Basic performance of plastic storage tank series:
1, density: PP is the lowest density of all synthetic resins, only 0.90~0.91g/cm3, is about 60% of PVC density. This means that with the same weight of raw materials can produce more of the same volume of products.
2, mechanical properties: PP tensile strength and rigidity are relatively good, but the impact strength is poor, especially low temperature impact resistance. In addition, if the product is shaped, there is a tendency or stress, the impact strength will be significantly reduced. Although the impact strength is poor, but after filling or enhancement, the mechanical properties of the mechanical properties in many areas can be higher cost of engineering plastics competition.
3, surface hardness: PP surface hardness in the five general plastics, is lower, only better than PE. When the degree of crystallinity is high, the hardness of the corresponding increase, but still less than PVC, PS, ABS, etc..
4, thermal properties: in the five general plastics, PP heat resistance is the best. PP plastic products can work at 100 degrees for a long time, in the absence of external force, PP products are heated to 150 degrees will not deformation. The heat resistance of the PP can be further improved after the use of the nucleating agent to improve the crystallization state, even if it can be used to heat food in the microwave oven.
5, resistance to stress cracking: the residual stress in the molded product, or the product is a long time to work, will cause the stress cracking phenomenon. Organic solvents and surfactants can significantly promote stress cracking. So the stress cracking test was performed in the presence of surface active agents. Commonly used additives for alkyl aryl polyethylene glycol. Experiments show that the PP in the surface active agent of the resistance to stress cracking performance and in the air, there is a good resistance, and the smaller the PP melt flow rate (the greater the molecular weight), the more resistance to stress cracking.
6, chemical stability: PP chemical stability is excellent, the majority of acid, alkali, salt, oxidant are inert. For example, the concentration of phosphoric acid, hydrochloric acid, 40% sulfuric acid and their salts are stable in 100, and only a few strong oxidizing agents, such as smoke and sulfuric acid, can make it change. PP is a nonpolar compound, which is very stable in polar solvents such as alcohols, phenols, aldehydes, ketones and most carboxylic acids, but can not be easily dissolved or swollen in some non polar organic solvents.
7, air tightness (gas barrier): PP on the oxygen, carbon dioxide and water vapor have a certain permeability, compared with Niron (PA) and polyester (PET) have a significant gap, for high barrier plastics, such as EVOH, PVDC, etc.. But compared with other non plastic materials, the air tightness is quite good. By adding a barrier material or in the surface coating of the barrier of the plastic, can greatly improve the air tightness.
8, aging properties: PP molecules exist in the presence of TERT carbon atoms, in the light and heat of the very easy to break down. Unstabilized PP at 150 DEG C is heated more than half an hour, or in the sun exposure for 12 days will be significantly brittle. PP powder without stabilizer in the room to avoid light for 4 months will be severely degraded, emitting a clear sour. In more than 0.2% of the antioxidant before PP powder granulation can effectively prevent degradation in the processing and use of PP in the process of aging. Antioxidant points for the free radical chain reaction terminating agents (also known as the main antioxidant and peroxide decomposition agent (also known as assistant antioxidant) two categories, the main and auxiliary reasonable coordination of the two kinds of antioxidants will play a good synergistic effect. Currently recommend the use of B215 antioxidant is the main antioxidant 1010 (phenolic) and auxiliary antioxidant 168 (Phosphite) were mixed in 1:2 ratio of. In order to prevent the light aging, it is needed to add the ultraviolet ray absorber in PP. It can be used to transform the ultraviolet absorption of wavelength 290~400nm into a long wavelength without damaging. For the buried in the soil or in indoor avoid light used PP plastic products only to join the main and auxiliary antioxidants can, without adding a UV absorber.
9, electrical properties: PP belongs to non polar polymer, with good electrical insulation, and PP water absorption is very low, electrical insulation will not be affected by humidity. The dielectric constant and the loss factor of the PP are very small, which is not affected by the frequency and temperature. The dielectric strength of PP is very high, and it increases with the increase of temperature. These are favorable for electrical insulation materials in wet and hot environment. On the other hand, the surface resistance of PP is very high, and it must be used in some situations.
10, the processing performance is good: PP belongs to the crystalline polymer, not to a certain temperature of its particles will not melt, unlike PE or PVC in the heating process as the temperature increases and softening. Once at a certain temperature, PP particles melt quickly, in a few degrees can be converted into molten state. PP melt viscosity is relatively low, so the process of forming good flow, especially when the melt flow rate is relatively high, the melt viscosity is smaller, suitable for large thin wall injection molding, such as washing machine barrel. PP after leaving the die, if it is slow cooling in the air, it will generate a larger grain, low transparency. The fruit is in the water quench (as follows), the molecular motion of PP is rapidly frozen, can not generate the crystal, the film is completely transparent at this time. PP of the molding shrinkage rate is relatively large, reaching 2%, far greater than ABS plastic (0.5%). The molding shrinkage rate of PP can be changed with the addition of other materials, which need to be considered in the production of injection molding products with the size of the injection.