【作者】 李皓；

【导师】 赵建青；

【作者基本信息】 华南理工大学 ， 材料学， 2014， 博士

【摘要】 工程塑料的改性过程中，由于不同的聚合物之间、聚合物与玻纤或无机功能填料之间存在极性和界面差别，所得聚合物合金或复合材料很难达到高的性能指标，因此工程塑料共混、复合化改性的关键是解决体系各组分的相容问题。适当地使用增容剂可以一定程度地解决该问题，但目前常用增容剂在250°C以下加工温度下使用效果很好，超过该温度则分解严重甚至炭化，因此耐高温增容剂是满足工程塑料高性能化和功能化改性的需要。聚二甲基硅氧烷（PDMS）由于Si-O主链及侧链的甲基的存在具有高弹性、高疏水性、低表面张力和极好的热稳定性而被广泛应用在航空航天、建筑、电子电器、汽车工业等领域。但其低表面能及与其他聚合物较低的相容性限制了它的应用范围。聚硅氧烷-丙烯酸酯共聚物能明显改善PDMS这一缺点，同时能维持其良好的耐热性和耐候性。因此近年来通过乳液聚合方法制备聚硅氧烷-丙烯酸酯共聚物是一研究热点。本文通过乳液聚合的方法合成了两种聚硅氧烷-丙烯酸酯共聚物，包括聚二甲基硅氧烷-甲基丙烯酸甲酯接枝共聚物（PDMS-g-PMMA）和聚二甲基硅氧烷-苯乙烯-甲基丙烯酸甲酯接枝共聚物（PDMS-St-MMA），并分别对其热稳定性进行了研究，分析其结构对热稳定性的影响。同时将这两种共聚物用于PC/ABS体系，观察这两种共聚物对于PC/ABS体系有无增容、阻燃作用等。1.通过D4和vD4的开环反应，制备侧链含有乙烯基的聚硅氧烷乳液，并与甲基丙烯酸甲酯反应以制备聚二甲基硅氧烷-甲基丙烯酸甲酯接枝共聚物。通过考察和优化合成过程中各个影响因素，确定了制备耐热性能较好的PDMS-g-PMMA适宜条件为，聚硅氧烷的分子量约为50000，聚硅氧烷和甲基丙烯酸甲酯单体的质量比为5:5，开环反应时间与接枝反应时间均为4h。通过TGA测试发现该条件下制备的PDMS-g-PMMA在氮气气氛下5%的热失重温度可达到357oC，且热失重过程明显分为两个阶段。通过TGA-FTIR和PY-GC-MS测试证明了在PDMS-g-PMMA的热失重过程中阶段I和阶段II分别代表着PMMA链段和PDMS链段的热分解，且在PDMS-g-PMMA热失重过程中主链PDMS链段的分解是在PMMA链段大部分分解完后才开始发生。2.在PDMS-g-PMMA的基础上引入耐热性能更好的苯乙烯，通过同样的乳液聚合方法制备了聚二甲基硅氧烷-苯乙烯-甲基丙烯酸甲酯接枝共聚物。通过TGA分析，发现PDMS-St-MMA在氮气气氛下的5%热失重温度高达373oC，且热失重过程也明显分为两个阶段。TGA-FTIR测试证明了在PDMS-St-MMA的热失重过程中阶段I和阶段II的热失重过程分别代表着St-MMA结构链段和PDMS链段的热分解，且在PDMS-St-MMA热失重过程中主链PDMS链段的分解是在St-MMA结构链段大部分分解完后才开始发生。3.将PDMS-g-PMMA和PDMS-St-MMA两种共聚物用于PC/ABS(90/10，质量比，下同)体系。通过TGA测试发现添加了PDMS-g-PMMA和PDMS-St-MMA后，PC/ABS合金的耐热性能得到了提高。通过力学性能测试发现，加入PDMS-St-MMA后PC/ABS合金的缺口冲击强度有明显的提升，而添加PDMS-g-PMMA-反而使得PC/ABS合金的缺口冲击强度大幅度下降。通过表面形态的观察发现，添加PDMS-St-MMA作为增容剂后，PC/ABS合金的低温脆断横截面比较平滑，ABS分散相的分散尺寸减小，而且分布均匀，相界面比较模糊不清；而PDMS-g-PMMA加入后PC/ABS合金的低温脆断面依然不平滑。4.将PDMS-St-MMA作为增容剂，应用在PC/ABS/PPSi(三(1-氧代-2,6,7-三氧杂-1-磷杂双环[2.2.2]辛烷-4-亚甲氧基)苯基硅烷)阻燃体系，结果表明，PDMS-St-MMA在提高PC/ABS合金的相容性的同时并不会影响原体系的阻燃性能；而市场上常用的增容剂MBS添加后会降低合金的阻燃性能。通过热稳定性分析发现，PDMS-St-MMA在增容的同时，也能有效提升阻燃剂PPSi和PC/ABS的分解温度，能有效降低ABS和PPSi的热分解速率，使得PC/ABS合金第一阶段分解完后的残炭量较高。通过对残炭形貌及元素分析发现，添加了PDMS-St-MMA的试样残炭表面孔洞明显消失，形成了一层致密的保护层，同时残炭表面硅元素明显增多，说明PDMS-St-MMA加入后，在燃烧时硅元素更多地向表面迁移，从而能够在表面形成致密稳定的含硅焦化炭保护层，加强了隔热、隔氧，阻止了聚合物热降解挥发物的逸出和防止熔滴出现等。更多还原

【Abstract】 Due to the different polar and interface between different polymers, polymers and glassfiber, polymers and inorganic fillers in the modification process of engineering plastics, theresultant polymer alloy or composite materials are difficult to achieve high performance.Therefore, improving the compatibility between the components is the key to themodification. Adding compatibilizer appropriately can solve the problem to some extent.However, currently used compatibilizers only can be used below250oC because they candecompose seriously at high temperature. Thus, preparing high temperature resistantcompatibilizers is receiving more and more attention to meet the modification needs ofengineering plastics.Polydimethylsiloxane (PDMS) containing Si-O-Si main chain and methyl side groupsprocesses many excellent properties, such as high flexibility and hydrophobicity, low surfacetension and excellent thermal stability. It is widely used in the aerospace, construction,electronics, automotive and medical field as silicone, silicone oil and silicone rubber. But thelow surface energy, poor solvent resistance and poor compatibility with other polymers limitits applications to some degree. The combination of PDMS with polyacrylates cansubstantially increase the adhesion, strength, solvent resistance of PDMS, and also maintainthe original excellent heat resistance, weather resistance etc. The research onPDMS-polyacrylate copolymer has been of importance and much interest during the past fewdecades.In this paper, polydimethylsiloxane-graft-poly(methyl methacrylate) copolymer(PDMS-g-PMMA) and polydimethylsiloxane-g-styrene-g-methyl methacrylate copolymer(PDMS-St-MMA) were synthesized and the thermal stabilities were also studied. Then thecopolymers were used in PC/ABS and the compatibilization and flame retardancy wereinvestigated.1. The polysiloxane emulsion containing vinyl side chain was obtained by the ring-openingreaction of D4and vD4. Then the polysiloxane reacted with methyl methacrylate to obtainPDMS-g-PMMA. By making effort to optimize the experimental parameters of synthesizing PDMS-g-PMMA, the suitable experimental condition to synthesize PDMS-g-PMMA withgood heat resistance was obtained and showed as follow: the molecular weight ofpolysiloxane was about50000, the mass ratio of polysiloxane and methyl methacrylate was1:1, the ring-opening reaction and grafting reaction were both reacted for4hours. TGAanalyses indicated that PDMS-g-PMMA possesses greatly improved thermal stability, itsdegradation temperatures at5%weight loss were up to357°C. A two-stage thermaldegradation behavior due to PMMA graft chain and PDMS main chain was confirmed byTGA-FTIR and PY-GC-MS results, and the degradation of PDMS chain happens only afterPMMA chains decomposed mostly.2. PDMS-St-MMA was synthesized through the same preparing method ofPDMS-g-PMMA. TGA analyses indicated that PDMS-St-MMA possesses greatly improvedthermal stability than PDMS-g-PMMA, its degradation temperatures at5%weight loss wereup to373°C. A two-stage thermal degradation behavior due to PMMA graft chain and PDMSmain chain was also confirmed by TGA-FTIR result, and the degradation of PDMS chainhappens only after St-MMA chains decomposed mostly.3. PDMS-g-PMMA and PDMS-St-MMA were used inPolycarbonate-acrylonitrile-butadiene-styrene (PC/ABS=90/10), and improved thermalstability of PC/ABS alloy were found. The mechanical properties testing showed that theincorporation of5wt%PDMS-St-MMA leads to an increase in the impact strength ofPC/ABS, but the incorporation of5wt%PDMS-g-PMMA caused a sharply decrease of theimpact strength. SEM morphologies of the impact fractured section showed that the size ofdispersed ABS domains was reduced and the phase boundaries were difficult to be observedwith the addition of PDMS-St-MMA, but the fracture surface was also uneven with theaddition of PDMS-g-PMMA.4. PDMS-St-MMA was used as a compatibilizer in flame-retardant PC/ABS which usedPPSi as flame retardant. It is noticed that the adding of the commonly used compatibilizerMBS in PC/ABS/PPSi reduced the flame retardancy of PC/ABS. On the contrary, the impactstrength of PC/ABS was significantly improved by the aid of PDMS-St-MMA and moreover the flame retardancy was maintained. TGA analyses showed that the addition ofPDMS-St-MMA elevated the degradation temperature and decreases considerably the weightloss in the first degradation stage. Through SEM/EDX analysis of the residue surface, acoherent vitreous layer was formed after burning due to the loading of PDMS-St-MMA.Meanwhile a higher silicon percentage of the residue surface was found. The laye can shieldthe underlying polymer from attack by oxygen and radiant heat and also prevent the escape ofvolatiles, resulting in better flame retardancy.更多还原