Dielectric Spectrum of Random Copolymerization Polypropylene Nanocomposites Doped with Nano Silica at Different Temperatures

Author(s):  
Rujia Men ◽  
Zhipeng Lei ◽  
Jiancheng Song ◽  
Kunying Han ◽  
Lu Li ◽  
...  
1991 ◽  
Vol 46 (11) ◽  
pp. 1001-1008 ◽  
Author(s):  
M. Rohmann ◽  
M. Stockhausen

AbstractThe dielectric spectrum is measured up to 72 GHz of solutions of polyvinylpyrrolidone (PVP) in tetramethylurea (TMU), dimethylethylene urea and dimethylpropylene urea. Concentrations are up to a monomole fraction of 0.65 (PVP 1200) or 0.5 (PVP 40 000). Measuring temperatures are 20CC for all systems and additionally 40 and 60°C for the TMU solutions. For the description of the results a superposition of Debye type components is used, which are discussed in particular with respect to the solvent contributions. These can be distinguished into three regions: (i) Unaffected bulk-type; (ii) loosely affected, relaxation time and activation enthalpy increasing with increasing polymer content; (iii) quasi bound and moving together with the polymer. The solvation numbers (total of affected solvent per repeat unit of polymer) are about 1.5 to 2.


Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3708
Author(s):  
Penghu Li ◽  
Haiyun Jin ◽  
Shichao Wei ◽  
Huaidong Liu ◽  
Naikui Gao ◽  
...  

Ceramizable composite is a kind of polymer matrix composite that can turn into ceramic material at a high temperature. It can be used for the ceramic insulation of a metal conductor because of its processability. However, poor low-temperature ceramization performance is a problem of ceramizable composites. In this paper, ceramizable composites were prepared by using silicone rubber as a matrix. Ceramic samples were sintered at different temperatures no more than 1000 °C, according to thermogravimetric analysis results of the composites. The linear contraction and flexural strength of the ceramics were measured. The microstructure and crystalline phase of ceramics were analyzed using scanning electron microscope (SEM) and X-ray diffraction (XRD). The results show that the composites turned into ceramics at 800 °C, and a new crystal and continuous microstructure formed in the samples. The flexural strength of ceramics was 46.76 MPa, which was more than twice that of similar materials reported in other research sintered at 1000 °C. The maximum flexural strength was 54.56 MPa, when the sintering temperature was no more than 1000 °C. Moreover, glass frit and nano silica played important roles in the formation of the ceramic phase in this research. A proper content of nano silica could increase the strength of the ceramic samples.


2019 ◽  
Vol 9 (9) ◽  
pp. 1033-1042 ◽  
Author(s):  
Zheng-Huan Wu ◽  
Jun-Xin Guo ◽  
Qi-Xiang Fan ◽  
Quan Wang ◽  
Yu-Jun Cai ◽  
...  

In this work, the same formulations of Nano-Silica/intumescent fire retardant polypropylene nanocomposites were prepared via a novel vane extruder and a tri-screw extruder, which represented elongational flow field and shearing flow field, respectively. Not only the synergistic combustion mechanisms of Kissinger method and Flynn-Wall-Ozawa method were revealed, but also the combustion effect and efficiency were compared. Both two methods proved specimens that processed by TE exhibited higher thermal stability. The smaller aggregates of physical initial Nano-Silica, the better dispersivity of aggregates in specimens that processed by VE. Such property broke the compactness degree of char layer.


2012 ◽  
Vol 488-489 ◽  
pp. 588-591
Author(s):  
Jin Peng Feng ◽  
De Ping Chen ◽  
Wen Ni ◽  
Shao Jian Ma

This work investigated the thermal stability of nano-silica thermal insulating composites, which consisted of fumed silica, fibers and opacifiers. The volume shrinkage was introduced as an evaluation index to characterize thermal stability of the composites at different temperatures. The effects of serving temperature, serving time, particle size of fumed silica and mass ratio of SiC were discussed. The results indicated nano-silica thermal insulating composites have excellent thermal stability under the temperature of 800°C. The volume shrinkage was correlated positively with serving time. High specific surface area of fumed silica could bring good thermal insulating performance, but at the same time caused high volume shrinkage when applied at high temperatures. SiC as an opacifier has little influence on volume shrinkage, but too much amount may yet increase solid heat transfer and lead to the drop of thermal insulating properties.


2021 ◽  
pp. 103750
Author(s):  
Haibao Liu ◽  
Qiuyi Li ◽  
Songyuan Ni ◽  
Liang Wang ◽  
Gongbing Yue ◽  
...  

2016 ◽  
Vol 848 ◽  
pp. 174-178
Author(s):  
Qian Wang

In this paper, both the permittivity and the microwave transmittance properties of organosilicon-matrix composites under different temperatures have been studied. In order to investigate the reason for the changing of dielectric property, both TGA and high-temperature dielectric spectrum measurement have been carried out. A theoretical model of radome, with a temperature gradient distribution, has been built to analyze the dependence of microwave transmittance property on temperature. Based on the experimental results, we can optimize the effective operating temperature of this kind of organosilicone-matrix composites.


2011 ◽  
Vol 284-286 ◽  
pp. 102-105
Author(s):  
Jin Peng Feng ◽  
De Ping Chen ◽  
Wen Ni ◽  
Shao Jian Ma ◽  
Jin Lin Yang ◽  
...  

This work investigated the effects of fumed titanium oxide on thermal stability of nano-silica thermal insulating composites prepared by dry process. The results showed that the composites could keep excellent thermal stability at the temperatures below 800°C. However, when the samples were used at higher temperatures (>800°C), the volume shrinkage increased sharply, which directly led to a serious deformation and then affected thermal insulating properties in applications. The utilization of fumed titanium oxide could significantly improve thermal stability of the composites. When 10wt% fumed titanium oxide was added, the service temperature can increase from 800°C to 900°C. The desirable results would be achieved by adjusting the amount of additives according to practical using temperature. In addition, field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) were employed to characterize the microstructure and phase transformations of the composites treated at different temperatures.


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