Volume 33, Issue 7

In the present study, linear low density polyethylene (LLDPE)/soya powder blends were compatibilized with epoxidized natural rubber (ENR 50) and exposed to natural weathering. The exposure period for the blends was 1 year. It was found that the degradability of the compatibilized blends was higher than that of uncompatibilized blends. Fourier transform infrared (FTIR) spectra, the tensile test, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) were applied to analyze the degradability of the blends. IR spectra showed that the carbonyl index (CI) of the blends increased as a function of exposure period and soya powder content. The compatibilized blends gave higher carbonyl indices. The retention tensile strength and elongation at break (E b ) of the compatibilized blends after weathering was generally lower than for the uncompatibilized blends. The increase of crystallinity also indicated a reduction of the amorphous portion after degradation. The higher crystallinity in compatibilized blends further confirms the higher degradability of ENR 50 compatibilized blends. The weight loss and molecular weight change indicated that the incorporation of ENR 50 into LLDPE/soya powder blends can enhance the degradability of the blends upon outdoor exposure.

Blends of isotactic polypropylene (iPP) and high density polyethylene (HDPE), with and without compatibilizers and with different organoclay amounts (1%, 3%, and 5%), were systematically investigated to assess the effect of the additives on the crystallinity of the blends, as well as the correlation between the microhardness, H and the Young’s modulus E . The compatibilizers used were: maleic anhydride grafted styrene ethylene butadiene styrene (SEBS-g-MAH), maleic anhydride grafted polyethylene (PE-g-MAH), maleic anhydride grafted polypropylene (PP-g-MAH), ethylene propylene diene monomer (EPDM), and maleic anhydride grafted EPDM (EPDM-g-MAH). The thermal properties and crystallization behavior were determined by differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS). Macro- and micromechanical properties were also investigated. The results obtained showed that the addition of clay slightly increases the crystallinity α WAXS of the blends. However, the hardness H decreases enormously only by adding 1 wt% of clay. With higher clay amounts, H increases again. The relationship between the Young’s modulus E and the hardness H for all the studied blends was found to be somewhat higher than the one obtained for polyethylene (PE) samples with different morphologies.

Blends of ultrahigh molecular weight polyethylene (UHMWPE) with high-density polyethylene (HDPE) provide adequate mechanical properties for biomedical application. In this study, the mechanical and thermal properties of UHMWPE/HDPE blends with the addition of polyethylene glycol (PEG) prepared via single-screw extruder nanomixer were investigated. The UHMWPE/HDPE blends exhibit a gradual increase in strength, modulus, and impact strength over pure polymers, suggesting synergism in the polymer blends. The elastic and flexural modulus was increased at the expense of tensile, flexural, and impact strength for the blends containing PEG. The degradation temperature of UHMWPE was improved with the incorporation of HDPE due to good thermal stability of HDPE. HDPE improved the dispersibility of PEG in matrix, consequently reduced the surface area available for the kinetic effects, and reduced the degradation temperature. The morphology analysis confirmed the miscibility between UHMWPE and HDPE and the changes in polymer structure with the presence of PEG modify the thermal behavior of the blends. The mechanical properties of the blends that are underlying values for the design of implant material show the potential used as biomedical devices.

The objective of this research is to investigate the effect of incorporating montmorillonite (MMT) on the mechanical, morphological, rheological, and thermal properties of recycled poly(ethylene terephthalate) (rPET) and high-density polyethylene (HDPE) nanocomposites. The MMT contents in 90:10 rPET/HDPE and 70:30 rPET/HDPE ranged from 1 to 5 wt.%. rPET/HDPE nanocomposites were prepared by using a single screw extruder, and injection molded to prepare mechanical test specimens. The samples underwent rheological tests by using a capillary rheometer, and the morphology of the nanocomposites was investigated by scanning electron microscopy (SEM). The thermal stability of the nanocomposites was tested using thermogravimetric analysis (TGA). The results showed that MMT acts as compatibilizing agent and improves phase dispersion and interfacial adhesion in the nanocomposites. The maximum tensile strength was found at 3 and 1 wt.% of MMT for the 90:10 and 70:30 rPET/HDPE blends. However, the tensile modulus decreased significantly with the incorporation of MMT. The impact strength for both the 90:10 and 70:30 blends reached a maximum at 3 wt.% and started to decrease beyond 3 wt.%. The incorporation of MMT increased the shear viscosity of the 90:10 and 70:30 blends, which reached a maximum value at 3 and 1 wt.%. SEM micrographs showed a good interaction of MMT that improved the adhesion between the two phases of blends and led to an increase in the mechanical properties of rPET/HDPE nanocomposites.

A three-dimensional viscoelastic numerical simulation was developed for a two-layer coextrusion through a rectangular channel by using the finite element method. The Phan-Thien and Tanner model was considered as viscoelastic constitutive equations. The generalized Navier’s law was adopted to found the slip boundary condition. The numerical results of the effects of the wall slip coefficient and the flow rate on the interface profile and the degree of encapsulation were compared with the experimental results of previous researchers. It was found that the interfacial offset and the degree of encapsulation increased with the increase of the wall slip coefficient and the flow rate, and the growing rate was large when the wall slip coefficient was between 10 6 and 10 8 . We were able to control the interface shape and the degree of encapsulation at the die exit by varying the wall slip coefficient and the magnitude of the melt flow rate.

Thin films of poly (vinyl chloride) (PVC)/poly (methyl methacrylate) (PMMA) blend polymers complexed with different concentrations of LiClO 4 salt, containing ethylene carbonate (EC) as the plasticizer, were fabricated by the solution cast procedure. Ionic conductivity, thermal stability and X-ray diffraction (XRD) studies were undertaken. AC impedance measurements were done in the temperature range of 20–70°C. The highest ionic conductivity at room temperature was found to be 2.23×10 -5 S cm -1 for the sample containing 15 wt% of LiClO 4 salt. The XRD technique was used to investigate the structure and complex formation of solid polymer electrolytes. There was a decrease in degree of crystallinity. The amorphous nature of complexed solid polymer blend electrolyte films increased, due to the addition of LiClO 4 salt. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) revealed the effect of salt on the thermal stability of the polymer electrolytes. It was found that these polymer electrolyte systems show stability up to about 280°C. It was also found that, with increased LiClO 4 salt content in complexed polymer electrolyte systems, the degradation temperature decreased.

The influence of chill roll temperature and thermal annealing on the morphology and dynamic mechanical behavior of poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA)/titanium dioxide blend films prepared by a melt casting process was studied. The β phase of PVDF was formed at the chill roll temperature of 30°C. Furthermore, with the increase in this chill roll temperature, its structural conversion to the α phase was observed. No change in the crystal structure of either the β or α phase occurred on account of thermal annealing at 115°C for 24 h. The decrement in the storage modulus above the glass transition temperature ascribed to the mixed amorphous phase became smaller, as the chill roll temperature increased. Based on morphological observations, we deduced that the reason for this decrement is not that the film cast at 115°C was more crystalline than that cast at 30°C but that the actual weight fraction of PMMA in the mixed amorphous phase of the film cast at 115°C was lower than that of the one cast at 30°C.

The effects of the addition different fillers, such as calcium stearate (CS), aluminum trihydrate (ATH), and magnesium hydroxide (MH), on the properties of low-density polyethylene/ethylene vinyl acetate (LDPE/EVA) compounds were studied. It was determined that the adhesion forces among MH and LDPE/EVA compounds were stronger than those among analogue compounds containing ATH in each irradiated sample. The gel content (GC) values of irradiated compounds containing ATH were higher than those of the analogue MH compounds, and CS addition enhanced the GC values of all compounds in each irradiated sample. The density values of compounds with MH content were higher than those of analogue compounds containing ATH in each irradiated sample. It was shown that all pristine compounds whose density was compared with irradiated samples had maximum values. Addition of CS and enhancing irradiation to polymer compounds reduced the density values. Compounds with high CS contents and were highly irradiated showed high tensile strength (TS) values. The TS values of compounds containing ATH were lower than those of analogue compounds containing MH in each irradiated sample. ATH or MH addition to polymer matrices reduced the elongation at break (EB) values in each irradiated sample. The EB values of compounds containing ATH were higher than those of compounds containing MH in each irradiation range. CS addition improved polymer chain flexibility and enhanced the compounds’ EB values with irradiation.

A biodegradable local drug release system consisting of poly(sebacic anhydride) and polylactic acid was developed for the purpose of osteomyelitis therapy. Five kinds of poly(sebacic anhydride) with different molecular weights were synthesized, and levofloxacin was chosen as a model antibacterial drug in the in vitro release within 38 days. As the molecular weight of poly(sebacic anhydride) increased, the melting point (Tm) of the matrices increased and the surface morphology became smoother. Consequently, the initial burst effect was reduced and the release rate significantly decreased. In addition, the kinetics of pills containing poly(sebacic anhydride) (Mw=13,000) were close to zero order release. The release profile reveals that the thermodynamic properties and morphology of these matrices, which are affected by the molecular weight, are essential for developing controllable delivery systems. The drug release rate could be easily controlled by the molecular weight of the poly(sebacic anhydride). Finally, these prospective results allow the biodegradable controlled release systems to be employed as carriers for the treatment of chronic osteomyelitis, as well as for other medical applications.

Surface modification of natural fiber may greatly enhance the mechanical interlocking between fiber and matrix. Although there are many reports on surface modification of natural fibers, little technical information is available to enable the selection of optimized surface modification conditions. In this work, treatment parameters, such as bath temperature, agent concentration, and treatment time, are optimized to achieve higher interfacial adhesion. The effect of these parameters on flexural and impact strength is investigated by applying gray relational techniques. Experimental results show that NaOH concentration and treatment time are significant variables which improve interfacial strength, while NaOH bath temperature appears less important.