The application of highly filled composites is limited by their poor processing and rheological properties due to the high loading of fillers. One possible solution to this problem is to use maleic ...anhydride grafted polypropylene (MAPP) with high melt index as compatibilizer and lubricant. Herein, magnesium hydroxide (MH)/linear low‐density polyethylene (LLDPE) composites with 60 wt% of MH were prepared using MAPP with three different melt flow indexes (MFI). The equilibrium torque and melt flow index tests show that the addition of MAPP with high MFI significantly improves the processability and flowability of MH/MAPP/LLDPE composites. The rheological studies show that it also leads to a substantial reduction in the viscosity and therefore MH/MAPP/LLDPE composites exhibit more solid‐like responses. The scanning electron microscopy shows that a transition layer is formed at the MH‐LLDPE interface. The flame retardancy test shows that the addition of MAPP slightly reduces the flame retardancy of the composites as evidenced by the reduced limiting oxygen index and increased total heat release. Cone calorimeter test shows that the simultaneous addition of MH and MAPP has a synergistic smoke suppression effect.
Maleic anhydride grafted polypropylene with a high melt flow index not only improves the dispersion of magnesium hydroxide particles in linear low‐density polyethylene matrix, but also acts as a lubricating layer, thus significantly improves the processability and fluidity of highly filled MH/LLDPE composites.
Highly filled composites have received the urgent demands in various areas (i.e., electrical and thermal conductive materials) due to their many advantages (i.e., low cost and high comprehensive ...performance). However, it is challenging to simultaneously improve the processability and toughness of highly filled composites by adding a small amount of flow modifier. In this work, for the first time, a novel silicone/fluorine‐functionalized flow modifier (Si-DPF) with low surface energy is synthesized and incorporated into a highly filled magnesium hydroxide/linear low-density polyethylene (MH/LLDPE) composite (80:20 by weight) to simultaneously improve the processability, toughness and flame retardancy. The results show that Si-DPF is dominantly located at the interface between the MH particles and LLDPE matrix to form a core-shell structure, leading to the relatively homogeneous dispersion of the MH particles. The melt equilibrium torque of the MH/LLDPE composite is decreased by 48.9%, the notched impact strength is increased by more than 4 times, and the area under the stress-strain curves is increased by more than 9 times at 5 wt% loading of Si-DPF. Additionally, the corresponding limited oxygen index (LOI) value is increased to 63.8%. This work provides a facile and effective strategy to simultaneously enhance the processability, toughness and flame retardancy of highly filled polymer-based composites by only one kind of multi-functional flow modifier.
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Acrylonitrile‐butadiene‐styrene (ABS) based composites with a high content of tungsten and bismuth oxide were developed using an innovative process to obtain lead‐free x‐ray shielding materials. ABS ...was chosen for its good mechanical properties and its widespread availability as a recycled material. The composites underwent flexural tests, Shore D hardness tests, thermogravimetric and morphological analysis, and their x‐ray attenuation properties were determined through numerical simulations and experimental measurements. Despite their high filler content (up to 75 wt%), the composites showed good filler dispersion within the polymeric matrix and maintained their mechanical properties. Across the investigated energy range (50–150 kV), the lead equivalence for x‐ray shielding was achieved with composite plates containing 75 wt% of tungsten and bismuth oxide, at thickness values corresponding to a weight increase of only 29% and 36%, respectively, in comparison to lead. These findings pave the way for a new generation of lead‐free x‐ray shielding materials. Moreover, their mechanical properties, including flexibility for potential application in wearable personal protective equipment, can be tailored by adjusting the filler content.
Highlights
High filler content lead‐free ABS composites with WO3 and Bi2O3 were developed.
They show good polymer/filler interfacial adhesion and flexural properties.
Numerical simulations of their x‐ray shielding properties were performed.
Experimental tests with polychromatic sources confirmed good x‐ray attenuation.
Results pave the way for the development of new lead‐free x‐ray shielding systems.
Lead‐free ABS composites containing high amounts of tungsten and bismuth oxide show excellent x‐ray shielding performances
A range of formulations — consisting of high-density polyethylene, surface-coated calcium carbonate, masterbatched carbon black and a stabiliser package — were compared in terms of their thermal ...stability through the use of several techniques and measures. Notably, calcium carbonate loadings of up to 60 wt% were investigated. The formulations were designed to be I- and D-optimal, based on a quadratic Scheffé polynomial model. Novel and established measures for the thermal stability of the materials were compared, based on data generated using techniques for the determination of oxidative induction time and for studies by time-sweep oscillatory rheometry. For ease of comparison, all tests were performed in air. Fourier-transform infrared spectroscopy was performed on the materials subjected to time-sweep oscillatory rheometry, to ascertain the locality and modes of degradation. Variable effects were found, depending on the technique used. Broadly, strong primary effects were found: positive in the cases of the carbon black and stabiliser pack, negative in the case of calcium carbonate. The latter, however, was offset by the highly synergistic interaction of calcium carbonate with the stabiliser pack. Time-sweep oscillatory rheometry was shown to be a promising method, with it yielding high-quality, comparable results when interpreted using a novel measure.
•Common methods ill-suited to comparison of widely varying materials.•Novel time-sweep rheometry measure for stability assessment and comparison.•High loadings of calcium carbonate are detrimental to thermal stability.•Calcium carbonate exhibits a very strong synergy with certain stabilisers.•Calcium carbonate and carbon black have antagonistic effects on thermal stability.
The poor processing and rheological properties of highly filled composites caused by the high loading of fillers can be improved with the use of maleic anhydride grafted polyethylene wax (PEWM) as ...compatibilizer and lubricant. In this study, two PEWMs with different molecular weights were synthesized by melt grafting, and their compositions and grafting degrees were characterized by Fourier transform infrared (FTIR) spectroscopy and acid-base titration. Subsequently, magnesium hydroxide (MH)/linear low-density polyethylene (LLDPE) composites with 60 wt% of MH were prepared using polyethylene wax (PEW) and PEWM, respectively. The equilibrium torque and melt flow index tests indicate that the processability and fluidity of MH/MAPP/LLDPE composites are significantly improved with the addition of PEWM. The addition of PEWM with a lower molecular weight leads to a substantial reduction in viscosity. The mechanical properties are also increased. The limiting oxygen index (LOI) test and cone calorimeter test (CCT) show that both PEW and PEWM have adverse effects on flame retardancy. This study provides a strategy to simultaneously improve the processability and mechanical properties of highly filled composites.
This paper reports on a study of highly filled composites of polypropylene (PP) and 75 and 85% by weight of oil palm mesocarp fiber (OPF) with and without coupling agent, maleic anhydride-grafted ...poly (styrene-ethylene/butadiene styrene) (SEBS-MA) and a maleated polypropylene (MAPP). Composites were prepared using a thermokinetic mixer for blending followed by hot pressing. The thermal and mechanical behavior of these composites was investigated by flexural and impact testing and scanning electron microscopy (SEM). Dynamic mechanical analysis (DMA) was also used to study the properties. The MAPP improve the flexural modulus and flexural strength of the composites with 75 and 85wt% of oil palm fiber while SEBS-MA improved the impact strength of the composites. By SEM it was possible to observe some voids, pull out and debonding in the polypropylene, and allowing the observation of level of adhesion between the fiber and matrix. DMTA showed a decrease in storage modulus when high amounts of fiber were added to polypropylene, however, the presence of the SEBS-MA and MAPP increased the storage modulus. This study looks into the effect of MAH modification on the compatibility of OPF and PP, gives a broad overview of an initial study of these new materials.
Kenaf polypropylene composites with high fiber load of 85 wt% were produced using glycerine as a processing aid and maleic anhydride-grafted polypropylene (MAPP) as a compatibilizer/coupling agent. ...Commercially available MAPPs with different molecular weights and anhydride contents were used to determine what properties of the MAPPs were important to achieve high mechanical properties of these highly filled composites. A homo-polymer and a random-polymer, were compared as matrix polymers. Composites were produced using a high-shear kinetic mixer followed by compression molding at pressures ranging between 345 and 5520 kPa. The data suggests that adding MAPPs with a low molecular weight and high anhydride content at concentrations of 5 wt% resulted in composites with the highest mechanical properties. The authors suggest that a combination of a high surface area, low viscosity and high anhydride content of the MAPP are resulting in a good stress transfer between fibers and matrix polymer.
This paper reports on a study of highly filled composites of polypropylene (PP) and 75% by weight sugarcane bagasse fiber with and without alkali treatment and with and without coupling agent ...(SEBS-g-MA). Composites were prepared using a Rheomix600 mixer connected to a HAAKE torque rheometer. The thermal and mechanical behavior of these composites were investigated by thermogravimetry (TGA), differential Scanning Calorimetry (DSC), flexural tests, impact tests and scanning electron microscopy. Scanning electron microscopy (SEM) images taken from sugarcane bagasse fibers showed enhancements in the fiber's surface topography after the surface treatment process. The FTIR, TGA and SEM results for the fibers showed that the alkali treatment modified the fiber surface as well as the chemical composition. The impact test results showed a good potential of SEBS-g-MA as coupling agent and impact modifier in highly filled composites, increasing by more than 100% the impact strength of the composite as compared to those without the coupling agent. Scanning electron microscopy showed that addition of coupling agent improved the interfacial adhesion between the fibers and polypropylene.
In nature bio-composites such as nacre show remarkable mechanical properties due to their complex hierarchical structure and high-volume fraction of its hard component. These composites are highly ...interesting for structural applications in different branches of industries for mechanical engineering and process technology. The aim of this work was to provide a scalable method for the production of highly filled composites by mimicking the structure of bio-composites. Therefore, composites from iron oxide (Fe2O3) and SBC-polymer (styrene-butadiene block copolymer) were fabricated by using a miniaturized spouted bed with an innovative fluidization gap design. Small iron oxide particles (25–45 μm) were fluidized in the spouted bed and coated with a polymer solution via a bottom spray nozzle. Afterwards the coated granules were hot-pressed and the mechanical properties of the obtained composites were tested. By this method composites with a bending strength of up to 6 MPa were fabricated. Although the mechanical properties of these artificial composites are still lower than those of the natural role models, it was shown that the spouted bed is a suitable technique for the fabrication of highly filled composites. For further optimization of the mechanical properties more complex and tailor-made starting materials will be used in following studies.
Mica is used as reinforcing filler in the polymer industry mainly because of the two-dimensional isotropic nature of reinforcement. Phlogopite and muscovite are under the more common micas with ...phlogopite found in abundance in South Africa. Phlogopite/linear low-density polyethylene (LLDPE) composites containing 20% and less LLDPE were manufactured to yield a composite with an application area similar to wood composites. The outstanding fire, chemical and heat resistance of phlogopite makes it especially suitable for this application. When modified LLDPE is used as a binder in these composites, the bending modulus reaches a maximum (895 MPa) around 15% polymer. This value is obtained when the LLDPE is modified by compounding it with 10% maleic acid anhydride as adhesion promoter and cross-linking agent. Furthermore, modifications to LLDPE that lead to cross-linking enhance the bending modulus of these composites. The optimum yield strength was found to be 11.5 MPa, also at 15% LLDPE modified with 10% maleic acid anhydride. The other LLDPE modifications tested showed that using less maleic acid anhydride, or irradiating the LLDPE before composite manufacture results in a composite with lower yield strength and bending modulus.
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