Пленочные материалы на основе полиэтилена с наночастицами кремния и карбида кремния

Polyethylene films containing 0.1-1.5% of mass of n-SiС and n-Si nanoparticles have been produced by the extrusion method. Using the spectral analysis method, it was found that the obtained films absorb UV radiation in the range 200-400 nm, which is harmful to organic substance. The average particle sizes and the quality of their dispersion in the films were determined by X-ray diffraction analysis. Using differential scanning calorimetry and physical and mechanical tests, it was found that nanoparticles did not affect the formation of the internal structure of the matrix polyethylene. The degree of crystallinity, the melting point and crystallization remain unchanged. The properties of the film surface, studied by the tribological, triboelectric methods and the determination of the wetting angle, remain constant and do not differ from the properties of PE films with nanoparticle content 0.1-1%. At 1.5% n-SiC content, a change in the surface microrelief is diagnosed, leading to a slight increase in the friction coefficient of the films. The polyethylene films filled with n-SiС and n-Si obtained in this work are recommended for use as UV protective coatings for various purposes.В настоящей научно-исследовательской работе экструзионным способом были получены полиэтиленовые пленки, содержащие 0,1-1,5% (мас.) наночастицы n-SiС и n-Si, полученные плазмохимическим методом. С помощью спектрального метода анализа установлено, что полученные пленки поглощают УФ-излучение в диапазоне 200-400 нм, губительное для органической материи. Методом рентгеноструктурного анализа были определены средние размеры частиц и качество их диспергирования в пленках. Методами дифференциальной сканирующей калориметрии и физико-механических испытаний установлено, что наночастицы не влияют на формирование внутренней структуры полиэтилена (ПЭ) матрицы. Степень кристалличности, температуры плавления и кристаллизации остаются неизменными. Свойства поверхности пленок, исследуемые трибологическими, трибоэлектрическими методами и определением краевого угла смачивания, остаются постоянными и не отличаются от свойств ПЭ-пленок при содержании наночастиц от 0,1 до 1%. При 1,5% содержании n-SiС диагностируется изменение микрорельефа поверхности, приводящее к небольшому росту коэффициента трения пленок. Полученные в работе наполненные n-SiС и n-Si полиэтиленовые пленки рекомендуются для использования в качестве УФ защитных покрытий различного назначения

Germinação de sementes de Asteraceae nativas no Rio Grande do Sul, Brasil Germination of seeds of Asteraceae natives of Rio Grande do Sul, Brazil

Aquênios (sementes) recém coletados, de treze espécies nativas de Asteraceae comuns nos ambientes abertos da região sul do Brasil foram testados quanto à germinação em temperaturas alternadas ( 20/10; 25/15; 30/20; 35/25°C) e sob temperaturas constantes ( 20; 25 e 30°C) com ou sem luz. A temperatura ótima para germinação varia entre as espécies, sendo que as espécies Elephantopus mobilis; Eupatorium laevigatum; Mikania cordifolia; Senecio oxyphyllus; Trixis prastens germinam de forma semelhante em todas temperaturas testadas. Eclipta alba tem sua germinação promovida a 30°C. Tagetes minuta tem a germinação das sementes promovida a 20°C. Em Senecio heterotrichius; S. selloi; Stenachaenium campestre; Symphyopappus casarettoi e Vernonia nudiflora as sementes germinam igualmente a 20 ou 25°C.. A luz promoveu a germinação de todas espécies exceto para Stenachaenium campestre e Tagetes minuta, sendo esta última espécie fotoblástica negativa. Quanto ao tempo médio de germinação, as espécies podem ser divididas em ; rápidas- menos de 5 dias (Baccharis trimera; Eclipta alba; Elephantopus mollis; Stenachaenium campestre e Vernonia nudiflora); intermediárias: entre 5 e 10 dias ( Eupatorium laevigatum; Mikania cordifolia e Tagetes minuta) ; lentas: mais de 10 dias (Senecio heterotrichius; S.oxyphyllus; S.selloi; Symphyopappus casarettoi e Trixis praestans).Os resultados mostram que a germinação de sementes de Asteraceas variam com a temperatura e o regime de luz; podendo prover uma base inicial para interpretação de efeitos sazonais sobre a germinação e estabelecimento a campo. Em adição, comentários sobre o substrato ágar ou areia são feitos.<br>Achenes of thirteen native Asteraceae species common to the natural grassland or weeds of the southern region of Brazil were tested for germination over a range of alternating temperatures ( 20/10; 25/15; 30/20 and 35/25°C), and under constant temperatures ( 20; 25 and 30°C) with light or not .Only fresh collected achenes (herein = seeds) were used. The optimum temperature for germination differed among the species, with Elephantopus mobillis; Eupatorium laevigatum; Mikania cordifolia; Senecio oxyphyllus; Trixis praestans germinating the most over all temperatures tested. Eclipta alba seeds germination was promoted at 30°C. Colder treatments promoted germination in Tagetes minuta , and in Senecio heterotrichius; S.selloi; Stenachaenium campestre; Symphyopappus casarettoi and Vernonia nudiflora germination was equivalent at 20 or 25°C. Light promoted germination for all species except in Stenachaenium campestre and Tagetes minuta, the latter being a negative photoblastic species. According to the mean time for germination, the species could be ranked in: fast -less than 5 days- (Baccharis trimera; Eclipta alba; Elephantopus mollis; Stenachaenium campestre and Vernonia nudiflora); intermediate: between 5 and 10 days- (Eupatorium laevigatum; Mikania cordifolia and Tagetes minuta) ; slow: more than 10 days-(Senecio heterotrichius; S.oxyphyllus; S.selloi; Symphyopappus casarettoi; Trixis praestans). The results show that germination of seeds of a range of Asteraceae species varies with temperature and light regime; they provide an initial basis on which to test and interpret the effects of seasonal factors on germination and field establishment. In addition, comments on the agar and sand substrates were made