**2. Thermoplastic starch preparation**

The gelatinization of starch is a process that permits the release of starch macromolecules from granules. It can be carried out by exposing starch granules to heat and shear in the presence of moisture. In the gelatinization of starch during extrusion, it is important to have strict control of the energy applied and the moisture content. The gelatinization process is depicted in Figure 1. The application of excessive heat and shear, such as that observed during extrusion processing of starch at low moisture content, leads to its thermo-mechanical degradation (Gomez & Aguilera, 1983, 1984, Lai & Kokini, 1991). Products of starch degradation are mainly dextrin, and in more extreme cases oligomer and sugar (Gomez & Aguilera, 1983, 1984). Once starch granules are disrupted, the resulting gelatinized starch (GS) can be mixed with a

Melt Blending with Thermoplastic Starch 5

processing temperature far below the processing conditions of most synthetic polymers, i.e. >150C, in order to avoid water vapor bubbles into TPS extrudates (Souza & Andrade, 2002; Farhat et al., 2003; Ma et al, 2006; Chaudhary, 2010). The development of an extruder configuration having a venting zone after both starch gelatinization and plasticization processes were accomplished and before exiting from the die allowed the preparation of

The rheological and thermal properties of water-free TPS materials having high glycerol contents (29, 36 and 40%) were evaluated by DSC analysis and rheological measurements in shear and oscillatory modes (Rodriguez-Gonzalez et al., 2004). TPS materials were labeled according to their glycerol content. Hence, TPS29,33, TPS36 and TPS40 have 29, 33, 36 and

Fig. 2. DSC thermograms of TPS samples conditioned for 24h at 0% R.H. The glycerol

As previously mentioned, TPS materials prepared in this work are almost water-free starchglycerol systems. Compared with previous work, TPS materials prepared in this work are binary systems which allow a more straightforward evaluation of the effect of glycerol on the thermal transitions of starch. DSC analysis of TPS shows a thermal transition below ambient temperature that decreases as glycerol content increases (Figure 2). On the other hand, no thermal transitions are observed between 25 and 200ºC (not shown). The Tg of TPS decreases from –45 to –56°C as glycerol content increases from 29% to 40%. Van Soest et al. have reported the Tg of extruded TPS materials containing a starch/water/glycerol ratio of 100:27:5 of +59°C (Van Soest et al., 1996). Forssell et al. (1997) studied the thermal transition of TPS materials prepared in a melt mixer as a function of glycerol and water content. Depending upon the composition, TPS materials presented one or two thermal transitions. In that work, at the lowest water content (ca. 1%) the upper transition of TPS decreases from

content in TPS is 40, 36 and 29% from the top to the bottom.

water-free TPS (Favis et al., 2001; Favis et al., 2003, Favis et al., 2005).

**3. Rheological and thermal properties of water-free TPS** 

40% of glycerol.

suitable plasticizer to reduce its melting temperature and improve its processabillity. This material is known as thermoplastic starch (TPS).

Fig. 1. Schematic representation of starch gelatinization and plasticization processes during extrusion.

Water is a good plasticizer for TPS but its use leads to a high dependence of final properties to environmental conditions of humidity. Utilization of plasticizers other than water helps to stabilize the properties of TPS. The main plasticizer used in TPS composition is glycerol (Forssell et al. 1997; Mathew & Dufresne, 2002; Souza & Andrade, 2002; Ma & Yu, 2004a; Ma & Yu, 2004b; Parra et al., 2004; Rodriguez-Gonzalez et al., 2003a; Rodriguez-Gonzalez et al., 2003b; Rodriguez-Gonzalez et al., 2004; Mali et al., 2005; Chand et al., 2006; Ma et al, 2006; Teixeira et al., 2007; Talja et al., 2007; Talja et al., 2008; Tena-Salcido et al., 2008; Chaudhary, 2010; Mendez-Hernandez et al., 2011) but other alcohols (Da Roz et al., 2006), polyols (Mathew & Dufresne, 2002; Parra et al., 2004; Mali et al., 2005; Da Roz et al., 2006; Talja et al., 2007; Chaudhary, 2010), sugars (Da Roz et al., 2006; Teixeira et al., 2007; Talja, 2008) or nitrogen compounds such as ethanolamine (Ma et al, 2006), formamide (Ma & Yu, 2004a; Ma & Yu, 2004b), acetamide (Ma & Yu, 2004a) or urea (You et al., 2003; Ma et al, 2006) have also been successfully employed. TPS materials have been prepared using casting process (Mathew & Dufresne, 2002; Parra, et al., 2004; Mali et al., 2005; Chand et al., 2006; Talja et al., 2007; Talja, 2008) or by melt mixing in batch, internal mixer (Forssell et al. 1997; Da Roz et al., 2006; Teixeira et al., 2007), or continuous equipment such as single (Souza & Andrade, 2002; Ma & Yu, 2004a; Ma & Yu, 2004b; Ma et al, 2006) or twin-screw extruders (Rodriguez-Gonzalez et al., 2003a; Rodriguez-Gonzalez et al., 2003b; You et al., 2003; Rodriguez-Gonzalez et al., 2004; Tena-Salcido et al., 2008; Chaudhary, 2010; Mendez-Hernandez et al., 2011). In the case of melt mixing processes, starch, plasticizer and water have been fed as dry blends (Ma & Yu, 2004a; Ma & Yu, 2004b; Da Roz et al., 2006; Ma et al, 2006; Chaudhary, 2010) or slurries (Rodriguez-Gonzalez et al., 2003a; Rodriguez-Gonzalez et al., 2003b; Rodriguez-Gonzalez et al., 2004; Tena-Salcido et al., 2008; Mendez-Hernandez et al., 2011). In some cases, TPS materials prepared by melt mixing have a significant water content which limits the

suitable plasticizer to reduce its melting temperature and improve its processabillity. This

Fig. 1. Schematic representation of starch gelatinization and plasticization processes during

Water is a good plasticizer for TPS but its use leads to a high dependence of final properties to environmental conditions of humidity. Utilization of plasticizers other than water helps to stabilize the properties of TPS. The main plasticizer used in TPS composition is glycerol (Forssell et al. 1997; Mathew & Dufresne, 2002; Souza & Andrade, 2002; Ma & Yu, 2004a; Ma & Yu, 2004b; Parra et al., 2004; Rodriguez-Gonzalez et al., 2003a; Rodriguez-Gonzalez et al., 2003b; Rodriguez-Gonzalez et al., 2004; Mali et al., 2005; Chand et al., 2006; Ma et al, 2006; Teixeira et al., 2007; Talja et al., 2007; Talja et al., 2008; Tena-Salcido et al., 2008; Chaudhary, 2010; Mendez-Hernandez et al., 2011) but other alcohols (Da Roz et al., 2006), polyols (Mathew & Dufresne, 2002; Parra et al., 2004; Mali et al., 2005; Da Roz et al., 2006; Talja et al., 2007; Chaudhary, 2010), sugars (Da Roz et al., 2006; Teixeira et al., 2007; Talja, 2008) or nitrogen compounds such as ethanolamine (Ma et al, 2006), formamide (Ma & Yu, 2004a; Ma & Yu, 2004b), acetamide (Ma & Yu, 2004a) or urea (You et al., 2003; Ma et al, 2006) have also been successfully employed. TPS materials have been prepared using casting process (Mathew & Dufresne, 2002; Parra, et al., 2004; Mali et al., 2005; Chand et al., 2006; Talja et al., 2007; Talja, 2008) or by melt mixing in batch, internal mixer (Forssell et al. 1997; Da Roz et al., 2006; Teixeira et al., 2007), or continuous equipment such as single (Souza & Andrade, 2002; Ma & Yu, 2004a; Ma & Yu, 2004b; Ma et al, 2006) or twin-screw extruders (Rodriguez-Gonzalez et al., 2003a; Rodriguez-Gonzalez et al., 2003b; You et al., 2003; Rodriguez-Gonzalez et al., 2004; Tena-Salcido et al., 2008; Chaudhary, 2010; Mendez-Hernandez et al., 2011). In the case of melt mixing processes, starch, plasticizer and water have been fed as dry blends (Ma & Yu, 2004a; Ma & Yu, 2004b; Da Roz et al., 2006; Ma et al, 2006; Chaudhary, 2010) or slurries (Rodriguez-Gonzalez et al., 2003a; Rodriguez-Gonzalez et al., 2003b; Rodriguez-Gonzalez et al., 2004; Tena-Salcido et al., 2008; Mendez-Hernandez et al., 2011). In some cases, TPS materials prepared by melt mixing have a significant water content which limits the

material is known as thermoplastic starch (TPS).

extrusion.

processing temperature far below the processing conditions of most synthetic polymers, i.e. >150C, in order to avoid water vapor bubbles into TPS extrudates (Souza & Andrade, 2002; Farhat et al., 2003; Ma et al, 2006; Chaudhary, 2010). The development of an extruder configuration having a venting zone after both starch gelatinization and plasticization processes were accomplished and before exiting from the die allowed the preparation of water-free TPS (Favis et al., 2001; Favis et al., 2003, Favis et al., 2005).

#### **3. Rheological and thermal properties of water-free TPS**

The rheological and thermal properties of water-free TPS materials having high glycerol contents (29, 36 and 40%) were evaluated by DSC analysis and rheological measurements in shear and oscillatory modes (Rodriguez-Gonzalez et al., 2004). TPS materials were labeled according to their glycerol content. Hence, TPS29,33, TPS36 and TPS40 have 29, 33, 36 and 40% of glycerol.

Fig. 2. DSC thermograms of TPS samples conditioned for 24h at 0% R.H. The glycerol content in TPS is 40, 36 and 29% from the top to the bottom.

As previously mentioned, TPS materials prepared in this work are almost water-free starchglycerol systems. Compared with previous work, TPS materials prepared in this work are binary systems which allow a more straightforward evaluation of the effect of glycerol on the thermal transitions of starch. DSC analysis of TPS shows a thermal transition below ambient temperature that decreases as glycerol content increases (Figure 2). On the other hand, no thermal transitions are observed between 25 and 200ºC (not shown). The Tg of TPS decreases from –45 to –56°C as glycerol content increases from 29% to 40%. Van Soest et al. have reported the Tg of extruded TPS materials containing a starch/water/glycerol ratio of 100:27:5 of +59°C (Van Soest et al., 1996). Forssell et al. (1997) studied the thermal transition of TPS materials prepared in a melt mixer as a function of glycerol and water content. Depending upon the composition, TPS materials presented one or two thermal transitions. In that work, at the lowest water content (ca. 1%) the upper transition of TPS decreases from

Melt Blending with Thermoplastic Starch 7

Fig. 4. Effect of glycerol content on (a) elastic modulus (G') and (b) loss modulus (G") of TPS

materials evaluated at 150ºC

145 to 70°C as the glycerol content is increased from 14 to 29% while only TPS compounded with 29 and 39% glycerol showed lower transitions both at -50°C. The upper transition was attributed to starch-rich phase while the lower transition was related to a starch-poor phase. Lourdin and coworkers prepared TPS cast films by mixing starch with different amounts of water and glycerol (Lourdin et al., 1997a; Lourdin et al., 1997b). Films having around 13% water content showed a reduction of Tg from 90 to 0°C when glycerol content increased from 0 to 24% (Lourdin et al., 1997a). In that case they observed a glassy to rubbery transition of TPS at around 15% glycerol. In a further paper, they compared the Tg of TPS films having around 11% water with respect to glycerol content and they found that Tg decreased from 126 to 28°C when glycerol content was increased from 0 to 40% (Lourdin et al., 1997b). Discrepancies in Tg values as a function of glycerol content can be related, as mentioned by Kalichevsky to the mixing history during TPS preparation (Kalichevsky et al., 1993).

During on-line measurements, TPS extrudates did not present bubbles due to the almost absence of water. The pressure readings of TPS36 and TPS40 at 150ºC were quite regular while those of TPS29 were mostly irregular. For this reason only TPS36 and TPS40 were evaluated. As observed by other authors (Aichholzer and Fritz, 1998; Della Valle et al., 1992; Lai and Kokini, 1990; Senouci and Smith, 1988; Willett et al., 1995; Willett et al., 1998), the viscosity () of both TPS and PE1 melts display a power-law (shear thinning) behavior at the shear rate ( ) interval developed over die extrusion conditions (Figure 3). The of TPS materials depends on the plasticizer content. An increment of glycerol content from 36% to 40% results in a reduction of 20% of of TPS36 (at ~ 130 s-1).

Fig. 3. Comparison of the viscosity of TPS40, TPS36 and PE1 measured on-line in the TSE at 150ºC.

145 to 70°C as the glycerol content is increased from 14 to 29% while only TPS compounded with 29 and 39% glycerol showed lower transitions both at -50°C. The upper transition was attributed to starch-rich phase while the lower transition was related to a starch-poor phase. Lourdin and coworkers prepared TPS cast films by mixing starch with different amounts of water and glycerol (Lourdin et al., 1997a; Lourdin et al., 1997b). Films having around 13% water content showed a reduction of Tg from 90 to 0°C when glycerol content increased from 0 to 24% (Lourdin et al., 1997a). In that case they observed a glassy to rubbery transition of TPS at around 15% glycerol. In a further paper, they compared the Tg of TPS films having around 11% water with respect to glycerol content and they found that Tg decreased from 126 to 28°C when glycerol content was increased from 0 to 40% (Lourdin et al., 1997b). Discrepancies in Tg values as a function of glycerol content can be related, as mentioned by Kalichevsky to the

During on-line measurements, TPS extrudates did not present bubbles due to the almost absence of water. The pressure readings of TPS36 and TPS40 at 150ºC were quite regular while those of TPS29 were mostly irregular. For this reason only TPS36 and TPS40 were evaluated. As observed by other authors (Aichholzer and Fritz, 1998; Della Valle et al., 1992; Lai and Kokini, 1990; Senouci and Smith, 1988; Willett et al., 1995; Willett et al., 1998), the viscosity () of both TPS and PE1 melts display a power-law (shear thinning) behavior at the

materials depends on the plasticizer content. An increment of glycerol content from 36% to

Fig. 3. Comparison of the viscosity of TPS40, TPS36 and PE1 measured on-line in the TSE at

) interval developed over die extrusion conditions (Figure 3). The of TPS

~ 130 s-1).

mixing history during TPS preparation (Kalichevsky et al., 1993).

40% results in a reduction of 20% of of TPS36 (at

shear rate (

150ºC.

Fig. 4. Effect of glycerol content on (a) elastic modulus (G') and (b) loss modulus (G") of TPS materials evaluated at 150ºC

Melt Blending with Thermoplastic Starch 9

Blending TPS with synthetic polymers have shown the typical characteristics of immiscible polymer blends (St-Pierre et al, 1997). The melt blending of TPS with synthetic polymers has given place to a series of scientific and technologic developments. Such works differed in the mixing protocol and the type of additives used. Some authors proposed the use of two steps for the preparation of TPS-based blends (Aburto et al., 1997, Bikiaris et al., 1997a, 1997b, 1998, Prinos et al., 1998, Averous et al., 2000a, 2000b, 2001a, 2001b, Martin & Averous, 2001) while other preferred just one-step processes (Dehennau & Depireux, 1993, St-Pierre et al., 1997). Starch-based blends prepared in two steps are generally characterized for the preparation of TPS in a separated extrusion step. St-Pierre and coworkers presented a one-step blending process for TPS-based polymer blends (St-Pierre et al., 1997). They developed an extrusion system combining a TSE with a singlescrew extruder (SSE). TPS was prepared in the SSE, and then it was blended with LDPE in the last sections of the TSE. Using such an extrusion system, they demonstrated experimentally that a certain morphological control of PE/TPS blends could be achieved by varying the TPS concentration from 0 to 22 wt%. Those blends showed an unusual

Fig. 5. Schematic representation of the one-step extrusion system designed for the melt

An improved approach for LDPE/TPS blends in a one-step process was developed by Rodriguez-Gonzalez and coworkers (Rodriguez-Gonzalez et al., 2003b). It consisted of an extrusion system equipped with a single-screw extruder, from which molten LDPE is fed to the middle section of a twin-screw extruder. Suspensions of starch, glycerol and water were

**4. Blending with polyethylene** 

high level of ductility.

blending of LDPE with water-free TPS.

TPS exhibits the rheological behavior of a typical gel as characterized by a storage modulus (G', Figure 4a) larger than the loss modulus (G", Figure 4b) and with both moduli largely independent of frequency over the amplitude of the experimental window (Ross-Murphy, 1995). This behavior is produced by the presence of an elastic network embedded in a softer matrix. The rigidity in those regions can be produced by chemical or physical crosslinking. The structure of the elastic network has been related to the crystallinity derived from the complexation reaction between amylose and lipids (Conde-Petit & Escher, 1995; Della Valle et al., 1998) and the physical entanglement of the high molecular weight polysaccharides (Della Valle et al., 1998; Ruch and Fritz, 2000).

As expected, the augmentation of the glycerol content in TPS results in a reduction of both G' and G". However, the trend in the modulus curves was nearly the same, regardless of the glycerol content. From the study of low-concentration starch dispersions, Conde-Petit and Escher (1995) showed that the formation of amylose-emulsifier complexes modifies the viscoelastic response of potato starch dispersions. Crystalline regions produced during the amylose-emulsifier complexation form an elastic network, which is responsible for the liquid-like to solid-like viscoelastic modification. From the similarity of the trend of the G' curves shown in Figure 4a, it can be inferred in this work that glycerol variation does not affect the nature of the hypothetical crystalline elastic network, it just plasticizes the amorphous fraction of starch.

The study of the viscoelasticity of starch-based materials has mainly focused on concentrated gels and dispersions ( 5% starch). In this work, the viscoelastic behavior of water-free TPS at high glycerol contents has been evaluated at 150°C. G' decreases as glycerol content increases and the changes are similar at both low and high frequencies. Della Valle and co-workers also studied the behavior of a water-free TPS at 150°C and found that the decrease of G' with glycerol content was dependent on frequency (Della Valle et al., 1998). However, that material was obtained by subjecting the TPS to a separate drying step, a process which can induce structural changes in the starch. The proportional reduction of G' as a function of glycerol content observed in this work is similar to that observed in starch gel systems (Kulicke et al., 1996). Figure 6a shows that the reduction of the glycerol content from 40% to 33% results in a quasi-linear increment of G', while the reduction from 33% to 29% glycerol produces a larger variation in G'. In the case of the elastic modulus of polymer composites, percolation theory explains the non-linearity produced by the phase inversion effect at high filler content (Willett, 1994). The limit of glycerol plasticization that produces the non-linearity observed in the G' of TPS at a concentration around 30% glycerol can be explained in a similar way. TPS can be considered as a homogeneous system composed of a hard elastic network and soft amorphous regions. Amylose complex crystallites, highly entangled starch molecules, poorly plasticized starch-rich sites, or a combination of them could compose the hard elastic network. Soft amorphous regions could be composed of well-plasticized glycerol-rich starch. Even though the elastic network is present at 33% glycerol, the soft amorphous regions dominate the viscoelastic response. Increasing glycerol content, beyond this concentration, produces a relatively small reduction in the rheological parameters. On the other hand, below 30% glycerol the phase inversion of a soft to a hard matrix occurs resulting in the domination of the viscoelastic response by the hard elastic network, which is in good agreement with percolation theory. That suggests a glycerol plasticization threshold at a concentration around 30%.

TPS exhibits the rheological behavior of a typical gel as characterized by a storage modulus (G', Figure 4a) larger than the loss modulus (G", Figure 4b) and with both moduli largely independent of frequency over the amplitude of the experimental window (Ross-Murphy, 1995). This behavior is produced by the presence of an elastic network embedded in a softer matrix. The rigidity in those regions can be produced by chemical or physical crosslinking. The structure of the elastic network has been related to the crystallinity derived from the complexation reaction between amylose and lipids (Conde-Petit & Escher, 1995; Della Valle et al., 1998) and the physical entanglement of the high molecular weight polysaccharides

As expected, the augmentation of the glycerol content in TPS results in a reduction of both G' and G". However, the trend in the modulus curves was nearly the same, regardless of the glycerol content. From the study of low-concentration starch dispersions, Conde-Petit and Escher (1995) showed that the formation of amylose-emulsifier complexes modifies the viscoelastic response of potato starch dispersions. Crystalline regions produced during the amylose-emulsifier complexation form an elastic network, which is responsible for the liquid-like to solid-like viscoelastic modification. From the similarity of the trend of the G' curves shown in Figure 4a, it can be inferred in this work that glycerol variation does not affect the nature of the hypothetical crystalline elastic network, it just plasticizes the

The study of the viscoelasticity of starch-based materials has mainly focused on concentrated gels and dispersions ( 5% starch). In this work, the viscoelastic behavior of water-free TPS at high glycerol contents has been evaluated at 150°C. G' decreases as glycerol content increases and the changes are similar at both low and high frequencies. Della Valle and co-workers also studied the behavior of a water-free TPS at 150°C and found that the decrease of G' with glycerol content was dependent on frequency (Della Valle et al., 1998). However, that material was obtained by subjecting the TPS to a separate drying step, a process which can induce structural changes in the starch. The proportional reduction of G' as a function of glycerol content observed in this work is similar to that observed in starch gel systems (Kulicke et al., 1996). Figure 6a shows that the reduction of the glycerol content from 40% to 33% results in a quasi-linear increment of G', while the reduction from 33% to 29% glycerol produces a larger variation in G'. In the case of the elastic modulus of polymer composites, percolation theory explains the non-linearity produced by the phase inversion effect at high filler content (Willett, 1994). The limit of glycerol plasticization that produces the non-linearity observed in the G' of TPS at a concentration around 30% glycerol can be explained in a similar way. TPS can be considered as a homogeneous system composed of a hard elastic network and soft amorphous regions. Amylose complex crystallites, highly entangled starch molecules, poorly plasticized starch-rich sites, or a combination of them could compose the hard elastic network. Soft amorphous regions could be composed of well-plasticized glycerol-rich starch. Even though the elastic network is present at 33% glycerol, the soft amorphous regions dominate the viscoelastic response. Increasing glycerol content, beyond this concentration, produces a relatively small reduction in the rheological parameters. On the other hand, below 30% glycerol the phase inversion of a soft to a hard matrix occurs resulting in the domination of the viscoelastic response by the hard elastic network, which is in good agreement with percolation theory. That suggests a

glycerol plasticization threshold at a concentration around 30%.

(Della Valle et al., 1998; Ruch and Fritz, 2000).

amorphous fraction of starch.

### **4. Blending with polyethylene**

Blending TPS with synthetic polymers have shown the typical characteristics of immiscible polymer blends (St-Pierre et al, 1997). The melt blending of TPS with synthetic polymers has given place to a series of scientific and technologic developments. Such works differed in the mixing protocol and the type of additives used. Some authors proposed the use of two steps for the preparation of TPS-based blends (Aburto et al., 1997, Bikiaris et al., 1997a, 1997b, 1998, Prinos et al., 1998, Averous et al., 2000a, 2000b, 2001a, 2001b, Martin & Averous, 2001) while other preferred just one-step processes (Dehennau & Depireux, 1993, St-Pierre et al., 1997). Starch-based blends prepared in two steps are generally characterized for the preparation of TPS in a separated extrusion step. St-Pierre and coworkers presented a one-step blending process for TPS-based polymer blends (St-Pierre et al., 1997). They developed an extrusion system combining a TSE with a singlescrew extruder (SSE). TPS was prepared in the SSE, and then it was blended with LDPE in the last sections of the TSE. Using such an extrusion system, they demonstrated experimentally that a certain morphological control of PE/TPS blends could be achieved by varying the TPS concentration from 0 to 22 wt%. Those blends showed an unusual high level of ductility.

Fig. 5. Schematic representation of the one-step extrusion system designed for the melt blending of LDPE with water-free TPS.

An improved approach for LDPE/TPS blends in a one-step process was developed by Rodriguez-Gonzalez and coworkers (Rodriguez-Gonzalez et al., 2003b). It consisted of an extrusion system equipped with a single-screw extruder, from which molten LDPE is fed to the middle section of a twin-screw extruder. Suspensions of starch, glycerol and water were

Melt Blending with Thermoplastic Starch 11

Fig. 6. Effect of glycerol content and LDPE viscosity on the morphology of microtomed PE/TPS (70/30) blends. PE1/TPS blends: a) 40% glycerol, b) 36% glycerol, and c) 29% glycerol. d) PE2/TPS at 29% glycerol content. The black bar below the micrographs

represents 10m.

fed to the hopper of the twin-screw extruder and, as described in section 3, water-free TPS having 29, 36 and 40% glycerol (TPS29, TPS36 and TPS40, respectively) were prepared and melt blended with the LDPE as depicted in Figure 5. In order to evaluate the effect of PE and TPS viscosities on the morphology of LDPE/TPS blends two commercial LDPE resins, LDPE2040 (PE1, MFI = 12g/10min) and LDPE2049 (PE2, MFI = 20g/10min), and the three TPS were used.
