Polypropylene Pellets Research Articles

Nitrogen removal from domestic wastewater using immobilized bacteria

Two bench-scale Runs, namely Run A and Run B, have been investigated in order to study the effect of immobilized bacteria on denitrification in anoxic-oxic process. The hollow polypropylene pellets (O.D. 4 mm, I.D. 3 mm, nominal density 1.001 g/cm3) have been dosed into the anoxic reactor in Run A up to 24% of the volume. Run B was operated with no pellets in the anoxic reactor as a control experiment. Both Runs A and B contained the above pellets in the oxic reactor for a total volume of 24%. Run A showed superiority in nitrogen removal (73%) compared to Run B (65%) at a loading of 0.219 kgN/m3.d for a detention time of 4 hours at 15°C. By further investigating into the mechanism of nitrogen removal, it was concluded that the immobilized bacteria in the anoxic reactor in Run A enhanced not only the denitrification but also the ammonification that resulted in higher nitrogen removal efficiency.

Compatibilization of polypropylene/poly(n-butylacrylate) blend: Functionalization of the poly(n-butylacrylate) phase by copolymerization

Compatibilization of a polypropylene (PP)/polybutylacrylate (PBuA) blend was studied, with the aim of achieving better adhesion at the interphase through modification of both the PP and PBuA phases. The compatibilization involved two separate stages: First, a small amount (2 and 5 mol %) of functional monomer copolymerizable with and soluble in BuA was added to the BuA initiator solution. Then, this solution was impregnated into PP pellets and polymerized inside the pellets by free-radical polymerization in a water suspension. The resulting blend was a thermoplastic elastomer consisting of PP as the matrix and functionalized PBuA as the partly crosslinked dispersed rubbery phase. The functionalities of the monomers were epoxy, oxazoline, hydroxyl, secondary amine, and carboxyl. In the second stage, two commercial graft copolymers of PP (PP grafted with either acrylic acid or maleic acid anhydride) were blended at the melt stage with the PP/functionalized PBuA blend. Here, the compatibilizing reactions took place between the functionalized components of the blend. The compatilization reactions were detected by FTIR analysis and by changes in mechanical or thermomechanical behavior of the blends. Morphology studies were carried out. As a result, the tensile strength, tensile modulus, elongation at break, and tear strength of the final product were improved by about 15, 20, 160, and 50%, respectively, compared with the unfunctionalized blend. The hardness of the material remained unchanged in the compatibilization. © 1996 John Wiley & Sons, Inc.

Injection Molding of Microcomposites Based on Polypropylene and Thermotropic Liquid Crystalline Polymers

Abstract This work is concerned with the injection molding of pellets of polypropylene (PP) containing pregenerated microfibrils of thermotropic liquid crystal polymers (TLCPs), referred to as microcomposites. The TLCPs used are HX6000 and Vectra A950. The microcomposites are produced by drawing strands of PP and TLCPs generated by means of a novel mixing technique and pelletizing the strands. The work was undertaken in an effort to improve on the properties observed for in situ composites in which the TLCP fibrils are generated during mold filling. In situ composites usually exhibit highly anisotropic mechanical properties and the properties do not reflect the full reinforcing potential of the TLCP fibers. Factors considered include the effect of in situ composite strand properties on the properties of the injection molded composite, the melt temperature used in injection molding, TLCP concentration, and the melt temperature of the TLCP. It is found that when processed at appropriate temperatures, the TLCP microfibrils are maintained through injection molding, and the composites show a good balance between machine and transverse direction properties (with ratios of the machine and transverse direction moduli ranging from 1.1 toto 1.35). The use of HX6000 rather than Vectra A allows for higher processing temperatures to be used during injection molding. The moduli of the injection molded composites increase with both increasing TLCP composition and in situ composite strand moduli. At 10 wt.-% TLCP the moduli of the injection molded composites approach the predictions of composite theory while at 20 and 30 wt.-% TLCP negative deviations from the theoretical moduli are seen. This is believed to be the result of a loss of fiber aspect ratio from fiber breakage and agglomeration. It is believed that with future studies on the effect of shear and elongational stresses during processing on the aspect ratio of the fibers a means of overcoming this problem may be found. The modulus of a 20 wt.-% HX6000 composite is similar to that of a 20 wt.-% glass composite (3.21 GPa versus 3.66 GPa), but the tensile strength of the HX6000 composite is about 28 % lower than that of the glass composite. It is expected that as the modulus and strength of the reinforcing TLCP fibrils are improved the properties of the injection molded microcomposites should exceed those of glass reinforced composites.

Sheet extrusion of microcomposites based on thermotropic liquid crystalline polymers and polypropylene

AbstractThis work is concerned with the extrusion of sheets from pellets of polypropylene (PP) containing pregenerated microfibrils of thermotropic liquid crystal polymers (TLCPs), referred to as microcomposites. The TLCPs used were HX6000 and Vectra A950. The microcomposites are produced by drawing strands of PP and TLCPs generated by means of a novel mixing technique and pelletizing the strands. The work was undertaken in an effort to improve on the properties for in situ composites in which the TLCP fibrils are generated in contractions in the die and the subsequent drawing step. In situ composites usually exhibit highly anisotropic mechanical properties and the properties do not reflect the full reinforcing potential of the TLCP fibers. Factors affecting the mechanical properties of the composite sheets considered include the effect of in situ composite strand properties and TLCP concentration. In addition, the properties of the extruded sheets are compared to those of microcomposites processed by means of injection molding. It is shown that the sheets produced using microcomposites have a good balance between the machine and transverse direction properties (ratios of these properties ranging from 0.8 to 1.2) and those properties compare well to those obtained by processing microcomposites in injection molding. The tensile modulus of the composite sheets increases with increasing in situ composite strand modulus. The moduli of the 20 wt% Vectra A950 and HX6000 composites are about equal to the modulus of 20 wt% glass reinforced PP (about 2.1 GPa), while the tensile strength of the TLCP reinforced composites is 28% lower than that of the glass reinforced PP. Furthermore, it is shown that the tensile modulus of the 10 wt% TLCP composites approach the predictions of composite theory, while at 20 and 30 wt% TLCP negative deviations from the predictions of composite theory are seen. Finally, it is concluded that the properties of the sheets produced through the extrusion of microcomposites may be further improved by improving the modulus of in situ composite strands and reducing the TLCP fiber diameter.

Extrusion blow molding of microcomposites based on thermotropic liquid crystalline polymers and polypropylene

AbstractThis work is concerned with the extrusion blow molding of bottles from pellets of polypropylene (PP) containing pregenerated microfibrils of thermotropic liquid crystal polymers (TLCPs), referred to as microcomposites. The TLCPs used are HX6000 and Vectra A950. The microcomposites are produced by drawing strands of PP and TLCPs generated by means of a novel mixing technique and pelletizing the strands. The work was undertaken in an effort to improve on the properties observed for in situ composites in which the TLCP fibrils are generated in elongational flow fields that occur in polymer processing operations and to determine if TLCP reinforced bottles could be produced by extrusion blow molding of microcomposites. In situ composites usually exhibit highly anisotropic mechanical properties and the properties do not reflect the full reinforcing potential of the TLCP fibers. Factors considered include the effect of TLCP concentration and in situ composite strand properties on the mechanical properties and anisotropy of bottles made from microcomposites. Specifically, strands having three different draw ratios are used to produce bottles at 10 and 20 wt% TLCP. Increasing the in situ composite strand modulus is shown to cause an increase in both the machine and transverse direction moduli of the composite bottles. The mechanical properties of the bottles increase with increasing TLCP composition. Finally, the machine and transverse direction properties are not balanced in the composite bottles produced in this study (degrees of anisotropy ranging from 1.5 to 1.8). The mechanical anisotropy is probably the result of a low blow up ratio (2) in the bottles and the TLCP fibers being oriented primarily in the machine direction due to the shear flow in the die.

Nitrogen removal from domestic wastewater using immobilized bacteria

Two bench-scale Runs, namely Run A and Run B, have been investigated in order to study the effect of immobilized bacteria on denitrification in anoxic-oxic process. The hollow polypropylene pellets (O.D. 4 mm, I.D. 3 mm, nominal density 1.001 g/cm3) have been dosed into the anoxic reactor in Run A up to 24% of the volume. Run B was operated with no pellets in the anoxic reactor as a control experiment. Both Runs A and B contained the above pellets in the oxic reactor for a total volume of 24%. Run A showed superiority in nitrogen removal (73%) compared to Run B (65%) at a loading of 0.219 kgN /m3.d for a detention time of 4 hours at 15°C. By further investigating into the mechanism of nitrogen removal, it was concluded that the immobilized bacteria in the anoxic reactor in Run A enhanced not only the denitrification but also the ammonification that resulted in higher nitrogen removal efficiency.

Polypropylene pellets as an inexpensive reusable substitute for milk in the Morris milk maze

A new inexpensive opaquing agent for the Morris milk maze is described. Small light-weight polypropylene pellets that float on the surface of the water were used to eliminate visual cues about the location of the hidden platform without impeding swimming or the use of distal spatial cues. Results obtained using the pellets are identical to those obtained with milk powder as an opaquing agent. An automatic tracking system works as well with the pellet as with the milk version of the maze.

Volatile compounds extracted from polypropylene sheets by hot water: Influence of the temperature of sheets injection

AbstractThe influence of the formulation of polypropylene (PP) on the organoleptic properties of the foodstuff in contact is of great importance for the quality of the product. A study was made on PP pellets degraded and not degraded and pointed out the presence and olfactive importance of volatile components extracted from PP pellets by hot water. Plastic packaging materials correspond to a further step of manufacturing: the injection step, and this is often conducted at high temperature. PP (not degraded) and PP‐CR (degraded) were transformed into sheets at several temperatures; Lickens–Nickerson extracts were made and allowed the quantification of volatile compounds already identified. A statistical analysis showed that temperature was a very significant parameter. An increasing injection temperature (275 or 300°C) creates increasing quantities of volatiles. This was well correlated with the sensory analysis made on the organic extracts of the sheets and also directly on molded cups. © 1993 John Wiley & Sons, Inc.

Analysis of Polymer Pellets Obtained from Two Extruders Using near Infrared Spectroscopy

The near infrared spectroscopic determination of additive levels in polypropylene pellets obtained from two process extruders/pelletisers is described. A quotient-term multiple linear least-squares spectroscopic model was derived that characterises analyte concentration and corrects for spectroscopic differences within the matrix due to the extruder/pelletisers. The analytical error of the spectroscopic model is comparable to the reference method used to derive the spectroscopic model.

Volatile compounds extracted from polypropylene pellets by hot water: Influence of the level of the peroxide agent

AbstractTo improve the quality level of plastic packaging materials, we determined the influence of chemical degradation of polypropylene (PP) upon the amount of volatile components extracted by hot water from PP pellets. Two formulations were analyzed and compared: PP CR (degraded) and PP (not degraded). After Likens‐Nickerson's extraction of the pellets and concentration of the extract, an HPLC fractionation was made to collect three fractions of different poiarities: a pentane (A), a dichloromethane (B), and an ether (C) fraction. Fractions (B) and (C) were olfactively evaluated by GC sniffing to be most interesting. Their analysis by GC/MS coupling allowed the identification of different components: aldehydes, ketones, and phenols in fraction B and alcohols and acids in fraction C. A quantitative analysis gave us the amounts of volatiles that were compared to their olfactive thresholds in water; thus, in fraction (B), nonanal and decanal were concluded to have a potential olfactive contribution to the odor of water in contact with PP. A statistical analysis showed that chemical degradation had little influence upon the amounts of volatiles extracted from PP pellets by hot water.

Removal of dimethyl sulfide, methyl mercaptan, and hydrogen sulfide by immobilized Thiobacillus thioparus TK-m

Cells of Thiobacillus thioparus TK-m were immobilized on cylindrical porous polypropylene pellets (5 mmφ × 5 mm) which were packed in an acrylic cylinder of 50 mm inner diameter up to the height of 800 mm. When a sulfur-containing malodorous gas was charged to this packed tower at the superficial velocity of 0.1 m/s, maximum loading capacity (mmol/ l·d) for a malodorous gas to attain the removal rate of 95% or more was: 3.65 for dimethyl sulfide, 8.74 for methyl mercaptan, and 17.36 for hydrogen sulfide. At this time, the inlet concentration (μl/ l) of the malodorous compound was: 7.44 for dimethyl sulfide, 17.8 for methyl mercaptan, and 35.4 for hydrogen sulfide. For every compound, higher loading resulted in greater removal quantities. The removal rate of dimethyl sulfide was not overly affected by the presence of a large amount of easily decomposable hydrogen sulfide.

Determination of the hindered amine additive CGL‐144 in polypropylene by high‐performance liquid chromatography

AbstractA method was developed to determine CGL‐144 (Tinuvin 144) in polypropylene. Polypropylene pellets were dissolved in hot decalin. The solution was cooled to precipitate the polymer. A portion of the filtered extract solution was injected onto a normal‐phase high‐performance liquid chromatography (HPLC) system consisting of a μ‐Porasil stationary phase and a chloroform:ethanol:ammonia (95:5:0.05) mobile phase. The amount of CGL‐144 was determined by peak height measurement from an ultraviolet absorption detector set at 280 nm. Injections could be made every 10 min. The limit of detection for the method as described is 0.06% CGL‐144 in polypropylene. There are no known interferences with this method.

Plastic debris in the surface waters of the South Atlantic

Polyethylene and polypropylene pellets, together with tarballs, were found to be the most common contaminates of the sea surface in the Cape Basin area of the South Atlantic Ocean. This is an area far removed from any obvious source of such materials.

Polyphloretine phosphate as an inhibitor of platelet adhesion. Comparison with acetylsalicylic acid and dipyridamole

The purpose of the study was to compare the reduction of platelet retention on polymeric surfaces following administration of polyphloretine phosphate (PPP), acetylsalicylic acid (ASA) and dipyridamole. Arteriovenous shunts were inserted at 30 min intervals in Defibrase defibrinogenated dogs with 51Cr-labelled platelets. The shunts consisted of polyethylene tubes filled with polypropylene pellets in order to increase contact surface and foreign surface. Defibrinogenation was used in order to study platelet behaviour without interaction of fibrin formation and to prevent occlusion of the shunts by plasma coagulation. The retention of platelets on the foreign surface was measured before and after intravenous administration of PPP, ASA and dipyridamole. PPP reduced the number of platelets retained on the surface by 94–98%. PPP exerts a slight heparin-like activity, but this was not responsible for the observed effect. ASA and dipyridamole reduced the number of retained platelets by 27–50% and 15–33% respectively. The two substances combined reduced platelet retention by 22–34%. The experimental model itself may have caused some reduction of the retention. It is concluded that in this experimental model PPP is a more potent inhibitor of platelet retention than ASA or dipyridamole, alone or in combination.