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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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.
Visualisation of Degraded Parts by Applying FT-IR Imaging and EDS Analysis
Generally, a durability evaluation of plastic pipe is performed by mechanical test such as tensile test and impact test after accelerated degradation test, whereas there is few research of polymer analysis with spectroscopy for these plastic pipes. However, it is very important to analyze the degradation process for improvement of reliability and long-term usage. In this investigation, we demonstrate the visualization of degradation parts and try to evaluate the degradation of PE-RT pipe after stress rupture test at high temperature by using FT-IR imaging and SEMEDS analysis. From results, it was found that there are many cracks on the inner surface of PE-RT pipe when the pipe ruptured with degradation. In addition, it was found that the inner surface and crack part of PE-RT were not only oxidation but also adsorption of metal ions in water. These results were visualized by using SEM-EDS analysis and FT-IR imaging.
The Real-Time Determination Algorithm of Mold Temperature Stabilization
In order to stabilize the part quality and minimize unnecessary cycles for temperature stabilization, it is desirable to determine the mold temperature stabilization in real-time. In this work, real-time mold temperature stabilization determination algorithm is developed. For an efficient operation of the algorithm, the initial mold surface temperature in each cycle turned out to be appropriate. To determine the stabilized state reliably, a determination criterion using the mold temperature changing rate was suggested. Developed algorithm was installed to an embedded device, showing a reliable operation even in a noisy condition.
Biodegradable Latex Paper Coatings Based on Polyhydroxyalkanoates for Improved Moisture Resistance
Polyhydroxyalkanoate (PHA)-based latex paper coatings were investigated for improved water resistance in Kraft paper samples. Cobb testing of samples with paper coating weights ranging from 10-30g/mý indicated improved moisture resistance with coating thickness as well as improved performance through heat treatment of the samples. Microscopy investigations indicated the formation of localized concentrations of surfactant after exposure to water. The PHA-surfactant structure and the effect of the annealing process on moisture resistance were investigated.
Using Multiple Morphological Methods to Understand the Processing/Structure/Property/Behavior of Olefinic Microporous Battery Separator Membranes
Today?s cell phones and many other microelectronic devices commonly utilize lithium ion based batteries that in turn depend on effective microporous membranes as battery separators. The materials utilized for these are typically either linear high density polyethylene, PE, or isotactic polypropylene, PP, or a combination of these two materials in layered form. These have been in existence for many years and they are made in a multiple-step process that begins with the melt extrusion of the given polymer(s). This invited presentation, meant to display the importance of understanding morphological structure in view of processing as well as the final properties, will use such single layer separators as an example system to demonstrate several of the many useful morphological tools available to the engineer or scientist. It will be shown that they provide understanding of the final structure of such systems in view of the process steps the material is put through to achieve the desired porosity for these important semicrystalline membrane materials.
Thermal Conductivity of Carbon Fiber/Carbon Nanotube Hybrid-Filled Polymer Composites
In order to improve compatibility between fillers and matrix, and reduce the scattering effect of the interface flaws on phonons movement, we used carbon fiber(CF) modified with polyamide solution and carbon nanotube(CNT) coated with nickel as fillers to fabricate thermal conductive polyamide(PA) composites. The surface states of different modification methods on CFs were tested with FRA and the microstructures of the composites were analyzed with scanning electron microscope(SEM). The results show that coated nickel CNTs not only disperse in the matrix well, but also attach to the surface of modified CFs easily as well. The thermal conductive network formed between CFs and CNTs through their adsorption of surface functional groups, which is beneficial to increase the mean length of phonons movements. Compare to the composites filled with CFs and CNTs without surface modification, the thermal conductivity of the composites, filled with coated nickel CNTs and surface modified CFs, increase by three times. Meanwhile, their mechanical properties increase also because of improved interface microstructure.
Matrix Effects on Long Fiber Orientation Distributions within Injection Molded End-Gated Plaques
The Method of Ellipses (MOE) was applied to long
fiber polymer composites in order to quantify the fiber
orientation distribution within injection molded end-gated
plaques. The effect of matrix viscosity and fiber type on
orientation was explored. Orientation was examined along
the centerline at the mold-gate interface, near the advancing
front and at multiple plaque widths at half of the plaque
length. Preliminary data suggests that the matrix viscosity
has a larger effect on the orientation of the fibers than if
glass fiber (GF) or carbon fiber (CF) is used. A more
viscous matrix caused a more distinct shell-core-shell
orientation profile. CF appeared to orient faster than GF
which is likely due to a shorter aspect ratio. Work is
ongoing to obtain the orientation of GF polymer samples
with different initial fiber lengths and along the plaque
Producing Cross-Linked Polycarbonate ? Challenges and Benefits
The benefits of polycarbonate include inherent toughness, transparency, relatively high temperature stability, and wide flow range. These properties have long led to usage in applications that require good aesthetics, dimensional stability, and strong mechanical properties. Looking to build upon these benefits, a new polycarbonate has been developed with a UV-active ketone incorporated in to the resin which allows for cross-linking of the polycarbonate when exposed to UV. This UV-active polycarbonate has similar physical properties to standard polycarbonate (tensile strength, Izod impact, melt flow, etc.). Yet after UV exposure, the new resin shows improvements in chemical resistance and flame retardance of polycarbonate.
X-Ray Nanotomography of the Skin-Core Structure of Injection Molded Composites
Microstructure development during polymer processing is of interest for manufacturers in engineering the final properties. Injection molding advancements have facilitated molding components with complex geometries. With industry moving towards minimizing the polymer waste while retaining the component properties, it is necessary to understand the microstructure formation in detail. Progresses in the field of X-ray imaging techniques have made it possible to characterize polymers with sub-micron resolution. In the current work, we show the applicability of X-ray nanotomography in quantifying the skin-core morphology resulting from injection molding.
Continuous Extrusion of LLDPE Films Modified with Hexagonal Boron Nitride Nanoplatelets
Linear low-density polyethylene (LLDPE) films containing boron nitride nanoplatelets (BNN) and were fabricated by continuous melt extrusion. The inclusion of BNN led to 10-fold increase of the in-plane thermal conductivity of the nanocomposite (7.7 W/m.K vs. 0.3 W/m.K for pure LLDPE). To increase the surface area available for convective heat transfer, micro-textured films (T-BNN) were produced from a micro-patterned die. Nanoplatelets oriented parallel to the film machine direction. Nanocomposite films lose ductility for a very high BNN content, but retain their stiffness and tensile strength as compared to the base LLDPE. BNN addition to the LLDPE decreased coeffiecent of friction by 50%, and mixrotextures raised this decrease by 7% more.
Producing Long Chain Branched Polymers from Linear Polyolefins
Polyolefins, (polyethylene and polypropylene) are arguably the most commonly used thermoplastics used today in a broad range of processes and applications. There are hundreds of types of polyolefins that can be produced directly from the polymerization reactor considering
co-monomer type and concentration, molecular weight and molecular weight distribution etc. However, even with today?s state of the art process technology, not all of the polymer attributes required by many applications are achievable at the reactor level. Of the polyolefin family, only low density polyethylene inherently exhibits excellent melt strength resulting from it?s highly long chain branched structure. While the physical properties of linear low density polyethylene (higher tear and puncture resistance), high density polyethylene (higher stiffness, toughness) and polypropylene (higher stiffness, clarity, high heat resistance) may be more desirable for a particular application, they all exhibit poor melt strength due to their linear structure.
This paper reviews the history, techniques and practical application of modifying readily available, ?reactor grade? linear polyolefins to produce long chain branching. Some of these materials exhibit rheological properties comparable to or exceed the melt strength of low density polyethylene while maintaining 100% of their original properties. Examples of their commercial practicality will be discussed in terms of value in application.
Plastic Packaging Modeling: Interactions with Food. Model and Method to Estimate the Shelf Life of Oxygen-Sensitive Food Products
A model to estimate the shelf life in oxygen sensitive food products is proposed. The kinetics of oxygen consumption of the food product and the permeation properties of the package are considered. A novel method to characterize the oxygen consumption is discussed. Some results for an oxygen-sensitive product are presented. The model and method proposed are very useful for developing new products and for making decisions about the selection of film and packaging conditions according to the shelf life expectations.
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