3. Results and discussion

The physical gel was irradiated in Dynamitron electron beam, with energy of 1.5 MeV, with a dose of 25 kGy and a dose rate of 11.3 kGy/s, which promoted the formation of the cross-links

PSB0 0 0 0 0 0 3 3 PVP 10 10 2.5 2.5 2.5 2.5 2.5 2.5 PVAl 0 0 7.5 7.5 7.5 7.5 7.5 7.5 Chitosan 0 0 0 0 1 1 1 1 PEG3 3 3 3 3 3 3 3 Agar1 3 1 3 1 3 1 3 Water 86 84 86 84 85 83 82 80

Comp. 1 Comp. 2 Comp. 3 Comp. 4 Comp. 5 Comp. 6 Comp. 7 Comp. 8

Hydrogels were characterized by visual test, mechanical test, gel fraction, thermal properties

• Mechanical test: Tensile strength tests for the hydrated membrane were performed in a dynamometer of the Q-Test, model 65 J at 25 mm/min (ABNT-NBR 6241/80, with speci-

• Sol-gel fraction: The samples were washed in Soxhlet extractors with boiling water for 36 h. The obtained gels were dried until reaching constant weight. The gel fraction was deter-

• Swelling: The samples were maintained in water for 240 h. The water absorption was checked every hour step in the first 24 h. After that, each measurement was performed using 24-h steps until reaching constant weight. The hydration grade was determined by

• Thermal properties (DTA, TG and DTMA): Thermal analyses were performed by the Netzsch Thermische Analyze STA 409 equipment. The rate used in DTA and TG analysis was 10�C/min from ambient temperature until 600�C with 40 mL/min nitrogen flow. The

Sol � gel fraction wt ð Þ¼ % ð Þ� Wfg=Wi 100 (1)

Swelling wt ð Þ¼ % ½ð Þ Wfs � Wi =Wi� � 100 (2)

mined in relation to the initial weight of the sample according to Eq. (1).

where Wfg = final weight (after drying); and Wi = initial weight of the sample.

the difference of the weight before and after swelling according to Eq. (2).

where Wfs = final weight (after swelling); and Wi = initial weight of the sample.

and also the sterilization of the material.

Materials Compositions (wt%)

2.2.1. Characterization of hydrogels

Table 1. Membranes composition.

and swelling.

144 Hydrogels

men type I).

Visual characterization: Figure 1 shows the obtained membranes with 25 kGy dose.

The membranes with the compositions 1, 2, 3 and 4 (Figure 1) are transparent, while others are translucent and slightly yellowish. Therefore, the presence of chitosan makes the hydrogels less transparent.

In the membranes with the compositions 1, 2, 3 and 4 were firm and without bubbles, the membranes of compositions 5, 6, 7 and 8 showed a greater adhesion or tack due to the presence of chitosan (Figure 1).

Tensile strength: Table 2 and Figures 2 and 3 present the results to the tensile strength tests to 7 days after irradiation.

The results show that comparing the obtained hydrogels, the Comp. 4 (based on PVP/PVAl/ 3wt% agar) and Comp. 3 (based on PVP/PVAl/chitosan/3wt% agar) (Figure 2) showed higher tensile strength and higher elongation.

The hydrogels Comp. 1 (PVP/1wt% agar), Comp. 2 (PVP/3wt% agar), Comp. 7 (PVP/PVAl/ chitosan/PBS/1wt% agar) and Comp. 8 (PVP/PVAl/chitosan/PSB)/3wt% agar) exhibit lower tensile strength (Figure 2).

The Comp. 2 hydrogels (PVP/3 wt% agar) (Figure 3) show the smallest elongation.


Figure 1. Comp. 1 (PVP/1wt% agar); Comp. 2 (PVP/3 wt% agar); Comp. 3 (PVP/PVAl/1 wt% agar); Comp. 4 (PVP/PVAl/ 3wt% agar), Comp. 5 (PVP/PVAl/chitosan/1 wt% agar), Comp. 6 (PVP/PVAl/chitosan/3wt% agar); Comp. 7 (PVP/PVAl/ chitosan/PSB)/1wt% agar) and Comp. 8 (PVP/PVAl/chitosan/PSB/3 wt% agar).


The hydrogels containing pseudoboehmite presented lower results of tensile strength and

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Probably, the amount of pseudoboehmite present absorbs part of the free radicals during the

Sol-gel fraction: Table 3 and the Figure 4 present the results obtained for the sol-gel fraction.

By results obtained in Table 3 and Figure 4, it is observed that the hydrogels obtained with compositions 5, 6 and 7, containing PVAl, chitosan and pseudoboehmite, presented the smallest percentage of gel fraction. The presence of PVAl, chitosan and pseudoboehmite, probably, absorb part of the free radicals during the irradiation process, decreasing the formation of cross-links. The hydrogels obtained with compositions 1 and 3 presented the highest percentages of gel fraction, although the conventional composition containing PVP/agar had a higher percentage

Hydrogels Sol fraction (%) Gel fraction (%)

Comp.1 Comp.2 Comp.3 Comp.4 Comp.5 Comp.6 Comp.7 Comp.8

Sol Frac�on Gel Frac�on

Comp. 1 (PVP /1wt% agar) 15.37 84.63 Comp. 2 (PVP/3wt% agar) 43.27 56.73 Comp. 3 (PVP/PVAl/1wt% agar) 30.99 69.01 Comp. 4 (PVP/PVAl/3wt% agar) 44.38 55.52 Comp. 5 (PVP/PVAl/chitosan/1wt% agar) 54.05 45.95 Comp. 6 (PVP/PVAl/chitosan/3wt% agar) 61.85 38.15 Comp. 7 (PVP/PVAl/chitosan/PSB/1wt% agar) 57.53 42.47 Comp. 8 (PVP/PVAl/chitosan/PSB/3wt% agar) 44.63 55.37

lower results for elongation at rupture (Table 2; Figures 2 and 3).

irradiation process by decreasing the formation of cross-links.

of gel fraction than those containing PVP/agar/PVAl (Figure 4).

The values obtained are the average of 16 experiments.

Table 3. Results obtained for sol-gel fraction.

0.00

Figure 4. Results obtained for sol-gel fraction.

20.00

40.00

**Sol/Gel Fraction(%)** 

60.00

80.00

100.00

\*

\*The values obtained are the average of 16 experiments.

Table 2. Results of the tensile strength tests.

Figure 2. Results of the tensile strength.

Figure 3. Results of elongation at rupture (%).

In general, hydrogels containing 3 wt% of agar in the composition, presented higher tensile strength and elongation at break, than their versions containing 1 wt% of agar (Table 2; Figures 2 and 3).

The data show that the association of chitosan with the increasing percentage of agar may have favored the elongation of the hydrogels (Figure 3);

The hydrogels containing pseudoboehmite presented lower results of tensile strength and lower results for elongation at rupture (Table 2; Figures 2 and 3).

Probably, the amount of pseudoboehmite present absorbs part of the free radicals during the irradiation process by decreasing the formation of cross-links.

Sol-gel fraction: Table 3 and the Figure 4 present the results obtained for the sol-gel fraction.

By results obtained in Table 3 and Figure 4, it is observed that the hydrogels obtained with compositions 5, 6 and 7, containing PVAl, chitosan and pseudoboehmite, presented the smallest percentage of gel fraction. The presence of PVAl, chitosan and pseudoboehmite, probably, absorb part of the free radicals during the irradiation process, decreasing the formation of cross-links.

The hydrogels obtained with compositions 1 and 3 presented the highest percentages of gel fraction, although the conventional composition containing PVP/agar had a higher percentage of gel fraction than those containing PVP/agar/PVAl (Figure 4).


\* The values obtained are the average of 16 experiments.

Table 3. Results obtained for sol-gel fraction.

Figure 4. Results obtained for sol-gel fraction.

In general, hydrogels containing 3 wt% of agar in the composition, presented higher tensile strength and elongation at break, than their versions containing 1 wt% of agar (Table 2;

Hydrogels Tensile strength (MPa) Elongation at rupture (%)

Comp. 1 (PVP/1wt% agar) 0.016 0.006 136.29 Comp. 2 (PVP/3wt% agar) 0.022 0.006 42 8 Comp. 3 (PVP/PVAl/1wt% agar) 0.108 0.007 490 70 Comp. 4 (PVP/PVAl/3wt% agar) 0.232 0.020 568 83 Comp. 5 (PVP/PVAl/chitosan/1wt% agar) 0.054 0.008 289 55 Comp. 6 (PVP/PVAl/chitosan/3wt% agar) 0.046 0.005 496 19 Comp. 7 (PVP/PVAl/chitosan/PSB/1wt% agar) 0.012 0.007 227 22 Comp. 8 (PVP/PVAl/chitosan/PSB/3wt% agar) 0.027 0.007 339 24

The data show that the association of chitosan with the increasing percentage of agar may have

Figures 2 and 3).

favored the elongation of the hydrogels (Figure 3);

**Enloga�on at rupture(%)** 

Figure 3. Results of elongation at rupture (%).

0.00 0.05 0.10 0.15 0.20 0.25 0.30

\*The values obtained are the average of 16 experiments.

**Tensile strength (Mpa)** 

Table 2. Results of the tensile strength tests.

146 Hydrogels

Figure 2. Results of the tensile strength.

Comparing the hydrogels containing PVP/agar/PVAl with the hydrogels containing PVP/agar/ PVAl/chitosan and PVP/agar/PVAl/chitosan/PSB, it is observed that the first have higher gel fraction indicating that the PVAl, probably absorbs a smaller part of the free radicals during the irradiation process than the chitosan and the pseudoboehmite (Figure 4).

The hydrogels obtained with compositions 2, 4 and 8 presented intermediate percentages of gel fraction. When comparing the agar concentration in the samples, it is observed that the increase in the agar concentration increases the gel fraction. Probably, the agar promotes the increase of the cross-link formation (Figure 4).

Comparing the results obtained for the gel fraction of the hydrogels containing chitosan and pseudoboehmite with those containing only one of these components, the values obtained were intermediates, indicating that these compounds acted independently of one another (Figure 4).

The Comp. 6 presents higher gel fraction. This sample does not contain pseudoboehmite in the composition (Figure 4).

the hydrogels of similar composition only with variation in composition of 3 wt% agar, the increase in swelling percentage was significant. Probably, this difference is due to the presence of agar in a higher concentration that causes a greater absorption of water in the hydrogel

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comp.1 comp.2 comp.3 comp.4 comp.5 comp.6 comp.7 comp.8

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The hydrogels containing PVP and PVAl, chitosan, Comp. 5 and Comp. 6 had low percentages of swelling after 7 days of irradiation (Figure 5), and the increase was not representative for the tests after 30 days of irradiation (Figure 6). Probably, the chitosan avoid the posterior cross-link. The hydrogels containing PVP/PVAl/chitosan/PSB/1 wt% agar, Comp. 7, presented the highest percentage of swelling after 7 days of irradiation (Figure 5), but the increase was not significant after 30 days of irradiation (Figure 6). The hydrogels containing PVP/PVAl/chitosan/PBS/3 wt % agar, Comp. 8, presented low water absorption after 7 days of irradiation and significant

DTA and TG: The DTA and TG results for the obtained hydrogels are shown in Figures 7–11. The results show that for the Comp. 1 hydrogels, containing PVP as the matrix, it can be observed that the PVP melts at a lower temperature, decreases the Tm and its degradation. For this composition, the Tg did not show considerable variation in relation to the pure PVP,

For the Comp. 2 hydrogels, where the matrix is also PVP, containing a higher percentage of agar, there was a decrease in Tg. PVP molecules have probably gained greater mobility at a lower temperature. However, Tm occurred at a higher temperature, indicating that degradation in the PVP molecules present in the hydrogel probably occurred. An increase occurred in

For the Comp. 3 hydrogels, where the PVAl is found in greater proportion, the molecules gained greater mobility at lower temperature, that is, it decreased the Tg and the fusion occurred at lower temperature, and also, it decreased the Tm (Figure 8). The same occurred for the Comp. 4 hydrogels with PVP and PVAl matrix and 3 wt% agar (Figure 8), that compared with the other samples, the molecules gained greater mobility at lower temperature,

structure because probably the agar promotes the increase of the cross-link formation.

0 24 48 72 96 120 144 168 192 216

**Time (Hours)** 

Figure 6. Results obtained for swelling tests of the hydrogels obtained after 30 days of the irradiation.

increase after 30 days of being irradiated (Figures 5 and 6).

and also its degradation temperature (Figure 7).

**Swelling (%)** 

temperature of degradation was observed (Figure 7).

Swelling: Swelling tests were performed for 7 and 30 days after irradiation of the hydrogels. Figures 5 and 6 show the results obtained for the swelling tests.

The results show that hydrogels presented higher percentages of swelling after 30 days of irradiation (Figures 5 and 6).

The hydrogels based on only PVP and agar (Comp. 1 and Comp. 2) had a low swelling percentage after 7 days of irradiation (Figure 5), and after 30 days of irradiation had a significant increase in swelling percentage (Figure 6). Probably, some macroradicals are recombined during this stage.

For the PVP/PVAl/1 wt% Agar (Comp. 3) hydrogels, the swelling percentage was low after 7 days of irradiation and remained low after 30 days of irradiation (Figures 5 and 6). While for

Figure 5. Results obtained for swelling tests of the hydrogels obtained after 7 days of the irradiation.

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Figure 6. Results obtained for swelling tests of the hydrogels obtained after 30 days of the irradiation.

Comparing the hydrogels containing PVP/agar/PVAl with the hydrogels containing PVP/agar/ PVAl/chitosan and PVP/agar/PVAl/chitosan/PSB, it is observed that the first have higher gel fraction indicating that the PVAl, probably absorbs a smaller part of the free radicals during

The hydrogels obtained with compositions 2, 4 and 8 presented intermediate percentages of gel fraction. When comparing the agar concentration in the samples, it is observed that the increase in the agar concentration increases the gel fraction. Probably, the agar promotes the

Comparing the results obtained for the gel fraction of the hydrogels containing chitosan and pseudoboehmite with those containing only one of these components, the values obtained were intermediates, indicating that these compounds acted independently of one another

The Comp. 6 presents higher gel fraction. This sample does not contain pseudoboehmite in the

Swelling: Swelling tests were performed for 7 and 30 days after irradiation of the hydrogels.

The results show that hydrogels presented higher percentages of swelling after 30 days of

The hydrogels based on only PVP and agar (Comp. 1 and Comp. 2) had a low swelling percentage after 7 days of irradiation (Figure 5), and after 30 days of irradiation had a significant increase in swelling percentage (Figure 6). Probably, some macroradicals are

For the PVP/PVAl/1 wt% Agar (Comp. 3) hydrogels, the swelling percentage was low after 7 days of irradiation and remained low after 30 days of irradiation (Figures 5 and 6). While for

> comp.1 comp.2 comp.3 comp.4 comp.5 comp.6 comp.7 comp.8

0 24 48 72 96 120 144 168 192 216

**Time (Hours)** 

Figure 5. Results obtained for swelling tests of the hydrogels obtained after 7 days of the irradiation.

the irradiation process than the chitosan and the pseudoboehmite (Figure 4).

increase of the cross-link formation (Figure 4).

Figures 5 and 6 show the results obtained for the swelling tests.

(Figure 4).

148 Hydrogels

composition (Figure 4).

irradiation (Figures 5 and 6).

recombined during this stage.

0

50

100

150

**Swelling (%)** 

200

250

300

the hydrogels of similar composition only with variation in composition of 3 wt% agar, the increase in swelling percentage was significant. Probably, this difference is due to the presence of agar in a higher concentration that causes a greater absorption of water in the hydrogel structure because probably the agar promotes the increase of the cross-link formation.

The hydrogels containing PVP and PVAl, chitosan, Comp. 5 and Comp. 6 had low percentages of swelling after 7 days of irradiation (Figure 5), and the increase was not representative for the tests after 30 days of irradiation (Figure 6). Probably, the chitosan avoid the posterior cross-link.

The hydrogels containing PVP/PVAl/chitosan/PSB/1 wt% agar, Comp. 7, presented the highest percentage of swelling after 7 days of irradiation (Figure 5), but the increase was not significant after 30 days of irradiation (Figure 6). The hydrogels containing PVP/PVAl/chitosan/PBS/3 wt % agar, Comp. 8, presented low water absorption after 7 days of irradiation and significant increase after 30 days of being irradiated (Figures 5 and 6).

DTA and TG: The DTA and TG results for the obtained hydrogels are shown in Figures 7–11.

The results show that for the Comp. 1 hydrogels, containing PVP as the matrix, it can be observed that the PVP melts at a lower temperature, decreases the Tm and its degradation. For this composition, the Tg did not show considerable variation in relation to the pure PVP, and also its degradation temperature (Figure 7).

For the Comp. 2 hydrogels, where the matrix is also PVP, containing a higher percentage of agar, there was a decrease in Tg. PVP molecules have probably gained greater mobility at a lower temperature. However, Tm occurred at a higher temperature, indicating that degradation in the PVP molecules present in the hydrogel probably occurred. An increase occurred in temperature of degradation was observed (Figure 7).

For the Comp. 3 hydrogels, where the PVAl is found in greater proportion, the molecules gained greater mobility at lower temperature, that is, it decreased the Tg and the fusion occurred at lower temperature, and also, it decreased the Tm (Figure 8). The same occurred for the Comp. 4 hydrogels with PVP and PVAl matrix and 3 wt% agar (Figure 8), that compared with the other samples, the molecules gained greater mobility at lower temperature,

A B

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C D

A B

C D

Figure 9. (A) DTA of the PVP/PVAl/chitosan with 1 wt% of agar, (B) TG of the PVP/PVAl/chitosan with 1 wt% of agar, (C) DTA of the PVP/PVAl/chitosan with 3 wt% of agar and (D) TG of the PVP/PVAl/chitosan with 3 wt% of agar.

Figure 10. (A) DTA of the PVP/PVAl/chitosan/PSB with 1 wt% of agar; (B) TG of the PVP/PVAl/chitosan/PSB with 1 wt% of agar; (C) DTA of the PVP/PVAl/chitosan/PSB with 3 wt% of agar; and (D) TG of the PVP/PVAl/chitosan/PSB with 3 wt%

of agar.

Figure 7. (A) DTA of pure PVP with 1 wt% of agar, (B) TG of pure PVP with 1 wt% of agar, (C) DTA of pure PVP with 3 wt% of agar; (D) TG of pure PVP with 3 wt% of agar.

Figure 8. (A) DTA of the PVP/PVAl with 1 wt% of agar, (B) TG of the PVP/PVAl with 1 wt% of agar, (C) DTA of the PVP/ PVAl with 3 wt% of agar and (D) TG of the PVP/PVAl with 3 wt% of agar.

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A B

C D

A B

C D

Figure 7. (A) DTA of pure PVP with 1 wt% of agar, (B) TG of pure PVP with 1 wt% of agar, (C) DTA of pure PVP with 3

Figure 8. (A) DTA of the PVP/PVAl with 1 wt% of agar, (B) TG of the PVP/PVAl with 1 wt% of agar, (C) DTA of the PVP/

PVAl with 3 wt% of agar and (D) TG of the PVP/PVAl with 3 wt% of agar.

wt% of agar; (D) TG of pure PVP with 3 wt% of agar.

150 Hydrogels

Figure 9. (A) DTA of the PVP/PVAl/chitosan with 1 wt% of agar, (B) TG of the PVP/PVAl/chitosan with 1 wt% of agar, (C) DTA of the PVP/PVAl/chitosan with 3 wt% of agar and (D) TG of the PVP/PVAl/chitosan with 3 wt% of agar.

Figure 10. (A) DTA of the PVP/PVAl/chitosan/PSB with 1 wt% of agar; (B) TG of the PVP/PVAl/chitosan/PSB with 1 wt% of agar; (C) DTA of the PVP/PVAl/chitosan/PSB with 3 wt% of agar; and (D) TG of the PVP/PVAl/chitosan/PSB with 3 wt% of agar.

Figure 11. (A) DTAs and (B) TGs of the all compositions.

decreasing Tg and Tm at a lower temperature. It was observed that the decomposition occurred at a higher temperature for samples Comp. 3 and Comp. 4.

For membranes with composition 5 containing PVP/PVAl/chitosan/1 wt% agar, it was concluded that the water was not strongly retained and the molecules gained mobility at a lower temperature, decreasing Tg and Tm (Figure 9). However, the degradation was delayed, that is, it occurred at higher temperature than pure PVP (Figure 7(A) and (B)).

Figure 12. DMTA results of the Comp. 1 and Comp. 2.

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Figure 13. DMTA results of the Comp. 3 and Comp. 4.

For Comp. 6 hydrogels with PVP/PVAl/chitosan/3 wt% agar, it can be concluded that the addition of agar did not hinder the loss of water. However, the molecules gained mobility at higher temperature (Tg higher), and the melting temperature was almost the same as temperature of sample 5. However, the degradation was delayed, occurring at a higher temperature (Figure 9).

DMTA: The DMTA results for the obtained hydrogels are shown in Figures 12–15 and Table 4.

The results show that when comparing Comp. 1 and Comp. 2 hydrogels, the presence of a higher concentration of agar decreases the Tm value, causing an increase in the viscoelasticity of the material. This result can also be observed for the Comp. 4 hydrogels.

When comparing Comp. 1 and Comp. 3 hydrogels (Figures 12 and 13), the presence of PVAl causes an increase in Tm, and consequently, a decrease in the viscoelasticity of the material.

The presence of chitosan and pseudoboehmite in the hydrogels causes an increase in the Tm of the material, reducing its viscoelasticity (Figures 14 and 15). It is observed that the effect of chitosan is more effective in process. Probably, the chitosan structure, containing several hydroxyl groups (which may form hydrogen bonds), causes a bigger decrease in the viscoelasticity in the hydrogel of than the pseudoboehmite.

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Figure 12. DMTA results of the Comp. 1 and Comp. 2.

decreasing Tg and Tm at a lower temperature. It was observed that the decomposition

A B

For membranes with composition 5 containing PVP/PVAl/chitosan/1 wt% agar, it was concluded that the water was not strongly retained and the molecules gained mobility at a lower temperature, decreasing Tg and Tm (Figure 9). However, the degradation was delayed, that is,

For Comp. 6 hydrogels with PVP/PVAl/chitosan/3 wt% agar, it can be concluded that the addition of agar did not hinder the loss of water. However, the molecules gained mobility at higher temperature (Tg higher), and the melting temperature was almost the same as temperature of sample 5. However, the degradation was delayed, occurring at a higher temperature (Figure 9).

DMTA: The DMTA results for the obtained hydrogels are shown in Figures 12–15 and Table 4. The results show that when comparing Comp. 1 and Comp. 2 hydrogels, the presence of a higher concentration of agar decreases the Tm value, causing an increase in the viscoelasticity

When comparing Comp. 1 and Comp. 3 hydrogels (Figures 12 and 13), the presence of PVAl causes an increase in Tm, and consequently, a decrease in the viscoelasticity of the material.

The presence of chitosan and pseudoboehmite in the hydrogels causes an increase in the Tm of the material, reducing its viscoelasticity (Figures 14 and 15). It is observed that the effect of chitosan is more effective in process. Probably, the chitosan structure, containing several hydroxyl groups (which may form hydrogen bonds), causes a bigger decrease in the viscoelas-

occurred at a higher temperature for samples Comp. 3 and Comp. 4.

Figure 11. (A) DTAs and (B) TGs of the all compositions.

152 Hydrogels

it occurred at higher temperature than pure PVP (Figure 7(A) and (B)).

of the material. This result can also be observed for the Comp. 4 hydrogels.

ticity in the hydrogel of than the pseudoboehmite.

Figure 13. DMTA results of the Comp. 3 and Comp. 4.

4. Conclusion

more adherent;

rupture;

gation at rupture of hydrogels;

elongation of the membranes;

cross-link formation.

of irradiation;

According to the results, the conclusions are as follows

Table 4. Results obtained from Tm and tan δ of the studied hydrogels.

Hydrogel Tm (

pseudoboehmite nanoparticles in the studied concentrations;

• It is possible to obtain hydrogels based on PVP, PVAl and chitosan containing

Comp. 1 (PVP/1 wt% agar) 33.9 0.5752 Comp. 2 (PVP/3 wt% agar) 22.8 0.7540 Comp. 3 (PVP/PVAl/1 wt% agar) 38.7 0.4045 Comp. 4 (PVP/PVAl/3 wt% agar) 24.6 0.5202 Comp. 5 (PVP/PVAl/chitosan/1 wt% agar) 1.5 0.1953 Comp. 6 (PVP/PVAl/chitosan/3 wt% agar) 6.6 0.2439 Comp. 7 (PVP/PVAl/chitosan/PSB/1 wt% agar) 24.5 0.4280 Comp. 8 (PVP/PVAl/chitosan/PSB/3 wt% agar) 2.7 0.2699

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• The presence of chitosan makes the hydrogels less transparent and makes the hydrogels

• The association of chitosan with increasing percentage of agar promotes the higher elon-

• The hydrogels containing pseudoboehmite presented lower results of tensile strength and lower results for elongation at rupture. Probably, the pseudoboehmite absorbs part of the free radicals during the irradiation process by decreasing the formation of cross-links; • The presence of PVAl increases the tensile strength and causes higher elongation at the

• In general, membranes containing 3 wt% of agar in the composition presented higher tensile strength and higher elongation at break than their versions containing 1 wt% of agar; • The association of chitosan with increasing percentage of agar may have favored the

• How much bigger the concentration of agar in the hydrogel, higher is the tensile strength and the higher is the elongation at break. Probably, the agar promotes the increase of the

• The hydrogels containing PVAl, chitosan and pseudoboehmite presented the smallest percentage of gel fraction. The presence of PVAl, chitosan and pseudoboehmite, probably, absorb part of the free radicals during the irradiation process, decreasing the cross-links formation;

• All hydrogels' compositions studied showed higher percentages of swelling after 30 days

Figure 14. DMTA results of the Comp. 5 and Comp. 6.

Figure 15. DMTA results of the Comp. 7 and Comp. 8.


Table 4. Results obtained from Tm and tan δ of the studied hydrogels.
