The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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Thermogravimetric Analysis of Water Associated with Cellulose Fibers
A new classification of water in a fiber-water system, termed “hard-to-remove (HR) water”, was defined from an isothermal TGA experiment. This HR water was found to include some free water (trapped water) as well as bound water (freezing and non-freezing water). Specific experimental conditions have been defined for an appropriate measurement of the HR water content. The HR water content was correlated with important characteristics of cellulose-based fibers including water retention value and freeness. This test can be performed on extremely small samples as a convenient, insightful characterization technique for cellulose-based fibers.
Experiments in Impulse Welding a Thin Film Lid for Sealing Micro-Channels in Microfluidic Applications
The rapid increase in demand for polymer based MEMS has led to the development of various techniques for joining micro-devices. This paper describes experiments in impulse welding of thin polycarbonate films on a carbon filled polycarbonate substrate similar to the sealing of micro-channels on a microfluidic device. Pressure burst testing was carried out in order to measure the weld strength. The effects of power and heating time on weld width and weld strength were studied. The weld width was found to increase with power and welding time. Weld strength was found to increase with power and time until a point beyond which the strength dropped due to possible degradation. The temperature history on the film and the substrate surfaces was measured using thermocouples. The heating during impulse sealing was then modeled using a two dimensional transient finite element model. Fracture surface analysis revealed that weaker welds had a visually similar fractography irrespective of the welding conditions or thickness of nichrome wire used. Similar observations were made for the strong welds. To evaluate the effects of stress concentrations within the weld during the burst test, experimental and mathematical analysis were conducted. A closed form solution was used to calculate the stress based on the displacement values for the film that were obtained from experimental measurement.
Manipulation of Fiber Orientation by Shear Rotation in Injection Molding
The development of fiber orientation in injection molding was manipulated by a special molding tool, the RCEM mould, which imposes a rotation action of one of the cavities wall during mould filling. Central gated disc moldings were produced in a glass fiber reinforced polypropylene, GFRP, with different cavity rotation velocities, inducing distinct distributions and levels of fiber orientation. The microstructures of the moldings were characterized by optical and electronic microscopy. The through-the-thickness profiles of fiber orientation (orientation tensor) were measured. The relationship between the processing thermomechanical environment and the fiber orientation are established.
Study of the Loading Capacity of Biodegradable Core-Shell Nanospheres
Core-shell nanospheres have recently emerged as novel drug delivery systems. The performance of the particles depends upon several characteristics including loading capacity, size, composition, etc. The amount of drug that can be loaded into the core is a function of several factors, such as the size and hydrophobicity of the core, the hydrophobicity of the encapsulant, and specific interactions. These parameters are used to optimize the performance of the formulations. In this work, we studied the loading capacity of biodegradable nanospheres as a function of the size of the nanospheres and hydrophobicity of the encapsulant using encapsulants of varying hydrophobicity and different molecular weight linear amphiphilic block copolymers of pullulan and polycaprolactone (PCL). The established relationship is a useful tool in predicting the loading capacity for other substances based on their hydrophobic character and hence in designing an optimum drug delivery system.
Measurement of Surface Polarity of Organically Treated Nanoclay Using Contact Angle Method
In this paper, we measured surface free energy and surface polarity of organically modified montmorillonite clay (OMMT) using contact angle and Wu’s harmonic-mean equation. The effect of heat treatment, as in polymer processing operations, on polarity was studied. It was observed that the surface polarity reduced significantly with heat treatment owing to degradation of the organic modifier of clay. It was observed that a nonpolar polymer, polypropylene (PP), spread more on heat treated surface than a polar polymer polyamide 6 (PA6). This has significant consequences on morphology development in the blending of PP and PA6.
Vibration Welding Short- and Long-Glass-Fiber-Reinforced Polyppropylene Compounds
Two short-glass-fiber-reinforced polypropylene and two long-glass-fiber-reinforced polypropylenes were vibration welded using a laboratory scale welder. The tensile properties of butt-welded plates were measured as a function of vibration welding pressure and meltdown. The weld strength was observed to decrease with increasing fiber content and length. Increases in weld pressure caused small decreases in weld strength for short-glass-fiber-reinforced polypropylene and a small increase in weld strength for long-reinforced-reinforced polypropylene. The initial fiber orientation in the welded plate and meltdown also had small effects on weld strength.
Comparative Studies between Charpy Impact Test and Dynatup Impact Test
Fracture dynamics of various bimodal HDPEs were investigated based on the loadtime history and impact energy recorded in a Dynatup impact tester. The crack propagation energy (A2) obtained from the Dynatup impact test showed a good correlation to the impact energy from the Charpy test. It is believed that A2, revealing the resistance to crack propagation after the crack has been initiated, reflects a closer relation to the genuine crack energy. Whether or not A2 is a better parameter than ‘Charpy energy’ for predicting rapid crack propagation (RCP) performance requires data support from S4 or full-scale test. Also, a crossover temperature (Tx), which is defined as the temperature where the crack initiation energy (A1) and the propagation energy (A2) intersects in a plot against temperature, is found to exhibit a good correlation with A2.
Development of Flaw Criteria for Short-Term Performance of Electro-Fusion Pipe Welds
The effects of lack of fusion defects on short term performance of electro-fusion polyethylene gas pipe welds were evaluated when it is subjected to loadings that are experienced by the joint in service. Recently improved ultrasonic non-destructive evaluation techniques were developed for detecting some of these defects. However, it was necessary to develop criteria for determining the size and location of defects that would result in unacceptable short term performance of the weld. We performed a variety of short term tests on joints with pre-designed defects including tensile, crush, and pressure leak tests. In addition, finite element modeling was used to find the stress distribution for joints with and without defects. The experimental results were then used together with modeling work to propose criteria for the size and location of the defects. It was found that for short term performance, defects that are near the outside edge of the socket were most critical.
The Control of Creep Memory in Extruded Polypropelene Tubes
The bend memory of extruded polymer tubes creates major problems during the high-speed automatic assembly of extruded and injection moulded components. This work investigates the effect of water bath quenching conditions, during tube extrusion processing, on the crystalline development, mechanical and creep performance, bend memory and recovery of small bore tubes manufactured from polypropylene (PP). Characterisation of the various tube samples was performed using mechanical (tensile, flexural) and thermal (DSC) analysis techniques. The results indicate that the water bath temperature was a critical processing parameter affecting the bend memory characteristics of these tubing products.
Deformation of PET Nanocomposites
The toughening mechanism in polyethylene terephthalate (PET) nanocomposites is investigated as a function of MLS concentration of 1 and 3% using effective area under the stress-strain curve coupled with infra red (IR) thermal wave imaging techniques. 1% MLS concentration, which had an exfoliated structure exhibited slight enhancement in toughness as compared to neat PET whereas 3% MLS composition showed drop in toughness by 87%. From IR thermography, it was concluded that the toughening mechanism in neat PET is due to the chain mobility induced by thermal heating. On the other hand in 1% MLS concentration, the increase in temperature (plastic deformation) is negligible. Differential scanning calorimetry results indicate the absence of cold crystallization peak. This implies that that the interlamellar disorder is completely removed. In the case of 3% MLS nanocomposite, strain embrittlement is seen. This effect of embrittlement is pronounced at higher rate of testing where ductile-brittle transition is evident in 3% nanocomposite.
Nonlinear Creep of Polyethylene Nanocomposites
A compatibilized linear low density polyethylene (LLDPE) modified by montmorillonite layered silicates (MLS) was analyzed for nonlinear creep. To separate the influence of the compatibilizer and the MLS, separate systems of LLDPE with the compatibilizer, LLDPE with MLS were also investigated. Tensile tests were done on all samples. The samples were then loaded to 50% of their yield stress and creep was conducted for an hour followed by an hour of recovery.The viscoelastic nature of polymers was used to explain creep behavior in PE nanocomposites. Nonlinearity in the creep response was modeled using mechanical analogs such as Burgers model.
Enhanced Wood-Plastic Composite utilizing Controlled Architecture Materials (CAM)
Controlled architecture materials (CAMs) (ie. Block copolymers) are being explored as specialty additives in wood polymer composite processing with the goal of improve processing, surface aesthetics, reducing edge tear, improving flexural and tensile strength. Performance testing of these materials versus known additive systems in profile extrusion and injection molding environments are reported. Migratory additives based on fluorinated block copolymer s and their ability to modify polyolefin surface properties at low loading levels and low fluoromonomer content are introduced.
Development of Combined Socket and Butt through Transmission Infrared Welding of Polyethylene Pipes
Welding of polyethylene (PE) pipes of different diameters is critical for the infrastructure of gas transmission as well as for numerous other industrial applications. A relatively new method of combined socket and butt through transmission infrared (TTIr) welding was developed. A prototype infrared welding system was constructed and it was used to evaluate the effects of welding parameters on the combined socket and butt welding of 60 mm outer diameter high density PE gas pipes. In addition, we evaluated the effects of coupling thickness on power transmission of the infrared radiation and the effects of coupling thickness and width on weld strength. Under the correct welding conditions it was possible to create very strong welds without deformation of the coupling, no discontinuities in the butt joint, and with minimum inner bead. The size and shape of the inner bead was also found to be a good indicator of weld quality and it may be useful for inspection of completed welds.
Portable, Tube-Based XRF Analyzer for Quick PPM-Level Metals Analysis in Polymers
A portable tube-based XRF analyzer provides fast, confident screening and sorting of polymers during manufacture, recycling and disposal. It rapidly sorts PVC, Br- or Sb-based plastics and quantifies Cl, Br and Sb content with excellent detection limits. The analyzer also quantifies As and other toxic metals such as Pb, Cd, Hg, and Cr for compliance with ECD2002/96/EC & RoHS (Restriction of Hazardous Substances) for WEEE (Waste Electrical/Electronic Equipment). X-ray tube-based XRF systems replace the need for multiple isotopes and eliminate their burdensome radioactive source regulatory issues, particularly for interstate and international travel. Integrated PDA & iPAQ Pocket PC affords flexible software, exceptional graphical user interface & conventional MS windows architecture. This also makes available value-added accessories like wireless email and data transfer, global positioning, binary storage, and multiple language display.
Nanocomposites of Polyamide 6/Metallocene Polyethylene/Grafted SEBS with Montmorillonite
Nanocomposites of montmorillonite (MMt) and ternary blends of Polyamide 6/Metallocene Polyethylene/SEBS grafted with diethyl maleate (PA6/mcPE/SEBS-g-DEM) and maleic anhydride (PA6/mcPE/SEBS-g-MA) were prepared in an internal mixer (Rheomix) in order to improve the toughness of the nanocomposite counterpart prepared with PA6 and MMt. The PA6/MMt nanocomposite was the matrix or continuous phase whereas the mcPE was the dispersed phase and the grafted SEBSs were the compatibilizer agents. Tensile properties were measured and transmission and scanning electron microscopy were used to characterize the nanoclay and phase dispersion, respectively. The results showed that the incorporation of the metallocene polyethylene produced a decrease in the embrittlement of the nanocomposite unfolding a higher rupture strain. The use of SEBS-g-MA instead of SEBS-g-DEM is a better alternative from the mechanical behavior point of view. TEM micrographs showed that tactoid, intercalated and exfoliated structures were obtained.
Analysis of Heat Transfer in Combined Socket and Butt through Transmission Infrared Welding of Plastic Pipes
Combined socket and butt through transmission infrared (TTIr) welding of plastic pipes involves radiant heating of an absorbing element that is placed at the weld interface with air cooling of the exterior of the socket. For successful welds it is important to minimize deformation of the socket while providing sufficient heat input to form the butt weld. Therefore, modeling of heat flow is important. To better understand the heat flow that occurs, infrared radiation transmission measurements were performed for couplings of different thickness. Thermocouples were also used to measure the temperature history in the pipe. The experimental results were then compared to analytical models as well as complex finite element models of the heat flow. Good agreement was found between the experimental results and the theoretical models. These models can be used as a tool to analyze and optimize the heating and temperature in the weld zone under different welding conditions.
Interfacial Effects in Replication of Nano-Scale Features
While injection molding provides the ability to produce nano-scale features at high rate high volume, the interfacial effects between the polymers melt and the tooling become more critical than with macro-scale parts. Parts molded from four amorphous materials, a cyclic polyolefin, polystyrene, polycarbonate, and polymethylmethacrylate, were characterized for part replication using atomic force microscopy. Part replication (i.e, depth ratio and feature definition) were correlated with the measurements of contact angle which then can be quantitatively converted to the wetting and surface tension. Suggestions are made for improving the replication of nano-scale features.
Three Dimensional Fiber Orientation in Vibration Welded Joints of Glass Fiber Reinforced Polyamide-6
A technique to obtain fiber orientation distribution was developed for the vibration-welded joints of polyamide-6 with 30% glass fiber. The heat affected zone (HAZ) of fiber reinforced polyamide-6 was successfully revealed by polishing and etching the HAZ. Under the polarized microscope in reflected light, detailed microstructure domains including bulk crystal zone and HAZ were observed. To obtain quantitative measurement of three dimensional fiber orientation distribution, orientation tensors were calculated from elliptical fiber cross section images. The fibers in HAZ were highly oriented toward the squeeze flow direction compared to the bulk phase. Thicker HAZ does not guarantee more random fiber orientation by average but higher fiber population more randomly oriented. High weld pressure at low amplitude promotes fiber reorientation in the tensile direction and thus weld strength.
Thermal Stress Analysis of Plastic Processing Tools
To transform the plastic materials into final products, plastic processing tools have to go through heating and cooling cycles. The dramatic temperature change develops thermal stress, often to a level where the tools start to crack. In this paper, we first reviewed the fundamentals of the thermal stress and strain. Then two case studies were presented to demonstrate the importance of considering the thermal stress in tool design. The CAE simulation proved that both cast skin tool and injection molding tool cracked due to high thermal stress. To reduce the thermal stress, the cast skin tool was required to allow freer expansion and contraction through using less constrained clamps, while the injection molding tool had to beef up the tool design at the weak spot.
Study of the Properties of Polypropylene/Cassava Starch Composites
The purpose of this work was to study the effect of incorporating cassava starch, in proportions of 10, 15 and 20 wt%, into Polypropylene (PP). All composites were mixed in a co-rotating twin-screw extruder. Blends were characterized using the DSC, TGA and Capillary Rheometry techniques. Tensile properties were also evaluated. Results obtained indicate that the crystallinity degree remains unchanged when the filler is incorporated. However, when the compatibilizer (Polybond 3150) is added, the crystallinity degree decreases independently of its percentage in the composite. All blends showed a pseudoplastic behavior and a rise in melt viscosity when the filler content was increased. Regarding the mechanical properties, an increase in Young’s Modulus and a decrease in elongation at break were obtained when cassava starch content was increased. The addition of Polybond produced a significant increase in the Young’s Modulus values.
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