Preparation of raspberry‐like poly(methyl methacrylate) particles by seeded dispersion polymerization

The facile preparation of nonspherical raspberry‐like poly(methyl methacrylate) (PMMA) particles by seeded dispersion polymerization of methyl methacrylate (MMA) on micron‐sized PMMA seed particles was described. Various polymerization parameters influencing the particle morphology, as well as the polymerization kinetic and morphological stability, were investigated in detail. It was found that the following polymerization conditions were necessary to prepare this kind of nonspherical particles: a relatively low temperature, an appropriate ratio of seed/MMA, an initiator with a relatively low decomposition rate, and a relatively low initiator concentration. These particles showed very good morphological stability at room temperature, but they changed to the spherical ones when heat treated at 60°C in methanol solution of MMA. The experimental results suggest that the prepared PMMA particles were kinetically favored and the localized polymerization of the MMA monomer on PMMA seed particle surface was responsible for the formation of the raspberry‐like particles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

The failure behavior of a polyurethane composite coating in 3.5% NaCl solution under ultraviolet irradiation

The failure process of inorganic zinc‐rich/micaceous iron oxide epoxy/aliphatic polyurethane composite coating in 3.5% NaCl solution under ultraviolet irradiation (UV) was studied with electrochemical impedance spectroscopy (EIS) and Fourier transform infrared (FTIR) spectroscopy. UV irradiation significantly accelerated failure process of the composite coating in NaCl solution. The effect of UV on failure process of the coating system in 3.5% NaCl solution may be divided into two stages: in the early stage, the thermal effect generated by the ultraviolet irradiation is the main reason leading to the increase in coating porosity, but this effect is not serious and the coating remains high impedance and good protection ability. In the latter stage, the fracture of polymer chains in the top coating by UV irradiation is the main factor resulting in quick decrease of coating performance. C N and C O bonds in polyurethane coating are broken by UV irradiation, leading to quick increase of the coating porosity and decrease of the coating resistance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Surface,tribological, and mechanical characterization of synthetic skins for tribological applications in cosmetic science

Synthetic skin as an ideal human‐tissue substitute is needed for the research and assessment of hair‐ and skin‐care products. In this study, a systematic study was carried out of the surface, tribological, and mechanical properties of two synthetic skins and rat skin with and without skin‐cream treatment with scanning electron microscopy, atomic force microscopy, and a nanoindenter. The film thickness, adhesive force, coefficient of friction, surface roughness, and contact angle of the two synthetic skins and rat skin were comparable. The hardness of one synthetic skin was more similar to rat skin. After treatment with skin cream, the trends of the properties of the two synthetic skins and rat skin were similar. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The formation of β‐polypropylene crystals in a compatibilized blend of isotactic polypropylene and polyamide‐6

Compatibilized polypropylene (PP)/polyamide (PA6) blends with and without β nucleating agent (β‐NA) are prepared, and are designated as Blend‐0.3 and Blend‐0, respectively. The melting and crystallization characteristic of the blends crystallized under different cooling rates and different crystallization temperatures are studied. It is observed that high β‐PP content can be developed in Blend‐0.3 only at slow cooling rates (<5°C/min), whereas high α‐PP content is formed at fast cooling rates. Isothermal crystallization analysis of Blend‐0 indicates that PA6 is an effective NA for α‐PP in the lower temperature range, whereas the α‐nucleating effect disappears in the higher temperature range. Blend‐0.3 can, therefore, be viewed as a system containing both α‐ and β‐NAs, simultaneously. PA6 is competing with β‐NA in inducing PP crystallization. Under the normal injection of Blend‐0.3, the melt will be cooled through the higher temperature that favors the effectiveness of β‐NA rapidly because of the faster cooling rate. However, the α‐nucleation effect from PA6 predominate at the lower temperature. This explains the difficulty in obtaining high β‐PP content in Blend‐0.3 from injection molding. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Comparative study of photoelectric properties of regiosymmetrical poly(3,4-dialkoxythiophene)s

A series of regiosymmetrical poly(3,4-dialkoxythiophene)s: poly(3,4-diamyloxythiophene), poly(3,4-dioctyloxythiophene), poly(3,4-di(2-ethyl-1-hexyloxy)thiophene), and poly(3,4-didodecyloxythiophene) were synthesized by the FeCl₃-oxidative approach. All these polymers were evaluated with NMR, FT-IR, gel permeation chromatography (GPC), thermo-gravimetric analysis (TGA), UV–Vis spectroscopy, and photoluminescence (PL). The polymers have excellent solubility in common organic solvents, and TGA studies show that the polymers lost 5% of their weights on heating to 250 °C above. Investigations of the UV–Vis spectroscopy show that the absorption maxima of the polymer thin films are similar to those in solutions, and the optical band gaps of the polymer thin films are ranging from 2.27 to 2.69 eV. In PL spectra, maxima emission peaks of the polymer thin films lie at 527 to 589 nm, embodying colors from green to yellow, and the quantum yields of the polymers are in the range of 22–28%. All the data indicate that the polymers have good solubility, outstanding thermal stabilities, low band gaps, and high PL quantum yields, and they might be excellent polymeric materials for applications in organic light-emitting diodes (OLEDs), light-emitting electrochemical cells, polymer solar cells, and so on.     

纳米Cu-TiO2在亲水涂料中的耐老化和抗菌性能研究

通过光催化还原的方法制备了纳米铜基二氧化钛(Cu-TiO2)抗菌剂。使用浸涂方法将素铝箔基片涂敷上含1.4%抗菌剂的面漆抗菌涂层。对抗菌涂层进行加速老化处理,采用接触角仪、金相显微镜、体视显微镜、抗菌实验等测定涂层老化前后的接触角、表面形貌以及抗菌性能的变化。结果表明:含1.4%抗菌剂的抗菌涂层具有优秀的杀菌性能、亲水性能和耐老化性能。老化之前抗菌率达99.9%以上,老化处理后,涂层表面无明显变化,平均抗菌率达到95%以上,同时亲水角保持小于8°。     

低温快固化丙烯酸聚氨酯涂料的发展现状

从丙烯酸聚氨酯涂料的固化反应机理出发,系统分析了树脂、固化剂、催化剂和环境因素对丙烯酸聚氨酯涂层干燥速度的影响,重点讨论了羟基单体的种类和用量、亚胺结构的引入、玻璃化转变温度、相对分子质量及其分布、酸值及分子链结构等因素对树脂反应活性的影响。通过对目前低温快固化涂料研究中存在的问题的分析,指出精确控制树脂分子结构是实现修补涂料低温快固化的有效途径。     

Influence of manganese substitution into the A-site of perovskite type Ca1−xMnxTiO3 ceramic

Ca_1−xMn_xTiO₃ (x = 0–1.0) perovskite ceramics were prepared by conventional solid state reaction. XRD was used to confirm the microcrystalline nature of the Ca_1−xMn_xTiO₃ crystals. For the x = 0 composition, the XRD patterns were those of a single orthorhombic perovskite while for x = 0.2–0.8, the XRD spectra were those of two orthorhombic perovskite phases: CaTiO₃ and MnTiO₃. For x = 1, XRD pattern was that of the MnTiO₃ phase only. The morphology and particle size of the grains of the different composition were observed using SEM. The size of the particles increased from 0.2 μm to 2–3 μm as x increased from 0 to 0.6. The room temperature dielectric constant at the frequency of 110 kHz for the x = 0.2 and x = 1.0 ceramics were ∼3.41 × 10⁴ and ∼4.99 × 10³, respectively. The ESR linewidth of samples increased with increasing manganese content due to the formation of magnetic cluster. Our ESR studies indicate that the manganese ions are in the Mn⁴⁺ state.     

Porous hydroxyapatite ceramics by ice templating: Freezing characteristics and mechanical properties

Ice templating produces porous hydroxyapatite (HA) scaffolds with a lamellar morphology and aligned channels when using aqueous HA slurries. We investigated the freezing characteristics of HA slurries with regard to the pore structures of the porous HA scaffolds. We found that by increasing the cooling rate, the lamellar spacing decreased. The average lamellar spacing is about 785.7 μm at a cooling rate of 1.3 °C/min. The porous geometry changes from lamella and well aligned channels to a partial dendrite and partially aligned cavities with a decrease in the initial nucleation temperature and an increase in the degree of supercooling. Additionally, we determined the relationship between compressive strength and porosity. The compressive strength of the porous HA scaffolds reach 6.7 MPa at a porosity of 64% and the lamellar spacing is about 124 μm.