Views:1 Author:Site Editor Publish Time: 2019-09-18 Origin:Site
Do you know the key performance of PVC? It has good electrical insulation properties, can be used as raw materials in various industries, and chemical stability is also very good. You can find more information below.
PVC pipe fitting physical and chemical properties
Polyvinyl chloride has poor thermal stability and light resistance. Hydrogen chloride starts to decompose at 150 ° C, and an adverse reaction occurs with the amount of plasticizer. In addition, the effect of the pigment on PVC pipe fitting is reflected in whether the pigment reacts with PVC pipe fitting and other components constituting the PVC pipe fitting product, and the pigment itself is resistant to migration and heat. Some of the ingredients in the colorant may contribute to the degradation of the resin.
For example, iron ions and zinc ions are catalysts for the degradation reaction of PVC resins. Therefore, the use of iron oxide (red, yellow, brown and black) pigments or zinc oxide, zinc sulfide and lithopone white pigments reduces the thermal stability of PVC resins. Some colorants may interact with degradation products of PVC resins. For example, the ultramarine pigments have poor acid resistance, so in the process of PVC pipe fitting coloring, they will interact with the hydrogen chloride generated by the decomposition of PVC and lose the color they deserve.
Mobility occurs only in plasticized PVC articles and when dyes or organic pigments are used. The so-called migration is a partially soluble dye or organic pigment present in the surrounding solvent. The plasticizer penetrates the surface of the PVC pipe fitting product, and the dissolved dye particles are also brought to the surface of the product, thus causing bleed, solvent. Bleeding or blooming. Another problem is "fouling." It means that the coloring agent is freed from the system during the coloring process because it is poorly compatible or not compatible at all, and is deposited on the surface of the processing equipment.
The natural color is yellowish translucent and shiny. Transparency is better than polyethylene, polypropylene, and is different from polystyrene. It is divided into soft and hard polyvinyl chloride according to the amount of additives. The soft products are soft and tough, and the hand feels sticky. The hardness of hard products is higher than that of low density polyethylene. Below polypropylene, whitening occurs at the bend. Stable; not easily corroded by acid or alkali; more resistant to heat.
Polyvinyl chloride has flame retardancy (flame retardancy value of 40 or more), high chemical resistance (concentrated hydrochloric acid, 90% sulfuric acid, 60% nitric acid and 20% sodium hydroxide), mechanical strength And the advantages of good electrical insulation. Polyvinyl chloride has poor stability to light and heat. The softening point was 80 ° C and decomposition began at 130 ° C. Without heating the stabilizer, the polyvinyl chloride starts to decompose at 100 ° C, and decomposes faster at 130 ° C or higher.
It is decomposed by heat to release hydrogen chloride gas (hydrogen chloride gas is a toxic gas) to discolor, from white → light yellow → red → brown → black. The ultraviolet rays and oxygen in the sunlight cause photo-oxidative decomposition of the polyvinyl chloride, thereby lowering the flexibility of the polyvinyl chloride and finally becoming brittle. It is not difficult to understand from here why some PVC pipe fitting turn yellow and become brittle after a long time.
In fact, such PVC pipe fittings have many other properties, and its advantages are really many, you can safely choose it as your engineering raw material.