Mechanical Properties Of Poly Research Articles

Enhanced flame retardancy and mechanical properties of poly (lactic acid) composites via piperazine pyrophosphate and nanoscale cerium dioxide synergistic flame retarding and uniaxial pre-stretching

The simultaneous improvement of flame retardancy and mechanical properties (including strength, rigidity, and toughness) of PLA was achieved for the first time. A synergistic flame retardant system including PAPP and nano-CeO2 was used to enhance the flame retardant properties of PLA. Especially, uniaxial pre-stretching was further used to improve the mechanical properties of the flame-retardant PLA composites. With the addition of just 1 wt% nano-CeO2, the flame retardant properties of PLA composite were significantly enhanced. Relative to pure PLA, the limiting oxygen index (LOI) of PLA/14 wt%PAPP/1 wt% nano-CeO2 increased from 20.2 % to 28.8 %, achieving a V-0 rating in the UL-94 test. Moreover, the peak heat release rate (PHRR) was reduced from 461KW/m2 to 230KW/m2. Notably, the flame-retardant PLA composites with excellent mechanical properties were achieved using uniaxial pre-stretching for the first time. After pre-stretching, the tensile strength, elongation at break and impact strength of the flame-retardant PLA were significantly increased to 79.82 MPa, 103.8 %, and 9.7 kJ/m2, respectively. This work proposes an ingenious strategy for significantly enhancing both the fire safety and mechanical properties of PLA composites.

Mechanical Properties of Epoxy Networks with Metal Coordination Bonds: Insights from Temperature and Molar Mass Variation.

We investigate the thermal and mechanical properties of poly(ethylene glycol), PEG, networks with either solely covalent epoxy bonds (single networks, SNs) or coexisting epoxy and iron-catecholate bonds (dual networks, DNs). The latter has recently been shown to be a promising material that combines mechanical strength with significant deformability. Here, we address the previously unexplored effects of the temperature and PEG precursor molar mass on the mechanical properties of the networks. We focus on PEG molar masses of 500 g/mol, where crystallization is suppressed, and 1000 g/mol, where some weak crystals are formed. SNs soften with an increasing PEG molar mass. Heating reversibly softens the DN, but it has a minimal effect on SNs. Nonlinear shear deformation of the DN breaks iron-catecholate bonds, and subsequent recovery upon shear cessation occurs to a long-time steady-state modulus whose value is almost triple the original one, likely due to the formation of tris-complexes versus initial sterically or kinetically trapped bis-complexation. The response under elongation indicates that the DN with sacrificial bonds is stiffer and more extensible than the other networks. These results may provide guidelines for designing dual networks with tunable mechanics at the molecular level.

Evolution of Physical, Thermal, and Mechanical Properties of Poly(methyl Methacrylate)-Based Elium Thermoplastic Polymer During Polymerization.

Elium-based thermoplastic composites are a key material for future use in the marine, wind energy, and automotive industries because of their recyclability and ease of manufacture. To optimize the processing of the Elium composites to yield optimal structural properties, computational process modeling can be used to relate processing parameters to residual stresses and material durability. The key ingredient for reliable and accurate process modeling is the evolution of physical, thermal, and mechanical properties during polymerization. The objective of this study is to use molecular dynamics to predict the mass density, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, glass transition temperature, and coefficient of thermal expansion as a function of the extent of reaction of the polymer. The predicted properties compare favorably to the experimentally measured values in the fully polymerized state. This data set of properties provides needed input data for process modeling of Elium-based composites for process parameter optimization and improved durability and performance.

Unraveling the Effect of Strain Rate and Temperature on the Heterogeneous Mechanical Behavior of Polymer Nanocomposites via Atomistic Simulations and Continuum Models.

Polymer nanocomposites are characterized by heterogeneous mechanical behavior and performance, which is mainly controlled by the interaction between the nanofiller and the polymer matrix. Optimizing their material performance in engineering applications requires understanding how both the temperature and strain rate of the applied deformation affect mechanical properties. This work investigates the effect of strain rate and temperature on the mechanical properties of poly(ethylene oxide)/silica (PEO/SiO2) nanocomposites, revealing their behavior in both the melt and glassy states, via atomistic molecular dynamics simulations and continuum models. In the glassy state, the results indicate that Young's modulus increases by up to 99.7% as the strain rate rises from 1.0 × 10-7 fs-1 to 1.0 × 10-4 fs-1, while Poisson's ratio decreases by up to 39.8% over the same range. These effects become even more pronounced in the melt state. Conversely, higher temperatures lead to an opposing trend. A local, per-atom analysis of stress and strain fields reveals broader variability in the local strain of the PEO/SiO2 nanocomposites as temperature increases and/or the deformation rate decreases. Both interphase and matrix regions lose rigidity at higher temperatures and lower strain rates, blurring their distinctiveness. The results of the atomistic simulations concerning the elastic modulus and Poisson's ratio are in good agreement with the predictions of the Richeton-Ji model. Additionally, these findings can be leveraged to design advanced polymer composites with tailored mechanical properties and could optimize structural components by enhancing their performance under diverse engineering conditions.

The Effect of Diphenylphosphate Intercalated Magnesium Aluminum Lanthanum Hydrotalcite on the Thermal Stability and Mechanical Properties of Poly(Vinyl Chloride)

The Effect of Diphenylphosphate Intercalated Magnesium Aluminum Lanthanum Hydrotalcite on the Thermal Stability and Mechanical Properties of Poly(Vinyl Chloride)

Influence of Green Chemical Treatments on Morphology and Mechanical Properties of Poly(3‐Hydroxybutyrate‐co‐3‐Hydroxyhexanoate)–Agave Americana Fibers Biocomposites

AbstractThis work aims at investigating the effect of two eco‐friendly chemical treatments of Agave Americana fibers (AAFs) on morphology and mechanical properties of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHBHHx) biocomposites prepared by melt compounding. Acid citric and sodium bicarbonate treatments are used separately to modify the fiber surface before their incorporation into PHBHHx matrix at 30 wt%. The study reveals through SEM observations that the fracture surface of untreated PHBHHx biocomposite shows a poor fiber‐matrix adhesion with the presence of many microvoids at interface and also some fibers pullout. However, less surface defects with a finer morphology are observed on the treated biocomposite samples resulting in improved tensile and flexural properties compared with neat polymer, being however, more pronounced for those modified with sodium bicarbonate. The study highlights the beneficial effect of the green treatments investigated to enhance the mechanical properties of PHBHHx biocomposites.

Mechanical Properties of Poly(vinyl alcohol) Hydrogels: Role of Chemical Crosslinks and Physical Junctions

Mechanical Properties of Poly(vinyl alcohol) Hydrogels: Role of Chemical Crosslinks and Physical Junctions

Effect of cellulose derivatives on crystallization and mechanical properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Abstract In this work, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was modified by cellulose derivatives, and the effects of different kinds of cellulose derivatives on the crystallization and mechanical properties of PHBV were investigated. The crystallization and mechanical properties of PHBV/cellulose derivatives composites were measured by means of differential scanning calorimeter, polarizing microscope, and mechanical properties testing instruments. Studies show that cellulose acetate (CA) can promote the crystallization of PHBV, a small amount of CA can significantly increase the crystallization temperature of PHBV. The crystallization rate of PHBV was also accelerated by CA. However, the addition of cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) decreased the crystallization temperature of PHBV and inhibited the nucleation of PHBV. And the degree of inhibition increased with the increase of CAB and CAP content. CAB and CAP have good compatibility with PHBV, CAB, and CAP can be uniformly dispersed in PHBV. Cellulose derivatives with specific component content can enhance the tensile properties of PHBV without losing the impact strength.

Improvement of Marine Biodegradability and Mechanical Properties of Poly(D-lactide) Films by Embedment of Poly(ethylene glycol)-Modified (PEGylated) Enzymes

Improvement of Marine Biodegradability and Mechanical Properties of Poly(<scp>D</scp>-lactide) Films by Embedment of Poly(ethylene glycol)-Modified (PEGylated) Enzymes

The study of degradation and mechanical properties of poly(lactic) acid (PLA) based 3D printed filament

Additive manufacturing, commonly known as 3D printing technology, has become one of the mainstream processes in the manufacturing industry due to its advantages over conventional manufacturing, which have piqued the public’s interest. This study aims to focus on the influence of thermal conditions on crystallization towards mechanical properties of 3D printed poly(lactic) acid (PLA) degradation samples with 100% infill. As for the degradation profile, the highest weight loss recorded by the samples was 0.7%, observed in samples buried in soil with an abiotic medium for one month. The exposure of degraded samples to high temperature during drying affected their crystallinity, resulting in significant changes in strains, particularly between week 1 and week 2, where strains dropped significantly from 7.33% to 4.28%, respectively. In conclusion, it has been demonstrated that degradation for PLA material still can occur in an abiotic medium, albeit at a slower rate compared to a biotic medium due to the presence of additional microorganisms and bacteria. Besides, the post-heat treatment process on PLA degradation samples affects their crystalline structure, resulting in significant changes in mechanical properties, particularly especially strains. Therefore, it can be concluded that different materials exhibit distinct mechanical properties.

A Macroscopic Interpretation of the Correlation between Electrical Percolation and Mechanical Properties of Poly-(Ethylene Vinyl Acetate)/Zn Composites.

Elastic composites were prepared using a procedure involving hot plates and zinc powder that was directly dispersed into an EVA matrix. The correlation between the zinc content and the conductive properties of the material was studied via impedance spectroscopy, the thermal properties of the material were studied via differential calorimetry and the mechanical properties of the composites were studied via tensile strength curves, representing an important advancement in the characterization of this type of composite material. The composites' tensile strength and elongation at break decrease with the addition of filler since zinc particles act as stress-concentrating centres, while the composites' hardness and Young's modulus increase because of an increase in the stiffness of the material. The AC perturbation across the EVA/Zn composites was characterized using an RC parallel equivalent circuit that allowed us to easily measure their resistivity (ρp) and permittivity (εp). The dependence of these electrical magnitudes on the zinc content is correlated with their mechanical properties across the characteristic time constant τp = ρp·εp of this equivalent circuit. The dependence of the mechanical and electrical magnitudes on the zinc content is consistent with the formation of percolation clusters. The addition of graphite particles increases their potential performance. Three possible mechanisms for the electrical transport of the ac-perturbation across the EVA/Zn composites have been identified. Chemical corrosion in acid media causes the loss of zinc surface particles, but their bulk physical properties practically remain constant.

Engineering Tough Supramolecular Hydrogels with Structured Micropillars for Tunable Wetting and Adhesion Properties.

Soft-lithography is widely used to fabricate microstructured surfaces on plastics and elastomers for designable physical properties such as wetting and adhesions. However, it remains a big challenge to construct high-aspect-ratio microstructures on the surface of hydrogels due to the difficulty in demolding from the gel with low strength and stiffness. Demonstrated here is the engineering of tough hydrogels by soft-lithography to form well-defined micropillars. The mechanical properties of poly(acrylamide-co-methacrylic acid) hydrogels with dense hydrogen-bond associations severely depend on temperature, with Young's modulus increasing from 8.1MPa at 15°C to 821.8MPa at -30°C, enabling easy demolding at low temperatures. Arrays of micropillars are maintained on the surface of the gel, and can be used at room temperature when the gel restores soft and stretchable. The hydrogel also exhibits good shape-memory property, favoring tailoring the morphology with a switchable tilt angle of micropillars. Consequently, the hydrogel shows tunable wetting and adhesion properties, as manifested by varying contact angles and adhesion strengths. These surface properties can also be tuned by geometry and arrangement of micropillars. This facile strategy by harnessing tunable viscoelasticity of supramolecular hydrogels should be applicable to other soft materials, and broaden their applications in biomedical and engineering fields.

Improved crystallization capability and mechanical properties of poly(l‐lactide) achieved by tailoring the grafted chain structure on graphene oxide

AbstractInterfacial interaction is crucial in modulating the microscopic morphology and macroscopic properties of composites. Generally, grafting polymer molecular chains on nanoparticles is an approach for enhancing the interfacial interaction, but the dependence of enhancement degree on molecular chain structure is not clear. In this work, nanosheets were obtained by grafting poly(d‐lactide) (PDLA) and poly(l‐lactide) (PLLA) molecular chains onto graphene oxide (GO), respectively, then PLLA‐based composites containing shallow loading (0.3 wt%) were obtained by melt‐blending. The findings indicated that grafting PDLA on the GO was more efficacious in enhancing the crystallization capability of PLLA, and the mechanism was primarily owing to stronger interfacial binding energy between the PLLA matrix and GO‐g‐PDLA, which was approximately 1.5 times that of the PLLA/GO‐g‐PLLA composite. Compared to the GO‐g‐PLLA nanosheets, GO‐g‐PDLA nanosheets exhibited apparent strengthening and toughening effect, and the composite sample exhibited significantly improved tensile strength and tensile ductility, with a respective increase of 21.5% and 52.2% compared with pure PLLA sample, respectively. Furthermore, all composite films (90 μm) maintain high transmittance close to 80%. This work further confirms that enhancing the interfacial binding energy by grafting PDLA molecular chains on nanoparticles is advantageous for enhancing both the crystallization and mechanical characteristics of the PLLA‐based composites.Highlights GO‐g‐PDLA and GO‐g‐PLLA were successfully synthesized. GO‐g‐PDLA showed more apparent nucleation effect in PLLA crystallization. GO‐g‐PDLA showed higher interfacial binding energy compared with GO‐g‐PLLA. Synchronously strengthening and toughening were achieved for PLLA/GO‐g‐PDLA.

Effect of Graphene Oxide Localization on Morphology Development and Rheological and Mechanical Properties of Poly(lactic acid)/ethylene vinyl Alcohol Copolymer Blend Composites: A Comprehensive Study.

This study investigates the rheological, morphological, and mechanical properties of melt-processed polylactide/ethylene vinyl alcohol (70PLA/30EVOH) blend composites containing 0.25, 0.5, and 1 wt.% of graphene oxide (GO) nanoplates. Thermodynamic-based suggested the localization of nanoparticles in EVOH, SEM studies showed that the introduction of GO to the blend increased dispersed droplet size, which was attributed to the localization of GO within EVOH, as confirmed by TEM. The rheology results indicated a decrease in the elasticity for the composite containing 0.25 wt.% of GO compared to the neat blend, which was attributed to the sliding effect of the added GO nanoplatelets. However, samples containing higher amounts of GO nanoplatelets exhibited more excellent elasticity than the neat blend. The increased elasticity was suggestively attributed to the dominance of hydrodynamic interactions, the physical network of added nanoplatelets, and polymer/GO interactions over the sliding role of the GO nanoplatelets at higher loadings. In addition, the effect of the order of mixing was investigated, and the premixing of PLA and GO exhibited a decrease in the droplet radius compared to the neat blend. It was ascribed to the localization of GO nanosheets in the PLA and interface, which was confirmed by rheological results and mechanical assessments.

Rheological, thermal, and mechanical properties of poly(butylene succinate) (PBS)/poly(L-lactide) (PLA) fiber biodegradable green composites

Rheological, thermal, and mechanical properties of poly(butylene succinate) (PBS)/poly(L-lactide) (PLA) fiber biodegradable green composites

Effect of chain extension on processability and mechanical properties of poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate)

AbstractPoly(3‐hydroxybutyrate‐4‐hydroxybutyrate) (P34HB) copolyester is a new type of biodegradable polymer material, but it cannot meet the market requirements because of its poor thermal stability. In this work, P34HB with a low degree of cross‐linking was successfully prepared by incorporating a small amount of a multiple epoxy chain extender, known as Joncryl ADR‐4380 (styrene‐methacrylic acid glycidyl ester copolymer), through reactive extrusion. The rheological properties, thermal stability, thermal behavior, and mechanical properties of the materials were investigated. Fourier transform infrared spectroscopy and gel content test showed that there was a significant chemical interaction between P34HB and ADR4380, and a cross‐linked structure was produced. Compared with pure P34HB, the samples after chain extension showed improved rheological properties, with increased viscosity and melt elasticity due to the formation of a gel network. Thermogravimetric analysis, dynamic time scanning experiment, and melt flow index (MFI) provided strong evidence for the enhanced of thermal stability of P34HB. The onset decomposition temperature of P34HB increased by 13.5°C, and its MFI decreased from 23.30 to around 5 at 170°C, and the complex viscosity remained relatively stable with time after modification. In terms of mechanical properties, the maximum elongation at break increased by 88.08% due to the improvement of toughness.

Glass Transition Temperature and Mechanical Properties of Poly(Ethylene Carbonate)/Organoclay Composites

Poly(ethylene carbonate) (PEC) is a form of aliphatic polycarbonate, a biodegradable polymer made via the copolymerization of carbon dioxide and epoxides. The poor thermal stability and mechanical properties of these aliphatic carbonates are attributed to the carbon structure's flexibility, which restricts their applications. By combining PEC with organoclay CP180, this study addressed the weaknesses of PEC with organoclay addition. A physical blending technique was employed to generate PEC/organoclay composites with a 10-50 wt.% ratio of organoclay. The blended material's thermal characteristics were analyzed using differential scanning calorimetry (DSC), and the mechanical characteristics were measured using a universal tensile machine. The Field Emission Scanning Electron Microscopy (FESEM) analysis determined the blends' morphology. Before the torque value for all curves grew with the addition of CP180 material to the PEC matrix, it became constant. It reached a high value due to the shear-thickening behavior of the PEC matrix with organoclay addition. Tg of PEC increased by more than 7°C by 40 wt.% organoclay addition, as evident in the hindrance of PEC flexibility, significantly increased the toughness of this PEC. From the FESEM images, the formation of large silicate starts to aggregate effectively, lowering the interfacial area between organoclay and PEC as the clay content continues to rise, as shown by 50 wt.% organoclay addition.

Mechanical properties of poly(N‐acryloyl‐glycinamide) hydrogels dependent on initiation number of the polymerization reaction

AbstractHydrogels with polymer networks formed through physical interactions have received attention because of their post‐moldability and self‐healing properties upon physicochemical stimulation. Although hydrogels become fragile without covalent crosslinking, poly(N‐acryloyl‐glycinamide) (PNAGA) hydrogels, which are formed through hydrogen bonding among PNAGA molecules, have recently demonstrated exceptional strain. In this study, we prepared a series of PNAGA hydrogels with different molecular weights and constant weight concentrations of PNAGA. Stress–strain tests demonstrated that higher molecular weights of PNAGA promote extensibility. The swelling ability of the hydrogel also increased with higher molecular weights of PNAGA, suggesting that high molecular weights of PNAGA significantly increase the tolerability of hydrogels to shape change, which opens up new possibilities for developing robust hydrogels without the requirement for cross‐linking. Although different behaviors were not observed with changes in the molecular weight, we achieved hydrogel re‐construction using the PNAGA powder obtained from hydrogels, which demonstrates an advantage of such polymer networks based on hydrogen bonding. Regarding the healing ability of the cut surfaces, hydrogels with a lower molecular weight exhibited higher recoveries, probably owing to the high PNAGA mobility in the hydrogels. Finally, this study elucidates the importance of controlling the molecular weight when developing functional hydrogels.

Poly(ethylene succinate-co-lactic acid) as a Multifunctional Additive for Modulating the Miscibility, Crystallization, and Mechanical Properties of Poly(lactic acid).

Polymer blending offers an effective and economical approach to overcome the performance limitations of poly(lactic acid) (PLA). In this study, a series of copolymers poly(ethylene succinate-co-lactic acid) (PESL) were synthesized, featuring lactic acid (LA) contents that ranged from 20 to 86 wt %. This synthesis involved a one-pot industrial melt polycondensation process using succinic acid (SA), ethylene glycol (EG), and LA, catalyzed by titanium tetraisopropoxide (TTP). The goal was to produce a fully biobased copolymer expected to exhibit partial miscibility with pure poly(lactic acid) (PLA). To assess the capability of PESL copolymers in toughening PLA, we conducted tensile testing on PLA/PESL blends containing 15 wt % PESL. As a result, an elongation at break for the blends with 15 wt % loading of the copolymer PESL72 was directly enhanced to 250% with an ultimate strength of 35 MPa, compared to brittle PLA with less 10% tensile length. The morphological features of interfacial adhesion before and after tensile failure were measured by scanning electron microscopy (SEM). A significant enhancement in the chain mobility of the PLA/PESL blends was further evidenced by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). These findings hold promise for the development of functional packaging materials based on PLA. The proposed copolymer design, which boasts strong industrial feasibility, can serve as a valuable guide for enhancing the toughness of PLA.

Influence of different dimensional nanoparticles on the properties of poly(β-hydroxybutyrate-co-valerate) nanocomposites

Abstract In order to study the effect of nanoparticle dimensions on the thermodynamic properties of PHBV and PHBV blends, one-dimensional cellulose nanocrystals (CNC), two-dimensional graphene, and zero-dimensional hydrophobic nano-silica were selected to regulate the crystallization and mechanical properties of poly(β-hydroxybutyrate-co-valerate) (PHBV) and PHBV blends. The morphology, crystallization process, mechanical property and rheological response of PHBV nanomaterials were analyzed. Experimental results show that the three selected nanomaterials all hinder the crystallization process of PHBV, among which two-dimensional graphene exhibits the most obvious hindrance. At the same time, two-dimensional graphene can improve the tensile strength and impact strength of PHBV. However, in the rheological response of PHBV nanocomposites, zero-dimensional hydrophobic nano-silica and one-dimensional cellulose nanocrystals show more obvious regulatory effects than two-dimensional graphene.