Preparation and Characterization of Organic/Inorganic Hybrid Nanofibers

A new class of nanocomposites based on organic and inorganic species integrated at a nanoscale has obtained more attention these years. Organic-inorganic hybrids have both the advantages of organic materials, such as light weight, flexibility and good moldability, and inorganic materials, such as high strength, heat stability and chemical resistance. In this work, PVAc/TiO2 organicinorganic hybrid was prepared by sol-gel process. Eiectrospinning technique was used to fabricate PVAc/TiO2 hybrid nanofibers. The structures and properties of the hybrid nanofibers were characterized by Scanning Electron Microscopy （SEM）, Atomic Force Microscope （AFM）, Differential Scanning Calorimeter （DSC） and Fouriertransform infrared （FTIR） spectra. SEM and AFM were employed to study the topography of the hybrid nanofibers. The chemical structure of the hybrid nanofibers were examined by FTIR. The DSC scans revealed the second order transition temperature of the hybrid materials were higher than PVAc.     

Effect of Nanoclay on the Phase Separation Behavior of Poly（methyl methacrylate）/Poly（vinyl acetate） Binary Polymer Blends

The effect of nanoclay on the phase-separation behavior of poly（methyl methacrylate）/poly（vinyl acetate）（PMMA/PVAc） blends has been mainly investigated by small-angle laser light scattering. It is found that the effect of clay on the thermodynamics and kinetics of phase-separation for PMMA/PVAc blends seems inconsistent. The kinetics phaseseparation rate decreases, while the thermodynamics parameters, cloud points Tc and delay time tD of isothermal phaseseparation also decrease, and the variation amplitude depends on the matrix composition. The affinity of clay to PMMA results in the composition difference between the border layer and the polymer matrix and further causes the concentration fluctuation at the early stage of phase separation to reduce Tc and tD. On the other hand, the decrease of phase-separation rate is caused by the mechanical barrier effect of clay on the macromolecular diffusion of blend matrix. Hence, such seemingly counterintuitive results on the thermodynamics and kinetics of phase-separation are attributed to different dominant factors.     

The thermal degradation of poly(vinyl acetate) and poly(ethylene-co-vinyl acetate), Part I: Experimental study of the degradation mechanism

The thermal degradation mechanism of poly(vinyl acetate) (PVAc) and poly(ethylene-co-vinyl acetate) (EVA) copolymers was investigated with solid-state NMR, thermogravimetry coupled with mass spectrometry and differential thermal analysis. Between 300 and 400 °C acetic acid is eliminated (deacetylation), leaving a highly unsaturated residue or polyene. The deacetylation of PVAc is autocatalytic. Upon incorporation of ethylene entities into the polymer backbone, autocatalysis disappears. Between 400 and 500 °C, the polyene will degrade further by chain scission reactions in inert conditions or aromatise in an oxidative environment into a char, and oxidised eventually into CO₂ beyond 500 °C.In inert conditions, the deacetylation step as well as the chain scission reaction shows endothermic effects. In an oxidative environment, large exothermal effects are found for each degradation step. This indicates the occurrence of additional oxidation reactions during deacetylation, an important reorganisation of the polyene during char formation and oxidation of the latter into CO₂.     

生物醋酸乙烯制备高聚合度聚乙烯醇

为了制备聚合度大于3000的高聚合度聚乙烯醇,以生物醋酸乙烯为原料、偶氮二异丁腈为引发剂、甲醇为溶剂进行溶液聚合反应研究,考察了温度、搅拌转速、引发剂用量、甲醇用量和聚合时间对生物醋酸乙烯聚合反应的影响,采用正交试验法对生物醋酸乙烯溶液聚合的反应条件进行了筛选,并通过凝胶色谱对最优条件下制得的聚醋酸乙烯进行了分子量的测定。结果表明,最优的聚合反应条件为：聚合温度65℃,搅拌转速200 r/min,聚合时间2 h,甲醇用量10％,引发剂用量0.005％,所得的产品聚合度为3640;极差分析确定了影响聚醋酸乙烯聚合度的主次顺序为：甲醇用量、引发剂用量和聚合时间;由凝胶色谱分析可知,在最优条件下可以制备得到的聚醋酸乙烯分子量分布为1.2。说明以生物醋酸乙烯为原料进行溶液聚合可以得到高聚合度、分子量分布较窄的产品。     

聚醋酸乙烯水泥复合乳胶漆

聚醋酸乙烯水泥复合乳胶漆是将聚醋酸乙烯乳液与普通硅酸盐白水泥相混合,并用１０７胶和膨润土改性,形成聚醋酸乙烯水泥单罐装复合材料。在实验的基础上,给出了涂料配合比的选择、配方、配制工艺,并对水泥漆的成膜机理进行了初步探讨。最后对沉淀分层、变稠、胀性现象、助剂作用等问题进行了讨论。这种水泥复合乳胶漆无毒无味,耐擦洗性和粘结强度优良,生产工艺简单,贮存性好,施工方便,有较广的应用领域。     

FT‐IR Investigation into the miscible interactions in new materials for optical devices

In this article we determine the miscibility of azobenzene derivative (poly(4‐(N‐(2‐methacryloyloxyethyl)‐N‐ethylamino)‐4′‐nitroazobenzene)₉₀‐co‐(methyl methacrylate)₁₀)/poly(vinyl acetate) (PVAc) and azobenzene derivative/poly(vinyl chloride) (PVC) blends using Fourier Transform infrared (FT‐IR) spectroscopy. With this method we can clearly identify the exact interactions responsible for miscibility. In the azobenzene derivative 50:50PVAc blend new peaks were evident at 2960, 2890, 1237 and 959 cm^?1, these peaks depict miscible interactions. These wavenumbers indicate that the miscible interactions occurring are from the C? H stretching band, the vinyl acetate C?O, conjugated to the ester carbonyl, the cis‐transformation N?N stretch frequency and the acetate ester weak doublet. The azobenzene derivative 80:20PVC blend display peaks identical in profile to the blend homopolymers, indicating no miscible interactions. However, this could be due to overlapping of peaks within the same wavenumber region, making resolution difficult. This research demonstrates FT‐IR can deduce favorable interactions for miscibility and therefore numerous miscible blends can successfully be calculated if possessing the same groups responsible for miscibility. This paves the way for a new generation of designer optical materials with the desired properties. Copyright © 2003 John Wiley & Sons, Ltd.     

饥饿态半连续VAc/BA核壳乳液聚合乳胶粒形态的演化模拟

将乳胶粒的簇迁移理论用到新簇在种子外表面生成核壳型乳胶粒形态演化的情况,以聚醋酸乙烯酯(PVAc)／聚丙烯酸丁酯(PBA)体系的相关实验结果为例,进行了模拟计算,所得结果与实验结果相符。本文的方法适用于种子乳液聚合中第二阶段全饥饿态加料的过程。     

Thermal and photochemical stability of poly(methyl methacrylate) and its blends with poly(vinyl acetate)

An investigation of the thermal stability of poly(methyl methacrylate) (PMMA) blends with poly(vinyl acetate) (PVAc) revealed that PVAc acts as a stabilizer as concerns thermal and photochemical degradation when the processes take place in air. The temperatures of decomposition of these blends are higher than that of pure PMMA. The efficiency of photodegradation and photooxidation in the blends is lower than that of pure PMMA.     

硬石膏粉体为填料制备白色及彩色涂料初探

研究了200M、1250M及1250M煅烧硬石膏粉体替代TiO2-CaCO3-滑石粉等无机填料制备聚醋酸乙烯酯白色及彩色涂料的涂料性能. 通过系列测试发现:1250M煅烧硬石膏粉体为填料的白色及彩色涂料性能较好,在彩色涂料中比TiO2-CaCO3-滑石粉及其他硬石膏粉体具有更强的保色能力,有望在白色及彩色涂料中得到应用.