Thermal Aging Resistance Research Articles

The role of model fatty acid and protein on thermal aging and ozone resistance of peroxide vulcanized natural rubber

The role of model fatty acid and protein on thermal aging and ozone resistance of peroxide vulcanized natural rubber

Solvent-based polychloroprene contact adhesives: effect of tackifier

Solvent-based polychloroprene (CR) adhesive was formulated using four different types of tackifiers. Wood rosin (WD), coumarone-indene resin (CI), terpene-phenolic resin (TP) and para-tert-butyl phenol-formaldehyde (TBPF) resin were incorporated with CR at various amounts say 20–50 phr (parts per hundred rubber). The effect of nature and amount of resins on adhesion strength was measured on both leather to leather and rubber to rubber joints. Results indicated that the nature of resins greatly influenced the performance of the CR adhesive. The peel strength of CR/TBPF adhesive was higher than that of CR/TP, CR/CI and CR/WD adhesives. It was found that incorporation of TBPF resin also improved the thermal ageing resistance of the bonded joints. The properties of CR/resin adhesive were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The interaction between the resin and CR was studied using FTIR spectroscopy. All the four tackifiers used were compatible with CR as confirmed by the DSC analysis.

Microstructure and electric properties of Pr-doped Pb(Zr0.52Ti0.48)O3 ceramics

Improving the piezoelectric activity of lead zirconate titanate (PZT) ceramics is of great importance for practical applications. In this study, the influence of Pr3+ doping on the ferroelectric phase composition, microstructure, and electric properties on the A-site of (Pb1-1.5xPrx)(Zr0.52Ti0.48)O3 is extensively investigated. A dense and fine microstructural sample is obtained with the introduction of Pr3+. The results show that the morphotropic phase boundary (MPB) moves to the rhombohedral phase region. The rhombohedral and tetragonal phases exhibit an ideal coexistence in the 4 mol.% Pr3+ doped (PPZT4) samples. Lead vacancy and the reduction of the potential energy barrier are considered to be the key mechanisms for donor doping, which is upheld by the Pr3+ doping. Combining the I-E hysteresis loops with the P-E hysteresis loops, it becomes apparent that both contribution maximums of the domain switching and residual polarisation are in PPZT4. Moreover, the thermal aging resistance of PZT is improved by doping, and the temperature stability is optimised from 83% in PZT to 96% in PPZT4. Hence, an appropriate amount of Pr3+ doping can effectively improve the piezoelectric activity of PZT ceramics in the MPB area and optimise the performance stability of the material under application temperatures.

Mechanical and thermal properties of PEEK composites by incorporating inorganic particles modified phosphates

This work aims to improve heat resistance and mechanical properties of PEEK composites by filling the modified phosphates with inorganic particles (Si3N4, AlN, Al2O3 and Cu2O) as reinforcements. The modified phosphate/PEEK composites were successfully prepared by pre-mixing and compression molding. The crystalline structures and compositions of modified phosphates and composites are characterized. Furthermore, the thermal and mechanical properties of composites were evaluated by thermal aging resistance at 350 °C for 24 h. The results show that all the four kinds of phosphate reinforcements can enhance the thermal aging resistance of phosphate/PEEK composites to varied extent. For the modified phosphate by Al2O3, its addition increases the 30% weight loss temperature (T30) by 55 °C. Moreover, the compressive strength exhibits a 105.6% enhancement, reaching 321.4 MPa from 156.3 MPa of the PEEK matrix. This work provides a valuable route to improve the thermal and mechanical properties of PEEK composites, which would have promise applications in heat-resistant and high-strength structural materials.

The use of recycled low‐density polyethylene films from protective prepreg for the development of nanocomposites with bentonite clay

AbstractPrepreg is a pre‐impregnated composite fiber where a thermoset polymer matrix material is present. Before being used, these materials are kept at low temperatures and have a low‐density polyethylene (LDPE) film for your protection. The increase in the use of structural composites based on prepregs causes an increase in the amount of protective LDPE film. This material is usually discarded or incinerated and can cause great damage to the environment. Thus, the present work aimed to study the feasibility of recycling up to 100% of protective LDPE (rLDPE) to develop blends‐based nanocomposites with rLDPE/virgin LDPE (60/40, 70/30, 80/20, 90/10 and 100/0) with the addition of 5 wt% of compatibilizer agent (maleic anhydride grafted LDPE, LDPE‐g‐MA), and 1 wt% of bentonite (BNT) using a co‐rotational twin‐screw extruder, followed by hot pressing in a hydropneumatic press and die‐cutting. Water absorption test, thermal aging resistance, morphological characterization by scanning electron microscopy, mechanical properties by Izod impact strength and tensile tests, and differential scanning calorimetry were performed. By the results, it was possible to verify the viability of 100% of the recycling of rLDPE. The results showed a good distribution of 1 wt% of BNT in the matrix, better mechanical properties when compared with virgin LDPE. Furthermore, the thermal properties, water absorption test, and thermal aging resistance showed no statistical differences between the samples. These results confirm the effectiveness and the environmental gain in the use of the recycled material.

К вопросу создания усовершенствованных огнестойких кабелей среднего напряжения и методов их испытаний

The article addresses problems faced in designing medium voltage fire resistant power cables. These cables must operate reliably during 30–40 years under the influence of relatively strong electric field, long-term heating up to 90 оC, and short-term heating up to 130 оC. These cables must also retain serviceability for a limited period of time when subjected to a flame source with a temperature of (830±40) оC. The article presents the key state-of-the-art electrical characteristics of these cables (dielectric strength, dielectric loss angle tangent in the delivery state, etc.), the thermal ageing resistance test procedure, the results of studies of long-term electrical strength (life curves) of fire-resistant cable models, and the fire resistance proper of results test. The article also proposes a mathematical model of the processes that take place in performing fire-resistance tests of medium voltage cables. The obtained modeling results are in qualitative agreement with the experimental data.

Improving the Thermal Aging Resistance of γ‐Vulcanized Polybutadiene Rubber (BR)/Nature Rubber (NR) Blends with Sulfur Added

In this paper, sulfur was added into polybutadiene rubber/nature rubber (BR/NR) blends for improving the resistance of thermal aging. BR/NR blends with sulfur were vulcanized by 60Co γ radiation with different irradiation doses. Afterwards, the specimens underwent thermal aging by using air oven, the non‐aged specimens without such process. It was found that the crosslink degree of BR/NR blends increased with the increase in the irradiation dose, according to the results of gel and molecular weight between crosslinks (Mc). Furthermore, the crosslink degree of BR/NR blends increased after thermal aging. This made the mechanical properties and initial degradation temperature (IDT) of aged BR/NR blends improve. Sulfur could improve thermal resistance of γ‐irradiated BR/NR blends. Finally, the possible mechanism of improved crosslink degree in aged BR/NR blends was illuminated in the paper.

Thermal aging and chemical resistance evaluation of carbon black filled natural rubber blending: effect of the composition of acrylo nitrile and styrene butadiene rubber

Natural rubber (NR) has excellent tensile and abrasion properties, but its thermal and chemical resistance needs to be improved. The present study investigates the effect of acrylonitrile-butadiene rubber (NBR) and styrene-butadiene rubber (SBR) composition in NR compounding filled carbon black (CB). The effect of chemical and heat resistance was examined by varying the addition of SBR/NBR (phr/phr) as follows 40/0; 35/5; 30/0; 25/15; and 20/20 into 60 phr (part hundred rubber) NR filled by 50 phr CB respectively. Compared with NR composites, SBR/NBR addition improved the hardness and density slightly. While tensile strength, modulus, abrasion resistance, and compression set decreased significantly. The volume, hardness, and physical properties were measured before and after 28 days of immersion in acidic, alkalis, and salty solutions. It was found that the higher loading SBR/NBR enhances chemical resistance. The hydrochloric and sulphuric acid immersion influenced the physical changes more vigorously. The thermal aging evaluation was observed by measuring the hardness and tensile strength at hot air circulation of 70°C for 24; 48 and 72 hours. The higher SBR/NBR loading could minimize the changes in hardness and tensile strength. To sum up, SBR/NBR addition improves the chemical and heat resistance on ternary blends.

Research on electric thermal aging resistance new energy material transformer oil based on steady quality engineering technology

The aim of this study was to investigate the electrical resistance of polycarbonate film and polyester film materials in new energy materials during electrothermal aging in transformer oil. Insulating paper was used as a comparative material to compare the breakdown voltage and initial voltage of insulating paper, polycarbonate film, and polyester film in electrothermal aging at 90 °C, 110 °C, and 130 °C. The best performance in the test was achieved by polycarbonate film, followed by polyester film, while the worst performance was that of insulating paper. Polycarbonate film can be used as an insulating material in transformers, and it has great application value and commercial prospects.

Thermoplastic polyurethane-cellulose nanocomposite for transparent armour: Characterisation of adhesion and thermal aging

Environmental degradation of transparent thermoplastic polyurethane (TPU) is an issue of growing concern. Measured increased in the mechanical properties of nano-reinforced TPUs have been reported, however, limited research is available regarding their adhesive properties and resistance to environmental aging. By incorporating cellulose nanocrystals (CNCs) into a TPU via planetary ball milling, an increase to both the mechanical and adhesive properties was obtained. The TPU/CNC nanocomposite showed bond integrity and lap shear strengths were increased by 34% and 25% respectively relative to the unmodified nanocomposite, and further improvements in mechanical performance were seen. The TPU/CNC nanocomposite showed higher melting temperature and increased melting enthalpy indicating improved thermal aging resistance. The restriction of TPU segments and changes in chemical bond state and crystallinity were identified as key mechanisms driving performance improvements.

Improved Electrical and Thermal Aging Properties of DBSA-Doped PANI Using MWCNT and GO

Electrical conductivity deterioration of polyaniline (PANI) at elevated temperatures has limited its applications for commercial usages. In this study we endeavored to improve the thermal aging resistance of PANI and its conductivity stability at elevated temperatures using a high molecular weight dopant, dodecylbenzenesulfonic acid (DBSA), along with the addition of carbon-based nanoparticles. DBSA-doped PANI (DBSA-PANI) and its nanocomposites with graphene oxide (PANI/GO) and multi-walled carbon nanotube (PANI/MWCNT) were prepared through in situ polymerization. The samples were aged at 90°C up to 1000 h and characterized by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), and electrical conductivity measurements. It was observed that electrical conductivity deteriorates more rapidly in DBSA-PANI than in GO and MWCNT nanocomposites. The FTIR results confirmed a strong retention of DBSA groups in the nanocomposites after aging, but not for DBSA-PANI. This showed more stability of DBSA dopant in PANI/GO and PANI/CNT. The characteristic time (τ), as a criterion for thermal stability, was found to be 91, 172, and 295 h for DBSA-PANI, PANI/MWCNT, and PANI/GO, respectively. It was suggested that the retardation of the de-doping process is the major reason for the higher τ value and more electrical conductivity stability of PANI/GO. The obtained thermal stability for the electrical conductivity of DBSA doped PANI/GO nanocomposites was nearly 30 times higher than that of HCl-doped PANI.

Reinforcement of Bakelite Moulding Powder in Acrylonitrile Butadiene Rubber (NBR): In Comparison with Cashew Nut Oil Modified Phenolic Resin

The influences of two phenolic resins, that is, cashew nut oil modified phenol-formaldehyde resin (CN-m-PF) and Bakelite moulding powder (BMP), on properties of carbon black filled acrylonitrile butadiene rubber (NBR) were investigated and compared. Processability, cure characteristics, mechanical properties, thermal ageing resistance, and oil resistance of the NBR filled with various contents of phenolic resins (0-60 phr) were determined. The addition of both resins leads to a prolonged cure time with a greater value of torque difference. Regardless of the resin type, the improvement of compound processability and the enhancement of modulus and hardness of the NBR vulcanisates are observed with increasing resin content. However, many mechanical properties such as tensile strength, elongation at break and abrasion resistance are deteriorated. Thermal ageing resistance of the NBR vulcanisate is slightly improved in the presence of both resins, probably due to the dilution of NBR with the high heat-resistant phenol-formaldehyde resins. Results also disclose that all NBR vulcanisates demonstrate excellent oil resistance, regardless of the resin type and content. At any given resin content, CN-m-PF gives a better processability, higher stiffness and greater mechanical properties than BMP. However, due to its lower cost, BMP can be used to enhance stiffness of NBR vulcanisates without the risk of processing problem.

Study of radiation-induced amorphization of M23C6 in RAFM steels under iron irradiations

The mechanical properties of reduced activation ferritic/martensitic steels (RAFMs) such as creep, thermal aging, and irradiation resistance are improved by the formation of MX and M23C6 particles. However, it is well known that these particles are unstable under irradiation. The purpose of the present study is to clarify the details of the radiation-induced amorphization (RIA) of M23C6 in F82H steels. The instability behavior of M23C6 under a wide range of irradiation temperatures from R.T. to 773 K and various ion beam energies (2.8, 3.7, 6.4 and 10.5 MeV) was systematically investigated. Two types of materials, F82H and its model alloy (F8), were utilized in this study. TEM observation and selected area electron diffraction analysis before and after irradiation were conducted to evaluate the occurrence of RIA, and the chemical composition was analyzed to reveal the possible relation between atom displacement/diffusion and RIA. In the case of the iron irradiation at the temperature below 598 K, a bilayer contrast of the particle, consisting of an amorphous-rim phase and inner crystalline core, was observed. Similar particle survived in the irradiated F82H at the temperature of 623 K, the RIA was not observed in the F8 specimen. Consequently, the critical temperature of RIA was estimated as 623–673 K. Since the melting temperature (Tm) of M23C6 is approximately 2173 K, the critical temperature corresponds to ∼0.29 Tm. From the STEM-EDS analysis, the Fe/Cr ratio of the particle decreased with increasing irradiation temperature in the range of 573–623 K. This behavior was qualitatively explained by the formation of the amorphous phase. It is clarified that the occurrence of the RIA of M23C6 particle can be evaluated by the variation of Fe/Cr ratio.

Oil-water separation through an ultrahydrophobic filter paper developed by sol-gel dip-coating technique

Eco-friendly oil–water separation substrates are mostly recommended in the present context of the world. In the present work, biodegradable and more economical ultrahydrophobic composite material was synthesized by sol–gel method using silica nanoparticles (SiO2) and poly (methyl methacrylate-co-ethyl acrylate) polymer (PMMA) with 1H,1H,2H,2H Perfluorooctyltrichlorosilane (PFOTS) coupler, and coated on 40-grade cellulose filter paper with a dip-coating method. As-prepared surfaces achieved static contact angle more than 175° and sliding angle 3.8°. The microstructure and chemical composition of ultrahydrophobic filter paper were characterized by scanning electric microscopy (SEM), X-ray spectroscopy (EDX), and Flourier transformation infrared spectroscopy (FTIR), respectively. The coated filter paper accomplished 98% oil–water separation efficiency by filtering different oils. Besides, the SiO2 nanoparticles were enhanced the thermal and UV aging resistance. The coated surfaces also showed excellent chemical inertness, and mechanical durability tested. This research work can be employed yet for domestic and industrial applications at a large scale for oil–water separation and self-cleaning.

SURFACE QUALITY COMPARISON BETWEEN TRADITIONAL AND ONE STEP PRODUCTION CYCLE

Surface quality behaviour was investigated for one step production system compared to traditional painting process. This study was conducted to compare and analyse the effect of one step production cycle on surface quality when compared with traditional production system. Sample plates were prepared by traditional painting process with acrylic solvent based paint and one step production cycle with polyurethane (PU) coating systems. Surface quality of plates were analysed regarding scratch resistance, thermal aging resistance and orange peeling formation. Test methods were determined according to Fiat painted plastic part qualification norms. Test results revealed that gloss loss, roughness values and orange peeling formation affinity were less for one step production system with PU than conventional system with solvent based acrylic paint. This study contributes to revealing surface quality performance for the methods of producing painted parts that are more resistant to scratch, thermal conditions and having much fewer surface defects like orange peeling.

THE EFFECT OF CARBON BLACK COMPOSITION IN STYRENE BUTADIENE RUBBER AND NATURAL RUBBER BLENDING TOWARDS ITS AGEING AND ORGANIC SOLVENT RESISTANCE PROPERTIES

In terms of enhance thermal ageing resistance of natural rubber (NR) based products, it is common to blend NR with styrene butadiene rubber (SBR) to produce binary blends with higher thermal properties. However, reinforcement filler such as carbon black (CB) commonly added to improve physcomechanical properties of the blends. Thus, this present study investigated the effect of CB composition in SBR/NR binary blending towards its thermal ageing resistance and organic solvent resistance. CB was compounded 35 up to 75 phr into SBR/NR (50/50 phr), the standard procedure ASTM D-3182 was applied. The result show that hardness value increase significantly due to the higher addition CB. Conversely, the higher CB composition in SBR/NR binary blends cause quite significant the decreasing value of tensile strength and elongation at break. The effect of thermal aging properties was observed at dry air circulation at 70 o C for 48 hours. It is found that thermo-oxidative ageing cause a serious damage on the surface as well as decrease the hardness, tensile strength and elongation at break of the rubber vulcanizates. However, the effect of CB addition towards the decreasing value of those properties could not be seen clearly. In addition, toluene immersion for 24 hours cause the mass loss up to about 5% weight of the NR/SBR binary blends, whereas iso-octane and n-hexane immersion cause slight mass changes only approximately 0,1 % weight.

Enhancing viscoelastic and mechanical performances of natural rubber through variation of large and small rubber particle combinations

There have been several reports investigating independent properties of large- (LRP) and small rubber particles (SRP). This work envisaged that, when co-existing, they could offer exceptional viscoelastic and mechanical properties from both components. Latex samples of various mixing ratios were prepared and properties of their rubber films were investigated against those of pure LRP and SRP to find that those containing 10–30% SRP were the best in mechanical strength and elasticity. This could be due to the combination of stronger phospholipid linkages in the LRP and void-filling ability of the SRP. The presence of SRP was shown to enhance curability in the vulcanised samples resulting in better mechanical performance of the vulcanisates. The 70/30 (LRP/SRP) blend showed the best thermal aging resistance among the vulcanisates. This suggested that the mixing ratios of the LRP and SRP contents were tunable to improve desirable properties of rubber products of interest, both green and cured.

Improvement of high-temperature thermal aging reliability of Ag–Au joints by modifying Ni/Au surface finish

Sintering Ag paste on Ni/Au surface finish (Ag–Au joint) is a hot topic because Ni/Au surface finish is one of the most commonly used metallizations in the electronics industry. However, it is still difficult to achieve a reliable Ag–Au joint after high-temperature thermal aging due to severe Ag–Au interdiffusion. In this work, we investigated thermal aging reliability of Ag–Au joint via high-temperature storage at 250 °C up to 1000 h. The Ag–Au joints with 0.1 and 0.8 μm Au layer coated substrates were compared to study the Au layer thickness effect on thermal aging reliability of joints, and a substrate preheating treatment was proposed to improve thermal aging reliability of Ag–Au joint. The result clearly shows that preheating treatment can improvement of bonding performance including thermal aging resistance and initial shear strength for both the thickness of Au layer. The shear strength of 1000 h thermally aged Ag–Au joint with the 0.1 and 0.8 Au substrate has been further improved to 11.7 and 16.5 MPa via the substrate preheating treatment, respectively. The substrate preheating treatment can lead to further growth of Au grains by eliminating fine grains, which results in the improvement of thermal aging reliability of joints. In addition, the thicker Au layer showed superior thermal aging reliability. This is attributed to the thicker Au layer less susceptive to massive Ag–Au interdiffusion and can prohibit severe oxidation of Ni because it hosts larger Au grains and fewer grain boundaries. The study would provide a convenient way to improve the thermal aging reliability of Ag–Au joints.

Probing the Damping Property of Three‐Dimensional Graphene Aerogels in Carboxylated Nitrile Butadiene Rubber/Polyurethane Blend

Three‐dimensional (3D) graphene aerogel (GA) with a spatial porous structure and network skeleton was facilely prepared via one‐step self‐assembly hydrothermal reduction. Such network structure is regarded as a critical advantage in resolving the dispersion of graphene in polymer matrix, thereby enhancing the damping property. Here, as‐prepared GA was added to the carboxylated butadiene nitrile rubber/polyurethane blend (XNBR/PU) by melting/mechanical complex method. Their dynamic mechanical properties were investigated in detail, and the relationship between thermal aging and dynamic mechanical properties had also been studied. Finding that the storage modulus and loss modulus of XNBR/PU were continually improved with the increase in addition amount of high‐performance GA, reaching 3,219 and 316 MPa with the content of 3 wt% GA, respectively. Loss factor (tanδ) of XNBR/PU with GA shows two sets of maximum values (0.22 and 0.61) at around −25 and 0.6°C, respectively. Results illustrate that GA can greatly improve the damping performance, damping temperature range, mechanical properties, and thermal aging resistance of XNBR/PU blend, mainly depending on the performance characteristics of GA and interface interaction between GA and XNBR/PU. Verifying that GA with 3D network structure holds a great prospect for damping materials. POLYM. ENG. SCI., 60:61–70, 2020. © 2019 Society of Plastics Engineers

Insight into a concentration-sensitive red-emitting phosphor Li2Ca4Si4O13:Eu3+ for multifunctional applications: Crystal structure, electronic structure and luminescent properties

Lithium-containing silicate compounds have attracted so much attention in recent years for applications in energy storage and illumination source due to their rigid structure and good electrical conductivity. In this study, a Eu3+ doped lithium-containing silicate red phosphor, Li2Ca4Si4O13:Eu3+, was explored by using structural computational simulations and systematic experiments for multifunctional applications. As a result, due to the quite non-central symmetry of the Ca2+ sites (C1 symmetry), the strong 4f-4f excitations in near ultraviolet region were observed. Under near ultraviolet and cathode ray light excitation, Li2Ca4Si4O13:Eu3+ phosphor has an efficient red emission with good thermal stability and ageing resistance. Furthermore, Li2Ca4Si4O13:Eu3+ phosphor exhibits a concentration-sensitive behavior induced by the change of site symmetry. The results show that it is feasible to develop near-ultraviolet and cathode ray light excited red phosphors in lithium-containing silicate compounds.