Polypropylene

In this paper, a study on the batch processing and characterization of microcellular foamed high-density polyethylene (HDPE/iPP) blends is reported. A microcellular plastic is a foamed polymer with a cell density greater than 109 cells/cm3 and fully grown cells smaller than 10 µm. Recent studies have shown that the morphology and crystallinity of semicrystalline polymers have a great influence on the solubility and diffusivity of the blowing agent and on the cellular structure of the resulting foam in microcellular batch processing. In this research, blends of HDPE and iPP were used to produce materials with variety of crystalline and phase morphologies to enhance the subsequent microcellular foaming. It was possible to produce much finer and more uniform foams with the blends than with neat HDPE and iPP. Moreover, the mechanical properties and in particular the impact strength of the blends were significantly improved by foaming.
(citation # 293)

Summary Inguinal hernia has been successfully treated using prostheses. However, doubts still remain with regard to tension-free and sutureless techniques, about tension and torsion, wrinkling, prosthesis dislocation and complications in the post-operative phase. We are therefore proposing a new technique, involving the use of a polypropylene prosthesis (Prolene®), known as P.A.D. (Protesi Autoregolantesi Dinamica) which is designed to eliminate these

The melting behavior of restrained isotactic polypropylene fibers is examined quantitatively in terms of the influence the anisotropic structural state of the polymer has on the observed properties. Two endotherm peaks are observed to occur in some of the samples. The formation and location of the multiple peaks are determined by the orientation of the noncrystalline chains, and is independent of the fabrication path used to achieve that orientation. Above a certain minimum orientation of the noncrystalline chains, multiple endotherm peak formation occurs. The high-temperature endotherm (T2M) extrapolates to an ultimate melting point for fully oriented noncrystalline chains of 220°C, while the lower-temperature endotherm (T1M) extrapolates to an ultimate melting point of 185°C. Noncrystalline chain orientation influences the endotherm temperature through its changing configurational entropy. It is shown quantitatively that the noncrystalline polymer must be considered as plastically deformed, since rubber elasticity theory is not followed as predicted. The melting behavior of isothermally crystallized samples are also reported to further elucidate the nature of the observed endotherms.

Effects of an ionic liquid, 1-n-tetradecyl-3-methylimidazolium bromide ([C14MIM] Br), as a foaming additive on the foaming behavior of polypropylene(PP) by supercritical CO2 technique was reported. Mass ratio of PP/[C14MIM] Br up to 100: 10 was incorporated via melt blending. The melting behavior and fractured morphology of PP/[C14MIM] Br samples were investigated by differential scanning calorimetry(DSC) and scanning electron microscopy(SEM), respectively. The CO2 sorption was measured by commonly accepted gravimetric method. The results of DSC and CO2 sorption experiments show that [C14MIM] Br has little effect on the crystallinity, melting point and the mass uptake of CO2 of PP. SEM images reveal that [C14MIM] Br forms a well-dispersed phase, whose size increases with [C14MIM] Br content, in the PP matrix. The foamed PP/[C14MIM] Br samples exhibit close cell structure, increased cell size and decreased unfoamed region and bulk density, compared with pure PP foamed under the same saturation conditions of 155 degrees C/10 MPa, indicating ionic liquid [C14MIM] Br has significant effect on the foaming behavior of PP.
Chemical Journal of Chinese Universities -Chinese Edition- 05/2010; 31(5):861-863.

ABSTRACT In this research, cocoa pod husk (by-product from cocoa industrial) has been utilized as filler in polypropylene (PP) matrix biocomposites. The CPH filler was modified with different contents of methacrylic acid (MAA) and its effect on tensile properties of PP/CPH biocomposites was investigated. The result showed that 3% of MAA gave the optimum improvement on tensile strength and tensile modulus of PP/CPH biocomposites. However, the MAA modification reduced the elongation at break of PP/CPH biocomposites. The improvement of tensile properties is attributed by the presence of MAA enhancing the filler-matrix interfacial bonding. The scanning electron microscope results indicated that the modified CPH exhibited less filler pull-out and was well wetted by the PP matrix, which indicated better interfacial bonding. Fourier transmission infrared (FTIR) confirm that the MAA was covalently bonded to the CPH filler surface.

The aim of this study was to investigate the deposition of particles in three types of synthetic fabric filter by scanning electron microscope (SEM) and to determine the experimental adhesive force of filter cakes in fabric filters. The fabrics used were acrylic, polypropylene and polyester. The particulate matter was phosphate rock. The particles were deposited in the filters during 10 filtration cycles, with a superficial filtration velocity of 0.10 m/s and maximum pressure drop of 980 Pa across the filter. The cleaning technique used was reverse air flow at 0.12 m/s. The results showed that the deposition depth of particles in the polypropylene filter was lower than those observed in the polyester and acrylic filters. Nevertheless, the residual pressure drop of the polypropylene at the beginning of the filtration assays was highest, owing to the greater accumulation of particles at the surface of the filter and the characteristics of the filter itself. It was also observed that the adhesion force was higher in the polypropylene filter than in the other filters, making it hard to remove the filter cake from that filter.► The behavior of the particle deposition and adhesion forces can improve the understanding of the cycles of filtration. ► The polypropylene filter exhibited the highest number of particles retained on the surface of the filter. ► The acrylic and polyester filters trapped greater numbers of particles internally than the polypropylene filter. ► The adhesion force was higher in the polypropylene filter, making it difficult to remove the cakes from the filter.

A Ceramic Injection Moulding process has been used for the manufacturing of Ni-Zn Ferrite parts. The binder was based on a combination of polypropylene and paraffin wax. Different feedstocks were prepared in order to check the effect of stearic acid. Rheology of feedstocks was evaluated using a capillary rheometer over a temperature range of 160-170-180 C and a shear-rate range of 100-3000 s-1. All the feedstocks presents pseudoplastic behaviour and an important decrease of the viscosity occur when the SA is added. However, different amount of SA has not effect in this property over the shear-rate range tested. Two different debinding cycles was optimized, by means of thermogravimetric analysis. The sintering was performed at the same conditions than this type of ferrite processed by uniaxial pressure. Final densities and magnetic properties are compared with those obtained by uniaxial compacted parts.

The high molecular weight polypropylene (PP) nanospheres (average particles size ∼ 60 nm) were synthesized under controlled growth condition using Ziegler-Natta catalyst. The sizes of the PP particles were investigated through microscopy analysis. The size-dependent crystal structure and crystallinity were studied through X-Ray powder diffraction (XRD) and differential scanning calorimetry (DSC). At 25°C PP nanoparticles show higher crystallinity (∼76%) compared to the micron sized PP particles (∼59%). The rearrangement of polymer chains is the reason for the higher crystallinity of nanosphere PP particles. The periodic organization of PP chains inside the nanoparticles shows new peaks. These corroborate the presence of α-monoclinic phase. The α-crystalline lamella lengths of various particle sizes are calculated and found to be 14.5 nm for nanoparticles, whereas the same for the microsphere PP is 17.6 nm. The crystal domains consist of various sizes of α-monoclinic crystals. Moreover, the absence of γ-orthorhombic phase acknowledges that the PP nanospheres are composed of α-monoclinic crystal domains.

Investigations on solar-driven membrane distillation (SDMD) were carried out for removal of arsenic from contaminated groundwater. Three different types of hydrophobic membranes made of polytetrafluoroethylene (PTFE) and polypropylene (PP) with surface area of 120×10−4m2 were used as flat sheet in a direct contact membrane distillation (DCMD) set up in a cross flow module. Effects of initial arsenic concentration in the feed, feed velocity, feed temperature and distillate inlet temperature on arsenic removal efficiency and flux were studied where temperatures of feed and distillate were found to have significant effect on the flux. Almost 100% arsenic separation was achieved without wetting membrane pore even after 120h of operation. The PTFE membrane with a flux of 49.80kg/m2h was found to the best one out of the tested membranes. The study shows that solar-driven DCMD can effectively separate arsenic from groundwater using a cross flow membrane module with PTFE hydrophobic membrane.

It is well known that polypropylene undergoes simultaneous crosslinking and degradation under irradiation. However, there are speculations regarding the formation of branching under special conditions. It is also well known that the melt-strength property of a polymer increases with molecular weight and with long-chain branching due to the increase in the entanglement level. This study was a contribution to the

Natural and wood fibre reinforced plastics as a relatively new group of environmental friendly materials have been extensively applied in interior, building applications and in the automobile industry. Among others, natural and wood fibre reinforced foamed polymer materials are of high significance because of the possibility of their reducing the density of automotive components which have a cellular structure. However, the properties of these materials have not been fully investigated and described. Microcellular composites of polypropylene containing natural and wood fibre was prepared using an injection moulding process. In the present work, the manufacturing technology of natural and wood fibre reinforced polymer microfoams was developed and the influence of fibre and microvoid content on its property spectrum was systematically investigated. The forming of microvoids and the degree of foaming related to the variation of the processing parameters in connection with manufacture technology was characterised. Measurement of density, cell size, tensile and flexural properties of the prepared composites was carried out. The cell structure is dependent on flow direction of foaming. The density of microfoamed wood fibre-PP composites was reduced by about 24% and decreased by as much as 0.77 g/cm3.Light microscopy showed that the cells are circular and it was also observed that the maximum cell sizes are between 10–50 μm. Water absorption and scanning electron microscopy of the composites were also investigated. Considering the experimental results, it can be deduced that the microcellular composites exhibit a possible combination of relatively good engineering properties and lower density for different technical applications. Natur- und holzfaserverstärkte Kunststoffe, als relativ neue Gruppe von umweltfreundlichen Werkstoffen, werden derzeit in beachtlichem Umfang in der Bauindustrie (Dach-, Boden- und Wändeabdeckungen) und Automobilindustrie verwendet. Ausserdem haben natur- und holzfaserverstärkte Polymerwerkstoffe –Mikroschäume, die wegen ihrer zellularen Struktur die Dichte der Bauteile noch reduzieren können, eine immer größere Bedeutung erlangt. Bisher sind die Eigenschaften dieser Werkstoffe nur beschränkt untersucht und beschrieben worden. Natur- und holzfaserverstärkte PP-Mikroschäume wurden im Spritzgießverfahren hergestellt. Im Rahmen der vorliegenden Arbeit wurde die Fertigungstechnik der natur- und holzfaserverstärkten Polymere-Mikroschäume entwickelt und systematisch der Einfluss des Faser-/ und Mikroporengehalts auf das Eigenschaftsspektrum dieser Werkstoffe untersucht. Mikroporen und Schäumungsgrad in Abhängigkeit von der Variation der Verarbeitungsparameter wurden in Verbindung mit dem Herstellungsprozess charakterisiert. Die Dichte, die Zellgröße, die Zug- und Biegeparameter der hergestellten Compositen wurden ermittelt. Die Schaumstruktur ist vom Fließweg abhängig. Die Dichte von geschäumten holzfaserverstärkten PP kann bis ca. 24% reduziert werden und erreicht Werte von 0,77 g/cm3. Die mikroskopischen Aufnahmen zeigen, dass die Mikroporen eine runde Struktur aufweisen, und der Porendurchmesser zwichen 10–50 μm liegt. Die Wasseraufnahme wurde ebenfalls untersucht. Die erzielten Ergebnisse belegen, dass diese Werkstoffe für verschidene Anwendungen in der Technik geeignet sind.

An expeditious method for the determination of triclosan (TCS) and methyl triclosan (MTCS) in sludge and sediment samples is presented. Extraction and cleanup steps were integrated in the same process using matrix solid-phase dispersion as sample preparation technique. Effects of different variables on the efficiency and the selectivity of the sample preparation process are discussed. Under final working conditions, samples (0.5 g) were dispersed with diatomaceous earth (1 g) and transferred to a polypropylene syringe containing 2 g of silica impregnated with sulphuric acid (15%, w:w). Analytes were recovered with 10 mL of dichloromethane. After solvent exchange to ethyl acetate, TCS was converted into the tert-butyldimethylsilyl derivative, and the extract was analysed by gas chromatography-mass spectrometry, without any additional cleanup. Obtained recoveries, for sludge and sediment samples spiked at different concentration levels, ranged from 86% to 113%, with associated standard deviations between 2 and 13%. Limits of quantification of the global method were 6 and 7 ng g−1 for MTCS and TCS, respectively. Both compounds were detected in all the processed sludge samples with maximum concentrations of 191 ng g−1 (MTCS) and 2,640 ng g−1 (TCS). The parent bactericide was also found in some sediment samples at concentrations up to 200 ng g−1.

Natural cellulose fibers have been obtained from the bark of cotton stalks and the fibers have been used to develop composites. Cotton stalks are rich in cellulose and account for up to 3 times the quantity of cotton fiber produced per acre. Currently, cotton stalks have limited use and are mostly burned on the ground. Natural cellulose fibers obtained from cotton stalks are composed of approximately 79% cellulose and 13.7% lignin. The fibers have breaking tenacity of 2.9 g per denier and breaking elongation of 3% and modulus of 144 g per denier, between that of cotton and linen. Polypropylene composites reinforced with cotton stalk fibers have flexural, tensile and impact resistance properties similar to jute fiber reinforced polypropylene composites. Utilizing cotton stalks as a source for natural cellulose fibers provides an opportunity to increase the income from cotton crops and make cotton crops more competitive to the biofuel crops.