Low Temperature Impact Strength Research Articles

Maintaining modulus of polypropylene composites with ultra-high low temperature toughness by synergistic branched polyethylene and nucleating agents

In this work, the synergistic effect of highly branched polyethylene (HBPEs, s = 1, 2) elastomers featuring dendritic structure and α-type nucleating agents (NA1, NA2) on the toughness and stiffness of block polypropylene (PP–B) was investigated. Blends of PP-B/HBPE/nucleating agent ternary systems were prepared, yielding materials with exceptionally high low-temperature toughness and minimal stiffness loss. The results indicate that HBPE enhances the low-temperature impact strength of the system but leads to a reduction in modulus. After the addition of the nucleating agent, both the low-temperature toughness and stiffness of the blend are improved simultaneously. The PP-B/HBPE2/NA2 (90/10/0.2) blend achieves the optimal balance between low-temperature toughness and stiffness, with its low-temperature impact strength increasing by a factor of 7 compared to PP-B, reaching 56.9 kJ/m2, and a bending modulus of 1110 MPa, nearly identical to PP-B. Dynamic mechanical properties and phase morphology results indicate that HBPE reduces the glass transition temperature of the rubber phase in the blended system and exhibits good compatibility with PP-B. Analysis of the crystallization behavior reveals that the significant increase in the crystallization temperature of PP-B and the substantial reduction in the size of spherical particles observed in PP-B/HBPE/NA blends are facilitated by NA1 and NA2. Additionally, NA1 and NA2 promote the transformation of the PP-B matrix into α-type crystals and enhance the crystallinity of PP-B.

Structural Anisotropy Parameters’ Effect on the Low-Temperature Impact Strength of Alloy Steels in Rolled Products

The present work is devoted to the study of the influence of the parameters of the structural anisotropy of rolled products on the low-temperature impact strength of alloyed steels. A quantitative metallographic analysis of the microstructure of rolled steel samples obtained after testing for low-temperature toughness was carried out. It was established that the main reason for the decrease in the low-temperature impact strength of rolled steel samples is a highly developed segregation band enriched with carbon films formed at the stage of steelmaking conversion in violation of the technology of continuous casting of steel. The microstructural analysis of rolled stock samples was used in the work, and studies of the fracture surface of rolled stock samples were carried out with a scanning electron microscope using X-ray microanalysis methods. The studies carried out showed that the metallurgical quality of sheets of one heat, as well as individual samples within one sheet, varied over a wide range, from satisfactory to unacceptably low. It was established that the main reason for the decreasing low-temperature impact strength of rolled products was a highly developed segregation band enriched with carbon films, formed at the stage of steelmaking in case of violation of the continuous casting of steel technology. The multivariate statistical analysis carried out showed that only the size of the segregation band has an effect on the low-temperature impact strength of 10 mm thick rolled coil samples.

New low‐temperature resistant shape memory elastomer: Ethylene‐octene copolymer/methyl vinyl silicone rubber composites

AbstractA new series of thermoplastic elastomers were fabricated in this study employing ethylene‐octene copolymer (POE) and methyl vinyl silicone rubber (MVQ) as the thermoplastic phase and the elastomeric phase, respectively. The effect of POE/MVQ blending ratios on the vulcanization, mechanical, and thermal properties, cold resistance, shape memory properties, and hydrophobicity of the thermoplastic composites was investigated. Moreover, specific properties such as low‐temperature impact (LTI), shape memory and hydrophobicity properties exhibited by the POE/MVQ thermoplastic composites were studied in detail. The results indicated that the POE/MVQ composites exhibited remarkable mechanical properties and LTI strength. With the MVQ content reaching 10 phr, their tensile strength reached 30.07 MPa, significantly higher than that of pure POE. Regarding shape memory properties, the shape fixing ratio and the shape recovery ratio were 97.6% and 94.3%, respectively, at the MVQ content of 40 phr.

Microporous-micronucleus composite structure endowing heterogenous polyamide 6 with low-temperature toughness, low dielectric constant, fire retardancy and antibacterial activity

Utilizing the difference in compatibility and phase transition among PA6, monoglyceride (MG), octaphenylsilsesquioxane (OPS) and zinc diethylphosphinate (ZDP), a PA6 composite with microporous-micronucleus structure is simulated and designed. Due to the passivation micro-cracks effect of microporous-micronucleus structure, the MG/OPS/ZDP/PA6 composite exhibits excellent low-temperature impact strength (5.58 kJ m−2, 203.3% higher than neat PA6 at −170 °C). The nano-gap and nano-cage OPS endows the MG/OPS/ZDP/PA6 with low dielectric constant (2.95 at 100 Hz). The thermal insulation effect of micropores and the synergistic effect of OPS and ZDP in the micronucleus lead to the high flame retardancy of MG/OPS/ZDP/PA6. Meanwhile, the MG on the inner surface of the micropore and the ZDP in the micronucleus endow a dual antibacterial activity. This work provides a guideline for the construction of microporous-micronucleus structure to realize the functional design of composite.

Toughening of linear low-density polyethylene/brominated polystyrene blend by styrene-ethylene/butylene-styrene elastomer

Brominated polystyrene (BPS) is blended with linear low-density polyethylene (LLDPE) to improve its fire retardancy for various applications such as wire and cable covering. To improve compatibility and mechanical properties, styrene-ethylene/butylene-styrene (SEBS) copolymer was added as a compatibilizer. The influence of processing temperature and SEBS elastomer on morphology, interfacial and mechanical properties has been investigated. It was found that melt blending at 230 °C with addition of SEBS elastomer can significantly reduce the BPS particle size to less than 0.5 μm by forming a core-shell structure that enhances the interfacial strength between BPS and LLDPE phases. Addition of 8 phr SEBS elastomer can increase the Izod impact strength at −37 °C by a factor of nearly three, compared to the non-compatibilized LLDPE/BPS system. Double-notch four-point bending (DN-4PB) test reveals that crazing and shear banding are two primary toughening mechanisms for the observed increase in the low temperature impact strength.

Study of structure of high-strength cold-resistant steel after quenching and tempering

The conditions of heat treatment, providing achievement of high strength characteristics (σ0,2 ≥ 600 N/mm2) in combination with low-temperature impact strength (KCV−60 ≥ 50 J/cm2) and plasticity (δ5 ≥ 17 %), were determined for the new weldable sparingly alloyed steel 20G2SMRA. Steel structure was formed after hot rolling, quenching from the temperature 860 °С and consequent high tempering at the temperature 600 °С (which determined the obtained complex of steel properties) and then was examined via the method of scanning electronic microscopy. The results of energy-dispersion analysis of carbide particles which were extracted during tempering of quenched steel are presented. It is shown that the required level of strength and cold resistance is provided due to forming of mainly finedispersed lath martensite (with α-phase lath width 0.2–0.7 μm) and with small part of residual austenite (about 1 %), as well as dislocation high-temperature martensite. Sub-grain α-phase structure (with size of single sub-grains 0.1–0.7 μm) and cementite-type of carbide particles are formed during tempering. The research was carried out under financial support of the RF Ministry of Education and Science within execution of the RF President’s grant (Agreement No. 075-15-2020-205/1 dated 29.03.2021 (int. No. MK-1979.2020.8/1)).Electron microscope examination of foils for clearance were conducted within the boundaries of the State assignment for the theme “Structure”, State reg. No. АААА-А18-118020190116-6.

The study of influence of heat treatment procedures on structure and properties of the new high-strength steel with increased cold resistance

The study of influence of different heat treatment procedures on microstructure and mechanical properties of the new high-strength weldable cold-resistant steel 20G2SMRA (20Г2СМРА) is conducted. Morphology of martensite after steel quenching, as well after quenching and consequent tempering, is examined using optical metallography and electron microscopy. Regularities of varying of microstructure parameters, hardness values (HV1) and impact strength KCV were revealed in this work at the temperature –60 °С depending on heating temperature for quenching and consequent tempering. Amount of residual austenite after quenching starting from the temperatures 850, 950 and 1000 °C was determined using X-ray structural phase analysis. The rational procedure of heat treatment was established as a result of the study; it provides combination of guaranteed yield strength σ0,2 ≥ 600 N/mm2 together with low-temperature impact strength KCV–60 ≥ 50 J/sm2 and ductility δ5 ≥ 17%. The obtained results of investigation are aimed for commercial putting into practice in the conditions of heavy plate production at 5000 rolling mill of Magnitogorsk Iron and Steel Works (MMK). The work was done under financial support of the RF Ministry of Education and Science within the framework of execution of the grant of RF President (Agreement No. 075-15-2020-205 dated 17.03.2020 (int. No. MK-1979.2020.8)).

Choosing the Rational Heat Treatment Conditions for High-Strength Cold-Resistant Weldable Steel with Yield Strength of more than 600 N/mm2

Rational heat treatment conditions for the new weldable cold-resistant steel grade 20G2SMRA ensuring a guaranteed yield strength σ0,2 ⩾ 600 N/mm2 combined with the lowtemperature impact strength KCV-60 ⩾ 50 J/cm2 have been searched. The effect of various quenching and tempering conditions on the steel microstructure parameters, hardness, and impact strength at a temperature of -60 °C has been studied. The dependencies of the microstructure parameters, hardness (HV1), and impact strength (KCV-60) on the quenching and subsequent tempering temperature are represented. Rational heat treatment conditions have been found for a new weldable cold-resistant steel with high yield strength.

Experience of Mastering in NLMK Dansteel Production of Arctic Usage High-Strength Microalloyed Steels F240, F460, and F500 for Shipbuilding and Marine Structures

Shipbuilding remains one of the most metal-consuming segments of the transport industry. For various types of vessels there is a trend of a successive increase in specifications for the specific volume of freight transport that predetermines an increase in the use of materials for construction, including thick steel plate. Considering the general trends in development of the thick plate market for shipbuilding, NLMK DanSteel has mastered production technologies for rolled product up to 35 mm thick produced from low-carbon microalloyed extra high-strength steels F420, F460, F500 intended for vessels of various types for Arctic application. Pilot plant, certified and industrial batches of heavy plates have shown a high level of strength, low-temperature impact strength at – 60°C, and a high level of welded joint mechanical properties employing various welding methods with heating input in the range from 15 ± 1 to 50 ± 2 kJ/cm. The results obtained provide NLMK DanSteel with favorable certification test results for production of extra high-strength grades F420, F460, F500 and their analogs in thickness up to 35 mm according to the IACS rules and confirm the quality of heavy plates in accordance with the requirements of DNV-GL and other marine certification association classification programs and standards.

Effects of thermo-oxidative aging on structure and low temperature impact performance of rotationally molded products

In this work, the effects of thermo-oxidative aging on the microstructure and impact properties of polyethylene during the rotational molding process were studied. FTIR and Raman analysis showed that the degradation of polyethylene was responsible for the low-temperature impact strength (LT-IS) and the brittle fracture behavior of samples those subjected to prolonged heating time during rotational molding process. The DSC and polarizing microscope analysis showed that the degradation process was delayed by the addition of antioxidants. Through use and optimization of antioxidants, the thermo-oxidative aging of polyethylene can be modulated, a broader processing window can be achieved, and the products may exhibit better mechanical properties with a wider heating time range.

Production of corrosion-resistant S420K2W and S460K2W structural steel

The alloying of steel resistant to atmospheric corrosion is discussed. The differences and similarities of the Russian GOST, European EN, and United States ASTM standards regarding the chemical composition of such steel are analyzed. The prospects for the production of corrosion-resistant high-strength steel sheet exceeding the requirements in the EN 10025-5 standard are considered. In trials, the possibility of producing steel sheet with elevated low-temperature impact strength is demonstrated. Production technology for high-strength steel resistant to atmospheric corrosion is developed.

Study on Performance of PP/POE <i>In Situ</i> Compatibilization

By the in situ compatibilization, PP/POE blends were prepared with dicumyl peroxide (DCP) as initiator, Trimethylolpropane triacrylate (TMPTA) as co-during systems and the metallocene polyolef in elastomers ploy (ethylene-1-octene) (POE) as toughening rubber. The effects of additive amount for TMPTA、POE on the mechanical properties were studied. The results showed that the maximum value of the room-temperature and low-temperature impact strength for the composite was reached to 52.03KJ/m2 and 37.29KJ/m2, and the elongationfor was reached to 482.74%.

Crystallization behavior and mechanical properties of nano-CaCO3/β-nucleated ethylene-propylene random copolymer composites

To provide ethylene-propylene random copolymer (PPR) with balanced mechanical properties, !-nucleating agent and CaCO3 nanoparticles are incorporated into PPR matrix by melt blending. It is found that crystallization rate and relative content of !-crystal increase with the addition of !-nucleating agent together with nanoparticles. Size of PPR spherulite is greatly reduced, and a specific morphology appears, in which #-crystal lamella is grown upon the !-nucleus. The results suggest that both !-nucleating agent and nano-CaCO3 have heterogeneous nucleation and synergistic effects on !-nucleation of PPR. Mechanical characterization shows that mechanical properties of PPR can be tuned by incorporation of !-nucleating agent and nano-CaCO3 particles. Under suitable compositions, low temperature impact strength and high temperature creep resistance of PPR, the bottlenecks of application of such material, can be simultaneously improved with- out sacrificing the Youngs'modulus and tensile strength.

Mechanical and optical effects of elastomer interaction in polypropylene modification: Ethylene-propylene rubber, poly-(ethylene-co-octene) and styrene-butadiene elastomers

The interaction between binary combinations of three different elastomer classes commonly applied in impact modification of isotactic polypropylene (iPP) was studied. Blends based on a homogeneous ethylene-propylene (EP) ran- dom copolymer (EP-RACO) and a heterophasic EP impact copolymer comprising ethylene-propylene rubber (EPR) with different external elastomer types, one homogeneous ethylene-1-octene copolymer (EOC), and two hydrogenated styrene- butadiene-styrene triblock copolymers (SEBS) with different styrene content, were prepared. The phase morphology, mobility as a function of temperature, mechanical and optical properties were studied. Special effects could be achieved for the combination of two different elastomer types. The results clearly demonstrate the possibility to achieve attractive prop- erty combinations in ternary systems consisting of a crystalline PP matrix and two different types of elastomer, EPR or EOC on the one hand and SEBS on the other hand. A combination of density matching and compatibilization effects allows reaching good low temperature impact strength together with a transparency close to matrix level when selecting a butadi- ene-rich SEBS type.

Effect of SBS Content on Low Temperature Impact Strength, Morphology and Rheology of PP-cp/SBS Blends

Izod impact strength of PP impact copolymer/Styrene-Butadiene-Styrene blends were evaluated at varied sub-zero temperatures and demonstrated 12 times enhancement in impact strength of 40% SBS containing blend over pure PP-cp at −40°C. SBS content played a vital role in morphology development as it changes from droplet morphology to elongated ellipsoid to a seemingly networked structure leading towards different fracture mechanisms. Rheological properties of blends evaluated on capillary rheometer showed pseudoplastic behavior at varied shear rates (50 − 104 s−1) at 220°C and good agreement between experimental shear viscosity and theoretical values as per log additivity principle at high shear rates.

Evolution of properties in ABS/PA6 blends compatibilized by fixed weight ratio SAGMA copolymer

Blends of acrylonitrile-butadiene-styrene (ABS) and Nylon 6 (PA6) incorporating styrene-acrylonitrile-glycidyl methacrylate (SAGMA) copolymer as compatibilizer have been studied across five different compositions by varying the PA6 ratio from 15 wt% to 55 wt%. The evolution of morphology from discrete dispersed PA6 particles to phase inversion to co-continuous phases effected due to the compatibilizer have been studied vis-a-vis preliminary melt flow analysis, viscoelastic behavior, physico-mechanical and thermal properties of the blends. Single point viscosity measurements during melt flow analyses are indicative of a significant increase in viscosity upon initial incorporation of PA6 followed by narrow increases with content. It is observed that while there are gradual positive modifications in physico-mechanical properties with increasing PA6 content, the most significant improvements are observed for room temperature izod impact strength and break elongation effected in the region of phase inversion on to the formation of a co-continuous phase. The low temperature impact strength at −40 °C essentially remains comparable to that of control ABS. DMTA analysis evidences partial dissolution of the blend components by the shifts of the damping peaks (Tg) of PB rich phase, SAN and PA6. Broadening of the damping peak of PB rich phase of ABS is attributed to increasing interfacial region due to PA6-g-SAGMA molecular layer at the interface. Thermal stability of the blends were not significantly affected in comparison to control ABS and PA6.

Low Temperature Izod Impact Studies of Blends Based on Impact Grade Polypropylene and Ethylene-α-Octene Copolymer

With an aim to enhance low temperature impact strength, blends of PP-cp (Impact Grade PP) and metallocene-catalyzed plastomer (EXACT® ethylene-α-octene copolymer) were prepared using a co-rotating, intermeshing twin-screw extruder in 90 : 10, 80 : 20, 70 : 30, and 60 : 40 weight ratio. Rheological properties studied by Haake’ single-screw extruder with torque rheometer attachment and capillary die showed pseudoplastic melt behavior at 220°C in the shear rate range of 400—4000 s—1. Density and MFI determinations showed minimal change. Morphology studied by low voltage scanning electron microscope (LVSEM) of blend samples showed distinct biphasic blend morphology wherein PP-cp as continuous phase and plastomer as spherical domains (0.5—2 μm size) with stabilized distribution and dispersion. Izod impact strength of the blends at varied temperatures (23, 0, -10, -20, -30, and -40°C) showed substantial enhancement in low temperature impact strength compared to the base polymer (from 44 J/m in case of pure PP-cp to 539 J/m in case of 40% plastomer blend at -40°C).

Fracture characteristics and deformation behavior of heterophasic ethylene–propylene copolymers as a function of the dispersed phase composition

The deformation and fracture behavior of in reactor produced heterophasic copolymers, comprising a polypropylene (PP) matrix and an ethylene propylene copolymer (EPC) dispersed phase, have been studied as a function of the dispersed phase composition (ethylene/propylene ratio). Conventional and instrumented Charpy as well as instrumented drop weight tests were employed to quantify the response of the materials to impact loading. Scanning and high-voltage electron microscopy was used for characterization of the deformation mechanisms. Decreasing ethylene content of the EPC led to an enhancement of the matrix/dispersed phase compatibility, reduction of the dispersed phase particle size and therewith to a systematic increase of the impact strength at room temperature and a decrease of the brittle-to-tough transition temperature ( T BTT) of the materials. The low temperature impact strength was predominantly dependent upon the glass transition temperature of the EPC phase. The results are discussed from the viewpoint of interfacial interactions, size and spatial packing of the dispersed phase domains and the observed deformation mechanisms.

Blends of polycarbonate and ethylene-1-octylene copolymer

The mechanical properties and morphology of polycarbonate/ethylene-1-octylene copolymer (PC/POE) binary blends and PC/POE/ionomer ternary blends were investigated. The tensile strength and elongation at break of the PC/POE blends decreased with increasing the POE content. The impact strength of the PC/POE blends showed less dependence on thickness than that of PC. And the low-temperature impact strength of PC was modified effectively by addition of POE. The morphology of the PC/POE blends was observed by scanning electron microscope. The PC/POE weight ratio had a great effect on the morphology of the PC/POE blends. For the PC/POE (80/20)/ionomer ternary blends, low content (0.25 and 0.5 phr) of ionomer could increase the tensile properties of PC/POE (80/20) blend and had little effect on the impact strength. And 0.5 phr ionomer made the dispersed domain distribute more uniformly and finely than the blend without it. But with high content of ionomer, the degradation of PC made the mechanical properties of the blends deteriorate. Blending PC and ionomer proved the degradation of PC, and the molecular weight decreased with increasing the ionomer content.

Compatibilization of PP/EPDM Blends via a Hexa Functional Coupling Agent and Peroxide During Reactive Extrusion

Isotactic polypropylene (PP) and ethylene-propylene-methylene-norbornene terpolymer (EPDM) were blended in a counter-rotating twin screw extruder in the presence of a peroxide initiator and a new multifunctional coupling agent (hexa(allylamino)cyclotriphosphonitrile (HAP)). The effects of free radical coupling reactions on the mechanical properties and morphologies of the resultant blends were evaluated. Blends that included both HAP and peroxide displayed an increase in low temperature impact strength. Tapping-mode atomic force microscopy(AFM) of the alloys revealed enhanced dispersion of EPDM within the PP matrix when compared to the base blends.