Deformation Of Polymer Films Research Articles

Transformation of the structure of the polyimide film during deformation: The effect of thickness

The effect of the thickness of the amorphous polymerized films of poly-4,4'-diphenylene oxide pyromellitimide on the structure after deformation by stretching at 293 K and 77 K was studied. The evolution of the macromolecular structure was concluded based on the results of the redistribution of the intensity diffraction peaks. It was established that the structure of films with a thickness of 75 μm is homogeneous and does not cardinal changes after deformation. Deformation of polymer films with a thickness of 125 μm leads to the appearance of regions with long-range order in the sample.

Parametric Study on Electric Field-Induced Micro-/Nanopatterns in Thin Polymer Films.

Electric field-induced micro-/nanopatterns in thin polymer films, sometimes referred as electrohydrodynamic patterning, is a promising technique to fabricate micro-/nanostructures. Extensive attention has been attracted because of its advantages in microcontact (easy demolding) and low cost. Although considerable work has been done on this technique, including both experimental and theoretical ones, there still appears a requirement for understanding the mechanism of electrohydrodynamic patterning. Thus, we systematically studied the effect of different parameters on electrohydrodynamic patterning with a numerical phase field model. Previous researchers usually employed lubrication approximation (i.e., long-wave approximation) to simplify the numerical model. However, this approximation would lose its validity if the structure height is on the same scale or larger than the wavelength, which occurs in most cases. Thus, we abandoned the lubrication approximation and solved the full governing equations for fluid flow and electric field. In this model, the deformation of polymer film is described by the phase field model. As to the electric field, the leaky dielectric model is adopted in which both electrical permittivity and conductivity are considered. The fluid flow together with electric field is coupled together in the framework of phase field. By this model, the effect of physical parameters, such as external voltage, template structure height, and polymer conductivity, is studied in detail. After that, the governing equations are nondimesionalized to analyze the relationship between different parameters. A dimensionless parameter, electrical Reynolds number ER, is defined, for which, a large value would simplify the electric field to perfect dielectric model and a small value leads it to steady leaky model. These findings and results may enhance our understanding of electrohydrodynamic patterning and may be a meaningful guide for experiments.

IMD 공정 중 필름 변형 특성 파악을 위한 사출 및 필름성형 간 연계해석

In various manufacturing industries, an in-mold decoration (IMD) process for plastic objects is widely utilized because a film forming and an injection molding processes run simultaneously. In the present study, the deformation of polymer film and filling of resin in the IMD process were numerically investigated to evaluate the quality of the plastic object formed by the IMD process, which consists of thermoforming and injection molding processes. To obtain the initial shape of the polymer film during the injection molding process, the deformation of the polymer film in the thermoforming process was pre-formed using the vacuum conditions to attach the film to a cavity. Since the properties and deformation of polymer film are greatly affected by the behavior of polymer resin being injected into a mold cavity, numerical simulations for the injection molding and film forming were performed with one-way coupling method. The results showed that the injected resin could lead to the tearing of the polymer film in local regions near the corners. In order to verify the proposed numerical methodology, the numerical results of the deformation patterns printed on the initial polymer film were compared with the experimental data. The proposed methodology to couple film forming analysis with injection molding analysis can be used to predict the deformation of film in IMD process.

Structure and properties of nanosized coatings deposited onto polymers

Results of studies aimed at developing a new approach to measuring stress-strain properties of nanosized solids (strength, yield stress, and the value of plastic deformation at uniaxial tension) are generalized. This approach is based on the analysis of the parameters of microrelief arising upon the deformation of polymer films with thin coatings. It is demonstrated for the first time that the stress-strain properties of aluminum coatings deposited onto Lavsan substrates depend on the level of stresses in the substrate, the value of its deformation, and the thickness of the coating. The evolution of these parameters is related to the strain hardening of metal and the effect of nanostructuring of crystalline materials in the range of small thicknesses. When precious metal (Au, Pt) nanosized films are deposited onto polymers by ion-plasma sputtering, in the course of metal deposition, polymer surface layers interact with cold plasma. Stress-strain properties of polymer surface layers modified by plasma are quantitatively estimated for the first time. The model is proposed that makes it possible to take into account the contribution of the properties of precious metal and plasma-modified polymer surface layer to the strength of the coating.

Nanoscale repetitive impact testing of polymer films

The deformation of polymer films under repetitive contact at high strain rates was investigated using nanoscale impact testing. Four systems were studied: (i) rubber-modified acrylonitrile-butadiene-styrene (ABS) (0–25 wt% rubber), (ii) uniaxially and biaxially drawn poly(ethylene terephthalate) film; (iii) poly(ethylene oxide)–clay nanocomposites, and (iv) nylon 6–organoclay nanocomposites. The initial results suggest that the technique has much potential in evaluating the fatigue behavior of thinner polymer films and coatings that are unsuitable for conventional methods designed for bulk samples. The extent of impact-induced deformation may be used as a measure of ductility because ductile failures are associated with significant plastic deformation before failure whereas brittle failures usually involve little plastic deformation. The nano-impact technique provides valuable highly localized information about deformation under high strain rate, which is complementary to low strain rate tests such as nanoindentation and nano-scratch. The technique has been shown to be sensitive to nano-/microstructural variations in ABS–rubber film when Berkovich indenters and low impact forces were used. The impact behavior of the nanocomposites is only significantly worse than that of the virgin polymers at the highest clay loading studied (15 wt%). This could be a factor when assessing the suitability of novel nanocomposite materials for applications where toughness is important. On ABS film, there is only an approximate correlation between the plastic work function determined from nanoindentation and the rubber loading in the film while the correlation between the rubber loading and nano-impact data is clear, suggesting that the dynamic test is a more useful predictor of thin polymer film toughness than the slow-loading quasi-static indentation test.

Deformation of polymer films by bending forces

By means of computer simulation, we study the deformation of nanoscale polymer films under the action of external bending forces. The polymer is represented by a generalized bead-spring model, intended to reproduce characteristic features of n-alkanes. The film is loaded by the action of a prismatic blade which is pressed into the polymer bulk from above and a pair of columns which support the film from below. The interaction between blade and support columns and the polymer is modelled by the repulsive part of a Lennard-Jones potential. For different system sizes as well as for different chain lengths, this nanoscale experiment is simulated by molecular dynamics methods. Our results allow us to give a first characterization of deformed states for such films. We resolve the kinetic and the dynamic stage of the deformation process in time and access the length scale between discrete particle and continuum mechanics behaviour. For the chain lengths considered here, we find that the deformation process is dominated by shear. We observe strangling effects for the film and deformation fluctuations in the steady state.

Deformation of Polymer Films by Bending Forces

AbstractWe study the deformation of nano-scale polymer films which are subject to external bending forces by means of computer simulation. The polymer is represented by a generalized bead-spring-model, intended to reproduce characteristic features of n-alkanes. The film is loaded by the action of a prismatic blade which is pressed into the polymer bulk from above and a pair of columns which support the film from below. The interaction between blade and support columns and the polymer is modeled by the repulsive part of a Lennard-Jones potential. For different system sizes as well as for different chain lengths, this nano-scale experiment is simulated by molecular dynamics methods. Our results allow us to give a characterization of deformed states for such films. We resolve the kinetic and the dynamic stage of the deformation process in time and access the length scale between discrete particle and continuum mechanics behavior. For the chain lengths considered here, we find that the deformation process is dominated by shear.

Effect of polymer nature on permeability of membranes prepared by deformation of polymer films in adsorption-active media

Hydraulic permeability of water-alcohol mixtures has been measured in polymer membranes based on poly(tetrafluoroethylene) and polyamide-6, deformed in adsorption-active media. Preferential sorption of one component of the mixture decides on the character of the dependence of permeability on composition; in the absence of preferential sorption the above dependence is given only by the viscosity of the permeant. The interaction between the permeant and the membrane was estimated from measurements of mechanical properties of polmers in contact with the liquid medium.