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The relationship between the morphology and the mechanical properties of copolymer ethylene−methyl methacrylate (EMMA) was estimated as a function of temperature by using polarized light scattering, X-ray diffraction and 13C solid-state NMR. All of these measurements revealed unstable crystallites within the EMMA films having a MMA content >14 mol %, crystallinity less than 10%, and crystal size of about 3 nm. On the other hand, the ethylene sequences in the amorphous phase had an ordered arrangement rather than a random orientation. It is evident that these characteristics are due to the strong repulsion between MMA and ethylene. Namely, MMA side groups suppress the crystallization as an essential property of ethylene sequences; consequently, the difficulty of accelerating the self-arrangement of ethylene sequences as crystallites leads to a local ordered arrangement of long ethylene sequences in the amorphous phase. The maximum draw ratio of the EMMA film reached 10 times at room temperature. A specimen with a draw ratio <2 showed a reversible change of stress−strain curves up to 40 repetitions at room temperature. This behavior appears to be within the framework of ideal rubber elasticity. However, the stress at a fixed strain decreased with passing time as well as with increasing temperature. This behavior is completely out of the framework. Such inconsistency is due to the fact that small crystallites playing a cross-linking role became disrupted by chain slippage at a constant strain and at elevated temperature.

Water‐soluble graft copolymers with phospholipid polar group were synthesized by the macromonomer method and their properties in water were investigated by surface tension and fluorescence spectroscopic measurements. At first, 2‐methacryloyloxyethyl phosphorylcholine (MPC) was polymerized in the presence of 3‐mercapt propionic acid as a chain transfer agent and carboxyl group‐terminated oligo (MPC) was obtained. The oligo (MPC) reacted with glycidyl methacrylate to convert the carboxyl group to a polymerizable methacryloyl group. The MPC macromonomer obtained was copolymerized with hydrophobic n‐butyl methacrylate (BMA) and a graft copolymer was obtained. The graft copolymer, poly(MPC‐graft‐BMA), was water‐soluble when the MPC unit mole fraction was above 0.40. The surface tension of the aqueous solution of poly(MPC‐graft‐BMA) did not depend on the polymer concentration below 0.1 wt %. This tendency was the same as that which appeared in aqueous poly(MPC) solution. The fluorescence intensity of hydrophobic probes observed in an aqueous solution of the poly (MPC‐graft‐BMA) was also the same level as that observed in the case of poly(MPC). These results clearly indicated that the poly(MPC‐graft‐BMA) took a domain structure like micelle in water, i.e., the hydrophobic poly(BMA) backbone was in the core part and the hydrophilic poly(MPC) chain formed the shell part of the micelle. © 1994 John Wiley & Sons, Inc.

The so-called "super-salt-resistive gel", or poly(4-vinylphenol) (P4VPh) hydrogel, of different water contents ( H = 97-51%) was prepared by cross-linking with different amounts of ethylene glycol diglycidyl ether. 1H NMR spectroscopy was used to investigate the dynamic properties of water in the gel samples in terms of the spin-spin relaxation. The T2 values in those hydrogels were analyzed by assuming a two-component system, namely, T 2(long) and T2(short), and their fractions were obtained. In the higher water content region (75% < or = H < or = 97%), T2(long) for P4VPh gel was almost constant or even slightly increased with decreasing temperature. On the other hand, T2(long) for poly(vinyl alcohol) (PVA) gel (80% < or = H < or = 96%) significantly decreased with decreasing temperature, showing a natural behavior for water mobility in common hydrogels. Water in P4VPh gels of lower water contents ( H = 70% and 51%) also showed intriguing behaviors: the T2 values are much larger than those of gels with higher water contents and decreased with decreasing temperature only in the lower temperature range (<10 degrees C). The fraction of T2(long) values of P4VPh gel showed another contrast to those of PVA gel; the latter decreased with decreasing water content (normal behavior), while in the former gel the highest fraction (ca. 60% at 20 degrees C) was observed for a sample with the lowest water content ( H = 51%). On the other hand, the results of DSC measurements for P4VPh gel were less specific than those of T2 and comparable to those of common hydrogels such as PVA; with decreasing water content, the total amounts of free water and freezable bound water per polymer mass (g/g) decreased, while the amount of nonfreezing water per polymer also decreased.

The friction of rolling guideways in the prerolling region displays hysteretic behavior known as nonlinear spring behavior (NSB). NSB deteriorates motion accuracy and causes vibration in the feed direction. Therefore, the influences of NSB on the dynamic characteristics of rolling guideways should be clarified. This paper describes the influence of NSB on the dynamic characteristics of a rolling guideway. A simple friction model is constructed based on the Masing rule. Because the proposed friction model is described with only three parameters, the factor that inherently affects the dynamic characteristics can be clearly identified. To clarify the influence of NSB, the impulse response, frequency response, and steady state motion are analyzed by numerical analysis. According to the results, the dynamic characteristics in the feed direction depend only on the change rate of friction in the prerolling region, which is introduced to the friction model as the shape factor, n. The stiffness and damping are high when the change rate of friction is high in the prerolling region. The frequency response function is forcedependent, and its tendency is varied by n. The frequency response function includes harmonic and super harmonic resonances. When the carriage is excited with a frequency lower than that of the super harmonic resonance, a displacement spike (quadrant glitch) is observed. Additionally, the nonlinearity cannot be ignored when the carriage is excited with a frequency lower than the harmonic resonance. Finally, an experiment with a roller guideway is conducted to prove the validity of the analysis. The resonance frequency and compliance at the harmonic resonance measured by the experiment accurately conform to the analytical results. IntroductionRolling guideways are widely used in machine tools because they can achieve high speed and precise motion at low cost. The rolling elements circulating inside of a carriage elastically support loads. The elastic deformation of rolling elements and raceways causes rigid-body vibration of a carriage in five degrees of freedom, excluding the feed direction (Ohta and Hayashi, 2000). Additionally, the circulation of rolling elements causes the rolling element passage vibration owing to the variations in stiffness (Matsumoto, 2004). Moreover, the nonlinear elastic behavior of friction causes vibration in the feed direction. This elastic behavior of friction is known as nonlinear spring behavior (NSB) (Otsuka and Masuda, 1998) (Futami et al., 1990) (Koizumi and Kuroda, 1990. These vibrations deteriorate the motion accuracy of a feed drive equipped with rolling guideways.NSB particularly causes the force dependency of the dynamic characteristics of a rolling guideway in the feed and pitch directions (Sakai et al., 2014). The cutting force varies periodically over a wide range during the machining process. Thus, the dynamic characteristics of a feed drive equipped with a rolling guideway vary throughout the machining process. This variation in dynamic characteristics ...