Synergistic effects of zeolites on a novel intumescent flame-retardant low-density polyethylene (LDPE) system

A char forming agent and silica-gel microencapsulated APP were selected to form novel intumescent flame-retardant system (IFR) to prepare flame-retardant low-density polyethylene (LDPE) composites, and then the influence of zeolites on the thermal and flame-retardant properties of flame-retardant LDPE composites were studied. With the addition of 1 wt% zeolites to LDPE/IFR system, the LOI value increases from 29.0 to 34.0 %. The results of cone calorimetry show that the heat release rate peak and total heat release of the intumescent flame-retardant LDPE composite with 1 wt% zeolites decreases remarkably compared with that of without zeolites. The scanning electron microscopy indicates zeolites with suitable content can improve the quality of the char layer of flame-retardant LDPE composite which is more coherent and dense. The zeolites with the appropriate content can remarkably improve the flame-retardant properties of the LDPE composites.     

Transport properties of annealed,drawn low-density polyethylene (LDPE)

The specific concentration c_a of methylene chloride, the zero-concentration diffusion coefficient D₀, and the concentration coefficient γ_D of the diffusivity in drawn and annealed LDPE were measured. The influence of the drawing rate, of annealing with the ends of the sample free and fixed and the effects of time of standing at room temperature after annealing were investigated. The observed transport properties are in good agreement with the microfibrillar model of fibrous structure, its relaxation during annealing, and the slow crystallization of relaxed tie-molecules upon standing at room temperature.     

High-energy C+ ion-irradiated low-density polyethylene (LDPE): Spectroscopic and morphological investigation

The optical absorption spectra of 3.6 MeV ¹²C ions irradiated low-density polyethylene (LDPE) show the gradual increase in the optical absorption and the shift from the near UV to the visible region with increase in ion fluence. The increase in absorption may be attributed to the generation of a conjugated system of bonds, which are also corroborated by FTIR. Scanning electron microscopic (SEM) studies reveal that the formation of linear network structure occurred at relatively lower ion fluence of 5×10¹³ ions/cm².     

Chemical transformations and changes in free volume holes in high-energy proton irradiated low-density polyethylene (LDPE)

Low-density polyethylene (LDPE) was irradiated with 4 MeV protons at different ion fluences. Chemical modifications were studied by UV–vis and Fourier transformed infrared (FT-IR) spectroscopy. Further, the changes in free volume holes were studied using positron annihilation lifetime spectroscopy. The different UV–vis absorption spectra show the maximum absorption at around 280 nm for the lower fluences whereas at the highest fluence a red shift is observed. This indicates formation of chromophoric groups that have the maximum absorption in that region. The formation of vinylidine, trans-vinylene, end-vinyl group, unsaturated linkage and carbonyl group were detected from FT-IR spectra. Positron annihilation lifetime spectroscopy reveals that the free volume hole size and their relative fraction first decrease, attaining a minimum value and subsequently increases with increase in ion fluence. These changes in free volume holes have been well correlated with the observed chemical transformations.     

Thermal and flame retardant properties of novel intumescent flame retardant low-density polyethylene (LDPE) composites

A char-forming agent (CFA) and silica-gel-microencapsulated ammonium polyphosphate (MCAPP) were selected to form novel intumescent flame retardant system (IFRs), and then the influence of this novel IFRs on the thermal and flame retardant properties of low-density polyethylene (LDPE) were studied. The results of cone calorimetry show that the flame retardant properties of LDPE with 30?wt% novel IFR (CFA/MCAPP?=?1:3) improve remarkably. The heat release rate peak, total heat release (THR) decreases, respectively, from 1479.6 to 273.5?kW?m^?2 and from 108.0 to 80.5?MJ?m^?2. The LDPE composite with CFA/MCAPP?=?1:3 has the excellent water resistance, and it can still obtain a UL-94?V-0 rating after treated with water at 70?°C for 168?h.     

Evolution of microstructure and crack pattern in NiO thin films under 200 MeV Au ion irradiation

NiO thin films grown on Si (100) substrate by electron beam evaporation method and sintered at 700 °C were irradiated with 200 MeV Au¹⁵⁺ ions. The fcc structure of the sintered films was retained up to the highest fluence (1×10¹³ ions cm^?2) of irradiation. However the microstructure of the pristine film underwent a considerable modification with increasing ion fluence. 200 MeV Au ion irradiation led to compressive stress generation in NiO medium. The diameter of the stressed region created by 200 MeV Au ions along the ion path was estimated from the variation of stress with ion fluence and found to be ～11.6 nm. The film surface started cracking when irradiated at and above the fluence of 3×10¹² ions cm^?2. Ratio of the fractal dimension of the cracked surface obtained at 200 MeV and 120 MeV (Mallick et al., 2010a) Au ions was compared with the ratio of the radii of ion tracks calculated based on Coulomb explosion and thermal spike models. This comparison indicated applicability of thermal spike model for crack formation.     

Opto-structural characterization of proton (3 MeV) irradiated polycarbonate and polystyrene

Polycarbonate (Makrofol-N) and polystyrene thin films were irradiated with protons (3 MeV) under vacuum at room temperature with the fluence ranging from 1×10¹⁴ to 1×10¹⁵ protons cm⁻². The change in optical properties, degradation of the functional groups and crystallinity of the proton-irradiated polymers were investigated with UV–vis, Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) techniques, respectively. The UV–vis analysis revealed that the optical band gap of irradiated Makrofol-N is reduced by 30% as compared to 27.5% in polystyrene at highest fluence of 1×10¹⁵ protons cm⁻², owing to higher electronic energy loss of protons in Makrofol-N. The calculations of the number of carbon atoms per conjugation length, N and number of carbon atoms per clusters, M embedded in the network of polymers further revealed that Makrofol-N is more modified as compared to polystyrene on proton irradiation. FTIR results reveal the reduction in absorption intensity of the main characteristic bands of both the polymers after irradiation. The proton-irradiated Makrofol-N shows a strong decrease of almost all of its characteristic absorption bands at about 1×10¹⁴ protons cm⁻². Beyond a critical dose an increase of almost all its characteristic bands are noticed, however, no such effect had been observed in polystyrene at this particular fluence. Appearance of new –OH groups was observed at the higher fluences in the FTIR spectra of both proton-irradiated polymers. XRD measurements show the decrease of the main peak intensity and the crystallite size, confirming the increase of amorphization in polymers under irradiation.     

Rheo-optical near-infrared (NIR) spectroscopy study of low-density polyethylene (LDPE) in conjunction with projection two-dimensional (2D) correlation analysis

A rheo-optical characterization technique based on near-infrared (NIR) spectroscopy is developed specifically to probe the submolecular-level deformation caused during a mechanical test. An illustrative example of the mechanical deformation of low-density polyethylene (LDPE) is provided to show how it can be utilized. A set of NIR spectra of the polymer sample were collected by using an acousto-optic tunable filter (AOTF) NIR spectrometer coupled with a tensile testing machine as an excitation device. While the substantial level of variation of spectral intensity was readily captured during the mechanical deformation of the LDPE, main feature of the NIR spectra was overwhelmed by the contribution from the baseline change. Projection 2D correlation analysis was then applied to selectively extract the signal contribution from the baseline fluctuation. The 2D correlation spectra revealed the predominant extension of amorphous tie chains followed by the rotation of crystalline lamellae, which induce elastic and plastic deformation of the LDPE, respectively.     

Radiation damage induced in Zircaloy-4 by 2.6 MeV proton irradiation

Journal of Radioanalytical and Nuclear Chemistry - Radiation damage induced in Zircaloy-4 by 2.6 MeV proton irradiation at low doses was studied. Our aim is to emulate the effect of...     

Morphology and properties of low-density (branched) polyethylene

The different types of morphology that can be developed in a large number of low-density (branched) polyethylene whole polymers, as well as in a series of fractions, have been studied for two different extreme crystallization modes. Concomitantly, thermodynamic properties of the same samples have also been determined. After isothermal crystallization at elevated temperatures, spherulitic structures are found in all the whole polymer samples. On the other hand, after rapid crystallization a variety of different types of supermolecular structures are observed which are shown to depend systematically on the concentration of side-chain branches and the relative proportion of high molecular weight species in the sample. This temperature dependence of the morphological forms is opposite to that previously reported for linear polyethylene. The studies with the fractions show that the individual species are not the cause of this behavior; rather, the total composition is the important factor. The thermodynamic properties are also quite different from those of linear polyethylene in showing virtually no molecular weight dependence and being governed primarily by the concentration of short-chain branches. The degrees of crystallinity as determined from density and enthalpy of fusion measurements do not vary much with the two extreme crystallization conditions employed, are not sensitive to the morphology, and differ from one another, even when well-developed spherulites are formed. A major influence of the branching concentration on these properties is clearly indicated.     

Simplified approach to modelling the catalytic degradation of low-density polyethylene (LDPE) by applying catalyst-free LDPE-TG profiles and the Friedman method

The course of the thermogravimetric degradation of LDPE in the presence of different aluminosilicate catalysts was modelled by applying a differential isoconversional Friedman approach. An analysis of catalyst-free PE-TG profiles confirmed that the degradation profiles predicted by various reaction models overlap over the entire conversion range once the data are analysed using a differential isoconversional Friedman approach. The results demonstrate that the catalytic degradation of LDPE can be predicted by a correlation twin, i.e. the two specific functional relations between the activation energy, pre-exponential factor and conversion. The crucial step for ensuring good agreement between the predicted and the measured profiles is to extrapolate the discrete values of the activation energies and pre-exponential factors to the zero conversion. It turns out that linear extrapolation and interpolation from the discrete values outperforms regression functions based on various order polynomials, and that apparent deviations from the global trend at lower conversions are not a consequence of the misinterpretation of the experimental results but are an experimental fact. The assumption about the compensation effect between the pre-exponential factor and activation energy holds within the conversion range from 10 to 90%. However, it is generally unsuitable for modelling purposes due to the uncertain extrapolation of the kinetic parameters to the zero conversion.

     

Effect of 120 MeV Au9+ ion irradiation on the structure and surface morphology of ZnO/NiO heterojunction

ZnO/NiO thin films, each of thickness 100 nm, were deposited on Si(100) substrate by pulsed laser deposition method. The resulting heterojunction, ZnO/NiO/Si, was irradiated by 120 MeV Au⁹⁺ ions and characterized by grazing incidence X‐ray diffraction (GIXRD), Raman spectroscopy, and atomic force microscopy (AFM). The GIXRD confirmed the presence of both NiO and ZnO in the samples. Ion irradiation induced suppression of crystalline nature, and the recrystallization of the same occurred at the fluence of 1 × 10¹³ ions cm⁻². The occurrence of most intense band at 302 cm⁻¹ in Raman spectra corresponds to the symmetric stretching vibration of ZnO. The linear shift of stretching mode of ZnO with ion fluence could be associated with the effect of compressive stress in the material. AFM analysis of the films indicated that the rms roughness increased when the film is irradiated at a fluence of 1 × 10¹² ions cm⁻². Beyond this fluence, the value of roughness decreased up to fluence of 1 × 10¹³ ions cm⁻² and increased thereafter. To see the effect of the stress of buffer layer on the surface layer, we calculated the stress for NiO layer with ion fluence form the lattice parameter. Comparing the stress of buffer layer with roughness of surface layer at the given fluence, we can say that the compressive stress in the buffer layer could possibly control the roughness of the surface layer.     

Binary and ternary (liquid + liquid) equilibrium for {methylcyclohexane (1) + toluene (2) + 1-hexyl-3-methylimidazolium tetracyanoborate (3)/1-butyl-3-methylimidazolium tetracyanoborate (3)}

This paper focuses on the study of the solubility behaviour of 1-hexyl-3-methylimidazolium tetracyanoborate [HMIM][TCB] and 1-butyl-3-methylimidazolium tetracyanoborate [BMIM][TCB] in combination with methylcyclohexane and toluene as representatives for non-aromatic and aromatic components. Binary and ternary (liquid + liquid) equilibrium data were collected at three different temperatures and at atmospheric pressure (0.1 MPa). The experimental data were well-correlated with the NRTL and UNIQUAC thermodynamic models; however, the UNIQUAC model gave better predictions than the NRTL, with a root mean square error below 0.97%. The non-aromatic/aromatic selectivities of the ionic liquids make them suitable solvents to be used in extractive distillation processes.     

Hot band spectroscopy of CCO in the C–O stretching region: The (ν1 + 2ν3) − 2ν3 and (2ν1 + ν3) − (ν1 + ν3) bands

Two C–O stretching hot bands, (ν₁ + 2ν₃) − 2ν₃ and (2ν₁ + ν₃) − (ν₁ + ν₃), of the CCO radical in the ground electronic state were measured. These hot bands are red shifted by approximately 70 cm⁻¹ compared to the C–O stretching fundamental. CCO was produced in a discharge through a flowing mixture of carbon suboxide and helium. The spectra were recorded using a diode laser spectrometer. The band origins were determined to be 1904.32512(62) and 1902.69130(56) cm⁻¹ for (ν₁ + 2ν₃) − 2ν₃ and (2ν₁ + ν₃) − (ν₁ + ν₃), respectively. The measurements in this band together with previously reported frequencies in the C–C and C–O stretching regions were analysed to determine harmonic frequencies and anharmonicity constants.     

The effect of gamma irradiation on mechanical, and thermal properties of recycling polyethylene terephthalate and low density polyethylene (R-PET/LDPE) blend compatibilized by ethylene vinyl acetate (EVA)

A study has been made on the compatibility of recycled polyethylene terephthalate (R-PET) and low density polyethylene (LDPE) blend in the presence of ethylene vinyl acetate (EVA) as a compatibilizing agent prepared by extrusion hot stretching process. EVA content in the blend as a compatibilizing agent was an enhancement effect on radiation crosslinking of R-PET/EVA/LDPE blends and the highest radiation crosslinking was obtained when the EVA content was reached at 10 % EVA when irradiated by gamma irradiation. Blends containing different (EVA) ratios were irradiated to different doses of gamma irradiation 25, 50 and 100 kGy. The effect of the compatibilizer and radiation on mechanical, thermal properties of R-PET together with LDPE and morphology has been investigated. It was found that gamma irradiation together with the presence of compatibilizing agent (EVA) has positive effect on the mechanical and thermal properties of R-PET/LDPE blend. The structural properties of R-PET/LDPE modified by gamma irradiation and EVA as compatibilizing agent was examined by SEM. Also, it was found that the optimum concentration of EVA and gamma irradiation dose was found to be 10 % EVA and 100 kGy, respectively.     

(Liquid + liquid) equilibrium for the system {ethyl stearate(1) + ethanol(2) + glycerol(3)}

This paper reports the results of a new experimental study on the (liquid + liquid) equilibrium of the system {ethyl stearate(1) + ethanol(2) + glycerol(3)} at atmospheric pressure and at T = (313.15 and 323.15) K. The equilibrium compositions were measured by gas chromatography. Ternary diagrams were obtained for each temperature and the equilibrium data were compared to the system in the presence of salt (NaCl) at T = 323.15 K. The experimentally determined (liquid + liquid) equilibrium data were satisfactorily correlated with NRTL and UNIQUAC equations. A comparative analysis was performed using the UNIFAC-LLE group contribution method. From the results presented herein good predictions were obtained for this ternary system.     

Modeling of the quaternary NaCl + KCl + CH3OH + H2O mixed electrolyte system: Binary and ternary mixing (ion + ion) and (ion + nonelectrolyte) interaction parameters

The purpose of this work is modeling of the quaternary system of mixed NaCl + KCl electrolyte in mixed CH₃OH + H₂O solvent, with different alcohol mass fractions by using particularly, the Pitzer (P) and Pitzer–Esteso (PE) equations and based on potentiometric measurement technique. The experimental data are obtained by different molal salt ratio r (r = m_NaCl/m_KCl = 100, 150, 200 and 250) in mixed solvent with different alcohol mass fractions x (x = 0.10, 0.20, 0.30, 0.40, and 0.50) in water. A galvanic cell is employed for collecting the potentiometric data by combining a Na⁺ glass membrane and Ag/AgCl electrodes and using different series of electrolyte solutions, at defined constant ionic strengths, with the molality ranging from 0.0005 up to 3.5 mol · kg⁻¹, at T = 298.15 ± 0.05 K of experiments. Comparison of the models shows that the modified Pitzer equation by Esteso (PE) present a better fit of the experimental data.     

Natural weathering test for films of various formulations of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE)

Natural (outdoor) weathering test was performed to investigate the UV stability of thin films (0.06 mm) of linear low density polyethylene (LLDPE) and low density polyethylene (LDPE). The PE films were prepared from various formulations of LLDPE and LDPE resins. Some of these films contained a single high molecular mass HALS only, along with a primary antioxidant (i.e. Irganox 1010) and a secondary antioxidant (i.e. Irgafos 168 or Alkanox TNPP), while others contained HALS and UVA (i.e. Chimassorb 81 or Tinuvin P or Tinuvin 326) along with these antioxidants. The HALS used was either an oligomeric or a synergistic mixture of a high molecular mass (HMM) hindered amine stabilizer and co-additives. The UV stability was investigated by exposing the prepared films at 45° towards south in the direct sunshine up to 365 days. Fifty percent of tensile strength retention was determined for all these exposed films and it was found that the films containing a single HALS gained improved UV stability by about two to 12 fold over the pure films. On the other hand, films that contained a combination of HALS and UVA obtained further improved UV stability over the films containing a single HALS (both have antioxidants). Films containing a single HALS reached 50% TS retention within 205 days, whereas, films containing a combination of HALS and UVA reached 50% TS retention within 590 days, which is about three times further improvement in UV stability.