The glass transition,crystallization, and melting characteristics of a class of polyester ionomers

The glass transition temperature (T_g), crystallization, and melting character of a class of random polyester ionomers (polymer containing < 10 mol % ionic groups) were investigated. The nonlinear change of the T_g and crystallization and melting behavior were characterized using differential scanning colorimetry (DSC). The ionomers are derived from polyethylene terephathalate (PET) modified through copolycondensation with a fully neutralized sulfonate moiety (sodiosulfo) isophthalate (Na‐SIP). Significant and systematic changes in the glass transition temperature and thermal characteristics upon addition of Na‐SIP on the PET backbone were observed, indicating strong association and interaction on the ionic species. At Na‐SIP levels ≥ 4 mol %, the turn of the the glass transition temperature was found, and the same results were obtained for the samples treated either by quenching or dissolution, suggesting the presence of reversible crosslink and aggregation of the ionic species within the organic matrix. When crystallized from the healing or cooling the samples during the DSC nonisothermal crystallization run at a 10°C/min, the enthalpy of the cold crystallization and melting showed an obvious decrease with the increase of Na‐SIP content, and changes of the crystal temperature had an analogy to those of the T_g. A tune of the crystal temperature was found at Na‐SIP levels ≥ 3 mol % (see Figs. 4 , 5 , and 7 ). The experimental data were discussed in the context of the restricted mobility model of the aggregation in the ionomers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3660–3666, 2002     

Solution behavior of Na sulfonated polystyrene: Dipole moment determinations

Solution behavior of Na sulfonated polystyrene (NaSPS) ionomers with different percentages of sulfonate was studied by viscosity and dipole moment measurements. Two solvents of different character were chosen, i.e. dioxane (? = 2.22) and dimethyl formamide (DMF, ? = 36) and their mixtures. The reduced viscosity as a function of concentration in polar solvents reflects the ‘polyelectrolyte’ behaviour of the ionomers. Mean-squared dipole moment (<μ²>/x) values were calculated over a temperature range of 20–100°C, in dioxane and in a mixture of 4% DMF in dioxane. The results confirm the ‘polyelectrolyte’ behavior of ionomers by the addition of a small amount of polar cosolvent. The effect of increasing temperature on <μ²>/x in the DMF-dioxane mixture is attributed to the formation of a coordination complex.     

How the infrared radiation affects the film formation process from latexes?

In this study, the effect of the infrared radiative heating (IRH) was investigated on the film formation from composites of polystyrene (PS) latex particles and poly vinyl alcohol (PVA). The films were prepared as a pure PS and a mixture of PS and PVA particles at equal compositions at room temperature and they were annealed at elevated temperatures above the glass transition temperature (T_g) of PS for 10 min by using IRH technique. Identical experiments were performed by using standard convectional heating technique in oven as comparison. It was shown that the activation energy for the film formation from PS latex particles decreased considerably in IRH annealing technique. Photon transmission (PT) and steady state fluorescence (SSF) techniques were used to monitor the film formation process at each sintering step. Minimum film formation temperature, T_o, and healing temperature, T_h, were determined by the data obtained from the SSF and the PT measurements for each heating processes. The film formation was modeled as a void closure and as an interdiffusion stage below and above T_h, respectively. Scanning electron microscopy (SEM) was used to examine the variation in morphological structure of annealed composite films. It was observed that IRH heating causes more homogenous and more flat film surface than films annealed in the oven. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43289.     

MPS-SiO_2/PS核壳型复合粒子的形态与玻璃化转变温度研究

以正硅酸乙酯为原料,调节pH值为碱性,通过溶胶-凝胶工艺制备单分散SiO2球,用偶联剂甲基丙烯酰(3-三甲氧基硅烷)丙酯(MPS)进行改性,得到MPS-SiO2球形粒子。以MPS-SiO2球为种子,苯乙烯为壳单体,乳液聚合法制备核壳结构的MPS-SiO2/PS复合粒子。透射电镜观察复合粒子形态的结果表明,MPS-SiO2球粒径为200 nm左右时,得到覆盆子状核壳结构;MPS-SiO2球粒径为80 nm左右时,得到包含多个MPS-SiO2球的多核壳结构。差示扫描量热法考察MPS-SiO2/PS复合粒子玻璃化转变温度(Tg)的结果表明,随着MPS-SiO2球含量增加,复合粒子的Tg增加;随着MPS-SiO2球粒径减小,复合粒子的Tg也有所增加。     

MPS-SiO2/PS核壳型复合粒子的形态与玻璃化转变温度研究

以正硅酸乙酯为原料，调节pH值为碱性，通过溶胶-凝胶工艺制备单分散SiO2球，用偶联剂甲基丙烯酰（3-三甲氧基硅烷）丙酯（MPS）进行改性，得到MPS-SiO2球形粒子。以MPS—SiO2球为种子，苯乙烯为壳单体，乳液聚合法制备核壳结构的MPS-SiO2／PS复合粒子。透射电镜观察复合粒子形态的结果表明，MPS—SiO2球粒径为200nm左右时，得到覆盆子状核壳结构；MPS-SiO2球粒径为80nm左右时，得到包含多个MPS—SiO2球的多核壳结构。差示扫描量热法考察MPS-SiO2／PS复合粒子玻璃化转变温度（Tg）的结果表明，随着MPS—SiO2球含量增加，复合粒子的Tg增加；随着MPS-SiO2球粒径减小，复合粒子的Tg也有所增加。     

等离子喷涂氧化钛纳米涂层及其离子注入特性研究

采用等离子喷涂方法制备了ＴｉＯ２ 纳米涂层,研究了其离子注入和抽出特性． 结果表明：等离子喷涂的氧化钛涂层具有多孔性纳米结构,纳米颗粒的尺寸为１０ ～１５０ ｎｍ ,主要由锐钛矿和金红石两种物相构成． 在电位扫描范围为１．０～１．５ Ｖ,电位扫描速率为２０,５０ 和１００ ｍＶ／ｓ 时,涂层表现出良好的Ｌｉ＋ 离子注入和抽出特性． 循环伏安试验表明氧化钛纳米涂层具有良好的电化学稳定性．     

Glass‐transition temperature–conversion relationship for an epoxy–hexahydro‐4‐methylphthalic anhydride system

The DGEBA–MHHPA epoxy system has found increasing applications in microelectronics packaging, making crucial the ability to understand and model the cure kinetics mechanism accurately. The present article reports on work done to elucidate an appropriate model, modified from the empirical DiBenedetto's equation, to relate the glass‐transition temperature (T_g) to the degree of conversion for a DGEBA–MHHPA epoxy system. This model employs the ratio of segmental mobility for crosslinked and uncrosslinked polymers, λ, to fit the model curve to the data obtained. A higher ratio value was shown to indicate a more consistent rate of increase of T_g in relation to the degree of conversion, while a lower value indicated that the rate of T_g increase was disproportionately higher at higher degrees of conversion. The best fit value of λ determined by regression analysis for the DGEBA–MHHPA epoxy system was 0.64, which appeared to be higher than for those previously obtained for other epoxy systems, which ranged from 0.43–0.58. The highest T_g value obtained experimentally, T_{g max}, was 146°C, which is significantly below the derived theoretical maximum T_g∞ value of 170. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 511–516, 2000