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941.
《先进技术聚合物》2018,29(5):1518-1525
A hindered polyphenol, oligo(4‐methoxyphenol), has been first successfully synthesized via a mild biocatalytic pathway using horseradish peroxidase as catalyst in water without any additive. Then the efficiency of oligo(4‐methoxyphenol) in stabilization of polypropylene (PP) was evaluated in terms of thermal analysis and accelerated aging test. It was observed that the apparent activation energy for thermal decomposition of PP/oligo(4‐methoxyphenol) calculated by Friedman's method is higher than that of virgin PP. Oligo(4‐methoxyphenol)‐stabilized PP maintains its tensile strength even after aging at 120°C for 800 hours. Oxidation induction time and onset oxidation temperature of PP/oligo(4‐methoxyphenol) are higher than both virgin PP and PP/4‐methoxyphenol, as well as PP stabilized with commercially available 6‐di‐tert‐buty‐4‐methylphenol or 1076. These results indicate that oligo(4‐methoxyphenol) can effectively improve the thermo‐oxidative resistance of PP. Noting that oligo(4‐methoxyphenol) is synthesized via enzymatic polymerization in water under mild condition with a facile procedure, oligo(4‐methoxyphenol) is thus proposed as a new efficiency and readily available antioxidant for PP. 相似文献
942.
《先进技术聚合物》2018,29(9):2449-2456
In this work, a novel hyperbranched and phosphorus‐containing triazine derivative (HPCFA) is synthesized. HPCFA is used as charring‐foaming agent and combined with ammonium polyphosphate (APP) as intumescent flame retardant to flame retard polypropylene (PP). PP/HPCFA/APP composite can achieve limited oxygen index value of 31% and pass UL 94V‐0 rating by addition of 20 wt% HPCFA/APP (1/2, w/w). Besides, HPCFA is compared with another hyperbranched charring‐foaming agent (HCFA). HPCFA and HCFA have similar chemical structure, and their only difference is that HPCFA has phosphorus‐containing unit in the main chain compared with HCFA. HPCFA/APP system exhibits superior flame retardancy compared with HCFA/APP system. Char residue analysis demonstrates that HPCFA/APP system can form denser and more compact char layer in comparison with that of HCFA/APP system. 相似文献
943.
Yuji Sasanuma Akihiro Abe Takako Sasanuma Yukishige Kitano Akira Ishitani 《Journal of Polymer Science.Polymer Physics》1993,31(9):1179-1186
Small-angle x-ray scattering (SAXS) intensity for the lamellar structure of polymeric materials has been formulated with consideration of structural defects such as the finiteness of the lamellar stack, the lamellar bend, and the paracrystalline distortions. In particular, the effects of the lamellar bend on the SAXS profile have been elucidated on the basis of Vonk'xss formula γ1(x) – γ(x)exp(?2x/d). Here, the scattering profile due to the lamellar bend is shown to be expressed by a Cauchy function. The integral breadth is equal to 2π/d, being independent of the order of scattering. As an example of the SAXS analysis based on the theory, the characterization of the lamellar structure in the “hard” elastic polypropylene films is reported. The long period and the lamellar thickness are evaluated from the correlation function, and the distortion length and Hosemann's g factor are estimated according to the procedure presented here. On the basis of these structural parameters, the relationship between the manufacturing process and the lamellar structure of the polypropylene films is discussed. © 1993 John Wiley & Sons, Inc. 相似文献
944.
稀土氧化物对聚丙烯晶型和动态力学性能的影响 总被引:6,自引:1,他引:6
本文用DSC和粘弹谱仪研究了La_2O_3,Y_2O_3和混合稀土氧化物对全同聚丙烯(iPP)的结晶行为,熔融行为和动态力学性能的影响。结果表明不同的iPP/稀土氧化物复合材料中iPP的晶型不同,Y_2O_3和稀土氧化物是iPP的α和β晶成核剂,La_2O_3是α晶成核剂。含有β晶试样同只有α晶试样相比,在T_g真松弛区其tanδ值较低,贮能模量E从-50℃~+50℃较高,从+50℃~+145℃则E值较低。 相似文献
945.
Morphology of isotactic polypropylene-polyamide 66 blends and their mechanical properties 总被引:1,自引:0,他引:1
Compounds were prepared with isotactic polypropylene (iPP) matrix and recycled polyamide 66 fibres (PA66), which were obtained as soft waste in industrial production process. Blends with pristine PA66 pellets were prepared as comparison. The blends showed the presence of PA66 particles dispersed in the PP continuous phase. Considering the incompatibility of the two polymers the addition of isotactic polypropylene grafted with maleic anhydride (iPPgMA) as compatibilizer was investigated: the blends were characterized by thermal, mechanical, dynamic-mechanical and morphological analyses. The presence of the compatibilizer significantly influences the morphology of the blends, inducing a finer dispersion and promoting interfacial adhesion. The characterization of pristine and recycled PA66 did not show a meaningful difference in the value of molecular weight, on the other hand marked differences were presented in the flexural moduli of the two materials; analogous differences were exhibited by the blends: compounds prepared with recycled PA66 showed flexural moduli higher than compatibilized blends with pristine PA66. 相似文献
946.
947.
Polypropylene powders as the adsorbent for organic solution containing n-hexadecane and olive oil were employed as the carbon source for producing an alkaline lipase from Acinetobacter radioresistens. The best volumetric ratio of n-hexadecane to olive oil around 5 for lipase production was determined from shake-flask and fermentation cultivations. The
existence of a maximum time course lipase activity of the aqueous phase was attributed to the compensation effects of olive
oil on cell growth and lipase production, repression of lipase synthesis by oleic acid, and lipase adsorption on the supports.
A linear relationship between the average cell growth rate in the exponential phase and the ratio of surface areas of the
supports was found. The benefits of using the present fermentation process include less foaming and emulsion of the broth,
less organic phase used, higher lipase production, and easy recovery of the lipase in the centrifugation step. 相似文献
948.
Biaxially Oriented Polypropylene (BOPP) Surface Modification by Nitrogen Atmospheric Pressure Glow Discharge (APGD) and by Air Corona 总被引:2,自引:0,他引:2
Guimond Sébastien Radu Ion Czeremuszkin Gregory Carlsson David J. Wertheimer Michael R. 《Plasmas and Polymers》2002,7(1):71-88
We compare two surface treatments of biaxially-oriented polypropylene (BOPP), which are carried out in the same dielectric barrier discharge (DBD) apparatus, namely air corona, and N2 atmospheric pressure glow discharge (APGD). Changes in the surface energy and chemistry are investigated by contact angle measurements, by X-ray photoelectron spectroscopy (XPS) and by attenuated total reflectance infrared spectroscopy (ATR-FTIR). It is shown that N2 APGD treatment leads to a higher surface energy than air corona treatment, and to the formation of mostly amine, amide, and hydroxyl functional groups at the polypropylene surface. Finally, hydrophobic recovery of the treated film is studied; for both treatment types, the increased surface energy is found to decay in a similar manner with increasing storage time after treatment. 相似文献
949.
The static loading-induced stress oscillation (SO) in syndiotactic polypropylene (sPP) was studied by modulated differential scanning calorimetry (TMDSC). Samples were taken from the initial necked, premature and mature SO oscillation ranges, respectively, and the related calorimetric responses were compared to those of the bulk material. It was established that necking caused some decrease in the crystallinity. In addition, necking resulted in cold crystallization that was assigned to a polymorphic transition (from all-trans to helical conformation) based on literature results. The TMDSC response was practically the same for necked samples with and without SO. A model was proposed to explain SO. The model assumes the presence of a network (similar to that of semicrystalline thermoplastic elastomers), which is highly stretchable and fails by sudden voiding at the intersections of shear micro bands intermittently.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
950.
Bing Na Qin Zhang Hong Yang Qiang Fu Yong-feng Men 《高分子科学》2007,(3):285-290
In this communication, by means of stress relaxation experiments, the viscous stress at various strains during tensile deformation of oriented polyolefin samples including high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and isotactic polypropylene (iPP), has been determined. The viscous stress in the oriented samples takes up to 50%-70% of the total stress, which is unusually high compared with their isotropic counterparts. The unusual high viscous stress was discussed based on mainly the existence of shish structure in oriented polyolefins, which could enhance the inter-lamella coupling significantly. 相似文献