Modification of cellulose acetate films using nanofillers based on organoclays

The present work has been oriented on the development of cellulose acetate films with nanofillers of montmorillonite/alkylammonium (hexa- and tetra-decyltrimethylammonium) and montmorillonite/chitosan which have been synthesized using a cationic exchange process. All synthesized organoclays have been characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). These analyses confirmed the modification of clay structures which proved to be dependent on the chemical structure of chosen organic precursor. On the other hand, the different organoclays have been used to produce cellulose acetate nanocomposites by solvent-casting technique. The nanocomposite films have been characterized by XRD, TGA, Differential scanning calorimetry (DSC), oxygen and water vapor permeability and scanning electronic microscopy (SEM). All nanocomposites obtained showed the intercalation of polymer inside the clay structure and an important reduction of oxygen transmission rate (OTR) compared to cellulose acetate films without nanofillers.     

A starch/milled‐montmorillonite nanocomposite for warp sizing

Na‐montmorillonite (Na‐MMT) was ball‐milled, and a starch/MMT nanocomposite for warp sizing was prepared by solution intercalating technique, with oxidized corn starch (OS) of concentration 6 wt% and the Na‐MMT of 5 wt% on the basis of dry OS. Scanning electron microscope and laser particle size analyzer were used to investigate the particle morphology and size distribution of the MMT. The interlamellar spacing of the MMT and crystal structure the OS‐based composite film were analyzed by using XRD. The sizing performances of the nanocomposite were also tested. All of the experiments conducted, together with those of the OS alone and OS/unmilled MMT for comparison. The results revealed that the ball‐milling treatment resulted in a smaller partical size with a narrow distribution, and larger interlamellar spacing of the Na‐MMT. In comparison with the pristine clay, the milled MMT restrained the crystallization of OS to a greater extent as composited into the OS, had more decrease effects on apparent viscosity of OS paste and hygroscopicity of the casting films, and had more improvement effects on the tensile properties of OS films and adhesiveness of sizes to fibers.     

A constitutive model for finite deformation response of layered polyurethane-montmorillonite nanocomposites

A constitutive model is developed to predict the finite deformation response of multilayered polyurethane (PU)-montmorillonite (MTM) nanocomposites. In PU-MTM nanocomposites, the PU matrix in the vicinity of the MTM nanoparticles is modified leading to an interphase region, and its effect on the finite deformation response of these nanocomposites is largely neglected in many existing models. In this work, the entire spatial volume is considered to be occupied by multi-layers of bulk PU and effective particles which consist of MTM nanoparticles and the modified PU interphase region. A Langevin chain based eight chain model is used to capture the large stretch hyperelastic behavior of bulk PU. The effective particle component of the model consists of a linear elastic spring to capture the initial elastic response, a non-linear viscoplastic dash-pot for the strain-rate dependent yield strength of nanocomposites, and a non-linear spring element in parallel to the dash-pot for the strain-hardening response. The model adopts the concept of amplified strain of the confined PU chains to accommodate the applied strain owing to the limited strain in the MTM nanoparticles. The constitutive model predicts all the major features of the stress-strain constitutive response of a family of PU-MTM nanocomposites including the initial linear elastic response, yield strength and post yield strain hardening for all volume fractions of MTM nanoparticles, thus confirming the efficacy of the proposed constitutive model.     

蒙脱石粘土／水分散体系中颗粒的性质

在实验测定了蒙脱石粘土／水分散体系中颗粒的比表面积，ζ电位及颗粒粒度的分布的基础上，研究了粘土颗粒在分散体系中的聚焦状态，颗粒结构以及颗粒的表面性质，为研究粘土分散体系的稳定与聚深以及体系性质提供参考。