# A Study of the Flexural Properties of PA12/Clay Nanocomposites

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Materials

^{3}according to DIN53466 0.435- [31].

#### 2.2. Design of Experiment

^{3}factorial points, 2 × 3 axial points, and 5 center points (Table 1).

#### 2.3. Preparation of Specimens

#### 2.4. Morphological and Structural Characterization

#### 2.5. Determination of Flexural Properties of PA12/Clay Nanocomposites

_{1}= 5 mm ± 0.1 mm and R

_{2}= 2 mm ± 0.2 mm were used for a test specimen with a thickness ≤ 3 mm, h = 2 mm, width of b = 25 mm, and length of l = 40 mm [37].

_{fM}is the maximum flexural stress that can be sustained by the test specimen during a bending test. This can be calculated using the equation:

_{fM}(MPa) is the maximum flexural stress, F

_{M}(N) is the maximum applied force, L (mm) is the span between supports (32 mm), b (mm) is the width of the specimen, and h (mm) is the thickness of the specimen.

_{f}is the ratio of the stress difference σ

_{f2}–σ

_{f1}to the corresponding strain difference, ε

_{f2}(= 0.25%)–ε

_{f1}(= 0.05%). It can be calculated using the equation:

_{f1}(MPa) is the flexural stress at deflection S

_{1}, σ

_{f2}(MPa) is the flexural stress at deflection S

_{2}, and ε

_{f}is the flexural strain (ε

_{f2}= 0.0025, ε

_{f1}= 0.0005).

_{1}and S

_{2}corresponding to values of the flexural strain of ε

_{f1}and ε

_{f1}can be calculated using the equation:

_{i}(mm) is the deflection and ε

_{fi}is the corresponding flexural strain.

## 3. Results and Discussion

#### 3.1. Characterization of Nanocomposite Structure

_{001}and indicate the exfoliation of nanofiller in the polymer matrix [2,7,24]. However, since the absence of diffraction maximum could also indicate the agglomeration of nanofiller, the microstructure of the specimens was additionally evaluated using SEM microscopy.

#### 3.2. Flexural Properties of PA12/Clay Nanocomposites

#### 3.2.1. Flexural Strength

^{2}are less than 0.05, meaning that they are statistically significant (have considerable effects on the response). Variables B, C, AB. AC, BC, B

^{2}, and C

^{2}with p-values greater than 0.05 are not significant and could be excluded from the model. The lack of fit for the model is not significant (p-value = 0.65 is greater than 0.05) and implies that the proposed model fits the experimental data. The coefficient of determination is 0.83.

^{2}are statistically significant (p-values are less than 0.05). The lack of fit for the model is not significant (p-value of 0.62 is greater than 0.05) and implies that the proposed model fits the experimental data. The coefficient of determination is 0.67. Based on the obtained results, an expression showing functional correlation between the flexural strength of PA12/clay nanocomposite and the content of nanoclay was established:

^{2}

#### 3.2.2. Flexural Modulus

**<**0.0001) indicates that at least one of the three regression variables have a regression coefficient unequal to zero—i.e., they have a correlation with the dependent variable. The p-value for variable A is less than 0.05 and is statistically significant (has a considerable effect on the response). Variables B and C have p-values greater than 0.05, meaning that they are not significant and could be excluded from the model. The lack of fit for the model is not significant (p-value of 0.76 is greater than 0.05) and implies that the proposed model fits the experimental data. The coefficient of determination is 0.76.

## 4. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Position of test specimen at the start of the test [37].

**Figure 3.**SEM micrographs of (

**a**) specimens made according to experiment No. 1, (

**b**) specimens made according to experiment No. 5, (

**c**) specimens made according to experiment No. 8, and (

**d**) specimens made according to experiment No. 9.

Experiment No./Point of the Experiment | A: Nanoclay Content, % | B: Screw Rotation Frequency, min^{−1} | C: Mixing Temperature, °C |
---|---|---|---|

1/factorial point | 3 | 20 | 210 |

2/factorial point | 9 | 20 | 210 |

3/factorial point | 3 | 40 | 210 |

4/factorial point | 9 | 40 | 210 |

5/factorial point | 3 | 20 | 230 |

6/factorial point | 9 | 20 | 230 |

7/factorial point | 3 | 40 | 230 |

8/factorial point | 9 | 40 | 230 |

9/axial point | 0.95 | 30 | 220 |

10/axial point | 11.05 | 30 | 220 |

11/axial point | 6 | 13.18 | 220 |

12/axial point | 6 | 46.82 | 220 |

13/axial point | 6 | 30 | 203.18 |

14/axial point | 6 | 30 | 236.82 |

15/center point | 6 | 30 | 220 |

16/center point | 6 | 30 | 220 |

17/center point | 6 | 30 | 220 |

18/center point | 6 | 30 | 220 |

19/center point | 6 | 30 | 220 |

Extruder type | Twin-screw, counter-rotating |

Screw diameter D | 42 mm |

Length/diameter ratio L/D | 6 |

Operating temperature max. | 350 °C |

Conveyor belt speed | 0.6 to 6 m/min |

Strand diameter | 1 to 4 mm |

Pellet length | 3 mm |

Strand pelletizer speed | 0.5 to 15 m/min |

Experiment No. | A: Nanoclay Content, % | B: Screw Rotation Frequency, min^{−1} | C: Mixing Temperature, °C | Flexural Strength σ_{fM}, MPa | Flexural Modulus E_{f}, GPa |
---|---|---|---|---|---|

1 | 3 | 20 | 210 | 65.6 | 1.7 |

2 | 9 | 20 | 210 | 67.9 | 2.0 |

3 | 3 | 40 | 210 | 64.4 | 1.6 |

4 | 9 | 40 | 210 | 68.5 | 2.0 |

5 | 3 | 20 | 230 | 66.2 | 1.7 |

6 | 9 | 20 | 230 | 68.7 | 2.2 |

7 | 3 | 40 | 230 | 63.8 | 1.5 |

8 | 9 | 40 | 230 | 72.2 | 2.2 |

9 | 0.95 | 30 | 220 | 62.5 | 1.4 |

10 | 11.05 | 30 | 220 | 67.6 | 2.1 |

11 | 6 | 13.18 | 220 | 71.9 | 1.9 |

12 | 6 | 46.82 | 220 | 70.1 | 2.0 |

13 | 6 | 30 | 203.18 | 68.6 | 1.9 |

14 | 6 | 30 | 236.82 | 69.8 | 1.9 |

15 | 6 | 30 | 220 | 69.4 | 1.6 |

16 | 6 | 30 | 220 | 67.3 | 1.9 |

17 | 6 | 30 | 220 | 70.1 | 2.0 |

18 | 6 | 30 | 220 | 69.2 | 1.9 |

19 | 6 | 30 | 220 | 66.1 | 1.7 |

PA12 | 60.7 | 1.4 |

Source | Sum of Squares | Degrees of Freedom df | Mean Square | F Value | p-Value |
---|---|---|---|---|---|

Model | 101.68 | 9 | 11.30 | 4.85 | 0.01 |

A—Nanoclay content | 48.82 | 1 | 48.82 | 20.94 | 0.001 |

B—Screw rotation frequency | 0.50 | 1 | 0.50 | 0.21 | 0.66 |

C—Mixing temperature | 3.11 | 1 | 3.11 | 1.34 | 0.28 |

AB | 7.18 | 1 | 7.18 | 3.08 | 0.11 |

AC | 2.62 | 1 | 2.62 | 1.12 | 0.32 |

BC | 0.34 | 1 | 0.34 | 0.15 | 0.71 |

A^{2} | 28.79 | 1 | 28.79 | 12.35 | 0.01 |

B^{2} | 5.57 | 1 | 5.57 | 2.39 | 0.16 |

C^{2} | 0.0009 | 1 | 0.0009 | 0.0004 | 0.99 |

Residual | 20.98 | 9 | 2.33 | ||

Lack of fit | 9.76 | 5 | 1.95 | 0.70 | 0.65 |

Pure error | 11.21 | 4 | 2.80 | ||

Cor total | 122.7 | 18 |

Source | Sum of Squares | Degrees of Freedom df | Mean Square | F Value | p-Value |
---|---|---|---|---|---|

Model | 82.24 | 2 | 41.12 | 16.28 | 0.0001 |

A—Nanoclay content | 48.82 | 1 | 48.82 | 19.33 | 0.001 |

A^{2} | 33.42 | 1 | 33.42 | 13.23 | 0.002 |

Residual | 40.42 | 16 | 2.53 | ||

Lack of fit | 29.20 | 12 | 2.43 | 0.87 | 0.62 |

Pure error | 11.21 | 4 | 2.80 | ||

Cor total | 122.66 | 18 |

Source | Sum of Squares | Degrees of Freedom df | Mean Square | F Value | p-Value |
---|---|---|---|---|---|

Model | 0.69 | 3 | 0.23 | 15.66 | <0.0001 |

A—Nanoclay content | 0.69 | 1 | 0.69 | 46.47 | <0.0001 |

B—Screw rotation frequency | 0.002 | 1 | 0.002 | 0.11 | 0.74 |

C—Mixing temperature | 0.006 | 1 | 0.01 | 0.41 | 0.53 |

Residual | 0.22 | 15 | 0.02 | ||

Lack of fit | 0.14 | 11 | 0.01 | 0.63 | 0.76 |

Pure error | 0.08 | 4 | 0.02 | ||

Cor total | 0.92 | 18 |

Source | Sum of Squares | Degrees of Freedom df | Mean Square | F Value | p-Value |
---|---|---|---|---|---|

Model | 0.69 | 1 | 0.69 | 50.90 | <0.0001 |

A—Nanoclay content | 0.69 | 1 | 0.69 | 50.90 | <0.0001 |

Residual | 0.23 | 17 | 0.01 | ||

Lack of fit | 0.15 | 13 | 0.01 | 0.56 | 0.81 |

Pure error | 0.08 | 4 | 0.02 | ||

Cor total | 0.92 | 18 |

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## Share and Cite

**MDPI and ACS Style**

Stojšić, J.; Raos, P.; Milinović, A.; Damjanović, D.
A Study of the Flexural Properties of PA12/Clay Nanocomposites. *Polymers* **2022**, *14*, 434.
https://doi.org/10.3390/polym14030434

**AMA Style**

Stojšić J, Raos P, Milinović A, Damjanović D.
A Study of the Flexural Properties of PA12/Clay Nanocomposites. *Polymers*. 2022; 14(3):434.
https://doi.org/10.3390/polym14030434

**Chicago/Turabian Style**

Stojšić, Josip, Pero Raos, Andrijana Milinović, and Darko Damjanović.
2022. "A Study of the Flexural Properties of PA12/Clay Nanocomposites" *Polymers* 14, no. 3: 434.
https://doi.org/10.3390/polym14030434