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51.
52.
火焰原子吸收光谱法测定苋菜中8种矿物元素 总被引:5,自引:0,他引:5
用空气-乙炔火焰原子吸收光谱法对苋菜中钾、钙、镁、铁、锌、铜、锰、铅8种矿物元素进行了测定,对样品前处理方法、酸度、共存元素干扰及元素线性范围进行了实验。在选定的实验条件下,可以用火焰原子吸收光谱法对苋菜中8种元素进行分别测定,互不干扰。方法的相对标准偏差为0.08%~3.17%(n=5),加标回收率为91.5%~102%。 相似文献
53.
Tri(acryloyloxyethyl) phosphate (TAEP) was blended in different ratios with epoxy acrylate EB600 and polyurethane acrylate EB270 to obtain a series of UV curable flame retardant resins. The thermal degradation mechanisms of their cured films in air were studied by thermogravimetric analysis, in situ Fourier‐transform infrared spectroscopy, and direct pyrolysis/mass spectrometry measurements. The results showed that the phosphate group in TAEP first degraded to form poly(phosphoric acid) before the degradation of EB600. Then, the formed poly(phosphoric acid) effectively promoted the conversion of EB600 to form char, which prevented the sample from further burning. However, urethane group in EB270 degraded simultaneously with phosphate group in TAEP, leading to not effectively increase the conversion of EB270 to char during the thermal degradation. It was thus found that the addition of TAEP more effectively improved the thermal stability, flame retardance, and the char yield during combustion of EB600 than those of EB270. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3130–3137, 2006 相似文献
54.
The N‐[3‐(dimethoxy‐methyl‐silanyl)‐propyl]‐N′‐ (9‐methyl‐3,9‐dioxo‐2,4,8,10‐tetraoxa‐3,9‐diphospha‐spiro[5.5]undec‐3‐yl)‐ethane‐1,2‐diamine/dimethoxy dimethyl silane copolymer (PSiN II), which simultaneously contains silicon, phosphorus, and nitrogen, is synthesized and incorporated into polypropylene (PP). The flame retardancy is evaluated by the limiting oxygen index value, which is enhanced to 29.5 from 17.4 with 20% total loading of PSiN II. The thermal degradation behavior of PP/PSiN II is investigated by thermogravimetric analysis under N2 and air. The PP/PSiN II sample degrades at 400°C for different amounts of time, and the process of degradation is studied by Fourier transform IR. The morphology of the char formed at 400°C for 10 min is investigated by scanning electron microscopy. The swollen inner structure, close, and smooth outer surface provide a much better barrier for the transfer of heat and mass during fire and good flame retardancy. The thermal stability of PP is improved by incorporation of PSiN II. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2487–2492, 2005 相似文献
55.
56.
聚酰胺66的复配阻燃研究 总被引:3,自引:0,他引:3
采用35%磷-溴-锑复配阻燃体系对聚酰胺66进行阻燃,极限氧指数可提高到33.6%,达到UL94-V0级(1.6mm),且无熔融滴落。阻燃体系的添加会导致聚酰胺66力学性能的下降,但与无机阻燃体系相比较,磷-溴-锑复配阻燃体系对聚酰胺66的力学性能影响较小。采用扫描电镜观察阻燃剂在聚酰胺66中的分散效果,发现分散均匀的体系,在水中或者在110℃的析出实验条件下,阻燃剂的析出量很小,可以维持较长时间的阻燃效果。 相似文献
57.
A series of phosphorus‐containing, wholly aromatic thermotropic copolyesters from acetylated 2‐(6‐oxide‐6H‐dibenz〈c,e〉〈1,2〉oxa phosphorin‐6‐yl)‐1,4‐dihydroxy phenylene, p‐acetoxybenzoic acid, terephthalic acid, and isophthalic acid were prepared by melting polycondensation. The structure and basic properties of the polymers, such as the glass‐transition temperature (Tg), melting temperature (Tm), thermal stability, crystallinity, and liquid crystallinity, were investigated with Fourier transform infrared, elemental analysis, differential scanning calorimetry (DSC), thermogravimetric analysis, wide‐angle X‐ray diffraction, and hot‐stage polarizing optical microscopy. The copolyesters had relatively high Tg values ranging from 183 to 192°C. The Tm values obtained from DSC curves for samples P‐20 and P‐25 were 290 and 287°C, respectively (where the number in the sample name indicates the molar fraction of the phosphorus‐containing monomer in the reactants). The initial flow temperatures of other samples observed with hot‐stage polarizing microscopy were 271–290°C. The 5% degradation temperatures in nitrogen ranged from 431 to 462°C, and the char yields at 640°C were 41–52%. All the copolyesters, except P‐40, were thermotropic and nematic. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1278–1284, 2002 相似文献
58.
59.
Khalil Faghihi 《应用聚合物科学杂志》2006,102(5):5062-5071
Six new flame‐retardant poly(amide‐imide)s (PAIs) 9a–f with high inherent viscosities containing phosphine oxide and hydantoin moieties in main chain were synthesized from the polycondensation reaction of N,N′‐(3,3′‐diphenylphenylphosphine oxide) bistrimellitimide diacid chloride 7 with six hydantoin derivatives 8a–f by two different methods such as solution and microwave assisted polycondensation. Results showed that the microwave assisted polycondensation, by using a domestic microwave oven, proceeded rapidly, compared with solution polycondensation, and was completed in about 7–9 min. All of the obtained polymers were fully characterized by means of elemental analysis, viscosity measurements, solubility test, and FTIR spectroscopy. Thermal properties and flame retardant behavior of the PAIs 9a–f were investigated using thermal gravimetric analysis (TGA and DTG) and limited Oxygen index (LOI). Data obtained by thermal analysis (TGA and DTG) revealed that these polymers showed good thermal stability. Furthermore, high char yields in TGA and good LOI values indicated that these polymers are capable of exhibiting good flame retardant properties. These polymers can be potentially utilized in flame retardant thermoplastic materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5062–5071, 2006 相似文献
60.
Intumescent coatings are increasingly used as a method of passive fire protection on steel constructions. By forming a carbon network and releasing a blowing agent, the thin intumescent film swells 100‐fold at elevated temperatures. The highly insulating foam effectively prevents the load bearing steel from reaching its critical temperature at which it looses its mechanical properties and collapses. The role of the carbon donor in intumescent coatings has been studied. Comparison in temperature development, foaming ratios, and rheological behavior has been performed between formulations containing pentaerythritol (penta), di–penta, and tri–penta. A simulated fire test, in which the temperature development during intumescence was studied, showed that the formulations containing penta were considerably more efficient in keeping a low temperature throughout the process. A more rapid temperature development was displayed when using di–penta and tri–penta as the carbon donor. Rheometer tests indicate that penta formulations enter the intumescent process at a lower temperature and stays in it for a longer time than di–penta and tri–penta formulations. Furthermore, the crossover temperature and maximum phase angle are shifted towards higher temperatures by replacing penta with di–penta and with tri–penta in the formulations, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 748–753, 2007 相似文献