Fawaz Deri

Thermoplastic starch blends: A review of recent works

The aim of this review is to discuss the recent developments in thermoplastic starch blends. Starch has been considered as an excellent candidate to partially substitute synthetic polymer in packaging, agricultural mulch and other low-cost applications. Recently, the starch granules were plasticized using different plasticizers under heating and shearing, giving rise to a continues phase in the form of a viscous melt which can be processed using traditional plastic processing techniques, such as injection molding and extrusion. This kind of starch composites is called thermoplastic starch. Unfortunately, thermoplastic starch presents some drawbacks, such as low degradation temperatures, which make it difficult to process, poor mechanical properties and high water susceptibility. Much work has been carried out to overcome these drawbacks, including the combination of thermoplastic starch with other polymers, aiming at lowering the cost and enhancing the biodegradability of the final product.

Biodegradable polymer blends and composites: An overview

Biodegradable polymers belong to a family of polymer materials that found applications ranged from medical applications including tissue engineering, wound management, drugs delivery, and orthopedic devices, to packaging and films applications. For broadening their potential applications, biodegradable polymers are modified utilizing several methods such as blending and composites forming, which lead to new materials with unique properties including high performance, low cost, and good processability. This paper reviews the recent information about the morphology of blends consisting of both biodegradable and non-biodegradable polymers and associated mechanical, rheological, and thermal properties of these systems as well as their degradation behavior. In addition, the mechanical performance of composites based on biodegradable polymers is described.

Rheological and mechanical properties of polypropylene/thermoplastic starch blend

Starch as an inexpensive and renewable source has been used as a filler for environmentally friendly plastics for about two decades. In order to improve the compatibility between hydrophilic starch granules and hydrophobic polypropylene (PP), glycerol used as a plasticizer for starch to enhance the dispersion and the interfacial affinity in thermoplastic starch (TPS)/PP blend. In this study, PP was melt blended with thermoplastic starch (TPS) using a single screw extrusion process and molded using injection molding process to investigate the rheological and mechanical properties of these blends. TPS viscosity measurements were performed on the single screw extruder. Rheological properties were studied using a capillary rheometer and the Bagley’s correction was performed. Mechanical analysis (stress–strain) was performed using Testometric M350-10KN. The rheological properties showed that the viscosity of TPS decreases with increasing glycerol content in TPS. Also, it was found that PP/TPS blends are pseudo plastic in nature and the flow activation energy of the blends is greater than that of PP. Mechanical results showed that strain at break of the blends is lower than that of PP, whereas the Young’s modulus of the blends is higher than that of PP.

On-Line Rheological Measurements and Mechanical Properties of Acrylonitrile-Butadiene-styrene/Corn Starch Composite

In this work, rheological and mechanical properties of acrylonitrile–butadiene–styrene/corn starch composites (ABS/starch) were studied. The composites were prepared using a laboratory-scale, single-screw extruder. Rheological properties were determined using the single-screw extruder, apparent shear rate (γ a ), apparent shear stress (τ a ), apparent viscosity (η a ), non-Newtonian index (n), and flow activation energy at a constant shear rate (E γ) and constant shear stress (E τ). Mechanical properties in terms of tensile tests were performed using Testometric M350-10KN, stress at break, strain at break, and Youngs modulus were determined. Rheological results showed that the composites are pseudo plastic in behavior, and the apparent viscosity of the composites increases with increasing starch content above the additive rule, which indicates a partial compatibility in the composite. It was also found that the flow activation energy of the composite increases with increasing starch content. The mechanical results showed that the strain at break of the composite decreases sharply by the presence of starch, whereas the Youngs modulus increases with increasing starch content.

Preparation and studying properties of thermoplastic starch/acrylonitrile–butadiene–styrene blend

In this work, blends of acrylonitrile–butadiene–styrene (ABS) and thermoplastic starch (TPS) were prepared by using a single screw extruder (SSE), the starch was plasticized in the single screw extruder by using glycerol as a plasticizer. The blends were characterized by studying rheological and mechanical properties. The rheological results indicated that ABS/TPS blend melts were pseudo plastic and exhibited shear–thinning behavior, and the viscosity of the blend decreased with increasing glycerol content. Also the values of flow activation energy at a constant shear stress (Eτ) of ABS1/TPS25G blend were determined, and it was found that Eτ increased with increasing shear stress. Die swell measurements of the blend showed that die swell ratio increases with increasing shear stress and glycerol content in the blend, while it decreases with increasing L/R. Mechanical results showed that, the values of stress at break and strain at break decreased with increasing TPS content in the blend, which was attributed to the immiscibility between TPS and ABS.

A review on recent researches on polylactic acid/carbon nanotube composites

As multifunctional high-performance materials, polylactic acid/carbon nanotube (PLA/CNT) composites are currently of great interest for using in an extensive range of medical and industrial applications. The main focus of the present work, accordingly, is to review the recent developments on PLA/CNT composites. In addition, the dependence of thermal, mechanical, electrical, and rheological properties on the type, aspect ratio, loading, dispersion state, and alignment of CNTs within PLA matrix was reviewed. The discussion of the different properties revealed that the CNTs additive could be an effective method to improve the performance of PLA materials for medical and industrial applications.

Melt rheology of poly(vinylidene fluoride) (PVDF)/low density polyethylene (LDPE) blends

The aim of this work is to study the rheological properties of PVDF/LDPE blends in the molten state, in relation to shear rate, shear stress and temperature. Blends of LDPE and PVDF at different compositions, namely PVDF/LDPE = 0/100, 30/70, 50/50, 70/30, 100/0 were realized. The blends were prepared by using brabender plastograph and measurements were carried out by using capillary rheometer. For studying the viscous properties non-Newtonian index n, true viscosity η and the flow activation energy E were determined. The melt elasticity has been studied in term of die swell ratio B. The results show that PVDF/LDPE blends behave in pseudo-plastic manner (n < 1), plots of true viscosity versus blending ratio go through a minimum nearly at blending ratio (50/50), and the flow activation energy decreases with increasing shear rate at the wall γ but it increases with increasing true shear stress τ. The results of die swell ratio show that, B increases linearly with increasing true shear stress τ, while B decreases with increasing L/R. It was also found that a maximum of elastic properties is observed at certain blending ratio. This phenomenon can be attributed to the amount of elastic deformation energy stored in the melt flow and its transition due to the viscoelastic difference between the two phases.

Material properties of polyethylene/wood composites: A review of recent works

Polyethylene/wood composites have attracted considerable attention in research and industry due to several advantages including biodegradability, low density, low cost, high stiffness, availability of renewable natural resources. This paper reviews the recent progress on thermal, rheological, and mechanical properties as well as degradation behavior of polyethylene/wood composites. In addition, fire properties and water resistance of the composites are introduced. The potential applications of polyethylene/wood composites are also highlighted. The discussion of the different properties showed that the wood additives can be an effective method to improve the performance of polyethylene materials for industrial applications.

Effect of Wood Fibers on the Rheological and Mechanical Properties of Polystyrene/Wood Composites

The effects of wood fibers on the rheological and mechanical properties of polystyrene/wood (PS/wood) composites were investigated. The composites with different ratios of PS and wood were prepared by means of internal mixer and, additionally, two different sizes of the wood particles were used, such as ∼100 and ∼600 µm. The rheological properties were studied using capillary rheometer, apparent shear rate, apparent shear stress, apparent viscosity, power law index, and flow activation energy at a constant shear stress were determined. The rheological results showed that the shear stress–shear rate variations obeyed a power law equation, and the composites exhibited shear thinning. The flow activation energy of the composites increased with the addition of wood particles. Mechanical results showed that stress at break of the composites was higher than that of pure PS, whereas the strain at break and impact strength of the composites were lower than that of PS. In addition, the mechanical properties of the present composites were improved when the small size of wood particles were incorporated.