Decrease In Tensile Strength Research Articles

Fabrication of microcapsules with graphene/organic hybrid shell based on Pickering emulsions for self‐healing anti‐corrosive coatings

AbstractDuring the utilization of organic coatings, microcracks may arise as a result of external environmental influences and inherent aging, significantly diminishing the coating's lifespan. In this study, we employed the Pickering emulsion template method combined with interfacial polymerization to fabricate graphene oxide/polyurethane/polyaniline (GO/PU/PANI) organic–inorganic hybrid shell microcapsules utilizing isophorone diisocyanate (IPDI) as the core material. The capsules exhibited an average particle diameter of 3.11 μm and an encapsulation rate of 78.19%. Subsequently, these prepared capsules were incorporated into a photocurable resin to obtain a self‐healing corrosion‐resistant coating. Scanning electron microscopy analysis demonstrated that even with just 5% addition of microcapsules, nearly complete repair could be achieved. The tensile strength and flexural strength of the self‐healing material containing 5% microcapsules were measured at 84.8 MPa and 193 MPa respectively. These values represented only a marginal decrease in tensile strength by 2.75% and flexural strength by 5.39%, compared to the substrate without capsule addition. Remarkably, after immersing the repaired coating in a NaCl solution with a concentration of 5 wt% for up to 250 hours, the alternating current impedance value remained stable at approximately 6.9 × 105 Ω·cm2. This outstanding corrosion resistance can be attributed to synergistic effects between PANI and IPDI within the coating system, thereby expanding its potential applications under harsh conditions.

Tensile Deformation Behaviors and Microstructure Evolution Under Various Temperatures for MAR‐M247 Nickel‐Based Superalloy

The study aims to analyze the tensile behavior and microstructural changes in MAR‐M247 nickel‐based superalloy across different temperatures. Tensile behavior is examined under a constant strain rate of 2.5 × 10−4 s−1 at varying temperatures. Results indicate a temperature‐dependent nature of the alloy's tensile properties. At 550 °C, a Portevin–Le Chatelier effect is observed, attributed to twinning nucleation and carbon atom diffusion. Dynamic recrystallization occurs at 950 °C, manifesting in a sinusoidal stress–strain curve. At room temperature, the primary fracture mechanism involves dislocation shearing in the γ matrix, with minor dislocation shearing in the γ′ phase. At 550 °C, carbides along grain boundaries and the γ′ phase impede dislocation motion. Concurrently, dislocations shear the γ′ phase, leading to the formation of superlattice intrinsic stacking faults and Kear–Wilsdorf locks, thereby enhancing tensile strength. However, at 950 °C, dislocation motion primarily involves climb, carbides decompose, the γ′ phase softens and enlarges, resulting in a notable decrease in tensile strength.

Failure behaviour of frozen rock with double ice-filled flaws under Brazilian splitting tension

Geotechnical engineering in cold regions frequently involves dealing with frozen fractured rock masses, particularly in the activities of strip mining and tunnel support design, where tensile failure predominates as the main failure mode in stress-driven failures. Seasonal freezing can adversely affect the performance of rock masses. To investigate the tensile characteristics of frozen rock masses, marble specimens with double parallel ice-filled flaws were artificially frozen and subjected to Brazilian splitting experiments at a loading rate of 0.001 mm/s. The influence of the angle of the double coplanar flaws and the rock bridge angle of ice-filled flaws on the tensile behaviours were numerically studied by RFPA3D (3D Rock Failure Process Analysis), a finite element method specifically developed for simulating rock failure. Results showed that as the angle of the double parallel ice-filled flaws increases, tensile strength initially decreases and then increases. Furthermore, in specimens with the double coplanar ice-filled flaws, an increase in the angles of the flaws and rock bridge leads to a gradual decrease in tensile strength. The spatial distribution of ice-filled flaws is a crucial factor that influences the failure mode after split cracking occurs. The ice filling and bonding mechanism controls the tensile strength and cracking behaviour of frozen rock masses. The findings of this study provide valuable insights and serve as a theoretical foundation for designing blasting parameters and disaster prevention in strip mines located in cold regions.

Tailoring Microstructure and Mechanical Properties of Additively Manufactured Inconel 625 by Remelting Strategy in Laser Powder Bed Fusion

Tailoring Microstructure and Mechanical Properties of Additively Manufactured Inconel 625 by Remelting Strategy in Laser Powder Bed Fusion

Effect of temperature on the mechanical behavior of glass fiber reinforced with hollow glass particle-filled epoxy composites

The design of marine ships and aircraft components with hollow glass particle-filled fiber-reinforced composites demands an understanding of their performance under outdoor conditions. The continuous glass fiber-reinforced epoxy matrix filled with hollow glass particles in the range of 0–0.3 vol fraction was prepared by the compression molding machine. The influence of temperature exposure on the mechanical behavior of glass fiber-reinforced hollow glass particle composites was studied by conducting tensile and flexural tests. The temperature exposure varying from room temperature up to 60 °C was used to investigate the effect of service temperature on the hollow glass particle-filled fiber composite specimens. Differential scanning calorimetry (DSC) analysis was conducted to study the glass transition behavior of the composites. The incorporation of microspheres in the glass fiber composites gradually reduced the tensile and flexural strength, while their specific values increased as increasing the microspheres. The hollow glass particle-filled fiber composites tested at 60 °C exhibited a decrease in tensile and flexural strength compared with room temperature. As the température of the test spécimens was nearer to the glass transition value, the polymer chain was softened, leading to a reduction in strength. In contrast, the modulus values remain unaffected by increasing the temperature to 60 °C.

Mechanical properties and microstructure of high-strength and high-ductility steel at elevated temperature

This paper aims to investigate the mechanical behavior and microstructure of a novel high-strength and high-ductility (HSHD) steel at different temperatures ranging from 25 to 600 °C. The testing machine conducted uniaxial tensile tests with seven different temperatures. The true plastic stress-strain curves of HSHD steel were fitted using the Ludwigson model based on the experimental results, and the microstructure of HSHD steel was analyzed using Electron Backscatter Diffraction (EBSD). The experimental results revealed an obvious temperature-mechanical response relationship in HSHD steel, showing a gradual decrease in tensile strength and yield strength with increasing temperature, while the uniform and post-necking elongation exhibit a trend of decreasing and then increasing. Compared to other steels, HSHD steel exhibited significant advantages of strength-ductility balance over a wide range of temperatures. A Ludwigson model coupled with temperature parameters was established, which provided a good fitting effect to the true plastic stress-strain curves of HSHD steel. Microstructure analysis shows significant Brass and Copper textures near the fracture surface of HSHD steel at all temperatures. Additionally, a large number of deformation twinning was observed within the grain of HSHD steel. The excellent high-temperature mechanical properties of HSHD steel can be attributed to the strong thermal stability of deformation twins.

Effect of Varied Cure Temperature on the Cure Behavior, Mechanical Properties and Heat Build-Up of Solid Tire Tread Compound Containing Different Particles Sizes of Ground Tire Rubber

This work investigates the effect of variation in vulcanization temperature on the cure behavior, tensile properties, tear strength, hardness, Akron abrasion loss and heat build-up of vulcanized tire tread compound in which the total rubber was replaced with 10% and 20% ground tire rubber (GTR) of 40, 60 and 80 mesh sizes. The first step was the characterization of the GTR using optical microscopy and a thermogravimetric analyzer. The first step of mixing each rubber compound was carried out using an internal mixer (Brabender) at 60°C and 40 rev/min rotor speed and the second step was done on a two-roll mill. The mooney viscosity of each rubber compound was investigated. the cure behavior of the rubber compounds was studied at 140°C, 150°C, and 160°C respectively. Results show that the introduction of GTR reduced vulcanization time, while increased cure temperature resulted in a lower vulcanization time. No significant difference was observed in the vulcanization time at a particular temperature of the rubber sample with different particle sizes and varied amounts of GTR. The introduction of ground tire rubber in the rubber vulcanizate however resulted in decreased tensile strength, tear strength and elongation, and increased hardness, abrasion resistance, modulus and heat build-up. An increase in the vulcanization temperature from 140°C to 150°C and 160°C  did not impart a significant reduction in the tensile strength of the vulcanizates containing GTR. Vulcanization at higher temperatures resulted in reduced hardness, and modulus, slightly increased abrasion loss and increased elongation of the vulcanizates containing GTR. The heat build-up increased as the cure temperature increased. Generally, the control sample with no content of ground tire rubber exhibited the best properties. If GTR is to be introduced in rubber matrix at an amount up to 20%, the results suggest that 60 mesh size particles will impart better properties. The optimal vulcanization temperature recommended based on the findings from the work is 150°C.

Mechanical and Rheological Evaluation of Polyester-Based Composites Containing Biochar.

The use of biodegradable polymers as matrices in composites gives a wide range of applications, especially in niche areas. The assessment of the effect of the filler content on the change of mechanical properties makes it possible to optimize the composition for specific needs. Biochar was used as a filler in the studied composites with two different biodegradable blends as a matrix. Poly(1,4-butylene adipate-co-1,4-butylene terephthalate)/polylactide/biochar (PBAT/PLA/BC) and polylactide/poly[(R)-3-hydroxybutyrate-co-4-hydroxybutyrate]/biochar (PLA/P(3HB-co-4HB)/BC) composites with 0, 10, 15, 20 and 30 wt% of biochar underwent mechanical tests. The test results revealed a change in the properties of the composites related to the filler content. The results of the tensile test showed that increasing the biochar content increased the tensile modulus values by up to 100% for composites with 30 wt% of biochar, compared to unfilled matrices, and decreased the elongation associated with the breaking of PBAT/PLA and PLA/P(3HB-co-4HB) matrix composites. The elongation values at break of PBAT/PLA and PLA/(3HB-co-4HB) composites with 30 wt% biochar were reduced by 50% and 65%, respectively, compared to the unfilled matrices. PLA/P(3HB-co-4HB) matrix composites, in contrast to PBAT/PLA/BC, showed a decrease in tensile strength with the increases in filler content from 35.6 MPa for unfilled matrix to 27.1 MPa for PLA/P(3HB-co-4HB)/BC30 composites. An increase in filler content increased the brittleness of the composites regardless of the matrix used, as determined under the Charpy impact-test. This phenomenon was observed for all tested PLA/P(3HB-co-4HB) composites, for which the impact strength decreased from 4.47 kJ/m2 for the matrix to 1.61 kJ/m2 for the composite containing 30 wt% biochar. PBAT/PLA-based composites with 10 wt% of biochar showed slightly lower impact strength compared to the unfilled matrix, but composites with 30 wt% biochar showed 30% lower impact strength than PBAT/PLA. The complex viscosity value increased with increased filler content. For all composites tested on both polyester matrices, the viscosity decreased with increasing angular frequency.

The synthesis of a novel polymer‐type antistatic agent and its effect on the properties of polypropylene

AbstractIn this paper, a novel polymeric antistatic agent, TMQ, with excellent antistatic properties, low cost, and good compatibility with polypropylene (PP), was prepared from isopentenyl polyoxyethylene ether (TPEG), maleic anhydride (MAH) and homemade quaternary ammonium salt (QAS). The structure is characterized using FTIR and 1H NMR. How the addition of TMQ and the molar ratio of TPEG, QAS, and MAH affect the antistatic, mechanical, and crystalline properties of PP are investigated. The results show that as the feed ratio of TPEG, MAH and QAS is TPEG:MAH:QAS = 1:8:8, the modified PP displays the best overall performances. Further exploring finds out when TMQ is added at 15 wt%, the surface resistivity of PP reduces to 6.78 × 109 Ω/sq and the volume resistivity of PP reduces to 7.9 × 109 Ω cm−1, the notched impact strength and melt index improve by 357% and 991%, respectively, while the tensile strength decreases by 38.6% compared with that of pure PP. Besides, the crystal study shows after TMQ is added, the crystallinity of PP reduces, the melt peak temperature remains essentially unchanged, and the crystallization peak temperature increases slightly. The material has excellent antistatic resistance to washing and durability, and the changes in relative humidity have little effect on its antistatic properties.

Effect of hydrophobic nano-silica content on the surface properties of corn-starch films

Starch-based films can be used for applications such as single-use packaging for food with a short shelf life. Hence, starch-based films could be a green alternative to some plastic packaging. This study analyzes the influence of hydrophobic silica content on mechanical properties, surface free energy, surface roughness, and morphology of corn starch-based films. For this purpose, commercially available amorphous hydrophobic nano-silica, Aerosil® R972, was used. The lowest value of surface free energy was observed for the starch films with the lowest glycerol and silica content (57 ± 1 mJ·m–2 for CG40S2.5), while the highest value was with the highest glycerol and silica content (73 ± 2 mJ·m–2 for CG80S5.0). The influence of silica content on the tensile strength decreases and elongation at break was investigated. The results showed that the surface roughness increases when the silica content increases. The SEM and EDS observation confirmed the homogeneity of the developed materials. This study shows that the commercially available Areosil® type of silica can be successfully used to change the performance of starch films.

Performance assessment of blended self-compacting concrete with ferrochrome slag as fine aggregate using functional ANOVA

The current study explored the feasibility of re-use of ferrochrome slag (FS), a waste byproduct from the ferrochrome industry as a replacement to fine aggregate in self-compacting concrete (SCC) with cement and fly ash as binders. The study investigated the mechanical and durability characteristics of SCC of M25 grade, incorporating FS in lieu of fine aggregate, up to 60 % replacement levels. Albeit workability of fresh concrete decreased with the increase of FS content, they were within the recommended limits of EFNARC for SCC. Considerable decreases in compressive, tensile and flexural strengths were observed in the mixtures with FS contents above 40 %. Slightly better performances in terms of water absorption, sorptivity, chloride ion permeability and sulphate attack were found in the concretes partially blended with FS. Leaching of chromium (Cr) from FS-incorporated self-compacting concrete samples were within the Indian discharge limits. Microstructural studies were conducted to decipher the arrangement of components in the concrete as well as determine the elemental composition of ferrochrome slag. Functional analysis of variance (ANOVA) was conducted to determine the significance of functional components in explaining the variability of the mechanical properties expressed as continuous functions. The test findings indicate that there is no statistical difference in the compressive strength and split tensile strength as a result of substituting a portion of sand with FS. Nevertheless, a rise in flexural strength is noticed after surpassing a 5 % substitution.

Experimental Study on Salt-Bearing Sandstone Samples Under the Change of Temperature and Humidity Cycle

ABSTRACT Salt crystallization is a common type of disease in grottoes. Due to the change in temperature and humidity, the soluble salt originally existing in sandstone will have a negative impact on the protection of rock relics. In this study, sandstone samples containing Na2SO4 solution and distilled water were used to study the difference in sample damage under the condition of temperature and humidity cycle changes. It was found that the damage degree of samples containing soluble salts was much higher than that of salt-free samples, especially under the influence of freeze-thaw cycles. With the increase of freeze-thaw cycles, the internal friction angle and wave velocity of sandstone decrease linearly, while the surface hardness, tensile strength, and cohesion decrease exponentially. In addition, the damage caused by freeze-thaw cycles and dry-wet cycles develops from the inside to the outside of the rock sample, which is manifested by the increase in the number of macropores and the emergence of new pores. The different combinations of several effects lead to different changes in pore structure and mineral composition of the samples under the four conditions. The research results are helpful in providing a scientific basis for the disease control of stone cultural relics.

Modulating hierarchical microstructural components to enhance strength-ductility synergy of a high-entropy alloy containing brittle sigma phase

Although brittle intermetallic phases are usually unwanted in the design of strong and ductile alloys, high strength and good ductility can be achievable in high-entropy alloys (HEAs) containing brittle phases. Here, we present an investigation on modulating the hierarchical microstructural components in a prototype metastable HEA (Fe30Cr25Co25Mn10Ni10, at. %) containing sigma (σ) phase to optimize the mechanical properties. An excellent combination of tensile strength (999.3 MPa) and ductility (57.7 %) is achieved in alloy sample containing recrystallized grains of various sizes, which is mainly attributed to the continuous transformation-induced plasticity (TRIP) effect and the back stress effect caused by the pile-up of geometrically necessary dislocations at various interfaces in the hierarchical microstructures. The decrease in fraction of hard domains (σ particles, non-recrystallized and small-sized grains) can lead to the decrease of tensile strength due to the weakened back stress effect. However, an excessively high fraction of hard domains (particularly with small-sized grains and σ particles) suppresses the TRIP effect, facilitating crack propagation and reducing ductility. The back stress effect can be rationally controlled through tuning the fraction and size of small-sized grains (accompanied with fine σ particles) by thermo-mechanical treatments, which can also enable the activation of TRIP effect in grains of various sizes to render high strain-hardening rate and good strength-ductility synergy. This provides a strategy for achieving an optimum combination of strength and ductility for metastable HEAs containing fine brittle phases via alleviating the embrittling effect of brittle phases and retaining the precipitation strengthening effect.

Recycled Household Plastic and Oil Palm Filler Reinforced Epoxy Composite for Lightweight Construction Applications

Polypropylene is extensively used in aerospace, automotive and construction applications due to its versatile properties. This project aims to reduce plastic and oil palm waste and promote the development of strong, sustainable and eco-friendly construction materials. The objective of this project is to develop a sustainable yet high-performance construction material by incorporating polypropylene particles, oil palm empty fruit bunch (OPEFB) fibres and oil palm shell (OPS) particles into epoxy composites through the hand lay-up method. The composite specimens undergo ASTM D638 tensile test to determine the tensile properties. The addition of PP particles in varying weights shows decrease in tensile strength, likely due to poor dispersion and compatibility with the epoxy matrix. Incorporating 3 wt% OPEFB fibres with fibre length from 2mm to 4mm improves tensile strength by 2.32% and 23.36% respectively at higher PP particle loadings which are 15 wt% and 25 wt%. Adding 1 wt% and 3 wt% OPS particles improves the tensile strength by 2.96% and 4.68% respectively, in composites with 10 wt% PP particles and 3 wt% OPEFB fibres. The tensile performance may be improved by treating PP particles with compatibilizers such as silane or maleic anhydride grafted polypropylene.

Gelatine Blends Modified with Polysaccharides: A Potential Alternative to Non-Degradable Plastics.

Non-degradable plastics of petrochemical origin are a contemporary problem of society. Due to the large amount of plastic waste, there are problems with their disposal or storage, where the most common types of plastic waste are disposable tableware, bags, packaging, bottles, and containers, and not all of them can be recycled. Due to growing ecological awareness, interest in the topics of biodegradable materials suitable for disposable items has begun to reduce the consumption of non-degradable plastics. An example of such materials are biodegradable biopolymers and their derivatives, which can be used to create the so-called bioplastics and biopolymer blends. In this article, gelatine blends modified with polysaccharides (e.g., agarose or carrageenan) were created and tested in order to obtain a stable biopolymer coating. Various techniques were used to characterize the resulting bioplastics, including Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC), contact angle measurements, and surface energy characterization. The influence of thermal and microbiological degradation on the properties of the blends was also investigated. From the analysis, it can be observed that the addition of agarose increased the hardness of the mixture by 27% compared to the control sample without the addition of polysaccharides. In addition, there was an increase in the surface energy (24%), softening point (15%), and glass transition temperature (14%) compared to the control sample. The addition of starch to the gelatine matrix increased the softening point by 15% and the glass transition temperature by 6%. After aging, both compounds showed an increase in hardness of 26% and a decrease in tensile strength of 60%. This offers an opportunity as application materials in the form of biopolymer coatings, dietary supplements, skin care products, short-term and single-contact decorative elements, food, medical, floriculture, and decorative industries.

Material recycling of acrylonitrile butadiene styrene (ABS) from wiring devices using mechanical recycling

Plastics play a significant role in various sectors by offering advantages such as durability, cost-effectiveness, and lightweight properties. However, the extensive production and consumption of plastics create significant environmental threats, leading to high carbon footprints, global warming, and the accumulation of hard-to-recycle waste. This study explores innovative recycling technologies, focusing on the circular economy and zero waste strategies. In line with this scope, the study aims to conduct research on the reuse of coated plastic materials in production, specifically selecting ABS materials that are difficult to recycle. In the study, wiring devices were prepared using 70% raw ABS (Acrylonitrile Butadiene Styrene) material and 30% recycled ABS (rABS) material, with this cycle being repeated three times. Experiments have been conducted to evaluate the suitability and performance of recycled ABS material for mass production. The results have revealed a slight decrease in tensile strength and impact strength compared to raw ABS material, yet significant mechanical performance has been maintained, thus demonstrating the viability of rABS in preserving product quality throughout successive recycling processes.

Polylactic acid/epoxidized linseed oil/polypropylene grafted maleic anhydride: A promising combination of toughness and rigidity

AbstractIncreasing toughness of brittle polymer without losing modulus of elasticity and tensile strength is highly important for enlarging the range of applications. In this study, polylactic acid (PLA) modified with epoxidized linseed oil (ELO) and polypropylene‐grafted maleic anhydride (PPgMA) with a good balance of toughness and rigidity was successfully prepared by melt mixing procedure. The addition of PPgMA/ELO with appropriate proportions (3:1, 5:1, and 5:5 wt%) resulted in PLA modified samples with significant ductility improvement (around 2200% of elongation at break and 1800% of tensile toughness compared to the neat PLA) with low decrease in Young modulus and tensile strength. This feature was attributed to improved interfacial interactions and the formation of crosslinked structures at the interface that also increased viscosity of the melting system and cold crystallization temperature of PLA. The scanning electron microscopy revealed the presence of small domains of modified systems. The effectiveness of reactive compatibilization among the components was also suggested by Fourier transform infrared (FTIR) spectroscopy and thermal degradation analysis. The combination of toughness, modulus of elasticity and good thermal properties make this low‐cost and scalable eco‐friendly material a promising candidate for use as biodegradable plastic in several fields including medical applications and packaging.

Thermo-mechanical characterizations and erosion wear studies of fumed silica-reinforced jute/epoxy composites

This study investigates the influence of nano-fumed silica content on thermo-mechanical properties of jute/epoxy composites. The results reveal that jute composites without filler (JJJJ-0) exhibited highest tensile strength (33.01 MPa) and percentage elongation (1.9522%), while composites with 1.5% and 2.5% filler demonstrated the highest tensile modulus (1967 MPa) and flexural modulus (2432.9 MPa), respectively. The observation demonstrates that as the filler content increases in jute composites, tensile strength decreases but flexural strength increases. However, an exception is noted for sample containing excess filler (3.5%), which exhibited the lowest flexural strength (44.36 MPa). The composite with 2.5% filler exhibited the highest flexural strength (53.5 MPa). Thermal analysis indicated that the addition of nanofiller enhanced both the activation energy (Ea) and thermal stability of the jute composites. A four-layer carbon composite without filler (CCCC-0) was also fabricated in order to compare wear and thermal stability performance with jute composites. The wear study was performed at different temperatures and found that JJJJ-3.5 composite exhibited superior wear resistance at ambient temperature, while CCCC-0 composite had better wear resistance at high temperatures. Also, the surface morphology of the eroded surface was examined using a scanning electron microscope (SEM) to study the failure mechanism of composites.

UNSATURATED POLYESTER RESIN BASED COMPOSITES: A CASE STUDY OF LIGNIN VALORISATION

Materials from green resources boast a low carbon footprint, forming the foundation of the circular economy approach in materials science. Thus, in this study, waste poly(ethylene terephthalate) (PET) was subjected to depolymerization using propylene glycol (PG), and subsequent polycondensation with bio-based maleic anhydride (MA) produced unsaturated polyester resin (b-UPR). Bio-derived acryloyl-modified Kraft lignin (KfL-A) served as a vinyl reactive filler in the b-UPR matrix to create b-UPR/KfL-A composites. The structural characterization of KfL-A and b-UPR involved the use of FTIR and NMR techniques. The mechanical properties of the newly fabricated composites were assessed through tensile strength, Vickers microhardness, and dynamic mechanical tests. The addition of KfL-A to the rigid b-UPR matrix enhanced material flexibility, resulting in less stiff and hard materials while preserving composite toughness. For instance, incorporating 10 wt.% of KfL-A in b-UPR led to a 17% reduction in hardness, a 48% decrease in tensile strength, and a 20% reduction in toughness. Positive environmental impact was achieved by incorporation of 64 wt.% of renewable and recycled raw material. Analogously prepared b-UPR/KfL composites showed structural inhomogeneity and somewhat better mechanical properties. Transmission (TEM) and scanning (SEM) electron microscopies revealed a suitable relationship between mechanical and structural properties of composites in relation to the extent of KfL-A addition. The UL94V flammability rating confirmed that flame resistance increased proportionally with the KfL-A addition. Once deposited in a landfill, these composites are expected to disintegrate more easily than PET, causing less harm to the environment and contributing to sustainability in the plastics cycle.

Investigation on the Correlation between Biaxial Stretching Process and Macroscopic Properties of BOPA6 Film.

Biaxially oriented polyamide 6 (BOPA6) films were prepared by extrusion casting and biaxial stretching with polyamide 6. The effects of different biaxially oriented on the macroscopic properties of BOPA6 were investigated by characterizing the rheological, crystallization, optical, barrier and mechanical properties. The results show that the increase of stretching temperature leads to the diffusion and regular stacking rate of BOPA6 chain segments towards crystal nuclei increases, the relative crystallinity increases, reaching 27.87% at 180 °C, and the mechanical strength and optical performance decrease. Heat-induced crystallization promotes the transformation of β-crystals to α-crystals in BOPA6, resulting in a more perfect crystalline structure and enhancing oxygen barrier properties. BOPA6 chains are oriented, and strain-induced crystallization (SIC) occurs during the biaxial stretching. Further increasing the stretch ratio, the relative crystallinity increased to 30.34%. The machine direction (MD) and transverse direction (TD) tensile strength of BOPA6 (B-33) are nearly two times higher than the unstretched film, reaching 134.33 MPa and 155.28 MPa, respectively. In addition, the permeation decreases to 57.61 cc·mil/(m2 day), and the oxygen barrier performance has improved by nearly 30% compared to the sample B-22. BOPA6 has a high storage modulus at a high stretching rate (300%/s). Rapid chain relaxation would promote the molecular chain disorientation, destroy the entangled network of the molecular chain, and lead to a decrease in tensile strength, reducing to about 110 MPa.