Search results for "polymers"

Progressive cracking mastercurves of the transverse ply in a laminate

2009

In this study, progressive cracking of a transverse layer in a cross-ply composite laminate subjected to tensile loading is considered. Using the results of a probabilistic cracking model, approximate relations for crack density as a function of stress are derived for initiation-controlled and propagation-controlled cracking. It is shown that the crack density evolution in the transverse ply can be represented by a mastercurve in suitably normalized coordinates. The mastercurve approach is applied to progressive cracking in glass/epoxy laminates. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Effect of glass fiber hybridization on the durability in salt-fog environment of pinned flax composites

2021

The aim of the present paper is to evaluate the effect of the hybridization with external layers of glass fibers on the durability of flax fiber reinforced composites in severe aging conditions. To this scope, full glass, full flax and hybrid glass–flax pinned laminates were exposed to a salt-fog environment for up to 60 days. Double-lap pinned joint tests were performed to assess the pin-hole joints performances at varying the laminate stacking sequence. In order to better discriminate the relationship between the mechanical behavior and the fracture mechanisms of joints at increasing the aging time, different geometries (i.e., by varying both the hole diameter D and the free edge distance…

Dynamics of self-healing supramolecular guanine-modified poly(n-butyl methacrylate-co-hydroxyethyl methacrylate) copolymers

2020

Abstract Self-healing is a nature-inspired characteristic that is imparted in synthetic polymeric materials through the integration of reversible supramolecular bonds following different design concepts. Generally, the dynamics of supramolecular bonds regulates timescale of the self-healing process, specifically in polymeric systems with a homogeneous morphology. Herein, we explore the utility of guanine as a hydrogen bonding group to construct supramolecular polymeric systems based on poly (n-butyl methacrylate). For this purpose, we follow a three-step reaction approach, including a living radical copolymerization, deprotection of the functional comonomer, and grafting of the guanine grou…

Infrared spectroscopy on new multiphase thermoplastic elastomers based on hydrogen bond complexes - temperature dependence and orientation behaviour

1991

The structure and deformation behaviour of a new class of thermoplastic elastomers is studied by temperature dependent infrared (IR) spectroscopy and by IR - dichroism spectroscopy. The thermoplastic elastomer is based on polybutadiene with statistically distributed side groups which form an anisotropic supramolecular structure via hydrogen bonds. Changes in the IR spectra at elevated temperatures are related to the melting of the ordered structure. The uniaxial deformation behaviour is studied by linear dichroism Fourier-transform (FT)-IR spectroscopy. A deformation model is developed which accounts for the major experimental results: while the polybutadiene segments behave as flexible cha…

Blends of polyamide 6 and linear low density polyethylene functionalized with methacrylic acid derivatives

1997

Abstract Morphological, calorimetric, rheological, dielectric and mechanical behaviour of blends made with polyamide 6 (PA6) and linear low density polyethylene (PE) are presented. The PE was functionalized grafting ester and alcohol groups in a Brabender mixer with methacrylic acid derivatives. These groups induce “compatibilization” effects in the blends with respect to blends made with the unfunctionalized polyethylene. The difference effects on the behaviour of the blends of the various functional groups are shown. In particular, the interactions at the interface change depending on the chemical nature of the grafted groups. Ethyl and isobuthyl-methacrylate essentially cause dipolar int…

Long-term ISO 23936-2 sweet oil ageing of HNBR

2021

Abstract A hydrogenated nitrile butadiene rubber (HNBR) compound is subjected to ageing in a simulated oil and gas environment in accordance with ISO 23936-2 standard at two elevated temperatures (130 °C and 150 °C) for a period of up to 9 months. Shore D hardness, thermal expansion, dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) spectroscopy, compression and compression set (CS) measurements are made before and after the chemical exposure. The hardness, modulus at short times, degree of relaxation and CS increases while the coefficient of thermal expansion in HNBR tends to decrease with ageing time and temperature. Temperature is shown to impose a greater effect on th…

Relating morphology to nanoscale mechanical properties: from crystalline to mesomorphic iPP

2005

Abstract A nanoindentation technique using an atomic force microscope (AFM) was applied to characterize the mechanical behaviour of several isotactic polypropylene (iPP) samples. The samples were solidified from the melt with a CCT (continuous cooling transformation) procedure spanning a wide range of cooling rates thanks to a fast quenching apparatus developed by the authors. The influence of instrumental parameters on the nanoscale mechanical properties (indentation depth, Young's modulus) shows that for modulus determination one has to rely on simpler methods of force curve analysis based on trace curve alone. Structure homogeneity up to the scale of macroscopic samples used to evaluate …

Photochemical stabilization of linear low-density polyethylene/clay nanocomposites: Towards durable nanocomposites

2008

International audience; This article reports a study of the chemical modifications of LLDPE/nanoblend nanocomposites exposed to UV light in conditions of artificially accelerated ageing and natural weathering. Analysis by infrared spectroscopy of the chemical modifications produced by photoageing shows that the presence of an organo-clay leads to the decrease of the oxidation induction time of the polymer (LLDPE), which results in lower durability of the nanocomposites. Protection against photooxidation was tested with different kinds of UV stabilizers and with a metal deactivator. It is shown that the metal deactivator is very efficient in stabilizing the nanocomposite since it totally can…

Oscillatory interaction between two like‐charged nanoparticles induced by polyelectrolyte brush–solvent interface

2016

Reprocessing of PLA/graphene nanoplatelets nanocomposites

2017

This work reports a study on the effect of multiple reprocessing on the properties of poly(lactic acid) (PLA) filled with graphene nanoplatelets (GnP) compared to the melt reprocessed neat polymeric matrix. In particular, morphological, X-Ray Diffraction and Micro-Raman analyses, intrinsic viscosity measurements, thermal, rheological and mechanical tests were carried out on materials reprocessed up five times by means of a single screw extruder. The results indicated that the presence of GnP decreased the degradation rate as a function of the reprocessing cycles in comparison with the neat PLA that, on the contrary, showed a more drastic reduction of the molecular weight. Moreover, the repr…