A facile and easily industrialized approach for preparing highly dispersed MMT/polymer nanocomposites is developed by combining the latex compounding method and a spray‐drying process. Clay particles are successfully delaminated into layers, and layer re‐stacking is effectively prevented. HR‐TEM and XRD results confirm that MMT layers achieve exfoliated or nearly exfoliated dispersion in both MMT/styrene‐butadiene rubber and MMT/PS nanocomposites. Compared with melt‐blended MMT/SBR composites, MMT/SBR nanocomposites prepared by this new strategy exhibit extremely high dynamic modulus.
In this paper, a novel intumescent system including MP as well as PER/TPU which acts as composite charring agent, is adopted to flame‐retarded PP. The encapsulation of charring agent PER by TPU effectively avoids the reaction of PER with MP during the compounding with PP at high temperature and also prevents the leaching out of polar PER from nonpolar PP matrix, thus remarkably enhancing the stability and water‐resistance of the intumescent system. PER and TPU have different but complementary charring mechanisms. So flame‐retarded PP with MP/composite charring agent shows a much better charring performance and flame‐retardancy than MP/PER flame‐retarded PP. The experimental results show that the former can reach UL‐94 V‐0 rating at 1.6 mm thickness at 25 wt.‐% flame retardant loading.
The oxidative degradation of PP/OMMT nanocomposites under γ‐irradiation was studied. Changes in structure and properties resulting from γ‐exposure in the range 0–100 kGy were investigated. The results were analyzed by comparing the influence of PP‐g‐MA and pristine OMMT on the oxidation kinetics of neat PP. γ‐Irradiation in the presence of air strongly degraded the properties of PP materials, particularly for radiation doses above 20 kGy. The rate of oxidative degradation of PP/OMMT/PP‐g‐MA nanocomposites was much faster than that of neat PP. This suggests that PP‐g‐MA and pristine OMMT components behave as oxidation catalysts, leading to the formation of free radicals in the polymer matrix.
A blend composition of poly(3‐hydroxybutyrate‐co‐valerate) and polylactide is used as a bioplastic matrix and reinforced with soy hull to engineer novel green composites. A comparative study with soy‐hull‐reinforced polypropylene composite system is performed. A compatibilizer is used to engineer the novel class of green composites with a balanced stiffness and toughness performance with the target to substitute PP‐based composites. The flexural and impact strength along with hydrophobicity of compatibilized composites are improved significantly over the noncompatibilized counterpart. The fiber/matrix interaction is investigated by SEM. These green composites have the potential to substitute PP‐based composites in some applications.
Fully exfoliated PS/clay nanocomposites were prepared via FRP in dispersion. Na‐MMT clay was pre‐modified using MPTMS before being used in a dispersion polymerization process. The objective of this study was to determine the impact of the clay concentrations on the monomer conversion, the polymer molecular weight, and the morphology and thermal stability of the nanocomposites prepared via dispersion polymerization. DLS and SEM revealed that the particle size decreased and became more uniformly distributed with increasing clay loading. XRD and TEM revealed that nanocomposites at low clay loading yielded exfoliated structures, while intercalated structures were obtained at higher clay loading.
The effect of hydrophilic and hydrophobic nanosilica on the morphological, mechanical and thermal properties of polyamide 6 (PA) and poly(propylene) (PP) blends is investigated by extrusion compounding. Depending on the difference between the polymer/nanoparticle interfacial tensions, different morphologies are obtained as highlighted by TEM and SEM. Hydrophobic nanosilica migrates mainly at the PA/PP interface, which leads to a clear refinement of PP droplet size. The macroscopic properties of the hybrid blends are discussed and interpreted in relation with the blend morphology and melt‐mixing procedure. The control over coalescence allows a morphology refinement of the blends and improves mechanical properties.
A new, nickel‐coated graphite resistance‐change‐based method for gel‐point determination for epoxy‐based thermoset resins is presented and compared with DSC and rheological methods. Gelation times determined by this new method are in very good agreement with conventional techniques; this new method is potentially simpler and less time consuming than existing ones.
A systematic study of the effects of , flow rate, voltage, and composition on the morphology of electrospun PLGA nanofibers is reported. It is shown that changes of voltage and flow rate do not appreciably affect the morphology. However, the of PLGA predominantly determines the formation of bead structures. Uniform electrospun PLGA nanofibers with controllable diameters can be formed through optimization. Further, multi‐walled carbon nanotubes can be incorporated into the PLGA nanofibers, significantly enhancing their tensile strength and elasticity without compromising the uniform morphology. The variable size, porosity, and composition of the nanofibers are essential for their applications in regenerative medicine.
In this study, novel protein/biodegradable polymer blend biomaterials‐gelatin/poly(ethylene oxide) blend films with compositional gradients were successfully fabricated by a dissolution/diffusion method. Two kinds of compositional gradient films, which were different in gradient structure, were prepared. The compositional gradient structure in the films was characterized by polarized optic microscopy, ATR‐FTIR, and trans‐FT‐IR mapping measurement. In addition, the mechanical properties of the gradient films were characterized with reference to their gradient structure. It is found that the compositional gradient films have better mechanical properties than the pure gelatin film. These protein/biodegradable polymer compositional gradient films have a potential for many biomedical applications.
Boehmite alumina nanoparticles are added to PP‐g‐MAH‐compatibilized blends of PA 12 and PP to study the effects of nanoparticle loading in the resulting composites. WAXD and SEM data suggest that the nanoparticles enhanced the coalescence of PP. DSC, DMA, and TGA reveal that the final properties such as crystallization temperature, flexural storage modulus, thermal degradation temperature, etc., improve with increasing nanoparticle loading for blend/based composites. FTIR results show that the nanoparticles interfere with the interfacial activity at 5 wt% nanoparticle loading. All results are compared between the neat polymers and the compatibilized blend and show that despite a slight increase in dispersed‐phase domain size, all other properties improve with the addition of AlO(OH).
Dynamic and start‐up shear flow experiments along with SEM analysis are described for a PP/PET blend compatibilized by two reactive compatibilizers with different interfacial activity and rheological characteristics. The linear viscoelastic behavior of the blends is discussed using Palierne and fractional Zener models (FZMs). The nonzero value of Ge, the elastic modulus of spring element of FZM, is explained by the network‐like structure of the blends attributed to the interconnectivity between dispersed‐phase domains. Ge increases with increasing interfacial activity. Micelle formation due to extra amounts of compatibilizer in a system with higher interfacial activity leads to an increase of the elastic modulus, but to Ge = 0 in system with lower interfacial activity.
This paper presents the first results of a project aimed at investigating the arrangement of polyelectrolyte layers on unalloyed steel. We studied the structure of double and single polymer layers consisting of cellulose phosphate (HP‐PP‐C) and polyethyleneimine (PEI). Layers were characterized by variable angle ellipsometry, AFM and XPS. In particular, XPS indicated the incorporation of iron ions into cellulose phosphate layers, but, in contrast, these ions could not be observed in PEI layers. Results indicated that the homogeneity and qualitative corrosion performance of double layers (HP‐PP‐C/PEI) on unalloyed steel depend on the deposition of cellulose phosphate at the interface with steel.
Two novel cationic RAFT agents, PCDBAB and DCTBAB, were anchored onto MMT clay to yield RAFT‐MMT clays. The RAFT‐MMT clays were then dispersed in styrene where thermal self‐initiation polymerization of styrene to give rise to exfoliated PS/clay nanocomposites occurred. The RAFT agents anchored onto the clay layers successfully controlled the polymerization process resulting in controlled molecular masses and narrow polydispersity indices. The nanocomposites prepared showed enhanced thermal stability, which was a function of the clay loading, clay morphology, and slightly on molecular mass.
This paper demonstrates how the electric‐field‐assisted thermal annealing of octadecylamine‐functionalized SWNT/PMMA films induces an increase in the composite transversal conductivity of several orders of magnitude and a decrease in the lateral conductivity. This difference has been rationalized in terms of the nanotube alignment into the polymer matrix along the electric field direction. This result provides an initial understanding of how electric fields can be used to control the bulk physical properties of such nanocomposites.
PET/PE blends are prepared with and without different types of organo‐modified montmorillonites (OMMT) using a extrusion process. The droplet size of PE dispersed phase decreases upon organoclays addition, however without any direct dependence on the organoclay initial surface tension. To assess the effect of the organomodifier without MMT, PET/PE blends are then compounded adding solely the surfactants (similar to those used to modify the various organoclays). Whatever the chemical nature of the surfactant, a refinement of the PE droplets is observed, interestingly similar to those previously observed in presence of clay. This shows unambiguously that the key factor for organoclay compatibilization efficiency, in the case of PET/PE blends, is the surfactant modifier itself and not the MMT platelets.
Composites containing 50 wt.‐% fly ash in a PP homopolymer were prepared via batch mixing and compression moulding. The following coupling agents were evaluated: Lubrizol Solplus C800, N,N′‐(1,3‐phenylene)dimaleimide, γ‐methacryloxypropyltrimethoxysilane and maleic‐anhydride‐grafted PP. At the filler level investigated, C800 gave the best balance of composite strength and toughness. In the latter case filler‐matrix adhesion appeared weaker relative to γ‐MPS, BMI and m‐PP, all of which gave excessively strong filler‐matrix adhesion leading to a reduction in composite toughness. The unexpected weakness of the C800/fly ash interaction may be related to removal of surface calcium ions from the fly ash via reaction of a single calcium ion with two C800 molecules.
The fractional crystallization kinetics and phase behavior of PEO with different molecular weights (MWs) in its miscible crystalline/crystalline blends with PBS are studied. Both fractional crystallization kinetics and phase segregation of PEO in PBS/PEO blends are dramatically influenced by its MW. PEO with a medium MW (20 kDa) shows a significant fractional crystallization in the blends with PBS crystallized at a high TIC,PBS, which, however, is dramatically depressed in the blends with a very low or high MW of PEO. This indicates that the PEO component with a medium MW is more ready to segregate into the interlamellar region of PBS crystals than those with a very low or high MW. The MW‐dependent fractional crystallization kinetics and phase segregation of PEO component in the PBS/PEO blends are discussed.
The supramolecular structure in pipe walls of isotactic PP‐R is a function of compound composition and processing parameters, which both influence the mechanical properties of the pipes. µFTIR shows a gradient of the crystallinity across the pipe wall, with a lower‐crystalline outer layer, and a higher‐crystalline core layer. The rate of extrusion has an influence on the thickness of the outer layer. The nucleating effect on the morphological profile throughout the pipe wall can be visualised. µFTIR shows a homogeneous distribution of the primary antioxidant in the pipe wall. Both the spectral crystallinity and the antioxidant concentration distribution are calculated.
A simple, easily accessible solvent‐free method for the dispersion of MWCNTs into PET is proposed, based on the preparation of a microparticulate polymer/nanotube masterbatch via cryogenic impact‐milling and its subsequent melt blending with the bulk polymer. Thermal and mechanical properties of nanocomposites prepared using this method were evaluated as a function of nanotube concentration. Thermal stability was improved, and superior crystallization behavior of PET in the nanocomposites was observed. Significant improvements of around 25% in tensile strength and tensile modulus of the nanocomposites was achieved using this strategy, with only 0.25 wt.‐% MWCNT, compared to previous literature data where 1 wt.‐% MWCNT was employed.
Isotactic PP nanocomposites filled with Fe@FeO nanoparticles are fabricated by a facile ex situ method. The nanofillers are dispersed in a boiling PP/xylene solution. X‐ray diffraction is used to determine the nanofiller effects on the crystallinity of PP. The crystallinity along the (040) plane is found to decrease with the incorporation of nanoparticles. Thermal properties and crystallinity are studied by TGA and DSC, respectively. Enhanced thermal stability and influenced crystallinity are observed in the PP nanocomposites compared with those of pure PP. An increased dielectric property without percolation threshold is observed. In addition, the nanocomposites are found to exhibit ferromagnetic properties.
