Polyethylene Compounds Research Articles

Botanical characteristics, pharmacological effects and medicinal components of KoreanPanax ginsengC A Meyer

Korean Panax ginseng C A Meyer is mainly used to maintain the homeostasis of the body, and the pharmacological efficacy of Korean ginseng identified by modern science includes improved brain function, pain-relieving effects, preventive effects against tumors as well as anti-tumor activity, enhanced immune system function, anti-diabetic effects, enhanced liver function, adjusted blood pressure, anti-fatigue and anti-stress effects, improved climacteric disorder and sexual functions, as well as anti-oxidative and anti-aging effects. Further clinical studies of these pharmacological efficacies will continue to be carried out. Korean ginseng is found to have such main properties as ginsenoside, ployacetylene, acid polysaccharide, anti-oxidative aromatic compound, and insulin-like acid peptides. The number of ginsenoside types contained in Korean ginseng (38 ginsenosides) is substantially more than that of ginsenoside types contained in American ginseng (19 ginsenosides). Furthermore, Korean ginseng has been identified to contain more main non-saponin compounds, phenol compounds, acid polysaccharides and polyethylene compounds than American ginseng and Sanchi ginseng.

A new approach to the statistical enlargement law for comparing the breakdown performances of power cables - part 2: application

A new theoretical approach to the application of the enlargement law for assessing the breakdown performances of shielded power cables was illustrated in the companion paper (Part 1) of this series. In the present paper, practical case-studies of the proposed theory are presented. The so-called crossing quantities of two cable lines, i.e. crossing length, crossing dielectric strength and crossing breakdown voltage, are analyzed on the basis of the results of dielectric strength tests performed on cable models insulated with different commercial compounds. In particular, the application is relevant to mini-cable samples realized with two ethylene-propylene rubber (EPR) compounds, and with two cross-linked polyethylene (XLPE) compounds, all subjected to standard lightning impulse dielectric strength tests. The estimation of the crossing quantities, performed for various power cable voltage ratings, shows that the crossing length - if any - is a strong function of the cable size and voltage rating. Thus the choice of the best compound should be based on a comparison between the value of crossing length and the typical lengths of full-size cables. Furthermore, since the crossing quantities are strongly affected by the values of the Weibull parameters estimated from the dielectric strength tests, a sensitivity analysis of such quantities to the uncertainty in the estimation of the Weibull parameters is also carried out.

A New Approach to the Statistical Enlargement Law for Comparing the Breakdown Performance of Power Cables. 1. Theory

This paper, the first of two companion papers, describes a new approach to the application of the statistical enlargement law to power cable insulation. The results of this work allow for selecting better insulation for medium or high voltage cables. The selection is based on the results of dielectric strength tests performed on cable models or full size cables of a limited length. The relevance of the so-called crossing length, where one insulating compound performs better below it and another compound above this length, is discussed. The proposed theory was used to analyze the performances of two ethylene-propylene rubber (EPR) compounds and two cross-linked polyethylene (XLPE) compounds. The results are presented in the companion paper.

Polyethylene compounds with antimicrobial surface properties

The present study aims at antimicrobial polyethylene surfaces. To achieve this, LLDPE was compounded with the polymeric biocide poly(2- tert-butylaminoethyl) methacrylate TBAM (bulk modification with 1.5–5.0 wt.% of TBAM). Surfaces of these polymer compounds were then subjected to microbial assays. Using standard methods the colony forming units (CFU) for Escherichia coli and Staphylococcus aureus were determined on these surfaces. In all cases, polyethylene surfaces with highly antimicrobial properties were achieved. An average reduction of 10 4 CFU ml −1 compared to neat LLDPE was achieved. The surfaces of these LLDPE/TBAM compounds were assessed by electrokinetic (zeta potential) measurements. The results indicate a relation between the antimicrobial activity and the zeta-potential of the polymer compounds. Moreover, the antimicrobial compounds were investigated towards biofilm formation. Compared to pristine LLDPE, the surfaces of the polymer compounds showed less adhering biofilm after a testing period of 16 weeks.

TERAHERTZ QUALITY CONTROL OF POLYMERIC PRODUCTS

We report on experiments that evaluate the potential of terahertz (THz) time-domain spectroscopy (TDS) for quality control of polymeric compounds. We investigate specimens out of a polyethylene compound with silver-coated titanium dioxide nanospheres and a glass-fiber reinforced epoxy composite. We further examine an industrial polymer product produced by injection molding. Our data demonstrates that THz imaging is a powerful tool for contactless quality control in the polymer industry.

Non Linear Rheology for Long Chain Branching characterization, comparison of two methodologies : Fourier Transform Rheology and Relaxation.

In this study we compare three rheological ways for Long Chain Branching (LCB) characterization of a broad variety of linear and branched polyethylene compounds. One method is based on dynamical spectrometry in the linear domain and uses the van Gurp Palmen plot. The two other methods are both based on non linear rheology (Fourier Transform Rheology (FTR) and chain orientation/relaxation experiments). FTR consists in the Fourier analysis of the shear stress signal due to large oscillatory shear strains. In the present work we focus on the third and the fifth harmonics of the shear stress response. Chain orientation/relaxation experiment consists in the analysis of the polymer relaxation after a large step strain obtained by squeeze flow. In this method, relaxation is measured by dynamical spectrometry and is characterized by two relaxation times related to LCB. All methods distinguish clearly the group of linear polyethylene from the group of branched polyethylene. However, FTR and Chain orientation/relaxation experiments show a better sensitivity than the van Gurp Palmen plot. Non linear experiments seem suitable to distinguish long branched polyethylene between themselves.

Radiolytic unsaturation decay in polyethylene. Part III—the effect of certain chain transfer agents

Small amounts of certain halogenated compounds are found to have, at most, only a slight enhancing effect on the radiolytic decay rates of added poly-unsaturated compounds in polyethylene, but significantly increase the elastic modulus at 433 K (melt modulus) obtained thereby. Experiments with model chlorine-containing additives suggest that this increase is due to a more random distribution of polymer and monomer mediated crosslinks in the polymer, that it does not result from a significant increase in crosslinking and that it is mediated by chlorine atoms, in a similar manner to radiolytic hydrogen atoms, through facilitation of long range free radical migration. Although low molecular weight chloro-paraffins inhibit radiolytically induced growth of melt modulus in monomer containing polyethylenes, even very small additions of chlorinated polyethylenes, which form a separate phase, increase the melt modulus. This again indicates that the active species is the chlorine radical.

Surface modified aluminium hydroxide in flame retarded noise damping sheets

AbstractFlame retarded polyethylene compounds were prepared using a series of aluminium hydroxide of different particle size applying a milling processes and special precipitation technologies. The processability and flame retardant efficiency of the flame retarded systems were compared. The effects of various surface modifications were analysed in case of one selected type of aluminium hydroxide. A silicone terminated reactive surfactant promoted not only the processability but also the flame retardant efficiency. Noise damping sheets were prepared by simultaneous application of aluminium hydroxide and barium sulphate in an elastomer blend matrix. V0 flame retardant grade could be achieved this way accompanied with improvement in the acoustic properties and maintenance of the mechanical properties.

불소처리된 카본블랙을 충전한 HDPE 기지 컴파운드의 PTC/NTC 특성에 관한 연구

본 연구에서는 PTC 소자의 NTC 현상을 제거하기 위하여 카본블랙을 0.1-0.4 MPa의 압력으로 불소처리 한 후 이를 이용하여 카본블랙/HDPE 전도성 컴파운드를 제조하였다. 불소처리한 카본블랙의 표면특성 변화는 FT-IR, XPS 그리고 접촉각 측정을 통하여 확인하였다. FT-IR실험 결과, 불소처리된 카본블랙은 1400-1000 cm<TEX>$^{-1}$</TEX> 영역에서 C-F 피크를 나타내며 처리압력이 증가할수록 C-F 피크의 세기가 증가함을 확인할 수 있었다. 또한, XPS 분석을 통해 불소처리 압력이 증가할수록 카본블랙 내의 불소의 함량이 증가함을 확인하였다. 그러나, 불소처리된 카본블랙의 표면자유에너지는 처리압력이 증가할수록 감소하였다. 결과로서, 카본블랙의 불소 처리를 통해 카본블랙/HDPE 컴파운드의 NTC 현상이 사라졌는데, 이는 카본블랙의 표면자유에너지 감소가 수지의 융점 이후 일어나는 카본블랙 입자간의 재결합을 방해하기 때문이라 사료된다. In this study, the fluorinated carbon blacks(CB) were used to reduce the negative temperature coefficient (NTC) phenomenon of the CB-filled high density polyethylene(HDPE) compounds in the fluorination pressure of 0.1-0.4 MPa. The changes in surface properties of the CB were investigated by using FT-IR, XPS and contact angle measurements. From the FT-IR results, the fluorinated CB showed the C-F absorption peak at 1400-1000 cm<TEX>$^{-1}$</TEX> and the peak intensity was increased with increasing the fluorination pressure. Also, the analysis of XPS spectra of the fluorinated CB indicated that fluorine content was increased with increasing the fluorination pressure. Meanwhile, the surface free energy of the fluorinated CB was decreased with increasing the fluorination pressure. Consequently, the increase of fluorine contents on CB made a disappearance of NTC behaviors of CB/HDPE compounds, which was probably due to the reduction of CB reaggregation after melting point of the HDPE, resulting from decreasing the surface free energy of CB particles.

Preparation and properties of heat‐shrinkable cross‐linked low‐density polyethylene

AbstractIn this work, heat‐shrinkable characteristics of a polyethylene compound were obtained by blending mixtures of low‐density polyethylene with varying amount of peroxide. These were then extruded and molded to the required shape and then cross‐linked by chemical means, followed by heating and stretching and then cooled to “freeze‐in” the oriented polymer structure (elastic memory). A decrease in the melting point and heat of fusion (ΔHf), as determined from the DSC melting enthalpies, was observed with an increase in the dicumyl peroxide (DCP) concentration. Tests on the heat shrinkablity of the samples showed that the stretching temperature has a large effect on the shrinkage temperature. The results showed that by increasing the peroxide content, the shrinkage temperature was decreased. The elongation at break decreased with an increase in the DCP concentration. Increasing the temperature in lightly cross‐linked samples (low percent DCP) resulted in a reduction in the elongation at break. Increasing the cross‐linking density (DCP content) gave an opposite effect. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 112–119, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10041

Wall effects on flow of polymer/particulate/(carboxylic acid) in dies and rheometers

The addition of carboxylic acids to polyolefins results in an apparent slippage flow along rheometer and die walls. In this article, we seek to extend this investigation to polymer/particulate compounds. An experimental study on the influence of carboxylic acid additive in polyethylene/filler and polystyrene/filler compounds in rheometers is described. Capillary and cone-plate experiments are reported. A series of particle fillers of varying character, including carbon black, calcium carbonate, zinc oxide, and talc are compared. The aliphatic fatty acid, octadecanoic acid, was used as an additive. Significant viscosity reductions were observed. The greatest effects were found in polyethylene/(carbon black) and polystyrene/(calcium carbonate) compounds. All of the polyethylene compounds exhibited slip flow, but the polystyrene compounds did not. Apparently much of the octadecanoic acid was interacting with the polar particle fillers and not with the die wall. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 651–658, 2004

Spiking of performance reference compounds in low density polyethylene and silicone passive water samplers

A method for spiking performance reference compounds (PRCs) into low density polyethylene (LDPE) and silicone polymers is described. This method is based on equilibration of the polymers in aqueous/methanolic solutions of PRCs. Equilibration times range from minutes to hours for perdeuterated polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) with a hydrophobicity in the range 3.9<log K ow<7.7. Best results were obtained for methanol–water ratios of 80/20 (v/v). The method allows for the use of PRCs for in situ calibration of the uptake kinetics of these solvent-free sampling phases in a similar way as for semipermeable membrane devices (SPMDs).

STRUCTURE–PROPERTY RELATIONSHIP IN FLAME RETARDANT POLYMERS

Mg(OH)2 and ammonium polyphosphate (APP) based flame retarded polyethylene (PE) and polypropylene (PP) compounds were prepared in a plastograph and the influence of additive systems on the microstructure, mechanical, and melt characteristics of the compounds was investigated by DSC, Raman microscopy, and rheological measurements. A high loading of Mg(OH)2 has a nucleating and crystallinity reducing effect in low density PE. The crystallinity reducing effect was explained by formation of a partially ordered but noncrystallized interfacial region around the flame retardant (FR) particles. The nucleating effect was hindered when the particles were embedded in elastomer. The nucleating effect of APP in PP was also reduced when a polyol layer surrounded it. The incorporation of boroxo siloxane (BSil) elatomer FR synergist, introduced additionally to the above additives, resulted in a further nucleating effect, and increased the melt viscosity. Polymer layered montmorillonite, applied instead of BSil elastomer, did not influence the crystallization; however, it increased the melt viscosity and improved the flame retardancy.

Polyethylene compounds containing mineral fillers modified by acid coatings. 2: Factors influencing mechanical properties

AbstractHigh molar mass medium density polyethylene (MDPE) compounds containing magnesium hydroxide filler, surface‐treated by a range of fatty acid coatings of variable aliphatic chain length were injection molded and subjected to mechanical property evaluation. Surface treatment modifies yield stress and modulus, with property maxima observed close to the monolayer coverage. Acid‐group terminated polyethylene (ATPE) coalings produced the highest yield stress, as a result of physical interaction with the matrix polymer. Retention of high‐energy, ductile mode impact failure of unfilled MDPE was obtained when using short‐chain decanoic acid coating, as a result of enhanced dispersion and reduced particle‐matrix interactions promoting microscopic matrix yielding. A mechanism for enhanced Mg(OH)2 particle dispersion based upon surface energy and molecular adsorption has been proposed, which is consistent with the properties data derived. Fractographic analysis (SEM) has confirmed the predominance of matrix yielding in compounds exhibiting enhanced impact resistance, while X‐ray pholoelectron spectroscopy (XPS) has also highlighted a different crack growth mechanism in MDPE compounds containing coated fillers, which are less prone to agglomeration. In addition, thermomechani‐cal history during processing also modifies physical properties of MDPE/Mg(OH)2 composites to some extent. Anisotropic effects include molecular orientation and filler particle alignment induced by shear stress during injection mold filling, which predominate in compounds containing coated fillers. Overall, the application of organo‐acid coatings reduces polymer‐particle surface interaction and thermody‐namic work of adhesion, leading to improved dispersion and enhanced properties. Appropriate property balances can be tailored by judicious selection of aliphatic chain length and addition level of fatty acid filler coatings.

Study of fusion percolation thresholds of rigid PVC compounds

AbstractRigid poly(vinyl chloride) (PVC), PVC/chlorinated polyethylene (CPE), and PVC/CPE/oxidized polyethylene (OPE) compounds were prepared in a Haake torque rheometer. The fusion percolation thresholds (FPTs) of these compounds were defined and compared. Moreover, the fusion curves of these compounds were illustrated and compared. A higher processing temperature resulted in a shorter fusion time and a lower FPT. For PVC/CPE compounds, a higher concentration of CPE could decrease the FPT and promote PVC particles to fuse together easily. Meanwhile, in the beginning of the fusion process, the interaction between a higher concentration of OPE and calcium stearate in PVC/OPE compounds could also promote an easy fusion of the PVC particles. For PVC/CPE/OPE compounds, the synergistic interaction among CPE, OPE, and calcium stearate resulted in the shortest fusion time and the lowest FPT. The FPTs of rigid PVC samples were strongly dependent on not only the processing conditions but also the formulations of the samples. © 2001 John Wiley &amp; Sons, Inc. J Appl Polym Sci 81: 3022–3029, 2001

In-Process R eometry Studies of LDPE Compounds

Abstract The initial part of a comprehensive study into the investigation and validation of in-process measurements on a low density polyethylene (LDPE) compound during extrusion is reported. An unfilled, commercial grade of low density polyethylene was processed using fully instrumented, computer monitored, single and twin screw extruders in the Interdisciplinary Research Centre (IRC) laboratories, University of Bradford. Three in-process rheometers were used; a prototype Rosand capillary on-line rheometer (OLR), a four sensor slit die in-line rheometer (ILR) and a six sensor slit die ILR. Off-line comparisons were carried out using a Rosand RH twin bore capillary rheometer. All devices allowed shear ow characterisation at a range of processing rates, and the capillary rheometers also provided a measurement of entry pressure drop through the use of orifice dies. The six-sensor ILR also allowed measurement of entry pressure drop into the slit, although the differences in ow geometry meant these measurements were not directly comparable with the capillary devices, and exit pressures were extrapolated from ILR pressure drops. The in-process devices exhibited very good agreement with measurements made off-line, in both shear ow and entry pressures. In-line slit die measurements were very close to those made using capillary dies, despite the in-line tests being non-isothermal and employing a different geometry of measurement section. Differences in melt rheology between single and twin extrusion were observed, due to the amount of mechanical work input by each extruder. Overall, good agreement was observed from the four different routes to measurement, for the LDPE examined.

In-Process R eometry Studies of LDPE Compounds

Abstract The second part of a comprehensive study into the investigation and validation of in-process measurements on a low density polyethylene compound during extrusion is reported. A commercial grade of branched low density polyethylene was used in the study, compounded with various levels of magnesium hydroxide ame retardant filler, up to 0 by weight. In-line and on-line rheometry were used to monitor melt ow behaviour during single screw and twin screw extrusion; off-line capillary rheometry was performed on the compound before and after extrusion, to examine any change in rheology. Morphological observations were made using scanning electron microscopy, and molecular characterisations carried out using gel permeation chromatography. In-process rheometry was found to be able to detect the presence of filler at low and high loadings, but was unable to discriminate between intermediate levels. Off-line rheometry indicated that twin screw extrusion altered the rheology of the compound, and capillary wall slip was found to increase after extrusion. Morphological observation indicated that filler in the compound was better dispersed after extrusion, especially at high volume fractions. Molecular weight and polydispersity of the LDPE were shown to increase after extrusion, more so in the case of low filler loadings. Overall, in-process measurements provided useful rheological data, and the compound was found to exhibit complex, process-dependent rheology.

REVIEW OF VOLATILE ORGANIC COMPOUNDS DERIVED FROM POLYETHYLENE

The formation of volatile organic compounds (VOCs) in polyethylene (PE) is a topic of concern to industries involved in the packaging of items such as foodstuffs and pharmaceuticals that are sensitive to organoleptic contamination. This article reviews the available literature on VOCs that originate from PE during its manufacture, processing, storage, and service life. The package–product interactions that may occur between PE and packaged foodstuffs are also considered together with the wide range of methods for the analysis of VOCs. The following analytical methods are discussed: (i) sensory evaluation, (ii) chromatographic techniques and their associated sampling techniques, including the “hot-jar” method and dynamic headspace sampling, (iii) gas chromatography–olfactory sensing, and (iv) artificial olfaction or “electronic nose” technology.

Polyethylene compounds containing mineral fillers modified by acid coatings. 1: Characterization and processing

AbstractResearch has been carried out to determine the effect of filler coatings on the processing properties of medium density polyethylene (MDPE) modified by an ultrafine grade of flame‐retardant magnesium hydroxide (Mg(OH)2) filler. Selected filler coatings were acid‐group terminated and were of varying aliphatic chain length. The filler dry‐coating process has been optimized by characterizing the reaction between Mg(OH)2 filler surface and the acid group, using spectroscopic techniques including Fourier transform infrared (FTIR) and X‐ray photoelectron spectroscopy (XPS). Using immersion calorimetry, the interactions between the fillers and the polyolefin matrix were shown to decrease on the addition of a fatty‐acid coating. Compounding torque and specific energy data relate to filler dispersion; qualitative analysis has demonstrated how the coatings provide a reduction in both size and number of particle agglomerates. MDPE compound processability was assessed by capillary rheometry; wall slip was evident in compounds containing uncoated Mg(OH)2 filler. Consequently, the development of molecular orientation of the polymer during injection mold filling, quantified by a reversion analysis, is modified by the effects of filler coating chain length and addition level, an effect that has important implications to link the mechanical properties of MDPE‐Mg(OH)2 composites to processing history.

Extensional flow characterisation and extrusion blow moulding of high density polyethylene modified by calcium carbonate

Free surface elongational flow properties, including transient state stress growth and melt rupture data, have been measured on a range of calcium carbonate filled high density polyethylene (HDPE) compounds, using a Rutherford elongational rheometer operating at constant strain rate in the range 0·1–6·0 s-1. Results show that polymer molecular weight has a strong influence on both tensile stress growth and melt rupture data; in creasing elongational strain rate decreases the stress growth coefficient, in all compounds. At any specific elongational strain rate, the stress growth coefficient increases with volume fraction of particulate additives and also when using additives of fine particle size, as a result of packing fraction effects. Acid coatings added at super-monolayer levels influence the viscosity of highly filled compounds, by internal lubrication.Dynamic extrusion data obtained by experimental blow moulding of calcium carbonate modified HDPE materials show that modifications to melt state shear modulus result in reduced die swell, to an extent determined by filler coating. In combination with die swell, higher extensional viscosity of filled HDPE contributes significantly to enhanced parison sag resistance. Solid state modulus enhancement was consistently observed in calcium carbonate filled HDPE containers and if excellent filler dispersion can be achieved, it is feasible to retain the ductile mode failure of unfilled HDPE when containers are subjected to high velocity impact loads.