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101.
102.
The plastic deformation mechanism operating in polymer glasses is analyzed. The whole process consists of two main stages: nucleation of special shear defects, called PSTs (plastic shear transformations), and their disappearance. The important feature of plastic deformation of glasses is the storage of a large amount of internal energy ΔUdef upon straining. Such energy storage is the critical issue for mechanical performance of polymeric material: if the amount of stored energy is high, the appearance of macroscopic failure is very probable while glassy materials collecting a small amount of stored deformation energy are quite ductile. It is proposed that the rate of disappearance of PSTs is a key factor in dissipation of stored deformation energy. A parameter describing the dissipation ability of material upon deformation is introduced. 相似文献
103.
Monwar M Oh SJ Rinaldi PL McCord EF Hutchinson RA Buback MM Latz H 《Analytical and bioanalytical chemistry》2004,378(6):1414-1427
Poly(n-butylacrylate-co-carbon monoxide-co-ethylene) (polyEBC) samples prepared from 13C-labeled monomer, n-butyl acrylate, were characterized using two dimensional (2D) pulsed field gradient (PFG) 750 MHz NMR spectroscopy. To elucidate the complex structure of the terpolymer, 2D-1H/13C-heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond correlation (HMBC) experiments were conducted by selectively exciting the enhanced resonances in the spectra of two polymer samples, one polymer resulting from synthesis with 1-13C-n-butylacrylate monomer and a second polymer obtained from a synthesis with 2-13C-n-butylacrylate monomer. High-resolution 2D-NMR combined with 13C-labeling of the polymer greatly simplifies the 2D-NMR spectra, selectively enhances the weak peaks from low occurrence B-centered triad structures, and aids in their resonance assignments. In all experiments, the sample temperature was 120 degrees C, to ensure a homogeneous solution and sufficient molecular mobility. Electronic Supplementary Material: Supplementary material (1D 13C NMR spectra of the 13C-labeled and unlabeled polymers) is available in the online version of this article at http://dx.doi.org/100.1007/s00216-003-2402-3. 相似文献
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A novel dual stage chemiluminescence detection system incorporating individually controlled hot stages has been developed and applied to probe for material interaction effects during polymer degradation. Utilization of this system has resulted in experimental confirmation for the first time that in an oxidizing environment a degrading polymer A (in this case polypropylene, PP) is capable of infecting a different polymer B (in this case polybutadiene, HTPB) over a relatively large distance. In the presence of the infectious degrading polymer A, the thermal degradation of polymer B is observed over a significantly shorter time period. Consistent with infectious volatiles from material A initiating the degradation process in material B it was demonstrated that traces (micrograms) of a thermally sensitive peroxide in the vicinity of PP could induce degradation remotely. This observation documents cross-infectious phenomena between different polymers and has major consequences for polymer interactions, understanding fundamental degradation processes and long-term aging effects under combined material exposures. 相似文献
106.
共混合聚(醚-酯)多嵌段共聚物的表面表征及其血液相容性研究 总被引:2,自引:0,他引:2
本文通过X-射线光电子能谱(XPS)、表面接触角、表面ξ电位和血液相容性实验,研究了聚(醚-酯)多嵌段共聚物及其共混物的表面组成和性质与血液相容性的关系。实验结果表明,疏水性的PET-PTMO多嵌段共聚物的血液相容性很差,并且与表相中软段的富集量无关;当亲水性的PET-PEO多嵌段共聚物与疏水性的PET-PTMO多嵌段共聚物共混后,发现存在着一个最佳的共混比例,此时材料表面的血小板粘附量大大降低。对于共混物,表相△[C—O)/[C—O]和表面ξ电位可以较好地与血小板粘附量相关联。以上结果清楚地表明,材料表面的亲-疏水性平衡、软段深度层次分布及表面电位是影响血液相容性的重要因素。 相似文献
107.
108.
NAK-12树脂脱除蚕蛹复合氨基酸异味及褐变物质的研究 总被引:6,自引:0,他引:6
本文研究了用NAK-12吸附树脂脱除蚕蛹复合氨基酸异味及褐变色素的条件,初步分析了蚕蛹复合氨基酸异味产生的原因,实验结果表明:当流速为3BV/h时,1ml NAK-12吸附树脂能吸附1.75g蚕蛹复合氨基酸中的异味物质;能吸附1.45g蚕蛹复合氨基酸中的褐变物质。甲醇是异味物质和褐变物质的良好洗脱剂,用pH1.0的甲醇以1BV/h流速洗脱,仅用3.5BV的洗脱剂即可完全洗脱异味物质和褐变物质,蚕蛹复合氨基酸异味产生的可能机理是:加热蚕蛹复合氨基酸液时,其苯丙氨酸,蛋氨酸,蛋氨酸,异亮氨酸,亮氨酸,苏氨酸被氧化脱氨,生成挥发性醛,而其褐变则是赖氨酸,精氨酸与还原糖发生Maillard反应生成褐变物质引起的。 相似文献
109.
110.
We have studied on the solubilization of single-walled carbon nanotubes (SW-CNTs) into aqueous and organic media by the use of a variety of nanometer size-controlled fluorinated self-assemblies, which were formed by the aggregations of end-capped fluoroalkyl segments in fluoroalkyl end-capped acrylic acid oligomers [RF-(ACA)n-RF], N,N-dimethylacrylamide oligomers [RF-(DMAA)n-RF], acryloylmorpholine oligomers [RF-(ACMO)n-RF], and N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomers [RF-(DOBAA)n-RF]. Fluorinated self assemblies formed in organic media (colorless solutions) could solubilize SW-CNTs into organic media to afford the transparent pale yellow solutions. The dynamic light scattering measurements showed that the size of fluorinated self-assemblies increased after the solubilization of SW-CNTs into organic media. It was suggested that the solubilization of SW-CNTs into organic media is due to the encapsulation of SW-CNTs into fluorinated assemblies. Fluorinated assemblies were also able to solubilize SW-CNTs into water to give the transparent gray solutions. Among a variety of fluorinated assemblies, fluorinated assemblies formed by RF-(ACMO)n-RF [RF = CF(CF3)OC6F13] oligomer was more effective for the solubilization of SW-CNTs into both aqueous and organic media. Contact angle measurements of dodecane and the fluorescence spectra for poly(methyl methacrylate) cast film modified by fluorinated self-assemblies—SW-CNTs complexes showed that SW-CNTs are dispersed above the PMMA surface. 相似文献