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In recent years, coated fabrics have become the major material used in membrane structures. Due to the special structure of base layer and mechanical properties, coated biaxial warp-knitted fabrics are increasingly applied in pneumatic structures. In this article, the mechanical properties of coated biaxial warp-knitted fabrics are investigated comprehensively. First, off-axial tensile tests are carried out in seven in-plane directions: 0°, 15°, 30°, 45°, 60°, 75°, and 90°. Based on the stress–strain relationship, tensile strengths are obtained and failure modes are studied. The adaptability of Tsai–Hill criterion is analyzed. Then, the uniaxial tensile creep test is performed under 24-h sustained load and the creep elongation is calculated. Besides, tearing strengths in warp and weft directions are obtained by tearing tests. Finally, the biaxial tensile tests under five different load ratios of 1:1, 2:1, 1:2, 1:0, and 0:1 are carried out, and the elastic constants and Poisson's ratio are calculated using the least squares method based on linear orthotropic assumption. Moreover, biaxial specimens under four load ratios of 3:1, 1:3, 5:1, and 1:5 are further tensile tested to verify the adaptability of linear orthotropic model. These experimental data offer a deeper and comprehensive understanding of mechanical properties of coated biaxial warp-knitted fabrics and could be conveniently adopted in structural design. [ABSTRACT FROM AUTHOR]

Organic-modified montmorillonite (OMMT), organic-modified layered double hydroxide (SDS-LDH) and graphene (GNS) were three typical layered inorganic compounds. The polystyrene (PS) nanocomposites were prepared using in situ polymerization method. X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, and microscale combustion calorimeter were used to investigate the morphology and microstructure, thermal stability, and combustion performance of the PS nanocomposites. It was evident that the addition of the typical layered inorganic compounds could improve thermal stability and flame retardancy of PS. The results revealed that organic-modified layered double hydroxide and graphene were dispersed in PS matrix with mainly exfoliated structure, whereas OMMT distribution with intercalated and few exfoliated structure. The PS/OMMT nanocomposites exhibited superior flame retardance over PS/SDS-LDH and PS/GNS. Compared to pure PS, a 25% decrease in the peak heat release rate value was obtained for PS nanocomposites containing 3.0 wt% OMMT. The thermogravimetric analysis results demonstrated that the addition of OMMT led to the improvements in the thermal stability and char residues of the PS nanocomposites, especially the T−50% and Tmax of the PS/5.0 wt% OMMT nanocomposites had improved by 38°C and 63°C, respectively, compared to those of pure PS. The improvement of thermal stability and fire resistance properties was primarily attributed to the physical barrier effect of layered inorganic nanosheets and the catalytic carbonization behavior of layered double hydroxide. POLYM. COMPOS., 38:E320-E330, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

ABSTRACT The outdoor natural weathering of polyamide 6 (PA6) was performed at six national standard natural exposure stations (at Qionghai, Guangzhou, Qingdao, Lhasa, Hailaer, and Ruoqiang), which represented the six typical climates over China. The outdoor aging behavior was studied. We found that under high temperature and humidity in the areas of Guangzhou, Qionghai, and Qingdao, the concentration of the end carboxyl group of PA6 increased significantly and the molecular weight decreased because of serious hydrolytic degradation. This resulted in a deterioration of the mechanical properties, high yellowing degree, and serious damage of the sample surface. While in the areas of Lhasa and Ruoqiang, with the relatively low temperature, humidity, and oxygen content in the atmosphere, the aging degree and corrosion index were low, and this resulted in the slow change of performances. Humidity, temperature, and rainfall may be the main environmental factors affecting the degradation of PA6. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44231. [ABSTRACT FROM AUTHOR]

The article focuses on the study on crystallization behavior, preparation, and melting characteristics of β-Nucleated isotactic polypropylene (iPP) blends with polyamide 6 (PA6). It states that adding a nucleating agent to the blends of iPP and PA6 phase may result to high content of β-iPP. It also shows that compatibilizer improved the distribution of PA6 in the iPP phase which reduces the crystalline ability and PA6's α-nucleating ability.

Abstract: In this paper, nano-CaCO3 supported β-nucleating agent for polypropylene (PP) was prepared by supporting pimelic acid on nano-CaCO3 with two methods. The thermal properties of pimelic acid and nano-CaCO3 supported β-nucleating agent were investigated by differential scanning calorimetry and thermogravimetry coupled with Fourier transform infrared spectrometry. The results indicated that the formation of β-nucleating agent supported on nano-CaCO3 was attributed to the chemical reaction between nano-CaCO3 and pimelic acid. The β-nucleating agent was added to PP to examine its β-nucleating ability for PP, the polymorphism of the PP was characterized by wide-angle X-ray diffractometer. The results of investigation showed that the nano-CaCO3 supported β-nucleating agent exhibited higher nucleation ability and lower price compared to calcium pimelate β-nucleating agent. [Copyright &y& Elsevier]

Due to its high strength, toughness, corrosion resistance and wear resistance, long chain polyamide (LCPA) has attracted broad interest. Nevertheless, its wide application in industrial fields is still being restricted because the starting material acquisition step involving diacid and diamine remains a major obstacle. Herein, we circumvent this obstacle by developing a novel polymer with similar properties by a green and efficient copolymerization process of carbon dioxide (CO 2 )-based dicarbamate with diamide diol under vacuum conditions, named poly(urethane- co -amide) (PUA). The semi-crystalline PUAs with high number-weight-average molecular weights ( M n , up to 41.3 kDa) were readily obtained, and these new polymers show high thermal stability (above 300 °C). Thanks to its unique chain structure, the amide, urethane and urea groups can endow the polymer with a high density cross-linking network via hydrogen bonds and high crystallinity that can result in high strength, up to 54.0 MPa. The dynamic thermomechanical analysis (DMA) results suggest that the phase separation exists within the new polymers, endowing the PUAs with a toughness higher than that of long chain polyamides. Consequently, this work not only develops a useful new polymer like commercial polyamides with high performance as a long chain polyamide candidate, but also provides a new way of utilizating CO 2 ., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)