Coronoelectrets based on composites of high density polyethylene with a TlGaSe<Subscript>2</Subscript> semiconductor filler

In the thesis reports concerning the results of the study of the thermally stimulated depolarization and electret properties of the compositions of HDPE + x%, where x = 1, 3, 5, 7, 10, it is found that the composites with x = 5 and 7 are valuable electret materials with a lifetime of 360 days, 50 times higher than the lifetime of pure high density polyethylene.     

The treatment influence on the electric strength and conductivity of fibroin

The influence of thermal treatment and liquid nitrogen treatment of cocoons on the electric properties of natural silk fibroin has been studied. It is found that, at the cocoon treatment by liquid nitrogen, the ratio of the amorphous and crystalline parts of the fibroin is preserved and the concentration of submicrocracks in them changes to a lesser extent than at treatment by heated air and a UHF field. The increase of the degree of crystallinity in the polymers leads to a certain increase of their breakdown voltage.     

Study of polymer-piezoceramic composites by the radio-thermo-luminescence method

In this work, the features of the dependence of radiothermoluminescence (RTL), charge stabilization, change of the temperature of structural β-and γ-transitions on the dose of γ-irradiation and degree of filling Φ of composites based on high-density polyethylene (HDPE) and piezoceramic fillers of the PKR-3M type are investigated. It is shown that the dependences of thermoluminescence intensity of the filling degree J(Φ) are characterized by extrema at the filler content as high as 5 vol % and a dose D = 20?30 kGy. It is shown that γadiation at defined doses leads to inhibition of the process of β-relaxation of HDPE in the composition, which can be associated with the formation of new trapping centers of excess charges of electrets.     

Improvement of the Electret Properties of Polystyrene with Introduction of Titanium Dioxide

The electret properties of polystyrene composites with titanium dioxide were studied. The optimal parameters were defined for manufacturing corona electrets based on polystyrene. The introduction of 2–10 vol % titanium dioxide into polystyrene resulted in better electret performance owing to an increased portion of polymer macromolecules with a reduced mobility, the appearance of interphase polarization, and the formation of high-energy traps at the polymer–filler interphase boundary. It was shown that the thermal stability of the electret properties significantly increased for the polystyrene filled with titanium dioxide.     

Effect of the electrothermopolarization on the electret properties and the charge state of polyethylene nanocomposites with Cr and PbCrO4 additives

The results of studying the effect of electrothermopolarization on the electret properties and charge state of PE + Cr and PE + PbCrO₄ composites are described. It is shown that an increase in the polarization field intensity to E _p = 5 × 10⁶ V/m leads to an improvement in the polarization processes in the composites; at E _p > 5 × 10⁶ V/m, the space charge concentration apparently increases, which results in the deterioration of the electret properties. The observed effect can be attributed to the repeated electron capture by deeper traps owing to the internal electric field. In addition, the intensity of the TSD peaks and therefore the number of stabilized charges for the composites polarized at high intensities are higher than for the samples polarized at low intensities.     

Radiothermoluminescence of γ-irradiated composites of polypropilene and dispersed oxides

The peculiarities of stabilization of the excess charges in composites based on PP and dispersed metal oxides are investigated using the method of radiothermoluminescence (RTL). It is shown that introduction of fillers such as BeO and ZrO₂ into PP leads to change in the intensity and temperature of realization of the β₁, β, α, and α₁ peaks on the RTL curves, and this can be used to predict the electroactive, dielectric and physical mechanical properties of the composites based on them.     

光学功能化蚕丝纤维材料

家蚕蚕丝是一种天然的蛋白质纤维,蚕丝及其衍生物（凝胶、蚕丝薄膜和海绵等）具有独特的力学性能、良好的生物相容性和生物降解性,已经被应用在纺织、生物医学等领域。最近,利用蚕丝独特的性质制备光学功能化蚕丝吸引了研究者的兴趣。基于对蚕丝的丝胶和丝素结构组成的总结,介绍了目前蚕丝结构的相关研究进展,综述了近年来对光学功能化蚕丝的研究,具体包括光学功能化蚕丝的重要种类、制备和应用。重点介绍了荧光性功能蚕丝基因工程、喂食法和复合等制备方法,该种材料用于生物支架成像、药物缓释载体和光学器件等领域。总结了利用生物仿生技术制备具有光子晶体结构色的蚕丝材料,这为化妆品,变色服饰和生物光控器件开辟了新方向;此外,蚕丝材料还可以应用于非线性光学领域,如光限幅和激光防护。     

The response of carbon black filled high-density polyethylene to microwave processing

Microwave processing has numerous advantages over traditional methods of heating. Most thermoplastics, such as high-density polyethylene (HDPE), are nearly transparent to electromagnetic radiation. Carbon black (CB) filled HDPE was prepared in order to improve the microwave heatability of HDPE. The heating response of HDPE/CB composites to microwave exposure and the effects of this exposure on the mechanical and physical properties of material were investigated. The addition of CB particles improved the microwave heatability of HDPE, and microwave heatability of composites varied with CB content, in which an average temperatures of up to 139 °C above ambient were measured for 20 wt% CB composites after a exposure duration of 150 s. Microwave exposure had no obvious effect on rheological property of HDPE/CB composites. Mechanical properties of HDPE/CB composites are relatively improved after microwave exposure. Scanning electronic micrograph (SEM) analysis presented that the interface defects between CB particles and HDPE matrix are significantly reduced and a better combination was found after microwave exposure. Differential scanning calorimetry (DSC) analysis showed that the melt point of HDPE with CB shifted toward high temperature and degree of crystallinity increased after microwave exposure.     

Charge state of composites based on polyethylene with semiconductor filler TlInSe<Subscript>2</Subscript>

In the present work, the spectra of currents of thermostimulated depolarization for composite corona electret LDPE + ε vol % TlInSe₂ are obtained by the thermoactivation spectroscopy method [11] and their electret properties and change conditions are investigated.     

Impact of γ-Radiation on Photothermoluminescence of Polypropylene-CdS/ZnS Composites

We have obtained polypropylene-based (PP) specimens of polymer composites with various volume fractions of binary compound based on cadmium sulfide and zinc sulfide (CdS/ZnS). Their photothermoluminescence, photostimulated by UV exposure, was studied before and after exposure to γ-radiation. The photothermoluminescence (PTL) method revealed an increased concentration of local levels in the range of 500–600 nm of the semiconductor loading agent and in the phase-boundary layer of the polymer-loading agent due to impact of γ-radiation with doses up to 100 kGy. It was demonstrated that composites with the composition PP–(CdS/ZnS) 90 (10 vol %) are characterized by an intensification of relaxation processes at a temperature 300 K, which can be regarded as an improvement in the performance properties of the obtained composites. The radiothermoluminescence (RTL) method revealed an increase in the intensity of the RTL and PTL peaks due to introduction of binary CdS/ZnS compounds into the PP.     

The effect of nano-sized calcium carbonate on thermodynamic parameters of HDPE

One of the main limitations in application of polymers, particularly thermoplastic polymers such as high density polyethylene (HDPE) and polypropylene (PP), is their poor thermal properties. To promote mechanical and thermal properties of HDPE, ceramic phases are added to it. In the current research, to enhance thermal properties of HDPE, nano-sized calcium carbonate was used. For this purpose, HDPE/10%CaCO₃ nanocomposite was fabricated using a twin screw mixer–single screw extruder. The properties of HDPE and its nanocomposite were investigated through differential scanning calorimetery (DSC) and thermo mechanical analyzer (TMA) tests. The results of DSC tests showed that the addition of nano-sized calcium carbonate to HDPE caused to increase the heat capacity, sensible heat and crystallinity index. The TMA results illustrated an increase in dimensional stability of HDPE as nano-sized of calcium carbonate added to it.     

Relaxation of the electret charges of PET films after the action of aerosol particles

The electret properties of PET films before and after the action of aerosol particles (APs) are investigated. These properties are shown to depend not only on the nature and method of the polymer polarizations but also on the variations in their micro- and permolecular structure (PMS). The singularities of the differences in the processes of the relaxation of stabilized electret charges in the bulk and in the surface layers of PET films have been revealed based on the results of the analysis of the spectrum of the thermostimulated depolarization (TSD) current. The thus-obtained data on the variations in the relaxation properties of electret PET film electrets allow us to say that these films can be used for fabricating efficient aerosol catches for different purposes and aerosol-sensitive sensors operating based on the principle of decreasing the values of the electret charges.     

Dielectric properties and radiothermoluminescent features of polypropylene/α-Al2O3 highly filled compositions

The high-frequency dielectric properties (? and tanδ) and the α-, β-, and γ′-relaxation processes in polypropylene (PP) composites with an α-Al₂O₃ filler were studied. It was shown that the experimental and calculated values of ? and tanδ for the PP/α-Al₂O₃ composition with the filler content being up to 20–25 vol % and those for highly filled composites (with the filler content being more than 30–40 vol %) are described by different models. It was found that the introduction of α-Al₂O₃ into PP results in a significant change in the shape and position of the β and α′ maximums. The relaxation nature of the luminescence peaks in the RTL spectra in the region of the β and α′ relaxations suggests that the highly filled PP/α-Al₂O₃ composites (up to 40 vol % of the filler) can be used as a γ-dosimetric material in the dose range up to 50 kGy.     

石墨烯/高密度聚乙烯在水润滑条件下的摩擦学性能研究

目的 探究石墨烯/高密度聚乙烯高分子材料在水润滑条件下的摩擦学性能,提高高密度聚乙烯的自润滑和耐磨损性能.方法 采用石墨烯纳米片填充高密度聚乙烯材料,利用RTEC摩擦磨损试验机,开展新型复合材料在水润滑条件下的摩擦学性能研究.通过分析新型复合材料的典型机械性能、摩擦系数、磨损形貌以及摩擦副接触表面的元素成分及分布情况,揭示石墨烯/高密度聚乙烯在水润滑条件下的摩擦磨损机理.结果 新型复合材料的拉伸强度、撕裂强度和肖氏硬度均随着石墨烯纳米片含量的增加而先增高后降低,1.5％石墨烯纳米片改性高密度聚乙烯表现出最高的强度,分别为19.81 MPa、31.34 MPa和92.6HSA.新型复合材料的平均摩擦系数和体积行程磨损率总体随着石墨烯含量的增加而减小,1.5％石墨烯纳米片改性的高密度聚乙烯平均摩擦系数和体积行程磨损率比纯高密度聚乙烯分别降低了53.6％和73.9％.Si3N4陶瓷球与1.5％、0.6％石墨烯纳米片改性高密度聚乙烯进行3600 s对磨试验,其磨损区域的碳元素质量分数分别约为3.5％和0.3％,表明含量较高的石墨烯纳米片有利于在微观界面形成石墨烯润滑层,从而降低摩擦系数.结论 石墨烯纳米片显著影响高密度聚乙烯的自润滑性能和耐磨损性能,适量的石墨烯纳米片促进了高密度聚乙烯磨损界面石墨烯润滑层的形成,降低摩擦系数和磨损量.该研究可为设计低摩擦、耐磨损的水润滑轴承复合材料提供参考.     

The effect of gamma irradiation on electret properties of polyethylene

The paper describes the electret properties of low-density polyethylene and the effect of gamma irradiation on them. It is shown that the thicker polyethylene film the more stable the surface potential, electric field strength, and effective surface charge density values. The negative impact of gamma-radiation on the electret properties of the films that is caused by the release of the injected charge carriers from the traps due to clearing the energy barrier thanks to radiation energy is revealed. Irradiated polyethylene films, in turn, are polarized badly in a corona discharge because of the oxygen-containing groups on the surface formed during gamma-irradiation that act as charge carrier traps with low capture energy. It was found that the formation of cross bonds in the bulk of the polymer and carbonyl groups on its surface slightly raises the degree of crystallinity and the specific volume resistivity and decreases the specific surface resistivity.     

Electrothermopolarization influence upon the structure and properties of a composition on the basis of polyethylene and Co(AlO<Subscript>2</Subscript>)<Subscript>2</Subscript>

The influence of electrothermopolarization on the structure and properties (electret, strength) of a composition on the basis of polyethylene and a low-molecular dye Co(AlO₂)₂ was investigated. It was experimentally established that the additive Co(AlO₂)₂ changes the polyethylene structure. As a result, the electret properties of the composition change. Correlation of the strength properties with the changes of the degree of the crystallinity of the polyethylene was observed.     

A study of the fluorescence spectra and dielectric properties of HDPE + x vol % TlGaSe2 composites

The results of studying the fluorescence spectra of HDPE + x vol % TlGaSe₂ (x = 0, 1, 5, 10, and 20) composite materials in the wavelength range of 400–600 nm are described. The fluorescence effect is revealed, and the wavelength-dependent qualitative relationship between the composition and the fluorescence spectrum of the composite is found. The temperature dependences of the dielectric permeability and the dielectric loss tangent of the HDPE + x vol % TlGaSe₂ (x = 0, 1, 3, 5, 7, and 10) composites in the temperature range of 300–500 K are studied.     

Dielectric properties of polymer composites with TlInSe2 semiconductor filler

The dielectric properties of polymer composites on the basis of polyethylene and polypropylene with TlInS₂ semiconductor filler are investigated. It is shown that the changes in these properties that were observed are caused by polarization processes occurring on the polymer-filler interface.     

HDPE/TiB_2-CB导电复合材料组织与性能研究

采用熔体共混法制备了高密度聚乙烯/二硼化钛-炭黑导电复合材料。研究了少量CB（炭黑）对HDPE/TiB2-CB复合材料室温电阻率、正温度系数（PTC）、负温度系数（NTC）效应和热循环稳定性的影响,并对HDPE/TiB2-CB复合材料的PTC效应随CB含量的变化原因进行了探讨。结果表明,加入少量CB明显降低了TiB2的填充量,由50%降为30%（质量分数,下同）。HDPE/TiB2-CB复合材料中CB含量为3%、TiB2含量为27%时复合材料的PTC强度达7,室温电阻率仅为1.25Ω.m,经过多次热循环后PTC效应仍然稳定。当CB含量超过6%时,室温电阻率稍有降低,但PTC强度迅速降到3.5以下。SEM分析表明CB对TiB2及CB在基体中形成导电通道影响明显。     

The Modification of Surface of Dispersed Fillers for Their Application in Polymer–Elastomer Composites

Structural studies of mechanoactivation-modified dispersed fillers (natural zeolite and magnesium spinel) and polymer–elastomer composites on their basis are performed. It is shown that mechanoactivation in an Aktivator-2S planetary mill (80.3 g, 900 rpm) allows halving the treatment duration and providing the greatest changes in the structure of dispersed fillers as compared to Pulverisette-5 (22 g, 400 rpm). The predominant localization of particles of mechanically activated fillers at the phase interface of the polymer mixture (BNKS-18/UHMPE) is found. This results in intensification of their interaction at the interface and, hence, improvement in obtaining polymer–elastomer materials with an improved set of physicomechanical properties.