Hot Drawing Research Articles

Preparation and Antibacterial Properties of Poly (l-Lactic Acid)-Oriented Microporous Materials

In this manuscript, an efficient self-reinforcing technology—solid hot drawing (SHD) technology—was combined with green processing supercritical carbon dioxide (SC-CO2) foaming technology to promote poly (l-lactic acid) (PLLA) to form an oriented micropore structure. In addition, Polydimethylsiloxane (PDMS), with a high affinity of CO2 and biological safety, was introduced to enhance the nucleation effect in SC-CO2 foaming and co-regulate the uniformity of oriented micropores’ structure. The results showed that orientation induced PLLA crystallization, so the tensile strength was improved; the maximum tensile strength of the oriented micropores’ PLLA reached 151.2 MPa. Furthermore, the micropores mainly improved the toughness; the maximum elongation at break reached 148.3%. It is worth mentioning that PDMS can form an antibacterial film on the surface of the material, so that the material has a continuous antibacterial effect.

Grain boundary segregation of B and microstructure evolution in a hot-drawn Fe–B alloy

The grain boundary segregation (GBS) of boron and microstructure evolution in a hot-drawn Fe–B alloy are investigated utilising the Gleeble-1500, Auger electron spectrometer, time-of-flight secondary ion mass spectrometry, electron back-scattered diffraction, and transmission electron microscopy techniques. The results suggest substantial boron segregation at grain boundaries of the Fe–B alloy during the hot drawing process. In comparison to the contribution of dislocations to boron diffusion coefficients, the influence of vacancies is predominant. With the increase in hot-drawing temperature, the ratio of excess vacancy content to thermal equilibrium vacancy content [Formula: see text] decreases, and the content of low [Formula: see text] (low Sigma coincidence site lattice) boundaries increases, resulting in a reduction in boron GBS content. Additionally, elevating the hot-drawing temperature promotes dynamic recrystallisation and refines the grains. The volume fraction of the <110>//RD (rolling direction) texture component initially increases and then decreases with increasing temperature, reaching a maximum value of 64.6% at 830 °C, while the percentage of the <100>//RD + <111>//RD texture components exhibits the opposite trend, with a peak value of 27.4% observed at 1000 °C.

The feasibility and rationale for utilizing high molecular weight PBT in the preparation of high-strength fiber

Polyethylene terephthalate (PET) industrial yarn is prone to damage during weaving due to its insufficient flexibility. Therefore, it is worth exploring whether polybutylene terephthalate (PBT) with improved flexibility can be utilized for the production of high strength and low modulus industrial yarn. In this study, a low velocity spinning multi-stage multi-ratio drawing technology route was employed for spinning, but PBT fibers only achieved a break strength of 5.1cN/dtex, which was lower than that of PET fibers (7.2cN/dtex). By comparing the multi-level structure evolution of PET and PBT during spinning, it was found that the core problem limiting the strength improvement of PBT fibers is due to the early formation of folded chain lamellar structure in PBT as-spun fibers during cooling, which hinders conformational transition during hot drawing and limits the drawing ratio. This has important implications for the development of PBT industrial yarn technology by adjusting the crystallization characteristics of PBT as-spun fibers.

In Vitro and In Vivo Degradation of the New Dissolvable Surgical Wire, Produced from Zn Based Low Alloy by Hot and Cold Drawing

The biocorrosion of a new surgical wire (0.6, 0.8, and 1.0 mm in diameter) obtained from a ZnMg0.004 alloy by hot and cold drawing was characterized using in vitro tests in a bovine animal serum solution and in vivo tests – through placement in the muscles of a rabbit and a in cat's broken paw. Corrosion gravimetric tests were carried out in a corrosive environment refreshed every 3 days and also one which remained unchanged throughout the test period. Electrochemical tests were performed in the same solution of serum as in gravimetric tests. Depending on the initial diameter, complete dissolution of the wire was observed after 36-78 days of immersion in periodically changed serum solution. None of the wires completely dissolved over 120 days in the unreplaced serum solution. The corrosion rate values determined in electrochemical and gravimetric tests were similar. After 90 days of in vivo tests, both in the body of the rabbit and the cat, the degradation of the wire was similar to in vitro tests in the unreplaced serum solution. No harmful effects were observed in the animals.

Excellent thermal conductive epoxy composites via adding UHMWPE fiber obtained by hot drawing method

AbstractThe continuous updating and iteration of electronic devices brings about a significant accumulation of heat. It is urgent to enhance the thermal properties of polymer‐based composites to alleviate the heat dissipation problem in the microelectronics industry. In this paper, the hot drawing process was introduced to increase the crystallinity of ultra‐high molecular weight polyethylene (UHMWPE) fiber and improve its thermal conductivity. The ultra‐high molecular weight polyethylene fiber/epoxy resin (UHMWPE fiber/Epoxy) composites with high thermal conductivity were prepared by compositing UHMWPE fiber with epoxy resin under vacuum conditions. Due to the good crystallinity of the UHMWPE fiber (86%), an efficient thermal conduction path is provided for phonons in the axial direction along the fibers. The results show that the thermal conductivity of the composites reaches a maximum of 3.51 W/mK (in‐plane), which is 17.47 times higher than that of the epoxy resin (0.19 W/mK). The thermography pictures indicate that the composites have better heat transfer capacity with an increase in the draw ratio (λ). In addition, the composites also have the characteristics of low density and low electrical conductivity. These researches will provide a new idea for the preparation of all‐polymer composites with high thermal properties.Highlights A hot drawing process was introduced to increase the crystallinity of UHMWPE fiber for improving thermal conductivity. High crystallinity facilitates the reduction of phonon scattering and the transmission of thermal energy by phonons. The obtained polymer composites exhibit an ultra‐high in‐plane thermal conductivity.

Calculations of phase composition of austenitic high-nitrogen welding wire and study of a welded joint made from it

The processability of a material is directly related to the possibility of its production, operation and maintainability. One of the most important indicators of the processability of any metal is weldability. Austenitic steels with a high nitrogen content proved themselves as high-strength, corrosion- and cold-resistant materials, but the issue of their weldability is still not fully understood. The lack of welding filler materials on the market specifically designed for welding high-nitrogen steels is the primary obstacle to solving this problem. Thus, the goal of the work was to develop and obtain a laboratory sample of high-nitrogen welding wire. Based on calculations of nitrogen solubility and the phase composition of the weld metal, the chemical composition of Cr – Mn – Ni – Mo – V, N steel was selected for this wire. A defect-free ingot with 0.57 % N was obtained, and wire with a nitrogen content of 0.57 wt. % was produced using hot plastic deformation and drawing methods. Testing of this wire to obtain a welded joint of austenitic cast steel, close to it in chemical composition, with the welding process carried out according to the developed technological recommendations, made it possible to obtain a defect-free welded joint without loss of nitrogen in the weld metal. With a microhardness of the base metal of 252 HV50 , due to the alloying of the welding wire steel with nitrogen and vanadium, the metal of the weld and fusion line had a high microhardness (278 and 273 HV50 , respectively), significantly exceeding the microhardness of Cr – Ni cast austenite. The metal of the welded joint has high strength (0.9 of the base metal strength) and high impact toughness. The fracture of impact samples is characterized by a dimple structure characteristic of viscous materials. According to the obtained results, the new welding wire showed itself to be a promising material for welding austenitic high-nitrogen steels.

Enhanced melt flow UHMWPE/HDPE blends melt spinning and performance study

AbstractThe extremely low melt flowability of ultra‐high molecular weight polyethylene (UHMWPE) is the primary obstacle to its melt processing. Particularly in melt spinning processes, the extremely high molecular weight of UHMWPE and the density of entangled molecular chains severely limit its production efficiency and monofilament performance. This study investigates the effect of flow modifiers on the melt spinning process of UHMWPE/HDPE blends, focusing on CaSt2, PEG, and CaSt2/silicone powder composite additives, and their impact on the standard tensile samples and monofilament tensile properties of UHMWPE/HDPE. The mechanism of additive influence on the tensile properties of UHMWPE/HDPE blends is analyzed through tensile strength testing, thermal analysis, and microscopic morphology observation. The results show that in standard tensile samples, CaSt2 or CaSt2/silicone powder composite additives can enhance the crystallinity of the blend, thereby improving its tensile strength. Conversely, adding PEG significantly reduces the crystallinity and tensile strength of the blend. The maximum tensile strength of CaSt2‐modified UHMWPE/HDPE monofilament is 1236.61 MPa. This enhancement is attributed to the lubricating effect of CaSt2, which simultaneously assists the molecular chains in the amorphous region, and the reorientation of the stress‐induced molten lamellar structure under tension, greatly promoting the formation of straight‐chain crystals in the monofilament. During hot drawing, PEG inhibits the formation of straight‐chain crystals in the monofilament, resulting in a 3.06% decrease in maximum crystallinity compared with standard tensile samples. When CaSt2 is combined with silicone powder, the additives tend to aggregate during hot drawing, and these larger aggregate particles hinder the orientation of molecular chains along the drawing direction, resulting in a 30.75% decrease in maximum tensile strength of the monofilament compared with the standard tensile samples.Highlights The tensile property of UHMWPE/HDPE blends modified with additives was discussed. Analytical techniques including DSC, SEM, and tensile strength tests were used. The maximum tensile strength of the monofilament can reach up to 1236.61 MPa. UHMWPE/HDPE/CaSt2 = 60/40/0.5 exhibits the best tensile property.

Study on the hot deep drawing performance and microstructural evolution of AZ91D magnesium alloy sheets

Magnesium alloys are attractive because of their low density and high specific strength and stiffness; however, secondary phase strengthening and the low number of slip systems lower formability especially for the strongest magnesium alloys such as AZ91D. The formability of AZ91D sheets is investigated through orthogonal experiments, which show that AZ91D has no deep drawing properties at room temperature and that plastic forming is only possible under hot forming conditions. When the temperature is increased from room temperature to 400 °C, the limiting drawing ratio of the sheet increases significantly to 1.91, and the thinning rate reaches a minimum value of 6% at approximately 400 °C because of the improved plastic flowability. The optimum process parameters for hot deep drawing are a temperature of 400 °C, blank holder force of 5 kN, and punch speed of 3 mm s−1. The microstructural evolution shows that plastic deformation of the AZ91D magnesium alloy at high temperatures is markedly accommodated by twinning and that, with heating, this twinning deformation mechanism is activated and overcomes the hindrances of the reinforcing phases to achieve better forming properties.

Shish‐kebab structure evolution of HDPE/UHMWPE during hot drawing

AbstractUsing a solution‐mixing method, this research aimed to fabricate high‐density polyethylene (HDPE)/ultra‐high molecular weight polyethylene (UHMWPE) composite materials with uniform dispersion. By incorporating a small quantity of UHMWPE as a nucleating agent, additional contact points were introduced to enhance the crystallization rate of the HDPE matrix. Thermal stretching experiments were conducted on composite systems with varying UHMWPE contents and molecular weight additions at different temperatures. Elevating the stretching temperature was found to decrease the yield strain and yield strength, extend the stage of tensile plastic deformation, and diminish the overall mechanical properties of the composite material. Notably, stretching at temperatures ranging from 90 to 110°C accentuated the development of internal crystal orientation structures. Under low strain conditions, crystal slip was observed to be concentrated, with single crystals undergoing continuous stretching and breaking, resulting in a decrease in the long period. Conversely, at high strains, the induced formation of oriented lamellar structures was observed.Highlights Prepared HDPE/UHMWPE blends by UHMWPE with varying molecular weights. Analyzed the alterations in the HDPE/UHMWPE blends' internal crystal structure. Influence of UHMWPE addition, temperature on the evolution of crystal structure.

Microstructure evolution and mechanical property of Mg-Gd-Y-Zn-Zr alloy wires prepared by hot drawing

This study examined the effects of hot drawing deformation on the microstructure, texture, and mechanical properties of an Mg-9.5Gd-4Y–2Zn-0.3Zr alloy. A Φ6 mm extruded alloy bar was hot drawn down to a Φ1.2 mm wire through multi-passes. The results revealed that the intergranular 18R-long period stacking ordered (LPSO) phase was gradually changed into elongated shapes distributing along the drawing direction with increasing deformation strain, while the 14H-LPSO phase precipitates in the α-Mg matrix are progressively fragmented. The average grain size in the wire first increased from 4.6 μm to 25.9 μm and then decreased to 6.7 μm, and the volume fraction of dynamic recrystallisation first decreased from 95.5% to 8.6% and then increased to 48.7%. The initial weak <0001>//ED anomalous texture gradually changed and strengthened into a <01-10>//DD dual basal texture. The Φ1.2 mm wire achieved a tensile strength of 553.5 MPa, a yield strength of 473.6 MPa, and an elongation of 2.5%. Calculations indicated that the high yield strength in Φ1.2 mm wire was mainly attributed to the high content of the large aspect ratio 18R-LPSO phase, high density of low angular grain boundaries, and strong basal texture.

Phase transformation, texture evolution, and mechanical properties of Mg-9.5Gd-4Y-2Zn-0.3Zr alloy wires fabricated using hot drawing

Mg-9.5Gd-4Y-2Zn-0.3Zr alloy wires with a diameter of 1.2 mm were fabricated by a multistage drawing process with a cumulative area reduction (CAR) of 96% at 500 °C using as-extruded rods with a diameter of 6 mm as the raw material. Investigated the impact of microstructural transformations on the mechanical performance of these wires, with a focus on phase evolution, texture changes, and grain refinement. In the alloy, second-phase 18R-LPSO, rare-earth-rich (RE-rich) phase, and Zn2Zr3 distributed at the grain boundaries along the extrusion direction (ED) or the drawing direction (DD), which were different from the intragranular 14H-LPSO phase, were observed. Significantly, we observed the transformation of blocky 18R-LPSO phases into sub-2μm W-Mg3Zn3RE2 particles during hot drawing. All the as-extruded and as-drawn wires exhibited equiaxed grains with average sizes between 4 μm and 7 μm. The as-extruded wires exhibited a texture with {0001} perpendicular to ED. As the CAR increased, the texture of the wires transformed into a basal texture with {0001} parallel to DD. The ultimate tensile strength (UTS) and tensile yield strength (TYS), respectively, increased from 369 MPa to 283 MPa for the as-extruded wire to 466 MPa and 436 MPa for the as-drawn wire with CAR increasing to 55%, and then decreased to 328 MPa and 318 MPa for the wire with CAR increasing to 96%. The elongation (EL) reduced from 8.01% to 1.37% with CAR increasing to 96%. As CAR exceeded 55%, the increased volume fraction of the W-Mg3Zn3RE2 phase resulted in a significant decrease in both the strength and the plasticity of the wires. The evolution of microstructure and mechanical properties provides possibility for regulating both the strength and elongation of the Mg-Gd-Y-Zn-Zr alloy wires by optimizing the drawing process.

Ultra‐high molecular weight polyethylene micro‐ribbon fibers gel spun using orange terpenes

AbstractToxic, hazardous petrochemical solvents are commonly used for industrial‐scale ultra‐high molecular weight polyethylene (UHMWPE) fiber production, but orange terpenes, a byproduct of orange fruit production, present a bio‐derived, sustainable alternative. In this work, fine UHMWPE fibers were spun using orange terpenes as the spin solvent, hot‐drawn at a draw ratio of 5:1, investigated for their morphology, microstructure, and thermal and mechanical properties. The resulting fibers exhibited a flat, micro‐ribbon cross‐section, which is highly desirable for achieving high fiber volume fractions in UHMWPE‐fiber reinforced composites. After drawing, the fibers possessed 4× greater breaking tenacity than any previously published studies on UHMWPE fibers spun using orange terpenes with a tenacity of 8.6 cN/dtex and tensile modulus of 229.2 cN/dtex. Microstructural analysis via differential scanning calorimetry and X‐ray diffraction revealed that the hot drawing process significantly increased molecular orientation, but crystallinity decreased due to crystallite melting during drawing. Therefore, the mechanical properties of these fibers may be significantly improved with optimization of the fiber drawing process. This work establishes the strong potential of orange terpenes as an environmentally‐friendly alternative solvent for UHMWPE gel spinning and sets a foundation for future parametric optimization of the spinning and drawing of these fibers.Highlights Micro‐ribbon ultra‐high molecular weight polyethylene fibers were prepared using bio‐solvent orange terpenes. Flat profile enables tight packing, aspect ratio maintained after drawing. Drawn fibers were 4× stronger than any previous work with orange terpenes. Near‐melt drawing reduced crystallinity, improved molecular alignment.

Macromolecular structure development of dry-spinning UHMWPE fibers through the industrial high-ratio hot-drawing process

Ultra-high molecular weight polyethylene (UHMWPE) and its decalin suspension were subjected to several industrial processes including swelling, dissolving, spinning, drying, and multi-stage high-ratio hot drawing to fabricate UHMWPE fibers (UPE fibers). The morphologies and architectures of the UPE fibers at different drawing stages were characterized by polarizing optical microscope (POM), scanning electron microscope (SEM) and atomic force microscopy (AFM). The aggregation structure evolution of UHMWPE macromolecules during the high-ratio hot-drawing process was studied by differential scanning calorimeter (DSC), wide-angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS) and other testing methods. The experimental results demonstrated that the UHMWPE/decalin spinning suspension was extruded from the spinneret hole to form a fine spinning flow, followed by the formation of the transitional-state fibers at different processing stages, and finally the ready-made fibers. The total drafting ratio of the UPE fibers after fabrication reached more than 600 times. The diameter of the single UPE filament was reduced to 5.66 μm with elevated drawing ratios. The crystal structure of the prepared UPE fibers was progressively improved, and the folding-chain crystals of fibers gradually transformed into extended-chain crystals. The mechanical properties of the UPE fibers were significantly improved. The fracture strength of the as-spun UPE fibers reaches 48.1 cN/dtex, which endows the fibers with specific characteristics such as ultra-fine denier and ultra-high strength.

Transformation- and stress-temperature behavior of hot-drawn Ni-rich NiTi wire after isochronous aging

Aging temperature in the range of 300–500 °C (1 h) strongly affects transformation and mechanical behavior of Ni50.8Ti alloy wire samples obtained as a result of hot drawing at test temperatures of −196 ≤ T ≤ 60 °C. Isochronous aging of hot-deformed Ni-rich NiTi alloy forms a mixed substructure that consists of grains and subgrains, their average size increases from 0.9 to 3.3 μm vs temperature growth. In the aging range of 430–500 °C the diameter of Ti3Ni4 precipitates grows from 10–20 nm to 0.1–0.2 μm along the grain/subgrain boundaries. The widest RsM − Af temperature range (Δ76°C) of the reverse MT is revealed after aging at 300 °C; the minimal RsM − Af temperature range (Δ10°C) – after aging at 500 °C. Aging-induced microstructure strongly affects stress–temperature behavior and Young’s modulus: the obtained regularities are associated with contribution of various competing factors.

Hydrogen generation by hydrolysis of ultrafine microstructure Mg[sbnd]10Ni alloy wire

This work presents a MgNi alloy wire prepared by a combination of extrusion and multi-pass hot drawing for fast hydrogen generation from aqueous NaCl solution. The results showed that the hydrogen generation rates of the wire were significantly improved compared to the as-cast alloy. The hydrolysis of the MgNi alloy wire produced 820 ml g−1 hydrogen in 16 min and the maximum hydrogen generation rates reached 67.86 ml g−1 min−1 in 3.5 % NaCl solution and at 25 °C. The improved hydrogen production properties can be attributed to the increase in specific surface area and the ultrafine microstructure with highly dispersed submicron Mg2Ni particles of the MgNi alloy wire.

Study on formability and microstructure evolution of hot deep drawing manufactured 7005 aluminum alloy sheet metal

The hot deep drawing process with an in-die heating system was proposed on the forming of 7005 aluminum alloy to improve the formability due to the limitation of ductility during severe plastic deformation at room temperature. The feasibility of hot deep drawing AA7005 sheet (only 0.8 mm) was investigated and evaluated by Swift cup tests from RT to 450 °C. The priority of main process parameters, namely temperature, blank holder force, and stamping speed, on sheet metal forming limit were discussed by analysis of range and variance. Experimental results indicated that elevating the temperature could fundamentally improve the deep drawing performance of the alloy, which is manifested by the revolutionary change in sheet metal behavior — from the failure of deformation at lower temperatures (RT-200 °C) to achieving a limiting drawing ratio of 2.19 at 450 °C. The optimal process parameters under HDD conditions are given as drawing temperature of 400 °C∼450 °C, BHF of 3 kN, and punch speed of 15–20 %. The thickness variation increases with rising temperature corresponding to the formability enhancement during the process within acceptable limits. DRV and DRX are the flow softening mechanism under the high temperature and large strain in HDD process obtained from the analysis of microstructure and texture evolution. The elongation and rotation of grains further substantiated the interrelationship between drawing performance and microstructure evolution. Improving the deep drawing performance through HDD process can provide practical guidance for the application of AA7005 sheet metal.

Effect of Deformation Degree on Microstructure and Texture of AZ31 Magnesium Alloy in Hot Drawing

Microstructure and texture evolution of the AZ31 magnesium alloy wire under different deformation degrees was investigated by continuous hot drawing deformation. With the increase of cumulative deformation degree, the grain refinement effect is remarkable. However, there is a critical deformation degree, and excessive deformation will increase the grain size. During the deformation process of hot drawing, the dynamic recrystallization mechanism of AZ31 magnesium alloy wire changed from twin dynamic recrystallization to rotary dynamic recrystallization. With the increase of cumulative deformation, the initial {0001} <11-20> silk texture gradually changed into {0001} <10-10> silk texture.

Abnormal grain growth of FeMnAlNiCo shape memory alloys during directional recrystallisation

Polycrystalline FeMnAlNi-based alloys generally exhibit poor pseudoelasticity owing to grain constraint. A promising method to improve the pseudoelasticity involves increasing the grain size by directional recrystallisation (DR). To improve the efficiency of obtaining large grain size, the effect of DR parameters—hot zone temperature (HZT) and drawing velocity—on the columnar grain size and the mechanisms of grain growth were investigated. The results showed that samples of FeMnAlNiCo shape memory alloys (SMAs) with an average grain size of over 20 mm and the largest grain size exceeding 50 mm were obtained after DR. The apparent activation energy of the columnar grain growth for DR was ≈135 kJ/mol, which was much lower than that of the equiaxed grain growth for isothermal annealing (≈384 kJ/mol). The lateral growth of the columnar grains was probably because the boundaries between columnar grains tend to form random high-angle grain (HAG) boundaries. By incremental compression test, at an applied strain of 7.0%, nearly <104> oriented single crystal exhibited a recoverable strain of ≈6.0%, while the polycrystal had a recoverable strain of only ≈3.4%. This work provides important guidance and inspires new strategies for microstructural control in FeMnAlNi-based SMAs.

Construction of a Highly Oriented Poly(lactic acid)-Based Block Polymer Foam and Its Self-Reinforcing Mechanism

Developing poly(lactic acid) (PLA)-based biodegradable polymer foams with high performance is crucial for sustainable energy conservation and the ecological environment. In this work, by applying poly(lactide-co-caprolactone) (PLCL) as a compatibilizer, the block polymer of poly(l-lactic) acid (PLLA)-b-polycaprolactone (PCL) with a long-chain branched structure was prepared by reactive processing. By utilizing the difference between the glass-transition temperature (Tg) and melting temperature (Tm) of PLA and PCL, PLLA-b-PCL-PLCL foams with a PCL chain as the foaming phase and an oriented PLLA chain as the enhancing phase were prepared by establishing a solid-phase hot drawing@supercritical CO2 foaming method. The incorporation of PLCL links significantly improved the interfacial compatibility between PLLA and PCL phases and chain entanglements, exhibiting strain-hardening behavior and leading to an improvement in the stretchability of the block polymer. In the hot drawing process in the range of Tg(PLA)–Tm(PLA), both PLLA and PCL phases were elongated along the drawing direction, and with an increasing draw ratio, the orientation factor and the crystallinity of the two phases increased evidently, accompanied by the formation of a shish–kebab crystalline structure. In the subsequent foaming process in the range of Tg(PCL)–Tm(PCL), the molecular chains of the PLLA phase were frozen and the retention of the orientation factor reached over 90%, while under CO2, crystallinity and crystallite size increased and a more perfect crystalline structure formed for the PCL phase. With an increasing draw ratio, the saturated dissolved amount of CO2 increased and the cell density and cell size of foam reached 5.13 × 109 cells/cm3 and 4.06 μm, respectively. The fibrillar structures of the PLLA phase appeared on the cell wall, while the tensile strength and modulus of foam reached as high as 65.9 MPa and 1.01 GPa, respectively. As a result, a super-strong PLA-based microcellular foam with dense micropores and highly oriented microfibrillar structures was constructed.

Effect of Nano-SiO2 on Different Stages of UHMWPE/HDPE Fiber Preparation via Melt Spinning

Ultra-high molecular weight polyethylene (UHMWPE)/high-density polyethylene (HDPE) blend with lower viscosity is more suitable for melt spinning compared to pure UHMWPE; however, the mechanical property of the blend fiber is hard to dramatically improve (the maximum tensile strength of 998.27 MPa). Herein, different content modified-nano-SiO2 is incorporated to UHMWPE/HDPE blend fiber. After adding 0.5 wt% nano-SiO2, the tensile strength and initial modulus of UHMWPE/HDPE/nano-SiO2 fiber are increased to 1211 MPa and 12.81 GPa, respectively, 21.57% and 43.32% higher than that of UHMWPE/HDPE fiber. Meanwhile, the influence of the nano-SiO2 content on the performance for as-spun filament and fiber are emphatically analyzed. The crystallinity and molecular chain orientation of as-spun filament reduces with the addition of nano-SiO2. On the contrary, for fiber, the addition of nano-SiO2 promoted the crystallinity, molecular chain orientation and grain refinement more obvious at a lower content. Furthermore, the possible action mechanism of nano-SiO2 in the as-spun filament extrusion and fiber hot drawing stage is explained.