【作者】 张才亮；

【导师】 冯连芳； 胡国华；

【作者基本信息】 浙江大学 ， 化学工程， 2009， 博士

【摘要】 聚合物相容共混是不相容聚合物共混过程中加入或原位生成嵌段或接枝共聚物实现相容的技术,已成为制备高性能高分子材料的重要方法。相容剂的相容有效性取决于它们的分子结构、分子量、组成以及与共混物的每一组分之间的相互作用力等。现在盛行的原位相容技术主要是在共混过程中通过界面偶合反应生成接枝共聚物而起相容作用的,但至今什么组成和结构的接枝共聚物具有高效的相容性仍不明确,急需研究。论文创造性地采用结构可控的聚苯乙烯(PS)和尼龙6(PA6)的接枝共聚物(PS-g-PA6)作为PS/PA6共混体系的相容剂,建立了接枝共聚物的链结构和组成与其相容特性的定量关联,这对于指导具有高效相容特性的接枝共聚物的组成和结构优化有重要的意义。论文主要包括三部分内容:(1)提出新的反应加工技术制备结构可控的PS-g-PA6;(2)研究PS-g-PA6作为PS/PA6共混体系的相容剂的相容特性以及热历史下稳定共混物相形态的特性;(3)提出示踪相容剂的概念,将传统的化学工程概念(停留时间分布)引入到高分子材料加工领域,研究双螺杆挤出加工过程中共混物的相形态的动态演变规律。论文取得了以下创新性研究结果:1、在催化剂己内酰胺(NaCL)存在下,3-异丙烯基-α,α-二甲基苄基异氰酸酯(TMI)和苯乙烯(St)的共聚物(PS-co-TMI)中异氰酸官能团引发己内酰胺(CL)聚合,形成接枝共聚物PS-g-PA6。接枝共聚物的结构主要由以下三因素所决定:主链链长、接枝链长和接枝密度。CL接枝到PS-co-TMI主链上的过程中,PS-co-TMI没有发生链降解,因此PS-g-PA6的主链链长可由PS-co-TMI的分子量决定;所有的异氰酸官能团都参与了引发CL的聚合,从而接枝密度可由PS-co-TMI中TMI的含量决定;接枝链长可通过PS-co-TMI/CL的摩尔比来控制。2、接枝共聚物PS-g-PA6作为PS/PA6共混体系的相容剂的相容效率通过分散相/母体形态中分散相尺寸以及在静态热处理下共连续相形态的稳定来衡量。结果表明接枝共聚物的结构和组成对它的相容特性有较大的影响:对于具有相同主链链长和接枝密度的接枝共聚物,接枝链越长,相容效率越高;对于具有相同组成的接枝共聚物,接枝密度越低而接枝链越长,相容效率越高。3、在短时间混合内,加料方式对分散相尺寸有较大的影响,但随着混合时间的延长,这种影响减小甚至可以忽略。这表明加料方式主要影响接枝共聚物Ps-g-PA6到达和稳定界面所需的时间。有效的加料方式应遵循两个原则:第一,为了避免分散相和母体的相反转,母体应在分散相之前熔融;第二,相容剂应在分散相开始熔融前加入。4、对于工业级的聚合物混合过程,很难建立乳化曲线来评估相容剂的相容能力。论文创新性的提出示踪相容剂的概念来解决这一问题。首先将少量的荧光性官能团(如蒽基)反应到Ps-co-TMI上,然后利用Ps-co-TMI中未反应的异氰酸官能团引发CL聚合,形成含有荧光性官能团的接枝共聚物,即示踪相容剂。连续混合装置(如双螺杆挤出机)中的乳化曲线能通过示踪相容剂的浓度分布(即停留时间分布)和相应的共混物的分散相尺寸分布的结合来实现。乳化曲线不仅能够反映相容剂的相容特性,更重要的是能够反映聚合物的混合状况,这无疑将开创聚合物共混的新的研究领域。更多还原

【Abstract】 Polymer compatibilizing blending,block or graft copolymers pre-made are added or generated in-situ by reaction in the mixing process of the immsible polymers, offers an important route to prepare new materials with combinations of properties. The efficiencies of compatibilizer are believed to depend on their molecular architecture,molecular weight,composition and the interaction between the homopolymers and the copolymer block.Now the prevailing method of in-situ compatibilization results mainly from the formation of graft copolymer by the coupling reaction between two functional polymers.Therefore,it is very necessary to research the relationship of the structure and composition of graft copolymer and its compatibilizing efficiency.This thesis use the graft copolymer(PS-g-PA6) with polystyrene(PS) as backbone and polyamide 6(PA6) as grafts as the compatibilizer of PS/PA6 blend systems to establish the relationship of the structure and composition of graft copolymer and its compatibilizing efficiency,which is awfully significant to optimize the structure and composition of graft copolymer in order to achieve the high compatibilizing efficiency.This thesis is composed of three parts:(1) development of a novel reactive processing technology for synthesizing graft copolymer PS-g-PA6;(2) studying emulsification efficiency of PS-g-PA6 graft copolymers for PS/PA6 blends and the ability of stabilizing the phase morphology of PS/PA6 blend in the process of annealing;and(3) bringing forward the concept of tracer-emulsifier and extending an old concept(residence time distribution) in chemical engineering to polymer blending in order to study the morphology evolvement of polymer blends in continuous mixer. The results are as follows:1.The underlying chemistry for the synthesis of PS-g-PA6 graft copolymers was based on the use of a copolymer of styrene(St) and 3-isopropenyl-α,α-dimethylbenzene isocyanate(TMI),PS-co-TMI,to activate the polymerization ofε-caprolactam(CL) in the presence of sodiumε-caprolactam(NaCL) as an anionic catalyst.The structure of a graft copolymer is mainly determined by the following three parameters,backbone length,graft density,and graft chain length.The backbone length of the PS-g-PA6 depended only on the molar mass of the initial PS-co-TMI as the latter was not subjected to chain scission during the synthesis process.The PA6 graft density was determined by the TMI content in PS-co-TMI because all the isocyanate moieties had participated in the activation of the polymerization of CL. The PA6 graft chain length was controlled primarly by the PS-co-TMI/CL molar ratio.2.The efficiency of graft copolymers at compatibilizing the dispersed phase/matrix morphology of PS and PA6 blends and stabilizing the co-continuous morphology of the blends during quiescent annealing were studied.Results showed that it depended very much on its molecular architecture and/or composition.For graft copolymers with similar backbone and graft density,the longer the grafts,the higher their efficiency;for a given backbone/graft composition,graft copolymers having fewer and longer grafts were more efficient at comaptibilizing and stabilizing the morphology.3.Feeding mode had a very significant effect on the size of the dispersed phase domains at short mixing time and its effect decreased or became negligible at long mixing time.This indicates that feeding mode affected mostly the time necessary for the PS-g-PA6 compatibilizer to reach and emulsify the interfaces between PS and PA6. A good feeding mode should meet the following two requirements:first,the matrix should melt faster than the dispersed phase in order to avoid the phase inversion; second,the compatibilizer should be present as soon as the blending process starts, namely,the dispersed phase begins to melt.4.Building up an emulsification curve may not always be practical because of limited amounts of copolymers available.This is especially true for an industrial polymer blending process.A so-called concept of tracer-emulsifier was developed to solve the problem.Very small amounts of fluorecent moities such as anthracene were incorporated in PS-co-TMI.When the latter was used to activate the polymerization of CL,the resulting graft copolymer contained fluorescent moities.An original method for constructing the emulsification curve of a polymer blend in a continuous mixer such as a twin-screw extruder was developed based on the tracer-emulsifier concentration distribution(i.e.the residence time distribution) and the corresponding dispersed phase domain size distribution of the blend system.The resulting emulsification curves exhibited unique features that would open a new research field for polymer blending.更多还原