains that are homogeneous and demonstrate high porosity ensure better penetration of the plasticizer into the porous structures of the polymer grains, making it possible to absorb more of the plasticizer during the preparation of a blend [1e6]. This helps obtain a dry blend PVC with good technological parameters (proper flowability, pneumatic transport capability, charging of processing equipment). Therefore, when determining the formula of PVC blends, it is advisable to define the properties of the polymer, plasticizer, and auxiliary agents. The processing method and expected properties of the product determine the composition of PVC blends. The basic parameters determining the processing properties of PVC compositions include gelation time and the dynamic stability of the mixture. Gelling of PVC compositions consists in destroying the morphological structure of a polymer (PVC) by means of heat, shear forces, and pressure exerted during processing [7e17]. The gelation time of the processed PVC composition should be strictly determined and adjusted to the processing method and technological parameters of the processing equipment. Mixing and kneading chambers that record changes in torque are used for conducting processing tests of PVC compositions. The gelation time of PVC mixtures is usually determined by plastographic methods (Brabender plastograph, Hakke), which make it possible to directly observe changes in the dynamics of the gelling material [18e20]. Other methods for assessing the degree of gelation of PVC compositions are also used [21e23]. When evaluating the performance of modifiers, plasticizers, and other additives in PVC compositions, the appropriate mixing procedure must be followed. The correct procedure determines the order in which the ingredients are introduced into the mixer, the temperature at the various stages of mixing, and the intensity of mixing [24,25]. The processing
Plasticizers Derived from Post-consumer PET https://doi.org/10.1016/B978-0-323-46200-6.00007-6 Copyright © 2020 Elsevier Inc. All rights reserved.
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conditions are also a decisive factor in the final properties of plasticized products [26e30]. To assess the effectiveness and usefulness of new oligomeric plasticizers based on waste poly(ethylene terephthalate) in PVC processing, a number of PVC compositions were prepared and tested. The results presented below constitute a preliminary assessment of the physicomechanical properties of PVC compositions containing new oligomeric plasticizers based on waste poly(ethylene terephthalate) synthesized on a laboratory scale. The next part concerns comparative tests of PVC compositions using one of the selected plasticizers synthesized on an industrial scale, a monomeric plasticizer, and a commercially available polymeric plasticizer. Suspension poly(vinyl chloride) and new oligomeric plasticizers based on waste poly(ethylene terephthalate) were used in the plasticized PVC compositions. Monomeric bis(2-ethylhexyl) phthalate (DEHP) and the commercially available polymeric H-1 plasticizer (adipic oligoester, Lanxess, Germany) were used in the reference compositions. The plasticized PVC compositions also contained calcium-zinc BP MC 8656-ST (Baerlocher, Germany) as a thermal stabilizer, epoxidized soybean oil (ESO) (Ergoplast ES, Boryszew, Poland), and technical stearic acid (Brenntag, Poland). The characteristics of the polymer used in the PVC compositions are presented below. The PVC suspension Polanvil S-70 (K value ¼ 69.1; apparent bulk density ¼ 0.505 g/cm3; plasticizer absorption ¼ 29 g/100 g; average grain size ¼ 0.13 mm; residual VCM ¼ 0.7 ppm; Mw ¼ 83,600 g/mol, and dispersity ¼ 2.2) by Z.A. Anwil Wloclawek, Poland, was used to prepare plasticized PVC compositions. A fragment of the surface of the grain and cross section of the polymer Polanvil S-70 are presented in Figs. 7.1 and 7.2. The morphological structure of the grain [31e33] has a significant influence on the processing properties of a PVC composition, including the susceptibility of the plasticizer to become absorbed by the polymer. Therefore, porosimetry was used to define the size distribution of the porous structures of the polymer used in plasticized PVC compositions. The volume distribution of PVC grain pores as a function of their diameter is shown in Fig. 7.3. Oligomeric plasticizers synthesized in a reaction of PET degradation using oligoesters containing a selected type of dicarboxylic acid and glycol were used in the PVC blends. The properties of these plasticizers are presented in Chapter 6.
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Figure 7.1 Fragment of Polanvil S-70 grain surfacedan area on the surface without an outer layer with a developed surface.
Figure 7.2 A fragment of PVC Polanvil S-70 grain cross section, visible primary particles.
None of the synthesized plasticizers evaluated in this study contained any commercially available antioxidants (e.g., bisphenol A) commonly used in commercial plasticizers. The tests were carried out using the following research methodology. A Hitachi SU8010 scanning electron microscope (Hitachi, Japan, 2011)
198
Log Differential Intrusion vs Pore size Log Differential Intrusion
Cumulative Intrusion
2.5 1.2
1.0
0.6
1.0 0.4
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Cumulative Intrusion (mL/g)
Log Differential Intrusion (mL/g)
2.0
FROM
0.2
0.0 0.0 100
50
10
5
1
0.5
0.1
0.05
Pore size Diameter (µm)
Figure 7.3 Pore volume distribution as a function of pore diameter for PVC Polanvil S70 grains.
0.01
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0.5
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was used to study the morphology of the surface and interior of the PVC grains. All the samples were sprayed with a 7e8 nm-thick layer of gold. The basic conditions for microscopic observation are type of detector: SE (second electron), accelerating voltage: 2 kV, current: approximately 10 mA, and working distance: 8e9 mm. All the samples (both for cutting and microscopic observation) were glued to a special table using conductive carbon tape. An E-3500 Ion Milling System (Hitachi, Japan, 2011) was used for cross-sectional surface microscopy. The conditions for cutting the samples with an ion cutting machine were as follows: - cutting time: from 10 to 16 h depending on the thickness of the sample, - accelerating voltage: 6 kV, - discharge voltage: 4 kV. The morphological structure of the PVC (Polanvil S-70) was also evaluated using mercury porosimetry using a Micrometrics AutoPore IV 9500 device. The amount of mercury injected into the pores of the previously degassed sample was recorded for subsequent predetermined pressures of up to 400 MPa. The volume and specific surface area of the pores and their size distribution were determined using the method described above. As per the recommendations of ASTM D 2873, according to which the tests were conducted, porous structures with diameters >3100 nm (3.1 mm), corresponding to intergranular spaces, were not considered in the given values of the pores’ specific volume. The thermal stability properties were determined by thermogravimetric analysis (TGA) using a model TGA/SDTA 851e Mettler Toledo device (Switzerland) at a heating rate of 20 C/min from 25 C to 600 C in a nitrogen atmosphere and a flow rate of 60 mL/min. Experiments were performed in an aluminum oxide pan. Volatilization of the plasticizers and the plasticized PVC granulates was performed by the isothermal thermogravimetry method at 180 C for plasticizers, and at 150 C for plasticized PVC granulates, for 60 min under nitrogen with a flow rate of 60 mL/min. From the starting temperature of 25 C to the isothermal testing temperature, the samples were heated at a rate of 50 C/min. After establishing the isothermal conditions (programmed temperature), the weight loss of each sample was taken as the starting value. The deviation of the real temperature value from the programmed temperature value amounted to c.0.25 C.
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Differential scanning calorimetry (DSC) of the samples was performed using a model DSC 822e/700 Mettler Toledo (Switzerland) device. Specimens of 6e8 mg were heated from 70 C to 150 C at a rate of 20 C/min and cooled at the same rate in a nitrogen atmosphere with a flow rate of 60 mL/min. The samples were hermetically closed in aluminum DSC capsules. The glass transition temperature was determined during the second heating run. Data analyses of TGA and DSC results were performed using the STARe v12.10 software supplied by Mettler Toledo. The hardness of the plasticizers was determined in accordance with EN ISO 868 Shore A scale hardness. The water absorption, expressed as wt.%, is determined by weight absorbability and is defined as the ratio of the mass of water absorbed by the sample to that of the sample in a dry state. The test was carried out in accordance with ISO 62 method A. The determination of plasticizer migration from the tested samples was carried out in accordance with EN ISO 177. Polyethylene film was used as the absorbing material. Tensile strength and relative elongation at break were determined according to standard EN ISO 527-2. A Brabender Plast-Corder plastograph was used to evaluate the processing properties of the PVC compositions tested. This was performed using a W30H kneader while maintaining the following constant measurement conditions: kneader temperatured150 C (determination of gelation time); rotor rpmd30/min.; and sample sized26e28 g. During the measurements, the following parameters were recorded: time points when the particular stages of the composition plasticizing process were reached, composition gelation time, dynamic thermal stability value, torques, mass temperature, and energy consumed in the subsequent stages of the PVC melting process. Plasticized PVC compositions containing polymer, plasticizer, and auxiliaries were prepared in a high speed, hot-cold MDF-30 mixer manufactured by Metalchem Toru n. To disperse the individual ingredients of the composition, the charge was mixed in a hot mixer until reaching a temperature of 130 C. To obtain high-quality dry blends, the sequence in which the individual components of a PVC mix are fed is crucial. The polymer with a stabilizing and lubricating composition and ESO were mixed at a temperature of 70 C, following which a plasticizer was introduced. This sequence of plasticizer insertion is justified and necessary because at this temperature, the poly(vinyl chloride) grains are partially swelled; therefore, the relaxed porous structures of the PVC grains are more easily and quickly
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penetrated by the plasticizer. To obtain dry PVC mixtures, the hot mixture was cooled in a cold mixer down to 40 C. The obtained dry blends of PVC were extruded by means of a laboratory extruder to obtain a granulate, which was then pressed. The pressed plates were used to prepared samples for physical and mechanical tests. The plasticized PVC formulations are shown in Table 7.1. The mechanical properties of plasticized PVC are also affected by the amount and structure of the plasticizer used. For a plasticizer to be effective and useful in PVC, it must contain two types of structural components, namely polar and nonpolar ones. The polar unit/group of the molecule is bound reversibly with the PVC polymer chain and is responsible for plasticizing its matrix. The solvation effect of the nonpolar portion of the molecule on PVC, however, is not significant enough to destroy the arranged (crystalline) structure of the polymer. In other words, the plasticizing efficiency of plasticizers depends on the ratio of the particular components in the molecule, i.e., polar groups (esters and ethers), nonpolar polarizable groups (benzene rings), and nonpolar nonpolarizable groups (alkyl and alkyne chains). The balance between the polar and nonpolar portions of the molecule is critical to controlling its solubilizing effect, and when a plasticizer is excessively polar, it can destroy the PVC crystallites. On the other hand, when it is excessively nonpolar, compatibility problems can arise [34]. The test results determined for compositions containing synthesized plasticizers are presented in Tables 7.2 and 7.3. The molecular weight of the plasticizer and the rate of plasticizer diffusion in the polymer matrix are some of the most important factors determining its effectiveness. A symptom of systemic instability includes excessive and rapid sweating out of the plasticizer, which leads to the deterioration of mechanical properties. Plasticizing efficiency improves with the rate of diffusion into the morphological structures of the polymer. Although the diffusion rate of small particle monomeric plasticizers is high, such systems are unstable, which may have to do with the rapid migration of the plasticizer from the polymer matrix. The results of plasticizer migration and water absorption determinations of PVC compositions are presented in Table 7.2 and graphically in Fig. 7.4. The migration of all the synthesized plasticizers was lower than that observed for the monomeric DEHP (Fig. 7.4). The lowest migration values were noted for the plasticizers containing 1,4-butanediol glycol (Compositions 5 and 6) or triethylene (Composition 10) and adipic acid.
Table 7.1 Formulations of the Tested PVC Compositions (phr). Composition Number 1
2
3
4
5
6
7
8
9
10
11
12
PVC S 70
100
100
100
100
100
100
100
100
100
100
100
100
DEHP
50
e
e
e
e
e
e
e
e
e
e
e
PETDEAz
e
50
e
e
e
e
e
e
e
e
e
e
PETDPAd
e
e
50
e
e
e
e
e
e
e
e
e
PETDPAz
e
e
e
50
e
e
e
e
e
e
e
e
PETBDAd
e
e
e
e
50
e
e
e
e
e
e
e
PETBDAz
e
e
e
e
e
50
e
e
e
e
e
e
PETDPAdGl
e
e
e
e
e
e
50
e
e
e
e
e
PETDPAzGl
e
e
e
e
e
e
e
50
e
e
e
e
PETDEAzGl
e
e
e
e
e
e
e
e
50
e
e
e
PETTEAd
e
e
e
e
e
e
e
e
e
50
e
e
H-1
e
e
e
e
e
e
e
e
e
e
50
e
PETTEAd ts
e
e
e
e
e
e
e
e
e
e
e
50
BP MC 8656 KA-ST
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
Ergoplast ES
2
2
2
2
2
2
2
2
2
2
2
2
Technical stearin
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
202
Component of the Composition
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Table 7.2 Test Results of Plasticizer Migration and Water Absorption of the Prepared PVC Compositions. Composition Numer/Plasticizer Code
Migration, %
Water Absorption, %
After 1 day
After 7 days
After 1 day
After 7 days
1/DEHP
1.34
1.76
0.10
0.16
2/PETDEAz
0.25
0.81
0.41
1.04
3/PETDPAd
0.24
0.57
0.28
0.70
4/PETDPAz
0.42
0.85
0.32
0.78
5/PETBDAd
0.12
0.27
0.16
0.43
6/PETBDAz
0.19
0.25
0.43
0.89
7/PETDPAdGl
0.84
1.19
0.42
1.44
8/PETDPAzGl
0.35
0.61
0.43
1.36
9/PETDEAzGl
0.32
0.62
0.39
1.03
10/PETTEAd
0.20
0.36
0.26
0.55
11/H-1
0.13
0.22
0.16
0.47
The plasticizers containing glycerine molecules in their structure (Compositions 7, 8, and 9) demonstrated a slightly higher migration value. This may well be the result of a greater molecular weight distribution among these samples and a possibly higher content of molecules with a lower weight. The migration values of the plasticizers present in compositions 5, 6, and 10 are comparable with the migration value of the commercial oligomeric plasticizer (Composition 11). The lowest water absorption values were observed for PVC compositions containing monomeric plasticizer. The hardness, tensile strength, and relative elongation at break of plasticized PVC specimens are shown in Table 7.3. Taking into account functional properties, the commonly accepted method for estimation of plasticizer effectiveness is determination of the hardness of the modified material at room temperature (Table 7.3). Based on the results presented in Table 7.4, it was concluded that the mechanical
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Table 7.3 Hardness and Mechanical Properties of PVC Compositions. Hardness, Sh A
Tensile Strenght, MPa
Elongation at Break, %
1/DEHP
83.0
18.2
407.3
2/PETDEAz
91.4
25.7
233.5
3/PETDPAd
92.0
26.1
365.2
4/PETDPAz
91.0
25.5
277.4
5/PETBDAd
92.0
19.8
259.5
6/PETBDAz
94.0
25.8
311.4
7/PETDPAdGl
97.0
16.4
159.4
8/PETDPAzGl
95.8
26.4
289.9
9/PETDEAzGl
90.0
23.3
328.7
10/PETTEAd
92.0
27.7
351.3
11/H-1
88.0
24.3
329.3
Migration (%)
Composition number
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0
1 day
1
2
3
4
8 5 6 7 Composition number
9
7 days
10
11
Figure 7.4 Variation of the migration of the plasticizers from the softened PVC samples.
properties of the plastificates, which contain the analyzed plasticizers, depend on the molecular weight and the structure of the plasticizer used; therefore, the plasticizer content in the studied compositions was kept the same. The hardness of the samples containing oligomeric plasticizers was slightly greater than that of the samples containing DEHP. The overall
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Table 7.4 Mass Loss, Decomposition, and Glass Transition Temperatures, Determined for the Tested Plasticizers Via Thermogravimetric Analysis and Differential Scanning Calorimetry. PETTEAd ts
Parameter
DEHP
H-1
Mass loss (%) (isothermal condition 180 C, 60 min, N2)
1.5
0.6
1.5
Temperature ( C) mass loss of 3%
273.9
355.1
344.7
Temperature ( C) mass loss of 5%
289.5
364.0
357.6
Temperature of decomposition ( C)
372.3
398.9
398.9
Glass transition temperature ( C)
e
44.2
49.4
tendency suggests that hardness increases with the molecular weight of the plasticizer [35]. However, these samples were characterized by greater tensile strength than those containing the monomeric plasticizer. In addition, in most cases, the elongation of the dicarboxylic acid chains had a positive impact on the resulting mechanical properties. The best results (tensile strength values over 26 MPa) were obtained for three plasticizers: PETDPAd, PETDPAzGl, and PETTEAd. As predicted, all of the synthesized oligomeric plasticizers show lower PVC composition plasticization effectiveness compared with the monomeric plasticizer (DEHP), as evidenced by both hardness and relative elongation at break values. This is due to the significant differences in the molecular weights of these plasticizers. The most unfavorable properties were demonstrated by the composition containing PETDPAdGl (adipic acid with glycerine and dipropylene glycol and a 2-ethylhexanol end group). Further investigations were aimed at verifying the processing and physicomechanical properties of PVC compositions containing an oligomeric plasticizer synthesized on an industrial scale in a reaction of poly(ethylene terephthalate) degradation using oligoesters containing a selected dicarboxylic acid and glycol. The plasticizer used in the technical scale synthesis in a 2000 kg capacity reactor was selected based on the test results of earlier studies.
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Crucial properties for plasticizer selection included low volatility, very good mechanical properties, low migration, and economic aspects, that is, the price of the raw materials used for obtaining the plasticizer. A plasticizer containing adipic acid, triethylene glycol, 2-ethylhexanol, and waste PET (PETTEAd ts [ts-technical scale]) was synthesized on a technical scale. The obtained product yielded analogical properties to the plasticizers obtained on a laboratory scale. The results presented below have been compared with the values for the DEHP and the commercial polymeric plasticizers (Table 7.4). The plasticizers selected above were used to prepare dry blendetype compounds. The plastificates containing the plasticizer synthesized on the technical scale (Composition 12) were analyzed and compared with the samples containing DEHP (Composition 1) and the commercial oligomeric variety (Composition 11). To determine the processing properties and functional performance of one of the selected synthesized PETTEAd ts plasticizers, a plastographic assessment of the PVC blend containing this plasticizer was carried out. The established parameters were compared with those determined for the PVC blend samples containing monomeric and oligomeric commercial plasticizers. The results of the plastographic measurements are shown in Table 7.5. A sample torque curve of the PVC composition is shown in Fig. 7.5. For polymer plasticization, compatibility should be interpreted as the ability to create a homogeneous system consisting of a polymeric matrix and plasticizer. Homogenization of the polymereplasticizer system already takes place when the two substances become initially mixed. The subsequent intensive process assisted by thermal and mechanical (shear) energy takes place at the processing stage. What is important is that the obtained polymer melt, after gelation and cooling, was thermodynamically stable. A lack of or limited compatibility of the plasticizer with the polymer would be apparent at the processing stage. In such cases, the compositions show much longer gelation time or they do not gel altogether and fail to form a uniform material with a solid structure. The results of the plastographic measurements are presented in Table 7.5. The gelation time (t) of the PVC composition containing PETTEAd ts was longer than that of the monomeric (DEHP) and oligomeric (H-1) plasticizers. Following the gelation stage, the homogenization of the PVC blend melt proceeds under similar conditions for both the composition containing the commercial polymeric plasticizer and for the evaluated PETTEAd ts plasticizer, as evidenced by similar ME torque values and the total W5 energy value (Table 7.5). Every PVC composition requires
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Table 7.5 Processing Characteristics of the Tested PVC Compositions. Composition Number Parameter
1
12
11
The time to reach (s) - Mb,(B)
24
12
8
- Md,(G)
34
34
14
- Mz_ ,(X)
46
46
30
- Gelation time (from point A to X), t
42
102
30
Torque, (nm) - Mb,(B)
6.1
6.9
8.5
- Md,(G)
6.7
8.5
9.5
- Mz_ ,(X)
7.3
10.1
10.6
- ME,(E)
6.7
8.5
8.6
130
117
104
- TG
135
137
116
- TX
140
152
135
- TE
156
155
158
Energy consumed in the area (kNm) W1 ¼ A B W2 ¼ B X W3 ¼ X E W4 ¼ A X W5 ¼ A E
0.5 0.5 5.7 1.0 6.6
0.2 2.7 5.6 2.9 8.5
0.3 0.7 8.0 1.0 8.9
Mw (g/mol)
390
3870
4230
Chamber temperature ( C) - Tb
a precise determination of the optimum conditions for its processing. Based on the plastographic studies, it can be concluded that the use of the PETTEAd ts plasticizer in PVC compositions requires processing at slightly higher temperatures of the plasticizing system. The synthesized PETTEAd ts oligomeric plasticizer imparted the plasticized PVC samples with very good tear resistance and tensile strength (Table 7.6). These samples, however, were least resistant to changes in the tensile strength and relative elongation at break values
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Figure 7.5 A sample torque curve of the PVC composition containing 50 phr of PETTEAd ts plasticizer. A, point of loading; B, minimum point of mixing; G, inflection point; X, maximum point of gelation; E, equilibrium state; t, gelation time.
caused by thermal aging. This is most probably a result of the lack of an antioxidant (e.g., bisphenol A) in the sample of the synthesized plasticizers. These substances are usually included in its commercial varieties. It is predicted that the use of stabilizers in synthesized PET plasticizers incorporated into PVC compositions should improve the resistance of the compositions to heat-induced changes in their strength properties. Tests of the basic physical and mechanical properties of PVC compositions containing oligomeric plasticizers synthesized from recycled PET confirm their usefulness for plasticizing poly(vinyl chloride). The properties of the PET-based synthesized oligoesters, including volatility and weight loss, proved they can be suitable for this purpose. The synthesized oligoesters are characterized by similar PVC plasticization efficiency to that of commercial polymeric plasticizers, which is confirmed by the values determined for the studied compositions: hardness, tensile strength, and relative elongation at break. Despite lacking antioxidants, the thermal stability of the synthesized oligoesters was higher than the stability of the monomeric plasticizer and its oligomeric variety, which are sold commercially and used in industry.
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Table 7.6 Weight Loss, Changes in Tensile Strength, and Relative Elongation Caused by Thermal Aging at 168 h/80 C. Composition Number 1
12
11
83.0
95.0
88.0
Tear resistance (N/mm)
48.0
101.0
70.8
Mass loss (%) 168 h/80 C
0.93
0.28
0.40
Tensile strength (MPa) before aging
23.5
27.7
24.3
Tensile strength (MPa) after aging
24.0
25.2
25.1
Change of tensile strength (%) after aging
þ2.13
9.02
þ3.29
Elongation at break (%) before aging
407.3
351.3
329.3
Elongation at break (%) after aging
400.0
318.7
338.0
Change of elongation at break (%) after aging
1.79
9.09
þ2.64
Parameter
Hardness ( Sh A)
The determined gelation time for the composition containing the PETTEAd ts plasticizer was longer compared with that of the monomeric and polymeric versions. Nevertheless, it fully meets the criteria determining whether a plasticizer is suitable for the processing of PVC compositions. The most significant of the resistance changes observed are most likely caused by the lack of additional thermal stability. Recycled poly(ethylene terephthalate) constitutes a potential raw material in the production of oligomeric plasticizers of poly(vinyl chloride). Oligomeric plasticizers obtained in the synthesis of waste PET are one of the products that can be used in the modification of poly(vinyl chloride). Both lower and higher molecular weight synthesis products obtained in the laboratory work can also be used in the modification of thermoplastic polymers.
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References [1] A.R. Berens, V.L. Folt, The significance of a particle-flow process in PVC melts, Polym. Eng. Sci. 8 (1) (1968) 5e10. [2] F.N. Cogswell, Sub-primary particles in PVC e identification and elucidation of their role during flow, Pure Appl. Chem. 52 (8) (1980) 2031e2050. [3] H. Mu¨nstedt, Relationship between rheological properties and structure of poly(vinyl chloride), J. Macromol. Sci. Phys. B 14 (2) (1977) 195e212. [4] J. Lynggae-Jorgensen, Structure and reological properties of poly(vinyl chloride) melts, Pure Appl. Chem. 53 (2) (1981) 533e547. [5] G.C. Portingell, Processing properties, in: G. Butters (Ed.), Particulate Nature of PVC e Formulation, Structure and Processing, Appl. Sci. Pub. Ltd., London, 1982. [6] K. Bortel, P. Szewczyk, Zale_znosc przetwo´rczych w1asnosci kompozycji suspensyjnego poli(chlorku winylu) od cie˛z_ aru cza˛steczkowego i morfologii ziarna, Polimery 38 (1993) 578e582. _ [7] S. Zajchowski, K. Piszczek, J. Tomaszewska, Zelowanie nieplastyfikowanego polichlorku winylu w procesie przetwo´rstwa, Polimery 46 (4) (2001) 232e245. _ [8] K. Piszczek, Zelowanie poli(chlorku winylu) w procesie walcowania, Polimery 50 (6) (2005) 441e448. [9] M. Gilbert, Fusion of PVC compounds, Plast. Rubber Int. 10 (3) (1985) 16e19. [10] K. Bortel, P. Szewczyk, Badania wp1ywu warunko´w przetwarzania nie zmie˛kczonych kompozycji poli(chlorku winylu) na strukture˛ polimeru, Polimery 11/12 (1996) 643e646. [11] M. Fujiyama, M. Kondou, Effect of gelation on the flow processability of poly(vinyl chloride), J. Appl. Polym. Sci. 90 (7) (2003) 1808e1824. [12] K. Piszczek, T. Sterzy nski, E. qukaszewicz, Visualization of gelation inhomogeneity of PVC, Polym. Test. 22 (1) (2003) 115e119. [13] B. Terselius, J.F. Jansson, J. Bystedt, Gelation of rigid PVC-pipes, J. Macromol. Sci. Phys. B 20 (3) (1981) 403e414. [14] T. Hattori, K. Tanaka, M. Matsuo, Fusion of particulate structure in polyvinyl chloride powder extrusion, Polym. Eng. Sci. 12 (3) (1972) 199e203. [15] R.J. Krzewki, E.A. Collins, Rheology of PVC compounds. I. Effect of processing variables on fusion, J. Macromol. Sci. Phys. B 20 (4) (1981) 443e464.
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[16] M.W. Allsopp, Mechanism of gelation of rigid PVC, in: R.H. Burgerss (Ed.), Manufacture and Processing of PVC, Mac Millan, New York, 1982. [17] B. Terselius, J.F. Jansson, Gelation of PVC. Part 5. Effect on structure and physical properties, Plast. Rubber Process. Appl. 5 (3) (1985) 193e201. [18] T. Hawkins, Evaluation of PVC compound on the Brabender torque rheometer, J. Vinyl Techn. 4 (3) (1982) 110e114. [19] P.G. Faulkner, The use a temperature programmable Brabender mixing head for the evaluation of the processing characteristics of PVC, J. Macromol. Sci. Phys. B 11 (2) (1975) 251e279. [20] J. Tomaszewska, T. Sterzy nski, K. Piszczek, Rigid poly(vinyl chloride) gelation in a Brabender measuring mixer. III. Transformation in the torque maximum, J. Appl. Polym. Sci. 106 (2007) 3158e3164. [21] C.H. Chen, R.D. Wesson, J.R. Collier, Y.W. Lo, Studies of rigid PVC compounds. II. Determination of the fusion level, J. Appl. Polym. Sci. 58 (7) (1995) 1093e1099. [22] M. Gilbert, J.C. Vyvoda, Thermal analysis technique for investigation gelation of rigid PVC, Polymer 22 (8) (1981) 1134e1136. [23] J. Skraga, A. Wa˛sicki, K. Piszczek, S. Zajchowski, R. Gruszka, J. Tomaszewska, Ocena stopnia z_zelowania plastyfikato´w poli(chlorku winylu) za pomoca˛ plastomeru kapilarnego, Polimery 44 (2) (1999) 138e145. [24] O.P. Obande, M. Gillbert, Effect of formulation and processing conditions on PVC fusion, Plast. Rubber Process. Appl. 10 (4) (1985) 231e238. [25] K. Bortel, Investigation of Processing and Physico-Chemical Properties of Selected Types of Suspension Poli(vinyl Chloride) and Their Blends, PhD thesis, Silesian University of Technology, Gliwice, 1997. [26] M. Moghri, H. Garmabi, M. Akbarian, Effect of processing parameters on fusion and mechanical properties of a twin-screw extruded rigid PVC pipe, J. Vinyl Addit. Technol. 9 (2) (2003) 81e89. [27] D.E. Marshall, R.P. Higgs, O.P. Obande, The effect of extrusion conditions on the fusion, structure and properties of rigid PVC, Plast. Rubber Process. Appl. 3 (4) (1983) 353e358. [28] P. Szewczyk, K. Bortel, in: G.H.W. Milburn (Ed.), Structure and Processing Conditions of PVC Effects on Properties, Colected Papers from Tempus Seminar “Modern Applications of Polymeric Materials”, Lizbona, Napier University, Edinburgh, May 1995.
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[29] J.A. Covas, M. Gillbert, D.E. Marshall, Twin screw extrusion of a rigid PVC compound effect of fusion and properties, Plast. Rubber Process. Appl. 92 (2) (1988) 107e116. [30] J.A. Covas, M. Gillbert, Single screw extrusion of poly(vinyl chloride): effect on fusion and properties, Polym. Eng. Sci. 32 (11) (1992) 743e750. [31] S. Zajchowski, J. Skraga, K. Piszczek, Wp1yw charakteru ziaren na plastyfikacje˛ i w1asciwosci plastyfikato´w poli(chlorku) winylu i kopolimero´w chlorku winylu z octanem winylu. Cz. IV. Badania procesu mieszania i z_ elowania PCW o zro´z_ nicowanej morfologii ziaren, Polimery 26 (4) (1981) 91e95. [32] K. Piszczek, J. Skraga, S. Zajchowski, Wp1yw charakteru ziaren na plastyfikacje˛ i w1asciwosci plastyfikato´w poli(chlorku) winylu i kopolimero´w chlorku winylu z octanem winylu. Cz. VI. Wspo´1_zelowanie PCW i kopolimero´w CW/OW, Polimery 26 (5) (1981) 170e174. [33] J.W. Summers, E.B. Rabinovitch, Use of acetone in determining poly(vinyl chloride) processing morphology and product morphology, J. Macromol. Sci. Phys. B 20 (2) (1981) 219e233. [34] C. Wilkes, J. Summers, C. Daniels, PVC Handbook, Carl Hanser Verlag, Munich, 2005. [35] G. Wypych, Handbook of Plasticizers, Chem Tech Publishing, Toronto-New York, 2004.
Plasticizers Derived from Post-consumer PET https://doi.org/10.1016/B978-0-323-46200-6.00007-6 Copyright © 2020 Elsevier Inc. All rights reserved.
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conditions are also a decisive factor in the final properties of plasticized products [26e30]. To assess the effectiveness and usefulness of new oligomeric plasticizers based on waste poly(ethylene terephthalate) in PVC processing, a number of PVC compositions were prepared and tested. The results presented below constitute a preliminary assessment of the physicomechanical properties of PVC compositions containing new oligomeric plasticizers based on waste poly(ethylene terephthalate) synthesized on a laboratory scale. The next part concerns comparative tests of PVC compositions using one of the selected plasticizers synthesized on an industrial scale, a monomeric plasticizer, and a commercially available polymeric plasticizer. Suspension poly(vinyl chloride) and new oligomeric plasticizers based on waste poly(ethylene terephthalate) were used in the plasticized PVC compositions. Monomeric bis(2-ethylhexyl) phthalate (DEHP) and the commercially available polymeric H-1 plasticizer (adipic oligoester, Lanxess, Germany) were used in the reference compositions. The plasticized PVC compositions also contained calcium-zinc BP MC 8656-ST (Baerlocher, Germany) as a thermal stabilizer, epoxidized soybean oil (ESO) (Ergoplast ES, Boryszew, Poland), and technical stearic acid (Brenntag, Poland). The characteristics of the polymer used in the PVC compositions are presented below. The PVC suspension Polanvil S-70 (K value ¼ 69.1; apparent bulk density ¼ 0.505 g/cm3; plasticizer absorption ¼ 29 g/100 g; average grain size ¼ 0.13 mm; residual VCM ¼ 0.7 ppm; Mw ¼ 83,600 g/mol, and dispersity ¼ 2.2) by Z.A. Anwil Wloclawek, Poland, was used to prepare plasticized PVC compositions. A fragment of the surface of the grain and cross section of the polymer Polanvil S-70 are presented in Figs. 7.1 and 7.2. The morphological structure of the grain [31e33] has a significant influence on the processing properties of a PVC composition, including the susceptibility of the plasticizer to become absorbed by the polymer. Therefore, porosimetry was used to define the size distribution of the porous structures of the polymer used in plasticized PVC compositions. The volume distribution of PVC grain pores as a function of their diameter is shown in Fig. 7.3. Oligomeric plasticizers synthesized in a reaction of PET degradation using oligoesters containing a selected type of dicarboxylic acid and glycol were used in the PVC blends. The properties of these plasticizers are presented in Chapter 6.
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Figure 7.1 Fragment of Polanvil S-70 grain surfacedan area on the surface without an outer layer with a developed surface.
Figure 7.2 A fragment of PVC Polanvil S-70 grain cross section, visible primary particles.
None of the synthesized plasticizers evaluated in this study contained any commercially available antioxidants (e.g., bisphenol A) commonly used in commercial plasticizers. The tests were carried out using the following research methodology. A Hitachi SU8010 scanning electron microscope (Hitachi, Japan, 2011)
198
Log Differential Intrusion vs Pore size Log Differential Intrusion
Cumulative Intrusion
2.5 1.2
1.0
0.6
1.0 0.4
P LASTICIZERS D ERIVED
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Cumulative Intrusion (mL/g)
Log Differential Intrusion (mL/g)
2.0
FROM
0.2
0.0 0.0 100
50
10
5
1
0.5
0.1
0.05
Pore size Diameter (µm)
Figure 7.3 Pore volume distribution as a function of pore diameter for PVC Polanvil S70 grains.
0.01
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was used to study the morphology of the surface and interior of the PVC grains. All the samples were sprayed with a 7e8 nm-thick layer of gold. The basic conditions for microscopic observation are type of detector: SE (second electron), accelerating voltage: 2 kV, current: approximately 10 mA, and working distance: 8e9 mm. All the samples (both for cutting and microscopic observation) were glued to a special table using conductive carbon tape. An E-3500 Ion Milling System (Hitachi, Japan, 2011) was used for cross-sectional surface microscopy. The conditions for cutting the samples with an ion cutting machine were as follows: - cutting time: from 10 to 16 h depending on the thickness of the sample, - accelerating voltage: 6 kV, - discharge voltage: 4 kV. The morphological structure of the PVC (Polanvil S-70) was also evaluated using mercury porosimetry using a Micrometrics AutoPore IV 9500 device. The amount of mercury injected into the pores of the previously degassed sample was recorded for subsequent predetermined pressures of up to 400 MPa. The volume and specific surface area of the pores and their size distribution were determined using the method described above. As per the recommendations of ASTM D 2873, according to which the tests were conducted, porous structures with diameters >3100 nm (3.1 mm), corresponding to intergranular spaces, were not considered in the given values of the pores’ specific volume. The thermal stability properties were determined by thermogravimetric analysis (TGA) using a model TGA/SDTA 851e Mettler Toledo device (Switzerland) at a heating rate of 20 C/min from 25 C to 600 C in a nitrogen atmosphere and a flow rate of 60 mL/min. Experiments were performed in an aluminum oxide pan. Volatilization of the plasticizers and the plasticized PVC granulates was performed by the isothermal thermogravimetry method at 180 C for plasticizers, and at 150 C for plasticized PVC granulates, for 60 min under nitrogen with a flow rate of 60 mL/min. From the starting temperature of 25 C to the isothermal testing temperature, the samples were heated at a rate of 50 C/min. After establishing the isothermal conditions (programmed temperature), the weight loss of each sample was taken as the starting value. The deviation of the real temperature value from the programmed temperature value amounted to c.0.25 C.
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Differential scanning calorimetry (DSC) of the samples was performed using a model DSC 822e/700 Mettler Toledo (Switzerland) device. Specimens of 6e8 mg were heated from 70 C to 150 C at a rate of 20 C/min and cooled at the same rate in a nitrogen atmosphere with a flow rate of 60 mL/min. The samples were hermetically closed in aluminum DSC capsules. The glass transition temperature was determined during the second heating run. Data analyses of TGA and DSC results were performed using the STARe v12.10 software supplied by Mettler Toledo. The hardness of the plasticizers was determined in accordance with EN ISO 868 Shore A scale hardness. The water absorption, expressed as wt.%, is determined by weight absorbability and is defined as the ratio of the mass of water absorbed by the sample to that of the sample in a dry state. The test was carried out in accordance with ISO 62 method A. The determination of plasticizer migration from the tested samples was carried out in accordance with EN ISO 177. Polyethylene film was used as the absorbing material. Tensile strength and relative elongation at break were determined according to standard EN ISO 527-2. A Brabender Plast-Corder plastograph was used to evaluate the processing properties of the PVC compositions tested. This was performed using a W30H kneader while maintaining the following constant measurement conditions: kneader temperatured150 C (determination of gelation time); rotor rpmd30/min.; and sample sized26e28 g. During the measurements, the following parameters were recorded: time points when the particular stages of the composition plasticizing process were reached, composition gelation time, dynamic thermal stability value, torques, mass temperature, and energy consumed in the subsequent stages of the PVC melting process. Plasticized PVC compositions containing polymer, plasticizer, and auxiliaries were prepared in a high speed, hot-cold MDF-30 mixer manufactured by Metalchem Toru n. To disperse the individual ingredients of the composition, the charge was mixed in a hot mixer until reaching a temperature of 130 C. To obtain high-quality dry blends, the sequence in which the individual components of a PVC mix are fed is crucial. The polymer with a stabilizing and lubricating composition and ESO were mixed at a temperature of 70 C, following which a plasticizer was introduced. This sequence of plasticizer insertion is justified and necessary because at this temperature, the poly(vinyl chloride) grains are partially swelled; therefore, the relaxed porous structures of the PVC grains are more easily and quickly
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penetrated by the plasticizer. To obtain dry PVC mixtures, the hot mixture was cooled in a cold mixer down to 40 C. The obtained dry blends of PVC were extruded by means of a laboratory extruder to obtain a granulate, which was then pressed. The pressed plates were used to prepared samples for physical and mechanical tests. The plasticized PVC formulations are shown in Table 7.1. The mechanical properties of plasticized PVC are also affected by the amount and structure of the plasticizer used. For a plasticizer to be effective and useful in PVC, it must contain two types of structural components, namely polar and nonpolar ones. The polar unit/group of the molecule is bound reversibly with the PVC polymer chain and is responsible for plasticizing its matrix. The solvation effect of the nonpolar portion of the molecule on PVC, however, is not significant enough to destroy the arranged (crystalline) structure of the polymer. In other words, the plasticizing efficiency of plasticizers depends on the ratio of the particular components in the molecule, i.e., polar groups (esters and ethers), nonpolar polarizable groups (benzene rings), and nonpolar nonpolarizable groups (alkyl and alkyne chains). The balance between the polar and nonpolar portions of the molecule is critical to controlling its solubilizing effect, and when a plasticizer is excessively polar, it can destroy the PVC crystallites. On the other hand, when it is excessively nonpolar, compatibility problems can arise [34]. The test results determined for compositions containing synthesized plasticizers are presented in Tables 7.2 and 7.3. The molecular weight of the plasticizer and the rate of plasticizer diffusion in the polymer matrix are some of the most important factors determining its effectiveness. A symptom of systemic instability includes excessive and rapid sweating out of the plasticizer, which leads to the deterioration of mechanical properties. Plasticizing efficiency improves with the rate of diffusion into the morphological structures of the polymer. Although the diffusion rate of small particle monomeric plasticizers is high, such systems are unstable, which may have to do with the rapid migration of the plasticizer from the polymer matrix. The results of plasticizer migration and water absorption determinations of PVC compositions are presented in Table 7.2 and graphically in Fig. 7.4. The migration of all the synthesized plasticizers was lower than that observed for the monomeric DEHP (Fig. 7.4). The lowest migration values were noted for the plasticizers containing 1,4-butanediol glycol (Compositions 5 and 6) or triethylene (Composition 10) and adipic acid.
Table 7.1 Formulations of the Tested PVC Compositions (phr). Composition Number 1
2
3
4
5
6
7
8
9
10
11
12
PVC S 70
100
100
100
100
100
100
100
100
100
100
100
100
DEHP
50
e
e
e
e
e
e
e
e
e
e
e
PETDEAz
e
50
e
e
e
e
e
e
e
e
e
e
PETDPAd
e
e
50
e
e
e
e
e
e
e
e
e
PETDPAz
e
e
e
50
e
e
e
e
e
e
e
e
PETBDAd
e
e
e
e
50
e
e
e
e
e
e
e
PETBDAz
e
e
e
e
e
50
e
e
e
e
e
e
PETDPAdGl
e
e
e
e
e
e
50
e
e
e
e
e
PETDPAzGl
e
e
e
e
e
e
e
50
e
e
e
e
PETDEAzGl
e
e
e
e
e
e
e
e
50
e
e
e
PETTEAd
e
e
e
e
e
e
e
e
e
50
e
e
H-1
e
e
e
e
e
e
e
e
e
e
50
e
PETTEAd ts
e
e
e
e
e
e
e
e
e
e
e
50
BP MC 8656 KA-ST
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
Ergoplast ES
2
2
2
2
2
2
2
2
2
2
2
2
Technical stearin
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
202
Component of the Composition
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Table 7.2 Test Results of Plasticizer Migration and Water Absorption of the Prepared PVC Compositions. Composition Numer/Plasticizer Code
Migration, %
Water Absorption, %
After 1 day
After 7 days
After 1 day
After 7 days
1/DEHP
1.34
1.76
0.10
0.16
2/PETDEAz
0.25
0.81
0.41
1.04
3/PETDPAd
0.24
0.57
0.28
0.70
4/PETDPAz
0.42
0.85
0.32
0.78
5/PETBDAd
0.12
0.27
0.16
0.43
6/PETBDAz
0.19
0.25
0.43
0.89
7/PETDPAdGl
0.84
1.19
0.42
1.44
8/PETDPAzGl
0.35
0.61
0.43
1.36
9/PETDEAzGl
0.32
0.62
0.39
1.03
10/PETTEAd
0.20
0.36
0.26
0.55
11/H-1
0.13
0.22
0.16
0.47
The plasticizers containing glycerine molecules in their structure (Compositions 7, 8, and 9) demonstrated a slightly higher migration value. This may well be the result of a greater molecular weight distribution among these samples and a possibly higher content of molecules with a lower weight. The migration values of the plasticizers present in compositions 5, 6, and 10 are comparable with the migration value of the commercial oligomeric plasticizer (Composition 11). The lowest water absorption values were observed for PVC compositions containing monomeric plasticizer. The hardness, tensile strength, and relative elongation at break of plasticized PVC specimens are shown in Table 7.3. Taking into account functional properties, the commonly accepted method for estimation of plasticizer effectiveness is determination of the hardness of the modified material at room temperature (Table 7.3). Based on the results presented in Table 7.4, it was concluded that the mechanical
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Table 7.3 Hardness and Mechanical Properties of PVC Compositions. Hardness, Sh A
Tensile Strenght, MPa
Elongation at Break, %
1/DEHP
83.0
18.2
407.3
2/PETDEAz
91.4
25.7
233.5
3/PETDPAd
92.0
26.1
365.2
4/PETDPAz
91.0
25.5
277.4
5/PETBDAd
92.0
19.8
259.5
6/PETBDAz
94.0
25.8
311.4
7/PETDPAdGl
97.0
16.4
159.4
8/PETDPAzGl
95.8
26.4
289.9
9/PETDEAzGl
90.0
23.3
328.7
10/PETTEAd
92.0
27.7
351.3
11/H-1
88.0
24.3
329.3
Migration (%)
Composition number
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0
1 day
1
2
3
4
8 5 6 7 Composition number
9
7 days
10
11
Figure 7.4 Variation of the migration of the plasticizers from the softened PVC samples.
properties of the plastificates, which contain the analyzed plasticizers, depend on the molecular weight and the structure of the plasticizer used; therefore, the plasticizer content in the studied compositions was kept the same. The hardness of the samples containing oligomeric plasticizers was slightly greater than that of the samples containing DEHP. The overall
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Table 7.4 Mass Loss, Decomposition, and Glass Transition Temperatures, Determined for the Tested Plasticizers Via Thermogravimetric Analysis and Differential Scanning Calorimetry. PETTEAd ts
Parameter
DEHP
H-1
Mass loss (%) (isothermal condition 180 C, 60 min, N2)
1.5
0.6
1.5
Temperature ( C) mass loss of 3%
273.9
355.1
344.7
Temperature ( C) mass loss of 5%
289.5
364.0
357.6
Temperature of decomposition ( C)
372.3
398.9
398.9
Glass transition temperature ( C)
e
44.2
49.4
tendency suggests that hardness increases with the molecular weight of the plasticizer [35]. However, these samples were characterized by greater tensile strength than those containing the monomeric plasticizer. In addition, in most cases, the elongation of the dicarboxylic acid chains had a positive impact on the resulting mechanical properties. The best results (tensile strength values over 26 MPa) were obtained for three plasticizers: PETDPAd, PETDPAzGl, and PETTEAd. As predicted, all of the synthesized oligomeric plasticizers show lower PVC composition plasticization effectiveness compared with the monomeric plasticizer (DEHP), as evidenced by both hardness and relative elongation at break values. This is due to the significant differences in the molecular weights of these plasticizers. The most unfavorable properties were demonstrated by the composition containing PETDPAdGl (adipic acid with glycerine and dipropylene glycol and a 2-ethylhexanol end group). Further investigations were aimed at verifying the processing and physicomechanical properties of PVC compositions containing an oligomeric plasticizer synthesized on an industrial scale in a reaction of poly(ethylene terephthalate) degradation using oligoesters containing a selected dicarboxylic acid and glycol. The plasticizer used in the technical scale synthesis in a 2000 kg capacity reactor was selected based on the test results of earlier studies.
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Crucial properties for plasticizer selection included low volatility, very good mechanical properties, low migration, and economic aspects, that is, the price of the raw materials used for obtaining the plasticizer. A plasticizer containing adipic acid, triethylene glycol, 2-ethylhexanol, and waste PET (PETTEAd ts [ts-technical scale]) was synthesized on a technical scale. The obtained product yielded analogical properties to the plasticizers obtained on a laboratory scale. The results presented below have been compared with the values for the DEHP and the commercial polymeric plasticizers (Table 7.4). The plasticizers selected above were used to prepare dry blendetype compounds. The plastificates containing the plasticizer synthesized on the technical scale (Composition 12) were analyzed and compared with the samples containing DEHP (Composition 1) and the commercial oligomeric variety (Composition 11). To determine the processing properties and functional performance of one of the selected synthesized PETTEAd ts plasticizers, a plastographic assessment of the PVC blend containing this plasticizer was carried out. The established parameters were compared with those determined for the PVC blend samples containing monomeric and oligomeric commercial plasticizers. The results of the plastographic measurements are shown in Table 7.5. A sample torque curve of the PVC composition is shown in Fig. 7.5. For polymer plasticization, compatibility should be interpreted as the ability to create a homogeneous system consisting of a polymeric matrix and plasticizer. Homogenization of the polymereplasticizer system already takes place when the two substances become initially mixed. The subsequent intensive process assisted by thermal and mechanical (shear) energy takes place at the processing stage. What is important is that the obtained polymer melt, after gelation and cooling, was thermodynamically stable. A lack of or limited compatibility of the plasticizer with the polymer would be apparent at the processing stage. In such cases, the compositions show much longer gelation time or they do not gel altogether and fail to form a uniform material with a solid structure. The results of the plastographic measurements are presented in Table 7.5. The gelation time (t) of the PVC composition containing PETTEAd ts was longer than that of the monomeric (DEHP) and oligomeric (H-1) plasticizers. Following the gelation stage, the homogenization of the PVC blend melt proceeds under similar conditions for both the composition containing the commercial polymeric plasticizer and for the evaluated PETTEAd ts plasticizer, as evidenced by similar ME torque values and the total W5 energy value (Table 7.5). Every PVC composition requires
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Table 7.5 Processing Characteristics of the Tested PVC Compositions. Composition Number Parameter
1
12
11
The time to reach (s) - Mb,(B)
24
12
8
- Md,(G)
34
34
14
- Mz_ ,(X)
46
46
30
- Gelation time (from point A to X), t
42
102
30
Torque, (nm) - Mb,(B)
6.1
6.9
8.5
- Md,(G)
6.7
8.5
9.5
- Mz_ ,(X)
7.3
10.1
10.6
- ME,(E)
6.7
8.5
8.6
130
117
104
- TG
135
137
116
- TX
140
152
135
- TE
156
155
158
Energy consumed in the area (kNm) W1 ¼ A B W2 ¼ B X W3 ¼ X E W4 ¼ A X W5 ¼ A E
0.5 0.5 5.7 1.0 6.6
0.2 2.7 5.6 2.9 8.5
0.3 0.7 8.0 1.0 8.9
Mw (g/mol)
390
3870
4230
Chamber temperature ( C) - Tb
a precise determination of the optimum conditions for its processing. Based on the plastographic studies, it can be concluded that the use of the PETTEAd ts plasticizer in PVC compositions requires processing at slightly higher temperatures of the plasticizing system. The synthesized PETTEAd ts oligomeric plasticizer imparted the plasticized PVC samples with very good tear resistance and tensile strength (Table 7.6). These samples, however, were least resistant to changes in the tensile strength and relative elongation at break values
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Figure 7.5 A sample torque curve of the PVC composition containing 50 phr of PETTEAd ts plasticizer. A, point of loading; B, minimum point of mixing; G, inflection point; X, maximum point of gelation; E, equilibrium state; t, gelation time.
caused by thermal aging. This is most probably a result of the lack of an antioxidant (e.g., bisphenol A) in the sample of the synthesized plasticizers. These substances are usually included in its commercial varieties. It is predicted that the use of stabilizers in synthesized PET plasticizers incorporated into PVC compositions should improve the resistance of the compositions to heat-induced changes in their strength properties. Tests of the basic physical and mechanical properties of PVC compositions containing oligomeric plasticizers synthesized from recycled PET confirm their usefulness for plasticizing poly(vinyl chloride). The properties of the PET-based synthesized oligoesters, including volatility and weight loss, proved they can be suitable for this purpose. The synthesized oligoesters are characterized by similar PVC plasticization efficiency to that of commercial polymeric plasticizers, which is confirmed by the values determined for the studied compositions: hardness, tensile strength, and relative elongation at break. Despite lacking antioxidants, the thermal stability of the synthesized oligoesters was higher than the stability of the monomeric plasticizer and its oligomeric variety, which are sold commercially and used in industry.
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Table 7.6 Weight Loss, Changes in Tensile Strength, and Relative Elongation Caused by Thermal Aging at 168 h/80 C. Composition Number 1
12
11
83.0
95.0
88.0
Tear resistance (N/mm)
48.0
101.0
70.8
Mass loss (%) 168 h/80 C
0.93
0.28
0.40
Tensile strength (MPa) before aging
23.5
27.7
24.3
Tensile strength (MPa) after aging
24.0
25.2
25.1
Change of tensile strength (%) after aging
þ2.13
9.02
þ3.29
Elongation at break (%) before aging
407.3
351.3
329.3
Elongation at break (%) after aging
400.0
318.7
338.0
Change of elongation at break (%) after aging
1.79
9.09
þ2.64
Parameter
Hardness ( Sh A)
The determined gelation time for the composition containing the PETTEAd ts plasticizer was longer compared with that of the monomeric and polymeric versions. Nevertheless, it fully meets the criteria determining whether a plasticizer is suitable for the processing of PVC compositions. The most significant of the resistance changes observed are most likely caused by the lack of additional thermal stability. Recycled poly(ethylene terephthalate) constitutes a potential raw material in the production of oligomeric plasticizers of poly(vinyl chloride). Oligomeric plasticizers obtained in the synthesis of waste PET are one of the products that can be used in the modification of poly(vinyl chloride). Both lower and higher molecular weight synthesis products obtained in the laboratory work can also be used in the modification of thermoplastic polymers.
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