用CS－1高效催化剂生产聚丙烯树脂的纺丝试验

研究了用ＣＳ－１高效催化剂生产聚丙烯树脂的纺丝性能，得出采用该催化剂并结合分子量调节剂可以得到熔融指数较大，分子量分布较窄的聚丙烯树脂，其纺丝及力学性能都比较好。     

Radiation flux distribution over solar images formed on the focal plane by a paraboloidal reflector with tracking errors

The radiation flux distribution of off-centered solar images formed by a sun-tracking paraboloidal reflector is theoretically analyzed for several tracking error angles using Jose’s sunshape equation and assuming a specularly reflecting surface without taking meteorological conditions into consideration. The results are printed out by computer in the form of shade density maps to bring out a clear contrast to the low and high flux areas of a full image.     

Grafting polymerization of l-lactide on the surface of hydroxyapatite nano-crystals

A novel method of grafting ring-opening polymerization of l-lactide (LLA) onto the surface of hydroxyapatite nano-particles (n-HAP) was developed. PLLA was directly connected onto the HAP surface through a chemical linkage. The PLLA-g-HAP particles could be stably dispersed in organic solvent such as chloroform for several weeks. The n-HAP particles still retained the original dimension and shape after the grafting of PLLA. Compared with the ³¹P MAS-NMR spectrum of pure HAP powders, there appeared a downfield displacement of 1.2 ppm in the spectrum of PLLA-g-HAP. Fourier transformation infrared (FT-IR) spectra further confirmed the existence of PLLA on the surface of PLLA-g-HAP. The amount of grafted polymer determined by thermal gravimetric analysis (TGA) was about 6% in weight. The tensile strength and elongation at break of the PLLA/PLLA-g-HAP composite containing 8 wt% of PLLA-g-HAP were 55 MPa and about 10-13%, respectively, while those of the PLLA/n-HAP composites were 40 MPa and 3-5%, respectively.     

Optical and surface properties of whey protein isolate coatings on plastic films as influenced by substrate,protein concentration,and plasticizer type

Composite film structures of common plastic polymers including polypropylene (PP) or poly(vinyl chloride) (PVC) with whey protein isolate (WPI) coatings may be obtained by a casting method. Optical and surface properties of the resulting WPI‐coated plastic films, as affected by protein concentration and plasticizer type, were investigated to examine the biopolymer coating effects on surface modification with polymeric substrates of opposite polarity. The measured properties involved specular gloss, color, contact angle, and critical surface energy. Regardless of the substrates, WPI‐coated films possessed excellent gloss and no color, as well as good adhesion between the coating and the substrate when an appropriate plasticizer was added to the coating formulations. The protein concentration did not significantly affect gloss of WPI‐coated plastic films. Among five plasticizers applied, sucrose conferred the most highly reflective and homogeneous surfaces to the coated films. The WPI coatings were very transparent and the coated films with various protein concentrations and plasticizers showed no noticeable changes in color. Experimental results suggest that WPI coatings formulated with a proper plasticizer can improve the visual characteristics of the polymeric substrate and enhance water wettability of the coated plastic films. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 335–343, 2004     

In situ preparation and properties of high‐solid‐content and low‐viscosity poly(methyl methacrylate/n‐butyl acrylate/acrylic acid)/poly(styrene/acrylic acid) composite latexes

With monodispersed poly(methyl methacrylate/n‐butyl acrylate/acrylic acid) [P(MMA/BA/AA)] seeded latex with a particle size of 485 nm and a solid content of 50 wt % as a medium, a series of stable P(MMA/BA/AA)/poly(styrene/acrylic acid) composite latexes with a high solid content (70 wt %) and low viscosities (500–1000 mPa · s when the shear rate was 21 s^?1) was prepared in situ via simple two‐step semicontinuous monomer adding technology. The coagulum ratio of polymerization was about 0.05 wt %. The particle size distribution of such latexes was bimodal, in which the large particle was about 589 nm and the small one was about 80 nm. The latexes combined good mechanical properties with good film‐forming properties. Differential scanning calorimetry showed that the corresponding latex film had a two‐phase structure. The morphology of the latex film was characterized with atomic force microscopy and scanning electron microscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1815–1825, 2007     

Ultrasonic oscillations effect on rheological and processing properties of metallocene‐catalyzed linear low density polyethylene

The effects of ultrasonic oscillations and die materials on die pressure, productivity of extrusion, melt viscosity of metallocene‐catalyzed linear low density polyethylene (mLLDPE), as well as their mechanism were studied in a special ultrasonic oscillations extrusion system developed in our lab. Die materials used in our experiment included steel, brass, and polytetrafluoroethylene (PTFE)_. The experimental results showed that ultrasonic oscillations as well as die materials have great influence on the rheological and processing behavior of mLLDPE. Ultrasonic oscillations can greatly increase the productivity of mLLDPE melt extruded through different dies, and can decrease the die pressure and the melt viscosity of mLLDPE. Compared with steel or brass die, mLLDPE melt extruded through PTFE die is more sensitive to ultrasonic oscillations. A possible mechanism for the improved processability of mLLDPE is proposed in this article. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1873–1878, 2003     

Structural and Electric Properties of Sol–Gel-Derived Ba0.9Sr0.1TiO3 Multilayers

Crack-free Ba_0.9Sr_0.1TiO₃ (BST) and Mn-doped Ba_0.9Sr_0.1TiO₃ (BSTM) multilayers with thickness over 2 μm have been prepared by chemical solution deposition based on one single precursor. Both multilayers exhibit good performance as Bragg reflectors. Mn doping tends to suppress the leakage current in BST multilayers effectively by smoothing the layers and the reduction of the charge carries. The Mn-doped BST multilayer displays an excellent ferroelectric property, with an average remnant polarization ( P _r⁺– P _r⁻)/2 of 12.69 μC/cm² and an average coercive field ( E ⁺ – E ⁻ )/2 of about 72.95 kV/cm under an applied field of 440 kV/cm.     

复合相刚玉颗粒构成对出铁沟浇注料抗热震稳定性的改善

根据本文中的机理A(引入热膨胀系数失配的第二相)机理B(引进热膨胀系数小的第二相),通过引入热膨胀系数不同的第二、三相形成复合相刚玉颗粒构成,使出铁沟浇注料抗热震稳定性得到改善。     

浅析无线网现状及相关技术

无线网作为一种现代化的技术手段,随着网络信息技术的不断发展完善,在实际中的应用越来越广泛和普遍,对于无线网技术的研究与关注内容也越来越多,进行无线网现状以及相关技术的研究分析,有利于促进无线网在实际应用中的改进和提升,具有积极的作用和意义。下文将结合无线网在实际网络通信传输中的应用现状,以网络建设中的安全管理为例,对其安全保护现状以及存在的问题、解决措施等进行分析论述。     

基于统一身份认证的数据加密技术在网络安全中的应用简

随着计算机技术的不断发展,网络应用到生活中的各个方面,网络在广泛应用的同时,网络安全问题也越来越多,使得用户在网络应用中要不断的进行身份认证来保证自身数据的安全。然而重复进行身份认证过程繁琐,同时也存在数据信息泄露的安全隐患,因此,提出了统一身份的认证系统。本文主要对统一身份认证系统和数据加密技术进行介绍,并对kerboeros网络认证协议的认证过程进行探讨,旨在提高网络的安全性。