The effect of solvent traces on the ultraviolet degradation of poly(vinyl chloride)

The ultraviolet degradation of poly(vinyl chloride) films was studied in a photoreactor which supplied energy near 3000 Å. It was noted that the rate of degradation and color development was increased when the level of residual solvent in the cast films was increased. Two solvents were employed in the study: tetrahydrofuran and dichloroethane. The amount of residual solvent was correlated with the height of a characteristic peak at 2800 Å for tetrahydrofuran and 1900 Å for dichloroethane. Films which had very small traces of solvent showed excellent resistance to ultraviolet degradation, even in the absence of ultraviolet stabilizers. The analysis of solubility data showed that chain scission was controlling in the early stages of exposure, while crosslinking was controlling at later stages. As a result, it was not possible to apply Charlesby's treatment of radiation-induced degradation. Comparison with the results obtained by other workers for degradation at 2537 Å showed that degradation at this wavelength was much faster than degradation at 3000 Å. Furthermore, degradation at 2537 Å appeared to be controlled by crosslinking at all stages of exposure.     

Extraction of uranium (VI) by di-(2-ethylhexyl)phosphoric acid gels based on a styrene-divinylbenzene copolymer

Uranium (VI) can be efficiently extracted using hydrophobic gel particles prepared by swelling styrene-divinylbenzene copolymer beads with di-(2-ethylhexyl)phosphoric acid packed into columns. Retained U (VI) can be quantitatively eluted with acid solutions. The effects of incorporating different organic solvents into the gel on its capacity and performance have been investigated. It was found that nitrobenzene gave the best results. The conditions required for the preparation of gels of high capacity have been established.     

The effect of processing conditions on the microstructure of embossed polyethylene films

Film embossing is a mechanical process in which a flat film is transformed into an embossed product. During the process, thermal and stress fields are applied Lo the polymer, causing changes in the microstructure and physical dimensions of the material. The engineering analysis of the process requires the study of various aspects relating to the characterization of the microstructure before and after embossing, A variety of techniques were employed to characterize the properties and microstructure of the embossed film in relation to: crystallinity, orientation, mechanical properties, and dimensions of the embossed films. The thermal treatment of the polymer film was shown to be the most significant factor in the process. By controlling the thermal treatment of the film, it is possible to manipulate the properties and dimensions of the embossed film. The important aspects: influencing thermal treatment include the radiation heater temperature, preheat roll temperature, line velocity, and film thickness. The initial film orientation and embossing pressure have a minor effect on the final properties of the embossed film. The main effect of the embossing pressure is on the bulk thickness of the embossed film.     

Two-port subnetworks of exponential distributed parameter Z-Y-KZ and Y-Z-KY micro-circuits with similar transfer functions

This paper shows that one may find a two-port subnetwork of the exponential distributed parameter (DP) Z-Y-KZ micro-circuit whose open-circuit voltage and short-circuit current ratio-transfer functions are exactly the same as those of another two-port subnetwork of the exponential (DP) Y-Z-KY micro-circuit. There are in total 28 such unique non-redundant two-port subnetworks of the exponential Z-Y-KZ structure which have their counterparts produced by the exponential Y-Z-KY micro-circuit. The results are given in a table. This information is intended to eliminate the duplicacy of time-consuming labour involved in the analyses of these subnetworks obtainable from the exponential Z-Y-KZ and Y-Z-KY structures in view of recent interest in the performance characteristics of such subnetworks.     

PVC membrane potentiometric sensor based on 5-pyridino-2,8-dithia[9](2,9)-1,10-phenanthroline-phane for selective determination of neodymium(III)

Spectrofluorometric studies on the binding properties of 5-pyridino-2,8-dithia[9](2,9)-1,10-phenanthrolinephane (L) toward La3+, Sm3+, Gd3+, Yb3+, and Nd3+ in methanol solution revealed the occurrence of both 1:1 and 2:1 (ligand/metal) complexation with a stability order of Nd3+ > Yb3+ > Gd3+ > Sm3+ > La3+. Consequently, L was used as a suitable neutral ionophore for the preparation of a novel polymeric membrane-selective electrode for Nd3+ ion. The electrode exhibited a Nernstian response over a wide concentration range (1.0 x 10(-6)-1.0 x 10(-2) M) with a low limit of detection of 7.9 x 10(-7) M. The electrode possesses a fast response time of <5 s and can be used for at least 9 weeks without observing any considerable deviation. The proposed electrode revealed a very good selectivity for Nd3+ over a wide variety of alkali, alkaline earth, transition, and heavy metal ions, including members of the lanthanide family other than Nd3+. The potentiometric response of the electrode is independent of the pH of test solution in the pH range 4.0-6.5. The proposed electrode was successfully applied to the recovery of Nd3+ ion from tap water samples and, also, as an indicator electrode, in potentiometric titration of neodymium(III) ions.     

Modeling and analysis of an extrinsic Fabry-Perot interferometer cavity

A schematic representation of optical feedback between two resonator mirrors undergoing a phase shift each round trip as a function of the separation of the mirrors is studied. A transfer function modeling of the extrinsic Fabry-Perot interferometer (EFPI) is presented. Nyquist analysis has been used to forecast the operational stability and possibility of interference in an EFPI. The analysis with two perfectly parallel surfaces of the cavity shows efficient interference. The performance when there is some tilt between the two mirrors in the cavity is also studied and is presented. In this case some restricted interference is found.     

Computer simulation of injection molding

The injection-molding process consists of three consecutive stages: filling, packing, and cooling. In order to obtain some insight into the phenomena involved in the process, and particularly in order to evaluate the moldability of certain resins and to predict the microstructure and properties of products molded therefrom, a number of workers have employed a variety of techniques based on mathematical simulation of the process. Mathematical simulation involves writing the relevant continuity, momentum, and energy equations governing the system, with appropriate boundary and initial conditions representing the prevailing conditions in the cavity and delivery channels. In order to obtain meaningful solutions to the above equations, detailed information is required regarding the thermodynamic, thermal, and rheological properties of the resin. Moreover, the prediction of the microstructure and ultimate properties of the molded article requires a knowledge of the morphological, crystallization, and orientation phenomena that take place under the influence of the thermo-mechanical history experienced by the resin. The complexity of the equations involved results in the utilization of a number of simplifying assumptions and the resort to computer simulation and numerical solutions of these equations. A variety of numerical schemes based on finite difference and finite element methods has been employed by various researchers.     

Kinetics and thermal characterization of thermoset cure

The differential scanning calorimeter (Perkin-Elmer DSC-1) is used to characterize the cure of a general-purpose polyester during isothermal and scanning experiments. The technique is based on a new proposed model for the kinetics of isothermal cure. The model yields results which are in good agreement with experimental isothermal rate of reaction and integral heat of reaction data. It also gives some information about the residual reactivity of the sample after an isothermal cure experiment. With the aid of the proposed kinetic model, it is possible to obtain integral heats of reaction and rates of heat generation at different temperatures during a scanning experiment. The difference between the rate of heat input to the sample and the heat of reaction at any instant during scanning may be used to calculate the specific heat of the sample at the same instant. Specific heat data show two maxima during each scanning experiment. These maxima may be associated with transitions occurring during cure in the melt and rubbery states.     

Kinetics of anodic oxide-film growth on titanium—II. Neutral and alkaline media

Anodic charging curves have been measured on Ti in Na₂SO₄, NaCl, NaNO₃, NaH₂PO₄, Na₂H PO₄, Na₃PO₄ and NaOH solutions in the cd range 5–35 μA/cm². Formation rates are calculated in the region below O₂ evolution. The results indicate the high-field approximation, with linearity between the reciprocal capacitance and log (cd). Data are recorded for the parameters A and B, the field and the activation distance. While B is independent of solution composition, A depends on the nature of anion and the pH. This behaviour is related to the partial dissolution of the oxide films. Use is made of the charge/potential relations to construct the potential/log (cd) curves. These allow estimation of the pre-immersion oxide thickness, giving a result of about 5 Å.