Form Of Polypropylene Research Articles

Melt Spinning of Polypropylene Fiber

In this paper the melt spinning process and technology of polypropylene fiber, polymerization conditions, preparation of polypropylene fiber by a larger variety of processes and the stress in the spinline was presented. More emphasis was given on the various polymerization processes (gas-phase and liquid-phase polymerization), catalyst system, different forms of polypropylene, structure, properties and application of polypropylene. Polypropylene fibers are produced by a larger variety of processes than other melt-spun fabrics. Polypropylene based materials can be processed by various technologies such as injection molding, calendaring, air-quenched blow films, spinning technology, spunbond process. The influence of both process and material variables on the spinnability and the development of the structure during melt spinning of filament were also discussed.

Melt Spinning of Polypropylene Fiber

In this paper the melt spinning process and technology of polypropylene fiber, polymerization conditions, preparation of polypropylene fiber by a larger variety of processes and the stress in the spinline was presented. More emphasis was given on the various polymerization processes (gas-phase and liquid-phase polymerization), catalyst system, different forms of polypropylene, structure, properties and application of polypropylene. Polypropylene fibers are produced by a larger variety of processes than other melt-spun fabrics. Polypropylene based materials can be processed by various technologies such as injection molding, calendaring, air-quenched blow films, spinning technology, spunbond process. The influence of both process and material variables on the spinnability and the development of the structure during melt spinning of filament were also discussed.

Microplastics affected black soldier fly (Hermetiaillucens) pupation and short chain fatty acids

AbstractMicroplastics (MPs) are microscopic particles that are now found in almost all ecosystems where they may exert adverse effects on various organisms, including insects. In this study, 20 black soldier fly (Hermetia illucens) larvae (BSFL) were exposed to MPs, in the form of polypropylene (PP‐MPs; 55 ± 4 µm) at 0.22% (26,972,507 particles/kg), versus a control (no added MPs) in triplicate for two weeks. After two weeks, final lengths, weights, percentage of pupation, fatty acid composition of BSFL and substrate reduction percentage were measured. Survival, lengths/weights and percentage substrate reduction in the PP‐MP group were not significantly different from the control. However, percentage of pupation was significantly lower in the PP‐MP treatment (at 65.2%) compared to the control (at 83.8%). Among the measured fatty acids, only propionic and butyric acid changed, and these short‐chain fatty acids (SCFAs) significantly increased from 0.12% and 0.17% to 0.14 and 0.19%, respectively, in the PP‐MP‐exposed group. This study indicates that exposure to environmentally relevant levels of PP‐MPs can substantially delay development, while the increase in the SCFA may indicate a change in the gut microbiota.

Investigating Strength Behaviour of Pond Ash as a Construction fill material

The use of sustainable materials has become a very important issue for the researchers and geotechnical engineers in construction of embankment for highways. Due to the combustion of coal for producing electricity, enormous amount of fly ash is produced, thus causing a serious threat of disposal and creating environmental and health problems. In India, where land to population ratio is too small, it is very difficult to dispose the fly ash on a huge area of land. So, to tackle the above stated problem, it is very important to utilize the fly ash in such a manner that it does not cause any harm to environment. The aim of this study was to conduct different laboratory tests on cement stabilized pond ash, so that it becomes suitable for geotechnical fill material. Cement was added in pond ash at different proportions and the effect of this addition was studied by analyzing the strength properties of pond ash. Synthetic fiber in the form of polypropylene was added to the optimum mix of cement-pond ash in different proportions. After adding the fiber in the optimum mix, flexural behavior was studied and the failure pattern with and without fiber was observed.

Cracking of composite fiber-reinforced concrete foundation slabs due to shrinkage

Industrial concrete floors made directly on the ground are concrete slabs reinforced with structural reinforcement and often additionally reinforced with dispersed reinforcement in the form of polypropylene or steel fibers. More often than not, these floors are not separated from the reinforced concrete slab; they form a monolithic whole with it. Due to high variable loads and additional pressure of groundwater, in the case of foundation slabs in underground garages, floors ought to be subject to precise static and strength calculations. However, the load from concrete shrinkage is often neglected, as it is considered to appear temporarily in concrete care phase and to disappear gradually when the slab is normally exploited. In the recipe of the concrete mix itself, the composition of aggregate, plasticizing additives, the amount of mixing water and the addition of dispersed reinforcement should be carefully selected in order to minimize concrete shrinkage. The quality of the flooring also has a huge impact upon the course of shrinkage and the distribution of tensile stresses in the floor. The article presents the main errors related to the appearance of excessive cracking caused by shrinkage stress.

Application of waste polypropylene bags as filter media in coalescers for oily water treatment

The polypropylene fibers have been used in bed coalescers for separation of micro-sized oil droplets from water for a long time. Possibilities of applying different forms of polypropylene as filter beds are still being in the focus of many researches. The possibility of applying waste polypropylene bags used for packing vegetables (PPDJ) was investigated in this paper. The results are compared with results obtained by applying waste polypropylene fibers from carpet production (PP). It is well known that there are difficulties to separate the oils of low viscosity by polymer fiber beds. Due to the above mentioned, the presented research refers to separation of low viscosity mineral oil from water. The obtained experimental results confirm that the material PPDJ could be efficiently used as a bed material for coalescers. The critical velocity of 50 m h-1 could be reached at using both polypropylene forms that is from bags PPDJ and from the carpet industry PP, when the adequate bulk density of materials is used.

Effect of Metallic Salts of Glutaric Acid on the Formation of β-crystalline Form in Isotactic Polypropylene

The effects of glutaric acid and the lithium, sodium, potassium, magnesium, calcium, strontium, barium, zinc, and cadmium salts of glutaric acid on the formation of β-crystalline form in isotactic polypropylene (iPP) at the crystallization temperatures 120 and 130°C have been investigated. It is found that glutaric acid and the sodium, potassium, and zinc salts of glutaric acid inhibit the formation of β-crystalline form in polypropylene. Lithium glutarate has a limited positive effect on the formation of β-crystalline form. Magnesium, calcium, strontium, barium salts of glutaric acid exhibit increased β-nucleation abilities with the increasing atomic radii of the combined metals. Cadmium glutarate is a good β-nucleating agent and the formation of β-crystalline form is favored at the crystallization temperature of 120°C. The increases in the orientation of b-axes of the nucleated iPP samples are due to the presences of sodium and zinc salts of glutaric acid.

Effect of Metallic Salts of Malonic Acid on the Formation of β Crystalline Form in Isotactic Polypropylene

The effects of malonic acid and the lithium, sodium, potassium, zinc, magnesium, calcium, strontium, and barium salts of malonic acid on the formation of β crystalline form in isotactic polypropylene at the crystallization temperatures 120 and 130°C have been investigated. It was found that malonic acid and the lithium, sodium, and potassium salts of malonic acid inhibit the formation of β crystalline form in polypropylene. Zinc malonate has a limited positive effect on the formation of β crystalline form, while magnesium, calcium, strontium, and barium salts are β nucleating agents, in descending order. The decreased β nucleation abilities of the alkaline earth metallic salts of malonic acid are attributed to the increasing atomic radii of the combined metals and decreasing crystallization temperatures.

Effect of Metallic Salts of Pimelic Acid and Crystallization Temperatures on the Formation of β Crystalline Form in Isotactic Poly(propylene)

The effect of crystallization temperatures (100–140°C) on the formation of β crystalline form in isotactic polypropylene nucleated by pimelic acid and sodium, magnesium, zinc, calcium, barium and aluminium salts of pimelic acid has been investigated. It is found that β crystalline form can be produced from polypropylene melt, isothermally crystallized at 120 or 130°C. Aluminium pimelate is a α nucleator which suppresses the production of β crystalline form in polypropylene. Pimelic acid and magnesium pimelate are weak β nucleators. Sodium pimelate is a moderate β nucleator. Zinc pimelate, calcium pimelate and barium pimelate are good β nucleators for polypropylene with calcium pimelate being the best.

Use of a magnetic suspension microbalance to measure organic vapor sorption for evaluating the impact of polymer converting process

A gravimetric analyzer consisting of a magnetic suspension balance was set up to study the sorption kinetics of benzaldehyde in various forms of polypropylene (PP), including resin, sheet and thermoformed container. Instrument noise was determined throughout the experiments over a maximum of 4000 min or until equilibrium was reached. The sorption of benzaldehyde by PP resin exhibited Fickian sorption kinetics at low vapor activities (0.1–0.5). However, at high vapor activities (0.7 and 0.9), a two-stage sorption involving Fickian diffusion during the initial sorption, followed by a protracted polymer relaxation, which enhanced the sorption capacity, was observed. The converting process of PP resin into sheets and thermoformed containers had a significant impact on the benzaldehyde sorption profile. Benzaldehyde exhibited a much higher solubility in extruded sheet and thermoformed container than in the resin.

The influence of additives on the structure of polypropylene fibres

The influence of two organic pigments and two flame retardants on the structure of polypropylene fibres was investigated. It was found that by spinning at low velocities in the presence of pigments a highly crystalline structure is formed. In fibres coloured with quinacridone the rarerly encountered β form of polypropylene was observed. Utilising low take-up velocities, the addition of flame retardants leads to an increase in fibre crystallinity. In the case of fibres formed at higher velocities the influence of additives on fibres structure was less visible. For all fibres, independent of additives, a similar structure containing the α form of polypropylene was obtained.

Study on Mechanical Properties and Crystallization Behavior of Polypropylene and Its Blends Modified by β Crystalline Form Nucleating Agent

ABSTRACT The influence of β crystalline form nucleating agent (β nucleator) on the mechanical properties of homo-polymerized polypropylene (PPH), random-copolymerized polypropylene (PPR), block-copolymerized polypropylene (PPB), and PPH/PPR/PPB blends was studied. Polarized optical microscopy (POM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD) were used to characterize the crystalline morphology and behavior. The results indicated that α crystalline form of polypropylene (PP) had transformed to β crystalline form by adding 0.5% β nucleator; in the meantime, the toughness of PP and its blends was enhanced. That is, 0.5% β nucleator helped to improve the notched impact strength of PPH, PPR, and PPH/PPR/PPB blends by 130%, 40%, and 40%, respectively, without losing the tensile strength and flexural strength.

Simulations of crystallization in syndiotactic polypropylene

Crystallization in syndiotactic polypropylene was investigated using Monte Carlo methods to generate polymer chains having sequences with representative stereochemistries. The chains were then slid by one another in parallel arrangements to look for matches that could lead to crystallite formation. The results were used to estimate degrees of crystallinity, melting points and some other related physical properties as a function of stereochemical structure. The alternating (racemic) stereochemical configurations in this form of polypropylene appeared to be more favourable for such matches than the replicating (meso) ones in the isotactic modification. This suggests increased degrees of crystallinity in the syndiotactic polypropylene at the same level of stereoregularity as the isotactic polymer, as was also predicted by Natta. The simulations are consistent with syndiotactic polypropylene having a lower enthalpy of fusion and with the negative surface free energies predicted for samples with lower degrees of syndiotacticity. The predicted melting points are such that for syndiotactic polypropylene to exhibit room temperature crystallinity it would have to have higher degrees of crystallinity than would be acceptable for a thermoplastic elastomer. The simulations also indicate that syndiotactic crystallization would not coexist with isotactic crystallization in the same sample of polypropylene unless there was an extremely wide range of replication probabilities.

Simulations of crystallization in syndiotactic polypropylene

Crystallization in syndiotactic polypropylene was investigated using Monte Carlo methods to generate polymer chains having sequences with representative stereochemistries. The chains were then slid by one another in parallel arrangements to look for matches that could lead to crystallite formation. The results were used to estimate degrees of crystallinity, melting points and some other related physical properties as a function of stereochemical structure. The alternating (racemic) stereochemical configurations in this form of polypropylene appeared to be more favourable for such matches than the replicating (meso) ones in the isotactic modification. This suggests increased degrees of crystallinity in the syndiotactic polypropylene at the same level of stereoregularity as the isotactic polymer, as was also predicted by Natta. The simulations are consistent with syndiotactic polypropylene having a lower enthalpy of fusion and with the negative surface free energies predicted for samples with lower degrees of syndiotacticity. The predicted melting points are such that for syndiotactic polypropylene to exhibit room temperature crystallinity it would have to have higher degrees of crystallinity than would be acceptable for a thermoplastic elastomer. The simulations also indicate that syndiotactic crystallization would not coexist with isotactic crystallization in the same sample of polypropylene unless there was an extremely wide range of replication probabilities. ©1997 SCI

Change of crystalline forms of polypropylene during purification

Change of crystalline forms of polypropylene during purification

The mechanical behavior of springy polypropylene

AbstractTo obtain further details of the unusual behavior of the “hard elastic,” “springy” form of polypropylene (SPP), various loading conditions were studied with an Instron model 1130. Specifically, the variation of the elongation at rupture with change in gauge length and strain rate has been determined. The nature and degree of the specimen hysteresis resulting from various loading cycles have been characterized. The ability of this material to recover from large extensions customarily expected to be permanent deformation has been identified and the time dependency of this recovery has been determined for strain levels of 10, 25, 50, and 100 percent of the original sample length. The effects of submitting the material to conditioning treatments, e.g., immersing in saline solutions of various electrolyte concentrations and autoclaving for 30 min at 250°F and 15 psig have been studied. Characterization of the stress relaxation behavior of the polymer has been made. Fatigue behavior has been identified utilizing a novel testing apparatus which permits load‐cycling of the fiber. Rheovibron work has facilitated calculation of the activation energy of the second order relaxation of SPP from tan δ vs temperature data. Stoll abrasion testing results on SPP tubular knit fabric and multifilament yarn have been compared to normal polypropylene and Dacron®.

Deformation and aging of quenched polypropylene

AbstractThe physical properties, i. e., yield stress and stress‐strain curve of the quenched (“smectic”) form of polypropylene have been shown to be time dependent at room temperature. The yield stress increases linearly with the logarithm of film age. No changes in the x‐ray diffraction pattern, infra‐red spectrum, electron diffraction pattern or morphology have been observed corresponding to this change in physical properties. A molecular mechanism is proposed which will explain this again process. Spherulites of the quenched form have been found to deform affinely when drawn. In contrast to this, slow cooled films show complete destruction of internal spherulite (lamellar) order, indicating a complex mechanism of deformation.

The nature of isotactic and atactic polypropylene. Evidence from radiation effects

Except for an enhanced yield of methane from atactic polypropylene, probably due to greater diffusibility or the methane in the amorphous atactic solid, there is no essential difference between the two forms of polypropylene. Thus, there is no evidence that the atactic polypropylene contains branched structures. (P.C.H.)

On the existence of near-range order in isotactic polypropylenes

A form of polypropylene, intermediate between amorphous and crystalline, has been detected and studied by means of X-ray scattering, i.r. absorption, n.m.r. absorption, dynamic mechanical, and volumetric measurements. This form (called non-crystalline) is characterized as being an aggregation of molecules (or segments of molecules) in which portions of the individual chains maintain the helical structure found in the crystal but in which there is little, or no, lateral order sufficient to be called crystalline.