Volume 35, Issue 2

Copolymerization of pyrrole and aniline was carried out using chemical methods. The synthesis was carried out at different temperatures for different proportions of the monomers. The monomer reactivity ratios for pyrrole and aniline were calculated as 5.2 and 0.19, respectively, by using the low conversion analysis method. In addition, the same was done for two different concentrations of the initiator. The graphs for percentage conversion were plotted for various combinations of temperature, feed ratio and initiator concentration. Thus, an effort was made to study the impact of various parameters on the process of copolymerization.

1,3-Butadiene monomer was polymerized at 40°C and 60°C by means of a catalyst comprising neodymium (Nd) chloride/1-pentanolate/triisobutylaluminum (TIBA) in cyclohexane as solvent; the catalyst system was aged at 5 and 30 min. The effects on conversion, catalytic activity and polymer final properties were evaluated. The obtained polybutadienes (PBs) were characterized by size exclusion chromatography (SEC), nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) techniques and the results were discussed in terms of the effect of aging time and reaction temperature.

In order to obtain flame retardants with good heat resistance, retardant properties and affinity, magnesium hydroxide (MH)/siloxane nanocomposite flame retardants were prepared by the hydrothermal and hypergravity method. The MH and MH/siloxane particles were characterized and analyzed by transmission electron microscopy (TEM), Brunner-Emment-Teller (BET) measurements, thermogravimetric analysis (TGA), etc. The results show that the stability of as-prepared MH/siloxane nanocomposite flame retardants is superior to MH particles prepared by other prepared methods, and the agglomeration is significantly reduced. The specific area of the composite particles was reduced, and the affinity and thermal stability were effectively improved. As a kind of filler for polymer, the MH/siloxane nanocomposite could help to improve the reinforcement of the polymer, and the heat resistant and flame retardant properties, which provide the foundation for further application of this nanocomposite as a flame retardant.

Shoe sole material, design, tread pattern and surface modifications influence slip resistance while walking and running. Thermoplastic styrene-butadine-styrene rubber, commercially known as TPR, is one of the materials widely used as shoe soles. This type of sole is subjected to chemical treatment known as halogenation to increase adhesion characteristic with the upper. The coefficient of friction (COF) is the ratio between the horizontal force and the vertical force when tested with the help of slip resistance test equipment SATRA STM 603. It is also known that footwear outsole surface modification affects COF at the footwear floor interfaces. In this study, plain TPR shoe sole samples were surface modified by treating with 2.0 wt% trichloroisocyanuric acid (TCI) in methyl ethyl ketone (MEK). The effect of surface modifications was studied by water contact angle measurements, Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS), surface roughness and scanning electron microscopy (SEM). The surface modified sole samples were also tested for other mechanical properties such as tensile strength, elongation at break, hardness and abrasion resistance to find out the extent of changes in those essential functional properties. It was observed that surface modification of TPR sole increased COF and reduced strength, elasticity and abrasion resistance properties. However, there was no significant change in hardness.

The effect of curing temperature and layering pattern on mechanical and free vibrational properties (natural frequency and damping) of Sansevieria cylindrica /coconut sheath fiber reinforced hybrid unsaturated polyester (USP) composites is discussed. The hybrid composites were compression molded using different layering sequences. Curing was carried out at different temperatures (30°C and 60°C). The results show that Sansevieria cylindrica /USP composites are stronger than the coconut sheath/USP composites. At higher curing temperatures, a significant improvement in strength was observed in all composites and layering pattern also played a vital role in enhancing composite strength, with coconut sheath/ Sansevieria cylindrica / Sansevieria cylindrica stack yielding a higher strength compared to the other composites. In addition, curing temperature and layering pattern produced a similar effect on the vibrational characteristics of the composites.

Glass fiber (GF) and ultrasound-treated oil palm empty fruit bunch (EFB) were used to prepare recycled polypropylene (RPP)-based hybrid composites through the extrusion and injection molding technique. The ultrasound technique was used to remove the lignin and other surface impurities from the EFB fiber by varying the treatment conditions (treatment time and temperature). A fixed concentration (10%) of NaOH solution was used as the treatment medium. Fiber loading was considered as 40%, while EFB and GF ratio was maintained as 70:30. Two types of coupling agents of maleic anhydride grafted PP (MAPP), Polybond and Fusabond, were used, each of an amount 2.5% (of the total fiber content), to improve the interfacial adhesion between fibers and matrix. Composites were characterized through density, melt flow index (MFI), tensile, flexural and Izod impact testing. In addition, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were also performed to evaluate the thermal and morphological properties, respectively. X-ray diffraction (XRD) analysis was performed to evaluate the crystalline structure of the samples. Finally, water uptake (WU) measurement was performed for 180 days of soaking period. Result analyses revealed improved mechanical, thermal and crystalline properties, with reduced WU as the outcome of treatment and coupling agent effects.

The molybdenum sulfide/lanthanum fluoride/polyimide (MoS 2 /LaF 3 /PI) coating was synthesized and irradiated by ultraviolet (UV) or atomic oxygen (AO). The friction and wear behavior were evaluated sliding against GCr15 steel balls (ASTM A295:1998) using a ball-on-disk tribology test rig. This paper aims to discuss these issues. The chemical structure of the irradiated surface was examined by Fourier transform infrared (FTIR) spectroscopy. The worn morphologies of the coatings and counterpart were observed by scanning electron microscopy (SEM) to reveal the wear mechanism. Experimental results indicated that the height and position of the characteristic functional groups and the coefficient of friction of the PI coating changed and the wear rate value decreased after UV or AO irradiation. The effect of LaF 3 combined with MoS 2 on the tribological properties of the coating and wear mechanism under different irradiated conditions is discussed.

Elastomeric polymers are interesting materials for polymer chemists and other novel material designers in the field of industrial and technological science, because of their physical (mechanical, thermal and electrical) properties. In the context of this study, 35% and 68% styrene-(ethylene-butylene)-styrene (SEBS) containing mixtures, namely SEBS35 and SEBS68, were focused on among of our novel synthesized SEBS blends which compose of microstructures. The structural changes, globular contents (globules) and uniformities of the samples at nanoscale and microscale were investigated by small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) methods. The obtained structural results were compared with a calculation of the scattering profiles using a convenient geometrical model defined by lamellar ordered and elliptical polydispersed cylindrical globules, which have approximately the same lengths in the range of 203.6–205.2 nm. Separation lengths and wide distributions of the cylindrical globules with elliptic cross sections and their lamellar stackings were also determined. At the end of the study, it was indicated that the microstructures of these newly designed polymers may be described by fractal structures composed of polydisperse elliptical cylinders.

The effects of UV irradiation and blending on the stability of poly (α-methylstyrene) (PαMS) in solid films were studied at different intervals of irradiation time in the presence of air, by absorption, emission and Fourier transform infrared (FT-IR) spectroscopy. The increase in irradiation time caused an increase in the intensity of the absorption band of the polymer, and an increase in the intensity of absorption of a new broad band at a longer wavelength, thus indicating the possibility of photodegradation of polymeric chains. The influence of added plasticizers, dimethyl terephthalate (DMT), diethyl terephthalate (DET), dibutyl phthalate (DBP), dioctyl phthalate (DOP) and dioctyl terephthalate (DOT) on photoquenching of the polymer fluorescence band was also investigated, and found to increase the photoquenching processes with increase in the amount of added plasticizers. By contrast, the intensity of excimer and monomer fluorescence bands was also found to decrease with increase in irradiation times. These changes may be attributed to the formation of new photoproducts which resulted from the photodegradation and photooxidation of irradiated polymeric chains. In addition, the observed increase in the intensities of the carbonyl and hydroxyl regions of the FT-IR spectra provides evidence for the photooxidation of polymeric chains. The increase in the intensity of some bands and the disappearance of new bands indicate the photodegradation of polymeric chains.

In industry, rapid crystallization is often required. At present, the crystallization rate of poly(lactic acid) (PLA) is too low compared to industrial needs. In this paper, amino acids such as glycine and L-alanine and poly(amino acids) like polyglycine and poly-DL-alanine are considered as heterogeneous crystallization nucleating agents. The impact of adding these bio-based additives on the isothermal crystallization behavior of PLA was quantified and compared at different concentrations by using the so-called Lotz efficiency scale, which here is based on isothermal DSC measurements. In addition, rheological and rheo-optical techniques were used to monitor the isothermal crystallization. Our results indicate that polyglycine possesses a significant nucleating ability (60.5%) which is comparable to the industrially used talc (81.1%).

Poly (vinylidene fluoride) (PVDF)-untreated clay nanocomposites were successfully prepared using an innovative one-step reactive melt extrusion process. Through specific temperature and shear conditions, the chemical reactions took place between the polymer matrix, the inorganic clay particles, and three main reactive agents: an organic peroxide, sulfur, and a specific activator led finally to the PVDF-clay nanocomposites. The materials were formulated with various amounts of clay in order to identify the best conditions, enabling to obtain the optimal particle exfoliation in the polymer matrix at the nanometric scale. The microstructure and nanostructure modifications were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and wide- and small-angle X-ray scattering (WAXS and SAXS). The relationship between nanostructure and mechanical behavior was investigated by tensile experiments, impact tests, and microhardness measurements. The FTIR results suggest that there is a chemical interaction between the clay and the polymer. Furthermore, the WAXS study shows that no intercalation step takes place in any composition. In addition to this, the sample with 2.5 wt.% clay could present a total exfoliation of the clay particles. The PVDF matrix is found to be exclusively of the α-form in all compositions. The final microhardness slightly increases with both nanoclay content and degree of crystallinity.

The work presents the results of experimental studies of plasticized poly(vinyl chloride) (PVC) extruded by a single-screw extruder with a modified feed section. The variable factors were the feed opening width, the feed pocket depth in the extruder barrel, and the rotational speed of the screw. The following parameters were studied: extrudate temperature T w (°C), screw torque M (Nm), polymer mass flow rate G (kg/h), unit consumption of energy supplied to the extruder E jc (J/g), and extrusion process energy efficiency κ (%). It was found that the increase in the depth of the pocket and the decrease in the width of the feed opening influence the extrusion process in a positive way.