Volume 30, Issue 2

Multilayer coextrusion is applied to produce a tape containing layers of alternating electrical properties to demonstrate the potential for using coextrusion to manufacture capacitors. To obtain the desired properties, we develop two filled polymer systems, one for conductive layers and one for dielectric layers. We describe numerical models used to help determine the material and processing parameters that impact processing and layer stability. These models help quantify the critical ratios of densities and viscosities of the two layers to maintain stable layers, as well as the effect of increasing the flow rate of one of the two materials. The conducting polymer is based on polystyrene filled with a blend of low-melting-point eutectic metal and nickel particulate filler, as described by Mrozek et al. (2010). The appropriate concentrations of fillers are determined by balancing measured conductivity with processability in a twin screw extruder. Based on results of the numerical models and estimates of the viscosity of emulsions and suspensions, a dielectric layer composed of polystyrene filled with barium titanate is formulated. Despite the fact that the density of the dielectric filler is less than the metallic filler of the conductive phase, as well as rheological measurements that later showed that the dielectric formulation is not an ideal match to the viscosity of the conductive material, the two materials can be successfully coextruded if the flow rates of the two materials are not identical. A measurable capacitance of the layered structure is obtained.

There exists an important relationship between the temperature fields and the heat utilization efficiency in the oven of rotational molding equipment. If the temperatures at the main locations can be reasonably controlled, then the efficiency of the rotational molding machine can be effectively improved. The main objective of this research project is to carry out numerical simulation and analysis of the velocity field and temperature field in the oven of a shuttle-type rotational molding machine by using the commercial code FLUENT. The machine was selected as the research object owing to its uneven temperature fields and large energy wastage. The simulation results were then verified by experiments. By improving the structure of the outlets of rotational molding machine and by reasonably controlling the temperature distribution in the oven and die, the working temperature can quickly reach the maximum point, and the uniformity of the temperature in the working area can be ensured. The results showed that the molding efficiency and energy efficiency of the rotational molding machine can be improved by controlling the temperature distribution, thereby increasing the production efficiency of rotational molding.

The possibility of using polyethylene (PE) wax to modify the rheology of sulfur asphalt binders is investigated. In this study, two industrial wastes namely sulfur and PE wax are used to modify asphalt for pavement applications. Asphalt binders with different amounts of sulfur and wax content are prepared in a high shear blender and rheological tests were carried out in ARES rheometer. PE wax content was varied from 2 to 8 % and sulfur of up to 40 % is used in asphalt binder. Melt rheology is characterized by dynamic frequency sweep, temperature sweep and artificial ageing techniques. Pure and modified asphalt binders are also characterized by Fourier transform infrared spectra (FTIR). Improvement in the viscoelastic properties (G′ and G″) of the sulfur asphalt binders is obtained due to the addition of PE wax. PE wax modification has reduced temperature susceptibility of sulfur asphalt and increased the upper performance temperature. In addition, this wax modification has increased the activation energy and the zero shear viscosity of sulfur asphalt. Optimum sulfur and PE wax contents of the asphalt binder are recommended. Utilization of PE wax and sulfur wastes in asphalt modification proved to enhance asphalt pavement life.

In this work thermoplastic materials from cellulose fatty acid esters were manufactured, their properties described and application and processing perspectives evaluated. Rheological properties of some cellulose esters in melt were studied under conditions similar to those usually used in industrial polymer processing. Thermoplastic properties of cellulose esters were compared with properties of low density polyethylene under the same conditions. It was discovered that long chain fatty acid cellulose esters could be processed in the same way as commodity polymers, but these materials need further improvement for being industrially applied as thermoplastic polymers.

The primary aim of this paper is to provide an insight on the effect of the distribution of calcium carbonate nanoparticles (nano-CaCO 3 ) on the isothermal crystallization kinetics in Polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM)/nano-CaCO 3 composites prepared by different compounding procedures. PP/EPDM/CaCO 3 composites were prepared by two compounding procedures (direct compounding: mixed all three solid materials together; multistep compounding: the melted EPDM/CaCO 3 master batch in a single screw extruder blended with melted PP in twin-screw extruder via injecting into the twin-screw extruder from a lateral port at the melting section of the twin-screw extruder). Morphological observation showed that abundant CaCO 3 particles concentrated around EPDM dispersed phase in the multistep compounding composite, essentially different from the respectively dispersed morphology of CaCO 3 particles and EPDM domains in the matrix for the direct compounding composite. Moreover, better dispersion of CaCO 3 particles in the multistep compounding composite was observed comparing to the direct compounding composite. Futhermore, a pronounced improvement of the crystallization half time (t 1/2 ), rate of crystallization (G) was achieved in the multistep compounding composite, which may originate from the better dispersion of CaCO 3 particles providing larger nucleation density and the collaborative nucleation of EPDM and CaCO 3 during the isothermal crystallization.

This paper describes attenuation measurement using the modified micrsotrip line technique from new microwave substrate material. The magnitudes of the transmission coefficient (S 21 ) from the microstrip measurement were used to determine the attenuation of the ZnO/PCL nanocomposites substrate with respect to different percentages of ZnO nanoparticles filler. Result from the measurement showed amongst others that as the filler content increases, the attenuation increases. The highest magnitude for attenuation was calculated for the 70% ZnO nano filler with a value of 14.92 dB and the least attenuation was calculated for the 25% ZnO nano filler, which value gave 6.72 dB which is very good for shielding applications. Transmission electron microscope (TEM) was used to analyse the average particle size of the ZnO powder used as filler in the study. The analysis showed that the average partcile size was 52.7 nm.

Core-shell hyperbranched polyesters (HBPE) of third generation prepared from 2,2′-bis (hydroxymethyl) propionic acid (Bis-MPA) as an AB x monomer and N-heterocyclic (indole, piperidine and piperazine) phosphoryl dichloride as a core molecule by melt condensation process. These polymers were characterized by FT-IR, 1 H NMR, 13 C NMR, 31 P NMR, elemental analysis, and MALDI spectroscopy. The thermal behavior of the polymers has been investigated by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). There is no weight loss observed until 250 °C under nitrogen atmosphere. DSC showed that the glass transition temperatures was about −14 and −30 °C for the prepared core-shell HBPE. The dielectric properties such as dielectric constant and loss factor for these polyesters were also studied with respect to change of frequency (50 Hz to 5 MHz).

Nanorods/nanofibers of conducting polymer, polyaniline (PANI) were synthesized via static, liquid-liquid interfacial polymerization process using ammonium persulphate as an oxidizing agent. The monomer, aniline was dissolved in chloroform comprising the organic phase, while the oxidizing agent, ammonium per sulphate was dissolved in doubly distilled water to form an aqueous phase. Para toluene sulphonic acid (p-TSA) was used as dopant during the polymerization process to dope the polyaniline. The presence of conducting emeraldine salt phase of the polymer was confirmed by UV-Vis. and FT-IR spectroscopic characterization. This was further supported by XRD analysis. The morphological studies are carried out using FE-SEM analysis and revealed the presence of uniform sized nanorods/nanofibers having diameter of ∼90 nm and length up to few microns. This rapid and novel interfacial polymerization process shows the potential of large scale synthesis of uniform sized nanorods/nanofibers of polyaniline. The synthesized nanostructured polyaniline was successfully utilized for the optical pH sensing application in aqueous state.

Bio-based polymeric nanocomposites were prepared via polymerization of a monomer mixture of acrylated epoxidized soybean oil (AESO) and styrene in the presence of organophilic montmorillonite (MMT) clay by in-situ free-radical polymerization technique. MMT clay was rendered organophilic by a styryl/oil functionalized intercalant which is compatible with the two matrices and able to participate in the polymerization/crosslinking reaction. The presence of styryl group in the intercalant is also thought to be an original solution to the drawback mentioned in the literature arising from higher amount of small styrene monomer molecules in the clay galleries than larger AESO molecules at high clay loadings. The current design of the interclant is expected to allow polymer molecules grown from both AESO and styrene monomers inside the clay galleries and also from edges/surfaces of the silicate layers. In this study, a special attention was paid to the enhancement of both thermal and mechanical properites of AESO-based nanocomposites via usage of the compatible and reactive intercalant for MMT modification. The resultant nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of increased nanoclay loading in thermal and mechanical properties was investigated by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The nanocomposite materials exhibited improved thermal stability and dynamic mechanical properties as compared to neat polymer. The nanocomposite with exfoliation dominant structural morphology showed the highest storage modulus around T g which is about 480% higher than that of neat AESOPS, even with a clay content as low as 3 wt%.

In order to investigate the effect of kaolin coated with liquid macromolecular modifier (LKL) particles on the processability, thermal and mechanical properties of PVC materials, rigid poly(vinyl chloride) (PVC)/kaolin and PVC/kaolin coated with liquid macromolecular modifier (PVC/LKL) composites were both fabricated by melt mixing. The processability, dynamic mechanical behavior, mechanical properties and micro-structure of PVC/kaolin and PVC/LKL composites were studied by using torque rheometer, dynamic mechanical analysis (DMA), universal mechanical testing machine and scanning electron microscope (SEM). The results showed that the LKL particles improved the processability of PVC materials, while restrained the degradation of PVC materials during melt mixing due to the plasticization, toughening effect and compatibilization of the liquid macromolecular modifier (LMM). Moreover, the LMM could promote LKL particles uniformly dispersed in PVC matrix, and enhance the interface adhesion between LKL particles and PVC matrix. The notched impact strength and T g of the PVC/LKL composites achieved 4.0 kJ/m 2 and 95.2 °C, which enhanced 29% and 6 °C with respect to neat PVC materials, respectively.

Two-Stage GITBlow, a special injection molding process developed by Polymer Processing Paderborn, combines the advantages of gas-assisted injection molding and blow molding. This is achieved by producing a preform with gas-assisted injection molding, which is then inflated into a larger cavity in the same mold. The inflation behavior is heavily influenced by the temperature distribution over the cross section of the preform. The preform is not rotationally symmetric and features functional geometries that are not inflated during the second process stage. Therefore, the temperature development during the first stage, i.e. the gas-assisted injection molding, as well as cooling and handling of the preform, is essential for the subsequent inflation. If certain thermal conditions are met, inflation and the creation of a homogeneous wall thickness is improved. The development of the necessary temperature profiles for homogeneous inflation is heavily dependent on the geometry of the gas chamber. Due to the preform's geometry, characteristic material accumulations are formed during the gas injection. These create local temperature hotspots that act as heat sources during the temperature equalization before inflation starts. Simulations were conducted to predict the gas chamber geometry and its influence on the temperature distribution and development during the process. The combination of two different simulation approaches creates a new method to analyze GITBlow and similar processes. Simulation results were verified with extensive experimental studies.

In this work, thermoplastic elastomers (TPE) were produced based on polypropylene (PP) and recycled ethylene-propylene-diene monomer (r-EPDM) through twin-screw extrusion followed by injection molding. In particular, the effect of different feeding strategies (component introduction order and position along the screw) and r-EPDM content (0, 20, 35, 50 and 65% wt.) were studied. From the materials produced, morphological and mechanical characterizations were carried out. The results show that feeding strategy has a substantial influence on dispersion and compatibility between PP and r-EPDM. The main result is that r-EPDM can significantly increase PP impact strength (495%) with optimized processing conditions.

Single screw extruders with barrier screws, grooved feed zones and grooved melting zones were introduced to the European plastics industry in 1999. These extruders have an improved melting and conveying capacity among other advantages, such as a lower melt temperature, less wear, less torque and less energy consumption. The aim of this paper is to present a mathematical model for predicting the melting rate in this type of extrusion system. Based on the classical melting mechanism observed in conventional extruders, it was possible to study the effect of the geometry of the grooved barrel on the melting rate of a polymer. It was shown that the grooves on the barrel notably increase the melting rate, when compared to conventional single screw extruders. A good agreement between theory and experimental data was found.

The melt strength behavior and drawability during elongation flow of low density polyethylene (LDPE)/linear low density polyethylene (LLDPE) blends were investigated using the Rheotens test method under temperature ranging from 160 to 200 °C and die extrusion velocity varying from 9 to 36 mm/s. It was found that the blend melt strength decreased with a rise of temperature while increased with increasing the LDPE weight fraction when the extension rate or drawing ratio is constant; the dependence of the blend melt strength on the melt extension temperature roughly obeyed the Arrhenius equation; the dependence of the blend melt strength on the die extrusion velocity roughly obeyed the index equation. The drawing ratio at the melt fracture decreased with increasing the LDPE weight fraction and the die extrusion velocities, while increased with a rise of the melt extension temperature.