The Preparation And Application Of Pentaerythritol-lanthanum And Pentaerythritol-aluminum As Novel Thermal Stabilizers For Rigid Poly (Vinyl Chloirde)

Poly(vinyl chloride)(PVC) is widely used in many fields due to its excellentcomprehensive performance and low cost, however, because of the drawbacks inits structure PVC will dehydrochlorinate during the processing, which will lead tothe degradation of PVC. Researchers have tried many ways to solve this problemduring which adding thermal stabilizers into PVC is one of the most efficientmethods. Recently, the commonly used stabilizers include lead salts, organic tin,metal soaps, rare earth stabilizers and organic compounds. However, because ofthe high toxicity of lead salts, their application is limited; though the thermalstability of organic tin is excellent, the lubricity of the products is poor and it isonly used in transparent products; due to the high cost, the use of rare earthstabilizers is restricted; though metal soaps is non-toxic, the thermal stability of itis less effective. Therefore, it is necessary to develop a new thermal stabilizerwhich not only improves the thermal stability of PVC but also non-toxic.In this paper, new thermal stabilizers which named pentaerythritol-lanthanum(PE-La) and pentaerythritol-aluminum (PE-Al) were synthesized frompentaerythritol and metal oxide, the reaction process of pentaerythritol and metaloxide were simulated by TG-MS and what’s more its molecular structure and grainsize was investigated with FTIR and SEM. The thermal stability of PVC stabilizedwith PE-Al, PE-La or complex thermal stabilizer was tested by Congo red test,thermal gravimetric analysis （TGA）, conductivity test, thermal aging test andUV-visible spectroscopy.1. In this paper, PE-La and PE-Al were synthesized by solid-state reaction. Acertain quantity of pentaerythritol and metal oxide were added into a high-speedmixer for intensive mixing, transfer the mixture into a three-necked flask and thenadd a defined amount of water-carrying agent, the mixture was stirred vigorouslyat190~200oC for2~3hours, pick up the suction to take out excess water-carryingagent. Take out the product to crash and dry for4h at80oC. The optimal reactiontemperature for PE-Al was200±5oC and for PE-La was190±5oC.2. The experiment results of PE-Al: SEM images showed that compared withthe simple of alumina, the average size reduced significantly and got more uniform,moreover, the shapes of PE-Al particles were more spherical. FTIR suggested thata new Al-O appeared. The Congo red test showed that the optimum amount ofPE-Al was3.84phr and the thermal stability time was52.86min in this condition when used lonely. In comparison with commercial thermal stabilizers, addition ofPE-Al could significantly prolong static stability time of PVC, reduce weight lossand improve the initial color of PVC films. The compound compositionexperiment results indicated that the synergistic effect between PE-Al and CaSt2or ZnSt2was excellent when they were used together, not only the initial color ofPVC films can be improved, but the static stability time can be extended and whenthe weight ratio of PE-Al/ZnSt2was3/1or the ratio of PE-Al/CaSt2was3/1, thesynergistic effect was best, however, though mixing PE-Al with β-diketone canobtain long thermal stability time, the initial color was undesirability. Throughthese comparisons the synergistic effect between PE-Al and ZnSt2was the bestwhen the weight ratio was3/1.3. The experiment results of PE-La: FTIR suggested that a new La-Oappeared. The Congo red test showed that the optimum amount of PE-La was3.6phr and the thermal stability time can reach to31.99min when used lonely.UV–visible spectroscopy test showed that in comparison with commercial thermalstabilizers the combination of PE-La can decrease the concentration of theconjugated bonds of PVC; TGA tests, conductivity test and thermal aging testshowed that with the addition of PE-La ont only the weight loss can be rejected;the induction time can be extended, what’s more the initial color of PVC films canbe improved. The compound composition experiment results indicated that theweight ratio of PE-La and ZnSt2was3/1, the synergistic effect was best, not onlyimprove the initial color but can extend the thermal stability time; when theweight ratio between PE-La and CaSt2was2/2the synergistic effect was good butweaker than PE-La/ZnSt2; when PE-La was compounded with β-diketone theinitial color was unsatisfactory but the long-term thermal effect was good.