Inverse gas chromatography for determining the dispersive surface free energy and acid–base interactions of sheet molding compound—Part II 14 Ligno‐cellulosic fiber types for possible composite reinforcement

Composites reinforced with natural plant fibers are currently actively researched. Inverse gas chromatography (IGC) is a technique that is used to characterize the surface energy and polar characteristics of materials. The theoretical approaches used with IGC are reviewed and applied to the study of 14 ligno‐cellulosic fiber types including grass fibers, bast fibers, leaf fibers, seed fibers, and fruit fibers. This was done to provide insight into the impact of fiber composition on the surface characteristics of the different fiber types and explore possible correlations among the data. The dispersive surface energy, and K_a, K_b constants are reported for the 14 fiber types and compared with values reported in the literature. The dispersive energies ranged from 35.5 mJ/m² to 44.2 mJ/m² at 20°C with K_a from 0.01 to 0.38 and K_b from 0 to 1.05. A correlation was found at 40°C for surface energy related to fiber composition and fiber type where the surface energy decreases with increasing lignin and hemicellulose composition but increased with increasing cellulose concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Determination of the acid–base characteristics of lignocellulosic surfaces by inverse gas chromatography

The surface acid–base characteristics of samples of cellulose, pine wood, and kenaf powder were determined by inverse gas chromatography (IGC). The test substrates were packed in a deactivated glass column and the IGC probes were injected at infinite dilution. The surface acid–base parameters were expressed in terms of the acceptor K_A and donor K_D parameters, analogous to the Gutmann acceptor and donor numbers derived from the Lewis concept of acids and bases. The K_A and K_D values were calculated from the experimental values of the enthalpy of desorption, corresponding to the specific acid–base interactions, and literature values of the acceptor and donor numbers for the acid–base probes, chloroform, carbon tetrachloride, ethyl acetate, and diethyl ether. Values of K_A and K_D suggest that the surfaces of cellulose, pine wood, and kenaf powder that have been washed by extraction with toluene/ethanol (2 : 1, v/v) are amphoteric, with a relatively greater capacity to accept electrons. The effect of the washing procedure on the dispersive component of the surface energy of the pine wood and kenaf powder was also determined. It was observed that the values for the washed substrates were relatively greater than those of the nonwashed counterparts. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1013–1020, 1997     

Estimation of the dispersive component of surface energy of polymer-grafted lignocellulosic fibers with inverse gas chromatography

Surface energy has traditionally been obtained through contact angle measurements. Hygroscopic, chemically heterogeneous and short fibers, such as wood fibers, may present difficulties in obtaining meaningful results. Inverse gas chromatography (IGC) is an alternative technique which can circumvent this problem. Indeed, IGC is particularly well-suited to measurements with porous, short fiber substrates, and data can be acquired as a function of composition or temperature. Measurements are generally done with a solvent, called 'probe', at near infinite dilution in an inert carrier gas. Little solvent-solvent interaction is involved, which is different from classical wetting measurements. A comparison is made between dispersive components of the surface energy as obtained through contact angle analysis and IGC. The variation of the dispersive component of the surface energy of wood fibers grafted with poly(methyl methacrylate), as a function of the degree of grafting, as obtained with IGC is presented and compared with results of photoelectron spectroscopy and specific surface measurements.     

Lewis acid–base property of P(VDF‐co‐HFP) measured by inverse gas chromatography

Poly (vinylidene fluoride‐co‐hexafluoropropylene) P(VDF‐co‐HFP) is an excellent material for polymer electrolytes of lithium ion battery. To enhance the lithium ion transference number, some metal oxides were often embedded into P(VDF‐co‐HFP). The promising mechanism for the increase in lithium ionic conductivity was Lewis acid‐base theory. In this experiment, the Lewis acid–base properties of P(VDF‐co‐HFP) were measured by inverse gas chromatography (IGC). The Lewis acid constant K_a of P(VDF‐co‐HFP) is 0.254, and the base constant K_b is 1.199. Compared with other polymers characterized by IGC, P(VDF‐co‐HFP) is the strongest Lewis basic polymers. Except aluminum ion, lithium ion is the strongest Lewis acidic ion according to their η value of Lewis acids. Therefore, a strong Lewis acid–base interaction will exist between lithium ion and P(VDF‐co‐HFP). This will restrict the transference of lithium ion in P(VDF‐co‐HFP). To enhance the lithium ion transference by blending other metal ions into P(VDF‐co‐HFP), it is suggested that the preferential ions should be Al³⁺, Mg²⁺, Na⁺, and Ca²⁺ because these metal ions have relative large η values. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Acrylic pressure‐sensitive adhesives with nanodiamonds and acid–base dependence of the pressure‐sensitive adhesive properties

A high performance and functional properties in pressure‐sensitive adhesives (PSAs) are attractive in fundamental and industrial fields. To control the performance of PSAs, nanofillers have been loaded into them. In this study, we focused on composites of acrylic PSAs and nanodiamonds (NDs). The loaded NDs reinforced the mechanical properties and increased the performance of the PSAs. NDs in a PSA formed a network structure. In this study, we revealed that the acidic–basic state was a key factor in the control of the dispersion of the NDs. When a PSA emulsions and ND aqueous dispersion was mixed under basic conditions, the composites demonstrated higher PSA properties (tack, holding, and peeling strength). We investigated the effect of the ND loading on the PSA properties from the viewpoints of the nanostructure and acid–base interactions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46349.     

Plasma‐graft polymerization of a monomer with double bonds onto the surface of carbon fiber and its adhesion to a vinyl ester resin

Double bonds reactive with active radical species were introduced onto the surface of carbon yarn by the plasma‐graft polymerization of adipic acid divinyl ester and ethylene glycol dimethacrylate monomers to increase the adhesive strength in the interface between the carbon yarn and a vinyl ester resin. The degree of grafting increased with increasing polymerization time and polymerization temperature. The degree of grafting depended on both the solvent and the monomer species used in the polymerization, and a high degree was obtained with ethylene glycol dimethacrylate as the conjugated monomer and in a mixture of methyl isobutyrate and water. The grafted yarn, whose surface layer contained double bonds, was reacted with a vinyl ester resin containing benzoyl peroxide and N,N‐dimethylaniline. The pull‐out force of the yarn embedded in the resin increased with increasing degree of grafting. The failure in pulling out the yarn was cohesive. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2415–2419, 2003     

Three‐dimensionally braided carbon fiber–epoxy composites,a new type of material for osteosynthesis devices. I. Mechanical properties and moisture absorption behavior

In recent years, three‐dimensionally (3D) braided composites have attracted a great deal of attention because of their high‐impact damage tolerance and fatigue life, superior fracture toughness, and so forth, and have been used in aeronautics, military, and transportation. These advantages make them strong candidates for osteosynthesis devices. In this study, 3D braided carbon fiber–epoxy (C_3D/EP) composites were produced via a simple vacuum impregnation technique. The load‐deflection curve, mechanical properties, and influence of fiber volume fraction, braiding angle, and axial reinforcing fibers were examined to determine their suitability for internal fixation devices. It is found that the C_3D/EP composites have excellent toughness and do not show brittleness when fractured because of their relatively high void content. The flexural, shear, and impact strengths of the C_3D/EP composites are excellent. It was shown that a C_3D/EP composite with a stiffness similar to load‐bearing bones can be made while maintaining enough strength. It is concluded that a relatively higher void content and braiding angle is more suitable for the C_3D/EP composites from the viewpoint of requirements of fracture fixation materials. The moisture absorption behavior and changes in mechanical properties caused by moisture uptake were evaluated. Results show that absorbed moisture slightly decreases mechanical properties of the C_3D/EP composites. Contrary to the unreinforced epoxy, the moisture absorption behavior of the C_3D/EP composites cannot be described with Fick's law of diffusion, probably because of the presence of voids and/or 3D fiber structure. The exact mechanisms should be proposed in further investigations. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1031–1039, 2002     

Simple chemical polymerization method for the deposition of a conducting polyaniline on the surface of acrylonitrile–butadiene–styrene. II. Treatment in organic free solvent

We developed a simple method for the deposition of a uniform layer of polyaniline (PANI) on the surface of acrylonitrile–butadiene–styrene (ABS). The method consisted of two steps: the soaking of ABS samples in a water‐based aniline solution stabilized by surfactants followed by the oxidative polymerization of the adsorbed and absorbed monomer. The three types of surfactants (molecular N,N‐dimethyl‐octalamine‐N‐oxide, anionic sodium dodecyl sulfate, and cationic hexadecyl trimethyl ammonium bromide) were used to prepare and stabilize the aniline emulsions in water. After treatment, the ABS surface was completely covered by PANI (as seen with scanning electron microscopy). The surface conductivity after PANI coating reached values between 10^?3 and 10^?4 S/□ in the best developed conditions. The chemical nature of the surfactant affected the particular setting of the aniline/surfactant emulsion preparation (time of ultrasonification = 15–30 min), its optimal concentration (2–10 wt % aniline and 0.1–0.2M surfactant), and other parameters of treatment, such as time (10 s to 20 min) and temperature (20–60°C) of soaking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1752–1758, 2004     

Organic–inorganic hybrid material. I. Synthesis,characterization, and thermal property of a novel polyhedral cubic silsesquioxane

Hydrosilylation of 2‐chloroethylvinyl ether by octahydridosilsesilsesquioxane catalyzed by hexachloroplatinic acid was carried out to afford a quantitative yield of 3 in its white crystals. Thermogravimetric analysis of Si₈O₁₂(CH₂CH₂OCH₂CH₂Cl)₈ 3 revealed that it is reasonably thermally stable. Spectroscopic data and crystal structure were used to justify the integrity, structural and molecular connectivity of the hitherto novel compound. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 907–910, 2004     

Headspace solid‐phase microextraction with gas chromatography/mass spectrometry reveals a correlation between the degradation product pattern and changes in the mechanical properties during the thermooxidation of in‐plant recycled polyamide 6,6

The increased susceptibility of in‐plant recycled polyamide 6,6 toward thermooxidation was shown by headspace solid‐phase microextraction with gas chromatography/mass spectrometry (HS‐SPME/GC‐MS), tensile testing, differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). A correlation between the deterioration in mechanical properties and the formation of degradation products due to thermooxidation was found, and the most prominent decrease in mechanical properties coincided with the largest increase in the abundance of degradation products. The recycled materials had a shorter induction period toward oxidation, and their mechanical properties deteriorated faster than the mechanical properties of virgin material. The same trend was observed with HS‐SPME/GC‐MS because degradation products were found for recycled materials after oxidation times shorter than those for virgin material. Furthermore, larger amounts of degradation products were formed in the recycled materials. The high sensitivity of HS‐SPME/GC‐MS as an analytical tool was demonstrated because it was able to detect changes caused by oxidation considerably earlier than the other methods. Unlike DSC and FTIR, it could also show differences between samples recycled for different times. Four groups of degradation products—cyclic imides, pyridines, chain fragments, and cyclopentanones—were identified in thermooxidized polyamide 6,6. After 1200 h of thermooxidation, 1‐pentyl‐2,5‐pyrrolidinedione was the most abundant degradation product. Approximately four times more 1‐pentyl‐2,5‐pyrrolidinedione was formed in polyamide recycled three times than in virgin polyamide. Pyridines and chain fragments behaved toward oxidation and repeated processing like cyclic imides; that is, their amounts increased during oxidation, and larger amounts were formed in recycled materials than in virgin material. The cyclopentanone derivatives were present already in unaged material, and their amounts decreased during oxidation. Cyclopentanones were not formed because of the thermooxidation of polyamide 6,6. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3396–3407, 2002     

Preparation and properties of emulsifier/N‐methylpyrrolidone‐free crosslinkable waterborne polyurethane–acrylate emulsions for footwear adhesives. I. Effect of the acrylic monomer content

Stable emulsions of emulsifier/N‐methylpyrrolidone‐free crosslinkable waterborne polyurethane–acrylates (C‐WBPUAs) with various acrylic monomer contents (0, 10, 20, and 30 wt %) for footwear adhesive materials were successfully prepared in this study. The effects of the acrylic monomer content on the shelf stability, mean particle size, and viscosity of the C‐WBPUA emulsions; the tensile properties and dynamic mechanical thermal properties of the C‐WBPUA film samples; and the adhesive strengths between the upper (synthetic leather) and the sole (ethylene vinyl acetate rubber) in both the dry and wet states of the formulated adhesives (C‐WBPUA emulsion–thickener–hardener) were examined. The adhesive strengths of the formulated adhesives for footwear (leather–sole) in both the dry and wet states increased with increasing acrylic monomer content up to 20 wt %; after this, they almost levelled off. Thus, C‐WBPUA20 and C‐WBPUA30, where the number indicates the acrylic monomer content, can be recommended as high‐performance adhesive materials for footwear. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43758.     

Synthesis and characterization of styrene–divinylbenzene loaded with di(2-ethylhexyl)phosphonic acid. I. Influence of diluent mixture on the porous structure of the copolymer

Styrene–divinylbenzene copolymers were synthesized in the presence of di(2-ethylhexyl)phosphonic acid (EHEHPA) to be applied in the separation of rare earths by extraction chromatography. The copolymers were prepared by suspension polymerization in the presence of pure EHEHPA or in a mixture with isooctane, heptane, or toluene. The composition of the diluent mixture employed in the synthesis was varied. The apparent density, fixed pore volume, and surface area of the copolymers were determined. The content of EHEHPA retained in the copolymer beads was also determined, and it was found to be independent of the porous structure of the copolymer matrix. That content was only dependent on the amount of EHEHPA present in the diluent mixture. The toluene/EHEHPA mixtures produced the copolymers with the best properties required for extraction chromatography supports. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:781–787, 1998     

Effect of adhesive‐coated glass fiber in natural rubber (NR), acrylonitrile rubber (NBR), and ethylene–propylene–diene rubber (EPDM) formulations. I. Effect of adhesive‐coated glass fiber on the curing and tensile properties of NR,NBR, and EPDM formulations

Adhesive‐coated glass fibers (3 and 6 mm in length) were added at loadings of 10, 20, and 30 phr in natural rubber (NR), nitrile rubber (NBR), and ethylene–propylene–diene comonomer (EPDM) formulations in both plain and carbon black mixes. The compounds were mixed in a two‐roll mill and were characterized for their cure properties, tensile, tear, and Mullin's effect. In NR mixes, all of the formulations showed reversion in cure behavior, suggesting that NR remained unaffected. In NBR and EPDM mixes, almost all of the mechanical properties of the fiber improved. The result was more significant in EPDM than in NBR. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1111–1123, 2004     

Relaxation time,activation energy,and reaction pathway determination of the poly(ethylene glycol dimethacrylate)–dopant (I2) interaction with the nuclear magnetic resonance technique

Conductive polymers were obtained with a new polymerization method in which UV light was used as a photochemical initiator. In a previous work, optimum irradiation times were determined to obtain high conversion percentages. The effect of dopants on the conductivity of the polymer poly(ethylene glycol dimethacrylate) (PEGDM) was studied with LiClO₄ and I₂ as a dopant. The most effective dopant concentration was determined by the measurement of conductivities. Through the tracing of the conductivity change at various temperatures during the reaction of PEGDM with the dopant, the activation energies of the interactions were calculated, and a method was developed to follow the kinetics of the polymerization reaction with a conductometric technique. This work presents a nuclear magnetic resonance (NMR) study of the same polymer prepared under the optimum conditions with the results obtained in a previous study. NMR spectroscopy was used to determine the relaxation time, rate constants, and activation energy of the polymer–dopant interactions. As a preliminary study, pyruvic acid was used, and for acid‐catalyzed pyruvic acid/water reactions, the relaxation time, activation energy, and enthalpy change values (ΔH) were determined. With the same NMR technique, the reaction mechanisms of the polymerization, relaxation times, and rate constants of the polymer–dopant interactions were determined. The polymerization pathway was determined with NMR spectra; the results were confirmed by the calculation of the activation energies and bond‐breaking energies. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:5087–5101, 2006