Rapid assessment of weathering stability from exposure of polymer films. I. Real and simulated weathering of commercial ABS terpolymers

Changes in the infared transmission spectra of thin films were used to follow the natural and artificial weathering of ABS terpolymers. Photo-oxidation of the polybutadiene moiety, which is the major process involved, occurs only after a well-defined amount of ultraviolet energy has been absorbed. Therafter, unsaturation decreases in a first-order manner with respect to UV energy absorbed. Under artificial conditions with constant UV intensity, energy absorbed is synonymous with time, but this is not so in natural exposure because of the variability of solar energy and its UV content. The method permits rapid comparison of commercial grades of ABS with the advantage of using natural conditions. It has been shown that pigmentation (3.6 phr brown and 1.25 phr carbon black) increases weathering stability two- and fourfold respectively, as assessed by induction energy and rate of disappearance of unsaturation.     

Rapid assessment of weathering stability from exposure of polymer films. III. Relative weathering stability of ABS and arylon,a related polymer blend

Arylon, a blend of an aromatic polysulfone and a terpolymer of acrylonitrile–butadiene and α-methylstyrene, weathers similarly to ABS. However its first-order rate constant for the loss of unsaturation is only 0.39 cm²(Wh)^?1 as against 0.80cm ²(Wh)^?1 for ABS. This slower weathering is probably caused by the decrease in light intensity penetrating Arylon compared with ABS as a result of the high degree of light scattering observed in the former.     

Natural weathering of polypropylene films. II. Ultimate properties and exposure time

Changes in the ultimate properties brought about by outdoor weathering during the rainy season of polypropylene (PP) films were studied. The results obtained showed that the draw ratio λ_d, tensile stress σ_b, breaking ratio λ_b, breaking factor (BF), work draw U_d, and work for rupture U_r all increased with increase in outdoor exposure time, attaining a maximum at about 240-h exposure time, before decreasing with further increases in exposure time. On the other hand, the draw ratio δ_s remained practically constant up to about 100-h exposure time. The changes in the former set of properties were corroborated by the changes in the apparent crystallinity of the PP samples. In addition, it was shown that a 504-h exposure time was not enough to reduce the properties to damaging levels. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2533–2540, 1998     

Ionic conduction in polymer films: II. Inhomogeneous structure of varnish films

Ionic conduction in polymer films is of two types. Inverse conduction, I, occurs when the resistance runs counter to that of the external solution, and Direct conduction, D, when the resistance follows that of the external solution. The distribution of areas having D properties has been established for films of a pentaerythritol alkyd, a phenol-formaldehyde tung oil and a polyamide-cured expoxide varnish, and it is shown that D conduction cannot be ascribed to capillaries, unless they are of molecular dimensions. It is concluded that these films have a very heterogeneous structure and that I and D areas are brought about by differences in crosslinking density within the film.     

Studies on polymer latex films: II. Effect of surfactants on the water vapour permeability of polymer latex films

Poly(butyl methacrylate) films have been prepared from surfactant-free latices which had post-added commonly used latex stabilisers. Water vapour transmission rates were used to study film permeability in relation to morphology, which was also studied by freeze fracture replication transmission electron microscopy. The extent of latex coalescence depended upon the chemical nature of the stabiliser employed and at monolayer coverage was not necessarily deleterious to the barrier properties of the films.     

Water permeation of polymer films. II. Dual-mode absorption in teflon FEP

DuPont Teflon FEP has been shown to permeate water vapor through a dual-mode process: adsorption followed by permeation. A model is proposed for this process based on the interactions of condensible gas molecules with themselves and with the polymer surface. This model appears to have general applicability.     

Anisotropy of poly(vinyl alcohol) films in the u.v. and i.r. regions of the spectrum

Absorption properties of anisotropic poly(vinyl alcohol) (PVA) films in u.v., Vis, and i.r. spectral regions were investigated. The orientation of the transition moments with respect to the long axis of the chain was determined together with the arrangement of PVA chain. Anisotropic PVA matrices should be considered in terms of binary solvents since together with crystallites, there are regions of amorphous structure.     

Automatic measurement of the absolute CTE of thin polymer samples. II. Effect of chain orientation on thermal expansion of drawn polymer films

More details about the coefficient of thermal expansion (CTE) and thermal expansion anisotropy, Δα, of drawn films from polypropylene (PP) and high density polyethylene (HDPE) are discussed. CTE of the selected polymers are measured along different directions relative to the drawing direction (MD). The coefficient of thermal expansion parallel to drawing direction (α_∥) was less than that in the transverse direction for both of the used polycrystalline polymers. Also α_∥ for PP and HDPE for different draw ratios are measured. The morphology of measured samples is investigated by using an optical polarizing microscope and from the 2D‐plot of the angular distribution of the absorption coefficient of light through a polymer sample between two crossed polarizers. An agreement between obtained figures was found. Birefringence of samples was measured photometrically. The orientation of drawn polymer chains is estimated from the birefringence measurement. The set up of the used optical system is explained. The CTE variations of drawn polycrystalline polymer are explained on bases of the associated morphological variations. A recommendation was given to produce an all‐PP‐composite with satisfactory dimension stability at elevated temperature. Construction and operation of a simple drawing machine is given too. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4452–4460, 2006     

The permeation of gases through modified polymer films. II. Gas permeability and separation characteristics of gamma ray-irradiated polyethylene

A study has been made of the diffusion, solubility, and separation of nitrogen and methane gases in a series of air-and vacuum-irradiated polyethylene films in the temperature range of 15° to 50°C. Samples were air irradiated to 90 Mrads and vacuum irradiated to 80 Mrads. The major structural differences between the modified films were the presence of oxygenated species in the air-irradiated samples. The oxidation of these samples reduced the amount of crosslinking normally found in vacuum-irradiated samples. Diffusion and permeability coefficients for both gases decreased with irradiation dose. The solubility coefficients for the air-irradiated samples increased with increasing irradiation dose while little change was observed for vacuum-irradiated film. The gas mixture permeabilities could be predicted from the pure component permeabilities, and the methane–nitrogen separation factor decreased with increasing irradiation dose.     

The analysis of polyurethane foams II. Chemical constitution of the polymer

Efforts have been made to establish the chemical constitution of water-blown polyurethane foams. Specific reagents have been used to indicate the presence of biuret or allophanate linkages. Partial hydrolysis techniques have been used to degrade foams selectively and hence isolate parts of the chain network. These methods yield information which is not satisfactorily obtained from the examination of undegraded polymer and which is not available after total degradation. It has been shown that polyureatype linkages are present in the chain network of both polyester and polyether foams.     

The significance of thermoanalytical measurements in the assessment of polymer flammability

Thermoanalytical techniques have been widely used for the study of polymer decomposition processes, but they cannot accurately represent the very complex process of polymer combustion. The present work discusses some of the advantages and limitations involved in the use of thermoanalytical measurements to elucidate selected aspects of the constituent processes involved during the combustion of an organic polymer. There is no correlation between the flammability of different organic polymers and their thermal stability, even if the latter property is represented by an improved parameter such as the temperature at which 1% of the polymer has decomposed. An attempt has been made to correlate the inverse of the flammability (as measured by the limiting oxygen index) with the ratio of the heats of combustion and of gasification; but the results are not entirely satisfactory. Thermal analysis can, however, be very useful for the study of the effects of additives on a polymeric substrate. The lower heating rates involved, compared with those associated with a fire, allow determinations to be made not only of the ease of decomposition of an organic polymer but also of the thermochemistry of its reactions, of the effects of different atmospheres and of the extent of volatilization of certain species. In particular, thermoanalytical measurements carried out on a polymer-additive system can aid in the prediction of the effectiveness and mode of action of additives as flame retardants.     

The effectiveness of some commercial emulsifiers in emulsion polymerization II. Anionic types

The initial polymerization rate of ethyl, butyl, and 2-ethylhexyl acrylate was studied in a thermally insulated polymerization reactor. The monomers were continuously added into the reactor and the effect of concentration of anionic emulsifiers on the temperature increase was investigated. Alkyl(aryl)polyethylenglykolethersulfate were found to be most effective in promoting the initial polymerization rate. An inhibition action of some emulsifiers was found.     

Ionic conduction in polymer films: IV. The effect of pigmentation with iron oxide

Ionic conduction in continuous polymer films is of two types. Inverse conduction occurs when the resistance of the film runs counter to, and direct conduction when the resistance follows, that of the external solution. The effect of pigmentation with iron oxide on the type of conduction has been examined in the case of films prepared from a pentaerythritol alkyd, a phenolformaldehyde tung oil and an epoxypolyamide varnish. It was found that upon progressive pigmentation the percentage samples showing direct conduction rose and then fell, furthermore no change in glass transition temperature was observed. It is suggested that this may be due to the segregation of low molecular weight material around the pigment particles thus screening them from the main bulk of the polymer.     

Experimental assessment of the utilization of a novel interpenetrating polymer network in different processes in the agricultural sector

We synthesized a biodegradable, controlled release formulation via the impregnation of methyl methacrylic acid onto the natural polysaccharide, gum tragacanth, and a polyacrlyic-based hydrogel with glutaraldehyde as crosslinker. The biodegradation behavior of the prepared interpenetrating polymer network (IPN) was investigated with soil burial and composting methods, and the biodegradability stages were studied with Fourier transform infrared spectroscopy and scanning electron microscopy analyses. The controlled release data of the calcium nitrate was analyzed in accordance with Fick's power law, and the kinetics parameters of the release process were calculated. The values of the initial and lateral diffusion coefficients indicated a fast initial release rate of the fertilizers in comparison to the lateral release. The synthesized IPN was degraded 91.62% within 11 weeks under composting methods, whereas it degraded 78.83% under the soil burial method. The results show that the synthesized IPN was ecofriendly and could be used for the controlled release of agrochemicals. The impact of the degraded IPN on the fertility of the soil was also studied. We concluded from the results obtained that the biodegraded IPN did not have any adverse effects on the soil fertility. Hence, this biodegradable IPN could be of great significance from a green revolution point of view. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47739.     

Electrodeposition of macroporous silver films from ionic liquids and assessment of these films in the electrocatalytic reduction of nitrate

Macroporous silver films, ordered or fragmented, were fabricated by electrodeposition of silver into the interstitial spaces of templates formed by polystyrene (PS) latex spheres that had been self-assembled onto bare indium tin oxide (ITO) electrodes or onto gold-coated ITO (ITO/Au) electrodes (in which the electrode had been coated by gold sputtering deposition) from two room-temperature ionic liquids (ILs): N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (BMP-TFSI) and N-butyl-N-methylpyrrolidinium dicyanamide (BMP-DCA), respectively, under normal atmospheric conditions. After electrodeposition of silver, the PS spheres were removed by dissolution in tetrahydrofuran (THF) to leave a macroporous silver structure. The higher wettability of ILs onto PS spheres leads to improved penetration of the ILs into the cavities of the PS templates. Electrodeposition is easier if an electrolyte that has a good penetration into the interstitial spaces between the PS spheres. The macroporous silver electrode exhibited much better electrocatalytic performance with respect to nitrate reduction than a regular silver wire electrode. Quantitative determination of nitrate was also examined.     

Studies of polymer electrets. II. Factors governing the stabilities of homoelectrets obtained from polystyrene and its derivatives

Polystyrene and its various alkyl and halo derivatives have been studied as homoelectrets and their stabilities under different environmental conditions determined. The stabilities of the homoelectrets prepared from these polymers depended on their volume resistivities, glass transition temperatures, and interactions with electron-acceptor impurities. Excellent stabilities were exhibited by the homoelectrets prepared from polystyrene, poly(vinyltoluene), poly(chlorostyrene), and poly(t-butylstyrene). It is postulated that the charged particles are trapped by the π-orbitals of the phenyl rings present in these polymers and that they are adversely affected by the presence of electron-acceptor compounds that generally from charge-transfer complexes with the phenyl groups.     

Electrical,thermal, and photo properties of poly(phenylene vinylene) precursors. II. Microwave-induced elimination reactions in precursor polymer films

Microwave radiation (MWR) was used to induce the elimination reaction of the poly(phenylene vinylene)–polyelectrolyte precursors polymer (PPV precursor) into the fully conjugated polymer. The process was applied mainly to the unsubstituted PPV and was followed by infrared spectroscopy. The extent of the elimination process was also determined from the amount of residual sulfur in the film after the irradiation process. The microwave-induced elimination process was also attempted using PPV precursor films that had been impregnated with anionic compounds containing iron. The molecular mechanisms for the observations are discussed and comparison with the elimination reaction induced by other energy sources is also made. © 1994 John Wiley & Sons, Inc.