Water‐uptake kinetics in poly(methyl methacrylate) films with a fluorescent rotor probe

A fluorescence method was adapted to measure moisture‐uptake kinetics in films of poly(methyl methacrylate), and data were interpreted in the context of a Fickian diffusion model. The films, 2–60 μm thick, were supported on acid‐etched microscope slides. They were compared with several freestanding slabs about 1 mm thick. The moisture diffusion in the slabs was Fickian with a diffusivity of 3.2 × 10^?9 cm²/s. The apparent Fickian diffusivity in the films decreased substantially with decreasing film thickness; however, a careful examination revealed that the initial moisture uptake was governed by a thickness‐independent diffusivity for a wide range of film thicknesses. This suggested that the appearance of non‐Fickian behavior originated within about a micrometer of the buried interface, possibly as a result of water accumulation beneath the film or slight thickness variations. Moisture uptake in the thickest films was more rapid than in the slabs, most likely because of residual thermal stresses. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2463–2471, 2002     

The Microstructure of Solvent-Welding of PMMA

The microstructure of solvent-welding of PMMA has been investigated. The morphologies of shear, tensile, tear and cleavage fracture surfaces are observed. Effects of solubility parameter, elevated temperature, and cosolvent on the mechanical strength are studied. The solvents used are methanol, ethanol and DMF. The feature sizes of shear, tensile and tear fracture surfaces and the angle of the cleavage curve at the interface of PMMA can be employed to determine the mechanical strength qualitatively. Constituents of shear, tensile and tear fracture surfaces are tongues, long and narrow hackles, and equiaxed hackles, respectively. PMMA treated at high temperature showed enhanced mechanical strength. PMMA treated with 95% by volume ethanol yielded the best quality of adhesion. The solvent affected zone and the residual solvent are also discussed.     

聚甲基丙烯酸甲酯／镉黄颜料色母粒的合成及其研究

采用亚硫酸氢钠、过氧化二苯甲酰作引发剂,在无机镉黄颜料水悬浮液中,引发甲基丙烯酸甲酯进行聚合反应,得到了镉黄颜料色母粒。对该种色母粒作了红外光谱及DTA、TG分析,并探讨了其反应机理。     

Use of a new natural clay to produce poly(methyl methacrylate)‐based nanocomposites

Nanocomposites of poly(methyl methacrylate) (PMMA) filled with 3 wt% of modified natural Algerian clay (AC; montmorillonite type) were prepared by either in situ polymerization of methyl methacrylate initiated by 2,2′‐azobisisobutyronitrile or a melt‐mixing process with preformed PMMA via twin‐screw extrusion. The organo‐modification of the AC montmorillonite was achieved by ion exchange of Na⁺ with octadecyldimethylhydroxyethylammonium bromide. Up to now, this AC montmorillonite has found applications only in the petroleum industry as a rheological additive for drilling muds and in water purification processes; its use as reinforcement in polymer matrices has not been reported yet. The modified clay was characterized using X‐ray diffraction (XRD), which showed an important shift of the interlayer spacing after organo‐modification. The degree of dispersion of the clay in the polymer matrix and the resulting morphology of nanocomposites were evaluated using XRD and transmission electron microscopy. The resulting intercalated PMMA nanocomposites were analysed using thermogravimetric analysis and differential scanning calorimetry. The glass transition temperature of the nanocomposites was not significantly influenced by the presence of the modified clay while the thermal stability was considerably improved compared to unfilled PMMA. This Algerian natural montmorillonite can serve as reinforcing nanofiller for polymer matrices and is of real interest for the fabrication of nanocomposite materials with improved properties. Copyright © 2009 Society of Chemical Industry     

High transmittance and environment‐friendly flame‐resistant optical resins based on poly(methyl methacrylate) and cyclotriphosphazene derivatives

Highly transparent optical resins based on poly(methyl methacrylate) (PMMA) and two cyclotriphosphazene derivatives which acting as halogen‐free flame retardants were prepared. The refractive indices, visible light transmittance, water absorption, flame‐resistant characteristic, and the mechanical properties of the resins were studied. Comparing with pure PMMA, the as‐prepared resins with the two additives exhibited higher refractive index (n_d), longer UV cutoff wavelength and better surface hardness. The water absorption of the resins was decrease with increasing of the additives. The visible light transmittance of all the samples adding Additive A was higher than 90%. When the weight ratio of additive/MMA was 20/100, the limiting oxygen index (LOI) of the samples were 26 (with Additive A) and 22 (with Additive B), respectively. The surface hardness was increased from HB to 2H with increasing the content of the additives, and the impact and the tensile strength changed little for the formulas of the additives lower than 30% by weight. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and properties of transparent PMMA/ZrO2 nanocomposites using 2-hydroxyethyl methacrylate as a coupling agent

Transparent PMMA/ZrO₂ nanocomposites were prepared by in-situ bulk polymerization of methyl methacrylate (MMA)/ZrO₂ dispersions that were firstly synthesized using nonaqueous synthesized ZrO₂ nanocrystals and the function monomer, 2-hydroxyethyl methacrylate (HEMA), as the ligand. The dispersion behavior of ZrO₂ nanoparticles in MMA, structure, mechanical and thermal properties of the PMMA/ZrO₂ nanocomposites were investigated comprehensively. It was found that ZrO₂ nanoparticles were well dispersed in MMA with HEMA ligand, but the MMA/ZrO₂ dispersions easily destabilized in air as well as at elevated temperatures. The destabilization temperature of the dispersion is raised by increasing the molar ratio of HEMA/ZrO₂ to match the bulk polymerization temperature. The PMMA/ZrO₂ nanocomposites showed an interesting chemical structure (namely, highly cross-linked structure even at ZrO₂ content as low as 0.8 wt% and hydrogen bonding interaction between polymer matrix and ZrO₂ nanoparticles), with enhanced rigidity without loss of the toughness and improved thermal stability. The relationship between the structure and the properties of the PMMA/ZrO₂ nanocomposites based on the HEMA coupling agent was discussed.     

偏振激光诱导的薄膜表面周期性自组织结构

本文研究了激光诱导的周期性表面结构(LIPSS)在聚甲基丙烯酸甲酯(PMMA)薄膜表面的形成过程。在导电玻璃衬底上制备得到PMMA薄膜,经p偏振的XeCl准分子激光照射后形成周期性的褶皱结构。用原子力显微镜(AFM)观察发现,形成的褶皱结构周期具有纳米量级,且当引入外加电场时,褶皱形成所需的激光脉冲数减少到2。当外加电压增加到30V时,褶皱的周期间隔明显减小,LIPSS变得不可控,出现了柱状的自组织结构。与直接用准分子激光照射的薄膜样品相比,外加辅助电压的引入改变了PMMA样品表面褶皱结构形成的时间和周期大小,褶皱形成的内部驱动力也发生了变化。     

聚甲基丙烯酸甲酯/ABS共混体系力学性能研究

采用双螺杆熔融共混工艺路线，通过选用合适牌号的聚甲基丙烯酸甲酯及ABS为基本原料，通过控制合适共混工艺条件，制备了一系列不同配比的聚甲基丙烯酸甲酯／ABS塑料合金材料。采用电子万能试验机、悬臂梁冲击实验机等测试手段对合金的力学性能进行了研究，结果表明：聚甲基丙烯酸甲酯／ABS合金材料的拉伸强度随聚甲基丙烯酸甲酯含量的增加而增大，断裂伸长率随着聚甲基丙烯酸甲酯含量的增加而减小，缺口冲击强度随聚甲基丙烯酸甲酯含量的增加而减小。     

Orthogonal ligation to spherical polymeric microparticles: Modular approaches for surface tailoring

Modular ligation strategies for the functionalization of polymeric microspheres provide new perspectives for their applications in material science. In the current trend article we highlight variable synthetic procedures for generating functional microspheres via orthogonal modular conjugation chemistries. An overview of the different surface chemistries available is provided, followed by surface-sensitive characterization techniques relevant for the microparticles. Finally, we explore future trends in modular orthogonal modification approaches on microparticles and provide an outlook on the perspectives that the field of surface-modification of polymeric microparticles holds.     

Interpolymer radical coupling: A toolbox complementary to controlled radical polymerization

The current review focuses on the relevance and practical benefit of interpolymer radical coupling methods. The latter are developing rapidly and constitute a perfectly complementary macromolecular engineering toolbox to the controlled radical polymerization techniques (CRP). Indeed, all structures formed by CRP are likely to be prone to radical coupling reactions, which multiply the available synthetic possibilities. Basically, the coupling systems can be divided in two main categories. The first one, including the atom transfer radical coupling (ATRC), silane radical atom abstraction (SRAA) and cobalt-mediated radical coupling (CMRC), relies on the recombination of macroradicals produced from a dormant species. The second one, including atom transfer nitroxide radical coupling (ATNRC), single electron transfer nitroxide radical coupling (SETNRC), enhanced spin capturing polymerization (ESCP) and nitrone/nitroso mediated radical coupling (NMRC), makes use of a radical scavenger in order to promote the conjugation of the polymer chains. More than a compilation of macromolecular engineering achievements, the present review additionally aims to emphasize the particularities, synthetic potential and present limitations of each system.