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  • 1
    Electronic Resource
    Electronic Resource
    The effect of processing on rheological and molecular characteristics of a low density polyethylene (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 377-382 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The viscoelastic responses of some molten polymers, and particularly of low density polyethylene (LDPE), are known to vary with processing history. Reasons for the variations include the effects of shear history on morphological states of the polymer, or on its molecular weight parameters. A typical low density polyethylene has been used to test the shear-history dependence concept following a variety of processing steps. The polymer was sheared in single-screw and twin-screw extruders, and in a high speed melter / mixer (Gelimat). Samples also were precipitated from very dilute solutions in trichlorobenzene and in p-xylene. GPC analyses showed that, in general, these procedures did not affect the various moments of molecular weight. An exception was the Gelimat-mixed sample, for which mild reductions in Mn and Mw were noted. In contrast, melt viscosity and elasticity readings, the former from low shear evaluations and the latter from extrudate swelling, were affected by the various procedures. A drop in melt viscosity and in elasticity was observed, being most pronounced for precipitated and twin-screw extruded versions of the LDPE. Reductions also were observed in the specimen sheared in the Gelimat instrument. Following conditioning at the test extrusion temperature (170°C), viscous and elastic responses tended to revert to those of the unsheared control sample, the exception again being the sample sheared in the Gelimat melter / mixer. Of the various mechanisms proposed in the literature to account for transient property changes such as those reported, temporary changes in the degree of chain entanglement appear the most satisfactory explanation. Irreversible alterations in viscoelastic properties may be associated with changes in molecular weights due to processing at high shear.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760330702
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  • 2
    Electronic Resource
    Electronic Resource
    Some effects of irradiation on properties of filled PVC compounds (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 981-985 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Compounds based on poly(vinyl chloride) (PVC), and containing CaCO3 filler and trifunctional acrylic crosslinking agent have been crosslinked by exposure to γ-rays at dosages to 70 kGy. The crosslinking agent was found to be essential for crosslinking to proceed, only minor sensitivity to the irradiation having been found in compounds omitting the chemical. The presence of filler somewhat inhibits crosslink effectiveness, as measured by solvent uptake data. Elastic moduli and elongations at rupture respond to crosslinking processes, the latter being particularly sensitive to the effects of irradiation. The presence of filler was found to raise modulus, while ductilities of compounds were greater than expected, owing to adhesion at polymer/filler interfaces. Favorable acid/base interaction forces appear responsible for the effect. The reduced sensitivity of filled PVC compounds to γ-ray exposure is attributed to polymer immobilization, the consequence of strong interfacial bonding with the filler.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341206
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  • 3
    Electronic Resource
    Electronic Resource
    Some properties of polyethylene compounds with surface-modified fillers (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 263-269 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The dispersion of variously surface-treated CaCo3 fillers in linear low density polyethylene has been studied, along with mechanical properties of the filled compounds. Microwave plasma discharges were used to modify the filler surfaces. Inverse gas chromatographic analyses showed that plasma treatments could change the dispersive and non-dispersive components of filler surface characteristics. A reduction in these surface energies facilitated the dispersion of the filler in the non-polar polyethylene. Mechanical properties, particularly those at high deformation of the filled plastic, also responded to filler surface treatments, the ductility at failure increasing with a decrease in the filler's surface polarity. For any given elongation at failure, it was found that the amount of filler accommodated by the host polymer was raised by the appropriate surface modification procedure. The work illustrates the important contribution made by interfacial phenomena to various performance aspects of complex polymer systems.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760300503
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  • 4
    Electronic Resource
    Electronic Resource
    New approaches to the processing of rutile-filled polyolefins (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 950-956 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The performance of a fluorocarbon elastomer processing additive in rutile-filled linear low density polyethylene (LLDPE) compounds was evaluated by capillary rheometry, and blown film extrusion. Different compounding sequences were considered and their effects on the performance of the processing additive in the presence of various rutiles examined. Lower apparent melt viscosities and higher shear rates for the onset of melt fracture were observed when using certain surface treated rutiles. The nature of the surface coating applied to rutiles was found to have a great influence on the Theological properties of the filled compounds and on the dispersibility of the solids. The acid-base characteristics of rutiles were determined by inverse gas chromatography techniques, and inherent agglomeration indexes for the pigments were measured by an application of powder rheology principles. It was found that those rutiles with high agglomeration indexes or those with highly basic surfaces interfered the most with the processing additive. Mechanisms by which rutile dispersibility and acid-base character influence the effectiveness of the fluorocarbon elastomer processing additive are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760301604
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  • 5
    Electronic Resource
    Electronic Resource
    Rheological properties of corona modified cellulose/polyethylene composites (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1734-1739 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The rheological behavior of wood fiber/polyethylene composites made of corona treated constituents was investigated. Corona treatment of one or both of the constituents resulted in decreased melt viscosities relative to compounds containing untreated materials. The reduction of melt viscosity may originate from low molecular weight moieties formed on the surfaces of both polyethylene and cellulose during corona treatment. These may act as lubricants at interfaces. Also it was found that the corona treatment of fibers leads to higher packing volumes; this may result from a reduction in fiber length when treated fibers are processed under high shear conditions. As a result these fibers perturb the normal flow pattern in the melt to a lesser degree than the longer fibers of untreated cellulose.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322212
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of polymer structure on the onset of processing defects in linear low density polyethylenes (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1581-1589 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Linear low density polyethylenes are manufactured by copolymerizing ethylene with 1-alkenes, yielding a linear polyethylene backbone with short side chains. Due to the nature of the catalyst used in the polymerizaton, multimodal branching distributions are typically obtained. In this report, we have investigated the processability of four 1-octene linear low density polyethylenes as a function of the short chain branching distribution. Analytical techniques such as 13C nuclear resonance spectroscopy, size exclusion chromatography, differential scanning calorimetry, and temperature rising elution fractionation, in particular were used to elucidate the molecular structure. Processability measurements were made using various extrusion techniques and dynamic mechanical analyses.It was determined that in the absence of any variations in molecular weight, the polymers with the higher proportions of linear polyethylene showed inferior processability In terms of onset of surface imperfections at lower extrusion rates. Polymers with worse processability characteristics also exhibited higher zero shear viscosities.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760312205
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  • 7
    Electronic Resource
    Electronic Resource
    Mechanical properties of corona-modified cellulose/polyethylene composites (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 343-346 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of corona treating the surfaces of components on tensile properties of wood fiber linear low-density polyethylene composites has been investigated. Corona treatment results in a significant increase in strength properties of the composites. Yield stress increases after treatment of one or both of the composite components. Pronounced improvement in ductility has been observed for composites containing 15 to 30% of the corona modified fiber. Relevant mechanisms involved are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760330606
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  • 8
    Electronic Resource
    Electronic Resource
    Component interactions and properties of crosslinked vinyl systems (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 981-988 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Compositions based on poly(vinylchloride) (PVC) containing diisodecyl phthalate (DIDP) or trioctyl trimellitate (TOTM) plasticizers and, in several cases, also containing chlorinated polyethylene (CPE) as property modifier were cross-linked by γ irradiation, using a trifunctional acrylic cross-linking agent. Cross-linking effectiveness was analyzed by solvent swelling data, and the effects of irradiation up to dosages of about 10 Mrad on the mechanical properties of the systems were recorded. The interaction potential of components used in these systems was determined by recently developed methods of inverse gas chromatography (IGC). These classify PVC and CPE as electron acceptors and the plasticizers as donors. Expectedly, increased moduli and decreased elongational properties follow exposure to γ-rays. The plasticizers reduce the effectiveness of cross-linking, the magnitude of the reduction being related to the degree of acid-base interaction between PVC and plasticizing fluids. Interference with cross-linking mechanisms thus is a function of the solvent power of the plasticizers. CPE competes with PVC for plasticizer so that for given quantities of DIDP or TOTM, the fraction available to solubilize the host polymer is reduced. In compounds with CPE, therefore, the cross-linking effectiveness of irradiation is raised, consistent with the acid-base balance of Interactions, as given by the IGC results. Twin yield points have been observed in the stress-strain curves of compounds containing CPE. It is postulated that distinct, interpenetrating cross-link networks are formed when these polymers are subjected to γ irradiation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760301607
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  • 9
    Electronic Resource
    Electronic Resource
    Flow defects in linear low density polyethylene processing: Instrumental detection and molecular weight dependence (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1524-1531 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An elongational rheometer coupled with a primary extrusion device has been used for the detection of flow limitations in the extrusion of linear low density polyethylenes (LLDPE). The shear rate for the onset of flow defects (fd) was found to decrease with increasing branch length in the LLDPE copolymer, but the severity of fd was greater in butene- than in hexene- and octene-copolymers. Studies of partially fractionated LLDPE showed that the critical shear rate for the onset of fd was closely related to the minimum molecular weight in the distribution of molecular weights. In addition, evaluations of bond strengths in LLDPE/metal joints showed that the same molecular weight parameter significantly affected that performance criterion. In combination, the experimental findings provided confirmation of sporadic adhesive failure (slip/stick effect) as the mechanism responsible for the occurrence of observed flow defects. Its manifestation is attributable to the thermodynamic drive that promotes the preferential localization of low molecular weight moieties at surfaces and at interfaces of polyolefins such as LLDPE.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760332303
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  • 10
    Electronic Resource
    Electronic Resource
    Component interactions and properties of crosslinked vinyl systems (1991)
    Brookfield, Conn. : Wiley-Blackwell
    Journal of Vinyl and Additive Technology 13 (1991), S. 67-72 
    Details
    ISSN: 0193-7197
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Compositions based on PVC, containing DIDP or TOTM plasticizers, and in several cases also containing chlorinated polyethylene (CPE) as property modifier, have been crosslinked by irradiation, using di- and tri-functional acrylic crosslinking agents. Crosslinking effectiveness has been analyzed by solvent swelling data, and the effects of irradiation up to dosages of about 10 Mrad on the mechanical properties of the systems have been recorded. The interaction potential of components used in these systems has been determined by recently-developed methods of inverse gas chromatography (IGC). These classify PVC and CPE as electron acceptors, and the plasticizers as donors. Expectedly, increased moduli and decreased elongational properties follow exposure to gamma-rays. The plasticizers reduce the effectiveness of crosslinking, the magnitude of the reduction being related to the degree of acid/base interaction between PVC and plasticizing fluids. When present, CPE competes with PVC for plasticizer so that for given quantities of DIDP or TOTM, the fraction available to solubilize the host polymer is reduced. In compounds with CPE, therefore, the crosslinking effectiveness of irradiation is raised, consistent with the acid/base balance of interactions, as given by the IGC results. Twin yield points have been observed in the stress-strain curves of compounds containing CPE. It is postulated that distinct, interpenetrating crosslink networks are formed when these polymers are subjected to gamma irradiation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/vnl.730130111
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