Co-acrylic Acid Research Articles

Miscibility of poly(styrene- co-acrylic acid) with polymethacrylates or poly(methacrylate- co-4-vinylpyridine)

The miscibility of poly(styrene- co-acrylic acid) with polymethacrylates or poly(methacrylate- co-4-vinylpyridine) was studied by differential scanning calorimetry and inverse gas chromatography using decane, octane and benzene as molecular probes. The results showed that poly(isobutyl methacrylate) is immiscible with styrene-acrylic acid copolymers of different acrylic acid content as evidenced from the appearance of two glass transition temperatures determined with both techniques. Positive values of the apparent polymer-polymer interaction parameter χ 23 (app.) obtained with all probes in the temperature range 160–180 °C over the entire blend composition confirm the immiscibility of these blends. Blends of the former styrene-acrylic acid copolymers are, however, miscible in all proportions with poly(ethyl methacrylate), poly(ethyl methacrylate- co-4-vinylpyridine) and poly(isobutyl methacrylate- co-4-vinylpyridine). A single composition dependent-glass transition temperature and negative values of χ 23 (app.) were obtained with these blends

Effect of interleaving on the impact response of a unidirectional carbon/epoxy composite

Instrumented drop-weight impact response of a unidirectional carbon/epoxy composite and that of the corresponding laminate interleaved with poly(ethylene- co-acrylic acid) at the midplane were studied. The impact penetration energy of the unidirectional composite beam increased strongly upon interleaving. Realtime observations using a microscope in a static flexure test indicated a dramatic change of failure mode from the dominantly compressive fracture of the baseline laminate to the dominantly tensile fracture process upon interleaving, in accordance with the corresponding fractographic features of the impact specimens. These observations were attributed to the change in stress distribution upon introduction of the interleaf layer. The relevance of the present observations to the role of high-strain, low-modulus adhesive layers in the toughening of composites is discussed.

Dehydration of water-pyridine mixture through poly(acrylonitrile- co-acryclic acid) membrane by pervaporation

An aqueous pyridine solution was dehydrated by using modified polyacrylonitrile membranes to form in situ complexes with the solute in the feed solution. The pervaporation separation of a water-pyridine mixture using poly(acrylonitrile- co-acrylic acid) membranes exhibited a separation factor ranging from 13.4 to 2207 and a flux of 45–610 g/m 2 h depending on the operating temperature and the concentration of the feed mixture. The permeation mechanism through the membrane is explained on the basis of the molecular interaction between the permeants and the membrane.

Thermal analysis of blends of poly(ethylene co-acrylic acid) (PEA) and epoxidised natural rubber (ENR)

The decomposition behavior of blends of poly(ethylene co-acrylic acid) (PEA) and epoxidised natural rubber (ENR) have been studied by thermogravimetric (TG) and (first) derivative thermogravimetric analysis. The thermograms of ENR show a clear two-stage degradation, whereas that of PEA exhibits three-stage degradation. Surprisingly, in the blends containing 70 and 50% of ENR, multistage degradation is observed, whereas blends containing 30, 20 and 10% ENR exhibit two-stage decomposition with a T 1max (first maximum decomposition temperature) at 430 °C. This higher T 1max in the latter blends indicates the existence of a single phase, owing to strong chemical interactions during melt processing. Activation energy at 10% degradation and half life at 200 °C of the blends have been reported.

Basic functionalization of polypropylene and the role of interfacial chemical bonding in its toughening

A reactive polypropylene (PP) containing oxazoline functional groups was prepared by the melt grafting of 2-iso-propenyl-2-oxazoline onto a PP homopolymer and used to introduce varying amounts of interfacial chemical reaction in PP/acrylonitrile- co-butadiene- co-acrylic acid rubber (NBR) blends. A technique has been successfully developed to control the rubber particle sizes of PP/NBR blends such that various PP/NBR blends with the same rubber particle size can be obtained by using different combinations of processing conditions and the amount of interfacial reaction. It has been found that moderate levels of interfacial chemical bonding are required for a transition from a brittle to ductile failure to be observed in PP/NBR blends. Blends without any interfacial chemical bonding showed no improvement in impact energy whereas up to a 13.5-fold improvement in impact energy (notched Charpy test) was observed for reactive blends above the brittle-tough transitions.

Association behavior in copolymer blend membranes and the pervaporation of water/ethanol mixtures

The nature of the interaction in the blend of poly(acrylonitrile- co-acrylic acid) and poly(acrylonitrile- co-vinyl pyridine) has been proven to be an ionic interaction between the carboxylic acid and the pyridyl group, which provides the blend membrane with an ionic character. The blends were found to form more selective membranes than either of the copolymers in an pervaporation process. Total flux and selectivity of these membranes increased with an increase in the ionic character of the blends. Ethanol flux increased with temperature while water flux remained nearly unchanged, indicating that the transport mechanisms of the two permeants are quite different.

Functional polymers for colloidal applications. VII. Aggregate formation of lipophile-modified polyacrylates in aqueous solutions

AbstractWater‐soluble copolymers, poly(dodecyl acrylate–coacrylic acid) (PDA), are synthesized by copolymerizing different ratios of dodecyl–acrylate/acrylic acid. Their aqueous solutions are transparent. The plots of I1/I3 (the intensity ratio of pyrene emission at 374 nm and 385 nm) and of surface tension as a function of polymer concentrations are combined to verify the existence of the aggregates of PDAs. It is found that the aggregations begin to form at concentrations below that of the polymer transfer to the air–water interface. The plots of I1/I3 as a function of polymer concentration shows that the polymers with a higher ratio of dodecyl acrylate form polymer aggregates at lower concentrations. The hydrophobicity of the inner core of polymer aggregates is close to that of sodium dodecyl sulfate (SDS). Polymer solutions of PDA 30, PDA 30L, and PDA 15, show significant solubilization ability to pyrene. (The molar ratio of dodecyl acrylate/total acrylates is 30%, 30%, and 15% for PDA 30, PDA 30L, and PDA 15, respectively. L, low molecular weight.) The solubilization ability increases with the increase in polymer concentration and degree of substitution of dodecylamine. The intensity ratio of the excimer emission to monomer emission of pyrene (Ie/Im) increases with increasing polymer concentration, roughly parallel to the increase in the amount of pyrene solubilized. However, the Ie/Im at a fixed pyrene concentration (Ie/I) decreases with increasing polymer concentration. These phenomena are interpreted in terms of the amount of pyrene solubilized and the size and concentration of the polymer aggregates. © 1993 John Wiley & Sons, Inc.

Contact angle of organic liquids on poly(2-ethylhexyl acrylate- co-acrylic acid)

The contact angles of poly(2-ethylhexyl acrylate- co-acrylic acid) (P(2EHA-AA)) with organic liquids, such as dispersion, polar and hydrogen bonding liquids, were investigated. The contact angle ϑ of organic liquids on P(2EHA-AA) decreased exponentially with contact time t, i.e. log ϑ = − K log t. It was suggested that the proportional constant K was influenced by the liquid's surface tension γ L, viscosity and glass transition temperature of P (2EHA-AA).

Investigation of hydrogel water in polyelectrolyte gels using differential scanning calorimetry

Characterization of the water structure in hydrogels is of the utmost importance in understanding their dynamic and equilibrium swelling behaviour as well as in analysing solute transport and other diffusive properties of such systems. Polymer-water interactions coupled with the physical property changes of the water associated with the hydrogel structure can determine the permeability characteristics of solutes through these hydrogels. The water structures inside ionic copolymeric networks of poly(2-hydroxyethyl methacrylate- co-methacrylic acid) and poly(2-hydroxyethyl methacrylate- co-acrylic acid) were investigated as a function of the pH and ionic strength of the swelling medium and the type of counterion in the swelling medium using differential scanning calorimetry. The free water content increased with an increase in pH and a decrease in ionic strength. The bound water content was found to be independent of the pH of the external swelling medium. The Donnan ionization equilibrium concept was used to explain the observed trends. This study is useful in correlating the hydrogel water structure with solute diffusion through these hydrogels.

The kinetics of particle and polymer adsorption by total internal reflection fluorescence

A spectrofluorimeter has been adapted to produce and analyse total internal reflection phenomena at solid—liquid interfaces. The induced evanescent wave is used to excite fluorescent species at the surface, and a specially constructed flow cell enables interfacial processes to be followed under well-defined hydrodynamic conditions. The adsorption of aqueous dispersions of cationic polystyrene latex particles and the amphoteric poly(dimethyldiallylammonium chloride co-acrylic acid) onto a flat quartz surface has been studied as a function of time. For particle adsorption the data fit a single-exponential equation which is interpreted in terms of the rate of mass transfer to the surface. Polymer adsorption is more complex and the data fit a double-exponential rate equation at low bulk concentrations. At higher polymer concentrations an early-time maximum is observed, which is explained in terms of the relative rates of mass transfer to the surface and configurational rearrangement of adsorbed molecules.

Complexes between starch and poly(ethylene- co-acrylic acid) — viscosity and gel rheology of jet-cooked dispersions

Starch-poly(ethylene- co-acrylic acid) (EAA) complexes were prepared by jet-cooking cornstarch, waxy cornstarch, high amylose cornstarch (Amylomaize VII), wheat starch and potato starch in the presence of an aqueous ammonia solution of EAA. Much of the excess ammonia is volatilized during jet-cooking, and cooked dispersions had pH values of about 9, depending on the amount of EAA solution used relative to starch. Viscosities were continuously measured as dispersions were cooled from 90 to 22°C. Addition of as little as 0·5% EAA based on starch significantly increased the viscosity of a cooked starch dispersion, and viscosities increased with the amount of EAA added. The maximum viscosity and the shape of the viscosity versus time/temperature curve varied with the particular starch variety used. Hot starch-EAA dispersions were poured into molds to allow the formation of gels on cooling. Gel rigidity was measured by subjecting these gels to uniaxial compression in an Instron testing machine. The ability to form a gel depended on the starch variety used, but more importantly on the presence of EAA and the starch-EAA ratio. The most rigid gel tested was prepared from 5% Amylomaize VII (amylose content 70%) without EAA. Addition of 5% EAA based on starch softened the gel, indicating interference of EAA with amylose retrogradation during gelation. Contrary to these results, cornstarch (containing about 30% amylose) gave a firm gel at 5% solids when cooked with 5% EAA (based on starch), whereas gels too soft for testing were obtained with EAA levels less than 5%. With waxy cornstarch and potato starch, which do not form gels by themselves, EAA levels of 10% (based on starch) were required to obtain gels rigid enough to test. Addition of EAA may, therefore, either increase or decrease gel rigidity depending upon how readily a particular starch will form a gel by itself (through amylose retrogradation) in the absence of additives. Apparent cross-link densities were also calculated from compressional data.

Complexing between starch and poly (ethylene- co-acrylic acid)—a comparison of starch varieties and complexing conditions

We have prepared starch-EAA complexes from different varieties of starch under a number of different reaction conditions. Water dispersions of starch at either 1 or 5% solids were combined with solutions of EAA in aqueous ammonia. Mixtures were air-dried, and the resulting composite films were then extracted with a solution of 1,1,2-trichloroethane, isopropanol, and toluene (15:15:70, by volume) to remove uncomplexed EAA. EAA content of composites after extraction was determined by FTIR. Because of its inability to form helical inclusion complexes with EAA, the microbial polysaccharide dextran was used to establish extraction conditions. Pretreatment of polysaccharide-EAA composites with methanol-water prior to extraction was essential for efficient removal of uncomplexed EAA. It was also necessary that methanol-water solutions be acidified to convert any residual ammonium carboxylate in the composite to carboxylic acid. The amount of EAA complexed by starch increased with an increase in the temperature used for gelatinization and also with the amylose content of the starch sample. Jet-cooked starch samples afforded the highest levels of complexation. Complex formation with cornstarch was not enhanced by the removal of trace amounts of lipid. Increased complexing of EAA was observed if composites were prepared at 1% as opposed to 5% solids. Under these conditions, complex formation with potato starch was about the same as that observed with cornstarch, indicating that phosphate substituents in potato starch do not influence complexing ability.

Analysis of polysaccharide-poly(ethylene- co-acrylic acid) composites by fourier-transform infrared spectroscopy

A method, based on absorbances in FTIR spectra of the CO singlebond stretch band of the polysaccharide and the CH stretch band of poly(ethylene- co-acrylic acid) (EAA) at 2851 cm −1, was developed for the determination of EAA in composites with either dextran or starch. Spectral subtraction of the polysaccharide component was necessary for quantitative determination of EAA. The accuracy of this analytical procedure is affected by the fact that absorbances of these two bands are not equally dependent on particle size of the sample in the KBr pellet; the absorbance ratio, as calculated from FTIR spectra therefore varies with sample preparation conditions. To ensure the necessary particle size uniformity during the preparation of KBr pellets, a method based on relative intensities of two bands in the CO region of the spectrum was developed as an indicator of particle size in the pellet. This method was also used for monitoring sample size in the polysaccharide standard used for spectral subtraction, since particle size uniformity between sample and polysaccharide standard was also necessary for accurate determination of EAA.

Novel two-phase polymer system

Blends of an acrylate or a related copolymer, containing a small proportion of acidic groups, with a homopolymer or a copolymer of an N-vinyl lactam were found to exhibit compatibility on an optical scale and a phase-separated microstructure. Infra-red spectroscopic studies of blends of poly(vinyl acetate- co- N-vinyl 2-pyrrolidone) with poly(2-ethylhexyl acrylate- co-acrylic acid) revealed hydrogen bond formation between the pyrrolidone carbonyl groups and the acidic hydrogens. These interpolymer interactions seemed to be the cause of the apparent compatibility of the polymer blends. The existence of microphase separation in the blend was confirmed by transmission electron microscopy. Further manifestation of the two-phase morphology of the blends of this system was obtained in their physical properties, such as stress—strain behaviour of the elastomeric polymer blends and swelling characteristics of the hydrophilic polymer blends.