An experimental study on mechanical properties of a novel hybrid metal–polymer joining technology based on a reaction between isocyanate and hydroxyl groups

2017 ◽  
Vol 30 ◽  
pp. 217-225 ◽  
Author(s):  
Omid Izadi ◽  
Peiman Mosaddegh ◽  
Mohammad Silani ◽  
Mohammad Dinari
Crystals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 62
Author(s):  
Xu Xu ◽  
Zeping Zhang ◽  
Wenjuan Yao

Graphene and graphene oxide (GO) usually have grain boundaries (GBs) in the process of synthesis and preparation. Here, we “attach” GBs into GO, a new molecular configuration i.e., polycrystalline graphene oxide (PGO) is proposed. This paper aims to provide an insight into the stability and mechanical properties of PGO by using the molecular dynamics method. For this purpose, the “bottom-up” multi-structure-spatial design performance of PGO and the physical mechanism associated with the spatial structure in mixed dimensions (combination of sp2 and sp3) were studied. Also, the effect of defect coupling (GBs and functional groups) on the mechanical properties was revealed. Our results demonstrate that the existence of the GBs reduces the mechanical properties of PGO and show an “induction” role during the tensile fracture process. The presence of functional groups converts in-plane sp2 carbon atoms into out-of-plane sp3 hybrid carbons, causing uneven stress distribution. Moreover, the mechanical characteristics of PGO are very sensitive to the oxygen content of functional groups, which decrease with the increase of oxygen content. The weakening degree of epoxy groups is slightly greater than that of hydroxyl groups. Finally, we find that the mechanical properties of PGO will fall to the lowest values due to the defect coupling amplification mechanism when the functional groups are distributed at GBs.


2021 ◽  
Vol 5 (4) ◽  
pp. 110
Author(s):  
Flaminio Sales ◽  
Andrews Souza ◽  
Ronaldo Ariati ◽  
Verônica Noronha ◽  
Elder Giovanetti ◽  
...  

Polydimethylsiloxane (PDMS) is a polymer that has attracted the attention of researchers due to its unique properties such as transparency, biocompatibility, high flexibility, and physical and chemical stability. In addition, PDMS modification and combination with other materials can expand its range of applications. For instance, the ability to perform superhydrophobic coating allows for the manufacture of lenses. However, many of these processes are complex and expensive. One of the most promising modifications, which consists of the development of an interchangeable coating, capable of changing its optical characteristics according to some stimuli, has been underexplored. Thus, we report an experimental study of the mechanical and optical properties and wettability of pure PDMS and of two PDMS composites with the addition of 1% paraffin or beeswax using a gravity casting process. The composites’ tensile strength and hardness were lower when compared with pure PDMS. However, the contact angle was increased, reaching the highest values when using the paraffin additive. Additionally, these composites have shown interesting results for the spectrophotometry tests, i.e., the material changed its optical characteristics when heated, going from opaque at room temperature to transparent, with transmittance around 75%, at 70 °C. As a result, these materials have great potential for use in smart devices, such as sensors, due to its ability to change its transparency at high temperatures.


2016 ◽  
Vol 29 (1) ◽  
pp. 26-35 ◽  
Author(s):  
Yunwu Yu ◽  
Wenhao Pan ◽  
Xiaoman Guo ◽  
Lili Gao ◽  
Yaxin Gu ◽  
...  

Poly(arylene ether sulfone) (PES)–titanium dioxide (TiO2) hybrid membranes were prepared via solution blending method using TiO2 nanoparticles as inorganic filler. The chemical structure and thermal stability of the matrix polymer were characterized by proton nuclear magnetic resonance, Fourier transform infrared, differential scanning calorimetry, and thermogravimetric analysis. The crystal structure, morphology, mechanical properties, and gas separation performance of hybrid membranes were characterized in detail. As shown in scanning electron microscopic images, TiO2 nanoparticles dispersed homogeneously in the matrix. Although the mechanical properties of hybrid membranes decreased certainly compared to the pure PES membranes, they are strong enough for gas separation in this study. All gas permeability coefficients of PES-TiO2 hybrid membranes were higher than pure PES membranes, attributed to the nanogap caused by TiO2 nanoparticles, for instance, oxygen and nitrogen permeability coefficients of Hybrid-3 (consists of PES with 4-amino-phenyl pendant group and hexafluoroisopropyl (Am-PES)-20 and TiO2 nanoparticles, 5 wt%) increased from 2.57 and 0.33 to 5.88 and 0.63, respectively. In addition, the separation factor increased at the same time attributed to the stimulative transfer effect caused by the interaction of hydroxyl groups on the TiO2 nanoparticle and polar carbon dioxide molecules.


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