Solvent-induced crystallinity in poly(aryl-ether-ether-ketone) [PEEK]

The amount and structure of the crystals formed by the solvent-induced crystallization (SIC) following a sorption-desorption cycle of five fluids (benzene, toluene, chloroform, methylene chloride, and carbon disulfide) in amorphous PEEK was determined by wideangle x-ray scattering (WAXS). The SIC crystal structure was compared with that produced by thermal methods, both those formed at low temperature by heating the amorphous material 10–20°C above T_g or by cooling from the melt. Although smaller in size, the SIC crystals are tighter and more organized than those produced thermally. The WAXS data indicates that all five fluids produce approximately 35% crystallinity in PEEK. Gravimetric data suggest that a low-density region, consisting of either microvoids or highly disordered amorphous region, surrounds the crystals.     

Preparation and characterization of poly(m-xylylene oxamide) and its copolymer

New polyoxamides, poly(m-xylylene oxamide) (PMXD2) and its copolymer with 2-methyl-1,5- pentanediamine (P(MXD2/M52)) with relative viscosity up to 4.6 were synthesized via spray/solid state polymerization. The obtained polyoxamides were characterized by FTIR, NMR, WAXD, DSC and TGA. The T_m of the copolymers decreased with increasing percentage of poly(2-methyl-1,5- pentaneoxamide) (PM52) in the copolymer from 346°C for 100% poly(meta-xylyleneoxamide) (PMXD2) to 277°C for copolymers of PMXD/PM52 (60/40). TGA analysis revealed that the thermal stability of the copolymers compared well with commercial PA6 and XRD studies suggested the copolymers possessed high crystallinity. DMA profile of the PMXD/PM52 (70/30) copolymer showed better mechanical performance with a storage modulus of about 7.2 GPa as compared to 1.8 GPa of PA6 at 25°C.     

FTIR spectroscopy of biodegraded historical textiles

Fungal attack is a common and severe problem in the storage rooms of museums. Fungi can damage different materials; organic materials are especially sensitive. In this work two different FTIR spectroscopy methods (micro-spectroscopy with diamond anvil cell and ATR) were used to investigate structural changes on biodeteriorated and non-affected textile fibres obtained from different Slovene museums and sacred objects. Several structural changes were observed in spectra of biodeteriorated as well as of non-affected cellulosic fibres, whereas no changes were observed in proteinaceous fibres. In the scope of spectral analysis crystallinity index has also been calculated by comparing two different band ratios. The research showed that the crystallinity index, calculated from the band intensity ratio I₁₃₇₂/I₂₉₀₀ groups fibres into two groups; biodeteriorated fibres predominantly have lower crystallinity index.     

磷酸钙料浆性质对雾化干燥羟基磷灰石微球的影响

以甲烷火焰为干燥介质,将3种不同性质的磷酸钙料浆利用火焰-雾化干燥法制备出不同形态和性能的羟基磷灰石(HA)微球。对比分析了料浆成分、温度、结晶程度等参数对所得HA微球形貌、相组成、结晶度、比表面积以及孔隙分布等的影响。结果表明,料浆中的氨水在雾化干燥过程中会聚集突释,得到具有“爆破状”开口的形态的HA微球。低温并且结晶程度较低的磷酸钙料浆经过火焰-雾化快速干燥后,得到结构松散、结晶度较低、比表面积及孔体积较大的HA微球,说明料浆的性质将会直接影响火焰-雾化干燥后HA微球的特性。     

MOCVD技术制备的ZnS:Mn电致发光薄膜结晶性及Mn2+分布

本文报导了用MOCVD技术制备的ZnS:Mn电致发光薄膜为立方晶相,结晶取向性好,颗粒大。从高倍率的扫描电镜拍摄的照片观察到薄膜的表面平滑。SIMS测量表明Mn2+在ZnS薄膜纵向分布均匀,但在两侧有起伏,可能的原因是在生长的初终阶段流量的突变使化合物的化学计量比偏离而产生位错,引起原子的局部堆积,并且由于初终阶段ZnS:Mn生长的衬底不同使原子堆积层厚度不同。     

六方氮化硼的振动光谱与立方氮化硼的合成

 以X射线衍射分析作参比，分析了高度三维有序到近乱层结构的9种六方氮化硼的红外和拉曼光谱，并进行了立方氮化硼的高温高压合成。光谱分析表明，随着晶性的降低，六方氮化硼的低频红外吸收峰的位置及拉曼谱线等基本振动光谱发生明显的特征性的变化，并伴随出现各自不同的次级光谱结构。合成结果表明，在触媒作用下，立方氮化硼的形成需要六方氮化硼原料有一定的结晶度，但立方氮化硼合成效果与六方氮化硼结晶度并非是简单的单调关系。对振动光谱和合成试验的结果进行了讨论。     

表面润湿法合成β沸石体系中晶种作用的研究

系统研究了表面润湿法合成β沸石的体系中,干晶种、润湿态晶种、异晶晶种(Y沸石、ZSM 5沸石)以及碱处理β沸石晶种在此晶化体系中的作用.采用β沸石产品及异晶作晶种时,可使产品的相对结晶度稍有提高,但对沸石微晶核的结构导向作用不明显.经浓碱液处理20min后的β沸石产品(碱处理晶种)作晶种引入晶化体系后,可以显著提高产品的相对结晶度,降低模板剂的用量,缩短晶化诱导期,成为表面润湿法合成β沸石体系的有效晶种形式.     

Polypropylene/montmorillonite nanocomposites toughened with SEBS‐g‐MA: Structure–property relationship

Polypropylene (PP)/organo‐montmorillonite (Org‐MMT) nanocomposites toughened with maleated styrene‐ethylene‐butylene‐styrene (SEBS‐g‐MA) were prepared via melt compounding. The structure, mechanical properties, and dynamic mechanical properties of PP/SEBS‐g‐MA blends and their nanocomposites were investigated by X‐ray diffraction (XRD), polarizing optical microscopy (POM), tensile, and impact tests. XRD traces showed that Org‐MMT promoted the formation of β‐phase PP. The degree of crystallinity of PP/SEBS‐g‐MA blends and their nanocomposites were determined from the wide angle X‐ray diffraction via profile fitting method. POM experiments revealed that Org‐MMT particles served as nucleating sites, resulting in a decrease of the spherulite size. The essential work of fracture approach was used to evaluate the tensile fracture toughness of the nanocomposites toughened with elastomer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3112–3126, 2005