Epoxy-silica polymers as restoration materials. Part II

Room temperature reaction of the epoxy resin poly(bisphenolA-co-epichlorohydrin), glycidyl end-capped with the coupling agent (3-aminopropyl)triethoxysilane, in 1:2 (1), 1:1 (2) and 2:1 (3) molar ratios, leads, after curing for three months at room temperature, to glassy, transparent, crack-free solids which were investigated by SEM, TGA, DSC, NIR and Raman spectroscopy. SEM investigations show substantially a great homogeneity over the entire area with absence of cracks, veins and/or fissures and without formations of clusters and/or aggregates. The conversion of oxirane rings, as found by Raman spectroscopy, decreases by increasing the epoxy/amine ratio, with conversion percentages ranging from 95.3 to 81.3%. As a common feature, the presence in 1, 2 and 3 of Si-O-Si linkages increases the polymer degradation temperature and thermal oxidative stability relative to the parent epoxy resin by shifting the weight loss to higher temperatures. Differently from mixtures 2 and 3, which show the T_g at 90 °C, the mixture 1 does not exhibit any detectable glass transition.     

Capillary rise in porous media. Part II: secondary phenomena

Capillary rise in homogeneous packings of coarse rotund particles shows qualitative differences in behaviour, both with respect to the statics and to the dynamics of capillary rise (see Part I). In this paper it is shown that the differences in behaviour are not due to any of the following parameters or secondary phenomena: the homogeneity of the packing and other pore space properties, phenomena involving the presence of the displaced phase, evaporation, and capillary condensation.     

Studies of relaxation phenomena in polymers. II. The behavior of simple polymers in their main transition region

In an earlier paper, a “new” viscoelastic function, log J₂ = g{log J₁}, was defined. For polymers, the linear viscoelastic behavior of which is characterized by “simple segment movements” in their main transition regions, the following general properties are found: (1) The local maxima of the function for different polymers fall along a straight line width the slope approximately equal to 1.1. (2) A characteristical general shape is noticed for the function after shifting along the straight line and reducing the J₁ compliance as regards the “frozen in” compliance J₁₀. (3) J₁ reflects the storage and J₂, the loss mechanisms of the system. The relation J₂/J₁ is an expression for the average retardation time.     

Studies of macromolecular entanglements. I. Melting behavior of swelling polymers with macromolecular entanglements

In this paper the swelling and melting behavior of several polymers, particularly acrylic fibers, is studied by thermomicroscopy and differential scanning calorimetry in detail. It is confirmed that the protrusion peak on the tail part of the DSC thermogram of swelling polymers is closely associated with the macromolecular entanglements. The proposed swelling DSC method is proved to be very effective for studying polymer entanglements. It is also shown that the melting point, whether of paracrystalline region or of entanglement structural unit, can be well fitted to Flory's melting point depression theory.     

Non-isothermal phenomena in polymer engineering and science: A review. Part II: Non-isothermal phenomena in polymer deformation

Thermal phenomena in deformation of solids and flows are reviewed. Regularities common to all these phenomena as well as their characteristic features and consequences important for science and engineering are reported. The analogy between thermal phenomena in polymer mechanics and in chemical reaction is noted.     

Studies on macromolecular entanglement. II. Modification of macromolecular entanglements by heat treatment

The modifications of macromolecular entanglements in polyacrylonitrile copolymer fibers by heat setting in different mediums such as steam, hot air, and inert liquid are reported. The effects of applied tension, frozen internal stress, temperature, time, medium, crystallization, etc., during heat setting on the modification of entanglements are investigated in detail. These experimental results elucidate clearly the mechanism of entanglement and disentanglement and confirm fully the DSC method of swelling polymers for studying entanglement in solid polymer, as was previously published in Part I of this paper. © 1993 John Wiley & Sons, Inc.     

Studies on the preparation and properties of conductive polymers. Part II. Novel method to prepare metallized plastics from metal chelates of polyamides

New metallized films were obtained by the reduction of polyamide metal chelate films with reducing agents. Polyamide metal chelates films exhibited excellent surface resistivity around 10°–10¹ Ω/cm² when treated with sodium borohydride aqueous solutions. Aqueous solutions of polyamide–formic acid with metal salts, and films prepared from those solutions, were analyzed by UV-visible and IR spectroscopy, respectively, in order to investigate and identify the structure of the polyamide metal chelates. Factors that include kinds and concentrations of metal salts, kinds and concentrations of reducing agents, and reduction time, which may affect the conductivity of metallized films, were investigated. The surfaces of these films were treated with sodium borohydride aqueous solution to form a definite metallic luster appearance. The surfaces of these conductive films were proved to be metallized, by means of ESCA analysis. The strongly adhered metal on the films was believed to be responsible for the improvement in electrical conductivity. The mechanical properties and scanning electron microscope (SEM) observations were also studied.     

End-capped fluoroalkyl-functional silanes. Part II: Modification of polymers and possibility of multifunctional silanes

This work reports the fluoroalkylation of polymer surfaces using novel oligomeric silanes having end-capped fluoroalkyl groups. Polymer surfaces such as cellulose, poly(ethylene terephthalate) (PET), polyethylene, and poly(methyl methacrylate) (PMMA) etc. were effectively modified by these oligomeric silanes as well as the glass surface. From the contact angle measurements, the dispersive and polar components of surface free energies were reduced to 15–20 and 1–3 mJ/m², respectively, and the surfaces were shown to be both highly water- and oil-repellent. Modified cellulose and PET surfaces were analyzed using XPS measurements. In the case of cellulose, a linear correlation was observed between the dispersive component of surface free energy γ_S ^d and the area ratio of the F1s peak to the Si2p peak. In the case of PET, the hickness of siloxane layer on the surface was shown to be less than 8 nm. The modified PET surface showed a high solvent durability against common organic and inorganic solvents except fluorochemicals and alkalis. The structure of the siloxane layer on the modified surface is discussed in terms of a network interphase model. It was also shown to be quite easy to add another function such as hydrophilicity (flip-flop character) and/or antibacterial property in addition to the water- and oil-repellency imparted by fluoroalkyl groups.     

3-D structure-property relationships in rolltruded polymers. Part II: Anisotropic yielding and deformation in triaxially oriented polymers

Rolltrusion, a single step solid state deformation process, has been successfully applied to isotactic poly(propylene), iPP, to produce unique 3-D properties. Mechanical property enhancement not only occurs in the principal draw direction, but also in the transverse directions. A systematic series of standard (ASTM) tensile and compressive experiments were made on well oriented materials supporting this claim. Tensile testing was also performed on dumb-bell shaped specimens cut at various angles to the main deformation direction. A variety of observations were made during testing. Deformation bands, anisotropic yielding, and ductile-to-brittle behavior were observed. These results are presented along with a morphological model that has been developed to account for the behavior of these unique triaxially oriented polymers.     

Epoxy polymers. II. Macrostructure

A variety of measurements indicate that thermosetting epoxy polymers contain closely packed floccules and an interstitial liquid similar to the starting materials. The fioccules are thought to be of colloidal origin and appear to be ordered with respect to each other in a three-dimensional array.     

Modeling of a membrane reactor system for crude palm oil transesterification. Part II: Transport phenomena

The mechanistic modeling of biodiesel production process in membrane reactor with the consideration of chemical reaction, phase equilibrium, and ultrafiltration is important for the membrane reactor design. In part II of this work, the chemical and phase equilibrium (CPE) model for crude palm oil transesterification reaction in the membrane reactor developed in part I is extended to an integration of CPE with modified Maxwell–Stefan model, which considers multicomponent mass transport phenomena of concentration polarization and intramembrane. A good fit of simulated permeate fluxes and apparent solute rejection to the experimental data shows that the model has a good prediction capability. Reversible fouling was found to be the major fouling and no pore plugging was observed. Simulation results verified that micelles were retained by the membrane at CPO:MEOH molar ratio of 1:24 and catalyst concentration of 0.5 wt %. However, phase inversion happened when catalyst concentration of 0.05 and 0.1 wt % were used. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1981–1996, 2015     

Swelling of hydrophilic polymers. II

The swelling of five types of Sephadex that are either nonionic (G) or possess one of four different ionic groups [sodium carboxymethyl (CM), sodium sulfopropyl (SP), diethyl-aminoethyl chloride (DEAE), diethyl - (2-hydroxypropyl) aminoethyl chloride (QAE)] in the same skeleton of the molecule has been studied by picture analysis and by calorimetry. Inducing dissociation of the ionic group in the polymer skeleton increased the water swelling. By the addition of sodium chloride, the maximum swelling volume of nonionic Sephadex was only slightly decreased. However, that of ionic polymers was considerably decreased. The variation of the apparent first-order rate constant of the swelling and that of the maximum swelling volume show the same tendency. The maximum heats of swelling were 93.2 ± 7.1 J g^?1 for G, 128.8 ± 9.1 J g^?1 for CM, 92.3 ± 8.0 J g^?1 for SP, 68.8 ± 10.5 J g^?1 for DEAE, and 67.0 ± 7.2 J g^?1 for QAE and did not depend on the concentration of sodium chloride. From the results obtained, we conclude that the nonionic Sephadex swells only by hydration but that ionic Sephadexes swell mainly by the osmotic pressure due to the counterions of the ionic groups and that the swelling ratio is not dependent on the kinds of ions but on the ionic concentration. Most of the water in the gels of ionic Sephadexes is free water that does not interact with the Sephadexes. © 1993 John Wiley & Sons, Inc.     

Guar gum methyl ethers. Part I. Synthesis and macromolecular characterization

Guar gum (GG) has been partially methyl-etherified under heterogeneous reaction conditions. The resulting products, (methyl ether guar: MG) with different degrees of substitution, have been characterized by means of viscosity, ¹H NMR, and FTIR measurements. The introduction of methoxyl groups along the polysaccharidic chains reduces the hydrogen bonding sites on the guar backbone reducing primarely the extent of hydrogen bonding between guar macromolecules, hence their aggregation tendency. A comparative analysis of Mark–Houwink–Sakurada parameters and of the characteristic ratio (C_∞) of GG and MG samples in aqueous solution has been carried out using the Burchard–Stockmayer–Fixman method for flexible and semiflexible chains. The MG chains exhibit more flexibility than those of native guar gum which is traceable to a disruption of intrachain hydrogen bonds.     

On some rheological phenomena of amorphous polymers

The molecular domain model for flexible macromolecules is presented in brief, and various observations are enumerated, indicating that the model holds true for the solid, melt, and solutions of different concentrations. The four forms in which the domains can exist under shear stress are then presented, and, by referring to them, such rheological phenomena as “die swell,” sudden jumps in flow rate, critical concentrations, and changes in viscosity are qualitatively explained.     

Organometallic polymers. II. Crosslinking of ferrocenylene–methylene-type polymers

Poly(ferrocenylene-methylmethylene) (PFMM) was prepared and subsequently crosslinked by the aid of either 1,1'-bis(α-hydroxyethyl)ferrocene or polyfunctional ferrocene polymers, containing reactive-CH₂OH or-CH(CH₃)OH groups. The thermal behavior of both the primary polymer and the thermoset was investigated. The solubility parameter of PFMM was determined and the degree of crosslinking was studied by solvent swelling and sol fraction measurements. Various thermosetting structural composites were prepared and subjected to mechanical testing.     

Thermodynamic description of relaxation phenomena in polymers

The analysis of various deformations of an ordinary elastic body and a highly elastic body accompanied by temperature changes shows that, in distinction to isothermic conditions, under adiabatic conditions the dynamic characteristics of a polymer in a highly elastic state depend on the amplitude of the applied stress (in particular, their position on a frequency or temperature scale), which is associated with the entropic nature of the highly elastic deformation. When describing the relaxation phenomena caused by the response of the system of interacting kinetic units to the external perturbation, the nonequilibrium thermodynamics relationship between the “flow” and the “generalized force” is nonlinear even at small deviations from the equilibrium state. In this case the dependency of the kinetic factor on the response can be presented by eq. (40). Considered herein were such particular relaxation phenomena as creep and stress relaxation. The calculated dependencies agree well with the experimental data.     

Transverse orientation dies for solid-state extrusion of polymers. Part II: Orientation and properties of extrudates

Biaxial orientation in polymer products is normally brought about by the application of planar tensile stresses to sheets or films in either the “plastic” or “rubbery” state. More recently, other techniques have been explored as, for instance, the superimposition of rotational components in planes perpendicular to compressive forces. The present work is concerned with the solid-state extrusion of very high molecular mass crystalline polymers, such as poly(tetra)fluoroethylene (PTFE) and ultrahigh-molecular-weight polyethylene (UHMWPE), using dies featuring converging and diverging walls perpendicular, to each other and with a cross-section area at the entry being the same as at the exit. Measurements of birefringence and tensile strength on solid section extrudates have shown that dies with small converging angles, known as fish tail dies, produce a uniaxial type of orientation along the transverse direction, while dies with large converging angles at the entry region give rise to an unbalanced biaxial orientation.     

Interpenetrating polymer network approach to tough and microcracking resistant high temperature polymers. Part II. LaRC-RP41

Recently, we reported on the interpenetrating polyimide network (IPN) approach to develop tough and microcracking resistant high temperature matrix resins for use in aircraft/aerospace structural components. One such polymer developed is designated LaRC-RP40. This new simultaneous semi-IPN was prepared from easy-to-process but brittle crosslinking PMR-15 and tough but difficult-to-process linear NR-150B2. Significantly improved toughness, microcracking resistance, and glass transition temperature over PMR-15 were realized from the combination. These property improvements were achieved without compromising ease of processing, high temperature mechanical performance, and cost effectiveness compared to PMR-15. These results encouraged us to further explore this approach for the development of a wider range of polymers of basic technological and economic interest. In the present work, we combine crosslinking PMR-15 and linear LaRC-TPI to provide a new sequential semi-2-IPN called LaRC-RP41. The physical and mechanical properties of the neat resin and composite reinforced with graphite fibers are presented. The phase morphology and phase stability of the neat resin and composite studied by various techniques are also discussed.     

Study of pyridinium-type functional polymers. II. Antibacterial activity of soluble pyridinium-type polymers

The antibacterial activity of a series of soluble pyridinium-type polymers with different compositions against Escherichia coli (E. coli) suspended in sterilized distilled water was investigated by a colony count method. The results show that the antibacterial activity of the soluble pyridinium-type polymers is characterized by their activity to kill bacterial cells and this activity can be enhanced as the content of the pyridinium group (C_q) in the polymers increases. The species of the bacteria has a great influence upon the antibacterial activity of the soluble pyridinium-type polymers. The polymers possess a strong ability to kill Gram-positive and Gram-negative bacteria, and yeasts, excepting Bacillus subtilis, having gemmae and fungi. The toxicity of this kind of polymer has also been appraised. In the acute stimulation and allergy experiments, the red maculae, edema, and abnormal phenomena of an allergy on the skin of the tested animals were not observed. The acute toxicity experiment shows that the LD₅₀ of the polymer is 2330 mg/kg, implying that this kind of polymer has only very weak toxicity. This is significant for the application of soluble pyridinium-type polymers. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 67:1761–1768, 1998