High-density Polyethylene Plates Research Articles

Thermal modeling of friction stir welding of thick high-density polyethylene plates

The process temperatures in the friction stir welding of thick polymer plates play a significant role in the joint's quality since the process is characterized by mixed solid and viscous flow states. The heat generation mechanism in each state is fundamentally different, with heat being generated by friction in the solid-state and by viscous shear flow in the viscous state. In this study, the heat generation and dissipation in the friction stir welding of 14 mm thick high-density polyethylene plates were studied numerically through solving the direct heat conduction problem. Two models of heat generation were used in the numerical solution and the effect of the pin rotational speed on the process temperatures was investigated. It was shown that the utilization of a mixed heat generation model consisting of both the solid state and the viscous shear flow considerably improves the numerical model predictions. The temperature predictions were validated through welding experiments and showed a temperature difference of 3 %. Furthermore, it was found that the welding process stabilizes at rotational speeds higher than 800 rpm, where no considerable change occurs in the volume of the viscous flow region and the welding power requirement. The numerical results based on the combined solid-viscous heat model were in good agreement with the experimental thermal histories.

Boron Nitride Filled Thermoplastics for Passive Shielding of Space Electronics

Space environment is rich of high energy particles that form the radiation field. Human beings as well as electronic devices are susceptible to their action, even if the exposure time is limited. For this reason, radiation shields are needed to carry out safe space missions. Traditionally, in-space shielding frames are made up of aluminum, but more recent studies have shown that a good shielding efficiency can be achieved by hydrogen (H)-rich materials, as polyethylene (PE). Moreover, it was noticed that small mass atoms as H, boron (B) and nitrogen (N) can reduce secondary emissions. In this work, radiation shields of high-density PE (HDPE) filled with boron nitride (BN) have been manufactured. Since BN particles dispersion into the polymeric matrix strongly affects the composite shielding ability, 2 filling routes have been investigated. The first manufacturing strategy is about melt-mixing: HDPE is melted at 200 °C into a batch-mixer, then BN powder is inserted, and mixing is carried out until the torque exerted by the rollers reaches a plateau. Subsequently, the shield is obtained by molding and machining. The second strategy is about the filler spray deposition; BN is spayed on HDPE plates surface after which stacking occurred and consolidation is carried out at 130 °C for 24 h. At the end, machining is performed. The shields dimensions are 25x25x10 mm3 and 50x46x35 mm3, respectively. Both of them show a good level of agglomeration and a good fillers dispersion, with a final density close to the HDPE nominal value.

Thermal Effect of Bobbin Tool Friction Stir Welding on the Mechanical Behavior of High Density Polyethylene Sheets: Experimental Study

Bobbin friction stir welding (BT-FSW) is a variant of the conventional friction stir welding (C-FSW). This method has been applied of welding high density polyethylene (HDPE) plates; where a rotating symmetrical tool causes a fully penetrated bond, it can weld the upper and lower surface of the work-piece in the same pass. BT-FSW process involves complex heat generation and HDPE flow, which directly affects on the weld area and on mechanical properties of welded joint. Heat generation and material flow during BT-FSW are significantly affected by the tool design features, process parameters and mechanical behavior of work piece materials. Studying the temperature of polyethylene sheets welded by BT-FSW can help in analyzing the mechanism of weld formation and also can provide theoretical guidance for the tool design, process parameter selection and even new process development. In the unique work described in this paper, the 11.4 mm-thick HDPE plates were welded successfully by bobbin-tool friction stir welding. Measurements of the material temperatures were performed by thermocouples which are placed near and at the weld seam. The weld quality was determined in terms of no defects in the stir zone and the tensile strength of the joint. It was found that considerable melting occurred between the rotating shoulders and on the trailing side of the rotating pin. Movement of the molten material by the rotating tool created a very black band in the stir zone. Thermocouples measurements indicated that the temperatures were higher on the advancing side (AS) compared to those on the retreating side (RS). Tensile tests and hardness measurements were performed on welded and seamless sheet samples. The results were analyzed to compare the mechanical properties. To demonstrate the variation in micromechanical properties between welded and seamless sheet samples, micro hardness (HV) testing was used to explain the difference. The HV of the HDPE plates weld by BT-FSW, were relatively symmetrical with respect to the parting line. The maximum hardness levels were reached in the weld bead at around 66 HV in the welded nugget; there was a rise in the level of hardness, in particular at retreating side (RS) and at advancing side (AS) where the value reached 68.60 HV.

Effect of Tool Design on the Mechanical Properties of Bobbin Friction Stir Welded High-Density Polyethylene Sheets: Experimental Study

Welding polymers by the friction stir welding (FSW) technique is one assembly process among several known assembly techniques which consists in welding two materials without filler material. The FSW process is based on the generation of heat due to friction and material deformation under an axial force. Among the main aspects affecting material flow, the choice of welding tool geometry has become of great interest to improve the welds quality. The main objective of this work is the welding of polymers using the FSW technique. A new method of welding HDPE (high density polyethylene) plates, called BT-FSW (bobbin tool friction stir welding) was developed. Standard rectangular shape intended for the distribution of natural gas has been successfully welded by BT-FSW. Tensile tests and hardness measurements were carried out on samples cut from the welded sheets and the results were analyzed to compare the mechanical characteristics of the plates welded by the BT-FSW and conventional FSW (C-FSW) processes. The results of the comparative studies on the micro-hardness characteristics and mechanical properties of the two welding processes indicate that welding using the bobbin tool can significantly reduce hardness and improve both weld formation and mechanical properties of joints. This study showed that the design of the welding tool has a big impact on the weld strength. An improvement in the mechanical properties of the specimens welded by BT-FSW was observed to give a better welding quality for the polymers studied.

The Effects of Stress Triaxiality on the Neck Initiation and Fracture of High-density Polyethylene (HDPE)

This study analyses the tensile mechanical behaviour and deformation of neck i.e localization initiation, propagation and fracture of injection-moulded polymer composed of high-density polyethylene (HDPE) as a function of initial stress triaxiality. Three different specimen geometries namely i) Simple tension, ii) Plane strain and iii) Shear specimens were punched from injection-moulded HDPE plates and tested experimentally in uniaxial tension to introduce different stress triaxialities. These specimen geometries used are standard for the material characterization of sheet metals. However, for plate polymer materials such specimen geometries have not comprehensively been studied earlier. Standard shear specimen geometry has been further optimized in this work using finite element models to restrict unwanted out-of-plane deformations arising at large deformation. The digital image correlation (DIC) technique is used to acquire the full field deformation and in particular the localized strains in the neck region of the specimens. Based on the major-minor strain paths from DIC-measurements stress triaxiality has been calculated. It is challenging to follow the stochastic pattern at larger local strain in DIC and hence the strain at failure has been measured using orthogonal grid lines on the specimen surface. Finally, strains at neck-initiation and failure at three different stress triaxialities are reported for injection-moulded HDPE in two material orientations. It is observed that within the elastic limit the stress triaxialities obtained from the experimental tests were close to the ideal values found in the literature and neck-initiation strain is strongly dependent on the stress triaxiality. However, as neck initiates and propagates, the triaxialities for all geometries shift closer to the measured value in a simple tension specimen i.e. 0.33 limiting the effect of the initial triaxiality on failure strain.

Hypervelocity impact response of monolithic UHMWPE and HDPE plates

When developing layered or architected protective structures to mitigate hypervelocity impacts (HVIs), understanding and characterizing the ultra-high rate response and energy dissipation of each constituent is critical. Incorporation of lightweight polymeric materials as intermediate or inner-most structural layers could optimize HVI damage resistance and tolerance without compromising cost or weight. One key challenge is developing a fundamental understanding of the effects of molecular architecture on the macroscopic dynamic material response and damage formation. In this work, two common and affordable thermoplastics, namely ultra-high molecular weight polyethylene (UHMWPE) and high density polyethylene (HDPE), were assessed. Flat square targets of two distinct sizes were subjected to a series of normal HVIs with 10 mm diameter 1050 aluminum spheres at velocities in the range 2–6.5 km/s. The debris cloud velocity, mass loss, and perforation radius were found to be functions of impact velocity for both materials. High-speed images show HVIs to UHMWPE resulted in quasi-brittle responses while HVIs to HDPE resulted in apparent bulk-melting of the material and large-scale plastic deformation. When subjected to HVIs in the tested range, UHMWPE plates exhibited greater mass loss than similar HDPE plates despite the perforation radii being larger in HDPE. This suggests that the momentum and kinetic energy of the debris clouds for UHMWPE targets were greater than that for HDPE targets subjected to identical impacts. These HVI experimental results combined with polymer material characterization data indicate that differences in the polymeric molecular structure and chemistry of the polyethylenes affect their macroscopic HVI performance.

Design and analysis of plate angles of the four-vertex origami pattern and its impacts on movement of rotational joints

We present a pneumatic origami joint, which consists of 89 degrees plate angles of Four-vertex origami mechanism activated by pouch motors. The proposed prototype consists of four high-density polyethylene plates connected by flexible adhesive polyethylene tapes. A cutting-binding technique was used for the fabrication of the origami. This technique is inexpensive and easy to replicate. We modeled the kinematics of the origami as a spherical mechanism, and compared with experimental result, against several origami mechanisms with different angles of origami’s plates. We found that an origami mechanism with a plate angle of 89∘ shows around 8.4 times higher rotational movement for a given angular displacement of the input link compared to a mechanism with a plate angle close to 0∘ or a simple fold which is equivalent to a revolute joint. The proposed design is flat-foldable (the sum of odd or even angles around the central vertex equals to 180∘). The pneumatic origami joint can fold and adapt its shape to the environment.

Parametric Study Of Friction Stir Spot Welding (FSSW) For Polymer Materials Case Of High Density Polyethylene Sheets: Experimental And Numerical Study

Friction stir spot welding (FSSW) is a very important part of conventional friction stir welding (FSW) which can be a replacement for riveted assemblies and resistance spot welding. This technique provides high quality joints compared to conventional welding processes. Friction stir spot welding (FSSW) is a new technology adopted to join various types of metals such as titanium, aluminum, magnesium. It is also used for welding polymer materials which are difficult to weld by the conventional welding process. In various industrial applications, high density polyethylene (HDPE) becomes the most used material. The parameters and mechanical properties of the welds are the major problems in the welding processes. In this paper, we have presented a contribution in finite element modeling of the friction stir spot welding process (FSSW) using Abaqus as a finite element solver. The objective of this paper is to study the HDPE plates resistance of stir spot welding joints (FSSW). First, we show the experimental tests results of high-density polyethylene (HDPE) plates assembled by friction stir spot welding (FSSW). Three-dimensional numerical modeling by the finite element method makes it possible to determine the best representation of the weld joint for a good prediction of its behavior. Comparison of the results shows that there is a good agreement between the numerical modeling predictions and the experimental results.

Visualization of hidden damage from scattered wavefield reconstructed using an integrated high-speed camera system

In this article, a feasibility study for the visualization of hidden damage using an integrated high-speed camera system was carried out. A thin, planar, and low-modulus high-density polyethylene plate with surrogate damage was chosen to represent a damaged structure for the proof of concept, and two different damage scenarios (mimicked by attaching lightweight rectangular/circular masses to the back of the plate) were investigated. The acoustic/ultrasonic guided waves were generated in the plate by a surface-mounted piezoelectric actuator under continuous sinusoidal excitation, and in-plane wavefield displacements on the surface of the plate were captured using a high-speed camera. In order to reconstruct the scattered wavefield, these in-plane wavefields which primarily include the fundamental symmetric wave mode S0 and fundamental shear horizontal wave mode SH0 (induced due to reflection/scattering of the incident S0 wave mode from the damage and plate boundaries) were then extracted using digital image correlation image analysis software. All the experimental parameters (e.g. material properties of the plate, excitation frequency, selection of lens, field-of-view, speckle size) were carefully designed, integrated, and optimized. In order to overcome the current hardware limitations (insufficient spatial/temporal resolution), sample interleaving was implemented to artificially enhance the frame rate and image stitching techniques were used to increase the total effective camera resolution. Together, these techniques provided a nearly 250-fold enhancement in the data acquisition capability of the high-speed camera. In order to fully demonstrate the efficacy of the sample interleaving technique, two frequencies were excited: 14 and 28 kHz, below and above the original Nyquist frequency, respectively. The first fundamental SH0 and S0 wave modes for both frequencies were successfully detected and identified, and the disturbances at the damage region were clearly observed in the scattered wavefield reconstructed with the SH0 mode in particular, as the SH0 mode has a shorter wavelength making it better suited for detecting smaller damage. The hidden damage was then visualized by employing a modified version of the phase-based damage imaging condition, wavenumber index, that was previously developed for visualizing hidden delamination damage in composites with a laser Doppler vibrometer scanning system.

Discontinuous slow crack growth modeling of semi-elliptical surface crack in high density polyethylene using crack layer theory

Surface flaws in structural materials are most likely to be generated during service time. One of the most general shapes of surface flaws is the semi-elliptical surface crack. Frequently, the slow crack growth (SCG) of a crack has been fitted based on the conventional Paris–Erdogan relationship. However, in the case of engineering plastics, which generally reveal a severe unrecoverable damage zone at the crack tip, the conventional Paris–Erdogan relationship is not appropriate to describe the SCG of a crack. Especially, SCG kinetics of some engineering polymers such as high-density polyethylene (HDPE) affect the SCG characteristics, i.e. non-conventional discontinuous SCG behavior, which cannot be simulated by conventional Paris–Erdogan relationship. It is known that the crack layer (CL) theory, which deals with driving forces of crack and process zone (PZ) together, can be a good mathematical model to simulate such SCG behavior. In this study, the discontinuous SCG of a semi-elliptical surface flaw in HDPE plate under cyclic tensile stress was simulated using the CL theory. Although the CL theory has the advantage of simulating the discontinuous SCG of HDPE accurately, until now the applications have been concentrated on one-dimensional slow crack growth. In this paper, the CL model for two-dimensional surface crack growth for axial and bending loading conditions was developed for the first time. The proposed model is validated with actual test results, and the role of some key CL parameters on discontinuous SCG behavior of a semi-elliptical surface flaw is investigated by intensive parametric studies.

Thermal and fast neutron detection through high-purity single-crystal CVD diamonds

We developed neutron detectors for detecting thermal and fast neutrons. The sensing element of the neutron detector uses a high-purity chemical-vapor-deposited (CVD) diamond plate, with a size of 3 mm × 3 mm × 0.5 mm, and the ø5 mm detector is sealed for use in the reactor as a small tube by using laser micro welding. The electrodes of the fast and thermal neutron detectors are made up of Ag and Gd with approximately 100-nm and 5 μm thicknesses, respectively. The deposition method of the electrode uses the RF plasma sputtering system. The developed neutron detectors were tested on a 30-MeV cyclotron, which generates fast neutrons and gamma rays. High-density polyethylene plates, Cd plates, and Pb bricks were used for the moderator and shielding. The Ag electrode detector measured the current generated by fast neutrons and gamma rays. Although the sensitivity of the Gd electrode detector is smaller than that of the Ag electrode detector, it measured the current generated by thermal neutrons as well as fast neutrons and gamma rays.

Fabrication of high density polyethylene composites reinforced with pine cone powder: mechanical and low velocity impact performances

The pine cone plant is a cellulosic material that is inexpensive and abundant in nature. It can be used as a reinforcing material in thermoplastic based composites. Pine cone plant has good mechanical properties and therefore allows it to be used as a filler material in composites. Alternative utilization from such agricultural pine cone powder in high density polyethylene (HDPE) composites can supply economic and environmental advantages. In this study, pine cone reinforced high density polyethylene (HDPE) composites were fabricated and their mechanical (i.e., tensile, compression and flexural properties) and low velocity impact behaviors were determined experimentally. To this end, collected pine cones were firstly cut into 1 cm pieces by using a knife and were pulverized by grinding in a ring mill. After that, two HDPE plates with dimensions of 350 × 350 × 1 mm were manufactured in the hot press. Then, various percentage amounts of powdered pine cones (5, 10, 15 and 20% wt) were added between these plates. Thereafter, pine cone reinforced HDPE composites were obtained under the same conditions. Mechanical properties and low velocity impact behaviors of the pine cone reinforced HDPE composites were determined at room temperature and findings were compared with each other. The parameters such as tensile and flexural strengths, compressive strength, elasticity and flexural modulus and energy absorption capacities of the composites were evaluated through various curves. According to obtained results, HDPE containing 10% pine cone powder showed the highest tensile strength, elasticity modulus and flexural strength. Low velocity impact test results exhibited that maximum contact force values of the reinforced HDPE with 5, 10 and 15% wt pine cone powder are higher than the neat HDPE at the impact energy levels ranging from 5 J to 25 J.

Horizontally rotating disc recirculated photoreactor with TiO2-P25 nanoparticles immobilized onto a HDPE plate for photocatalytic removal of p-nitrophenol

ABSTRACTIn this study, a horizontally rotating disc recirculated (HRDR) photoreactor equipped with two UV lamps (6 W) was designed and fabricated for photocatalytic removal of p-nitrophenol (PNP). Photocatalyst (TiO2) nanoparticles were immobilized onto a high-density polyethylene (HDPE) disc, and PNP containing solution was allowed to flow (flow rate of 310 mL min–1) in radial direction along the surface of the rotating disc illuminated with UV light. The efficiency of direct photolysis and photocatalysis and the effect of rotating speed on the removal of PNP were studied in the HRDR photoreactor. It was found that TiO2-P25 nanoparticles are needed for the effective removal of PNP and there was an optimum rotating speed (450 rpm) for the efficient performance of the HRDR photoreactor. Then effects of operational variables on the removal efficiency were optimized using response surface methodology. The results showed that the predicted values of removal efficiency are consistent with experimental results with an R2 of 0.9656. Optimization results showed that maximum removal percent (82.6%) was achieved in the HRDR photoreactor at the optimum operational conditions. Finally, the reusability of the HRDR photoreactor was evaluated and the results showed high reusability and stability without any significant decrease in the photocatalytic removal efficiency.

Characterization of laser beam transmission through a High Density Polyethylene (HDPE) plate

Infrared (IR) light propagation in semicrystalline polymers involves mechanisms such as reflection, transmission, absorption and internal scattering. These different rates determine either the interaction mechanism, either the temperatures reached in the IR heating processes. Consequently, the knowledge of these rates is fundamental in the development of IR heating processes in order to avoid the polymer's damage and to increase the process energy efficiency. Aim of this work is to assess a simple procedure to determine the rates of absorbed, reflected, transmitted and scattered energy in the case of an unfilled High Density Polyethylene (HDPE) plate. Experimental tests were performed by exposing a HDPE plate, 3mm in thickness, to a diode laser source, working at the fundamental wavelength of 975nm. The transmitted power was measured by power meter, the reflected one by applying the Beer–Lambert law to sample of different thickness. IR thermal images were adopted to measure the absorbed ratio. The scattered ratio was measured by energetic balance, as difference between the incoming power and the other ratios. Finally, IR thermal images were adopted to measure the scattered ratio and to validate the procedure.

Induction heated tool assisted friction-stir welding (i-FSW): A novel hybrid process for joining of thermoplastics

This paper presents a hybrid friction-stir welding process, i-FSW, for the joining of thermoplastics. In this process, the friction-stir tool during welding is heated by induction and the temperature is precisely maintained though feedback control. The paper conveys new observations on friction-stir welding of thermoplastics through a case study on the welding of high-density polyethylene plates. The mechanical behavior and weld microstructure were studied over a wide range of tool rotational speeds and tool-pin temperatures. A narrow transition zone between the weld and base materials without any defect ensures joints with a similar strength to the base material, vis-a-vis better than previously reported results with the same material. A drop in hardness at the weld zone, for all the parameters, and a transition from brittle to ductile nature of the joints at higher tool-pin temperatures were observed. The material flow and weld formation mechanism in i-FSW is discussed.

Properties and printability of compression moulded recycled polyethylene

The goal of the research was the determination of the properties and printability of polymeric materials made from the recycled polymers, low-density polyethylene (LDPE) and high-density polyethylene (HDPE). From the primary (virgin) polymers and secondary (recycled) polymers that were obtained from the separately collected fractions of waste packaging, compression moulded plates were produced. The tensile properties of 1mm and 2mm thin plates were correlated with some structural characteristics: melting point, melting enthalpy and crystallinity degree. It was determined that the recycling process changes the melting behaviour, lowers the crystallinity and to some extent influences the tensile properties of plates. LDPE and HDPE compression moulded plates were printed with the UV inks on the large format digital UV inkjet printer Océ Arizona. To investigate the printability of plates made from the recycled materials some of their surface properties were determined. Higher optical density, area of ink coverage and dot gain of the printed HDPE plates compared to the LDPE plates are the consequence of higher roughness, higher surface energy with prevailing part of the polar component. By adding 4% of coloured master batch to the recycled polymer at moulding, the uniformity of colour is improved leading to the higher print quality. The results have shown that the digital UV inkjet printing technique could be applied for printing recycled polyethylene plastic materials, used for disposable low cost packaging products.

Cold spray metal embedment: an innovative antifouling technology

The study demonstrates that embedment of copper particles into thermoplastic polymers (polymers) using cold spray technology is an effective deterrent against fouling organisms. Two polymers, high-density polyethylene (HDPE) and nylon were metallised with copper powder using cold spray technology. After 250 days in the field, Cu-embedded HDPE and copper plate controls were completely free of hard foulers compared to Cu-embedded nylon and polymer controls which were heavily fouled with both soft and hard fouling. Antifouling (AF) success is related to the interaction between the properties of the polymers (elastic modulus and hardness) and the cold spray process which affect particle embedment depth, and subsequently, the release of copper ions as determined by analytical techniques. Embedding metal using cold spray equipment is shown to be an effective AF technology for polymers, in particular those that are difficult to treat with standard AF coatings, with efficacy being a function of the interaction between the cold spray metal and the polymer recipient.

Effect of pulse repetition rate and number of pulses in the analysis of polypropylene and high density polyethylene by nanosecond infrared laser induced breakdown spectroscopy

Pulse repetition rates and the number of laser pulses are among the most important parameters that do affect the analysis of solid materials by laser induced breakdown spectroscopy, and the knowledge of their effects is of fundamental importance for suggesting analytical strategies when dealing with laser ablation processes of polymers. In this contribution, the influence of these parameters in the ablated mass and in the features of craters was evaluated in polypropylene and high density polyethylene plates containing pigment-based PbCrO4. Surface characterization and craters profile were carried out by perfilometry and scanning electron microscopy. Area, volume and profile of craters were obtained using Taylor Map software. A laser induced breakdown spectroscopy system consisted of a Q-Switched Nd:YAG laser (1064nm, 5ns) and an Echelle spectrometer equipped with ICCD detector were used. The evaluated operating conditions consisted of 10, 25 and 50 laser pulses at 1, 5 and 10Hz, 250mJ/pulse (85Jcm−2), 2μs delay time and 6μs integration time gate. Differences in the topographical features among craters of both polymers were observed. The decrease in the repetition rate resulted in irregular craters and formation of edges, especially in polypropylene sample. The differences in the topographical features and ablated masses were attributed to the influence of the degree of crystallinity, crystalline melting temperature and glass transition temperature in the ablation process of the high density polyethylene and polypropylene. It was also observed that the intensities of chromium and lead emission signals obtained at 10Hz were two times higher than at 5Hz by keeping the number of laser pulses constant.

Adhesion of polyethylene plates photografted with methacrylic acid and acrylic acid with enzymatically modified chitosan solutions and X‐ray photoelectron spectroscopy analysis of failed surfaces

AbstractAn investigation was carried out on the application of dilute chitosan solutions modified by a tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenetylamine (dopamine) to the adhesion of low‐density polyethylene (LDPE) and high‐density polyethylene (HDPE) plates photografted with carboxyl‐group‐containing hydrophilic monomers, such as methacrylic acid (MAA) and acrylic acid (AA). In the case where photografting was carried out at lower monomer concentrations or at lower temperatures, the adhesive strength sharply increased with lower grafted amounts. A sharp increase in the adhesive strength was found to be due to the formation of shorter grafted polymer chains at lower monomer concentrations and/or the restriction of the location of grafting to the outer surface region at lower temperatures. In addition, the adhesive strength also sharply increased at even lower grafted amounts for photografting onto the HDPE plates and/or that of AA because the location of grafting was restricted to the outer surface region. For the AA‐grafted LDPE and HDPE plates, substrate breaking was observed. This was attributed to the coverage of the substrate surfaces with grafted poly(acrylic acid) chains at lower grafted amounts and a high water absorptivity of the grafted layer. X‐ray photoelectron spectroscopy (XPS) analysis of the grafted LDPE plates incubated in a dopamine solution containing tyrosinase suggested that the increase in the adhesive strength was caused by the penetration of enzymatically modified chitosan solutions in the grafted layers and the subsequent reaction of quinone derivatives enzymatically generated with grafted polymer chains. In addition, the surface analysis of the failed surfaces by XPS showed that as the adhesive strength increased, the location of failure was shifted from the interface between the layers mixed with enzymatically modified chitosan materials and grafted polymer chains to the inside the grafted layer containing enzymatically modified chitosan materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Spiral Countercurrent Chromatography Studies Using the Spiral Disk Assembly

The first rotor proposed for high speed countercurrent chromatography (HSCCC), the spiral disk assembly, consisting of a stack of 8 high density polyethylene plates with spiral flow channels, has been studied with various solvents and peptide separations to understand its application to polar compounds and solvent systems. Mostly polar solvent systems comprised of the heavy alcohols, were studied because of their suitability for peptide and larger molecule separation. Peptide mixtures were separated to correlate partition coefficients ranging from 0.3 to 2.8 with elution in spiral CCC. With some peptides, scale-up purification experiments were performed with sample loadings up to 85 mg in the 153 mL volume rotor. These studies characterized polar solvent systems with high stationary phase retentions that can be used for separation and purification of compounds with suitable partition coefficients. The solvent system, sec-butanol-1% aq.trifluoroacetic acid with a 73.3% stationary phase retention proved to be useful for most separations. This is a very useful method to substitute for the use of acetonitrile in preparative chromatography.