**3.2 Characterization of TPCF material**

The material was obtained by manual molding technique. To determine the operating conditions, we developed an experimental factorial design as shown in Table 1. The results of this design, indicated that there were significant differences among the factors evaluated (p <0.05), so an response surface analysis was developed using the software matlab (R2008a) to determine the process conditions: the content of plasticizer, drying time and particle size of cassava flour. Figures 4 and 5 show the results of the analysis.


Table 1. Experimental design moulded material process

Response surface analysis established that the particle size of 600 microns was the one who reported the highest value on the strength of tensile strength of the material, the same way, drying times above 20 hours at 45°C, interacting with a content of 15% plasticizer favor mechanical properties in tension, bearing in mind that this property is important because it will identify the functional applications of the material.

Figures 4 and 5 show the optimization of the variables evaluated (drying time, particle size and concentration of plasticizer). This optimization is valuable because it indicates the values of variables in which the response evaluated had the highest value. Small particle sizes cassava flour could be contributing to a greater absorption of water by the increased free volume between particles, which probably caused a lower response to stress. Water acts as a plasticizer, resulting in intermolecular mobility, therefore, a drier material (longer drying time), the higher rigidity and resistance to a tensile stress.

Some of the techniques to characterize the material valued based TPCF were:

The samples showed a peak at 2θ: 20°, which according to Zobel (1988, quoted in Singh, 2006), is attributed to the presence of amylose-lipid complexes in starches, whose intensity could be related to the proportion of them. There were strong peaks at 2θ: 15°, 2θ: 17°, 2θ: 18° and 2θ: 23°, characteristic of type A pattern (Van Soest et al., 1996; Cheetham & Tao , 1998; Rodriguez et al., 2007; Leblanc et al. 2008; Perdomo et al, 2009), which indicates that

The material was obtained by manual molding technique. To determine the operating conditions, we developed an experimental factorial design as shown in Table 1. The results of this design, indicated that there were significant differences among the factors evaluated (p <0.05), so an response surface analysis was developed using the software matlab (R2008a) to determine the process conditions: the content of plasticizer, drying time and particle size

Factor Level Response

High:25 Low: 10 Center: 17.5

High: 26 Low: 8 Center: 17

High: 600 Low: 250 Center: 425

Response surface analysis established that the particle size of 600 microns was the one who reported the highest value on the strength of tensile strength of the material, the same way, drying times above 20 hours at 45°C, interacting with a content of 15% plasticizer favor mechanical properties in tension, bearing in mind that this property is important because it

Figures 4 and 5 show the optimization of the variables evaluated (drying time, particle size and concentration of plasticizer). This optimization is valuable because it indicates the values of variables in which the response evaluated had the highest value. Small particle sizes cassava flour could be contributing to a greater absorption of water by the increased free volume between particles, which probably caused a lower response to stress. Water acts as a plasticizer, resulting in intermolecular mobility, therefore, a drier

material (longer drying time), the higher rigidity and resistance to a tensile stress.

Some of the techniques to characterize the material valued based TPCF were:

Tensile strenght (MPa)

the crystalline arrangement is monocyclic.

**3.2 Characterization of TPCF material** 

of cassava flour. Figures 4 and 5 show the results of the analysis.

Plasticizer content (%)

Drying time at 45°C (hours)

Particle size of cassava flour (µm)

Table 1. Experimental design moulded material process

will identify the functional applications of the material.

Fig. 4. Response surface of TPCF material with particle size 250 µm

Fig. 5. Response surface of TPCF material with particle size 600 µm

Thermoplastic Cassava Flour 33

second heating in polylactide films samples mixed with thermoplastic cassava starch extruded (Lee, Chen & Hanna, 2008). Possibly, the material molecules can not organize freely during cooling, maybe because they require a much slower process for ordering, which resulted in no evidence of the glass transition and fusion of material on third cycle, further, cooling after first heating is probably causing irreversible structural changes and transformations at the molecular level, which prevents phase transitions evident in the first

In Figure 6, can be seen that the glass transition temperature is above 110°C, this is an indication of the high stability of the material, since in future applications, it may be subjected to temperatures near 100°C maintaining its stability because it is in their glassy solid state.

TGA equipment was used (Q50, TA Instruments). Samples between 10 and 20 mg were assessed of molded material, according the ASTM E1131-08. The sample was placed in a platinum tray open and subjected to heating from 25°C to 500°C at a rate of 10°C/min. The

299.28°C

73.49%

Temperature (°C) Universal V4.5A TA Instruments

0.0

0.2

0.4

0.6

Deriv. Weight (%/°C)

0.8

1.0

The TGA curve has four main areas, namely: the area of highly volatile material (200°C or less) represented by moisture, plasticizers, residual solvents and other components of low boiling point, the material area average volatility (between 200 and 750°C) represented by compounds of polymer degradation, oil; area where combustible material degrades oxidized material such as coal nonvolatile (temperature depends on the material), and the area of ash corresponds to non-volatile residue in an oxidizing atmosphere including metal components, inert fillers or reinforcements (ASTM E1131). Figure 7 shows the first two zones in the TGA curve, represented by 7.820% in highly volatile material, and the area

0 100 200 300 400 500

tests were carried out in a controlled environment using nitrogen level UAP.

7.820%

heating cycle, but it was evident by the second one.

**3.2.2 Thermogravimetric Analysis - TGA** 

Fig. 7. Termogram TGA material of TPCF

0

20

40

60

Weight (%)

80

100

#### **3.2.1 Differential scanning calorimetry**

Samples were evaluated according to ASTM D3418-08 applied to the analysis of polymeric materials, with some modifications. Equipment used was a DSC (TA Instruments, Q20, USA). The samples were stored in hermetically sealed aluminum pans and subjected to heating from -50°C to 225°C at a heating rate of 20°C/min, then cooling to -50°C and a final heating similar to the first.

Figure 6 shows the three cycles that were submitted material samples in DSC. In the first heating scan showed a first endothermic peak before 0°C, then a glass transition and a second endothermic peak of melting of the material close to 150°C. Sample was then cooled with the drop from the flow of heat and finally heated in the third cycle, evidencing only an endothermic peak below 0°C, as presented in the first cycle.

Fig. 6. Termogram DSC material of TPCF

The first scan was performed to remove the thermal history of material, that is, to prevent abnormal results because thermal processes to which the material was subjetc, which can alter the phase transitions characteristic of the sample, so it is expected that with the initial heating the material molecules were casted, and then, with the cooling the material molecules get to organize freely (second cycle) to obtain the real phase transitions of the material in the third cycle. No clutch, the first cycle performed (Figure 6) shows the typical transitions of the material, which was not presented in the third or second heating cycle, as usually (Mohamed et al, 2010). Some authors report that the Tg (glass transition temperature) was obtained only in the first heating, and melting temperature in the first and

Samples were evaluated according to ASTM D3418-08 applied to the analysis of polymeric materials, with some modifications. Equipment used was a DSC (TA Instruments, Q20, USA). The samples were stored in hermetically sealed aluminum pans and subjected to heating from -50°C to 225°C at a heating rate of 20°C/min, then cooling to -50°C and a final

Figure 6 shows the three cycles that were submitted material samples in DSC. In the first heating scan showed a first endothermic peak before 0°C, then a glass transition and a second endothermic peak of melting of the material close to 150°C. Sample was then cooled with the drop from the flow of heat and finally heated in the third cycle, evidencing only an

The first scan was performed to remove the thermal history of material, that is, to prevent abnormal results because thermal processes to which the material was subjetc, which can alter the phase transitions characteristic of the sample, so it is expected that with the initial heating the material molecules were casted, and then, with the cooling the material molecules get to organize freely (second cycle) to obtain the real phase transitions of the material in the third cycle. No clutch, the first cycle performed (Figure 6) shows the typical transitions of the material, which was not presented in the third or second heating cycle, as usually (Mohamed et al, 2010). Some authors report that the Tg (glass transition temperature) was obtained only in the first heating, and melting temperature in the first and

**3.2.1 Differential scanning calorimetry** 

Fig. 6. Termogram DSC material of TPCF

endothermic peak below 0°C, as presented in the first cycle.

heating similar to the first.

second heating in polylactide films samples mixed with thermoplastic cassava starch extruded (Lee, Chen & Hanna, 2008). Possibly, the material molecules can not organize freely during cooling, maybe because they require a much slower process for ordering, which resulted in no evidence of the glass transition and fusion of material on third cycle, further, cooling after first heating is probably causing irreversible structural changes and transformations at the molecular level, which prevents phase transitions evident in the first heating cycle, but it was evident by the second one.

In Figure 6, can be seen that the glass transition temperature is above 110°C, this is an indication of the high stability of the material, since in future applications, it may be subjected to temperatures near 100°C maintaining its stability because it is in their glassy solid state.

#### **3.2.2 Thermogravimetric Analysis - TGA**

TGA equipment was used (Q50, TA Instruments). Samples between 10 and 20 mg were assessed of molded material, according the ASTM E1131-08. The sample was placed in a platinum tray open and subjected to heating from 25°C to 500°C at a rate of 10°C/min. The tests were carried out in a controlled environment using nitrogen level UAP.

Fig. 7. Termogram TGA material of TPCF

The TGA curve has four main areas, namely: the area of highly volatile material (200°C or less) represented by moisture, plasticizers, residual solvents and other components of low boiling point, the material area average volatility (between 200 and 750°C) represented by compounds of polymer degradation, oil; area where combustible material degrades oxidized material such as coal nonvolatile (temperature depends on the material), and the area of ash corresponds to non-volatile residue in an oxidizing atmosphere including metal components, inert fillers or reinforcements (ASTM E1131). Figure 7 shows the first two zones in the TGA curve, represented by 7.820% in highly volatile material, and the area

Thermoplastic Cassava Flour 35

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average volatility material that starts at 134.89°C and ends at 470.6°C and a residue of 18.69%. The degradation temperature (Td) for the material presented was 299.28°C, meaning adequate thermal stability, comparable with thermoplastic cassava starch nanoreforced. Td which occurred between 309 and 327°C (Schlemmer, Angelica & Sales, 2010), and compounds near extruded and injection molded thermoplastic starch reinforced with lignocellulosic fibers whose degradation temperatures were between 335 and 339°C (Averous & Boquillon, 2004).
