Particles In Polypropylene Research Articles

Mechanical, Thermal and Electrical Resisitivity Properties of Thermoplastic Composites Filled with Carbon Fibers and Carbon Particles

Composites consisting of carbon fibers (CF) and carbon particles (CP) in polypropylene (PP) matrix were melt-compounded. Composites were analyzed for their mechanical, electrical and thermal properties. Results indicate that the addition of these fillers improved the mechanical properties of the composites. Thermal conductivity was enhanced as the concentration of fillers was increased. Carbon fibers render the composites electrically conductive so we observed a percolation threshold near 10 wt.% of CF for PP/CF (PP and CF composite) and near 25 wt.% of CP for PP/CP (PP and carbon particle composite). All the results indicated that carbon fibers are more effective in improving the properties as compare to the carbon particles.

Radiation-induced modification of montmorillonite used as a filler in PP composite

In order to improve compatibility between inorganic fillers and polymeric matrix, montmorillonite (MMT) particles were modified with maleic anhydride (MA), then irradiated with electron beam, and finally were dispersed in polypropylene (PP). It was found that absorption of MA on the surface of layered clay results in the formation of salt-type bonding. Radiation treatment generates in the organic modifier stable carbon-centered radicals which, upon dispersion of activated particles in PP, induce filler-matrix linkages. Thus, such a process is another approach which has been shown to be an effective way in overcoming organophobic character of inorganic fillers in polymeric composites.

Surface-modified calcium carbonate particles by admicellar polymerization to be used as filler for isotactic polypropylene

Admicellar polymerization was used to produce a thin layer of polypropylene (PP) on the surface of calcium carbonate (CaCO 3) particles using sodium dodecyl sulfate (SDS) as the surfactant template and sodium persulfate (Na 2S 2O 8) as the thermal initiator. The admicellar-treated CaCO 3 particles were characterized by Fourier-transformed infrared spectroscopy (FT-IR), gravimetric analysis, and particle size analysis. FT-IR analysis suggested successful coating of atactic polypropylene (aPP) on the surface of the particles. The behavior of these coated particles in an isotactic polypropylene (iPP) matrix was compared to that of uncoated and stearic acid-coated ones. Non-isothermal crystallization studies indicated that surface treatment of CaCO 3 particles reduced the ability for CaCO 3 particles to nucleate the iPP matrix. Compared to composites made from the uncoated material, composites made with stearic acid-coated and admicellar-treated CaCO 3 particles had lower tensile strength, Young's modulus, and flexural strength, but higher impact strength. Observation of the fractured surfaces of the composites by scanning electron microscopy (SEM) revealed an improvement in the dispersion and distribution of the CaCO 3 particles within the iPP matrix as a result of the surface treatment.

Morphological studies of polypropylene–nanoclay composites

AbstractPolypropylene–clay nanocomposites were prepared by a solution technique and a subsequent melt‐mixing process. A titanate coupling agent was used to improve the compatibility of the nanoclay particles with the polypropylene. The dispersion of the nanoclay particles in polypropylene was studied with X‐ray diffraction (XRD) and transmission electron microscopy (TEM). An increased d‐spacing value of the clay particles in the nanocomposites was observed, and it was compared with the values of as‐mined (pristine) and as‐received (organophilic) clay particles. The number of intercalated layers in a single clay crystallite was determined to be 4, and the number was confirmed with XRD data and TEM images. On the basis of the Daumas–Herold model (which is widely used for graphite intercalation compounds), the stage 2 and stage 3 structures of montmorillonite particles in polypropylene were recommended. A study on the stage structure suggested a way of determining the presence of polymer molecules in the clay galleries. The results confirmed the existence of single‐layered platelets with improved dispersion in polypropylene. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 218–226, 2005

Thermal conductivity, thermal diffusivity, and specific heat capacity of particle filled polypropylene

Abstract By the addition of metal and oxide particles to plastics, thermal transport properties, heat capacity, and density of polymers can be varied systematically. Composites samples of polypropylene (PP) with various fillers in different fractions (up to 50 vol%) were prepared with an injection moulding process to study the evolution of the properties as a function of filler content. Standard filler materials like magnetite, barite, talc, copper, strontium ferrite and glass fibres were used. Thermal diffusivities, specific heat capacities and densities of the prepared composite samples were measured, and thermal conductivities were derived. Thermal conductivity of the polypropylene is increased from 0.27 up to 2.5 W/(m K) with 30 vol% talc in the polypropylene matrix. Thermal conductivities of the filled polypropylene samples are compared with the modelled values according to Hashin and Shtrikman. The interconnectivity of the particles in the polypropylene matrix is derived from a comparison between modelled and measured thermal conductivity values. For higher talc and glass fibre content in PP plastics, a complete interconnectivity is achieved, while copper particles in PP show a very poor interconnectivity. Specific heat capacities and thermal diffusivities of magnetite and barite filled polypropylene were measured in the temperature range from 300 to 395 K.

Selective crosslinking in polymer blends. II. Its effect on impact strength and other mechanical properties of polypropylene/unsaturated elastomer blends

AbstractThe effect of selective crosslinking of the unsaturated elastomer particles in polypropylene (PP) matrix was investigated. The crosslink system comprised N,N′‐m‐phenylene‐bismaleimide and 6‐ethoxy‐2,2,4‐trimethyl‐1,2‐dihydroqinoline or polymerized‐(2,2,4‐trimethyl‐1,2‐dihydroquinoline). The system, which produces only carbon radicals, crosslinks the elastomer particles selectively without causing excessive degradation of the PP matrix. The reaction was carried out under a dynamic crosslinking process using a twin extruder on PP/EPDM, PP/SBS, and PP/SIS blends, all of which comprised 80 wt % of PP and 20 wt % of the elastomer. After the crosslinking, the impact strength of the blends increased. Especially remarkable increase is obtained at 23°C where PP is above its Tg. The increase of interfacial adhesion caused by production of PP/elastomer graft copolymer at the interface is considered to be the most important factor in the improvement. It permits the interactions of the stress concentrate zone developed at the elastomer particles and causes shear yielding of the PP matrix. Impact fracture energy absorption can be thus changed by adjusting the degree of the interfacial adhesion even at essentially the same morphology. The crosslinked elastomer particles also play the role of a nucleation agent. The selective cross‐linking of the elastomer particles in PP/elastomer blends is demonstrated to be an excellent technique to produce a high‐impact, high‐modulus PP. © 1994 John Wiley & Sons, Inc.

The stopping power of organic compounds for alpha particles in the range 1.5-8 MeV

Range-energy relationships for 8.78 MeV alpha particles in polystyrene, polypropylene and ethyl cellulose have been determined. The stopping powers of CH and CH2 groups are compared in the solid, liquid and vapour phases and significant differences are noted. The experimental results are also compared with theoretical results. The differences indicate that the mechanism of charge-changing in different phases is incompletely understood.