Natural Dispersal Research Articles

Independent fledglings of Forty-spotted Pardalotes Pardalotus quadragintus stay in their natal territory: Implications for translocations

The Endangered Forty-spotted Pardalote Pardalotus quadragintus is restricted to a small proportion of its former range, with the vast majority of birds occurring on two small Tasmanian islands. As such, the species is threatened by landscape-scale fires that could severely impact these populations. This has led to interest in reintroducing the species to parts of its former range that are now beyond its natural dispersal capabilities. One potential way of doing this is to transfer fledglings from their natal territories to unoccupied habitat. However, it is not known when fledglings are able to survive without their parents. This study found that fledglings first appeared independent of their parents for food 11 days after leaving the nest, and remained within the natal territory for several weeks thereafter. This finding could help guide options for future translocation planning.

Relativistic effects on the Schrödinger-Newton equation

The Schr\"odinger-Newton model describes self-gravitating quantum particles, and it is often cited to explain the gravitational collapse of the wave function and the localization of macroscopic objects. However, this model is completely nonrelativistic. Thus, in order to study whether the relativistic effects may spoil the properties of this system, we derive a modification of the Schr\"odinger-Newton equation by considering certain relativistic corrections up to the first post-Newtonian order. The construction of the model begins by considering the Hamiltonian of a relativistic particle propagating on a curved background. For simplicity, the background metric is assumed to be spherically symmetric and it is then expanded up to the first post-Newtonian order. After performing the canonical quantization of the system, and following the usual interpretation, the square of the module of the wave function defines a mass distribution, which in turn is the source of the Poisson equation for the gravitational potential. As in the nonrelativistic case, this construction couples the Poisson and the Schr\"odinger equations and leads to a complicated nonlinear system. Hence, the dynamics of an initial Gaussian wave packet is then numerically analyzed. We observe that the natural dispersion of the wave function is slower than in the nonrelativistic case. Furthermore, for those cases that reach a final localized stationary state, the peak of the wave function happens to be located at a smaller radius. Therefore, the relativistic corrections effectively contribute to increase the self-gravitation of the particle and strengthen the validity of this model as an explanation for the gravitational localization of the wave function.

Spatial genetic patterns in African wild dogs reveal signs of effective dispersal across southern Africa

Across much of Africa, decades of civil war, land reforms, and persecution by humans have decimated wildlife populations. African wild dogs (Lycaon pictus) have declined dramatically during the past decades, but have shown recent natural recolonisation of some areas. In Angola, they were rediscovered after almost five decades when no surveys were being conducted, and they have recolonised areas in southern Zimbabwe and northern South Africa. Wild dogs were also reintroduced to Mozambique, where only few individuals remained. Against this backdrop, understanding genetic structure and effective dispersal between fragmented populations is essential to ensure the best conservation approaches for the long-term survival of the species. Our study investigated population genetic diversity, differentiation and gene flow of wild dogs across southern Africa, to include areas where they have recently been rediscovered, reestablished or reintroduced. Our results point to four weakly differentiated genetic clusters, representing the lowveld of Zimbabwe/Limpopo, Kruger NP, Angola/KAZA-TFCA, and the managed metapopulation, counterbalanced by moderate levels of effective dispersal on a southern African scale. Our results suggest that if the human footprint and impact can be significantly minimized, natural dispersal of wild dogs could lead to the demographic recovery of the species in southern Africa.

A nationwide pest risk analysis in the context of the ongoing Japanese beetle invasion in Continental Europe: The case of metropolitan France.

The Japanese beetle, Popillia japonica, is native to Japan and became established in North America in the early twentieth century. The beetle was detected in Europe, first in Italy in 2014 and then in Switzerland in 2017. Metropolitan France is at the forefront of the Japanese beetle threat, due to its geographical proximity to the European populations established in the Piedmont, Lombardy and Ticino regions. An express pest risk analysis for metropolitan France was therefore conducted. The most likely pathways for entry include (i) natural dispersion, (ii) trades of plant products with adherent soil and (iii) hitchhiking behaviour, leading to a high probability of entry. The spread rate of P. japonica was also evaluated as high, resulting from natural spread as well as human activities. Given the absence of significant limiting factors, the potential impacts of P. japonica in France will likely be as important as in its current geographic distribution. Although several sources of uncertainty were highlighted throughout the evaluation, none of them has significant impact on the conclusions of the present express pest risk analysis. Measures to prevent entry, establishment and spread of P. japonica are recommended and include surveillance with pheromone traps and control via integrated pest management strategies. However, most efforts should be concentrated on eradication measures while P. japonica is still in the early stages of invasion.

Landscapes drive the dispersal of Monochamus alternatus, vector of the pinewood nematode, revealed by whole-genome resequencing

Pine wilt disease (PWD), Bursaphelenchus xylophilus, is an extremely threatening invasion forest disease throughout the world, especially in Asia. B. xylophilus is spread in Asia by vector beetles of Monochamus alternatus, which has long no effective control method. Understanding of landscape effects on the dispersal and outbreaks of forest pests is crucial to establishing effective ecological control strategies. Here, we analyzed the samples of M. alternatus collected in a fine-scale in order to estimate the effects of landscape types on the genetic structure and dispersal of M. alternatus. The landscapes included the geographical scales, forest types and land uses. The individuals of M. alternatus were genotyped by using whole-genome resequencing. Population genetic structures were clearly differentiated at the range of 250 kms, suggesting the intermediate scale is an effective barrier against natural dispersal of M. alternatus. We used the least-cost distances, least-cost transect analysis, and distance-based redundancy analysis to estimate the effects of forest types and land uses within the fine scales. The results showed that the gene flow and genetic diversity were positively correlated with host and mixed forests, whereas negatively with non-host forests. Among land-use landscapes, the roads had the positive effect on gene flow and genetic diversity but farmland and urban uses had negative effects. This highlights that human-mediated transport via roads was likely to be the main factor leading to the long-distance invasion of M. alternatus, whereas non-host landscapes could suppress the spread of this species. These findings may be useful to control the PWD dispersed by M. alternatus.

Climate warming triggers the emergence of native viruses in Iberian amphibians.

The number of epizootics in amphibian populations caused by viruses of the genus Ranavirus is increasing worldwide. Yet, causes for pathogen emergence are poorly understood. Here, we confirmed that the Common midwife toad virus (CMTV) and Frog virus 3 (FV3) are responsible for mass mortalities in Iberia since the late 1980s. Our results illustrate the Iberian Peninsula as a diversity hotspot for the highly virulent CMTV. Although this pattern of diversity in Europe is consistent with spread by natural dispersal, the exact origin of the emergence of CMTV remains uncertain. Nevertheless, our data allow hypothesizing that the Iberian Peninsula might harbor the ancestral population of CMTVs that could have spread into the rest of Europe. In addition, we found that climate warming could be triggering the CMTV outbreaks, supporting its endemic status in the Iberian Peninsula.

Ancient islands or ancient mariners? The cryptic history and voyages of the South Pacific barnacle Rehderella Zevina & Kurshakova, 1973 (Cirripedia: Thoracica: Chthamalidae)

Abstract We report the first verified DNA barcode data for the tropical chthamalid barnacle Rehderella belyaevi (Zevina & Kurshakova, 1973) and place it in phylogenetic and biogeographic context among other lineages of Pacific barnacles. Hitherto found on a few remote but widely separated islands across the South Pacific, R. belyaevi is the sole described species of its genus. Phylogenetic analyses indicate that Nesochthamalus intertextus (Darwin, 1854) is its sister taxon and that this taxon pair is nested in a cluster of South Pacific chthamalid taxa. We found that the Pitcairn Is. population includes an admixture of diversity from French Polynesia and Rapa Nui (Easter I.), with those populations being quite divergent. In light of the long history of ocean-going vessel movements in this region, beginning with Polynesian voyagers and the propensity of chthamalid barnacles to occur in biofouling communities, the sequence diversity on Pitcairn is suggestive of ship-borne influence, the more so since the tremendous distances between these islands may preclude natural larval dispersal among them. The true distributional range of Rehderella in the South Pacific is unknown, as shown by our report herein of an undescribed lineage of this genus in French Polynesia based on specimens collected 20 years ago. Furthermore, our discovery that this species occurs on floating plastic debris, a vast amount of which is now present throughout the South Pacific, suggests that the ocean voyages of Rehderella may continue.

Ecological status of macrobenthic communities in the Saudi waters of the western Arabian Gulf

In view of the unique oceanographic conditions combined with human pressure, we assessed the ecological status of macrobenthos from the entire Saudi waters (including open waters and inner bays) of the Gulf in 2013. A total of 328 macrobenthic species (228 polychaete species, 47 crustacean species, 46 mollusc species, and seven species belonging to other taxa) was recorded from the study area. Species richness, species diversity, and density had an overall average ±SE of 34 ± 2.0, 4.02 ± 0.1 and 1,373 ± 160 ind. m−2, respectively. As per the results of AZTI’s Marine Biotic Index (AMBI), in open waters, 10% of stations belonged to undisturbed and the remaining 90% belonged to slightly disturbed categories, while in sheltered inner bays, 95% of the stations belonged to slightly disturbed and the remaining 5% belonged to moderately disturbed categories. According to Multivariate AMBI (M-AMBI), 4% of the stations showed high status, 74% good status, 23% moderate status and 1% poor status in open waters. In inner bays, 2% of the stations showed high status, 73% good status, 14% moderate status and 4% poor status. The open waters, where extensive industrial activities take place, are not under major stress, which might be due to the implementation of appropriate mitigation measures during the construction and operation of the offshore facilities and the natural dispersal of potential pollutants. The stressed conditions on benthos in inner bays might be due to coastal discharges besides extreme oceanographic conditions, including the poor water flushing rates, which increase the exposure to pollutants.

UV-Assisted Room-Temperature Fabrication of Lignin-Based Nanosilver Complexes for Photothermal-Mediated Sterilization.

Green and controllable preparation of silver nanoparticles (AgNPs) remains a great challenge. In this work, ethanol-extracted lignin-based nanosilver composites (AgNPs@EL) were synthesized at room temperature with the assistance of ultraviolet (UV) radiation. The ethanol-extracted lignin (EL) could serve as natural dispersion carriers and reducing agents for AgNPs. The reducing ability of EL could be further improved under UV irradiation, which enables the rapid synthesis of AgNPs at room temperature. More importantly, due to the good photothermal conversion capacity of EL, AgNPs@EL exhibits remarkably enhanced photothermal performance and excellent photothermal antibacterial ability, which could cause 7.2 and 5.3 log10 CFU/mL reduction against Escherichia coli and Staphylococcus aureus, respectively, under near-infrared (NIR) irradiation (808 nm, 1.8 W/cm2) for 5 min. Furthermore, the composite film obtained by impregnating bacterial cellulose onto AgNPs@EL solution also shows significantly improved mechanical properties and photothermal antimicrobial activity. Therefore, this work may provide insights into the design of lignin-based photothermal-mediated antimicrobial materials.

Suitability of Natura 2000 sites for threatened freshwater species under projected climate change

Abstract As part of the world's largest coordinated network of protected areas, Natura 2000, European Union member states designate special areas of conservation (SACs) to maintain or achieve favourable conservation status for imperilled aquatic species listed under Annex II of the Habitats Directive. Long‐term suitability of SAC habitats is potentially challenged by continuing climate change. To examine this emerging threat to aquatic species conservation, the habitat suitability of designated SACs (n = 8,221) for 24 Central European freshwater species (18 teleosts, two lampreys, two crayfish and two bivalves) was assessed under current and projected end‐of‐century climate using environmental niche models calibrated on species occurrences reported under the Habitats Directive (n = 33,995). Potential future conditions included three climate‐change scenarios representing a gradient from effective climate protection measures to a worst‐case warming scenario. Habitat suitability of SACs was consistently calculated as high under present climate but projected to decline severely for two‐thirds of the species under future climate conditions, with the magnitude of decline generally paralleling that of projected climate change. Under high emission scenarios, one third to more than half of the species were predicted to face unsuitable conditions in ≥75% of SACs. Predicted change in habitat suitability varied across biogeographical regions, with Alpine SACs often undergoing lower or no decline in predicted suitability. Given the discrepancy between the location of currently designated SACs and predicted areas of suitable habitat under projected end‐of‐century climate, climate change can be expected to undermine the long‐term effectiveness of currently protected areas. Fostering climate resilience of freshwater habitats within SACs, restoring stream connectivity among SACs, assisted migration to newly suitable SACs where natural dispersal is not possible, as well as designation of new protected areas within climate refugia represent key actions to overcome this potential future conservation gap.

Near‐shore island lizard fauna shaped by a combination of human‐mediated and natural dispersal

AbstractAimIsland biotas provide opportunities to study colonization and adaptation to novel environments. Islands, especially near‐shore islands, may have a long record of human habitation such that some lineages result from human‐assisted introductions. Here, we combine phylogenetic analyses with fossil data and historical specimen records to reconstruct colonization histories, characterize among‐island divergence and assess the role of humans in shaping the evolutionary history of lizards inhabiting a near‐shore island archipelago.LocationChannel Islands and adjacent mainland of California, United States.TaxaWestern fence lizard (Sceloporus occidentalis), southern alligator lizard (Elgaria multicarinata), common side‐blotched lizard (Uta stansburiana).MethodsWe sequenced mitochondrial DNA (ND1, cyt‐b) from each of three lizard species, covering their entire island distributions plus the adjacent mainland. For each, we estimated diversity within and among each island, obtained maximum likelihood bootstrapped phylogenies, constructed haplotype networks and tested for population expansion. We used museum specimen records and microfossil evidence to infer colonization scenarios.ResultsSceloporus occidentalis is characterized by a single island‐colonization event, and exhibits the deepest divergences from mainland relatives and the highest among‐island divergence. Elgaria multicarinata and Uta stansburiana each have at least three distinct colonization events, with fossil and historical data indicating that some of these occurred after humans arrived to the islands.Main ConclusionsThe evolution of Channel Island lineages for two lizard taxa has been mediated by ancient and contemporary anthropogenic activity, while the evolution of the third is shaped by natural dispersal and vicariance caused by sea‐level rise. Genetic divergence corroborates the treatment of S. occidentalis as an endemic island species, Sceloporus becki. The unique histories of these three taxa are synthesized with other Channel Island lineages highlighting that taxa inhabiting islands with long histories of human activity should be carefully studied to assess the role of people in facilitating colonization and subsequent gene flow.

The effects of dispersal, herbivory, and competition on plant community assembly.

Dispersal is a key process in community assembly but is often considered separately from downstream assembly processes (e.g., competition, herbivory). However, dispersal varies by species and can interact with other assembly processes through establishment as species enter communities. Here, we sought to distinguish the role of dispersal in community assembly and its interaction with two biotic assembly processes: competition and herbivory. We used a tallgrass prairie restoration experiment that manipulated the competitive and herbivore environments while allowing for natural dispersal and establishment from a diverse regional species pool into areas of low diversity. Dispersal, competition, and herbivory all influenced local communities. By tracking the spread of four target species across the plots, we found interspecific and intraspecific differences in establishment patterns, with herbivores influencing the number of individuals present and the distances species moved. At the community level, only dispersal and competition significantly influenced alpha diversity, but all three processes additively influenced community composition. There was also evidence of herbivore-competition and herbivore-colonization trade-offs in our experiment. Some species that could tolerate herbivory were less likely to establish in competitive environments, while others that could tolerate herbivory were more likely to disperse greater distances. More work is needed to understand the contexts under which dispersal variation affects community assembly and its synergy with other processes.

The Jorō spider (Trichonephila clavata) in the southeastern U.S.: an opportunity for research and a call for reasonable journalism

Trichonephila clavata, also known as the Jorō spider, was first discovered in Georgia, USA in 2014. Its arrival from Asia and subsequent range expansion across the southeastern U.S. has received much media coverage, spanning from factual to sensational. Here, we describe T. clavata's invasion potential and known invasive range, and review its biology, dispersal abilities, potential impacts, and management strategies. As of October 2022, T. clavata's range spans at least 120,000 km2, occurring across Georgia, South Carolina, North Carolina, and Tennessee, with additional reports in Alabama, Maryland, Oklahoma, and West Virginia. Its pattern of spread suggests it is primarily driven by natural dispersal mechanisms, such as ballooning, though human-mediated transport cannot be discounted. Like other large-bodied orb-weavers, T. clavata captures and feeds on flying insects and potentially other small animals, and we suggest thirteen co-occurring spider species that should be monitored for competition with T. clavata for resources and web-building sites. Since T. clavata is spreading across both natural and urban habitats, management options are limited. Overall, very little is known about this species in its new North American range, especially its impacts within this novel ecosystem. Thus, we advise journalists and experts alike against exaggerating its potential environmental impact or uncritical acceptance of the spider as ecologically harmless. Instead, T. clavata's rapid spread should be carefully monitored, and we should take a cautious, evidence-based approach when determining next steps.

Helicoverpa genus on the edge of the continental U.S.: Flight phenology, analysis of hybrid presence, and insecticide performance in high-input field crops in Puerto Rico.

The genus Helicoverpa includes several agricultural pests globally. Helicoverpa armigera was reported in several countries in South America in 2013, and in Puerto Rico, in 2014. This territory is considered an agricultural hub, with a high-input system of seed production in the southern region of the island, and also at the edge of the continental U.S. Possible natural dispersion of populations of H. armigera from the Caribbean or other Central American regions poses a continuing risk to the U.S. This study was performed during the post-detection scenario of H. armigera in Puerto Rico, from 2018 to 2021. A year-round pheromone trapping program of adult males indicated an increase in the population from October to March and differences in the occurrence of Helicoverpa spp. between the municipalities Juan Diaz and Salinas. The proportion of H. armigera/H. zea and detection of congeneric hybrids between these species were assessed based on genital morphology and DNA analysis. Interestingly, neither H. armigera nor expected hybrids were detected in the present study. The susceptibility of H. zea populations to the insecticides Spinetoram, Emamectin benzoate, Chlorantraniliprole, and Esfenvalerate was assessed, and an overall significant effect of insecticide susceptibility was detected. Chlorantraniliprole and Emamectin benzoate had the highest efficacy. These results contribute to the Integrated Pest Management and Insect resistance management programs to Helicoverpa spp. in Puerto Rico. In addition, provide validated information to be considered in mitigation plans, in the scenario of an invasion of H. armigera in the continental U.S.

Decision surface optimization in mapping exotic mangrove species (Sonneratia apetala) across latitudinal coastal areas of China

The exotic Sonneratia apetala is widely planted in mangrove afforestation in China due to its high adaptability and fast growth rates. This species has triggered intense debate on its ecological invasion risk during the past decades because of its natural reproduction, dispersal, and spread. However, national plans for the management and control of this exotic species are unclear, partly due to the lack of an accurate distribution map of the species for broad latitudinal areas. Mangrove species with subtle spectral differences and varied growth phases require plenty of samples to describe their spectrum; however, the scarcity of samples resulting from the low accessibility of their habitats hinders the mapping of the species across the national coastal zone. To overcome this problem, we derived S. apetala samples from existing discrete localized studies and then iteratively optimized the trained binary model by incorporating new negative samples until a threshold converged. Negative samples were more easily acquired in areas where the absence of S. apetala had been confirmed. This approach avoids the prerequisite that S. apetala can be distinguished by visual inspections, which is commonly used in routine classification procedures or active learning classifiers. The approach was applied to derive classification results with the help of a Random Forest classifier using both Sentinel-1 and −2 imagery hosted on Google Earth Engine, considering that S. apetala differs from native mangrove species in terms of the large crown, drooping branches, and biochemical properties. The generated S. apetala map was evaluated using three prepared datasets and achieved overall accuracies of 98.1 % and 96.4 % using the test dataset and independent evaluation dataset, respectively, as well as an accuracy of 91.7 % using 145 field samples provided by mangrove specialists. The total area of exotic S. apetala in China reached 2,968 ha in 2020, accounting for 11.0 % of the total mangrove area in China. This study is the first attempt to delineate the detailed national-scale distribution of S. apetala in coastal China. The information provided in this study can support the management and control of S. apetala. The developed approach can be generalized to other vegetation species in broad latitudinal areas, and can be further improved by probing the internal details of the trained classifier.

General Guided-Wave Impedance-Matching Networks with Waveguide-Metamaterial Elements

A plasmonic based nanocircuit transplants the lumped property of classical electronic circuits to optical frequencies, providing a circuit paradigm for optics and photonics. To broaden the material and frequency selections, the concept of a waveguide metamaterial is applied to design lumped elements by utilizing the waveguide's structural dispersion to emulate the natural material's dispersion. Here, as an important application of the physics of waveguide metamaterials, a general type of impedance-matching network directly integrated with a waveguide is investigated for various matching occasions of guided waves, outperforming the classical ones using waveguide membranes. Three representative matching examples are analyzed to validate the feasibility, namely, transmission discontinuities, active power amplifiers, and antennas. The numerical and experimental results confirm the impedance-matching applications of the waveguide metamaterial and suggest the potential merits of low loss and low crosstalk for the proposed waveguide-integrated matching networks in terahertz integrated-circuit designs.

The Southern Flying Squirrel (Glaucomys volans) in Lincoln, Nebraska

The southern flying squirrel (Glaucomys volans) is considered a species of greatest conservation need in Nebraska and listed as threatened in the state. Historically, the geographic range of the southern flying squirrel in Nebraska has been restricted to five eastern counties from a northern suburb of Omaha, Douglas Co., southward in the four counties of Sarpy, Otoe, Nemaha, and Richardson, all bordering the Missouri River on the east. In late November of 2018, a resident of Lincoln, Lancaster Co., Nebraska, contacted the Nebraska Game and Parks Commission about an animal found dead in his yard. This animal proved to be a southern flying squirrel, which was 50 to 70 miles [80 to112 km] west of the known geographic range of the species. Two additional individuals were subsequently observed at the original residence as were individuals in at least a total of 10 neighborhoods throughout the city of Lincoln. Clearly, a population of the southern flying squirrels is established and reproducing in Lincoln, but their origin is unknown. The source of this city-dwelling population may be from released/escaped pets, a natural dispersal from the Missouri River via the Platte River and Salt Creek, or inadvertent translocation when moving timber or fire wood.

Developing Electrospun Ethylcellulose Nanofibrous Webs: An Alternative Approach for Structuring Castor Oil.

The development of environment-friendly natural polymer gel-like dispersions in oil media, with functional properties, in terms of formulation design and synthesis protocol, is still a cutting-edge research area for many applications. The aim of this work was to study the manufacture of electrospun ethylcellulose (EC) nanofibrous webs and to examine their usage to thicken vegetable oils as an alternative approach. The role of concentration, molecular weight (Mw), and binary solvent systems on the electrospinnability of EC and subsequently on the rheological properties of EC nanofiber dispersions in castor oil was investigated. It was observed that, for each Mw, defect-free nanofibers were produced above a critical concentration, corresponding to about 2.5 the entanglement concentration (Ce). The average fiber diameter increased with both Mw and EC concentrations. Dielectric constant and dipole moment of binary solvent systems influenced the morphology of the EC nanofiber web. The morphology of the micro- and nanoarchitectures generated played a key role in the physical stabilization and rheological behavior of electrospun EC dispersions. The storage modulus (G') of EC dispersions was correlated with both the spinning solution concentration and average fiber diameter. Furthermore, electrospun EC nanofiber dispersions were compared with EC oleogels obtained by traditional thermogelation from thermorheological and tribological points of view. Overall, this work proposes an efficient and innovative approach to produce bio-based oleogel-like dispersions with great potential in different sectors such as pharmaceuticals, food, or lubricants.

Genetic Diversity and Relatedness of Group-Living Small Mammals on the Mongolian Plateau

Genetic diversity plays an important role in the evolution and adaptation of organisms. Losses of genetic diversity make organisms more vulnerable to climate changes and diseases, reducing the viability of small populations. In addition to natural selection, genetic drift, dispersal, inbreeding, and population bottleneck, the social systems of animals may also affect the genetic diversity of populations. We aimed to test the hypothesis that the delayed dispersal of group-living small mammals would reduce genetic diversity through attenuated gene flow but enhance genetic relatedness. We used microsatellite analysis to estimate genetic diversity and the Queller and Goodnight relatedness coefficients of Daurian pikas (Ochotona dauurica) and Mongolian gerbils (Meriones unguiculatus), two socially monogamous small mammals living in social groups in Inner Mongolia, China. The average genetic relatedness of social groups was inversely related to the average genetic diversity of social groups in Daurian pikas but not in Mongolian gerbils, partially supporting our hypothesis. Dispersal following frequent local extinctions resulted in the recolonization of burrow systems by individuals with different genetic makeups, increasing genetic diversity and reducing the genetic relatedness of the social groups of Daurian pikas. On the other hand, delayed short-distance dispersal was sufficient to maintain the high genetic diversity and high genetic relatedness of gerbil social groups independently.

Study of the fillers influence on the organosilicon polymers resistance to high temperatures

Organosilicon varnishes, such as polymethylphenylsiloxane and polyaluminomethylphenylsiloxane, filled with modified clay minerals are the object of research The most vulnerable place of the organosilicon coating is insufficient mechanical properties (hardness, impact strength, etc.) and low adhesive strength of the film to the surface, especially when operating at elevated temperatures. Various oxides, ceramic compounds, natural and synthetic silicate materials are introduced into organosilicon compositions to improve the specified properties. But only individual units can comprehensively improve both the mechanical and heat-resistant properties of organosilicon compounds although the range of such materials is quite wide. The clay minerals palygorskite, which is classified as an intermediate type between strip and layered silicates, and montmorillonite from the subclass of layered silicates, which have a natural high dispersion, were used as fillers during the study. The choice of palygorskite and montmorillonite is explained by the sufficient study of their behavior in organic environments by a number of scientists, availability and economic advantages for introduction into production. Existing clay minerals, which are traditionally used to solve the problem of improving the physical and mechanical properties of organosilicon coatings, are not sufficiently active due to the hydrophilic properties of the particles surface. Based on this, a modifier that has proven itself well in this field was used for the study. A number of compositions of heat-resistant organosilicon varnishes with modified fillers based on the above-mentioned clay minerals were obtained. It was established that the introduction of modified forms of natural aluminosilicates contributes to the increase of temperature resistance in filled coatings, compared to coatings made of pure polymer. At the same time, the best effect is achieved when using montmorillonite. This is related with the fact that the proposed compositions of polymethylphenylsiloxane varnish and montmorillonite have a number of features, in particular, the highest comprehensive result of simultaneous improvement of the physical, mechanical and thermal properties of the specified coatings. It is possible to obtain compositions with stable physico-mechanical properties, as they withstood heat treatment at 400 °C for 100 hours without visible changes in integrity, due to the introduction of the optimal amount of modified montmorillonite into organosilicon varnishes KO-08K and KO-921. Compared to similar heat-resistant polymethylphenylsiloxane varnishes, longer service life at elevated temperatures is ensured.