Tomoyuki Kasemura

Surface dynamics for poly(vinyl alkylate)s via dynamic contact angle and adhesion tension relaxation

Abstract Dynamic contact angle (DCA) and adhesion tension relaxation (ATR) for poly(vinyl alkylate)s (PVA1s) were measured. Advancing contact angle initially increased with an increase in the side-chain-length and after a maximum at C10, it decreased, while receding contact angle showed a complex behaviour. A large contact-angle hysteresis was observed. DCA also depended on the dipping velocity. Results on ATRs showed that the surface molecule of these PVA1s had large molecular mobility. Reproducibility of ATR was also observed. These phenomena were explained by the reorientation of the segment at polymer/water or polymer/air interface so as to minimize interfacial free energy.

Surface molecular mobility for copolymers having perfluorooctyl and/or polyether side chains via dynamic contact angle

Abstract It is well known that a segment of a multicomponent polymeric system such as copolymer selectively adsorb and orient to the surface of the system so as to minimize interfacial free energy in response to an environmental media. Surface molecular mobility of perfluorooctyl (PFO) group of acrylic copolymers, having PFO as a side chain, was investigated via dynamic contact angle and X.p.s. For all copolymers, more fluorine was detected than calculated amount from composition via X.p.s. In addition, the shallower sampling depth of X.p.s., the more fluorine was detected. These sample polymers exhibited a relatively large contact angle hysteresis. Advancing contact angle θA for copolymers increased with an increase in PFO content. Receding contact angles were largely influenced by polar group of copolymers.

Studies on The Modification of Epoxy Resin with Silicone Rubber

Abstract In order to find a compatibilizer for epoxy resin/silicone rubber systems, interfacial tension of epoxy resin mixed with modified silicone oils which had the compatible groups to epoxy resin was measured against RTV silicone rubber and silicone oil. From the results, it was found that one of polyether modified silicone oils (EtMPS) had strong interfacial activity. Then using the EtMPS as the compatibilizer, RTV silicone rubber or silicone diamine was filled in epoxy resin. The effects of silicone content of these materials on impact fracture energy and on peel strength were investigated. The impact fracture energy of epoxy resin was increased by the addition of RTV silicone rubber up to two times that of unmodified resin while silicone diamine had almost no effect which might be due to the small molecular weight. T-peel strengths of aluminium plates bonded by epoxy resin filled with RTV silicone rubber and with silicone diamine effectively increased with the increasing of silicone content showing...

Surface segregation and miscibility in blends of poly(ethyl acrylate) with poly(vinylidene fluoride-co-hexafluoroacetone)

In blends of poly(ethyl acrylate) (PEA) and poly(vinylidene fluoride-co-hexafluoroacetone) [P(VDF-HFA)], surface segregation of the P(VDF-HFA) component was confirmed by X-ray photoelectron spectroscopy. The PEA/P(VDF-HFA) blends exhibited lower critical solution temperature phase behaviour, with a critical temperature of 150°C. Since the surface tension value of P(VDF-HFA) is lower than that of PEA, this may influence surface segregation behaviour in PEA/P(VDF-HFA) blends. Surface segregation results of the PEA/P(VDF-HFA) blends are compared with those from a previous study on immiscible acrylate copolymer/fluoro copolymer blends.

Acrylate Copolymer/Ultraviolet Curable Oligomer Blends as Pressure-sensitive Adhesives

Abstract For the blends of acrylate copolymer [poly(2-ethylhexyl acrylate-co-acrylic acid); P(2EHA-AA)] with ultraviolet (UV) curable oligomer [urethane acrylate oligomer; UAO], pressure-sensitive adhesive (PSA) properties, such as peel adhesion, probe tack, and holding power were examined. The values of peel adhesion and probe tack of the P(2EHA-AA)/UAO blends were dramatically reduced by UV irradiation. On the other hand, all blends had a high holding power even if these blends were cured by UV irradiation. The mechanism of reduced PSA properties was investigated via dynamic mechanical properties, DSC, and dynamic contact angle (DCA). The peel adhesion decreased monotonically with increasing storage modulus, E′, and loss modulus, E″, for all non-UV and UV-cured blends. Since modulus values and glass transition temperatures, Tg, of these blends after UV irradiation were higher than those of these blends before UV irradiation, we judged that the reduced peel adhesion and probe tack values were caused by the modulus increase and the Tg increase due to UV irradiation. In other words, the ability of the deformation energy of UV-cured blends to influence the adhesive tests was reduced by the curing process. The DCAs of non-UV-cured blends were the same as those of UV-cured blends. We presumed that the segment mobility of the polymer chain on the surface did not contribute to the reduced peel adhesion and probe tack values.

Surface molecular mobility for copolymers having both hydrophobic and hydrophilic side chains via dynamic contact angle measurement

Abstract The reorganization of a surface structure in response to a change in environmental media was investigated for copolymers having both hydrophobic polydimethylsiloxane (PDMS) and hydrophilic methoxypoly-ethyleneglycol (MPEG) side chains via dynamic contact angle (DCA). These copolymers showed a large contact angle hysteresis and a dependency of the advancing and receding contact angle on dipping velocity (DV). Composition dependency of DCA for these copolymers is also discussed. In addition to this, adhesion tension relaxation, F(t), for MMA/MPEGMA/PDMSMA was determined. F(t) in the advancing process increased with elapsed time and decreased in the receding process. These phenomena were explained by the adsorption and reorientation of hydrophilic segments to the water/copolymer interface in water. In XPS analysis, more oxygen atoms were detected on the surfaces of MMA/MPEGMA after immersion in water than before. For MMA/MPEGMA/PDMSMA, the atomic ratio of Si to C increased with an increase in PDMSMA...

Surface Modification of Epoxy Resin with Silicone-containing Block Copolymers

Abstract In order to improve oil and water repellency, silicone-containing block copolymers, composed of methylmethacrylate (MMA), glycidylmethacrylate (GMA), and polydimethylsiloxanemethacrylate (SMA), were blended in an epoxy resin. It was expected that the low surface energy dimethylsiloxane segments would adsorb and orient at the exterior of the resin to make a thin surface phase and the glycidyl groups would mesh with the epoxy resin by primary bonding. The techniques of X-ray photoelectron spectroscopy (ESCA), dynamic contact angle (DCA) and peel strength measurements of pressure sensitive adhesives were used to characterize the modified epoxy resin surface phases. The amount of Si2p obtained via angular dependent ESCA investigation in the near surface region of the modified resin increased with decreasing sampling depth. With an increase in modifier content, both the amount of Si2p and O1s also increased. Both advancing and receding contact angles for an aluminum plate coated with modified resin, m...

Application of Poly(acetic Acid)–Based Graft Copolymer as a Compatibilizer for Poly(L-lactic Acid)/Poly(butylenesuccinate) Blend System

Poly(L-lactic acid) (PLLA) was blended with poly(butylenesuccinate) (PBS) using a single-screw extruder to modify the poor characteristics of these polymers. Furthermore, when both polymers were blended, the graft copolymer that was synthesized by partially saponified poly(vinyl alcohol) (PSPVA) and ϵ-caprolactone (ϵ-CL) was used as a novel compatibilizer. The structure of the synthesized compatibilizer was determined by 1H or 13C NMR. From this result, the ring-opening polymerization of the ϵ-CL occurred at the hydroxyl group of PSPVA. The structures of the PLLA/PBS solvent-cast blended films could be observed via an optical microscope. From the optical microscopic observation, the structures of the solvent-cast blended films with the synthesized compatibilizer were more homogeneous than those of the solvent-cast blended films without the compatibilizer. The mechanical properties of the PLLA/PBS extruded blended films were determined by a tensile test. The result showed the tensile strength of the blended films with the synthesized compatibilizer was greater than that of the blended films without the compatibilizer.

Surface enrichment in blends of poly(ethyl acrylate) with poly(vinylidene fluoride-co-hexafluoroacetone)

Abstract The surface enrichment in blends of poly(ethyl acrylate) (PEA) and poly(vinylidene fluoride-co-hexafluoroacetone) [P(VDF-HFA)], the latter of which has a low surface energy, has been observed by using X-ray photoelectron spectroscopy (XPS) at the miscible equilibrium state attained by annealing at 140°C, above the melting temperature. The semi-log plots of In [θ1(d) − θ1b] versus depth d for PEA/ P(VDF-HFA) blends were obtained by the take-off angle dependence of XPS measurements. In the PEA/P(VDF-HFA) blends, the In [θ1(d) − θ1b] versus d plots could be well approximated by a straight line, where θ1(d) and θ1b are the volume fractions of the component with low surface energy from the surface to depth d and in the bulk, respectively. As a result, the effect of annealing on the surface enrichment of P(VDF-HFA) is also reported for the PEA/P(VDF-HFA) blends.

Adhesion Properties of Acrylic Copolymers Modified with Si-Containing Copolymer

Abstract We made clear the cause of the increase in peel strength of pressure sensitive (PS) adhesives as a function of contact time, and investigated how to modify PS adhesives to maintain a low and constant peel strength for a long time. It was found that polar groups in the adhesive orient to the interface between the adhesive and the (stainless steel) metal substrate (SUS 304) so as to minimize interfacial free energy during adhesion, and the orientation increased affinity between the adhesive and the metal material and increased the peel strength as a result. The use of modifier which contained both P(MMA-co-SiMA) and PDMS showed an excellent modification effect, although modification with only PDMS or P(MMA-co-SiMA) was not sufficient. It was suggested that PDMS which migrated to the surface was extended uniformly over the surface by PDMS segments of P(MMA-co-SiMA) and that the enriched layer of PDMS on the adhesive surface worked as a barrier to prevent the orientation of polar groups in bulk. Ther...