Preparation of green montmorillonite/carbon nanotubes hybrid by lyophilization procedure for poly(lactic acid) nanocomposite

International audienceMontmorillonite (MMT) and multi-walled carbon nanotube (MWCNT) are presently the leading and most effective studied nanofillers reported to impact high properties in various polymeric matrices. Meanwhile, the main challenge in nanocomposite is achieving efficient dispersion of these nanoparticles without agglomeration in the selected matrix. In this study, we investigated the influence of various types of montmorillonite and carbon nanotubes in determining the most stable MMT/MWCNT hybrid formulation, and the optimum mixing ratio of the two fillers was selected to prepare MMT/MWCNT hybrid via lyophilization process. Three kinds of nanoclays (Cloisite MMT Na+, MMT 10A and MMT 20A) and two types of MWCNT (pristine MWCNT and functionalized MWCNT "MWCNT-f") have been investigated. The most stable and optimum MMT/MWCNT hybrid was incorporated into poly(lactic acid) (PLA) matrix. The various characterization results revealed the success of the lyophilization procedure, and that the prepared MMT/MWCNT hybrid influenced high properties in the nanocomposites

How to Identify and Prioritize Psychosocial Factors Impacting Stress Level

<div><p>We develop a methodological approach to identify and prioritize psychosocial factors (stressors) requiring priority action to reduce stress levels. Data analysis was carried out on a random sample of 10 000 French employees who completed, during a routine interview with the occupational physician, a 25-item questionnaire about stress levels, as well as a questionnaire about 58 stressors grouped into 5 latent variables: job control, job context, relationships at work, tasks performed and recognition. Our method combines Importance-Performance Analysis, a valuable approach for prioritizing improvements in the quality of services, with Partial Least Squares-Path modeling, a Structural Equation Modeling approach widely applied in psychosocial research. Findings on our data suggest two areas worthy of attention: one with five stressors on which decision makers should concentrate, and another with five stressors that managers should leave alone when acting to reduce stress levels. We show that IPA is robust when answers to questions are dichotomized, as opposed to the initial 6-point Likert scale. We believe that our approach will be a useful tool for experts and decision-makers in the field of stress management and prevention.</p></div

Illustration of variation in stress level y for 2 different stressors x₁ and x_2.

<p>Illustration of variation in stress level y for 2 different stressors x₁ and x_2.</p

IPA grid for the 58 stressors coded on a 6-point Likert scale.

<p>IPA grid for the 58 stressors coded on a 6-point Likert scale.</p

Correlations between latent variables (N = 10 000).

<p>Correlations between latent variables (N = 10 000).</p

Conceptual model for stressors and work-related stress.

<p>Conceptual model for stressors and work-related stress.</p

First eigenvalue for each latent variable and Cronbach's α (N = 10 000).

<p>First eigenvalue for each latent variable and Cronbach's α (N = 10 000).</p

Path coefficients and contributions of each block of stressors to the stress block: β (R²).

<p>Path coefficients and contributions of each block of stressors to the stress block: β (R²).</p