The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform

Charles M Hansen - One of the best experts on this subject based on the ideXlab platform.

  • on predicting Environmental Stress Cracking in polymers
    Polymer Degradation and Stability, 2002
    Co-Authors: Charles M Hansen
    Abstract:

    Abstract Environmental Stress Cracking (ESC) is shown to correlate well using a plot of the RED number (polymer–solvent interaction) found from Hansen solubility parameters (HSP) versus a molecular size parameter, the molar volume, V . These plots are presented for a cyclo-olefinic copolymer, a polycarbonate, and a polyvinylchloride. There are three distinct regions on this type of plot. There is a region at low RED including those challenge liquids which dissolve the polymer or are very aggressive, and ESC is not found as such. There is a region at high RED where the absorption is not great enough to matter, or else the absorption rate is slow enough to allow relaxation of the polymer in preference to ESC. ESC can occur in an intermediate region where there is some absorption of challenge liquid. The ESC region on these plots increases in size with increased Stress and/or increased critical strain. The molecular shape of the challenge molecules is clearly important in addition to V . ESC may occur for a challenge chemical with a linear molecular structure, but not for one with the same RED and V , but with a cyclic structure. The absorption rate of the cyclic molecule is too slow. All of the test liquids causing ESC failure in an immersed, injection-molded, cyclo-olefinic copolymer (COC) cylinder had measurable surface resistances retarding absorption. Emphasis is therefore placed on surface resistance to absorption, since this may play an important part in the ESC phenomena itself, and can possibly lead to delaying a catastrophic ESC failure beyond normal testing times. This surface resistance is thought to originate from the rate at which adsorbing molecules can locate a hole in the polymer surface large enough to accommodate them. Larger and more sterically complicated molecules have much more difficulty finding such a suitable hole, so the surface transport coefficient is inversely proportional to the molecular cross-section. Once an adsorbed molecule locates in a suitable hole, the rate of motion into the bulk is dependent on the diffusion coefficient. Therefore the surface transport coefficient is directly proportional to the diffusion coefficient.

  • prediction of Environmental Stress Cracking in plastics with hansen solubility parameters
    Industrial & Engineering Chemistry Research, 2001
    Co-Authors: Charles M Hansen, Lisbeth Juhl Just
    Abstract:

    The results reported here confirm that Environmental Stress Cracking phenomena in plastics depend on the size and shape of the test liquid's molecules as well as their Hansen solubility parameters (HSP) relative to those of the polymer. The behavior of other, untested liquids can be estimated from HSP correlations based on a limited number of test liquids. A simple test has been developed for the Cracking tendency of immersed polymer tubes having different levels of externally applied, controlled Stresses. This uses standard tapered NS Teflon (most glass is too rough) stoppers placed on a toploader analytical balance. Polymer tubes are pressed onto the stoppers until the balance shows the given desired force. The tube and stopper are then immersed in a test liquid and observed at regular time intervals for Cracking. It has been assumed that the Teflon stoppers are inert in this application. The experiments described here used a COC (cyclo-olefinic copolymer) type polymer (Topas 6013, Ticona). The samples ...

Alois K. Schlarb - One of the best experts on this subject based on the ideXlab platform.

  • Environmental Stress Cracking esc resistance of polycarbonate sio2 nanocomposites in different media
    Journal of Applied Polymer Science, 2017
    Co-Authors: Jiraporn Nomai, Alois K. Schlarb
    Abstract:

    Polycarbonate (PC) nanocomposites containing different nano-SiO2 contents were prepared using a twin-screw extruder followed by injection molding. The mechanical behavior and Environmental Stress Cracking (ESC) resistance of the nanocomposites were investigated. Compared to neat PC, the incorporation of nanofiller leads to a slight improvement in Young's modulus, tensile strength, and notched impact strength properties. Interestingly, the nanofiller enhanced the Environmental Stress Cracking resistance of PC in different fluids (isopropanol, methanol, aqueous urea solution, and deionized water) vastly. The correlation of the mode I critical Stress intensity factor with the Hansen solubility parameter shows a very good agreement for different fluids and thus allows the prediction of the Stress Cracking behavior as a function of the filler content for different Stress-Cracking agents. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45451.

  • Environmental Stress Cracking (ESC) resistance of polycarbonate/SiO2 nanocomposites in different media
    Journal of Applied Polymer Science, 2017
    Co-Authors: Jiraporn Nomai, Alois K. Schlarb
    Abstract:

    Polycarbonate (PC) nanocomposites containing different nano-SiO2 contents were prepared using a twin-screw extruder followed by injection molding. The mechanical behavior and Environmental Stress Cracking (ESC) resistance of the nanocomposites were investigated. Compared to neat PC, the incorporation of nanofiller leads to a slight improvement in Young's modulus, tensile strength, and notched impact strength properties. Interestingly, the nanofiller enhanced the Environmental Stress Cracking resistance of PC in different fluids (isopropanol, methanol, aqueous urea solution, and deionized water) vastly. The correlation of the mode I critical Stress intensity factor with the Hansen solubility parameter shows a very good agreement for different fluids and thus allows the prediction of the Stress Cracking behavior as a function of the filler content for different Stress-Cracking agents. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45451.

  • A study on Environmental Stress Cracking in nano-SiO_2-filled polycarbonate
    Journal of Materials Science, 2012
    Co-Authors: Alois K. Schlarb
    Abstract:

    In this study, the Environmental Stress Cracking (ESC) resistance of nano-SiO_2 particle-filled polycarbonate (PC) was investigated at room temperature by using a fracture mechanical test method. Two PC-based nanocomposites with nano-SiO_2 content of 1 and 4 vol% were compounded using a twin-screw extruder. The incorporation of nanoparticles into PC leads to an improvement in ESC resistance, which increases with increased filler loading up to 4 vol%. Fractography analyses suggest that the formation of cavities/debonding and localized microdeformation of matrix induced by nanoparticles as a result of energy dissipation are responsible for the improvement of ESC resistance.

  • Determining resistance to Environmental Stress Cracking in luer fittings.
    Medical device technology, 2002
    Co-Authors: Alois K. Schlarb
    Abstract:

    : Environmental Stress Cracking (ESC) is a phenomenon associated with disposable plastic products. This article describes new methods to determine ESC in luer fittings. The findings of two experimental studies are reported.

Mei Liang - One of the best experts on this subject based on the ideXlab platform.

  • investigations of Environmental Stress Cracking resistance of ldpe uhmwpe and ldpe eva blends
    Plastics Rubber and Composites, 2015
    Co-Authors: Zhengguang Heng, Yang Chen, Mei Liang
    Abstract:

    Low density polyethylene (LDPE)/ultrahigh molecular weight polyethylene (UHMWPE) and LDPE/poly(ethylene-co-vinylacetate) (EVA) blends were tested and compared with respect to their Environmental Stress Cracking resistance (ESCR) using the Bell telephone test. The time to failure in the ESCR test improved with increasing UHMWPE and EVA content, and considerable improvements were produced when an UHMWPE weight fraction of 0.4 and EVA weight fraction of 0.03 were used. Thermal and morphological studies were conducted, and a relationship between morphological features and composition was established. Furthermore, the failed specimens were further characterised by scanning electron microscopy and fractographic methodology to investigate the failure mechanism for ESCR samples.

  • Investigations of Environmental Stress Cracking resistance of LDPE/UHMWPE and LDPE/EVA blends
    Plastics Rubber and Composites, 2015
    Co-Authors: Zhengguang Heng, Yang Chen, Mei Liang
    Abstract:

    Low density polyethylene (LDPE)/ultrahigh molecular weight polyethylene (UHMWPE) and LDPE/poly(ethylene-co-vinylacetate) (EVA) blends were tested and compared with respect to their Environmental Stress Cracking resistance (ESCR) using the Bell telephone test. The time to failure in the ESCR test improved with increasing UHMWPE and EVA content, and considerable improvements were produced when an UHMWPE weight fraction of 0.4 and EVA weight fraction of 0.03 were used. Thermal and morphological studies were conducted, and a relationship between morphological features and composition was established. Furthermore, the failed specimens were further characterised by scanning electron microscopy and fractographic methodology to investigate the failure mechanism for ESCR samples.

  • investigations of Environmental Stress Cracking resistance of hdpe uhmwpe and ldpe uhmwpe blends
    Journal of Polymer Research, 2013
    Co-Authors: Yang Chen, Shengtai Zhou, Mei Liang
    Abstract:

    HDPE/UHMWPE and LDPE/UHMWPE blends were prepared and the Environmental Stress Cracking resistance (ESCR) was compared using the Bell-telephone test. The time to failure in the ESCR test improved with increasing UHMWPE content, and considerable improvements were both produced when an UHMWPE weight fraction of 0.4 was used. Whereas LDPE/UHMWPE blend yield a higher improvement in Stress Cracking resistance compared to that of HDPE/UHMWPE blend. Thermal, morphological and mechanical studies were conducted and a relationship between morphological features and composition was established. Furthermore, the failed specimens were further characterized by scanning electron microscopy and fractographic methodology to investigate the failure mechanism for ESCR samples.

  • Investigations of Environmental Stress Cracking resistance of HDPE/UHMWPE and LDPE/UHMWPE blends
    Journal of Polymer Research, 2013
    Co-Authors: Yang Chen, Shengtai Zhou, Mei Liang
    Abstract:

    HDPE/UHMWPE and LDPE/UHMWPE blends were prepared and the Environmental Stress Cracking resistance (ESCR) was compared using the Bell-telephone test. The time to failure in the ESCR test improved with increasing UHMWPE content, and considerable improvements were both produced when an UHMWPE weight fraction of 0.4 was used. Whereas LDPE/UHMWPE blend yield a higher improvement in Stress Cracking resistance compared to that of HDPE/UHMWPE blend. Thermal, morphological and mechanical studies were conducted and a relationship between morphological features and composition was established. Furthermore, the failed specimens were further characterized by scanning electron microscopy and fractographic methodology to investigate the failure mechanism for ESCR samples.

Yang Chen - One of the best experts on this subject based on the ideXlab platform.

  • investigations of Environmental Stress Cracking resistance of ldpe uhmwpe and ldpe eva blends
    Plastics Rubber and Composites, 2015
    Co-Authors: Zhengguang Heng, Yang Chen, Mei Liang
    Abstract:

    Low density polyethylene (LDPE)/ultrahigh molecular weight polyethylene (UHMWPE) and LDPE/poly(ethylene-co-vinylacetate) (EVA) blends were tested and compared with respect to their Environmental Stress Cracking resistance (ESCR) using the Bell telephone test. The time to failure in the ESCR test improved with increasing UHMWPE and EVA content, and considerable improvements were produced when an UHMWPE weight fraction of 0.4 and EVA weight fraction of 0.03 were used. Thermal and morphological studies were conducted, and a relationship between morphological features and composition was established. Furthermore, the failed specimens were further characterised by scanning electron microscopy and fractographic methodology to investigate the failure mechanism for ESCR samples.

  • Investigations of Environmental Stress Cracking resistance of LDPE/UHMWPE and LDPE/EVA blends
    Plastics Rubber and Composites, 2015
    Co-Authors: Zhengguang Heng, Yang Chen, Mei Liang
    Abstract:

    Low density polyethylene (LDPE)/ultrahigh molecular weight polyethylene (UHMWPE) and LDPE/poly(ethylene-co-vinylacetate) (EVA) blends were tested and compared with respect to their Environmental Stress Cracking resistance (ESCR) using the Bell telephone test. The time to failure in the ESCR test improved with increasing UHMWPE and EVA content, and considerable improvements were produced when an UHMWPE weight fraction of 0.4 and EVA weight fraction of 0.03 were used. Thermal and morphological studies were conducted, and a relationship between morphological features and composition was established. Furthermore, the failed specimens were further characterised by scanning electron microscopy and fractographic methodology to investigate the failure mechanism for ESCR samples.

  • investigations of Environmental Stress Cracking resistance of hdpe eva and ldpe eva blends
    Journal of Applied Polymer Science, 2014
    Co-Authors: Yang Chen
    Abstract:

    HDPE/poly(ethylene-co-vinylacetate) (EVA) and low-density polyethylene (LDPE)/EVA blends were tested and compared with respect to their Environmental Stress Cracking resistance (ESCR) using the Bell-telephone test. The time to failure in the ESCR test improves with increasing EVA content, and considerable improvements were produced for LDPE/EVA blends while small improvements were observed for HDPE/EVA blends. Thermal, rheological, mechanical, and morphological studies were conducted which established a quantitative relationship between morphological features and composition. Furthermore, the failed specimens were further characterized by scanning electron microscopy and fractographic methodology to investigate the failure mechanism for ESCR samples. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39880.

  • Investigations of Environmental Stress Cracking resistance of HDPE/EVA and LDPE/EVA blends
    Journal of Applied Polymer Science, 2013
    Co-Authors: Yang Chen
    Abstract:

    HDPE/poly(ethylene-co-vinylacetate) (EVA) and low-density polyethylene (LDPE)/EVA blends were tested and compared with respect to their Environmental Stress Cracking resistance (ESCR) using the Bell-telephone test. The time to failure in the ESCR test improves with increasing EVA content, and considerable improvements were produced for LDPE/EVA blends while small improvements were observed for HDPE/EVA blends. Thermal, rheological, mechanical, and morphological studies were conducted which established a quantitative relationship between morphological features and composition. Furthermore, the failed specimens were further characterized by scanning electron microscopy and fractographic methodology to investigate the failure mechanism for ESCR samples. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39880.

  • investigations of Environmental Stress Cracking resistance of hdpe uhmwpe and ldpe uhmwpe blends
    Journal of Polymer Research, 2013
    Co-Authors: Yang Chen, Shengtai Zhou, Mei Liang
    Abstract:

    HDPE/UHMWPE and LDPE/UHMWPE blends were prepared and the Environmental Stress Cracking resistance (ESCR) was compared using the Bell-telephone test. The time to failure in the ESCR test improved with increasing UHMWPE content, and considerable improvements were both produced when an UHMWPE weight fraction of 0.4 was used. Whereas LDPE/UHMWPE blend yield a higher improvement in Stress Cracking resistance compared to that of HDPE/UHMWPE blend. Thermal, morphological and mechanical studies were conducted and a relationship between morphological features and composition was established. Furthermore, the failed specimens were further characterized by scanning electron microscopy and fractographic methodology to investigate the failure mechanism for ESCR samples.

Alexander Penlidis - One of the best experts on this subject based on the ideXlab platform.

  • rheological indicators for Environmental Stress Cracking resistance of polyethylene
    International Polymer Processing, 2015
    Co-Authors: Pouyan Sardashti, Maria Anna Polak, Costas Tzoganakis, Martin Zatloukal, Alexander Penlidis
    Abstract:

    Abstract Most studies on Environmental Stress Cracking resistance (ESCR) of polymers have focused on performing mechanical tests in the solid state. In this work, investigations in the melt state were carried out, to identify potential melt indicators for a relative measure of ESCR. A normalized characteristic relaxation time (λN), obtained from dynamic shear experiments, was established as a valid measure of ESCR of linear low density polyethylene, where a large content of short chain branches is present. In addition, the melt strain hardening coefficient (MSHC), obtained from extensional rheological methodologies, was found to be another potential and reliable indicator of ESCR. An inverse correlation between MSHC and ESCR was observed, indicating an inverse relationship between ESCR and chain extensibility in the melt. Furthermore, a new factor called “melt hardening stiffness (mHS)” was developed from the slope of a Stress vs. Hencky strain obtained from a Sentmanat extensional rheometer. mHS was foun...

  • effect of temperature on Environmental Stress Cracking resistance and crystal structure of polyethylene
    Journal of Macromolecular Science Part A, 2014
    Co-Authors: Pouyan Sardashti, Maria Anna Polak, Costas Tzoganakis, Alison J Scott, Alexander Penlidis
    Abstract:

    Studies were conducted on the crystalline properties of different polyethylene resins to identify their influence on phase interconnectivity between amorphous and crystalline regions. This work offers a thorough investigation on the potential correlation between Environmental Stress Cracking resistance (ESCR) and crystalline structure characteristics, namely, crystallinity, mean lamella thickness and its distribution, and lamella surface area (LSA). The initial objective of this work was to investigate an existing ambiguity in the literature with respect to the effect of the crystalline phase on ESCR. In addition, research was conducted to evaluate the degree of variability in the lamella surface area, as a measure of phase interconnectivity and ESCR, with processing temperature and post-process annealing. Annealing at various conditions, along with cooling at different rates, were employed to investigate the effect of temperature on LSA. It was observed that a clear correlation exists between crystalline...

  • improvement of hardening stiffness test as an indicator of Environmental Stress Cracking resistance of polyethylene
    Journal of Macromolecular Science Part A, 2012
    Co-Authors: Pouyan Sardashti, Maria Anna Polak, Costas Tzoganakis, Alexander Penlidis
    Abstract:

    Long term mechanical behavior of polyethylene (PE) is of great importance especially in cases where structural integrity is required. In order to predict characteristics of the mechanical behavior of PE, it is necessary to fully understand the molecular structure of the employed resins. In this study, evaluation of several micromolecular properties of PE is conducted. These properties influence an important performance indicator of PE for structural applications, namely, the Environmental Stress Cracking resistance (ESCR). ESCR in PE resins occurs through a slow crack growth mechanism under low applied Stresses and long periods of time. This property is usually assessed by unreliable and time consuming testing methods such as the notch constant load test (NCLT) on notched PE specimens in the presence of an aggressive fluid at elevated temperatures. In the work presented herein, relationships between molecular structure and material response characteristics, mainly between molecular weight properties and s...

  • influence of micromolecular structure on Environmental Stress Cracking resistance of high density polyethylene
    Tunnelling and Underground Space Technology, 2011
    Co-Authors: Joy J Cheng, Maria Anna Polak, Alexander Penlidis
    Abstract:

    Environmental Stress Cracking (ESC) is a serious problem for polyethylene (PE) in structural applications and can result in catastrophic failure without any visible warning. Due to the nature of polymeric materials, polyethylene with excellent short-term mechanical strength can have poor long-term performance due to Environmental Stress Cracking. In this work, we present our recent research findings on Environmental Stress Cracking resistance (ESCR) of polyethylene. In this comprehensive overview we discuss (1) molecular structure influences on ESCR, (2) a new method for evaluating ESCR of PE, and (3) ESC modeling work, practical tips and prescriptions for producing and choosing better (higher) ESCR pipe material.

  • polymer network mobility and Environmental Stress Cracking resistance of high density polyethylene
    Polymer-plastics Technology and Engineering, 2009
    Co-Authors: Joy J Cheng, Maria Anna Polak, Alexander Penlidis
    Abstract:

    Zero shear viscosity and molecular weight between entanglements (M e ) are determined from dynamic oscillatory shear experiments. Lower M e value means higher number of entanglements in the system and is associated with increasing strain hardening stiffness. With the understanding that strain hardening is related to Environmental Stress Cracking resistance (ESCR) of high density polyethylene (HDPE), M e is then related to the ESCR of several resins in this study. The inversely proportional relationship between M e and ESCR indicates that low network mobility due to an increasing number of chain entanglements increases the ESCR of HDPE.