We investigated the hydrophilicity of fluorinated carbon fibers at room temperature, that is a new method of surface treatment, and found that through this treatment, wettabillity of the surface of carbon fibers increased dramatically without decrease of tensile strength. Observation by scanning electron microscope (SEM) showed the same surface morphology of fluorinated carbon fibers as that of original fiber. On the other hand, of anodic oxidated fibers. In the case of anodic oxidation as the wettabillity of oxidated fibers increased, the surface roughness increased and resulted in the decrease of tensile strength.
The relationship between the adhesive properties of the interphase of glass fiber/resin and the resultant composite Mode I interlaminar fracture toughness in glass cloth laminate was studied. The Mode I interlaminar fracture toughness of the laminate was obtained by the method of double cantilever beam (DCB) specimen. The delamination resistance of the laminates which have two silane coupling agents and two kinds of resin was discussed on the basis of interlaminar fracture toughness. The crack propagation behavior of DCB test was divided into stable and unstable manners. The fracture toughness and the crack propagation behavior were dependent on the types of silane coupling agents and resins. Mode I interlaminar fracture toughness of the laminate consist of glass cloth which was treated with silane coupling agents and fabricated with unsaturated polyester (vinylester) and epoxy(amine curing system) resin was measured.
Nylon composites containing ultrafine particles such as gold, silver and copper (I) oxide, were prepared by the RAD process. Various properties of the composites such as optical, mechanical, and electrical properties were studied in order to examine the interfacial properties between ultrafine particles and nylon matrix. The composites showed such colloidal colors as red (Au), yellow (Ag), and yellowish green (copper (I) oxide) which were all uniformly transparent without metalic luster. Both solid film of the composite and m -crezol solution of the composite maintained its colloidal color for a long time without agglomeration or aggregation of the particles. The mechanical relaxation of the composites suggested that the rigid nylon region around particle was formed by strong interaction between particles and nylon molecules. This region stably kept holding ultrafine particles in nylon matrix, and it also prevented particles from agglomerating. The composites showed interesting elecrical properties different from those of nylon alone because the rigid region of nylon polarized very slowly by applying the electric field. The time lag in the electrical response was caused by slow relaxation of the interfacial region.
Surface modifications of monodispersed colloidal silica particles with polymers were investigated. In the modification of the particles with hydrophobic and hydrophilic polymer-silane coupling agents, more than 15 times of the amount of the coupling agents for that of silica was at least required to avoid the aggregation of the particles, but addition of a small amount of aqueous ammonia to the reaction system resulted in effective attachment of polymer to silica surface and afforded dispersible polymer/SiO2 composites into organic solvents without aggregation. Radical polymerization of vinyl monomers (styrene, methyl methacrylate and 2-hydroxyethyl methacrylate) using 2, 2'-azobis (2-amidinopropane) dihydrochloride as an initiator on the colloidal silica surface led to the formation of spherical polymer/SiO2 composites, and retained particle size. Surface grafting of polystyrene to poly (N-vinyl-2-pyrrolidone) having vinylphenylene end group by radical polymerization on the particle surface also successfully brought about the formation of monodispersed polymer/SiO2 composites.
Engineering plastic films such as polyethylene terephthalate, nylon 6, polyimide, p-aramid, polycarbonate and Polyphenylene sulfide were treated with sputter etching and low temperature argon plasma, and their adhesive properties were investigated in relation to critical surface tension, SEM photograph and ESCA measurement. Peel strength increased by sputter etching and argon low temperature plasma treatments, especially with the former. Although critical surface tension increases by both treatments in one minute, adhesive property considerably increases by sputter etching over 3 min, because the treatment causes physical change such as surface roughness and protrusion. Thus, the sputter etching seems much more effective to increase the peel strength.
In order to improve the water-resistance of the layer produced by silane coupling agents such as 3-methacryloxypropyltrimethoxysilane (3-MPS), the effect of addition of various hydrophobic silanes to 3-MPS was studied. The hydrophobic silanes were trifluoropropyltrimethoxysilane (LP1-T), nonafluorohexyltrimethoxysilane (LP4-T), heptadecafluorodacanyltrimethoxysilane (LP8-T), heptadecafluorodacanylmethyldimethoxysilane (LP8-D), phenyltriethoxysilane (PS) and octyltrimethoxysilane (Oct). The tensile bond strengths of acrylic resin to the glass plate treated with the mixed silane increased with increasing content of the hydrophobic silane in the mixed silane and reached to a maximum when the content was 40-50% by weight, and decreased at the content above 50%. The tendency of the strength was almost the same among those silanes. For example, in the case of a mixture of LPl-T and 3-MPS, the strength of the resin was 29 MPa when the content of LP1-T in the mixed silane was 40% and was higher than that of 20 MPa of 3-MPS alone, and the strength at the content of 80% of LP1-T was 21 MPa. There was a difference in the strength of those specimens after 2000 thermal cycles. In the above thermal cycles, the specimens were alternately immersed for 1 minute in water baths having temperatures of 4°C and 60°C. The addition of LP1-T and LP4-T to 3-MPS was excellent in durability against water, that of PS and Oct was slightly effective, and LP8-T and LP8-D was poor. A higher bonding strength and better water-resistance produced by using a mixture of 3-MPS and a hydrophobic silane may be due to the increase of diffusion of the matrix resin into the hydrophobic siloxane layer, and the formation of an interpenetrating polymer network between the resin and the layer.