Yasunori Hatano

Synthesis of Lignin /Epoxy Resins in Aqueous Systems and Their Properties

A new resin system was developed only by mixing the alkaline solution of industrial kraft lignin with water-soluble epoxy compound, polyethylene glycol diglycidyl ether (PFGDGE), and curing reagent. The viscoelastic properties of cured resin films were investigated. As the content of the kraft lignin in the resins increased, the absorption peak due to the glass transition for cured resins shifted to a higher temperature with spreading. It was found that the glass transition temperature of cured resins can be modified by changing kinds of PEGDGE and curing reagents. Addition of the emulsion type of diglycidyl ether of bisphenol A (DGEBA) to the blendings also could make the glass transition temperature of cured resins higher. Since only one broad dispersion peak due to the glass transition could be observed, it was suggested that the cured resins had compatibility to form a kind of IPNs.

Viscoelastic properties of liquefied wood/epoxy resin and its bond strength

Summary A new resin system, in which liquefied wood was reacted with various epoxy compounds, was previously developed. This paper reports the syntheses of two types of liquefied wood/epoxy resins with the ratio of liquefied wood to epoxy compounds (L/E ratio) of either 1/0.5 or 1/1. Furthermore, the viscoelastic properties obtained from the dynamic mechanical measurements of the cured resins and their adhesive bond properties measured as tensile shear strength are reported. The results from dynamic mechanical measurements indicated that the resins with a L/E ratio of 1/0.5 could be cured at 90°C, while the resins with L/E ratio of 1/1 were cured at 150°C. The resins cured with triethylene tetramine (TETA) at 150°C or 90°C had almost the same level of the normal adhesive shear strength as that of the commercial epoxy resin. The high level of adhesive shear strength of the resin cured at 150°C was maintained after the glued specimens were soaked in water at 60°C, while the share strength of the resins cured at 90°C was reduced by either the water soaking at 60°C or the cyclic boiling test.

Rheological study on the adhesion properties of the blends of ethylene vinyl acetate/terpene phenol adhesives

Measurements of the shear, tensile, peel, and creep strength of ethylene vinyl acetate (EVA)/CaCO3/terpene phenol adhesive system at three different ratios [100/60/0 (EVA-O), 80/48/20 (EVA-20), and 60/36/40 (EVA-40) by weight, using wood and aluminum as adherends] were conducted. Over a wide range of temperatures and rates of deformation, adhesion shear, tensile, and peel strength results, as well as the creep response over a broad range of temperature and stresses, were found to yield a single master curve by means of the reduced-variable technique. It was observed that the peak of E′ representing Tg, shifted toward higher temperatures as the amount of terpene phenol in the blend was increased. The most obvious effect of increasing the tackifier resin was the shifting of the adhesion strength master curves to the direction of lower rates. The shift was associated with the rise in Tg as the blend ratio was increased. The influence of the tackifier resin in modifying the viscoelastic properties of the adhesive was further described in a comparison of the adhesion strength master curves with corresponding dynamic viscoelastic curves of the adhesive films. The master curves for the creep response of the adhesives showed that the stress-breaking time relationship shifts toward longer time for EVA-40 with high Tg. Thus, it was found that the strength of adhesion is due mainly to dynamic effects in the adhesive of a viscous nature in the same way to the cohesive strength of the viscoelastic materials.

Miscibility and PSA Performance of Acrylic Copolymer and Tackifier Resin Systems

The influence of miscibility of an acrylic PSA and several tackifier resin systems upon PSA performance was investigated. When the acrylic copolymer and the resins were blended in various proportions, three types of mixing state were found: miscible system, partially miscible system and immiscible system. In the case of miscible systems, PSA performance (tack, peel strength and shear resistance) depended upon the viscoelastic properties of the PSA. In the case of completely immiscible systems, the above PSA performance depended primarily upon the viscoelastic properties of a continuous matrix phase, and the separated resin phase acted as a kind of filler. In the case of partially miscible systems, the PSA performance changed discontinuously at the resin concentration where phase separation occurred. It suggests that the phase structure of a PSA greatly influences the PSAs performance.

Bonding and Debonding Processes in Tack of Pressure-Sensitive Adhesives

Abstract Rolling friction coefficient of two acrylic pressure sensitive adhesives (PSAs) are measured as a function of velocity at several temperatures. It is found that the time (or velocity)-temperature superposition procedure is applicable for one PSA, while it is not for the other. The authors came to the conclusion that the rate of increase of the true contact area is different for the two adhesives. The time-temperature superposition is possible only in the case where the activation energy of the bonding process is equal to that of the debonding process.

Rheological Study on Tack of Pressure-Sensitive Adhesives

Abstract It is pointed out that the tack of pressure-sensitive adhesives should be expressed in terms of rolling friction coefficient f of the adhesives. Values of f were determined by both rolling ball and pulling cylinder experiments, and the dependence of f upon viscoelastic properties and thickness of the adhesives was studied. The experimental results were interpreted by the model theory previously proposed. It is also shown that the tack of pressure-sensitive adhesives by the conventional ball tack tests corresponds to f measured at the velocity ranging from v ∼ 10 to v ∼ 102 cm/sec.

Rate-temperature dependence of bond strength properties of polyester adhesive

The viscoelastic and adhesion properties of polyester used äs adhcsive to wood has been studied.Tensile, shear, and peel Strength properties for Kaba wood (Betula Maximowicziana Regel) were measured over a temperaturc ränge from -5°C to 61 °C at three dtfferent test rates (crosshead speed), namely; 0.5, 5, and 50 mm/min; äs well äs its crcep response over a wide ränge of breaking time and temperature.The reduced-variable technique was applied over a wide ränge of test ratcs and tcmperatures.The results were found to yield a simple master curve for each Strength in tcrms of rest rate when reduced to a reference temperature by means of the Arrhcnius relation.The activation energies were calculated using the horizontal shift factors determined empirically.Thc results showed the cxistence of two concurrent relaxation mechanisms with different activation energies for each type of Strength. The adhesion maxima are rheological in origin äs rate-temperature equivalence was observed.

Rheological treatment of the adhesion properties of pressure-sensitive adhesives (PSA) by reduced-variable technique

The study of the different properties (dynamic viscoelasticity, shear, tensile, peel, tack, creep) of a double-coated pressure-sensitive adhesive (VHB 4950) comprising of an acryl foam backing and acrylate adhesive was conducted in order to determine some of the factors affecting the nature and general phenoena of the adhesion of this type of material.

Dynamic Mechanical Properties and Adhesive Joint Strengths of Emulsion Polymers Produced by Power Feed Technique. III. Adhesive Joint Strengths of Grafted Power Feed Copolymer

Abstract Power feed copolymers were synthesized using styrene and n-butyl acrylate through non-uniform feeding emulsion polymerization. Poly(vinyl alcohol) (PVA) was used as a protective colloid, onto which vinyl monomers were grafted. Power feed copolymer had a very broad glass transition temperature compared with random copolymer, even if grafting and/or crosslinking were introduced to the system. This tendency was almost the same as the non-grafted power feed copolymer where only low molecular weight surfactant was used. Adhesive joint strengths of power feed copolymers were evaluated compared with random copolymers. In the case of usual linear power feed copolymer, the adhesive joint strengths were not higher than those of random copolymer, which was considered to be due to the lower film strengths of the power feed copolymer. Power feed copolymer having grafting showed slightly higher adhesive joint strengths over a wide range of temperatures than random copolymer. When crosslinking was introduced to...