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The aim of this study was to fabricate polyimide (PI)/Al₂O₃ composite films via surface modification and ion exchange techniques, and examine their properties.

The method involves hydrolyzing the PI film double surface layers in an aqueous potassium hydroxide (KOH) solution and incorporating aluminium ions (Al3+) into the hydrolyzed layers of the PI film via subsequent ion exchange, followed by a treatment of the Al3+-loaded PI films with an aqueous ammonia solution, which leads to the formation of Al(OH)₃ in the surface-modified layers. After a final thermal annealing treatment in ambient air, the Al(OH)₃ decomposes to Al₂O₃, and forms composite layers on both surfaces of the re-imidized PI film.

The PI/Al₂O₃ composite film obtained with a 6 hours of KOH treatment exhibited excellent thermal stability, good mechanical properties and better electric breakdown strength and corona-resistance properties than the pristine PI film.

The method for obtaining the composite films in this paper is worth consideration, but additional research will be needed. Furthermore, this method is of general importance for the fabrication of composite PI films with tailored properties.

This study showed that surface modification and ion-exchange techniques are powerful methodologies for the fabrication of PI/Al₂O₃ composite films.

The purpose of this paper was to comprehensively understand the effects of imidization process on the structure and properties of polyimide (PI) films through the preparation and characterization of a variety of PI/aluminium oxide (Al₂O₃) nanocomposite films by using several imidization-based strategies.

Poly(amic acid) (PAA) containing different amounts of inorganic materials (namely, 0 Wt.%, 4 Wt.%, 8 Wt.%, 12 Wt.% and 16 Wt.%) was synthesized by using pyromellitic dianhydride and 4,4-diaminodiphenyl ether as raw material and N,N-dimethylacetamide as solvent. Subsequently, the solution obtained was casted on a glass substrate and dried by the means of various curing processes. The micro-structure, Fourier transform–infrared spectral features, breakdown field strength, dielectric properties and the corona-resistant time parameters of films were achieved.

The imidization process influences substantially the properties of composite films. Therefore, as the imidization rate is increased, the corona-resistant time and the electrical breakdown strength of composite films are also improved, while the dielectric constant faces a+ decreasing.

In this paper, the impact of imidization process on the performance of PI/nano-Al₂O₃ three-layered composite film is reported. However, there are multiple factors governing these systems (such as, interlayer thickness ratio and humidity), which are not discussed herein.

The current study expounds the relationship between imidization ratios as well as the effect of imidization ratio on the performance of the film.

TO say that the Twenty‐fourth S.B.A.C. Show was an unqualified success is perhaps to gild the lily. True there were disappointments— the delay which kept the TSR‐2 on the ground until well after the Show being one—but on the whole the British industry was well pleased with Farnborough week and if future sales could be related to the number of visitors then the order books would be full for many years to come. The total attendance at the Show was well over 400,000—this figure including just under 300,000 members of the public who paid to enter on the last three days of the Show. Those who argued in favour of allowing a two‐year interval between the 1962 Show and this one seem to be fully vindicated, for these attendance figures are an all‐time record. This augurs well for the future for it would appear that potential customers from overseas are still anxious to attend the Farnborough Show, while the public attendance figures indicate that Britain is still air‐minded to a very healthy degree. It is difficult to pick out any one feature or even one aircraft as being really outstanding at Farnborough, but certainly the range of rear‐engined civil jets (HS. 125, BAC One‐Eleven, Trident and VCIQ) served as a re‐minder that British aeronautical engineering prowess is without parallel, while the number of rotorcraft to be seen in the flying display empha‐sized the growing importance of the helicopter in both civil and military operations. As far as the value of Farnborough is concerned, it is certainly a most useful shop window for British aerospace products, and if few new orders are actually received at Farnborough, a very large number are announced— as our ’Orders and Contracts' column on page 332 bears witness. It is not possible to cover every exhibit displayed at the Farnborough Show but the following report describes a wide cross‐section beginning with the exhibits of the major airframe and engine companies.

RECENT years have seen the introduction by the Dow Corning Corporation of three silicone greases that have been applied with great success to the lubrication of ball bearings operating at abnormally high and low temperatures. These greases have good heat stability, low volatility and freezing points while over a wide range of temperature their consistency changes only slightly.

The purpose of this paper is to investigate the effects of coupling agents on the structure and properties of the nanocomposite films and clarify their mechanism. Polyimide (PI)/Al₂O₃ nanocomposite films were prepared using different coupling agents.

Poly(amic acid) (PAA) was firstly synthesised from appropriate pyromellitic diannanocomposite and oxydianiline in N‐dimethylacetamide. Calculated amount of nano‐Al₂O₃ particles modified by different coupling agents (KH550, KH560, KH570 and AE3012) were added to PAA solution by an ultrasonic‐mechanical method and PI/nano‐Al₂O₃ film was fabricated by heat curing. The microstructure, thermal stability, mechanical properties and electric breakdown strength of the films were characterised.

The addition of coupling agents could greatly improve the dispersion homogeneity of Al₂O₃ nano‐particles in PI matrix. Results of corresponding characterisations indicated that both the thermal stability and mechanical properties of PI/Al₂O₃ nanocomposite film with KH550 were greater/better than others, while AE3012 could improve the electric breakdown strength.

In the present discussion, the effects of different coupling agents, KH550, KH560, KH570 and AE3012, were investigated. Results of this research work would be beneficial to an in‐depth understanding on the relationship between microstructure and properties of PI composites, and further promote the development of the high‐performance PI insulating materials.

The four coupling agents, KH550, KH560, KH570 and AE3012, were firstly used to disperse the nano‐Al₂O₃ particles in PI matrix. The effects of coupling agents on microstructure and properties of composites were discussed by the authors in detail.

This article examines the susceptibility of cryptocurrencies to coronavirus disease 2019 (COVID-19) induced panic in comparison with major stock indices.

The author employs the Bayesian structural vector autoregression to examine the phenomenon in Bitcoin, Ethereum and Litecoin from 2nd January 2020 to 30th June 2021. A similar analysis is conducted for major stock indices, namely S&P 500, FTSE 100 and SSE Composite for comparison purposes.

The results suggest that cryptocurrencies returns suffered immensely in the early days of the COVID-19 outbreak following declarations of the disease as a global health emergency and eventually a pandemic in March 2020. However, the returns for all three cryptocurrencies recovered by April 2020 and remained resistant to further COVID-19 panic shocks. The results are dissimilar to those of S&P 500, FTSE 100 and SSE Composite values which were vulnerable to COVID-19 panic throughout the timeframe to June 2021. The results further reveal strong predictive power of Bitcoin on prices of other cryptocurrencies.

The article provides evidence to support the cryptocurrency as a safe haven during COVID-19 school of thought given their resistance to subsequent shocks during COVID-19. Thus, the author stresses the need for diversification of investment portfolios by including cryptocurrencies given their uniqueness and resistance to shocks during crises.

The author makes use of the novel corona virus panic index to examine the magnitude of shocks in prices of cryptocurrencies during COVID-19.

Silicone Agent. Protocoat is a colloidal suspended silicone compound based on silicone grease MS4, with a working temperature of −50°C. to +200°C. It is oxidation resistant, non‐volatile and resistant to tracking and the effects of corona discharge. Sprayed on, uses are as an auxiliary dielectric on ignition systems, as a sealing material for aerial connections, as a corrosion inhibitor for electric heating elements and as a lubricant to reduce abrasion inside cable conduits and keep rubber flexible. CT 1508

Silicone Insulating Compound A product originally developed to exclude moisture from aircraft ignition systems, which has excellent dielectric properties and a high order of water‐repellency, is silicone insulating compound MS 4. This is a smooth silicone grease with the consistency of petroleum jelly, which is said to retain its consistency at temperatures between ‐50°C and 200°C. It is chemically inert, highly resistant to oxidation, tracking and corona discharge. In addition, the manufacturers claim that it releases, preserves and lubricates rubber, plastics and many other surfaces.

This study aims to explore and verify the influence of the corona pandemic on the stock returns of the Palestinian companies listed on the Palestine Exchange during the period 2020–2021.

The research makes use of secondary financial data from 52 companies in the industrial, investment, services, banking and insurance sectors. Many financial ratios are calculated to assess stock returns: current ratio, cash ratio and average collection time as liquidity measures; debt-to-equity ratio as an indication of leverage or solvency; and net profit margin as an indicator of profitability. The research examines ratios between the (2020 and 2021) precorona outbreak using the Wilcoxon signed rank test and financial ratio analysis during the corona pandemic.

The findings show that liquidity in the investment, banking, insurance and industrial sectors has decreased significantly, whereas liquidity in the service sector has improved. The statistics reveal a considerable growth in debt in the service sector, while it stays unchanged in the other sectors. However, there is no discernible change in profitability during and after the corona outbreak.

The present research faced many limitations, such as the approach to gathering primary data, which depended heavily on disclosures, financial reports and secondary data, as well as only analyzing one context and one country.

The findings of this study can guide the Palestinian government and decision-makers to respond to the COVID-19 outbreak and must act quickly because strong short-term policies are more functional than long-term policy measures. In addition, the temporal discrepancy between their policy actions and financial regulations regarding the stage of the outbreak, integrating monetary treatment methods, strengthening their control over exchange rate fluctuations and extending the duration of financial participation measures that ensure stable exchange rates, such as attempting to restrict trade of the monetary system between countries was assessed to reduce the important monetary stimulation policy.

This study presents important facts and results for regulators and decision-makers regarding the investment, industry, banking, insurance and services sectors as sectors that are most affected by the corona pandemic as a sample for this study from the Palestinian companies listed in Palestine Stock Exchange due to the corona pandemic.

THE trend in high voltage connectors is towards miniaturisation, while providing the same degree of voltage handling and anti‐corona discharge performance as conventional designs. This usage of smaller dimensions is being achieved through careful design of parameters such as the tracking path lengths, scrupulous exclusion of air from the cable, connector internals and the mating surfaces.