Synthesis And Characterization Of Several Colored Layered Double Hydroxides Used As PVC Thermal Stabilizer

Layered double hydroxides (LDHs) are a kind of typical lamellar structure inorganic materials consisting of positively charged metal hydroxide sheets, intercalated anions and water molecules. Its general formula can be represented by [M2+1-xM3+x(OH)2]x+An-x/n·yH2O, where M2+ stands for divalent metal cation and M3+stands for trivalent metal cation, An- is intercalated anions, y represents the amount of crystal water. Due to the particularity of its structure and composition, the layered double hydroxides have some special chemical properties and have been widely used in various fields. When the layered double hydroxides are decomposed by the heat, the layered double hydroxides absorb a large amount of heat and release a great amount of carbon dioxide to decrease the concentration of oxygen on the surface of polymer materials, and make the combustible material surface form loose carbide layer, which prevents the transfer of the polymer surface heat. It is a kind of non-toxic, low smoke, and environmental flame retardant, which can be used as flame retardant or postpone the combustion process. Moreover, due to the basic center of the surface is able to absorb HCl, and can prevent the polyvinyl chloride autocatalytic effect and the formation of free radicals terminate chain activity, which will extend the thermal stability of polyvinyl chloride polymer materials. Thus it can be used as thermal stabilizer. Because of its simple preparation, raw materials cheap, economic and environmental protection, it is being widely used in plastic processing industry and has a good development prospect.As a kind of plastic additives, if it can make the plastic color and help people to identify the purpose and direction, it is very meaningful in the cable application. In this paper, several layered double hydroxides have been researched including preparation process, surface modification and the effect of as thermal stabilizer in the polyvinyl chloride plastic. The LDHs MgFe_CO3, MgCr_CO3, NiAl_Cl have been synthesized by a green route, they have been characterized by XRD,FT-IR, UV-vis, TG-DTA, which shows the typical lamellar structure and good crystalline.In order to improve the compatibility between layered double hydroxides inorganic materials and polymer materials, stearic acid was used as surface modification agent to modify MgFe_CO3, MgCr_CO3, NiAl_Cl LDHs. Moreover, it determines the modification temperature, time and modifier dosage through the activation index test. The experimental results show that the samples have best modification effect when the temperature is 100?, the reactive time is 1.5 hours and modifier dosage is 6 wt%.Finally, the modified layered double hydroxide samples were added into the polyvinyl chloride plastic and were mixed for four minutes under the 160? of rolling temperature, and then were cut into 2 centimeters×2 centimeters in order to get polyvinyl chloride sample sheets. The thermal stability of samples were tested under 180? in the thermal aging test chamber. The sample colors were observed every ten minutes. It indicates that MgCr_CO3 sample color will begin turn in the late thermal aging test when the aging time was 40 minutes, and almost turned red at 90 minutes. The MgFe_CO3 sample color will begin turn in the late thermal aging test when the aging time was 50 minutes, and almost turned black at 90 minutes.