Dynamic Mechanical Properties Of Polymers Research Articles

Regulation of the Properties of Polymers based on Thiirane using Mixtures of Amine Hardeners

Abstract: Introduction: The possibility of regulating the curing rate and the complex of adhesive, deformation-strength and dynamic mechanical properties of polymers based on bisphenol A dithioester (thiirane) using a mixture of amine hardeners of various chemical nature is investigated. Method: Diethylenetriamine, diethylenetriaminomethylphenol and aminopolyamide were investigated as hardeners. The ratio of the components of the mixed hardener is selected, which provides the best combination of strength properties. Results: It was found that the rate of adhesion and cohesive strength at the initial stage (during the first hour) of curing compositions containing a mixture hardener significantly exceeds compositions cured by individual components of the mixture. Conclusion: The results of measuring the dynamic mechanical characteristics of the studied polymers indicate that the dynamic modulus of elasticity, measured at temperatures below and above the transition from a glassy state to a high elastic one, for a sample containing a mixed hardener has an intermediate value between the values characteristic of samples containing individual components of a mixed hardener. objective: The ratio of the components of the mixed hardener is selected, which provides the best combination of strength properties.

EMI shielding and dynamic mechanical analysis of graphene oxide-carbon nanotube-acrylonitrile butadiene styrene hybrid composites

Carbon nanomaterials such as carbon nanotubes (CNTs), graphene and their hybrid have been studied extensively. Despite having excellent properties of CNTs and graphene have not yet been fully realized in the polymer composites. During fabrication agglomeration of CNTs and restacking of graphene is a serious concern that results in the degradation of properties of nanomaterials into the final composites. To improve the dispersion of CNTs and restacking graphene, in the present research work, we focused on the hybridization of graphene oxide and CNTs. Multiwalled carbon nanotubes (MWCNTs), functionalized carbon nanotubes (FCNTs), and graphene oxide-carbon nanotubes (GCNTs) reinforced acrylonitrile butadiene styrene (ABS) composites were prepared separately by vacuum filtration followed by hot compression molding. Further, dynamic mechanical analysis (DMA), and electromagnetic interference (EMI) shielding properties of ABS composites reinforced carbon nanofillers were investigated. The dynamic mechanical properties of polymers strongly depend on the adhesion of fillers and polymer, entanglement density of polymer chains in the presence of carbon fillers. The dynamic mechanical characteristics such as storage, loss modulus, and damping factor of prepared composites were significantly affected by the incorporation of MWCNTs, FCNTs, and GCNTs. Maximum EMI shielding effectiveness of −49.6 dB was achieved for GCNT-ABS composites which were highest compared to MWCNTs-ABS composites (−38.6 dB) and FCNTs-ABS composites (−36.7 dB) in the Ku band (12.4–18 GHz). These results depict the great potential of GCNTs-ABS composites to be used in various applications of efficient heat dissipative EMI shielding materials for electronic devices.

Infusion of graphene quantum dots to modulate thermal conductivity and dynamic mechanical properties of polymers

Graphene quantum dots are small fragments of graphene that may be advantageous to transferring properties to polymers because of their small size, molecular like interactions, surface chemistry and ability to overcome dispersibility challenges in composite formation. Here, we begin the first thermal conductivity study with graphene quantum dots by revealing the thermal and mechanical properties of composites made by infusing graphene quantum dots into epoxy. We found that graphene quantum dots that have the capability to improve the toughness of epoxy by 260%, increase the thermal conductivity by 144%, increase the glass transition temperature by 10%, increase the storage modulus by 9%, and decrease damping by 45%. We anticipate graphene quantum dots infusion to be a starting point for creating more sophisticated polymer composites.

Enhancement of stiffness and dynamic mechanical properties of polymers using single-walled-carbon-nanotube – a multiscale finite element formulation study

The static and dynamic mechanical properties of polymeric materials can greatly be enhanced by using carbon nanotubes as reinforcement material. However, studies still need to be carried out to characterize the dynamic mechanical properties of the Carbon-Nanotube-Reinforced-Polymer (CNRP) material. Experimental investigations for this purpose have severe limitations and, in most cases, appropriate and reliable experimental work could not be carried out. Computational modelling and simulation encompassing multiscale material behavior provides an alternate approach to study the material behavior. The objective of the present work is to study the enhancement of stiffness and dynamic mechanical properties of Carbon-Nanotube-Reinforced-Polymer (CNRP) material by using a 3D multiscale finite-element model of the representative volume element of the CNRP material. A composite material model consisting of a polymer matrix, an interface region, and a Single-Walled Carbon Nanotube (SWCNT) is constructed for this purpose. The polymer matrix is modeled with the Mooney-Rivlin strain energy function to calculate its non-linear response and the interface region is modeled via van der Waals links. The SWCNT is modeled as a space frame structure by using the Morse potential and as a thin shell model based on Donnell’s Shell Theory. The stiffness response of the CNRP is calculated and the natural frequencies of the CNRP are also determined. The viscoplastic behavior of the polymer matrix material is considered and the rate-dependent characteristics of the CNRP are studied. The damping properties of the CNRP are investigated based on its viscous and structural damping mechanisms. The effectiveness of the SWCNT reinforcement is quantified and characterized.

Dynamic viscoelastic properties of polyvinyl chloride with physical aging

The experimental research of dynamic viscoelastic properties of polyvinyl chloride was conducted by the dynamic mechanical analysis method in this paper. And the fitting equation of dynamic modulus of polymers has been presented. Based on the time-aging time equivalent principle, horizontal shift factor and vertical shift factor of aging time are carried out, which proposes a novel method for the research on time-aging time equivalent analysis of dynamic mechanical properties of polymers during physical aging.

Local Stereochemical Microstructures Dependence of β Relaxation Process in Some Vinyl Polymers: Fundamentals and Correlations

Abstract. Dynamic mechanical thermal analysis (DMTA) is an accessible and versatileanalytical technique where a sample is submitted to an oscillating stress or strain as a function ofoscillatory frequency and temperature. Through this non-destructive measurement, acomprehensive understanding of the dynamic mechanical properties of polymers may be obtained.Key words: PVC, PMMA, -relaxation, chain conformation, local motion, nucleophilicsubstitution, molecular microstructure.IntroductionThe structure property relationships aregreatly significant industrially and scientifically.Most of abundant research work in this field forthe last years has dealt with approaches to thewhole simulation of the physical behavior and,thence, to a macroscopic view of the relatedphysical properties of polymers. In contrast, noattempts to correlate the physical properties withthe molecular microstructure of polymers havebeen made. The implication is that little informationas to the nature and the mechanisms of themolecular nature involvement in the physicalbehaviour of these materials is available. In fact,the studies to correlate every physical propertywith any specific molecular structure, in particularthe local or sequential chain microstructureregardless of the type of vinyl polymer, are ratherscarce if any. The difficulty lies in the fact thatboth the controlled formation of thosemicrostructures along the polymer chain and theiraccurate determination are far from beingsuccessful.Within this framework a rather abundant workin our laboratory has revealed that there exists astraight relation between some physical andchemical behaviours and the occurrence of a fewrepeating steresequences along the chain,especially the mmmr and the mmmmrx (x = m orr)which occur necessarily whenever an isotacticsequence breaks-off. The prominent role of themin a list of physical properties of poly(vinyl chloride)(PVC) including glass transitions, physical ageing,dielectrical relaxations and electrical space chargenature and distribution, has been extensivelyconveyed [1; 4; 5; 6; 8]. Most of the correlationsfound for PVC have been proved to hold true forpoly(propylene) (PP) [2;7]. They have been alsoextended to dynamic mechanical properties of PVCand PMMA. Actually, this paper deals withapproaches to secondary relaxation knowledge asinferred from found correlations with thestereochemical microstructures mentioned below.In general the stereochemical microstructuresthat have been considered are: 1)the isotactic andsyndiotactic sequences, that relate to the extent towhich a polymer exhibits a non-Bernoullian tacticity

Effect of filler geometry on viscoelastic damping of graphite/aramid and carbon short fiber‐filled SBR composites: A new insight

AbstractAn investigation on the effect of filler geometry/shape on the dynamic mechanical properties of polymers was conducted. The viscoelastic damping matrix chosen was SBR and the fillers chosen were graphite, aramid, and carbon short fibers. The study was conducted by taking a control base compound of 20 parts N330 carbon black‐filled styrene butadiene rubber (SBR). Dynamic mechanical thermal analyzer was used to investigate the viscoelastic damping of the rubber composites at low dynamic strain levels. Compressive hysterisis at moderate degree of strain were evaluated for all the composite samples to probe into their high strain static damping properties. SEM was used to investigate the matrix‐fiber interaction and distribution of the fillers. Investigations demonstrated that the matrix‐filler interface plays a major role in energy dissipation. The amount of interface was analyzed by considering the half height width of tan δ peak. Fiber matrix interaction parameter was calculated from the tan δmax values for matrix and composite. It was observed the interaction parameter and the low strain tensile stress values register similar trend. Aramid short fibers were most effective in more energy dissipation than other fillers under consideration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of temperature on the tribological and dynamic mechanical properties of liquid crystalline polymer

The effects of temperature on the tribological and dynamic mechanical properties (DMP) of aromatic liquid-crystal poly(ester- co-amide) were investigated. Specimens for the DMA test and friction and wear test were prepared by compression molding at elevated temperature. The dynamic mechanical properties of the resulting compression-molded liquid crystal polymer (LCP) specimens were evaluated on a Perkin-Elmer DMA instrument, in a three-point bending mode, at a heating rate of 10 °C/min and frequency of 1 Hz from room temperature to 250 °C. The friction and wear behavior of the compression-molded LCP specimens sliding against SA52100 steel in a ball-on-disk configuration was evaluated on a high-temperature friction and wear tester from 25 to 300 °C. The worn surface morphologies of the compression-molded LCP specimens were observed on a scanning electron microscope. It was found that the tribological and dynamic mechanical properties of the LCP strongly depended on the test temperature. Namely, the friction coefficients decreased significantly and the wear rate increased considerably with increasing temperature. This was attributed to the enhanced softening and plastic deformation of the LCP at elevated temperature. The LCP experienced severe plastic deformation, flowing and local melting owing to the destruction of the stiff backbones of the polymeric molecules at excessively high temperature, thus the largest wear rate of the tested LCP was generated at 300 °C. Such a trend in the friction and wear behavior of the compression-molded LCP with temperature conformed well to the corresponding worn surface morphologies. Namely, the LCP worn surface was characterized by mild plastic deformation and micro-cracking as the LCP disk slid against the steel ball at 50 °C, whilst at 100 °C, the plastic deformation and adhesion became severe and the micro-cracking disappeared owing to the plastic flow. The plastic deformation and adhesion became increasingly more severe with further increase of the test temperature up to 150, 200, and 250 °C, owing to the increased plastic flow and local softening and melting of the LCP. Moreover, the storage modulus of the compression-molded LCP greatly decreased with increasing temperature, as did the loss modulus, while the complex modulus and tan δ increased with increasing temperature, which agreed well with the corresponding trend of the tribological behavior with temperature. It was confirmed that the dynamic mechanical properties of the polymer were an important factor of the high temperature tribological behavior.

Measurement of polymer complex modulus properties using several techniques

Various techniques for measurement of the dynamic mechanical properties of polymers are discussed. Special emphasis is given to the vibrating beam, SDOF resonance, SDOF impedance, creep, relaxation, forced oscillation (Metravib viscoanalyzer), and forced torsional oscillation (Metravib micromechanalyzer) techniques. Material property data, generated over wide ranges of temperature and frequency (using the above techniques), are presented in terms of reduced frequency upon application of an Arrhenius temperature‐frequency shift function. Comparison of these properties in the reduced frequency format indicates good correlation between techniques. Specific examples are included consisting of data generated from commercially available materials in both shear and tension‐compression states of stress from which estimates of Poisson's ratio may be determined.

Monitoring the dynamic mechanical behavior of polymers and composites using mechanical impedance analysis (MIA)

AbstractThe techniques of mechanical impedance analysis (MIA) have been evaluated in terms of its potential for use as a reliable dynamic mechanical methodology. The method involves measuring the relation between a force input (excitation) and a motion output (response) between various points on the structure. In its most common and simple form, the force input and velocity output are measured at a single point of the structure and the values of the mechanical admittance (velocity/force) are plotted as a function of frequency. Rapid measurements and analysis of the dynamic mechanical properties of polymers and composites can be obtained by using a dual‐channel FFT spectrum analyzer interfaced with a personal computer. It is demonstrated that the technique can be used to analyze polymer viscoelasticity, to study phase transformation of thermosetting resins, and to monitor cure of integrated composite structures. Also discussed are the potential advantages and limitations of the MIA technique when applied in the fields of polymer science and engineering.

Dynamic mechanical properties of polymer–leather composites

AbstractThe effects of polymer impregnation, moisture, and lubricant oils on the complex modulus of the grain layer of leather have been studied. The impregnated materials were prepared by introducing a mixture of polyurethane oligomer and vinyl monomers into the grain layer and polymerizing by electron‐beam irradiation. Synergism was observed in the interaction of the components of the system and analyzed in terms of the adhesion of the polymer to the collagen fibers.

Error analysis and modelling of non-linear stress-strain behaviour in measuring dynamic mechanical properties of polymers with the Rheovibron

The Rheovibron is widely used for measuring the dynamic mechanical properties of polymers. Poor reproducibility and data variation which have been considered inherent to the Rheovibron operation necessitate both instrument modifications and modelling of the instrument operation for quantitative interpretation of the experimental data. The instrument modifications that have been made in this study include electronic modifications, a new clamp design that eliminates sample mounting and slippage problems, and the design of an environmental chamber, which, along with a nitrogen purge, eliminates moisture condensation on the sample at low temperatures. A previously-developed mathematical model for the instrument has also been extended to account for the effect of the static stress and the stress rate imposed on the sample during measurement. Based on a simple constitutive relation for non-linear stress-strain behaviour of polymers, this model has been applied to a number of polymeric materials including polyethylene, polyimide, poly (ethylene terephthalate), and polypropylene, among others. The instrument modifications and modelling of the influence of static stress and the stress rate imposed on the sample during dynamic mechanical testing allows for reproducible (within 5%) and accurate use of the Rheovibron.

Interaction between Wood and Polymers. Pt. VI. Dynamic Mechanical Properties of Polymers Filled with Wood Components

Article Interaction between Wood and Polymers. Pt. VI. Dynamic Mechanical Properties of Polymers Filled with Wood Components was published on January 1, 1980 in the journal Holzforschung (volume 34, issue 4).

Dynamic mechanical properties of polymers filled with agglomerated particles

AbstractThe filler particles in most filled polymers are not perfectly dispersed but are more or less agglomerated. The degree of agglomeration and the strength of the agglomerates, which can be modified by surface treatments, have a very great effect on the dynamic mechanical properties. Filler agglomerates which are wetted by the polymer matrix produce higher elastic moduli than similar agglomerates which are not wetted. The relative damping in most filled polymers is very temperature‐dependent. A qualitative explanation is given for this temperature dependence. The degree of agglomeration and the strength of the agglomerates are important factors in determining the damping.

Influence of structure on the dynamic mechanical properties of crystalline polymers

Abstract A dynamk mechanical theory is presented whose structural elements correspond to such physically measurable material parameters as the compliance of the phases, the percent crystallinity, and the orientation of the crystalline and noncrystalline regions. The theory is tested by using both structural and dynamk mechanical data from samples of isotactic polyproylene films of varying crystallinity and orientation. For the specific case of isotactic polypropylene the general theory is shown to reduce to a simple two-parameter model. It is further shown that the two-parameter model not only identifies the unique properties of each of the phases separately, but also predicts the dynamic mechanical properties of the polymer over a temperature range of—130°C to 120°C, for samples ranging from unoriented to highly oriented, and varying in crystallinity from 40 to 70%. The model can also predict the dynamic mechanical properties over the same temperature range for strips of these samples cut at varying angl...

An apparatus for the measurement of dynamic mechanical properties of polymers in a gas medium with the vibron viscoelastometer

AbstractThe Vibron Viscoelastometer is useful for obtaining dynamic mechanical properties of film and fibers in atmospheres at 0 and 100% relative humidity. No apparatus has previously been available for obtaining dynamic mechanical properties in a gas medium; however an apparatus and procedure have been developed for measuring these dynamic properties in a gas medium using the Vibron instrument. This technique will be useful in studies on the effects of different gases on polymers in the process and on the effects of gas treatments on materials. A new gas cell which is adaptable for other mechanical testing instruments such as the Instron, Tensometer, and Torsion Pendulum is also discussed.

Synthesis and dynamic mechanical properties of heterogeneous network polymers from poly(L‐glutamic acid) and poly(oxyethylene glycol)

AbstractHeterogeneous network polymers composed of rigid polypeptide chains and flexible polyether chains were synthesized. That is, poly(L‐glutamic acid) (PLGA) was crosslinked with poly(oxyethylene glycol) (PEG) at various carboxy/hydroxyl mole ratios K. The solubility tests and hydrolysis of heterogeneous network polymers suggest that the crosslinking reaction proceeds by esterification. The dynamic mechanical properties of these polymers(100 Hz, −100–200°C) are greatly influenced by the presence of a trace of water and the weight per cent of PLGA. In addition, some of these polymers show only one maximum in the temperature dispersion of dynamic loss modulus E″ and tan δ, although their shape is rather broad. The x‐ray photographs of these polymers show an amorphous halo or weak Debye‐Sherrer rings. These findings suggest that these polymers are not simple adducts; neverthless PLGA and/or PEG domains exist.

The dynamic mechanical properties of polymers at cryogenic temperatures

Abstract A general review of our investigations in the last few years on the cryogenic dynamic mechanical properties of polymers is discussed. The differences in the mechanical spectra between cis and trans polybutadienes and polyisoprenes are considered in terms of molecular structure and packing density. Tensile stress-strain properties of these polymers are considered in relation to secondary glass transitions, free volume, and rate of cooling. Also, the effect of simple organic liquids and solid fillers on the mechanical spectra of polymers is presented. The nature of the polystyrene γ and δ peaks is considered in relation to our investigations on substituted polystyrenes and mechanisms by which diluent molecules modify the polystyrene spectra.

Instrument for investigating the dynamic mechanical properties of polymers by the resonance vibration method

The RUIZ-2T instrument for automatically measuring the dynamic modulus of elasticity and decrement of plastics in the resonance vibration regime is described.

The significance of the rubber damping peak in rubber‐modified polymers

AbstractDynamic mechanical properties have been used as the basis for some important conclusions with regards to the physical properties of rubber‐modified high‐impact polymers. This paper attempts to show that conclusions of this type should be limited to fairly narrow groupings of polymers. Since the size, shape, and position on the temperature scale of a damping peak are influenced by composition, morphology, and method of polymer preparation, the significance of the damping peak associated with the rubber phase of the polymer has probably been generalized to too great an extent. Two examples of polymer groupings are given to illustrate the need for caution in attaching significance to the dynamic mechanical properties of polymers. Also given are two fairly narrow polymer groupings to show to what extent dynamic mechanical properties can be used for a correlation with impact strength and rubber concentration.