6.1. Mechanical Properties of Polymer Hybrid Composites with Added Ionic Liquids
The significance of mechanical properties in polymer hybrid composites and hybrid polymer composites becomes apparent when developing advanced materials. These properties play central roles in determining the overall performance, durability, and suitability of these materials for specific applications. They serve as valuable indicators of how these composites will respond to various loads and conditions, thereby assisting in their optimal utilization. Among these mechanical attributes, tensile properties occupy a pivotal position in evaluating the structural integrity of these composites. The tensile strength, tensile modulus, and elongation at break collectively offer valuable insights into a composite’s capacity to withstand pulling forces to measure its levels of strength and stiffness as well as its degree of ductility.
Table 9 shows the tensile properties of polymer hybrid composites with added ionic liquids. Chen et al. fabricated Chito/rGO/SPT composites with added EmimOAc using the thermomechanical kneading method [
1]. The tensile strength of the Chito/rGO/SPT-EmimOAc (20 wt.%) composite was 26.40 MPa, which is substantially lower than that of the Chito/rGO/SPT composite (60.70 MPa). Moreover, the Young’s modulus of the Chito/rGO/SPT-EmimOAc composite was 893 MPa, while that of the Chito/rGO/SPT composite was 1635 MPa. However, the elongation at break of the Chito/rGO/SPT-EmimOAc composite was 78%, which is significantly higher compared to that of the Chito/rGO/SPT composite (19%). The results displayed that the addition of EmimOAc reduced the mechanical strength and stiffness of the Chito/rGO/SPT composite. Nevertheless, this reduction in mechanical properties was accompanied by a substantial improvement in the composite’s ductility, which indicated a higher level of chitosan plasticization facilitated by EmimOAc in the presence of rGO and SPT. The results can help in the design of biopolymer hybrid composites with customized mechanical properties for biomedical, biotechnology, and other high-value applications.
Wan et al. fabricated EP/MPP/GO composites with added BmimPF
6 using the magnetic stirring method [
17]. The tensile strength of the EP/MPP/GO-BmimPF
6 (0.1 wt.%) composite was 50.64 MPa, which is moderately higher than that of the EP/MPP/GO composite (45.64 MPa). However, the tensile modulus of the EP/MPP/GO-BmimPF
6 composite was 1085 MPa, whereas that of the EP/MPP/GO composite was 1339 MPa. The results showed that the addition of BmimPF
6 improved the composite’s resistance to stretching or deformation. This improvement can be attributed to the reinforcing effect of GO-BmimPF
6 on the composite’s structural integrity. Nonetheless, this improvement was convoyed by a decrease in stiffness, which might affect the ductility of the composite.
Li et al. fabricated EP/Mo-MOF/GO composites with added BmimBF
4 using the magnetic stirring method [
2]. The tensile strength of the EP/Mo-MOF/GO-BmimBF
4 (3.0 wt.%) composite was 64.31 MPa, which is significantly higher than that of the EP/Mo-MOF/GO composite (51.23 MPa). Moreover, the elongation at break of the EP/Mo-MOF/GO-BmimBF
4 composite was 14%, which is marginally higher compared to that of the EP/Mo-MOF/GO composite (11%). The results exhibited that the addition of BmimBF
4 contributed positively to enhancing the mechanical properties of the composite. Furthermore, the presence of BmimBF
4 resulted in an improved dispersion of the Mo-MOF/GO within the composite and lessened the distinct interface, and Mo-MOF/GO became completely incorporated into the EP matrix. The results also indicated that excellent mechanical properties were obtained, which can broaden the thermoset hybrid composites’ scenario application.
Yasin et al. fabricated NR/CS/CNC composites with added AmimCl using the two-roll milling method [
28]. The tensile strength of the NR/CS/CNC-AmimCl (2.0 phr) composite was 4.65 MPa, which is moderately higher than that of the NR/CS/CNC composite (4.10 MPa). However, the elongation at break of the NR/CS/CNC-AmimCl composite was 205%, which is modestly lower compared to that of the NR/CS/CNC composite (220%). The results demonstrated that the addition of AmimCl had a discernible effect on the strength, which could be due to the improved NR-CS/CNC interfacial interaction. On the other hand, a modest reduction in the elongation of the composite suggested a trade-off between strength and ductility. The results provide a perspective for manufacturing high-performance rubber hybrid composites using novel fillers and an ionic liquid.
Wang et al. fabricated NR/CSDPF composites with added AmimCl using the two-roll milling method [
29]. The tensile strength of the NR/CSDPF-AmimCl (0.8 phr) composite was 29.60 MPa, which is moderately higher than that of the NR/CSDPF composite (24.70 MPa). However, the tensile modulus of the NR/CSDPF-AmimCl composite was 10 MPa, while that of the NR/CSDPF composite was 12 MPa. Moreover, the elongation at break of the NR/CSDPF-AmimCl composite was 660%, which is significantly higher compared to that of the NR/CSDPF composite (517%). The results indicated that the addition of AmimCl led to interactions with CSPDF and NR (
Figure 5), which enhanced CSPDF dispersion within the NR matrix and facilitated effective stress dissipation. Additionally, during tensile fatigue, the hydrogen bonding between AmimCl and CSDPF was subject to disruption and reformation as the NR chains slid along the CSDPF filler.
Zhang et al. fabricated PA6/MPP/MMT composites with added TDPBr using the melt extrusion method [
13]. The tensile strength of the PA6/MPP/MMT-TDPBr (5.0 phr) composite was 50.00 MPa, which is marginally lower than that of the PA6/MPP/MMT composite (53.00 MPa). However, the tensile modulus of the PA6/MPP/MMT-TDPBr composite was 2116 MPa, whereas that of the PA6/MPP/MMT composite was 2077 MPa. Moreover, the strain at break of the PA6/MPP/MMT-TDPBr composite was 2%, which is slightly lower compared to that of the PA6/MPP/MMT composite (3%). The results revealed that the addition of TDPBr modified MMT, which increased the interaction between the MMT-TDPBr and PA6 matrix and consequently improved the dispersion of MMT-TDPBr particles in the matrix. Additionally, the larger increase in the modulus was due to the coordinative effect of MPP between the MMT-TDPBr and PA6 matrix.
Sa et al. fabricated PMMA/rGO/MWCNTs composites with added BmimTFSI using the magnetic stirring method [
21]. The tensile strength of the PMMA/rGO/MWCNTs-BmimTFSI (0.5 wt.%) composite was 46.52 MPa, which is significantly higher than that of the PMMA/rGO composite (21.45 MPa). Moreover, the Young’s modulus of the PMMA/rGO/MWCNTs-BmimTFSI composite was 2250 MPa, while that of the PMMA/rGO composite was 1560 MPa. The results exposed that the addition of BmimTFSI had a remarkable impact on the mechanical properties of the composite, which made it considerably stronger, stiffer, and more structurally stable. This can be attributed to the robust cation-π or π–π interactions that occurred between MWCNTs-BmimTFSI and the PMMA matrix.
Sahu et al. fabricated PVA/AgNPs/GO composites with added AmimCl using the magnetic stirring method [
25]. The tensile strength of the PVA/AgNPs/GO-AmimCl composite was 34.49 MPa, which is moderately higher than that of the PVA/AgNPs/GO composite (32.36 MPa). However, the elongation at break of the PVA/AgNPs/GO-AmimCl composite was 133%, which is modestly lower compared to that of the PVA/AgNPs/GO composite (149%). The results illustrated that the addition of AmimCl served as a connector between GO and PVA, which lessened the available space and thereby limited the mobility of the PVA chains and facilitated the stress transfer. The interaction between GO-AmimCl and PVA constrained the slipping motion, which reduced the ductility. The results show that the creation of polymer hybrid composites with tailored mechanical properties can be facilitated, which may have potential for biomedical applications.
6.2. Mechanical Properties of Hybrid Polymer Composites with Added Ionic Liquids
Table 10 shows the tensile properties of hybrid polymer composites with added ionic liquids. Gouvêa and Andrade fabricated PHBV/EVA/rGO-ZnO composites with added BmimPF
6 using the melt extrusion method [
3]. The tensile strength of the PHBV/EVA/rGO-ZnO-BmimPF
6 (7.0 wt.%) composite was 4.5 MPa, which is significantly lower than that of the PHBV/EVA/rGO-ZnO composite (7.6 MPa). Moreover, the Young’s modulus of the PHBV/EVA/rGO-ZnO-BmimPF
6 composite was 348 MPa, while that of the PHBV/EVA/rGO-ZnO composite was 401 MPa. The results exhibited that the addition of BmimPF
6 had a weakening effect on the mechanical properties of the composite. This is due to the higher mobility of PHBV chains, which improved elongation. Therefore, the presence of BmimPF
6 resulted in a compromise between the strength and stiffness of the composite. The results also showed that the reduced mechanical properties of the hybrid polymer composites can be widely used in packaging applications.
Wang et al. fabricated PLA/EMA-GMA/MWCNTs composites with added CmmimBF
4 using the melt blending method [
30]. The tensile strength of the PLA/EMA-GMA/MWCNTs-CmmimBF
4 (2.0 wt.%) composite was 29.0 MPa, which is similar to that of the PLA/EMA-GMA/MWCNTs composite (29.0 MPa). Moreover, the elongation at break of the PLA/EMA-GMA/MWCNTs-CmmimBF
4 composite was 138%, which is significantly higher compared to that of the PLA/EMA-GMA/MWCNTs composite (25%). The results indicated that the addition of CmmimBF
4 played a crucial role in enhancing the ability of the composite to deform and stretch, which resulted in increased composite ductility. Furthermore, the even dispersion of MWCNTs mitigated the buildup of stress when the composite underwent tensile testing. Hybrid polymer composites with high flexibility and great reliability can be potentially applied in power electronics, power conditioning, and pulsed power applications.
Lopes Pereira et al. fabricated PLA/EVA/MWCNTs composites with added MimbSO
3H·Cl using the melt blending method [
12]. The tensile strength of the PLA/EVA/MWCNTs-MimbSO
3H·Cl (2.5 phr) composite was 24.0 MPa, which is modestly higher than that of the PLA/EVA/MWCNTs composite (21.0 MPa). Moreover, the tensile modulus of the PLA/EVA/MWCNTs-MimbSO
3H·Cl composite was 660 MPa, whereas that of the PLA/EVA/MWCNTs composite was 650 MPa. Additionally, the elongation at break of the PLA/EVA/MWCNTs-MimbSO
3H·Cl composite was 8%, which is moderately higher compared to that of the PLA/EVA/MWCNTs composite (6%). The results showed that the addition of MimbSO
3H·Cl had a discernible impact on the mechanical properties of the composite. This suggests that MimbSO
3H·Cl might have contributed to a slightly stiffer composite and enhanced ductility. This change can likely be attributed to improved interfacial adhesion, which is facilitated by the compatibilization process. The results suggested that hybrid polymer composites are a promising option for developing semi-biodegradable conducting materials, particularly for antistatic packaging and diverse applications in the electroelectronic industry.
Huang et al. fabricated PLA/PCL/PU/MWCNTs composites with added BmimmpdBr using the melt blending method [
31]. The tensile strength of the PLA/PCL/PU/MWCNTs-BmimmpdBr (0.8 wt.%) composite was 36.1 MPa, which is moderately higher than that of the PLA/PCL/MWCNTs composite (32.3 MPa). Moreover, the elongation at break of the PLA/PCL/PU/MWCNTs-BmimmpdBr composite was 308%, which is significantly higher compared to the PLA/PCL/MWCNTs composite (242%). The results displayed that the addition of BmimmpdBr improved the interfacial adhesion between the immiscible PLA and PCL phases, which aided in stress transfer and increased stress dissipation during the tensile testing. Additionally, the enhanced ductility was due to the compatibilizing effect of BmimmpdBr-functionalized MWCNTs.
Yousfi et al. fabricated PP/PA6/n-Talc composites with added TTPTMP using the melt extrusion method [
35]. The tensile strength of the PP/PA6/n-Talc-TTPTMP (2.0 wt.%) composite was 38.5 MPa, which is significantly higher than that of the PP/PA6 blend (28.8 MPa). Moreover, the Young’s modulus of the PP/PA6/n-Talc-TTPTMP composite was 2060 MPa, while that of the PP/PA6 blend was 1880 MPa. Furthermore, the elongation at break of the PP/PA6/n-Talc-TTPTMP composite was 18%, which is slightly higher compared to that of the PP/PA6 blend (17%). The results demonstrated that the addition of TTPTMP led to a substantial boost in stiffness without compromising the ductility of the composite. Additionally, it is believed that the improved mechanical properties primarily stemmed from the strong interactions and excellent dispersion, as well as the exfoliation of n-Talc layers within the minor PA6 phase.
Liu et al. fabricated SR/POE/MWCNTs composites with added VeimBr using the two-roll milling method [
38]. The tensile strength of the SR/POE/MWCNTs-VeimBr (7.0 wt.%) composite was 6.4 MPa, which is substantially higher than that of the SR/POE blend (4.5 MPa). However, the elongation at break of the SR/POE/MWCNTs-VeimBr composite was 183%, which is significantly lower compared to that of the SR/POE blend (370%). The results illustrated that the addition of VeimBr participated in the cross-linking of SR, which enhanced the strength of the composite. Nevertheless, while the reinforcement provided by MWCNTs-VeimBr improved the composite’s strength, it concurrently led to a notable reduction in the ductility of the composite. The results offer a clever and efficient approach for fabricating promising hybrid polymer composites suitable for microwave absorption applications.
Zhao et al. fabricated Stch/PBS/MgCl
2 composites with added BmimCl using the melt blending method [
7]. The tensile strength of the Stch/PBS/MgCl
2-BmimCl (8.8 wt.%) composite was 15.8 MPa, which is significantly higher than that of the Stch/PBS/BmimCl blend (10.8 MPa). Furthermore, the Young’s modulus of the Stch/PBS/MgCl
2-BmimCl composite was 1183 MPa, while that of the Stch/PBS/BmimCl blend was 687 MPa. Moreover, the elongation at break of the Stch/PBS/MgCl
2-BmimCl composite was 20%, which is moderately higher compared to that of the Stch/PBS/BmimCl blend (14%). The results revealed that the addition of BmimCl, particularly in the presence of MgCl
2, resulted in substantial improvements in strength and ductility. This is because chloride anions, which are abundant in electrons, can form robust interactions with hydrogen atoms within the Stch/PBS blend (
Figure 6), which bolstered the compatibility between the Stch and PBS phases.