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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A Walk around the Color Sphere: Effect of Titanium Dioxide Particle Size Distribution on Color of Plastics
?Black? and ?White? pigments are often referred to as colorants because they can influence the color properties of finished products in the plastics industry. One of the most common ?white? pigments used in the plastic industry is rutile titanium dioxide. This review provides an example of how various types of titanium dioxide materials can impact the overall color of plastics. Three different titanium dioxide (TiO2) grades were compounded into a soft PVC containing with a fixed amount of carbon black and the resulting CIE L*a*b* tri-stimulus values were measured. The primary difference amongst the titanium dioxide samples was their median particle diameter. Each titanium dioxide material resulted in a unique color space, As the amount of each pigment was increased in the soft PVC formulation, it was interesting to observe that the tri-stimulus values march towards the ideal white co-ordinates of L*= 100, a* = 0, and b* = 0, but follow different paths. In other words, the tri-stimulus values walk along the color sphere in different paths, but all tending towards the same point. At a given concentration of titanium dioxide, the smaller particle diameter pigment approached the ideal white the most amongst the three pigments. The highest Whiteness Index (WI) was achieved by the titanium dioxide with the smallest particle size diameter.
Fiber Orientation Measurements Using a Novel Image Processing Algorithm for Micro-Computed Tomography Scans
Based on previous work at the Polymer Engineering Center, Madison, a novel image processing algorithm has been developed that accurately analyzes fiber orientation distribution in discontinuous fiber-reinforced composites. The developed algorithm is an accurate and time-efficient method to measure the fiber orientation distribution of micro-computed tomography (?CT) scans. In this work, the image processing algorithm is described and verified experimentally. Additionally, the algorithm is compared to a commercially available benchmark software package. In this test case, ?CT scans of samples extracted from compression molded parts were used to evaluate the performance of the algorithm by comparing it to the benchmark. In all cases, the algorithm shows highly accurate fiber orientation measurements and the results show that it can compete with the benchmark software.
Bio Based Active Barrier Materials and Package Development
The food and packaging industry are interested in approaches to reduce the permeability of oxygen in Polyethylene terephthalate (PET) to extend product shelf-life. The purpose of this work is to investigate use of unsaturated fatty acids as O?2 scavengers to reduce the permeability in PET. The focus was to characterize the scavenger and to develop methods to incorporate them within PET packages. Linoleic acid was chosen based on oxygen capacity and uptake kinetics. Reactive extrusion was utilized to make pellets of PET/scavenger and blown into bottles. The presence of the scavenger in the polymer was determined using TGA and extraction. Permeability of O?2 through bottle sidewall in PET/scavenger system was measured and compared with base PET. The PET scavenger system exhibited decreased O?2 permeation with little changes in thermal and mechanical properties.
How Is Electrical Percolation Achieved in Nano Doped Materials? Direction towards More Efficient Doping
One route to create electrically conductive polymeric material is to dope them using highly conductive nanoparticles such as carbon nanotubes. It is well known that, when a threshold volume fraction is reached, a percolated network is achieved in which efficient conduction can take place. In such a network, inter particles charge transfer takes place over a very short distances, when particles become close enough to each other so a tunneling mechanism becomes possible. It follows that most of the introduced particles are not linked to the percolated path, thus not participating in the doping mechanism. The spatial arrangement of the particles plays a major role in the way they are participating in the increase in macroscopic electrical conductivity. We propose here to go further than the usual method of quantifying filler content based on weight/volume fractions by studying in detail the topology of the particle arrangement. This provides an in-depth understanding about how the conductive path develops when increasing the filler content and paves the way for an optimal use of the doping particles.
Thermal and Rheological Analysis of Nucleated LLDPE Resin. Determination of Crystallization Kinetics Parameters
The effect of a commercial nucleating agent i.e HPN20E on the thermal and rheological properties of LLDPE M500026 resin was successfully studied. The crystallization temperature increased by about 7§C and the crystallization % decrease when a NA is added. Non-isothermal crystallization parameters were determined. The lower Ea value for LL50-NA indicates easier crystallization in the presence of a nucleating agent.
Time sweep rheological experiment proved to be a powerful technique to evidence the effect of a nucleating agent. Hot stage microscopy confirmed the role of a NA in reducing the size of crystallite
Modeling of Tension-Compression Asymmetry in Fiber-Filled Engineering Thermoplastic Materials Using LS-DYNA
Fiber-filled engineering thermoplastic (ETP) materials such as THERMOCOMP?, VERTON? and STAMAX? compounds are used across various domains such as aerospace, automotive and fluid engineering. For such materials, Young?s modulus (E) in tension may be very different than that in compression. Most of the commercial simulation software used for non-linear static analysis does not have a material model to simulate the structural deformation of a component having differential mechanical properties under tension and compression. The assumption of using the lower value of E, between that of tension and compression, in the material model leads to an over prediction of the design deformations. On the other hand, the usage of higher E value leads to an under prediction of the actual deformation which could result in an unsafe design condition. This paper explores advanced material modeling capability available within the LS-DYNA commercial code to simulate the aforementioned material behavior. In this work, a methodology to perform a quasi-static simulation using LS-DYNA explicit solver for materials with unequal tension-compression modulus is proposed and is validated against a practical field problem.
Development of Electrically Conductive PVDF/PET Systems
Polyvinylidene fluoride/poly(ethylene terephthalate) (PVDF/PET) based composites for proton exchange membrane fuel cell (PEMFC) bipolar plates (BPs) were prepared at different crystallization temperatures and characterized by X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and resistivity setup. Composite conductivity was made possible by using a mixture of carbon black (CB) and graphite (GR). To improve composite processability, its viscosity was reduced by adding a small amount of cyclic oligomers of butylene terephthalate (c-BT) and thermoplastic polyolefin elastomer. In the PVDF/PET based composite, it was found that PVDF phase could crystallize easily but PET crystallization was difficult. Due to CB/GR additives, the formed crystals in PVDF/PET phases had a poor perfection degree and showed a lower melting temperature compared to pure PVDF and PET. It was observed that PET nucleation was accelerated but not that of PVDF. According to through-plane resistivity results, composite crystallization temperature range was divided into two parts (below/above 170oC) where there was a different variation behavior of through-plane resistivity. It has been proved that the resistivity was mainly governed by the network of CB/ GR developed inside the PET phase, and decreasing the crystallinity of PET led to a decrease of through-plane resistivity, which is desirable for BPs.
The Use of Nucleators and Clarifiers in Polypropylene
Polypropylene is one of the most common plastics, and its use in many applications is a result of the excellent balance of physical properties that PP displays. The solid state properties of polypropylene are very dependent on the crystal morphology of the final part. One common way of controlling the crystal structure and the overall crystallinity of PP is through the use of nucleating agents. These additives provide surfaces on which polypropylene crystallites can form when the molten polymer is cooled. The chemical and surface characteristics of the nucleating agent affect the type of polymer crystals that form, the size and distribution of the polymer crystals, and the percent crystallinity in the final part. Nucleating agents also influence the appearance of the part, and they can have a dramatic effect on processing behavior and the rate of crystallization.
In this talk we will review the basic principles of polymer crystallization and nucleation. This discussion will include examples of nucleating agents that induce the formation of the more common alpha crystal form of PP as well as the less common beta form. Many examples of nucleated products ranging from molded parts and oriented films to extruded and thermoformed plastic parts will be included in this discussion. A particular type of alpha nucleant known as a clarifier, which is used to produce high clarity parts, will also be discussed.
Virtual Fine-Tuning of a Profile Coextrusion Die using a Three-Dimensional Flow Simulation Software
Die geometry of a bilayer die for coextrusion of a PVC window profile is fine-tuned for a uniform exit velocity distribution by using a flow simulation software. Besides the flow inside the die, the post-die flow of extrudate, including the flow in the calibrator of the profile die, is simulated. The pressure drop and the changes in the extrudate shape predicted by the software are in good agreement with the corresponding experimental data. It is estimated that the virtual fine-tuning of the die using the software saved two fine-tuning cycles in the experiments, resulting in a significant saving in the cost and the lead time for the profile die development.
Filtration Media Using a Melt-Based Processing Technique
Fibrous filtration media were produced using a novel melt-based co-extrusion and two-dimensional multiplication technique combined with a high-pressure-water delamination technique. These cross-plied, fibrous filters have integrity and mechanical strength in two dimensions. The orientation procedure greatly improves the fiber orientation, decreases the fiber sizes, and enhances their mechanical performance. In comparison with the commercial product, the filters produced from the oriented tapes have superior mechanical properties, larger surface area, smaller pore size and higher porosity, which are indicative of improved filtration performances. This melt-based, versatile technology is applicable to any melt-processable polymers, and allows tunability of the filters? surface area, pore size, and porosity, and makes these filter materials good candidates for various filtration applications.
Continuous Extrusion of Nanocellular Foam
Nanocellular foams are typically produced with supercritical CO2 by a solid state batch foaming process. Low temperatures allow for the stabilization of a high number of nuclei that can be generated by controlling the pressure and pressure drop rate. Yet such a process is not easily applicable to future commercial production due to long saturation times and finite autoclave volume.
This limitation can be removed by adapting the nanofoaming process to continuous production. Modifications to a simplified foam extrusion system made it possible to produce sub-microcellular acrylic foams with bimodal and monomodal cell distributions. Optimization of extrusion conditions led to homogeneous nanofoams with four-fold expansion and cell nucleation densities over 1014/cm3.
Nucleation of Polypropylene during High Speed Processing
Nucleation is one important tool for tailoring mechanical and optical properties of polypropylene (PP) as well its processability in various conversion technologies. Especially the latter aspect is gaining more and more importance in the light of sustainability and energy efficiency discussions, as shorter cycle times and high line speeds are aspired. The efficiency of a nucleating system is commonly determined by the crystallization temperature (Tc) of the resin as measured by differential scanning calorimetry (DSC), typically at 10 K/min. However, Tc is strongly dependent on the cooling rate. Thus, at processing relevant conditions (cooling rate 100-6000 øC/min resp. up to 100 K/s) a suppression of the nucleation effect is frequently observed, and in certain cases the nucleating agent can become completely ineffective. In this study, the crystallization behavior of polypropylene heterophasic copolymers, containing state-of-the-art nucleating systems has been compared. Non-isothermal and isothermal crystallization experiments were performed by DSC and by fast scanning chip calorimetry (FSC) at cooling rates between 0.02 and 3.000 K/s. The data obtained suggest significant differences regarding the crystallization rate. The results are discussed in light of the molecular architecture of the polymer and the type of nucleating system.
New Phosphorus Based Flame Retardants: For Thin-Walled Applications
Building on more than 30 years expertise in phosphorus chemistry and flame retardants (FRs) for textiles, Thor (www.thor.com) has recently developed an extensive range of non-halogenated FRs dedicated to plastics applications. Cornerstones of the portfolio are two new substances, AFLAMMIT? PCO 700 and PCO 800 that have been registered under REACH and TSCA, and another proprietary high-performance FR, AFLAMMIT? PCO 900.
While they can be used in various polymers, thicknesses and applications, these new substances are expected to find commercial use primarily in polyolefin based thin-films, tapes or foams, where they fill the gap between traditional formulations (based on organic bromine or chlorine based FRs and antimony trioxide) and the available halogen-free additives, which are essentially limited in performance.
The paper will introduce the new AFLAMMIT? products and their synergistic combinations in a benchmark approach and will demonstrate their unique FR effectiveness. These new additives not only represent the first halogen-free alternatives to the widely used halogenated compounds in the targeted applications, but have also demonstrated to be successful in particular applications without halogen-free requirements, where performance based criteria are most important (i.e. highly flame-retarded films preserving transparency or light-weight FR thermoplastic foams).
Controlling the Architecture of Tissue Engineering Scaffolds in Extrusion-Based Additive Manufacturing: the Effect of Extrudate Swell
Organ failure is a costly burden on human healthcare. A paradigm shift is taking place in medicine, from tissue grafts and synthetic implants to regenerating tissues and organs. The tissue engineering approach using 3D scaffolds is a novel alternative to conventional repair techniques. In recent years, additive manufacturing has become the method of choice for developing 3D scaffolds with controlled internal architectures. Among these techniques, melt extrusion-based additive manufacturing, or fused deposition modeling (FDM), has been used for the fabrication of polymeric scaffolds. Optimal design of scaffolds is critical for cell attachment and survival. However, rigorous control over scaffold architecture in FDM is highly restricted mainly due to pronounced variations in the deposited strand diameter (extrudate swell) upon any variations in process conditions and polymer viscoelasticity. We designed an I-Optimal, split-plot experiment to study the extrudate swell in FDM and to control the scaffold architecture. The result was scaffolds with an estimated modulus > 15 MPa, while respecting a constraint on scaffold density (< 0.65 g/cm3) corresponding to a porosity of > 40%.
In-Depth Study for the Different Physical Mechanism between over-Molding and Co-Injection Molding
Multi-component molding (MCM) has been developed and applied in our life for many decades. However, due to the complicated combination from materials to processes, it is very difficult to control and management for this type of product development. In this study, we have extended our study from over-molding to co-injection to discuss about the physical mechanism for both distinct interface and uncertain interface MCM systems. In over-molding MCM system, due to the unbalance volume shrinkage and heat accumulation or dissipation, the warpage can in inward or out ward. The final warpage quality can be managed and controlled. On the other hand, in co-injection MCM system, the warpage is strongly affected by the core penetration distance. In this study, the critical central core penetration distance is 36 mm. As long as the core penetration is greater than the critical value, the warpage can be improved. However, unlike over-molding MCM, since both corners (A and B) will be shrunk. To catch the target with good quality product, still need to further efforts. Moreover, the experimental conduction for co-injection MCM will be performed in coming future.
Transparent Permanent Antistatic Polycarboname Blend by Reflactive Index Matching Technology
Antistatic/dust and ESD management demands are increasing at electronics relevant use plastics especially semiconductor handling area. Transparent performance also needed at specific area because confirm able inside without opening box to minimize contamination from outside. Electrical conductive carbon filler is one option, but it?s tough to achieve both these performance. On the other hand, primary antistatic agents like a surfactant type are questioned for their duration of the antistatic performance. This paper discusses refractive index matched transparent antistatic polycarbonate and polyester blends that offer transparency, sustainable antistatic performance, and cleanliness (lower out gassing, leachable ions).
Flow Behavior of Thermoplastic Starch-Blends
In this study a polyethylene modified with thermoplastic starch (TPS) is investigated and its rheological behavior is shown. The unmodified polyethylene has a common shear thinning behavior whereas the thermoplastic starch presents a typical elastomeric flow property. The complex viscosity shows a strong dependence of the TPS volume fraction. To describe the flow properties over a broad range of shear rate, a new empirical approach was created, based on the Carreau and the Ostwald de Waele equation. The approach shows very good consistency with experimental results compared to other models from the literature. The parameters of the approach can be explained physically and show strong dependence of the TPS concentration. Furthermore the maximal force acting between the particles can be calculated based on the model parameters and the structure of particle network can be quantified by the fractal dimension. Futhermore an improvement in the mold construction can be achieved through a better modelling.
Investigating the Influence of Filler Type, Particle Size and Weight Fraction on Rheological and Thermal Behavior of Polypropylene/Blast Furnace Slag Microcomposite
The aim of this study is to assess the rheological and thermal performance of polypropylene (PP) composites filled with blast furnace slag (BFS) filler. Two filler types, crystalline and amorphous, were ground into three micro-sized batches: 71, 40 and 20æm and each introduced without treatment to BB412E-grade PP via melt kneading. So composites with 10, 20 and 30 wt% filler were prepared, formed into plates by means of compression molding and then subjected to rheological and thermal investigation. Type of filler did not show any noticeable effect on rheological and thermal behavior, while particle size and content did. As expected, complex viscosity, storage modulus and loss modulus curves slightly shifted to higher values with increasing filler content. Composites with 40æm filler size showed best rheological performance regardless of filler type. Slight shifting to lower and higher temperature values was observed for crystallization and melting peaks. In addition, decrease of filler size and/or increase in filler amount lead to a decrease in enthalpy and crystallization degree
Evaluating the Efficiency of Nucleation Agents in Polypropylene by Means of Isothermal Crystallization and Kinetic Modelling
Semi-crystalline polymers like Polypropylene (PP) or Polyamide (PA) undergo a crystallization process during cooling from the melt, initiated by initial crystal nucleation, followed by crystal growth. The nucleation process is not only dependent on the cooling profile and the resins nature but it can be influenced by nucleation additives. These additives can increase the crystallization temperature and rate as well as the degree of crystallinity. For thermoplastic processing like injection molding it is favorable to have a high crystallization temperature to reduce required cooling time. Additionally a high degree of crystallinity improves mechanical properties like strength and toughness. However, for material developers and molders it may be of severe advantage to fully understand the crystallization process as a function of additive type and concentration, to model their kinetic parameters as well as to predict its behavior at processing relevant temperature profiles. Therefore isothermal crystallization experiments by means of Differential Scanning Calorimetry (DSC) are employed using a newly developed heat-flow DSC with a very fast furnace to study the efficiency of two different types of nucleation additives in PP. The measurement data were used to model the crystallization kinetics with Avrami-approach using sophisticated Thermokinetic software. Kinetic modelling allows comparing nucleation efficiency of different additives.
Crystal Morphology of Biodegradable Poly(Lactic Acid)/Graphene Oxide Nanocomposites and the Isothermal Crystallization Kinetics Research
The biodegradable poly(lactic acid) (PLA)/graphene oxide (GO) nanocomposites were prepared successfully at various GO loading by solution casting. Wide angle X-ray diffraction (WAXD) showed the layered GO were exfoliated in the nanocomposites and well distributed. Evident crystallization peaks were observed in the PLA/GO nanocomsites rather than neat PLA in the nonisothermal melt crystallization test, which indicated the GO was an effective nucleating agent. For isothermal melt crystallization, the overall isothermal melt crystallization rates were signi?cantly greater in the nanocomposites than in neat PLA. The crystallization rates decreased with increasing crystallization tempera?ture. The incorporation of GO did not affect the crystal morphology of PLA in the nanocomposites, but it contributed to more regular and perfect crystallization structure.
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