Mechanical Properties Of Polymeric Materials Research Articles

Obtaining unsaturated polyester resins using products of recycled polyethylene terephthalate solvolysis

A technique for obtaining an unsaturated polyester resin based on recycled polyethylene terephthalate has been developed. The process of curing an unsaturated polyester resin under the action of styrene, a peroxide compound (Butanox 50M) and an accelerator (cobalt ortoate) has been studied. The physical and mechanical properties of polymeric materials based on the developed resin have been studied, it was found that their strength depends on the mass fraction of recycled polyethylene terephthalate in the oligoether polyol used in the synthesis.

Exploiting Waste towards More Sustainable Flame-Retardant Solutions for Polymers: A Review.

The development of sustainable flame retardants is gaining momentum due to their enhanced safety attributes and environmental compatibility. One effective strategy is to use waste materials as a primary source of chemical components, which can help mitigate environmental issues associated with traditional flame retardants. This paper reviews recent research in flame retardancy for waste flame retardants, categorizing them based on waste types like industrial, food, and plant waste. The paper focuses on recent advancements in this area, focusing on their impact on the thermal stability, flame retardancy, smoke suppression, and mechanical properties of polymeric materials. The study also provides a summary of functionalization methodologies used and key factors involved in modifying polymer systems. Finally, their major challenges and prospects for the future are identified.

Identification method on the vibration properties of a periodic core sandwich: Thermal impact on the band gap

This paper focuses on the thermal impact of filtering properties on sandwich structures with periodic core. The evolution of the bandgap is carefully studied as a function of temperature. Sandwich structure allows to shear the viscoelastic core layer and increases passive damping. Two polymers are selected for their viscoelastic properties and their adhesion properties with metal surfaces. The mechanical properties, shear modulus G(ω) and loss factor η(ω) of these polymers, are determined at temperature by an inverse method. The periodicity of the sandwich structure is achieved by alternating two materials with specific viscoelastic properties in the core, allowing resonant frequencies to be located in beams creating frequency ranges without resonant peaks. Temperature has a strong influence on the mechanical properties of polymer materials. This is why we felt it was important to be able to carry out a temperature investigation. Numerical finite element modelling is developed considering periodicity and temperature. Periodic sandwich fabricated in our laboratory are tested under thermal conditioned. The results show the importance of considering the effect of temperature. It has a direct impact on the filtering properties obtained by periodic structures.

Enhancing the Toughness and Strength of Polymers Using Mechanically Interlocked Hydrogen Bonds.

The energy dissipative features of hydrogen bonds under conditions of mechanical strain have provided an ongoing incentive to explore hydrogen bonding units for the purpose of controlling and customizing the mechanical properties of polymeric materials. However, there remains a need for hydrogen bond units that (1) possess directionality, (2) provide selectivity, (3) dissipate energy effectively, and (4) can be incorporated readily into polymeric materials to regulate their mechanical properties. Here, we report mechanically interlocked hydrogen bond units that incorporate multiple hydrogen bonds within a [2]catenane structure. The conformational flexibility and associated spatial folding characteristics of the [2]catenane units allow for molecular scale motion under external stress, while the interlocked structure serves as a pivot that maintains the directionality and selectivity of the resultant hydrogen bonding units. When incorporated into polymers, these interlocked hydrogen bond motifs serve to strengthen and toughen the resulting materials. This study not only presents a novel hydrogen bond unit for creating polymeric materials with improved mechanical properties but also underscores the unique opportunities that mechanically interlocked hydrogen bond structures may provide across a diverse range of applications.

Four-dimensional printing of continuous glass fiber-reinforced thermoplastics

Shape memory polymers (SMPs) are a new class of materials in which their shapes can be changed over time. Despite their lightness and ease of fabrication, SMPs have very low recovery forces and are therefore inefficient when high loads are applied. To improve the mechanical properties of polymeric materials, glass fiber (GF) is commonly used as a reinforcement. The purpose of this study was to demonstrate a four-dimensional (4D) printing process using material extrusion additive manufacturing on both polylactic acid (PLA) and thermoplastic polyurethane (TPU). The goal was to improve the recovery forces in SMPs. GF roving was fed continuously into the nozzle of a three-dimensional (3D) printer to fabricate composite specimens. Also, multi-layer PLA/TPU specimens were printed. There was a measurement of shape fixity, shape recovery, and force recovery ratios. A multi-objective function analysis was performed to determine the optimum material based on recovery force priority in this study. In terms of recovery force, GF showed a superior effect. For composite specimens, shape fixity and recovery ratios decreased and increased, respectively. According to the result of optimization, PLA with 6.62 % GF proved to be the best material. PLA's recovery force has been improved by annealing heat treatment. Furthermore, cyclic experiments up to three cycles were conducted to evaluate the performance of the optimum material.

Degradation of Mechanical Properties of A-PET Films after UV Aging.

In 2018, the European Commission adopted the European Strategy for Plastics in a Circular Economy, which outlines key actions to reduce the negative impact of plastic pollution. The strategy aims to expand plastic recycling capacity and increase the proportion of recycled materials in plastic products and packaging. Using recycled plastic can save 50-60% energy compared to virgin plastic. Recycled PET can be used in the production of A-PET films, which are predominantly used in thermo-vacuum forming for food packaging. Storage conditions can influence the mechanical properties of polymer materials. This work presents changes in the mechanical properties of A-PET films after UV irradiation. An experimental investigation of the UV aging of A-PET films was conducted in a UV aging chamber. The specimens were exposed to a UV radiation dose rate of 2.45 W/m2 for 1, 2, 4, 8, 16, 24, 32, and 40 h. UV measurements were also taken on a sunny day to compare the acceleration of UV irradiation in the UV aging chamber. Mechanical tensile tests were performed on two different three-layer A-PET films (100% virgin and 50% recycled). The tensile strength and relative elongation of the A-PET films were determined, and the work required to break the film was calculated. The total consumed work was divided into the work needed for elastic and plastic deformations. A study of the UV aging of A-PET films confirmed a significant effect on the films, including a loss of plasticity even after brief exposure to solar irradiance. The results of the puncture impact test further confirmed the deterioration of the mechanical properties of A-PET material due to exposure to UV radiation, with a greater effect observed for the recycled material.

In-situ measurement of dynamic micro X-ray CT and dynamic mechanical analysis for rubber materials

Observing the internal state that takes place during deformation is essential for comprehending the mechanical properties of polymeric materials like rubber. For the effective utilization of rubber in damping applications, it is imperative to comprehend the relationship between the loss factor and microstructure. In an earlier study, we developed a dynamic X-ray CT technique tailored for damping materials subjected to tensile amplitude and proposed a method to directly evaluate the internal deformation behavior under dynamic conditions. However, owing to the technical constraints of the shaker employed for dynamic X-ray computed tomography, key variables such as vibration frequency and amplitude could not be incorporated into the analysis. Additionally, it has not been possible to simultaneously measure dynamic viscoelasticity and dynamic micro X-ray CT in situ.In this study, we developed an experimental system that enables simultaneous measurement of dynamic mechanical properties and dynamic X-ray computed tomography (CT). This system facilitates in-situ investigation of internal deformation behavior and the loss factor in rubber materials, allowing for the assessment of variations in loss factors at the micro-scale. We examined the differences between styrene butadiene rubber (SBR) and natural rubber (NR) as base materials and investigated the influence of shape, and particle size of ZnO on the dynamic behavior of SBR composites. Dynamic X-ray computed tomography (CT) was conducted at excitation frequencies of 1 and 2 Hz, excitation amplitudes corresponding to 1% and 1.25% of the inter-chuck distance of the specimens, and a spatial resolution of 0.5 µm. Local strains were extracted from the 3D reconstructed images, and both the local strain amplitudes and their histograms were assessed as characteristics of dynamic behavior. The results indicated that the effect of varying the excitation frequency between 1 and 2 Hz was minimal for the SBR. Additionally, the median value of local strain amplitudes shifted in relation to the magnitude of the excitation amplitude. When comparing base materials (SBR and NR) with significantly different loss factors, no discernible differences were observed in the histograms of local strain amplitudes. The histograms did vary based on the formulation conditions of the SBR microparticle composite, although the loss factor remained unchanged. This lack of change in the loss factor can be attributed to the minimal impact of the particulate composites on the inherent loss factor of pure SBR. Importantly, the study successfully achieved multimodal and simultaneous measurements using dynamic mechanical analysis and dynamic micro X-ray CT.

DIELECTRIC SPECTROSCOPY METHOD FOR POLAR POLYMERS ELASTIC PROPERTIES DIAGNOSTICS

The mechanical properties of polymer materials are changes under the complex influence of such climatic factors as, for example, solar radiation, temperature changes, high humidity, and the impact of microorganisms – destructors. The methods of non-invasive diagnostics have to be used for changes prediction of the polymers materials products mechanical properties. The dielectric spectroscopy possibility using for diagnosing the modulus of elasticity of polymeric materials is considered in that paper. The results of elasticity modulus investigation by the dielectric spectroscopy using the DiMarzio–Bishop model and the mechanical measurements method are considered and compared in that paper. The results of dielectric and mechanical properties of polymers samples (polymethylmethacrylate, polycarbonate and polyvinylchloride) investigation are considered in that paper. These polymers are polar, so their mechanical properties in the elastic region of deformations can be investigate by dielectric spectroscopy method. This is due to the fact that the elastic deformations of a polymer are determined by the deformation of its macromolecules. It is show, that there are qualitative agreements between results of that measurement and the DiMarzio–Bishop model have to be refinement. The dipoles are represented as a spheres and interaction between dipoles are neglected in the DiMarzio–Bishop model. In our opinion, the interaction between dipoles in polymeric macromolecules is inevitable, and the configuration of dipoles differs from spherical. The necessity of using the calibration coefficient in the DiMarzio–Bishop model is shown by comparing the results of elastic modulus experimental measurements by the mechanical method and the dielectric spectroscopy method. This calibration factor takes into account the average number of dipoles in a macromolecule with a coefficient proportionality ∼6,7⋅10–5.

Thermal and mechanical properties of polymeric materials for automotive applications using molecular dynamics simulation

In the development of next-generation eco-friendly vehicles, it is crucial to measure the properties of polymeric materials under standardized conditions due to potential deterioration caused by factors such as temperature, humidity, and the driving environment. In this study, we used molecular dynamics simulation to analyze the thermal and mechanical properties of three polymers (PC, PMMA, and PBT) that are commonly used in automobile headlights. The densities of the polymers were measured and found to be similar to experimental values, with PBT showing a slightly larger deviation due to its relatively high crystallinity compared to the other two polymers. The glass transition temperatures of the polymers were measured using the same cooling rate, and the results followed the order of PC, PMMA, and PBT. Similarly, Young's moduli of the polymers were measured using the same strain rate, with the results following the order of PMMA, PC, and PBT. This approach enables the comparison of polymer properties under standardized conditions, ensuring accurate and reliable comparisons. Moreover, our research has the potential to make a significant contribution to the development of a molecular dynamics (MD) simulation protocol for the efficient generation of polymeric material properties. Such a protocol would greatly support experimental measurements in the automobile industry.

Small change, big impact: Simply changing the substitute on Si atom towards significant improvement of flame retardancy and toughness of epoxy resins

Enhancing simultaneously the flame retardancy and mechanical properties of polymer materials is a good expectation but always a tough challenge. In this work, two multifunctional compounds: phosphaphenanthrene/vinylsiloxane (DDVS) and phosphaphenanthrene/phenylsiloxane (DDPS) were synthesized, and both effectively improved the flame-retardant properties, toughness and UV shielding performance of epoxy resins (EPs) with high transparency. It was further found that the flame retardancy and toughness of EPs were greatly affected by simply changing the substituents from phenyl to vinyl groups on Si atom. Compared with DDPS, DDVS with vinyl group on Si showed more efficiency in improving flame retardancy (higher LOI value), self-extinguishing properties (higher UL 94 grade) and higher quality retention (more carbon residue) in EP. For example, DDVS was added in two-thirds of the amount of DDPS to make EPs achieve UL94 V-0 rating. This attributed to the high-temperature self-crosslinking of unsaturated carbon-carbon double bonds in DDVS, which can increase the charring ability of EPs and form more high-temperature stable char residues. Meantime, this also inhibited the release of volatile phosphorus-containing pieces from DDVS decomposition and retained more P in condense phase, thus improving the compactness and graphitization degree of char layers. The introduction of unsaturated bonds strengthened the condense-phase flame-retardant function of DDVS in EP, while retaining the original gas-phase flame-retardant actions of DOPO groups. The mechanism of gas-phase and condensed-phase mechanisms cooperated with each other, obtaining better flame retardant effect. Meanwhile, DDVS possessed greater efficiency than DDPS in increasing the fracture toughness of matrix due to the difference of steric hindrance between the substituents on silicon. Furthermore, the introduction of DDVS and DDPS did not significantly affect the transparency of EPs and the high visual transparency of materials was still maintained. In brief, the coordination design of phosphaphenanthrene and vinylsiloxane groups provided a theoretical basis to simultaneously improve the flame retardancy and toughening of EPs without losing glass transition temperature, while maintaining the high visual transparency of EPs with good UV shielding performance.

물 흡수에 따른 다양한 고분자 재료의 기계적/트라이볼로지적 물성 연구

The physical, chemical and mechanical properties of polymer materials used in water environment for a long time will change due to their water absorption characteristics, which will affect their tribological properties. This work studied the changes of physicochemical, mechanical, and tribological properties for five kinds of polymer materials (polyethylene, polyformaldehyde,polyamide, polytetrafluoroethylene, and poly-ether-etherketone) before and after water absorption. The mechanism of water absorption for polymer materials was revealed by molecular dynamics simulation. The results show that the higher the water absorption of polymer, the larger the swelling volume, the more the surface hardness and compressive strength decrease, and the toughness and friction coefficient of the material increase obviously. The water absorption status of polymer materials is closely related to the polarity of molecular chain. Water molecules are easy to form hydrogen bonds with polymer molecular chains of high polarity, which is the main factor of water absorption.

Physical and mechanical properties of polymer materials with different types of structures based on EVA and rice straw powder

The results of investigation of dependence of physical and mechanical characteristics of disperse-filled polymer composite materials (DFPCM) based on EVA grade 11306-075 and rice straw powder with particle size of ~ 250 microns (RSP) on generalized parameters of their structure are presented. The calculation of the generalized parameters and the classification of DFPCM according to the type of structures were carried out.It has been shown that when filling EVA grade 11306–075 with RSP particles, depending on the type of structure, the tensile strength of DFPCM decreases by ~ 2 times (from 9.4 to 4.51 MPa), the tensile strain by more than ~ 10 times (from 275 up to 8%), and the value of the tensile modulus increases by ~ 18 times (from 42 to 750 MPa).To obtain DFPCM based on EVA filled with rice straw powder with optimal physical and mechanical properties, it is recommended to introduce RSP in the concentration range from 0.18 to 0.45 vol.p.

Highly Tough and Reliable Poly(Amic Acid) with Ballistic Impact-Resistance through Modulation of Hydrogen Bonding Interactions.

Poly(amic acid) (PAA) materials as the precursor of polyimide generally show remarkably poor mechanical properties, thus limiting their application as the engineering plastics. In this study, it is demonstrated that the mechanical properties of PAA materials can be improved significantly for tens of folds with breaking strength >50MPa, Young's modulus >400MPa, and elongation at break >300% by incorporation of 20% (mol%) poly(propylene glycol) (PPO) soft segments. The optimization for suitable hard-soft composition with 20% PPO and the existence of various hydrogen bonds with different binding energies can dissipate energies efficiently, which simultaneously improve the material strength and toughness. In addition, PAA82 films exhibit excellent tolerance toward cyclic stretch, and have the capability to resist various harsh conditions including solar radiation testing (1sun), heat (85°C), alkalinity (pH 10), and acidity (pH 4) over one month. Noted that PAA82 films can be laminated with Kapton films, which show excellent resistance to ultrahigh (200°C) and ultralow temperature (-196°C). The laminated film also exhibits bulletproof property with a thickness of 6mm. The strategy via modulation of hard-soft compositions and hydrogen bonds in PAA materials shows great potentials to improve the mechanical properties of polymeric materials.

A Novel Design of Constant Load Creep Test Machine

Polymer materials have been used in a wide area from our homes to industry today. For this reason, creep curves from the mechanical properties of polymer materials are an important factor for the correct use of polymers. This article presents a new constant load creep test machine design which is a mechatronic system to perform creep testing of polymers. A low-cost creep test machine was developed by mounting clamps, pulleys, weights and steel cable on top of a main frame. With the measurement unit, the linear movement of the steel cable was detected and recorded with the data logging system together with the ambient temperature. Tests were made with a 15% calcium carbonate reinforced polypropylene specimen. It was observed that the experimental data obtained were compatible with a standard creep test curve. These findings confirm that the presented constant load creep test machine design works efficiently.

Influence study of thermostabilizers on the properties of cellulose triacetates

In the chemical and petrochemical industry, the primary focus for workers in the upcoming years is to develop innovative and secure technologies and equipment that comply with stringent quality standards. This imperative encompasses the production of materials, devices, and other products that meet the highest global benchmarks in technical and economic aspects. Emphasizing the implementation of progressive technologies and advanced production methods is crucial for achieving substantial improvements in labor productivity across all sectors of the national economy, with special attention paid to the chemical industry. This paper work presents the results of a study on increasing the thermal stability of cellulose triacetate by introducing stabilizers into its composition. Regularities of plasticization of cellulose triacetate with low- and high-molecular compounds have been established. As a result, the deterioration of the physical and mechanical properties of polymer materials processed at high temperatures occurs due to thermo-oxidative degradation, which leads to changes in the composition of the main polymer chain and a decrease in molecular weight. The application of stabilizers is proposed to prevent this process at high temperatures.

Mechanical Properties of Polylactide Filled with Micronized Chalcedonite

One of the methods of changing the mechanical properties of polymeric materials is by the creation of composites with various substances whose task is to strengthen and fill them. Thanks to the use of fillers, we can obtain new materials with interesting mechanical and chemical properties. Among the materials obtained, some of the features are often improved, while the others deteriorate. In this study, an attempt was made to obtain a polymer composite based on a PLA filled with macaroni chalcedonite in the amount of 5%, 10%, 15%, 20% and 30% by weight. The properties of the mechanically obtained mixtures were assessed. The tests show that the number of substances in the composite had a significant effect on changing the properties of the obtained material.

Investigation of the Flame Retardant Properties of High-Strength Microcellular Flame Retardant/Polyurethane Composite Elastomers.

Flame retardants (FRs) often reduce the mechanical properties of polymer materials, and FR/microcellular polyurethane elastomer (MPUE) composite materials have not been systemically studied. Hence, we conducted this study on FR/MPUE composites by using multiple liquid FRs and/or expandable graphite (EG). Compared with liquid flame retardants, the LOI of an expandable graphite/dimethyl methylphosphonate (EG/DMMP) (3:1) combination was significantly increased (~36.1%), and the vertical combustion grade reached V-0 without a dripping phenomenon. However, the corresponding tensile strength was decreased by 17.5%. With the incorporation of EG alone, although the corresponding LOI was not a match with that of DMMP/EG, there was no droplet phenomenon. In addition, even with 15 wt% of EG, there was no significant decline in the tensile strength. Cone calorimeter test results showed that PHRR, THR, PSPR, and TSR were significantly reduced, compared to the neat MPUE, when the EG content surpassed 10 wt%. The combustion process became more stable and thus the fire risk was highly reduced. It was found that flame retardancy and mechanical properties could be well balanced by adding EG alone. Our proposed strategy for synthesizing FR/MPUE composites with excellent flame retardancy and mechanical properties was easy, effective, low-cost and universal, which could have great practical significance in expanding the potential application fields of MPUEs.

Robust and Dynamic Polymer Networks Enabled by Woven Crosslinks.

Crosslinking plays a crucial role in determining mechanical properties of polymer materials. Although various crosslinks based on covalent or noncovalent bonds have been adopted, it remains an enormous challenge to develop a crosslink which could endow corresponding polymer network with robust yet dynamic properties. Herein, we report a crosslink simultaneously having dynamic property and woven geometry, and the polymer network with woven crosslinks (WPN) could integrate the merits of covalent polymer network (CPN) and supramolecular polymer network (SPN). In specific, the WPN not only exhibits comparable stiffness, strength, elastic recovery, and anti-fatigue property to those of CPN, but also possesses decent mechanical adaptivity and ductility, similar to those of SPN. Particularly, its toughness and puncture resistance are much superior to those of the others. Besides, the dynamicity of woven crosslink also imparts good performances of self-healing and processability to WPN.

Robust and Dynamic Polymer Networks Enabled by Woven Crosslinks

AbstractCrosslinking plays a crucial role in determining mechanical properties of polymer materials. Although various crosslinks based on covalent or noncovalent bonds have been adopted, it remains an enormous challenge to develop a crosslink which could endow corresponding polymer network with robust yet dynamic properties. Herein, we report a crosslink simultaneously having dynamic property and woven geometry, and the polymer network with woven crosslinks (WPN) could integrate the merits of covalent polymer network (CPN) and supramolecular polymer network (SPN). In specific, the WPN not only exhibits comparable stiffness, strength, elastic recovery, and anti‐fatigue property to those of CPN, but also possesses decent mechanical adaptivity and ductility, similar to those of SPN. Particularly, its toughness and puncture resistance are much superior to those of the others. Besides, the dynamicity of woven crosslink also imparts good performances of self‐healing and processability to WPN.

The Influence of Temperature on the Tensile Mechanical Properties of PPA

In the automotive industry and not only, more and more attempts are being made to replace parts made of metals with those made of plastics, due to their low weight and low manufacturing cost. Thus, a detailed knowledge of the mechanical properties of polymeric materials is a must. This paper presents a study of the influence of temperature on the tensile mechanical properties of semicrystalline polyphthalamide (PPA). Dog bone specimens were obtained by injection molding and, in order to eliminate the possible moisture absorbed in the place of storage of the specimens, they were subjected to a drying treatment in an airtight oven at a temperature of 80 degrees for 12 hours. The specimens were tested at 5 different temperatures (25, 40, 80, 120, and 160°C) with a loading speed of 5 mm/min. For each test temperature 3 specimens were used, according to the ISO 527-2 standard. With the data extracted from the experimental tests, the mechanical properties were calculated. Also, the force – displacement and stress – strain curves were plotted. After the experimental tests, it was concluded that the dry specimens are more resistant, and with increasing temperature, the PPA material changes from a brittle to a ductile behavior. Moreover, the main tensile properties decrease significantly with increasing temperature (the modulus of elasticity decreases by 66.8% from temperature of 25 °C to temperature of 160 °C).