RESUMO
Biaxially oriented polyamide 6 (BOPA6) films were prepared by extrusion casting and biaxial stretching with polyamide 6. The effects of different biaxially oriented on the macroscopic properties of BOPA6 were investigated by characterizing the rheological, crystallization, optical, barrier and mechanical properties. The results show that the increase of stretching temperature leads to the diffusion and regular stacking rate of BOPA6 chain segments towards crystal nuclei increases, the relative crystallinity increases, reaching 27.87% at 180 °C, and the mechanical strength and optical performance decrease. Heat-induced crystallization promotes the transformation of ß-crystals to α-crystals in BOPA6, resulting in a more perfect crystalline structure and enhancing oxygen barrier properties. BOPA6 chains are oriented, and strain-induced crystallization (SIC) occurs during the biaxial stretching. Further increasing the stretch ratio, the relative crystallinity increased to 30.34%. The machine direction (MD) and transverse direction (TD) tensile strength of BOPA6 (B-33) are nearly two times higher than the unstretched film, reaching 134.33 MPa and 155.28 MPa, respectively. In addition, the permeation decreases to 57.61 cc·mil/(m2 day), and the oxygen barrier performance has improved by nearly 30% compared to the sample B-22. BOPA6 has a high storage modulus at a high stretching rate (300%/s). Rapid chain relaxation would promote the molecular chain disorientation, destroy the entangled network of the molecular chain, and lead to a decrease in tensile strength, reducing to about 110 MPa.
RESUMO
Recent cave biodiversity surveys carried out in Du'an County and its adjacent areas of northwestern Guangxi, China, have revealed some exciting scientific findings. In a very limited area seven new species of the cavernicolous trechine genus Dongodytes Deuve, 1993 were found and are described: Dongodytes(s. str.)elongatussp. n., Dongodytes(s. str.)troglodytessp. n., Dongodytes(s. str.)lanisp. n., Dongodytes (Dongodytodes) brevipenissp. n., Dongodytes (Dongodytodes) jinzhuensissp. n., Dongodytes (Dongodytodes) inexpectatussp. n. and Dongodytes (Dongodytodes) yaophilussp. n. Diagnoses and notes on the genus, subgenera, and two known species in Du'an Karst, Dongodytes(s. str.)baxian Tian, 2011 and Dongodytes (Dongodytodes) deharvengi Tian, 2011, are also given. A key to subgenera and all species of Dongodytes is provided. To date, Dongodytes becomes one of the richest in species genera of subterranean carabid trechines in China with 12 species which are arranged into two subgenera. Dongodytes (s. str.) Deuve is composed of seven species, four of which from Du'an County, each of other three from Bama, Fengshan and Tian'e Counties, respectively. All species of the subgenus Dongodytodes Tian, 2011 are recorded from Du'an Karst. By having 10 species (nine Dongodytes and one Libotrechus Uéno, 1998), Du'an Karst holds the richest specific diversity of cavernicolous Trechinae in China. Dongodytes species are distributed in a very limited area of the river Hongshui He drainages in northwestern Guangxi, and the river acts as a natural barrier of Dongodytes dispersal at only a specific level. However, all members of Dongodytodes are recorded from the eastern or northern bank of Hongshui He.
