介孔分子硅剂改善茶浓缩膜结构特性应用研究

为有效提高功能性茶浓缩反渗透膜的回收效率和抗污性能,探究了3种介孔分子硅材料(MCM-41、SBA-15和MCFs)对浓缩膜面聚酰胺层聚合形成过程的结构影响。结果表明,添加质量分数0.02%经磺化预处理的MCM-41于间苯二胺水相可接枝酰氯基团,形成的聚酰胺结构层峰谷粗糙跨度仅为220 nm且交联紧致,膜抗拉伸强度增加37.8%;SBA-15和MCFs相膜面峰谷跨度达500~780 nm,横向褶皱和团聚,结构存在孔道塌陷;改性膜在3 h内对茶多酚、茶多糖、茶蛋白即可达到最大浓缩度,减少50%浓缩时间;MCM-41和SBA-15膜长时间运行的浓缩降率仅为2.8%~6.1%,48 h下降率比显示改性膜达标使用时长增加112.5%~137.5%,亲水性和抗污堵能力均大幅提升,可有效满足功能化茶浓缩精度。     

Heat propagation in thermally conductive polymers of PA6 and hexagonal boron nitride

Thermally conductive polymers offer new possibilities for the heat dissipation in electric and electronic components, for example, by a three‐dimensional shaping of the heat sinks. To face safety regulations, improved fire performance of those components is required. In contrast to unfilled polymers, those materials exhibit an entirely different thermal behavior. To investigate the flammability, a phosphorus flame retardant was incorporated into thermally conductive composites of polyamide 6 and hexagonal boron nitride. The flame retardant decreased the thermal conductivity only slightly. However, the burning behavior changed significantly, due to a different heat propagation, which was investigated using a thermographic camera. An optimum content of hexagonal boron nitride for a sufficient thermal conductivity and fire performance was found between 20 and 30 vol%. The improvement of the fire performance was due to a faster heat release out of the pyrolysis zone and an earlier decomposition of the flame retardant. For higher contents of hexagonal boron nitride, the heat was spread faster within the part, promoting an earlier ignition and increasing the decomposition rate of the flame retardant.     

Effect of moisture and filler content on the structural,thermal and dielectric properties of polyamide‐6/boehmite alumina nanocomposites

Polyamide‐6 (PA‐6)/boehmite alumina (BA) nanocomposites were prepared via direct melt compounding. Structural, thermal and dielectric properties of ‘as‐received’ (including moisture) and ‘dried’ (thermally treated) specimens were examined. The BA nanofiller was homogeneously dispersed in the PA‐6 matrix. XRD and FTIR revealed that crystallization of PA‐6 in the γ phase was favoured over α phase with increasing BA content. The crystallinity index (CI) and the percentage of α and γ phases were also evaluated. Dried specimens exhibited a lower CI than as‐received specimens while the CI decreased with the addition of filler. Broadband dielectric spectroscopy revealed the presence of γ, β and α relaxations, the Maxwell–Wagner–Sillars effect and the contribution of conductivity relaxation in the as‐received samples. The drying procedure unmasked a double feature of both β and α modes. The results of the complementary techniques were analysed and the effects of moisture and/or the incorporation of BA nanofiller on the microstructure of the PA‐6 matrix are disclosed. © 2019 Society of Chemical Industry     

Mechanical properties of continuous bamboo fiber-reinforced biobased polyamide 11 composites

This study is devoted to the analysis of the properties of continuous bamboo fiber (BF)-reinforced polyamide 11 (PA 11) composites. The SEM observations highlighted continuity between BFs and the polymeric matrix showing a high density of hydrogen bonds. The comparative calorimetric study of the matrix and its composites showed that the crystallinity of PA 11 was not modified by the presence of bamboo fibers. The physical aging observed in PA 11 is no more observed in composites due to physical interactions between PA 11 and BFs. The mechanical properties were investigated by tensile strength and dynamic mechanical analysis. The introduction of BFs enhanced Young's modulus of the matrix by a factor of 10. The presence of BFs also improved the storage shear modulus G′ over the whole temperature range. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47623.     

Comparative performance of carbon nanotube and nanoclay on thermal properties and flammability behavior of amorphous polyamide/SEBS blend

Multiwall carbon nanotubes (CNT) or montmorillonite clay (MMT-30B) were added to a poly(hexamethylene isophthalamide-co-terephthalamine) (an amorphous polyamide - aPA) and styrene-ethylene/butylene-styrene graphitized with maleic anhydride (SEBS) blend, in different concentrations, in order to investigate the morphology, thermal properties and flammability behavior. Different nanoparticle localizations in the phase blend were observed through transmission electronic microscopy. CNT nanoparticles are localized in SEBS phase, and MMT-30B nanoparticles in aPA phase. No significant changes were observed on transition temperatures and thermal stability with both nanoparticle additions. However, a slight increase on storage modulus for clay nanocomposites and a slight reduction for carbon nanotube nanocomposites were observed, due to their different phase localizations. Regarding flammability, CNT nanocomposites showed better performance as a flame retardant when compared to samples with MMT-30B. Although the MMT-30B nanocomposites could not be classified according to the UL-94 criteria, no dripped flaming particles were observed, due to the a char barrier formation on the polymer surface. The CNT nanocomposites were classified according to the UL-94 criteria as V-2. The CNT's selective localization on the SEBS phase decreases its heat-release rate, but no interconnected network structure was formed in the matrix to suppress the dripping flaming particles.     

高导热高介电BT/SiC/PA6复合材料的制备及性能研究

以聚酰胺(PA6)为基体,氮化硅(SiC)为导热填料,钛酸钡(BT)为介电填料,通过热压法制备出系列复合材料;研究了不同粒径填料的搭配对材料导热与介电性能的影响。结果表明:在填充量较低时,使用混合粒径导热填料能产生一定的级配效应,从而提高复合材料的导热性能。总填充量为26%时,以4∶1的比例,用粒径为0.5~0.7μm和3μm的SiC共同填充PA6,制备获得了最高导热系数为0.9198W/(m·K)的复合材料,而不同粒径、不同功能的混合功能填料还能产生协同效应,进一步提升材料的导热性能并使材料同时获得较好的介电性能,当SiC填充量为20%,BT填充量为20%时,复合材料的导热系数达到1.1110W/(m·K),介电常数到达16(100Hz),损耗保持在0.075(100Hz)左右。     

Polydimethylsiloxane wrapped aluminum diethylphosphinate for enhancing the flame retardancy of polyamide 6

Aluminum diethylphosphinate (ADP) was wrapped with polydimethylsiloxane (PDMS) by a facile method to improve its hydrophobic properties. The morphology and properties of PDMS-modified ADP (PDMS-ADP) were investigated by thermogravimetric analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and water contact angle tests. The water contact angle of PDMS-ADP was increased from 126° to 151° as compared with that of ADP, which indicates that PDMS-ADP showed good hydrophobic properties. Then, ADP and PDMS-ADP were introduced into polyamide 6 (PA6) matrices to study the flame retardancy of the composites. The flammability of the PA6/ADP and PA6/PDMS-ADP composites was much lower than that of pure PA6. The composites PA6-1 (with the addition of 15 wt% ADP) and PA6-4 (with the addition of 12 wt% PDMS-ADP) could pass the UL-94 V-0 in the vertical burning test. Meanwhile, the peak heat release rates of PA6-1 and PA6-4 were 212 and 192 kW/m², with reductions of 67.3 and 70.4%, respectively, compared with pure PA6. These results indicated that the coating of PDMS could enhance the flame-retardant efficiency of ADP.     

改性三氧化二锑协效二乙基次磷酸铝阻燃PA6研究

采用硅烷偶联剂（KH560）对三氧化二锑（Sb₂O₃）进行表面改性处理，并将其协效二乙基次磷酸铝（ADP）应用于聚酰胺6（PA6）阻燃研究。采用傅里叶变换红外光谱和热失重分析对改性Sb₂O₃进行表征，运用垂直燃烧、氧指数、锥形量热仪、热分析以及扫描电子显微镜和拉曼光谱等对阻燃PA6进行了阻燃性能及机理分析。结果表明，改性 Sb₂O₃与Sb₂O₃相比，与ADP具有更好的协同阻燃效应，其作用机制主要是在气相发挥阻燃作用；当ADP含量为8 %，改性Sb₂O₃含量为2 %时，阻燃PA6复合材料的UL 94等级达到V?0级，极限氧指数达到33.8 %。     

The formation of fibrous structure of polyamide 6 induced by the three-step forming process and its prominent reinforcement in nitrile rubber

Nitrile rubber (NBR) blends with excellent performance have always been a hot research topic in petroleum field. Due to the excellent performance and compatibility of polyamide 6 (PA6), it provides an opportunity for the preparation of high-performance NBR/PA6 blends. In this article, NBR/PA6 blends were prepared by the three-step molding process. Experimentally, it was found that PA6 has a prominent reinforcement effect in NBR matrix. The variation of this mechanical property was investigated from different aspects of the crystal structure, crystallinities, phase morphology, and so on. It can be cleared that the formation of fibrous structure of PA6 phase is the main factor for reinforcement of the polymer blends. Meanwhile, the formation mechanism of the special phase structure induced by the three-step process is deeply expounded and its structural evolution schematic is established. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47472.