【作者】 徐辉；

【导师】 韩景宾；

【作者基本信息】 北京化工大学 ， 化学， 2025， 硕士

【摘要】 塑料作为一类理化性能优异的高分子材料被广泛应用于国民经济的诸多行业。然而,聚丙烯(PP)和低密度聚乙烯(LDPE)等聚烯烃塑料在加工、储存和应用过程中在机械剪切、热和氧气作用下易发生氧化降解,导致分子链断裂或交联,造成材料黄变、脆化及力学性能的不可逆衰退,从而缩短其使用寿命。此外,聚烯烃塑料的老化造成废弃物累积,进一步加剧了生态环境污染,威胁生物安全。为抑制聚合物分子链的氧化降解,通常需向塑料中加入抗氧化剂。然而,传统的低分子量抗氧化剂易迁移出聚合物表面,导致其抗氧化性能逐渐减弱。近年来,无机载体固定化策略引起了广泛关注。层状双金属氢氧化物(水滑石,LDH)因其制备工艺简单、结构可调、环境友好、优异的抗迁移性能而展现出巨大的潜力。然而,LDH表面富含羟基,其亲水特性导致在聚合物基体中易发生界面不相容,分散性较差,制约了其实际应用。本论文针对PP和LDPE的热氧老化问题,利用抗氧化剂对LDH进行表面改性:一方面通过LDH的锚定作用有效抑制抗氧化剂的迁移和析出;另一方面借助抗氧化剂高效的自由基清除性能,从而协同提升聚合物的热氧化稳定性。本论文具体研究内容和结果如下:1、抗氧化剂AO功能化LDH增强聚丙烯的热氧化稳定性通过脱水缩合反应将抗氧化剂3-(3,5-二叔丁基-4-羟基苯基)丙酸(AO)表面功能化LDH(LDH-AO)作为PP基体的无机纳米填料。LDH-AO通过协同作用不仅有效改善了LDH在PP基体中的分散性,显著增强PP的热氧化稳定性和氧气阻隔性能,同时也大幅度提升了抗氧化剂的抗迁移性能。在0.5 wt%LDH-AO的低添加量下,复合材料的氧化诱导时间延长至纯PP的2.2倍,初始热分解温度提升近30℃,且抗迁移性能提高2倍。经150℃加速热氧化老化500 h后,通过羰基指数和XPS分析证明,PP/LDH-AO的氧化程度显著低于纯PP。这项工作为开发低成本、长效耐高温聚合物材料提供了一种新策略。2、受阻酚类抗氧化剂BHT钝化LDH以提升低密度聚乙烯的热氧化稳定性通过异佛尔酮二异氰酸酯(IPDI)桥联作用,将受阻酚抗氧化剂2,6-二叔丁基-4-羟甲基苯酚(BHT)共价接枝到LDH表面,成功构筑了LDPE/LDH-BHT复合材料。当添加0.5 wt%LDH-BHT时,复合材料的氧化诱导时间(OIT)提升至纯LDPE的3.2倍,气体阻隔性能和热稳定性均显著提高。经100℃加速热氧化老化500 h后,LDPE/LDH-BHT的羰基指数增幅显著低于纯LDPE,印证其长效热氧化稳定性。此外,LDH-BHT在提升LDPE导热性能的同时,保持了其优异的电绝缘性能。本工作通过分子设计实现热氧化稳定性、气体阻隔性和导热性能的协同提升,为多功能聚合物复合材料的开发提供了新思路。更多还原

【Abstract】 Plastics,as a class of polymeric materials with excellent physicochemical properties,are widely applied in many industries of the national economy.However,polyolefin plastics such as polypropylene(PP)and low-density polyethylene(LDPE)are prone to oxidative degradation under the action of mechanical shear,heat,and oxygen during processing,storage,and application,leading to molecular chain scission or cross-linking,causing irreversible deterioration of material yellowing,embrittlement,and mechanical properties,thus shortening their service life.In addition,the aging of polyolefin plastics causes waste accumulation,further exacerbating ecological environmental pollution and threatening biosafety.To inhibit the oxidative degradation of polymer chains,antioxidants are usually added to plastics.However,traditional low-molecular-weight antioxidants easily migrate out of the polymer surface,leading to a gradual weakening of their antioxidant properties.In recent years,the inorganic carrier immobilization strategy has attracted widespread attention.Layered double hydroxide(hydrotalcite,LDH)shows great potential due to their simple preparation process,tunable structure,environmental friendliness,and excellent migration resistance.However,the surface of LDH is rich in hydroxyl groups,and its hydrophilic properties lead to easy interfacial incompatibility and poor dispersibility in polymer matrices,restricting its practical applications.Aiming at the thermo-oxidative aging problems of PP and LDPE,this thesis uses antioxidants to modify the surface of LDH:on the one hand,the anchoring effect of LDH effectively inhibits the migration and exudation of antioxidants;on the other hand,the efficient free radical scavenging performance of antioxidants is leveraged to synergistically enhance the thermo-oxidative stability of polymers.The specific research contents and results of this thesis are as follows:1.Antioxidant AO-functionalized layered double hydroxide enhances the thermo-oxidative stability of polypropyleneLayered double hydroxides(LDH)functionalized with the antioxidant 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid(AO)was proposed as a hybrid nanofiller for the PP matrix.The LDH-AO composite exhibits synergistic effects:it not only improves the dispersion of LDH in the PP matrix but also enhances the thermo-oxidative stability and oxygen barrier properties of PP,while significantly suppressing antioxidant migration.At a low loading of 0.5 wt%LDH-AO,the oxidation induction time(OIT)of the composite increased to 2.2 times that of pure PP.Furthermore,the initial thermal decomposition temperature(T_i)increased by nearly 30°C,and the migration resistance was enhanced twofold.After 500 h of accelerated thermo-oxidative aging at 150°C,PP/LDH-AO showed a significantly lower oxidation degree than pure PP,as confirmed by both carbonyl index and XPS analyses.This research introduces a novel strategy for developing cost-effective,long-term,high-temperature-resistant polymeric materials.2.Hindered phenolic antioxidant BHT passivates the LDH to enhance thermo-oxidative stability of low-density polyethyleneThrough the bridging effect of isophorone diisocyanate(IPDI),the hindered phenolic antioxidant 2,6-di-tert-butyl-4-hydroxymethylphenol(BHT)was covalently grafted onto the surface of LDH,successfully constructing an LDPE/LDH-BHT composite.When 0.5 wt%LDH-BHT is added,the oxidation induction time(OIT)of the composite is increased to 3.2 times that of pure LDPE,and both gas barrier properties and thermal stability are significantly improved.After 500 h of accelerated thermo-oxidative aging at 100°C,the increase in carbonyl index of LDPE/LDH-BHT is significantly lower than that of pure LDPE,confirming its long-term thermo-oxidative stability.In addition,LDH-BHT enhances the thermal conductivity of LDPE while maintaining its excellent electrical insulation properties.This work achieves the synergistic improvement of thermo-oxidative stability,gas barrier property,and thermal conductivity through molecular design,providing new insights for the development of multifunctional polymer composites.更多还原