Novel flame retardants containing cyclodextrin nanosponges and phosphorus compounds to enhance EVA combustion properties

A novel flame retardant intumescent system, aimed to improve the fire stability of ethylene vinyl acetate copolymer (EVA), has been prepared by melt blending of the copolymer and a complex of cyclodextrin nanosponge-phosphorus compounds. As compared to traditional systems, this complex, stable in processing conditions, has the advantage that nanosponges act as both carbon sources and foam forming agents while the phosphorus compounds are able to directly generate phosphoric acid in situ. In this context, cyclodextrin nanosponges undergo dehydration in presence of the acid source, generating water vapour and char, and thus protecting the copolymer against combustion. Different acid sources have been investigated in order to reach the optimum interaction with the nanosponges. Raman measurements and thermogravimetric analyses have shown that the cavities of nanosponges entrapped the phosphorus derivatives forming stable complexes at the temperature of EVA processing. Different amounts of these complexes (5, 10 and 15 wt.%) have been added to EVA via melt blending and their flame retardancy properties measured by UL94 test and cone calorimetry. Strongly modified burning kinetics, as compared to the behaviour of the neat copolymer, have been found by UL94 test: V2 classification has been achieved for every formulation regardless of the type and the amount of complex used. EVA combustion behaviour by cone calorimetry has also been significantly affected: the heat release rate decreased dramatically down to ca. 20% in the presence of these new additives.     

Determination of Zn(II) in natural waters by ICP-OES with on-line preconcentration using a simple solid phase extraction system

An on-line zinc preconcentration and determination system implemented with inductively coupled plasma optical emission spectrometry (ICP-OES) was developed. The zinc was precipitated and retained on a minicolumn filled with ethyl vinyl acetate (EVA) at pH 9.0, without using any complexing reagent. The zinc ions were eluted from the minicolumn with 10% (v/v) hydrochloric acid. Experimental conditions including pH and sample loading and eluting variables were evaluated and established.An enrichment factor (EF) of 44 was obtained for Zn²⁺ with a preconcentration time of 120 s. Under the optimal conditions, the value of the limit of detection (3σ) for the preconcentration of 10 mL of sample was 0.08 μg L^{− 1}. The sampling frequency was about 24 h^{− 1}. The precision for six replicate determinations (repeatability conditions) at 50 μg L^{− 1} Zn level was 3.94% relative deviation standard (RSD), calculated from the peak heights obtained. The methodology was successfully applied to the determination of zinc in tap water samples and in a certified VKI reference material QC Metal LL1 DHI (Water & Environment) Denmark.     

Influence of M w of LDPE and vinyl acetate content of EVA on the rheology of polymer modified asphalt

Asphalt binder was modified by low-density polyethylene (LDPE) and ethyl vinyl acetate (EVA) polymers to investigate the structure–property relationships of polymer-modified asphalt (PMA). The PMA was prepared in a high-shear blender at 160 °C. The optimum blending time (OBT) for each polymer was determined following a separate investigation. OBT was influenced by M_w, MWD, and polymer structure. The influence of M_w of LDPE and vinyl acetate (VA) content of EVA on PMAs was studied by rheological tools. Polymer modification improved the rheological properties of base asphalt. EVA–PMAs were found to be less temperature sensitive than LDPE-modified asphalts. LDPE modification increased flow activation energy (E_a) but EVA modification decreased E_a. Both VA content and M_w of LDPE have influenced the storage stability of PMAs. The low-temperature properties of PMAs and short ageing tests were not influenced by polymer type. On the other hand, the high-temperature properties of PMAs were strongly influenced by M_w of LDPE and VA content of EVA. Overall, EVA with low VA content showed the best temperature resistance to high- temperature deformations, the highest upper service temperature as well as the best storage stability.     

The effect of different variables on the accelerated and natural weathering of agricultural films

Lifetimes required for greenhouse cover films depend heavily on the country, especially the tradition in the country. They vary from one agricultural season (i.e. 6-9 months) to several years and are strongly dependent on the use of pesticides which destroy the photostabilisers (HALS and nickel quenchers) and on other geographic and climatic factors (solar irradiation, temperature, winds, etc.).In this work, we have measured the duration of four real agricultural films using the European Standard EN 13206:2001 conditions for the accelerated weathering test and the results have been compared to their duration under accelerated weathering using more aggressive conditions (pesticide spraying, different chamber temperatures) and under natural weathering. We have also explored the effect of the backing material in the artificial weathering test and of the starting date in the natural weathering. The final goal of this study is to obtain good correlations between accelerated weathering, natural weathering at defined, controlled conditions and weathering in real-use conditions for agricultural films.     

Radiation Effects on Optical Properties of Ethylene Vinyl Acetate Copolymer Films

The optical properties of ethylene vinyl acetate (EVA) film have been studied. The effects of gamma irradiations on the optical spectrum of EVA films have been investigated using spectrophotometric measurements of reflectance and transmittance in the wavelength range 200–1100 nm. The absorption spectra were recorded in the UV–vis region for the unirradiated and irradiated films (from 0 to 50 kGy). Optical constants such as refractive index (n), extinction coefficient (K), and complex dielectric constant have been determined, as well as the optical dispersion parameters and high frequency dielectric constants. A large dependence of the fundamental optical constants on the irradiation dose was noticed. On irradiation, a higher refractive index was obtained as compared with that for unirradiated film. The dispersion parameters, such as E ₀ (single‐oscillator energy), E _d (dispersive energy), and M _?1 and M _?3 (moments), are discussed in terms of the single‐oscillator Wemple–DiDomenico model.     

Crystalline and relaxation properties of ethylene copolymer films inserted between two steel sheets

The relaxation and crystalline properties of ethylene vinyl acetate (EVA) co-polymers inserted in steel/polymer/steel assemblies were studied. To investigate the properties of the interfacial region, polymers of different thickness inserted in the assemblies were analyzed. The studied EVA copolymers are semicrystalline polymers. The relaxation properties of the amorphous phase were investigated by dynamic mechanical measurements performed on the steel/polymer/steel assemblies, and the crystalline properties were studied by differential scanning calorimetry (DSC). The results indicate that, for low polymer thicknesses, the mobility of the amorphous phase is significantly reduced. Significant changes in the crystalline organization also were observed when the polymer thickness decreased, with the presence of more numerous disorganized crystals for thin EVA layers. These crystals can act as physical ties that reduce the mobility of the neighboring amorphous chains. These results indicate the formation of an interphase layer of reduced mobility.     

A Review of Online Real-Time Process Analyses of Melt-State Polymer Using the Near-Infrared Spectroscopy and Chemometrics

Abstract

This review describes the online process monitoring of the melt-state polymer by near-infrared (NIR) spectroscopy and chemometrics. The spectra of linear low-density polyethylene (LLDPE), random polypropylene (RPP), block polypropylene (BPP), and ethylene-vinylacetate (EVA) copolymer in melt states measured by an online monitoring system with a Fourier transform near-infrared spectrometer are discussed. The calibration models for the density of LLDPE, the content of ethylene copolymers in RPP and BPP, and vinylacetate concentration (VA) in EVA copolymers using partial least squares regression are reported. The continuous monitoring of the LLDPE density at the real plant is described as an example of online monitoring using NIR spectroscopy and chemometrics. For the precise prediction of VA in EVA, a combination method using regression and discrimination was inducted. Three compensation methods for the effect of the temperature change in the RPP and BPP samples are shown. Conventional calibration transfer methods are introduced, and a practical calibration transfer method using two samples and its performance are reported using BPP and RPP spectra. Moreover, the possibility of a calibration correction method using one sample for the realization of long-term traceability is indicated by the example of the relocation.     

Acoustic behaviour and equation of state of amorphous ethylene–vinyl acetate copolymer studied by means of high-pressure Brillouin scattering spectroscopy

The determination of the equation of state (EOS) of amorphous materials is very important for fundamental understanding of the glass transition and applications as well. Simultaneous observation of both longitudinal and transverse acoustic modes by Brillouin scattering spectroscopy has been one of the major methods to obtain EOS of amorphous materials. However, the transverse acoustic mode is hardly seen from some of the amorphous polymers, which makes it difficult to derive EOS. The temperature and pressure dependences of the acoustic properties of amorphous ethylene–vinyl acetate (EVA) copolymer were measured by using high-pressure Brillouin scattering spectroscopy. The temperature variation induced large changes in the frequency shift and linewidth of the longitudinal acoustic mode due to strong coupling between the structural relaxation process and the propagating density fluctuations. The residual linewidth in the glassy state was attributed to the remnant intramolecular motions of EVA, the activation energy of which was estimated to be ～3.30 ± 0.27 kcal/mol. The pressure–density relationship of EVA could be obtained for the first time by measuring the refractive index and using the Lorentz–Lorenz equation. The density and the refractive index exhibited monotonic increase up to approximately 12 GPa. The strong reduction of the acoustic damping at low pressures below ～3 GPa was attributed to the collapsing free volume in EVA. The present study clearly shows that measuring the refractive index by high-pressure Brillouin spectroscopy may be an alternative method to get the EOS of polymeric materials whose transverse acoustic mode is too weak to be observed.     

Mixed surfactant enabled EVA emulsion for PPD applications

PPD emulsion product is advantageous for use in sub-ambient temperature as it improve the physical handling characteristic compared to traditional product. However, existing PPD emulsion system is solely implementing a single anionic surfactant system which leads instability towards a series of temperature changes. Therefore, mixed surfactant (anionic and non-ionic) surfactant was introduced to overcome this problem. Through this research, sodium dodecyl sulfate (SDS) act as anionic surfactant and Tween 80 used as non-ionic surfactant in this study. The stability of an emulsion was identified through particle size and zeta potential. For the mixed surfactant composition, the result show the presence of SDS content contributes in reduction on particle size. Furthermore, the study on effectiveness of surfactant on EVA emulsion was evaluated. The result indicates with present of surfactant, interfacial surface tension was reduced. The freezing point and pour point depressant test of the EVA emulsion was evaluated. Present of non-ionic surfactant help in stability and flow-respond at low temperature. Mixed surfactant system provides sufficient protection from droplet size growth caused by the temperature changes which eventually leads to instability.