Preparation And Application Of The Liquid Composite Thermal Stabilizers For PVC

Poly（vinyl chloride）（PVC） is one of the most widely used synthetic resins in the world.Due to its excellent performance and low-cost, PVC has been widely used in various fields ofnational economy and people’s daily life. However, due to their structure defects, the stabilityof PVC during the machining process is poor and PVC is easily to be degraded. Therefore,thermal stabilizer is a necessary additional agent in PVC processing and application.Traditional thermal stabilizers usually contain heavy metal salts such as lead, barium,chromium and so on, which cause certain toxic hazards and damage to the environment andpeople healthy. In recent years, with the increasing conscience of environmental protection,more researchers focused on investigating and developing the new environmental friendly andefficient heat stabilizer. Synthesis of PVC composite liquid thermal stabilizers and theirapplication were investigated in detail in this paper.Metal salts were traditionally prepared by double decomposition, causing a lot ofwastewater. In order to overcome this disadvantage, solid-liquid "one-step" method wasemployed to synthesize a series of environmental-protected iso-octoate metal salts. Thematerial ratio, reaction temperature, reaction time and adding quantities of accelerant werestudied and the optimal synthetic condition of each metal salt were obtained. The complexperformances among main stabilizers like iso-octoate magnesium, sodium iso-octoate andzinc iso-octoate were discussed. Optimized binary sodium/zinc system with ratio of Na/Zn=1/1（ion mass ratio） was obtained. On this base, diisooctyl phenyl phosphite （PDOP）,epoxidized soybean oil （ESBO） and epoxy fatty acid methyl ester （EFAME） liquidbeta-diketone were added as associant stabilizers. Results showed that the synergy effect wasfound when PDOP （15%）, ESBO （10%） and beta-diketone （3%） were added.Thermo gravimetric was used to analyze and discuss the thermal decomposition kineticsin both blank PVC and PVC with thermal stabilizers systems. Based on the Doyle equation,we can get the activation energy of PVC degradation under different thermal weightlessnessrate of alpha （30%,60%and80%）, which can reflect the degree of PVC degradation andfurther prove the thermostability efficiency of PVC with thermal stabilizer in theory.Through the determination and analysis of physicochemical properties, the qualityparameters were obtained. The safety and toxicity assessment of two Mg/Zn and Na/Zn liquidcomposite thermal stabilizers were conducted by the third party testing institutions, whichshowed that the amounts of RoHs, PAHs and six phthalates all met the European Unionenvironmental indicators. The LD₅₀values of Mg/Zn and Na/Zn liquid composite thermalstabilizer were respectively1260mg/Kg and1470mg/Kg, which indicated that these twomaterials were environmental friendly.According to the formulation design and optimization, the optimized formula applied inPVC soft products contains potassium zinc （62.5%）, calcium iso-octoate （12.5%）, iso-octoatezinc （5.0%）, PDOP （15.0%） and beta-diketone （5.0%）. The static thermal stability time at180℃could reach65.4min. During the simulation process of PVC gloves production, thedynamic plasticizing time keep up to10min at200℃. This stabilizing effect is better thanthat of the other thermal stabilizers on the market. This recipe has been introduced to the industrialized trial-production of PVC gloves. A transparent product with no bubble andprecipitation was obtained, which showed excellent thermal stability.