【作者】 伍鹏；

【导师】 赵建青； 王浩江；

【作者基本信息】 华南理工大学 ， 材料工程（专业学位）， 2022， 硕士

【摘要】 聚碳酸酯（PC）具有优异的透明、耐热和抗冲击性能等,在移动通信、医疗器械和航空航天等领域有着广泛的应用,但其表面硬度较低和易刮伤。而聚甲基丙烯酸甲酯（PMMA）具有较高表面硬度,并且拥有更优异的透明性能,将其与PC共混制成PC/PMMA合金,有望在保证PC透明性能的前提下,解决其表面硬度低的问题。但PC和PMMA相容性较差,折光指数也存在较大差别,简单共混得到的合金往往不透明。本论文使用酯交换催化剂Sn Cl₂改善PC和PMMA间的相容性,制备兼具高表面硬度和优良透明性能的PC/PMMA合金。进一步,将更高硬度的无机刚性粒子纳米二氧化硅（SiO₂）与PMMA共混,并加入分散剂Si-DPF,改善纳米SiO₂在基体中的分散性,以期获得拥有更高表面硬度的透明SiO₂/PMMA复合材料,并将其代替PC/PMMA合金中的PMMA组分,最终制备具有更高表面硬度、优良透明、力学、加工和热性能的SiO₂-PMMA/PC复合材料,解决表面硬度低所带来的PC应用受限问题。（1）探究Sn Cl₂对PC和PMMA间相容性的影响及其机理,并对比研究了共混工艺和Sn Cl₂加入前后PC的表面硬度、透明、力学、加工和热性能的变化。研究结果表明,与20 wt%的PMMA共混后,PC的表面硬度得到有效提高,铅笔硬度提高三个等级至2 H,纳米压痕硬度提高了17.6%,但热稳定性有所降低,起始分解温度降低了81.6℃。Sn Cl₂对合金表面硬度和热稳定性的影响不大,其通过提高PC和PMMA间的酯交换反应程度,生成PC-PMMA共聚物,有效改善了PC和PMMA间的相容性和合金的透明性能。当其添加量为0.05 wt%时,PC/PMMA合金（质量比为80/20,全文同）只存在一个玻璃化转变温度T_g,PMMA分散相在PC基体中均匀分布。合金在波长600nm处的透光率从PC/PMMA的53.7%提高至72.8%,雾度从52.2%降至43.4%。此外,转矩流变测试和热重分析（TGA）证明,Sn Cl₂对PC存在催化降解作用,当Sn Cl₂的用量为0.05 wt%时,PC/PMMA/Sn Cl₂-0.05的熔体平衡扭矩比PC/PMMA降低了47.2%。随着Sn Cl₂添加量增加,合金的熔体平衡扭矩和DTG曲线中归属于PC组分的最大分解速率温度逐渐降低。在相容性提高和PC降解的双重作用下,添加0.05 wt%的Sn Cl₂前后,合金的力学性能相当。（2）通过较简便的熔融共混,制备了一种在较高SiO₂含量下仍透明的SiO₂/PMMA复合材料,研究了实验室自制的分散剂Si-DPF和SiO₂含量对复合材料表面硬度、韧性、透明和加工性能的影响。高硬度的SiO₂显著提高了复合材料的表面硬度,当其用量为30 wt%时,复合材料的纳米压痕硬度比纯PMMA提高了107.8%,Si-DPF对复合材料表面硬度的影响较小。扫描电镜（SEM）和透射电镜（TEM）表明,Si-DPF显著改善了SiO₂在基体中的分散性,当Si-DPF用量为5 wt%时,SiO₂粒径从数百纳米降至20-40 nm。因此,复合材料的韧性、透明和加工性能得到有效改善。SiO₂含量同为30 wt%时,SiO₂/PMMA/Si-DPF（30/65/5）在波长600 nm处的透光率从SiO₂/PMMA（30/70）的77.3%提高至87.2%,缺口冲击强度较之提高了22.9%,熔体平衡扭矩则降低了17.5%。由于SiO₂团聚体尺寸减小相当于其数量增多,进而使体系两相界面总面积增加,对入射光的散射程度提高,故SiO₂/PMMA/Si-DPF（30/65/5）的雾度,由SiO₂/PMMA（30/70）的17.7%提高至34.3%。这也说明了Si-DPF能提高SiO₂的分散性。（3）使用SiO₂/PMMA代替纯PMMA改性PC,将之与PC熔融共混,并加入酯交换催化剂Sn Cl₂,制备高表面硬度透明的SiO₂-PMMA/PC复合材料。研究不同质量比例对复合材料表面硬度、透明、力学、加工和热性能的影响,并与PC/PMMA合金进行对比。测试结果表明,随着SiO₂/PMMA含量的提高,复合材料的表面硬度逐渐提高,而透明、力学性能和热稳定性则逐渐变差。相较纯PC,SiO₂/PMMA的质量分数为10 wt%时,SiO₂-PMMA/PC（10/90）的铅笔硬度提高了四个等级,纳米压痕硬度提高了21.2%,熔体平衡扭矩则降低了30.6%。与PC/PMMA/Sn Cl₂-0.05相比,SiO₂-PMMA/PC（10/90）的铅笔硬度、纳米压痕硬度和缺口冲击强度分别由2 H、236.8 MPa和4.76 k J/m²提高至3 H、254.1 MPa和5.18 k J/m²,波长600 nm处的透光率、雾度和起始分解温度分别为70.7%、39.1%和368.5℃,与PC/PMMA/Sn Cl₂-0.05的72.8%、43.4%和379.2℃相近,但SiO₂-PMMA/PC（10/90）的熔体平衡扭矩提高了55.3%。更多还原

【Abstract】 Polycarbonate（PC）is widely utilized in mobile communications,medical devices and aerospace due to the advantages of excellent transparency,heat resistance and toughness,while it suffers from the drawbacks of the low surface hardness and wear-resistance.Poly（methyl methacrylate）（PMMA）possesses high surface hardness and excellent transparency.To fabricate PC/PMMA alloys by blending PC with PMMA is expected to solve the problem of low surface hardness of PC on the base of ensuring the transparency.However,the poor compatibility and the different refractive indexes between PC and PMMA will lead to the opaque of the alloy by simply blending.In this work,the catalyst Sn Cl₂ promoting ester exchange reaction was employed to enhance the compatibility between PC and PMMA and PC/PMMA alloys with high surface hardness and excellent transparency were prepared.Furthermore,the inorganic rigid particle with higher hardness（i.e.silicon dioxide,SiO₂）was utilized to blend with PMMA and the dispersing agent Si-DPF was added to improve the dispersion of SiO₂ in the matrix to obtain transparent SiO₂/PMMA composites with higher surface hardness.The PMMA component in PC/PMMA alloy was replaced by SiO₂/PMMA composite to finally prepare SiO₂-PMMA/PC composites with higher surface hardness,excellent transparency,processability,mechanical and thermal properties to broaden the application of PC.（1）The effect of Sn Cl₂ on the compatibility between PC and PMMA and the corresponding mechanism were investigated,and the surface hardness,transparency,processability,mechanical and thermal properties of PC were investigated at the different loading of PMMA and of Sn Cl₂.The results manifested that the surface hardness of PC was significantly improved after blending with 20 wt%PMMA,the pencil hardness was increased by three grades to 2 H,and the nanoindentation hardness was increased by 17.6%,but the thermal stability was reduced and the decomposition temperature at 5%weight loss was decreased by 81.6℃.Sn Cl₂ had little influence on the surface hardness and thermal stability of the PC/PMMA alloys,but it promoted the ester exchange reaction between PC and PMMA and PC-PMMA copolymer was generated,which improved the compatibility and the transparency of the PC/PMMA alloys.When the loading of Sn Cl₂ was 0.05 wt%,only one glass transition temperature（T_g）was observed in the PC/PMMA alloys（mass ratio of 80/20,the same in the full text）,and the dispersed phase（PMMA）was homogeneously distributed in the PC matrix,and the transmittance of the alloy at 600 nm was increased from 53.7%to72.8%,and the haze was decreased from 52.2%to 43.4%,compared with PC/PMMA.In addition,the torque rheological test and thermogravimetric analysis（TGA）demonstrated that Sn Cl₂ catalyzed the degradation of PC.When the amount of Sn Cl₂ was 0.05 wt%,the melt balanced torque of PC/PMMA/Sn Cl₂-0.05 was reduced by 47.2%compared with PC/PMMA.As the amount of Sn Cl₂ increased,the melt balanced torque of the PC/PMMA alloys and the maximum decomposition rate temperature attributed to the PC component were gradually decreased.The mechanical properties of the alloy varied little after the addition of 0.05 wt%Sn Cl₂ owing to the combined effects of improved compatibility and PC degradation.（2）Transparent SiO₂/PMMA composites with high SiO₂ content were fabricated by simple melt blending,and the effects of the laboratory-made dispersing agent Si-DPF and SiO₂ content on the surface hardness,toughness,transparency and processability of the composites were investigated.The SiO₂ with high hardness significantly enhanced the surface hardness of the composites,the nanoindentation hardness of the composites containing 30 wt%SiO₂ was increased by 107.8%compared with that of pure PMMA,while the Si-DPF had little influence on the surface hardness of the composites.The results from scanning electron microscopy（SEM）and transmission electron microscopy（TEM）revealed that Si-DPF significantly improved the dispersion of SiO₂ in the PMMA matrix.When the amount of Si-DPF was 5 wt%,the particle size of SiO₂ agglomerates was reduced from hundreds of nanometers to 20-40 nm.Consequently,the toughness,transparency and processability of the composites were considerably improved.At the same SiO₂ content of 30 wt%,the transmittance at 600 nm of SiO₂/PMMA/Si-DPF（30/65/5）was increased from 77.3%to87.2%,and the notched impact strength was increased by 22.9%compared with SiO₂/PMMA（30/70）,and the melt balanced torque was reduced by 17.5%.Furthermore,compared to sample SiO₂/PMMA（30/70）,the haze of SiO₂/PMMA/Si-DPF（30/65/5）was increased from 17.7%to 34.3%,probably because the number of SiO₂ agglomerates increased as the size decreased,which enlarged the total surface area of the dispersion phase and increased the scattering of incident light.The result also indicated that Si-DPF improved the dispersibility of SiO₂.（3）Transparent SiO₂-PMMA/PC composites with high surface hardness were prepared by replacing pure PMMA with SiO₂/PMMA（30/70 by weight）to modify PC through melt blending and adding eater exchange catalyst Sn Cl₂.The results exhibited that the surface hardness of the composites was gradually enhanced with the increasing of SiO₂/PMMA content,while the transparency,mechanical properties and thermal stability were gradually deteriorated.When the loading of SiO₂/PMMA was 10 wt%,the pencil hardness of SiO₂-PMMA/PC（10/90）was increased by four grades,the nanoindentation hardness was increased by 21.2%and the melt balanced torque was decreased by 30.6%compared to those of pure PC.Compared with PC/PMMA/Sn Cl₂-0.05,the pencil hardness,nanoindentation hardness and notched impact strength of SiO₂-PMMA/PC（10/90）were increased from 2 H,236.8 MPa and 4.76 k J/m² to 3 H,254.1 MPa and 5.18 k J/m²,respectively.The transmittance at 600 nm,haze and initial decomposition temperature of SiO₂-PMMA/PC（10/90）were70.7%,39.1%and 368.5℃,respectively,similar to 72.8%,43.4%and 379.2℃of PC/PMMA/Sn Cl₂-0.05,meanwhile the melt balanced torque of SiO₂-PMMA/PC（10/90）was55.3%higher than that of PC/PMMA/Sn Cl₂-0.05.更多还原