Study On Ldhs Modification And Composite Materials For Thermal Stability Of PVC

As a kind of polymer material,Polyvinyl chloride(PVC)has many excellent comprehensive performances.It is widely used in agriculture,construction,communication and daily necessities field,due to its high strength,high dielectric property,wear resistance and low price.However,since the processing temperature is higher than the decomposition temperature,it is easily decomposed during processing,which limits its use to some extent.Therefore,heat stabilizers must be added during the processing.The addition of heat stabilizers can significantly retard or prevent its thermal decomposition,thereby maintaining its good performance.The heat stabilizers currently used mainly include heavy metals such as lead salts,metal soaps,and organotins,which include heavy metals and cause great damage to the human body and the environment.Therefore,there is an urgent need to develop a new type of environmentally friendly,efficient and inexpensive heat stabilizer.Layered double hydroxides(referred to LDHs)are a class of inorganic nanomaterials.Since the first discovery in the 1980s as a PVC heat stabilizer,LDHs thermal stabilizers have been extensively studied.However,there are two problems:(1)In the past,research on PVC thermal stabilizers for LDHs mainly focused on the modulation of metal ions in laminates and the exchange of special inorganic or organic anions in interlayer.There are few reports on the relationship between the morphology of MgAl-LDH and PVC heat stabilizers.(2)LDH is a PVC heat stabilizer for PVC heat stabilizer,which has poor effect on its use alone,and its thermal stability needs further improvement.In order to solve the above problems,we have carried out the following work:(1)Control of particle size of MgAl-LDH and its effect on thermal stability of PVC50-100 nm LDH,200-300 nm LDH and 3-4 ?m LDH were prepared by nucleation and crystallization method,hydrothermal method and urea method.Study on the effect of LDHs particle size on PVC thermal stability by using different particle size LDHs as PVC heat stabilizers.the study found that 200-300nm LDH exhibits excellent thermal stability due to the exposure of suitable surface basic sites.(2)Control of the diameter-thickness ratio of MgAl-LDH and its effect on the thermal stability of PVCOn the basis of the previous work,we control the LDHs in the optimal size range,and prepare a series of LDHs with different diameter-thickness ratios by adjusting the hydrothermal synthesis time.The effect of LDHs diameter ratio on the thermal stabilizer of PVC was studied.The results show that with the decrease of the diameter-thickness ratio of LDHs,the thermal stability of PVC increases gradually,which is related to the alkaline exposure of LDHs.(3)Synthesis of LDH@ZIF-8 new heat stabilizer material and its effect on thermal stability of PVCLDH@ZIF-8 new heat stabilizer material was successfully synthesized by designing a new heat stabilizer material around ZIF-8.The new material combines LDHs with ZIF-8's excellent PVC thermal stability.it shows good thermal stability and can further improve the thermal stability of LDHs.