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Due to its excellent mechanical, physical, and chemical properties, polyethylene is being widely used as a substitute for conventional metal pipes. Especially, in the case of polyethylene pipes, it is very important to secure long-term lifetime, therefore, various standard test methods to evaluate long-term lifetime with various fracture mechanisms have been proposed in ISO or ASTM. Among various failure mechanisms of pipe-grade polyethylene materials, slow crack growth (SCG) may be frequently occurred in actual filed conditions, so various standard test specimens such as PENT, FNCT, CRB have been developed to evaluate SCG characteristics. However, the existing SCG tests are reported to be difficult to evaluate SCG properties of the recently developed pipe polyethylene material in time due to technical issues, and to overcome these issues, a new test specimen, Stiffness-Constant K (SCK) specimen, has been recently proposed. In this study, CRB and SCK specimens were used to evaluate the integrity of polyethylene pipes that were damaged during portable water transportation. The CRB test was used for the evaluation of crack initiation characteristics of the pipe, and the SCK specimen was used for evaluating SCG characteristics of the pipe. The SCG characteristics of the damaged polyethylene piping materials were compared with the regular polyethylene materials to analyze the root causes of the failure of the polyethylene piping materials in use.
Quantification of Low Molecular Weight Oligomers in Polyolefin Products for Food Packaging and Hygiene Application Trace amounts of low molecular weight aliphatic polyolefin oligomer or LMWO (less than a few percent) exist in many polyolefin products such as polyethylene (PE), polypropylene (PP) and propylene-ethylene copolymers. These low molecular weight (MW) chemicals either are volatile or readily migrate out of the bulk polymer. Many governments such as US, China and EU require strict compliance with the legal maximum amount of LMWO content present in these products. In the past, quantification of LMWO content mainly relied on gas chromatography (GC). However the upper limit of LMWO MW that can be measured by GC is less than 1000 Dalton while LMWO with MW around 2000 Dalton is also a regulatory concern. In addition, due to the semi-crystalline nature of these polymers, the GC measurement of LMWO is significantly influenced by sample preparation method, and thus carries great uncertainty. High Temperature Gel Permeation Chromatography (GPC) with band-filter based infrared detector, a new GPC technique emerging in the market in recent years, provides an excellent opportunity to characterize polyolefins of both low and high MW due to high sensitivity and excellent linearity of detector response. In this paper, we demonstrate that the LMWO in propylene-ethylene copolymer (Vistamaxx™ polymer) and PE homopolymer can be accurately quantified through a methodology developed with GPC-IR by a comprehensive analysis on the effects of all kinds of noise factors and a new way of column calibration. Excellent results have been achieved. Quantification of fractions with MW less than 500 by GPC-IR are compared with GC and are generally consistent. The method of using GPC-IR for the quantification of LMWO in lieu of GC has not been reported else where. Due to the broader MW range detectable by GPC-IR over GC, it can be expected that this new method will become very useful for polyolefin society as regulations become more and more stringent. As a complementary tool for GC, this method could also be developed into a standard protocol widely available to the industry for quantification of LMWO in polyolefin materials.
In polyolefins industry, reliable flow of powder/resin through degassers and purge columns is of high importance. It is directly connected to purging performance. If flow problems occur in degassers and/or purge columns, volatile organic compounds (VOCs) in the product can exceed specifications. Cross-contamination between grades can also occur during grade changeover. The system may experience limitations on the maximum discharge rate that can be achieved. In extreme cases, the system may need to be shutdown if resin bridges/arches over the outlet of the purge column, highlighting importance of reliable flow through a purge column. Scientific techniques are available to characterize the flow behavior of a resin/fluff/powder in degassers and purge columns. This paper will focus on the characterization methods to determine solids flow behavior in processing vessels. These methods are based on proven direct-shear techniques which consider the friction and cohesiveness of solids as a function of consolidation pressure on the solids. Such characterization is conducted at several different consolidation pressures, to cover the expected range in the degasser. This testing is not qualitative rather it is quantitative. It provides a basis to determine important geometric features of degassers and purge columns to achieve reliable flow without arching, buildup, or discharge-rate limitation. This paper will describe details of the characterization methods, and its use for designing and/or modifying a degasser/purge column.
Block copolymers (BCP) synthesis often results in a complex polymer mixture containing the desired BCP as well as one or both parent blocks. Interactive liquid chromatography separation of parent blocks from BCP is typically challenging, because the parent blocks are structurally the same as the blocks contained within the BCP. In this presentation, we first present the fundamental studies of liquid chromatography with preloaded adsorption promoting solvent barriers to overcome this challenge for the separation of a model BCP. The approach was then leveraged to the separation of olefin block copolymers (OBC). The OBC contains a “hard-soft’ block OBC with a high density polyethylene (HDPE) block and a relatively low density polyethylene (VLDPE) block targeted as thermoplastic elastomers. One of the major challenges is to fractionate HDPE segments from the other components (block copolymers and VLDPE segments). In this work we have overcome this challenge by using liquid chromatography with preloaded adsorption promoting barriers. A solvent plug (barrier) is introduced in front of the sample which specifically promotes the adsorption of HDPE segments on the stationary phase (porous graphitic carbon). Under selected thermodynamic conditions, VLDPE segments and block copolymer chains crossed the barrier while HDPE segments followed the barrier solvent and thus enabled separation. The barrier solvent composition was optimized and the chemical composition of fractionated polymer chains was investigated as a function of barrier solvent strength using an online Fourier-transform infrared (FTIR) detector. Our study revealed that both the HDPE segments as well as asymmetric block copolymer chains (HDPE block length >> VLDPE block length) are retained in the separation and the barrier strength can be tailored to retain a particular composition. At the optimum barrier solvent composition, this method can be applied to separate effective HDPE segments from the other components.
Isoprene rubber, while extensively used in the tire and footwear industries, has limited applications due to its poor resistance to heat, UV and ozone, and low glass transition temperature. Such limitations can be improved by adding elastomeric polyolefins (composed of saturated hydrocarbons) to the polydiene rubber. Random copolymers of polyethylene and poly(ethyl ethylene) (PE-co-PEE) exhibit tunable glass transition temperatures. The addition of PE-co-PEE to 1,4-polyisoprene (PI) might potentially improve rubber performance. In order to provide quantitative guidance for such blends of olefin and diene elastomers in product design, the thermodynamic interactions between PI and PE-co-PEE were quantified via small angle light scattering (SALS) and small angle neutron scattering (SANS). PI was partially saturated with hydrogen to various extents (20-80%), which produced copolymers of PI and poly(ethylene-alt-propylene) (PI-co-PEP), to lower the critical point in the blends with PE-co-PEE. In this way, the cloud points (by SALS) could be observed in an accessible temperature range and SANS data could be collected within the homogeneous state. Temperature dependencies of the apparent interaction parameter (χ) were well described by the random copolymer theory (RCT) and χ of the homopolymer pairs (PI/PEE, PI/PE, PEP/PEE) were extracted. The χ parameter between PE-co-PEE and PI-co-PEP decreased dramatically as the PEP content (i.e. olefin content) in PI-co-PEP was increased.
High demands for polyolefins sample throughput necessitate optimization of chromatography systems for speed, often at the cost of resolution. Universal Calibration techniques in high-temperature SEC are especially sensitive to column resolution due to the increased slope of the product, IVxM, which is steeper than a traditional calibration against backbone molecular weight. Moreover, optimization methods must be included to preserve data relative to band-broadening effects between higher speed and higher resolution systems. Herein, we examine the use of analytical SEC columns as we balance shear rate effects and resolution versus run time for a Universal calibration system including both LDPE and HDPE samples. A methodology of comparing resolution enhancements and dilution effects versus number and type of GPC columns will be presented.
K. Tarverdi | P. Allan | P. Marsh | J. Silver, December 2019
This report is an account of a project that went under name ‘Light AND Sound’ or the acronym ‘LANDS’. The objective was to investigate the potential use of recycled and waste materials in automotive components. Five components were selected for the investigation. All of them had the potential to be manufactured from waste and recycled materials. The trial materials which included recycled polypropylene and a particulate industrial solid waste stream, were processed into prototype components that were evaluated and compared with the respective production counterparts. Finally a life cycle assessment was carried out for each prototype component that was also compared with the current part. The overall results indicated a clear potential for the use of the project materials in their respective application.
Antimony Trioxide remains invaluable as a flame retardant synergist for PVC and for halogen flame retardant systems. A complete replacement has yet to be found and is unlikely to be found.
The lengthy timeframe for materials to move from discovery to market is due in part to the continued reliance of materials research and development programs on scientific intuition and trial and error experimentation. Much of the design and testing of materials is currently performed through time-consuming and repetitive experiment and characterization loops.
J. Weingart | M. Jakupca | J. Lance | C. Phillips | J. Regula, October 2019
VOC Reduction via Phosphite Design: Remove phosphites that contain phenol as a ligand (such as DiDP and DPiD phosphites). Use phosphites with higher boiling ligands and that are of higher MW.; Use more hydrolytically/thermally stable phosphites (larger aryl and more hydrophobic aryl groups sterically hinder water from attacking the phosphorous and provide better thermal stability).
Rheology: The study of the flow and deformation of matter. Flow: Fluid Behavior; Viscous Nature: F = F(v); F ≠ F(x). Deformation: Solid Behavior Elastic Nature: F = F(x); F ≠ F(v). Viscoelastic Materials: Force depends on both Deformation and Rate of Deformation and vice versa.
Mixing: Key to Successful Compounding of Filled and Reinforced Polymers. Mixing: What is it? Intimate blending of two or more ingredients to make a new material formulation that has certain predefined properties. – Mineral fillers – glass fibers – Impact modifiers – Pigments – Difficult to handle materials or additives
Blending vs. Melt Mixing. Blending - the intimate intermingling of ingredients without phase change; Melt Mixing - the intimate intermingling of ingredients with a phase change.
Acrylic Impact Modifiers: ● Core / Shell impact modifier design ● Modes of failure and formulation ● Processing and impact performance;
Acrylic Process Aids: ● Process aid chemistry and functionality ● Selecting process aid technology ● Applications in semi-rigid and flexible PVC;
PVC Formulation by market segment: ● Rigid weatherable ● Substrate ● Cellular PVC.
T. Seibel | S. Cockett | A. Eichholzer | S. MacDonald, October 2019
What is sustainability? the ability to be maintained at a certain rate or level; avoidance of the depletion of natural resources in order to maintain an ecological balance; Sustainability is most often defined as meeting the needs of the present without compromising the ability of future generations to meet theirs. It has three main pillars: economic, environmental, and social. These three pillars are informally referred to as people, planet and profits.
Determining the Fusion of PVC Standard methods include: • ASTM D2152 – Standard Test Method for Adequacy of Fusion of Extruded Poly(Vinyl Chloride) (PVC) Pipe and Molded Fittings by Acetone Immersion; • ISO 9852 Unplasticized poly(vinyl Chloride) (PVC-U) pipes – Dichloromethane resistance at specified Temperature; • No ASTM Standard for use of Differential Scanning Calorimetry to determine Degree of Fusion of PVC; • Numerous papers have been published on the use of DSC to determine the degree of fusion of PVC ( Gilbert & Vyvoda "Thermal Analysis Technique for investigating the Gelation of Rigid PVC Compounds" 1981) (Vanspeybroeck & Dewilde "Determination of the Degree of Gelation of Rigid PVC Compounds" 2007) and others.
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Any article that is cited in another manuscript or other work is required to use the correct reference style. Below is an example of the reference style for SPE articles:
Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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Note: if there are more than three authors you may use the first author's name and et al. EG Brown, H. L. et al.
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