邻香兰素基稳定剂的制备及其在聚丙烯中的应用

Preparation of O-vanillin-based stabilisers and their application in polypropylene

邻香兰素(OVA)是一种天然来源的酚类化合物,具有独特的酚醛结构。以OVA、腺嘌呤(Ade)和2,6-二氨基嘌呤(26-DAPY)为原料,通过席夫碱反应合成了两种新型生物基稳定剂—OVA-嘌呤类席夫碱化合物(SB1和SB2),并通过密炼机分别将其与聚丙烯(PP)熔融共混后热压制样。采用傅里叶变换红外光谱和核磁共振氢谱表征SB1和SB2的化学结构;通过热重分析仪测试SB1和SB2的热稳定性。通过测试PP热氧稳定性、起始氧化温度(IOT)、氧化诱导时间(OIT)、光氧老化后力学性能以及PP膜紫外透过率研究了SB1和SB2对PP的耐热氧性能、光氧稳定性能和紫外屏蔽性能的影响。通过理论计算键解离能、分子最高占据轨道和最低未占据轨道之间能隙评价抗氧活性。结果表明,SB1和SB2热失重5%的温度分别为202℃和219℃,高于OVA(144℃);SB1的加入能够提高PP热氧稳定性,与纯PP相比,添加SB1后材料的IOT和OIT分别提高7~19℃和2.2~4.9 min;添加0.1%的SB1或SB2对PP均表现出光氧稳定作用;PP膜紫外透过试验表明,添加1.0%的SB1或SB2的PP膜在250~400 nm间透过率分别降至6.0%和6.2%以下。

O-vanillin(OVA)is a naturally phenolic compound with a unique phenol-aldehyde structure.Two novel bio-based stabilisers,O-vanillin-purine schiff base compounds(SB1 and SB2)were synthesized via schiff base reaction using OVA,adenine(Ade),and 2,6-diaminopurine(26-DAPY)as raw materials.The samples were then hot-pressed by melt blending with polypropylene(PP)using a closed plastic mixer,respectively.Fourier transform infrared spectroscopy(FTIR)and nuclear magnetic resonance hydrogen spectrum(1H NMR)were used to characterise the chemical structures of SB1 and SB2.The thermal stability of SB1 and SB2 was tested by thermogravimetric analysis.The thermal oxidative stability,initial oxidation temperature(IOT),oxidation induction time(OIT),tensile properties after photo-oxidative aging,and ultraviolet transmittance of the PP films were studied to investigate the effects of SB1 and SB2 on the thermal oxidative stability,photo-oxidative stability,and ultraviolet shielding performance of PP.The antioxidant activity was evaluated by theoretical calculation of bond dissociation energy,highest occupied molecular orbitallowest unoccupied molecular orbital energy gap.The results indicate that the temperatures corresponding to 5%thermal weight loss for SB1 and SB2 are 202℃and 219℃,respectively,higher than OVA(144℃).The addition of SB1 improves the thermal oxidative stability of PP.Compared to pure PP,the addition of SB1 increases the initial oxidation temperature(IOT)and oxidation induction time(OIT)by 7-19℃and 2.2-4.9 min,respectively.The addition of 0.1wt%of SB1 or SB2 exhibits photo-oxidative stabilization effects on PP.In the UV transmittance test of PP films,the transmittance of PP films with the addition of 1.0 wt%of SB1 or SB2 is reduced to less than 6.0%and 6.2%in the range of 250-400 nm,respectively.