Mechanical Properties Of Polymeric Materials Research Articles

On the improved mechanical properties of nanoclay reinforced ABS composite for fused deposition modelling

Due to the restrictions imposed by the availability of materials in fused deposition modelling process (FDM), the achieved mechanical properties of FDM parts are limited. This scarceness leads to a critical need for improving the mechanical properties of FDM parts. The incorporation of nanoclay can effectively improve the mechanical properties of polymeric materials used in FDM. The present study investigates the FDM of clay-based polymer nanocomposite and examines the effect of dual extrusion in part fabrication. Incorporation of nanoclay demonstrated significant improvement in tensile, modulus and compressive strength as 14.5%, 21% and 24% respectively. A substantial increase in modulus and compressive behaviour was observed in hybrid parts. The developed material possesses enhanced properties compared to the virgin polymer and can be used effectively as an alternative material for FDM process. Dual extrusion technique can aid to tailor material properties as per the requirements in FDM parts.

On the improved mechanical properties of nanoclay reinforced ABS composite for fused deposition modelling

Due to the restrictions imposed by the availability of materials in fused deposition modelling process (FDM), the achieved mechanical properties of FDM parts are limited. This scarceness leads to a critical need for improving the mechanical properties of FDM parts. The incorporation of nanoclay can effectively improve the mechanical properties of polymeric materials used in FDM. The present study investigates the FDM of clay-based polymer nanocomposite and examines the effect of dual extrusion in part fabrication. Incorporation of nanoclay demonstrated significant improvement in tensile, modulus and compressive strength as 14.5%, 21% and 24% respectively. A substantial increase in modulus and compressive behaviour was observed in hybrid parts. The developed material possesses enhanced properties compared to the virgin polymer and can be used effectively as an alternative material for FDM process. Dual extrusion technique can aid to tailor material properties as per the requirements in FDM parts.

Apparent depth‐dependent modulus and hardness of polymers by nanoindentation: Investigation of surface detection error and pressure effects

ABSTRACTNanoindentation is a widely used technique to characterize the mechanical properties of polymeric materials at the nanoscale. Extreme surface stiffening has been reported for soft polymers such as poly(dimethylsiloxane) (PDMS) rubber. Our recent work [J. Polym. Sci. Part B Polym. Phys. 2017, 55, 30–38] provided a quantitative model which demonstrates such extreme stiffening can be associated with experimental artifacts, for example, error in surface detection. In this work, we have further investigated the effect of surface detection error on the determination of mechanical properties by varying the sample modulus, instrument surface detection criterion, and probe geometry. We have examined materials having Young's moduli from ∼2 MPa (PDMS) to 3 GPa (polystyrene) using two different nanoindentation instruments (G200 and TI 950) which implement different surface detection methods. The results show that surface detection error can lead to apparent large stiffening. The errors are lower for the stiffer materials, but can still be significant if care is not taken to establish the range of the surface detection error in a particular experimental situation. We have also examined the effect of pressure beneath the probe on the nanoindentation‐determined modulus of polystyrene with different probe geometries. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 414–428

Multivariate correlation analysis of outdoor weathering behavior of polypropylene under diverse climate scenarios

A full understanding on the relationships between weathering factors and deteriorations in the physical or mechanical properties of polymeric materials as well as their intercorrelations is critically important to forecast the durability of materials. In this work, the outdoor weathering behaviors of isotactic polypropylene (iPP) across a 1.5-year period under six typical climate scenarios in China are investigated. A wide sets of natural exposure conditions and test methods allow the establishment of the substantial correlations between chemical/physical structures and appearance/mechanical properties under simultaneous effects of multiple weathering factors (such as light, heat, oxygen etc.). The results under diverse natural environments suggest that the crystallinity and crack development depend largely on the molecular weight while the yellowing index correlates directly with the carbonyl index irrespective of the exposure conditions. The relationship between tensile strength and molecular weight is found to be in accord with an empirical linear model. Subsequently, using principal component analysis (PCA), a data reduction and visualization method, the degradation risk map of PP materials in China is established and the relative importance of relevant weathering factors is evaluated. Temperature is found to be the most dominant weathering factor on iPP aging under the climate scenarios investigated in the present work.

Influence of Operating Conditions on Structure and Physical Properties of Polymeric Materials

The changes in structure and physical properties of polymeric materials that exploited in a long time with complex mechanical loads used in pipe systems for high-pressure cold water have been studied. A significant reduction in the mechanical properties of polymeric materials has been established. The most typical structural defects that occur in polymer materials during manufacture and in the exploitations, using electron microscopic studies identified.

Ultra high stiffness and thermal conductivity of graphene like C3N

Recently, single crystalline carbon nitride 2D material with a C3N stoichiometry has been synthesized. In this investigation, we explored the mechanical response and thermal transport along pristine, free-standing and single-layer C3N. To this aim, we conducted extensive first-principles density functional theory (DFT) calculations as well as molecular dynamics (MD) simulations. DFT results reveal that C3N nanofilms can yield remarkably high elastic modulus of 341 GPa nm and tensile strength of 35 GPa nm, very close to those of defect-free graphene. Classical MD simulations performed at a low temperature, predict accurately the elastic modulus of 2D C3N with less than 3% difference with the first-principles estimation. The deformation process of C3N nanosheets was studied both by the DFT and MD simulations. Ab initio molecular dynamics simulations show that single-layer C3N can withstand high temperatures like 4000 K. Remarkably, the phononic thermal conductivity of free-standing C3N was predicted to be as high as 815 ± 20 W/mK. Our atomistic modelling results reveal ultra high stiffness and thermal conductivity of C3N nanomembranes and therefore propose them as promising candidates for new application such as the thermal management in nanoelectronics or simultaneously reinforcing the thermal and mechanical properties of polymeric materials.

Monitoring of the injection and holding phases by using a modular injection mold

Abstract Introducing pressure and temperature sensors into the mold cavity allows us to determine the rheological properties of the polymeric materials being processed. Furthermore, signals registered by sensors inside the mold cavity allow us to monitor the injection and holding phases as well as the subsequent solidification of the polymer melt. The aim of this research work was to verify the operational abilities of a laboratory injection mold with pressure and temperature sensors and was designed for research purposes. Standardized test pieces to investigate the mechanical properties of polymeric materials were obtained by using a laboratory injection mold. This article presents the investigation results of the influence of microcellular foaming of polyamide on the conditions inside an injection mold cavity. Apparent viscosity fluctuations of polymer melt in subsequent processing cycles were investigated as well. Additionally, the effect of changes in the injection speed of the polypropylene melt on its rheological parameters were investigated.

67: FABRICATION OF SMART SELF-EXPANDING BIOCOMPATIBLE STENTS IN BODY TEMPERATURE

Stent implantation has attracted significant attention since the urgent need of coronary angioplasty as the most common cause of heart attacks. Shape memory materials are able to have two shapes...

The Behaviour of Cross-Linking Filled PA66 by Micro-Indentation Test

The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Micro-mechanical changes in the surface layer of glass-fiber filled PA 66 modified by beta radiation were measured by the Depth Sensing Indentation - DSI method on samples which were non-irradiated and irradiated by different doses of the β - radiation. The specimens were prepared by injection technology and subjected to radiation doses of 0, 33, 66 nad 99 kGy. The change of micro-mechanical properties is greatly manifested mainly in the surface layer of the modified polypropylene where a significant growth of micro-hardness values can be observed. Indentation modulus increased from 1.8 to 3.0 GPa (increasing about 66%) and indentation hardness increased from 87 to 157 MPa (increasing about 80%). This research paper studies the influence of the dose of irradiation on the micro-mechanical properties of semi-crystalline polyamide 66 filled by 30% glass fiber at room temperature. The study is carried out due to the ever-growing employment of this type of polymer.

Exceptional enhancement of ductility and toughness in poly(vinylidene fluoride)/carbon nanotubes composites

ABSTRACTThe reinforcement of mechanical properties of polymeric materials is often important for widening their applications; however, it remains a technical challenge to effectively increase toughness without degrading stiffness and strength of the polymers. In this work, by a facile methodology combining solution mixing and melt blending, poly(vinylidene fluoride)/multi‐walled carbon nanotubes (PVDF/MWCNTs) composite with exceptionally enhanced ductility and toughness are prepared. With only 0.2 wt % CNT loading, the elongation at break has increased from originally 138% to almost 500%, while toughness improved by as much as 386%, without compromising the stiffness and strength. Note that raw CNTs are directly dispersed in the matrix without any surface modification. In order to elucidate this novel enhancement of ductility of PVDF/MWCNTs composites, we carried out detailed analyses based on results from ultra‐small‐angle X‐ray scattering (USAXS), cryo‐fractured surface morphology, differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). It is proposed that the enhanced ductility are contributed by a synergistic combination of “void pinning effect” of CNT, as well as the formation of γ phase polymorph as the interphase in the PVDF/CNTs composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43610.

Highly robust crystalsome via directed polymer crystallization at curved liquid/liquid interface.

Lipids and amphiphilic block copolymers spontaneously self-assemble in water to form a plethora of micelles and vesicles. They are typically fluidic in nature and often mechanically weak for applications such as drug delivery and gene therapeutics. Mechanical properties of polymeric materials could be improved by forming crystalline structures. However, most of the self-assembled micelles and vesicles have curved surfaces and precisely tuning crystallization within a nanoscale curved space is challenging, as the curved geometry is incommensurate with crystals having three-dimensional translational symmetry. Herein, we report using a miniemulsion crystallization method to grow nanosized, polymer single-crystal-like capsules. We coin the name crystalsome to describe this unique structure, because they are formed by polymer lamellar crystals and their structure mimics liposomes and polymersomes. Using poly(L-lactic acid) (PLLA) as the model polymer, we show that curved water/p-xylene interface formed by the miniemulsion process can guide the growth of PLLA single crystals. Crystalsomes with the size ranging from ∼148 nm to over 1 μm have been formed. Atomic force microscopy measurement demonstrate a two to three orders of magnitude increase in bending modulus compared with conventional polymersomes. We envisage that this novel structure could shed light on investigating spherical crystallography and drug delivery.

Fabrication of multifunctional graphene decorated with bromine and nano-Sb2O3 towards high-performance polymer nanocomposites

Despite great advances, it remains highly attractive but challenging to create high-performance polymeric materials combining excellent flame-retardancy and outstanding thermal, mechanical and electrical properties. We herein demonstrate a novel strategy for fabricating a multifunctional nano-additive (Br–Sb2O3@RGO) based on graphene decorated with bromine and nano-Sb2O3. Cone calorimetric tests show that incorporating 10 wt% Br–Sb2O3@RGO into thermoplastic polyurethane (TPU) strikingly prolongs the time to ignition and decreases the peak heat release rate by 72%. Besides, tensile strength and Young's modulus are enhanced by 37% and 820%, respectively. Meanwhile, the electric conductibility is increased by eleven orders of magnitude relative to the TPU matrix. This work provides a promising strategy for addressing the critical bottleneck with the existing flame retardants that only enhance flame retardancy at the expense of mechanical properties of polymeric materials. As-prepared high-performance TPU composites are expected to find many applications, especially in aerospace, tissue engineering, and cables and wires.

Micromechanical Properties of Glass-Filled Polyamide 6

The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Micromechanical changes in the surface layer of glass-filled PA-6 modified by beta radiation were measured by instrumented test of microhardness. The specimens were prepared by injection technology and subjected to radiation doses of 0, 66, 99, 132 kGy. Measurements of microhardness showed considerable changes of behavior of surface layer in middle as well as high radiation doses with higher values of indentation hardness and stiffness.

Micromechanical Properties of Thermoplastic Elastomer (TPE-E)

The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Micromechanical changes in the surface layer of Thermoplastic elastomer (TPE-E) modified by beta radiation were measured by instrumented test of microhardness. The specimens were prepared by injection technology and subjected to radiation doses of 0, 66, 99, 132 kGy. Measurements of microhardness showed considerable changes of behavior of surface layer in middle as well as high radiation doses with higher values of indentation hardness and stiffness.

Influence of Content of Crosslinking Agent on the Micromechanical Properties of Glass-Filled Polyamide 6

The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Some types of polymers do not cross-link during radiation crosslinking but degrade. In order to create 3D net in the polymer structure it is necessary to add a crosslinking agent. The specimens were prepared by injection technology with the TAIC crosslinking agent at 0, 1, 2 and 3 %. The changes of micromechanical properties of the surface layer were measured by instrumented microhardness test. It was found that micromechanical properties of the surface layer of the tested polyamide changed.

Energy dissipation and recovery in a simple model with reversible cross-links

Reversible cross-linking is a method of enhancing the mechanical properties of polymeric materials. The inspiration for this kind of cross-linking comes from nature, which uses this strategy in a large variety of biological materials to dramatically increase their toughness. Recently, first attempts were made to transfer this principle to technological applications. In this study, Monte Carlo simulations are used to investigate the effect of the number and the topology of reversible cross-links on the mechanical performance of a simple model system. Computational cyclic loading tests are performed, and the work to fracture and the energy dissipation per cycle are determined, which both increase when the density of cross-links is increased. Furthermore, a different topology of the bonds may increase the work to fracture by a factor of more than 2 for the same density. This dependence of the mechanical properties on the topology of the bonds has important implications on the self-healing properties of such systems, because only a fast return of the system to its unloaded state after release of the load ensures that the optimal topology may form.

Revealing the supramolecular nature of side-chain terpyridine-functionalized polymer networks.

Nowadays, finely controlling the mechanical properties of polymeric materials is possible by incorporating supramolecular motifs into their architecture. In this context, the synthesis of a side-chain terpyridine-functionalized poly(2-(dimethylamino)ethyl methacrylate) is reported via reversible addition-fragmentation chain transfer polymerization. By addition of transition metal ions, concentrated aqueous solutions of this polymer turn into metallo-supramolecular hydrogels whose dynamic mechanical properties are investigated by rotational rheometry. Hence, the possibility for the material to relax mechanical constrains via dissociation of transient cross-links is brought into light. In addition, the complex phenomena occurring under large oscillatory shear are interpreted in the context of transient networks.

Anomalous glass transition behavior of SBR–Al2O3 nanocomposites at small filler concentrations

Elastomers filled with hard nanoparticles are of great technical importance for the rubber industry. In general, fillers improve mechanical properties of polymer materials, e.g. elastic moduli, tensile strength etc. The smaller the size of the particles, the larger is the interface where interactions between polymer molecules and fillers can generate new properties. Using temperature-modulated differential scanning calorimetry and dynamic mechanical analysis, we investigated the properties of pure styrene-butadiene rubber (SBR) and SBR/alumina nanoparticles. Beside a reinforcement effect seen in the complex elastic moduli, small amounts of nanoparticles of about 2 wt% interestingly lead to an acceleration of the relaxation modes responsible for the thermal glass transition. This leads to a minimum in the glass transition temperature as a function of nanoparticle content in the vicinity of this critical concentration. The frequency dependent elastic moduli are used to discuss the possible reduction of the entanglement of rubber molecules as one cause for this unexpected behavior.

The Application of Polymer Materials with High Mechanical Properties in Competitive Sports

With the development of science and technology, the requirements on the properties of new materials was increasing, polymer materials become one kind of important material type which has been widely used in the current human social activity. Due to its high properties such as strength, elasticity and toughness, polymer materials with high mechanical properties’ application in the field of competitive sports has incomparable advantages. This paper analyzes the characteristics of high mechanical properties of polymer materials and its advantage in competitive sports, in order to promote its application in the field of sports.

Strapped porphyrin-based polymeric systems

Inspired by functional systems in nature, chemists have created a number of intriguing and useful molecular systems from porphyrins and their metal complexes. Of the synthetic porphyrin derivatives developed to date, strapped porphyrins are unique because they have three-dimensional architectures based on a built-in two-dimensional porphyrin molecule. Consequently, the structures of strapped porphyrins can be customized through detailed molecular design, thereby allowing the synthesis of sophisticated molecular systems. Herein, we describe strapped porphyrin-based polymeric systems. In particular, we focus on molecular design concepts that are established in combination with photophysical, electronic and mechanical properties of polymeric materials. Inspired by functional systems in nature, chemists have created a number of intriguing and useful molecular systems from porphyrin derivatives. Of the synthetic porphyrin derivatives developed to date, strapped porphyrins are unique because they have three-dimensional architectures based on a built-in two-dimensional porphyrin molecule. Consequently, the structures of strapped porphyrins can be customized through detailed molecular design, thereby allowing the synthesis of sophisticated molecular systems. Herein, we describe strapped porphyrin-based polymeric systems with a particular focus on molecular design concepts that have led to unique photophysical, electronic and mechanical properties.