The mechanical properties of zirconia ceramic polyethylene are general, the tensile strength is low, the creep resistance is not good, and the impact resistance is good. Impact strength LDPE>LLDPE>HDPE, other mechanical properties LDPE<LLDPE<HDPE. It is Laser Drilling Electronic Ceramic Substrate Strap Board mainly affected by density, crystallinity and relative molecular weight. With the improvement of these indexes, its mechanical properties increase. Environmental stress cracking resistance is not good, but when the relative molecular weight increases, it improves. Good puncture resistance, of which LLDPE is the best. The heat resistance of polyethylene is not high, Laser Drilling Electronic Ceramic Substrate Strap Board and it improves with the increase of relative molecular weight and crystallinity. The low temperature resistance is good, and the brittleness temperature can generally reach below -50℃; and with the increase of relative molecular weight, the lowest can reach -140℃. The linear expansion coefficient of polyethylene is large, up to (20~24)×10-5/K. The thermal conductivity is high. Because polyethylene has no polarity, it has excellent electrical properties such as Laser Drilling Electronic Ceramic Substrate Strap Board low dielectric loss and high dielectric strength. It can be used as frequency modulation insulation material, corona resistant plastic, and high voltage insulation material. Polyethylene is an alkane inert polymer with good chemical stability. It is resistant to acid, alkali, and salt solutions at room temperature, but it is not resistant to strong oxidants such as fuming sulfuric acid, concentrated nitric acid and chromic acid. Polyethylene is insoluble in general solvents below 60°C, but it will swell or crack if it contacts with aliphatic hydrocarbons, Laser Drilling Electronic Ceramic Substrate Strap Board aromatic hydrocarbons, halogenated hydrocarbons, etc. for a long time. When the temperature exceeds 60°C, it can be dissolved in a small amount of toluene, amyl acetate, trichloroethylene, turpentine, mineral oil and paraffin; the temperature is higher than 100°C, it is soluble in tetralin.
As the polyethylene molecule contains a small amount of double bonds and ether bonds, the sun and rain will cause aging, and antioxidants and light stabilizers need to be added to improve it. Because LDPE and HDPE have good fluidity, low processing temperature, moderate viscosity, and low decomposition temperature, they will not decompose at a high temperature of 300°C in an inert gas, so they are plastics with good processing properties. However, Laser Drilling Electronic Ceramic Substrate Strap Board the viscosity of LLDPE is slightly higher, and the motor power needs to be increased by 20% to 30%; melt fracture is likely to occur, and the gap between the die and the processing aid must be increased; the processing temperature is slightly higher, which can reach 200-215°C. Polyethylene has low water absorption and does not require drying before processing.
Polyethylene melt is a non-Newtonian fluid, and its viscosity varies little with temperature, while the increase in shear rate decreases quickly and shows a linear relationship, of which LLDPE decreases the slowest.
Polyethylene products are easy to crystallize during the cooling process, so pay attention to the mold temperature during the processing. In Laser Drilling Electronic Ceramic Substrate Strap Board order to control the crystallinity of the product, make it have different properties. The molding shrinkage rate of polyethylene is large, which must be considered when designing the mold. The modified varieties of polyethylene mainly include chlorinated polyethylene, chlorosulfonated polyethylene, cross-linked polyethylene and blended modified varieties
Chlorinated polyethylene is a random chloride obtained by partially replacing the hydrogen atoms in polyethylene with chlorine. Chlorination is carried out under the initiation of light or peroxide, and is mainly produced by aqueous suspension method in industry. Due to the differences in the molecular weight and distribution of the raw material polyethylene, the degree of branching, the degree of chlorination after chlorination, the distribution of chlorine Laser Drilling Electronic Ceramic Substrate Strap Board atoms and the residual crystallinity, chlorinated polyethylene can be obtained from rubber-like to hard plastic-like. The main purpose is to be used as a modifier of polyvinyl chloride to improve the impact resistance of polyvinyl chloride. Chlorinated polyethylene itself can also be used as electrical insulation material and ground material.
What are the properties of zirconia ceramics?
2020 11/02