# Lightweight High-Performance Polymer Composite for Automotive Applications

^{1}

^{2}

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## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Experimental Protocol

#### 2.2. Rheology

_{0}is the zero shear viscosity, $\dot{\gamma}$ is the shear rate, ${\tau}^{*}$ is the critical stress level at the transition to shear thinning, and $n$ is the power law index. The zero shear viscosity was assumed to be given by the WLF equation:

#### 2.3. Injection Molding

#### 2.4. Density Measurements

#### 2.5. Mechanical Properties

#### 2.6. Thermal Properties

#### 2.7. Scanning Electron Microscope (SEM)

^{2}. At least two samples for each condition were analyzed. The interconnected cells were counted individually if a boundary was evident: when a cell was clearly formed by two or more different cells, each cell was counted; when instead, it was not possible to detect the single cells constituting a larger, non-spherical one, only one cell was counted.

#### 2.8. Analysis of Variance (ANOVA)

_{a}is the sum of squares of factor a and SS

_{T}is the total sum of squares [29]. For the significance level of the analysis, the probability value, p-value, was considered. In particular, a p-value of 0.05 was chosen (as normally done for experimental analysis). This indicates that, if the p-value is less than or equal to 0.05, a relationship exists between the dependent and the independent variable. Otherwise (i.e., if the p-value is greater than 0.05), there are no statistically significant differences between group means, as determined by ANOVA.

## 3. Results

#### 3.1. Microstructure

#### 3.2. Thermal Properties

#### 3.3. Mechanical Properties

#### 3.4. Analysis of Variance (ANOVA)

## 4. Conclusions

## Author Contributions

## Acknowledgments

## Conflicts of Interest

## References

- Turng, L.-S. Special and Emerging Injection Molding Processes. J. Inject. Molding Technol.
**2001**, 5, 160. [Google Scholar] - Pierick, D.; Jacobsen, K. Injection molding innovation: The microcellular foam process. Plast. Eng.
**2001**, 57, 46. [Google Scholar] - Hwang, S.S.; Hsu, P.P.; Chiang, C.W. Shrinkage study of textile roller molded by conventional/microcellular injection-molding process. Int. Commun. Heat Mass
**2008**, 35, 735–743. [Google Scholar] [CrossRef] - Kramschuster, A.; Cavitt, R.; Ermer, D.; Chen, Z.B.; Turng, L.S. Quantitative study of shrinkage and warpage behavior for microcellular and conventional injection molding. Polym. Eng. Sci.
**2005**, 45, 1408–1418. [Google Scholar] [CrossRef] - Lee, J.W.S.; Wang, J.; Yoon, J.D.; Park, C.B. Strategies to Achieve a Uniform Cell Structure with a High Void Fraction in Advanced Structural Foam Molding. Ind. Eng. Chem. Res.
**2008**, 47, 9457–9464. [Google Scholar] [CrossRef] - Pantani, R.; Volpe, V.; Titomanlio, G. Foam injection molding of poly(lactic acid) with environmentally friendly physical blowing agents. J. Mater. Process. Technol.
**2014**, 214, 3098–3107. [Google Scholar] [CrossRef] - Volpe, V.; Pantani, R. Foam injection molding of poly(lactic) acid: Effect of back pressure on morphology and mechanical properties. J. Appl. Polym. Sci.
**2015**, 132. [Google Scholar] [CrossRef] - Jacobsen, K.; Pierick, D. Microcellular foam molding: Advantages and application examples. In Proceedings of the Antec 2000: Society of Plastics Engineers Technical Papers, Orlando, FL, USA, 7–11 May 2000; pp. 1929–1933. [Google Scholar]
- Rizvi, S.J.A.; Bhatnagar, N. Optimization of Microcellular Injection Molding Parameters. Int. Polym. Proc.
**2009**, 24, 399–405. [Google Scholar] [CrossRef] - Guo, W.; Mao, H.J.; Li, B.; Guo, X.Y. Influence of processing parameters on molding process in microcellular injection molding. Procedia Eng.
**2014**, 81, 670–675. [Google Scholar] [CrossRef] - Volpe, V.; Pantani, R. Effect of processing condition on properties of polylactic acid parts obtained by foam injection molding. J. Cell. Plast.
**2017**, 53, 491–502. [Google Scholar] [CrossRef] - Chien, R.D.; Chen, S.C.; Lee, P.H.; Huang, J.S. Study on the molding characteristics and mechanical properties of injection-molded foaming polypropylene parts. J. Reinf. Plast. Comp.
**2004**, 23, 429–444. [Google Scholar] [CrossRef] - Li, J.; Chen, Z.; Wang, X.; Liu, T.; Zhou, Y.; Luo, S. Cell morphology and mechanical properties of microcellular mucell
^{®}injection molded polyetherimide and polyetherimide/fillers composite foams. J. Appl. Polym. Sci.**2013**, 130, 4171–4181. [Google Scholar] [CrossRef] - Gómez-Monterde, J.; Sánchez-Soto, M.; Maspoch, M.L. Microcellular PP/GF composites: Morphological, mechanical and fracture characterization. Compos. Part A Appl. Sci. Manuf.
**2018**, 104, 1–13. [Google Scholar] [CrossRef] - Zhang, G.; Thompson, M.R. Reduced fibre breakage in a glass-fibre reinforced thermoplastic through foaming. Compos. Sci. Technol.
**2005**, 65, 2240–2249. [Google Scholar] [CrossRef] - Xi, Z.H.; Sha, X.Y.; Liu, T.; Zhao, L. Microcellular injection molding of polypropylene and glass fiber composites with supercritical nitrogen. J. Cell. Plast.
**2014**, 50, 489–505. [Google Scholar] [CrossRef] - Gómez-Monterde, J.; Schulte, M.; Ilijevic, S.; Hain, J.; Arencón, D.; Sánchez-Soto, M.; Maspoch, M.L. Morphology and Mechanical Characterization of ABS Foamed by Microcellular Injection Molding. Procedia Eng.
**2015**, 132, 15–22. [Google Scholar] [CrossRef] [Green Version] - Liu, T.; Chen, Z.L.; Lei, Y.J.; Wang, X.Z.; Luo, S.K. Foaming behaviors of polyetherimide/polypropylene-graft-maleic anhydride blends in the microcellular injection molding process. J. Cell. Plast.
**2015**, 51, 387–400. [Google Scholar] [CrossRef] - Roch, A.; Kehret, L.; Huber, T.; Henning, F.; Elsner, P. Investigations On Injection Molded, Glass-Fiber Reinforced Polyamide 6 Integral Foams Using Breathing Mold Technology. In Proceedings of the PPS-30: The 30th International Conference of the Polymer Processing Society, Cleveland, OH, USA, 6–12 June 2015; Volume 1664. [Google Scholar] [CrossRef]
- Yousefian, H.; Rodrigue, D. Morphological, physical and mechanical properties of nanocrystalline cellulose filled Nylon 6 foams. J. Cell. Plast.
**2017**, 53, 253–271. [Google Scholar] [CrossRef] - Gong, S.; Yuan, M.; Chandra, A.; Kharbas, H.; Osorio, A.; Turng, L.S. Microcellular injection molding. Int. Polym. Proc.
**2005**, 20, 202–214. [Google Scholar] [CrossRef] - Yuan, M.J.; Turng, L.S. Microstructure and mechanical properties of microcellular injection molded polyamide-6 nanocomposites. Polymer
**2005**, 46, 7273–7292. [Google Scholar] [CrossRef] - Yuan, M.J.; Turng, L.S. Studies of microcellular nanocomposites with supercritical fluid assisted injection moulding process. Plast. Rubber Compos.
**2006**, 35, 129–138. [Google Scholar] [CrossRef] - Liu, T.; Liu, H.W.; Li, L.L.; Wang, X.Z.; Lu, A.; Luo, S.K. Microstructure and Properties of Microcellular Poly (phenylene sulfide) Foams by Mucell Injection Molding. Polym. Plast. Technol.
**2013**, 52, 440–445. [Google Scholar] [CrossRef] - Ma, Z.L.; Zhang, G.C.; Yang, Q.; Shi, X.T.; Li, J.T.; Fan, X.L. Microcellular Foams of Glass-Fiber Reinforced Poly(phenylene sulfide) Composites Generated Using Supercritical Carbon Dioxide. Polym. Compos.
**2016**, 37, 2527–2540. [Google Scholar] [CrossRef] - Pantani, R.; Coccorullo, I.; Speranza, V.; Titomanlio, G. Modeling of morphology evolution in the injection molding process of thermoplastic polymers. Prog. Polym. Sci.
**2005**, 30, 1185–1222. [Google Scholar] [CrossRef] - Volpe, V.; De Filitto, M.; Klofacova, V.; De Santis, F.; Pantani, R. Effect of mold opening on the properties of PLA samples obtained by foam injection molding. Polym. Eng. Sci.
**2018**, 58, 475–484. [Google Scholar] [CrossRef] - Gonzalez, H., Jr. Efficiency of Foams in Stiffness Applications. J. Cell. Plast.
**1976**, 12, 49–58. [Google Scholar] [CrossRef] - Shuib, R.K.; Pickering, K.L.; Mace, B.R. Dynamic properties of magnetorheological elastomers based on iron sand and natural rubber. J. Appl. Polym. Sci.
**2015**, 132. [Google Scholar] [CrossRef] - Zhang, L.; Zhao, G.Q.; Wang, G.L. Formation mechanism of porous structure in plastic parts injected by microcellular injection molding technology with variable mold temperature. Appl. Eng.
**2017**, 114, 484–497. [Google Scholar] [CrossRef] - De Santis, F.; Pantani, R.; Speranza, V.; Titomanlio, G. Analysis of Shrinkage Development of a Semicrystalline Polymer during Injection Molding. Ind. Eng. Chem. Res.
**2010**, 49, 2469–2476. [Google Scholar] [CrossRef] - Crema, L.; Sorgato, M.; Zanini, F.; Carmignato, S.; Lucchetta, G. Experimental analysis of mechanical properties and microstructure of long glass fiber reinforced polypropylene processed by rapid heat cycle injection molding. Compos. Part A Appl. Sci. Manuf.
**2018**, 107, 366–373. [Google Scholar] [CrossRef] - Shaayegan, V.; Ameli, A.; Wang, S.; Park, C.B. Experimental observation and modeling of fiber rotation and translation during foam injection molding of polymer composites. Compos. Part A Appl. Sci. Manuf.
**2016**, 88, 67–74. [Google Scholar] [CrossRef]

**Figure 4.**Half-section of samples molded with injection temperature of 280 °C (

**a**) and 300 °C (

**b**). Sample thickness 3 mm.

**Figure 7.**Scanning electron microscopy (SEM) images of skin, transition zone, and core layer of the samples with gas injection pressure 70 bar (GAS 1) at the three analyzed thicknesses.

**Figure 8.**Scanning electron microscopy (SEM) images of skin, transition zone, and core layer of samples that were obtained with gas injection pressure 120 bar (GAS 2) at the three analyzed thicknesses.

**Figure 10.**Cell size distribution in the transition zone (

**a**) and core (

**b**) of samples foamed at 120 bar.

**Figure 11.**Heat Deflection Temperature for unfoamed samples, and GAS 1 and GAS 2 samples at all of the three part thicknesses.

**Figure 13.**Ratio between flexural modulus of the structural foam and flexural modulus of the matrix: comparison of experimental values and values predicted by Equation (5).

**Figure 14.**Factor coding of part density (values at 300 °C), flexural modulus (values at 300 °C), and cell density in the core (values at 4 mm). Bars represent the predicted values, points represent the values below (white) and above (red) the predicted values.

Parameter | CASE 1 |
---|---|

n | 0.2 |

τ* | 5500 Pa |

D1 | 3.00 × 10^{30} Pa·s |

T* | 323.17 K |

A1 | 76.1 |

A2 | 51.6 K |

Process Parameter | CASE 1 | CASE 2 |
---|---|---|

Injection temperature (°C) | 300 | 280 |

Mold temperature (°C) | 90 | 90 |

Injection Flow Rate (cm^{3}/s) | 26 | 26 |

Screw rotation during dosage (rpm) | 200 | 200 |

Back pressure (bar) | 0 | 0 |

Max filling pressure (bar) | 70 | 70 |

Gas injection pressure (bar) | 70–120 | 70–120 |

Cavity thickness (mm) | 2–3–4 | 2–3–4 |

Condition | Gas Injection Pressure (bar) | Gas Amount/Injection Volume (g/ccm) | ||
---|---|---|---|---|

2 mm | 3 mm | 4 mm | ||

GAS 1 | 70 | 0.020 | 0.013 | 0.013 |

GAS 2 | 120 | 0.038 | 0.036 | 0.031 |

Condition | Skin Thickness (μm) | ||
---|---|---|---|

2 mm | 3 mm | 4 mm | |

GAS 1 | 200 | 280 | 180 |

GAS 2 | 280 | 190 | 170 |

Source | Sum of Squares | df | Mean Square | F-value | p-value | Dependence | Percentage Contribution |
---|---|---|---|---|---|---|---|

Model | 0.3559 | 5 | 0.0712 | 19.79 | <0.0001 | significant | - |

Part thickness (A) | 0.2355 | 2 | 0.1177 | 32.74 | <0.0001 | - | 56.46% |

Gas injection pressure (B) | 0.1023 | 1 | 0.1023 | 28.46 | <0.0001 | - | 24.53% |

AB | 0.0181 | 2 | 0.0091 | 2.52 | 0.1100 | - | 4.34% |

Residual | 0.0611 | 17 | 0.0036 | - | - | - | 14.65% |

Cor Total | 0.4171 | 23 | - | - | - | - |

Source | Sum of Squares | df | Mean Square | F-value | p-value | Dependence | Percentage Contribution |
---|---|---|---|---|---|---|---|

Model | 0.6636 | 2 | 0.3318 | 8.78 | 0.0077 | significant | - |

Part thickness | 0.6636 | 2 | 0.3318 | 8.78 | 0.0077 | - | 66.36% |

Residual | 0.3400 | 9 | 0.0378 | - | - | - | 34.00% |

Cor Total | 1.00 | 11 | - | - | - | - | - |

Source | Sum of Squares | df | Mean Square | F-value | p-value | Dependence | Percentage Contribution |
---|---|---|---|---|---|---|---|

Model | 5.805 × 10^{−10} | 3 | 1.935 × 10^{−10} | 16.86 | 0.0008 | significant | - |

Gas Injection pressure (A) | 3.003 × 10^{−10} | 1 | 3.003 × 10^{−10} | 26.17 | 0.0009 | - | 44.67% |

Injection temperature (B) | 1.633 × 10^{−10} | 1 | 1.633 × 10^{−10} | 14.23 | 0.0054 | - | 24.29% |

AB | 1.168 × 10^{−10} | 1 | 1.168 × 10^{−10} | 10.18 | 0.0128 | - | 17.37% |

Residual | 9.180 × 10^{−10} | 8 | 1.148 × 10^{−11} | - | - | - | 13.65% |

Cor Total | 6.723 × 10^{−10} | 11 | - | - | - | - | v |

Parameter | Intercept | Factor A: Injection Temperature | Factor B(1): Part Thickness | Factor B(2): Part Thickness | Factor C: Gas Injection Pressures | Factor AC | Factor B(1)C | Factor B(2)C |
---|---|---|---|---|---|---|---|---|

Part density | 1.115293 | - | 0.1381 | −0.048607 | −0.0653 | - | 0.0038 | 0.0316 |

p-value | - | - | <0.0001 | <0.0001 | <0.0001 | - | 0.1100 | 0.1100 |

Normalized modulus | 1.12 | - | −0.2975 | 0.02 | - | - | - | - |

p-value | - | - | 0.0077 | 0.0077 | - | - | - | - |

Cell density | 7.09 × 10^{−6} | 3.69 × 10^{−6} | - | - | 5.00 × 10^{−6} | 3.12 × 10^{−6} | - | - |

p-value | - | 0.0054 | - | - | 0.0009 | 0.0128 | - | - |

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**MDPI and ACS Style**

Volpe, V.; Lanzillo, S.; Affinita, G.; Villacci, B.; Macchiarolo, I.; Pantani, R.
Lightweight High-Performance Polymer Composite for Automotive Applications. *Polymers* **2019**, *11*, 326.
https://doi.org/10.3390/polym11020326

**AMA Style**

Volpe V, Lanzillo S, Affinita G, Villacci B, Macchiarolo I, Pantani R.
Lightweight High-Performance Polymer Composite for Automotive Applications. *Polymers*. 2019; 11(2):326.
https://doi.org/10.3390/polym11020326

**Chicago/Turabian Style**

Volpe, Valentina, Sofia Lanzillo, Giovanni Affinita, Beniamino Villacci, Innocenzo Macchiarolo, and Roberto Pantani.
2019. "Lightweight High-Performance Polymer Composite for Automotive Applications" *Polymers* 11, no. 2: 326.
https://doi.org/10.3390/polym11020326