Castell P, Medel F J, Martinez M T, Puértolas J A
Department of Carbon Nanostructures and Nanotechnology, Instituto de Carboquímica-CSIC, Zaragoza 50018, Spain.
J Nanosci Nanotechnol. 2009 Oct;9(10):6055-63. doi: 10.1166/jnn.2009.1555.
Single walled carbon nanotubes (SWNT) have been incorporated into a polypropylene (PP) matrix in different concentrations (range: 0.25-2.5 wt%). The nanotubes were blended with PP particles (approximately 500 microm in size) before mixing in an extruder. Finally, rectangular plates were obtained by compression moulding. PP-SWNT composites were gamma irradiated at different doses, 10 and 20 kGy, to promote crosslinking in the matrix and potentially enhance the interaction between nanotubes and PP. Extensive thermal, structural and mechanical characterization was conducted by means of DSC, X-ray diffraction, Raman spectroscopy, uniaxial tensile tests and dynamic mechanical thermal (DMTA) techniques. DSC thermograms reflected higher crystallinity with increasing nanotube concentration. XRD analysis confirmed the only presence of a monoclinic crystals and proved unambiguously that CNTs generated a preferred orientation. Raman spectroscopy confirmed that the intercalation of the polymer between bundles is favored at low CNTs contents. Elastic modulus results confirmed the reinforcement of the polypropylene matrix with increasing SWNT concentration, although stiffness saturation was observed at the highest concentration. Loss tangent DMTA curves showed three transitions for raw polypropylene. While gamma relaxation remained practically unchanged in all the samples, beta relaxation temperatures showed an increase with increasing CNT content due to the reduced mobility of the system. Gamma-irradiated PP exhibited an increase in the beta relaxation temperature, associated with changes in glass transition due to radiation-induced crosslinking. On the contrary, gamma-irradiated nanocomposites did not show this effect probably due to the reaction of radiative free radicals with CNTs.
单壁碳纳米管（SWNT）已被以不同浓度（范围：0.25 - 2.5 wt%）掺入聚丙烯（PP）基体中。在挤出机中混合之前，将纳米管与尺寸约为500微米的PP颗粒进行共混。最后，通过压缩模塑获得矩形板。对PP - SWNT复合材料进行了10 kGy和20 kGy不同剂量的γ辐照，以促进基体中的交联并潜在增强纳米管与PP之间的相互作用。借助差示扫描量热法（DSC）、X射线衍射、拉曼光谱、单轴拉伸试验和动态机械热分析（DMTA）技术进行了广泛的热、结构和力学表征。DSC热谱图表明，随着纳米管浓度的增加，结晶度更高。XRD分析证实仅存在单斜晶体，并明确证明碳纳米管产生了择优取向。拉曼光谱证实，在低CNT含量下，聚合物在束间的插层更有利。弹性模量结果证实，随着SWNT浓度的增加，聚丙烯基体得到增强，尽管在最高浓度下观察到刚度饱和。损耗角正切DMTA曲线显示了纯聚丙烯的三个转变。虽然在所有样品中γ弛豫基本保持不变，但由于体系流动性降低，β弛豫温度随CNT含量的增加而升高。γ辐照的PP表现出β弛豫温度升高，这与辐射诱导交联导致的玻璃化转变变化有关。相反，γ辐照的纳米复合材料可能由于辐射自由基与CNT的反应而未显示出这种效应。
