【作者】 孙双月；

【导师】 汪晓东；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2010， 博士

【摘要】 目前,我国工程塑料工业发展与国外先进水平有较大差距,虽然国内企业通过引进成套生产技术,在通用料生产方面其生产规模不断扩大,产品牌号不断增加,已经和国外企业相差无几。但是,在改性产品开发上国内企业远远落后于国外公司,至今没有改性产品上市。国内工程塑料市场基本为国外企业所垄断。本文以国产聚甲醛(POM)、聚酰胺(PA)6以及聚碳酸酯(PC)回收料为基料,选择有代表性的改性专用料体系进行改性技术的研究与开发,将有助于国内企业提高产品的附加值以及我国工程塑料改性技术水平的提升和行业的发展。本文的研究内容主要包括三大部分。第一,无卤阻燃POM复合物的制备及其阻燃机理研究POM的阻燃历来是一个难题,这与其自身特殊的分子结构和燃烧机理有关。本文采用磷系阻燃剂聚磷酸铵(APP)或微胶囊红磷(MRP)与三聚氰胺氰尿酸盐(MC)复配的磷-氮协效阻燃剂；此外,针对POM燃烧过程中难以成炭的特性,利用双季戊四醇(DPER)和热塑性酚醛树脂(novolak)协效成炭作用辅助其成炭；利用热塑性聚氨酯(TPU)作为无机粉体阻燃剂的载体及包覆材料,不仅可提高阻燃剂与基体树脂之间的相容性,还可降低因添加粉体阻燃剂对其力学性能造成的影响。综合上述技术,通过熔融共混法制备了性能优良的无卤阻燃POM复合物。测试了阻燃POM的阻燃性能、力学性能,并采用红外光谱仪(FTIR)分析了阻燃POM燃烧残炭的成分,用扫描电子显微镜(SEM)观测燃烧残炭的形貌,用热失重分析仪(TGA)表征了POM及阻燃POM的热稳定性,用热裂解-气相色谱-质谱联用仪(Py-GC-MS)分析了POM及阻燃POM的热降解机理。结果表明,MRP/MC/DPER/novolak复配阻燃POM的阻燃性可达到UL94V-1级,而APP/MC/DPER/novolak复配阻燃POM的阻燃级别可达UL94V-0级,其LOI最高达到52.8。垂直燃烧测试后样条表面剩余炭层的SEM照片显示,该炭层为外表面致密坚固、内部呈蜂窝状的焦化炭层,可有效阻止热和氧的传递,有助于减缓或终止燃烧。TGA测试结果表明,在阻燃POM燃烧过程中,复配阻燃剂在POM未分解之前就可起到阻燃作用,并促使体系的炭化使残炭量大幅提高。FTIR和Py-GC-MS分析表明,所加阻燃剂在气相和凝聚相同时起到阻燃作用。并且根据测试结果分析了阻燃机理。第二,尼龙6高强超韧化改性研究尼龙6改性研究一直是人们关注的焦点。本文分别采用甲基丙烯酸甲酯-丁二烯-苯乙烯共聚物(MBS)和甲基丙烯酸甲酯-甲基苯基硅氧烷-苯乙烯共聚物(MSiS)对尼龙6进行增韧改性研究,这两种共聚物均为具有“核-壳”结构的增韧剂,并用双酚A型环氧树脂(DGEBA)作为增容剂。这两种体系的SEM及TEM照片显示,增容剂的添加可显著提高MBS(或MSiS)粒子在基体中的分散性,使其形成单分散分布。结果表明,当尼龙6/MBS/DGEBA的质量比为80／20／3,体系的缺口冲击强度达到92kJ／m2,而尼龙6/MSiS/DGEBA(80／20／3)体系的缺口冲击强度达到66kJ／m2,MBS的增韧效果明显好于MSiS的。并且这两种试样冲击断面的SEM照片显示,基体发生了大范围的剪切屈服,为韧性断裂,其增韧机理为粒子的空穴化以及基体的剪切屈服。在增韧效果较好的MBS增韧体系中分别添加有机蒙脱土(OMMT)和针状硅灰石作为增强剂,以提高共混体系的强度和刚性。X-射线衍射仪(XRD)分析表明,OMMT被充分剥离分散在尼龙6基体中。透射电镜(TEM)照片显示,MBS和OMMT各自均匀分散在尼龙6基体中,OMMT的存在不会干扰MBS粒子空穴化以及引起基体的剪切屈服而起到增韧作用。第三,PC回收料的增韧及无卤阻燃改性研究PC是一种综合性能优良的工程塑料,其产量和消费量仅次于尼龙,位列五大通用工程塑料第二位。随着PC消费量的迅速增加,不可避免地产生大量废弃PC制品及废料,它既是宝贵的再生资源,处理不当又会对环境造成无法弥补的危害,所以对PC的回收再利用是节约资源,保护生态环境的有效处理方法。本文分别用具有“核-壳”结构的增韧剂MBS和MSiS粒子来对PC回收料进行改性研究。结果表明,由于MBS或MSiS与PC回收料相容性较差而没有达到增韧效果,当分别添加双酚A型环氧树脂(DGEBA).苯乙烯-马来酸酐共聚物(SMA)或聚双酚A羟基醚(Phenoxy)作为增容剂,其缺口冲击强度得到大幅提高。试样的SEM照片显示,增容剂的添加可使MBS(或MSiS)粒子在基体中形成单分散分布,这是取得优异增韧效果的关键因素。并根据实验结果分析了增韧机理。MSiS粒子不仅能有效提高PC回收料的冲击性能,还能赋予其优异的阻燃性能,当添加7wt.%MSiS和3wt.%的增容剂,可使PC回收料达到UL94 V-0的阻燃级别。垂直燃烧测试后残炭的FTIR分析表明,添加MSiS的PC共混物在燃烧时生成富含Si-C键和Si-O-Si键的隔氧绝热残炭层,起到隔热隔氧的作用。通过上述方法对PC回收料进行改性,为其再利用创造了条件,达到了充分利用回收料、节约资源的目的。更多还原

【Abstract】 At present, there are the huge gaps in development of engineering plastics technologies between domestic and international industries. The production scales of general grade engineering plastics are continuously expanding and product categories of general grade engineering plastics are increasing by introducing the complete sets of technique in the domestic enterprises. However, the domestic enterprises lag far behind many countries in the technologies of engineering plastics modification; there are no modified products in market. The almost all domestic market of engineering plastics is monopolized by the foreign enterprises. To promote the improvement of the modification techniques of engineering plastics and the development of the domestic industries, polyoxymethylene(POM), polyamide 6(PA6), and recycled polycarbonate(PC) were modified for achievement of high performance in this work. The studies contain three parts in this paper.Firstly, Preparation and study on flame-retardant mechanism of halogen-free flame-retarded POM compoundsPOM is considered as the most difficultly flame-retarded thermoplastic polymer because of its special chemical structure as well as its thermal stability and chemical degradation characteristics. In this paper, the flammability characteristics and thermal stability of halogen-free flame-retardant POM were studied, and two very effective flame retarding formulation for POM were developed from a combination of ammonium polyphosphate (APP), melamine cyanurate (MC), novolak, and dipentaerythritol(DPER), and the other combination of microencapsulated red phosphorus(MRP), MC, novolak, and DPER. The decomposition behavior of the POM compounds was evaluated by thermogravimetric analysis(TGA). The compound shows optimal flame retardancy with a limiting oxygen index of 52.8 and flammability rating of UL94 V-0, when 27wt.%APP,9wt.%MC,4 wt.% novolak, and 4wt.% DPER are simultaneously incorporated into POM. The MRP/MC/DPER/novolak flame retarded system achieved UL94 V-1 rating. The presence of novolak and DPER as char-forming agents results in a dense and compact multicellular char residue for the test bar after combustion, while Fourier transform infrared(FTIR) spectra confirm a characteristic phosphorous-and carbon-rich char resulting from the APP/MC formulation. The pyrolysis-gas chromatography-mass spectrometry(Py-GC-MS) analysis indicates that highly flammable formaldehyde gas, the main pyrolysis product of POM, is annihilated by amide derivatives produced by the pyrolysis of MC, imparting better flame retardancy. The comprehensive flame-retardant mechanisms based on phosphorus-nitrogen synergism promote the high flame retardancy of POM to reach the non-flammability of the V-0 rating. Secondly, Study on modification of nylon 6 for enhancement of impact resistance and strengthModification of nylon 6 is the focus all the time.This work is focused on a new route to achieve both high fracture toughness and high strength for nylon 6. A series of nylon 6-matrix composites were prepared via melting extrusion by compounding with poly(methyl methacrylate-co-butadiene-co-styrene) (MBS) latex particles as an impact modifier and diglycidyl ether of bisphenol-A (DGEBA) as a compatibilizer. Layered organic montmorillonite and fibrillar wollastonite were also incorporated into the nylon 6 compounds for the reinforcement of materials. Morphology study suggests that the MBS latex particles could achieve a mono-dispersion in nylon 6 matrix with aid of 3wt.% DGEBA, which improves the compatibilization and an interfacial adhesion between the matrix and the shell of MBS using a melt-extrusion technique. A high impact toughness was also obtained but with a corresponding reduction in tensile strength and stiffness. A moderate amount of the layered organic montmorillonite and fibrillar wollastonite as a nonofiller could gain a desirable balance between tensile strength and toughness of the materials, and the flexural strength, tensile strength, and stiffness achieved an improvement. The thermal stability and thermal resistance were also enhanced. This suggests that the combination of nanofillers and core-shell latex particlesis a useful strategy to optimize and enhance the properties of PA6. The structure and morphology of the nanocomposites studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the layered organic montmorillonite was exfoliated within nylon 6 matrix. It was found that the core-shell latex particles and the nanofillers were dispersed respectively in the nylon 6 matrix. The study indicates that the presence of the nao fillers in the nylon 6 matrix cannot disturb the latex particles to promote high fracture toughness via particle cavitation and subsequent matrix shear yielding, in addition, provided maximum reinforcement to the polymer. Thirdly, Study on modification and mechanism of recycled PC in improvement in impact resistance and flame retardancyPC is one of the most important engineering thermoplastics used in a wide variety of applications; the annually consumed amount of this polymer exceeds several million metrictons. In recent years, the interest in recycling of PC has expanded dramatically and this is a trend that will undoubtedly continue into the future, which may be explained by (i) limited natural resources, (ⅱ) rising waste-handling costs, and (ⅲ)environmental regulations related to land-filling and incineration of plastics. In this paper, two types of core-shell structured latexes, poly(methyl methacrylate-co-butadiene-co-styrene) (MBS) and poly(methyl methacrylate-co-methylphenyl siloxaneco-styrene) (MSiS) were used to modify recycled polycarbonate(PC) for the enhancement of toughness and flame retardancy. The impact strength of the modified PC blends was not improved after melt-blending recycled PC with these two kinds of latexes, probably because the latex particles were not evenly dispersed in the PC matrix because of the incompatibility between PC and PMMA shell of the latexes. Addition of a compatibilizer, e.g. DGEBA, SMA, or Phenoxy can effectively enhance the toughening effect of recycled PC with core-shell structured modifiers. The presence of compatibilizer in the blends reduces the interfacial tension and introduces a steric hindrance to coalescence, and thus enhances the interfacial adhesion between PC domain and PMMA shell, and improves the dispersion of core-shell structured particles in the PC matrix. The ternary blends achieve a high impact resistance by cavitation of the particles, which relieves the triaxial stress and promotes massive shear yielding of the matrix, and then enables the matrix to fracture by the plane stress ductile tearing mode. Additionally, MSiS has a silicone-based core and can effectively retard the combustion of recycled PC. The blends containing 7wt.% MSiS and 3wt.% compatibilizer can achieve a UL94 V-0 rating in vertical burning test. We proposed that, during combustion, a fine dispersion of MSiS particles in the PC matrix facilitates the rapid migration of MSiS and formation of a uniform and highly flame resistant char barrier on the surface of the modified PC.更多还原