REVIEW OF THE PHYSICAL AND MECHANICAL CHARACTERISTICS OF POLYURETHANE NANOCOMPOSITES

Polyurethane nanocomposites are promising materials in many industries, they have superior physical and mechanical properties compared to the original polyurethane. This paper presents an analysis of the physical and mechanical properties of polyurethane nano-composites with various types of fillers such as organoclays, carbon nanotubes, polyhedral oligomeric silse-squioxanes, graphene, graphene oxide, polytetrafluoroethylene, and metal nanoparticles. The concentration-dependent effects in changing the structure and properties of polyurethane composites under the influence of the added fillers were also considered. It is noted that the values of physical and mechanical properties are influenced by the uniform distribution of nanofiller particles in the composite and their chemical modification. It was found that with a uniform distribution of nanoparticles in the polymer matrix, the physicomechanical properties of the resulting composites increase.

Composite Micro-Nanoarchitectonics of MMT-SiO2: Space Charge Characteristics under Tensile State

Low density polyethylene (LDPE) is a good insulating material which is widely used in cable materials due to its excellent insulation and processability. However, in the DC high voltage environment, pure polyethylene materials still face many problems, the most serious of which is space charge accumulation. The cable will inevitably be subjected to tensile stress during production, installation and operation. Therefore, it is of great significance to study the effect of stretching on the microstructure and space charge characteristics for polymers and their composites. In this paper, MMT/LDPE micro-composites, SiO2/LDPE nano-composites and MMT-SiO2/LDPE micro-nano-composites were prepared by melt blending. Mechanical stretching was carried out on pure LDPE materials and the above three kinds of composite materials. Each material was stretched according to four stretching ratios, which are 0%, 5%, 10% and 20%. The crystal morphology was observed by polarizing microscope (PLM), the crystallization perfection was tested by differential scanning calorimetry (DSC), and the space charge distribution inside each sample was measured by pulsed electro-acoustic (PEA) method. At the same time, the average charge density and apparent charge mobility for samples during depolarization were calculated and analyzed. The experimental results show that when the pure low density polyethylene sample is not stretched, its crystal structure is loose. Tensile stress can make the loose molecular chains align in LDPE and improve its crystalline structure, which is helpful to restrain the accumulation of space charge inside the sample. For MMT/LDPE, SiO2/LDPE and MMT-SiO2/LDPE composites, their internal crystal structure is compact. Stretching will destroy their original crystal structure at first, and then disorder molecular chains inside the three composite materials. With the increase of stretching ratio, the molecular chains begin to orient along the direction of force, the crystallization tends to be perfect gradually, and the space charge accumulation in samples also decreases. From the calculation results of apparent charge mobility for each sample, with the increase of stretching ratio, the trap depth and trap density inside samples firstly increased and then decreased.

Tribological and Rheological Investigations of MWCNT/PMMA Polymeric Composites and Hybrid Compounds

The Nano scale self-lubricating compounds were prepared by in-situ free radical polymerization with the dispersion of MWCNT ultrasonic molecules embedded in the polymer matrix to enhance the tribological mechanical properties as well as the production of hybrid compounds to detect the tibial changes on the polymer surface, dry friction under the conditions of slip was studied, the friction coefficient was found For hybrid compounds slightly lower than the coefficient of friction of Nano composites under multiple loads and constant velocities, enhancements of Nano composites in rheological behavior were investigated and the influencing factors were determined: shear stress, shear viscosity, as well as shear rates. By using visual inspection, tracking of the behavior of compounds during extrusion was carried out and obtaining the shapes of the threads resulting from extrusion, which are usually important matters whose results depend on many industries.