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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Blow head design and optimization
Major sectors with high demands and specifications for polymer products are packaging and automotive. Due to the complexity of polymeric materials and the high specifications regarding the product quality and e. g. homogeneity of wall thicknesses, a key issue is the rheological design of the extrusion die that is used for the primary forming of the polymer melt. Usually, numerical die design approaches (e. g. based on computational fluid dynamics) are time consuming, costly, tie down manpower and highly depends on the experience and training of the responsible engineers. Applying a holistic approach based on the analogy between electrical engineering (voltage, current, resistance) and hydrodynamics (pressure drop, volume flow, flow resistance) offers a promising way to achieve good die design results very time efficient. In order to describe flow phenomena the control volume approach (also referred to as network theory) is used and a simulation model for complex multi-level extrusion dies is implemented. Interdependencies between different levels of the extrusion die are taken into account. The approach aims for a fast and automatic flow calculation. The results of the flow simulation are compared against user specifications and a quality value is computed that describes the quality of the design. This value is used for optimization techniques tin order to develop a smart and time-efficient way to find optimal solution for complex multi-level extrusion blow heads.
Phase Inversion- Assisted Synthesis of Electrospun Nanoporous Polycaprolactone (PCL) Fibers for Protein Adsorption
Impregnation of desirable biological moieties can significantly enhance the biocompatibility of an electrospun scaffold. Nanopores provide additional impregnation or attachment sites for target bio-molecules on scaffold surface. In the present work, a combination of vapor and non-solvent- induced phase inversion processes was used to create 20 - 200 nm sized pores on PCL fibers. 24-hour adsorption studies, performed with Collagen-I protein, showed a 2.5 fold increase in protein retention of porous fibers over their non-porous counterparts, thus exhibiting efficacy of the high surface porosity. The pore size distributions can be tailored by controlling key parameters i.e. relative humidity and solvent/non-solvent ratio to enhance the loading of target molecule.
Crystalline Structure of Blends of Isotactic Propylene-1-Hexene Copolymers Revealed by WAXS/SAXS Techniques
Blends of a miscible pair of propylene-1-hexene (PH) copolymers with 11 and 21 mol% of 1- hexene have been studied in reference to their polymorphic behavior, kinetics and crystal structure using in situ WAXS and SAXS analysis. PH21 crystallizes in a trigonal packing in the whole range of undercooling, while PH11 develops monoclinic crystallites (at low undercooling) or the mesomorphic form (at high undercooling). The level of crystallinity increases from 17 to 25% and scales directly with increasing content of PH21. WAXS analysis indicated that while the content of trigonal phase decreases with increasing PH11, the rate of formation of trigonal phase in the whole range of undercooling increases with addition of PH11, which as a pure component does not form trigonal phase. The unexpected enhanced kinetics of formation of trigonal phase with blending is attributed to the increasing composition of 1-hexene in the melt during evolution of the monoclinic phase in the first stage of isothermal crystallization of the blend.
Novel Prototype to Study the Effects of Helical Spiral Flow on in-vitro Biodegradation of Polymers for Bioimplants
There are currently no tests to determine degradation rates and characteristics of bioabsorbable materials that come in direct contact with blood. Blood follows a helical flow pattern resulting in conditions not simulated in current degradation tests. This is of concern to the degradation of stents because certain stent designs have the potential to liberate fragments large enough to induce strokes or other detrimental health concerns. A novel prototype designed to simulate in vivo conditions including flow rates, pressures, temperatures, and flow characteristics was designed and built. This system was designed with a fast change testing chamber to allow sample removal and different configurations to simulate different sized arteries and cardiovascular health levels. The critical consideration for the testing chamber was the silicone artificial artery to simulate helical flow found in blood vessels. The effects of this flow pattern were compared to laminar and turbulent flow patterns and optimal conditions found to best simulate actual body conditions. Degradation of polymers was characterized with weight loss of the sample, visual inspection via camera, and observed fragment size running through meshes to indicate size.
Manufacturing Induced Curvature of Carbon Fiber Laminates: Experimental Observation and Model Validation
Carbon fiber composites are used frequently in a wide variety of industries; such as automotive, aerospace and sports equipment, primarily due to their large strength to weight ratios. The design and manufacturing of such parts, as well as the final part's performance, create engineering difficulties as compared with alternative materials and processes. As a carbon fiber composite is manufactured, strains are formed due to the curing kinetics of the resin matrix and thermal effects caused by a mismatch in the coefficient of thermal expansion between the carbon fibers and the resin matrix. This work compares the curvature of an un-balanced (cross-ply) laminate with the curvature of a balanced laminate. The experimental results are compared with a finite element structural and coupled thermal-structural analysis which incorporates micromechanical theories to predict the stiffness and coefficient of thermal expansion of a lamina from the constitutive properties of the fiber and the resin matrix. The experimental and modeling results show qualitative and quantitative agreement.
Toughening of Polylactide with Pre-heat Treated Natural Rubber
Both polylactide (PLA) and natural rubber (NR) are biocompatible and biodegradable polymers. PLA possesses high strength and modulus but low toughness, while NR exhibits excellent elasticity and ductility. In view of their complementary properties, NR seems an ideal candidate to toughen PLA. To the best of our knowledge, PLA blends showed increased ductility only when more than 10 wt% rubber was added. This study demonstrates a significant improvement in the toughness of PLA by melt blending PLA with pre-heated NR. SEM studies showed that the rubber phase was uniformly dispersed in the PLA matrix. With as little as 1 wt% NR, the elongation at break and tensile toughness of PLA/NR blend were significantly improved over those of neat PLA (207% vs. 16% and 83 MJ/m3 vs. 9 MJ/m3, respectively) without loss in tensile modulus and stress. In addition, by blending in PLA with 20 wt% NR, samples obtained did not even break in the notched Charpy impact test. FTIR spectrum indicated that carbonyl groups were generated in NR chains after hot shearing and led to enhanced compatibility between PLA and NR, which accounted for the improved toughness
Recycling of PLA
Polylactide (PLA) is a bioplastic which has a high potential for packaging applications. Due to a high raw material prize and a limited availability the usage of PLA is limited apart from some niche products at the moment. Nevertheless, the number of applications is increasing. At the Institute of Plastic Processing (IKV) the recycling behavior of PLA is evaluated. Recycling helps to cut the raw material consumption and lowers material costs. Additionally, it improves the ecological balance. Following the industrial praxis different recycling strategies are analyzed. This paper gives a review about the multiple processing of PLA and the processing with melt degassing.
Comparison of Negative and Positive Tooling for Injection Molding of Microstructured Surfaces
Extensive research has been carried out on replication of negative micro and nanostructured surfaces injection molded using positive tooling. Limited studies, however, have investigated positive features created using negative tooling. In this work, we compared replication of injection molded positive and negative features with different geometries using two polycarbonates with very different viscosities and a copolyester thermoplastic elastomer. The tooling and part features were characterized for feature depth and height as well as feature definition using scanning electron microscopy and optical profilometry.
Effects of Dispersion on the Dielectric Properties of Multi-Walled Carbon Nanotube/Polystyrene composites
This study reports on the effects of multi-walled carbon nanotube (MWCNT) dispersion on the dielectric properties of MWCNT/polystyrene composites over the broadband frequency range, i.e., 10-1 – 106 Hz. Different degrees of MWCNT dispersion were achieved employing distinct composite preparation techniques, namely solution mixing and melt mixing. Characterization methods, such as light microscopy and transmission electron microscopy indicated better MWCNT dispersion in the solution-mixed samples. The results showed that, in the insulative region, which is desired for charge storage applications, the solution-mixed samples presented much better dielectric properties than the melt-mixed samples.
Analysis of the Interfacial Shear Strength of Banana Fiber in Low-Density Polyethylene
The increasing social pressure for biodegradability, environmentally?friendly products, and sustainable products for developing countries has launched the use of natural fibers in fiber reinforced polymer composites. Due to the integration of organic material in thermoplastics, the fiber?matrix interfacial bonding is quite poor. While the organic material is hydrophilic, able to absorb water, the majority of polymer matrices are hydrophobic, unable to bond with water. The interfacial shear strength, a quantity to measure this bonding, has been shown to be improved through morphological and chemical treatment. In this context, the interfacial shear strength of banana fiber in low?density polyethylene has not been fully characterized. The aim of this study is to analyze and improve the interfacial shear strength of banana fiber in a polymer matrix through a variety of surface treatment and modification techniques. For characterization of the fiber?matrix interfacial bonding, a commonly used micromechanical technique, the pull?out test, is used.
Advantages of a Servo-Driven Ultrasonic Welder
Ultrasonic welding is one of the most widely used processes for bonding polymers, valued for its speed, flexibility, and low cost. Recently, there has been a call for more controlled and consistent ultrasonic welding processes, as part designs become more complex and requirements more stringent. There is also a need for strong, dimensionally consistent parts that show good cosmetics and have minimal residual stresses. In addition, the processes used to meet these increasing demands must be consistent and repeatable over time. Dukane has worked to meet this demand through the development of a new iQ series Servo-Driven Ultrasonic Welder with MeltMatch™ technology. This study explores the potential benefits of using the MeltMatch™ (matching welding speed with the melt flow rate of the plastic) feature available on Dukane’s servo-driven ultrasonic welders. An effort has been made, to detail & quantify the improvement to the weld joint based both on previous research and new experimentation.
Comparison of Microstructured Surfaces Fabricated using Nanoimprint and Injection Molding
Hot embossing and injection molding are leading processes for the production of micro and nanostructured surfaces. The ability of these processes to replicate electroformed nickel tooling containing 0.5, 1, 10, and 50-?m positive and negative features was compared using several polymers. The tooling and microstructured parts were measured using scanning electron microscopy and optical profilometry. The processing conditions, replication (quantified using the depth ratio and feature definition), and overall quality of the parts were compared.
Effect of mixing time and temperature on the rheology and morphology of immiscible polymer blends prepared from polytrimethylene terephthalate [PTT] and polyamide 6,10 [PA6,10]. Kevin Lucero, Marissa
Thermoplastic immiscible polymer blends were prepared from polytrimethylene terephthalate [PTT] and polyamide 6,10 [PA6,10] by melt processing in a Brabender mixer to assess morphology developed between the immiscible domains. PTT and PA6,10 were selected as a pair of engineering polymers with complementary properties and as a blend prepared to significant extent from bio-based precursors. Overall, a 50/50 blend of these polymers has a renewable content of nearly 50%. The overall objective is to develop an engineering blend with good stiffness, strength, and dimensional stability while simultaneously being easy to process. In the present phase of the work, blend homogeneity was studied as a function of mixing time and temperature in the range of t=0-25 minutes and T=240-260 C. Results are presented in terms of torque versus time and temperature curves that are interpreted in terms of domain formation and SEM micrographs are used to define domain size and overall morphology.
Characterization of Novel One-Step Processed FG-PTT
PET, PBT and Poly (trimethylene terephthalate) (PTT), of the polyester resin family, potentially compete for the same engineering-grade thermoplastic market. PTT’s crystallization rate relative to those of PET and PBT, suggests its high suitability for injection molding applications. The aim of this work is to produce a viable PTT candidate for engineering structural applications. To this end, fiberglass (FG) reinforcement, a commonly used method of improving polyester properties, is in a one-step novel process blended with PTT at 10%, 15%, 20%, and 30% FG. The mechanical, rheological, thermal and morphological properties of the FG-PTT composite are presented.
What do polymer chemical segments do during stretching? Real time Ultra-Rapid- FTIR spectroscopy , birefringence coupled with true stress, strain measurements
The URS-FTIR is an one-of-a-kind machine developed by our group that allows collection of real-time data, which includes birefringence, true strain, true stress, and simultaneous tracking of full spectrum parallel and crossed polarized infrared spectroscopy of materials during uniaxial stretching of polymer films. This is machine is capable of acquiring both polarizations at 300 spectra/second during the uniaxial stretching. The real-time dichroic ratio is calculated by polarized infrared light, both parallel and perpendicular to the stretching direction; because of this, we are able to observe how the chemical groups behave during stretching, relaxation and subsequent annealing. This is particularly useful in examining semicrystalline polymers, multiphase systems such as copolymers, nanocomposites and their blends on their melting, orientation , relaxation and crystallization behavior enable us to peer into the mechanistic details of each phenomenon being examined, The design of the instrument, its performance and selected preliminary data will be presented on the poster.
Surface Modified Fillers at Polycarbonate Blends
Mineral fillers/reinforcing agents such as talc, wollastonite, clay and/or mica in polycarbonate- acrylonitrile butadiene styrene (PC/ABS) blends provide a technological pathway to increase specific mechanical properties like tensile strength, tensile / flexural modulus, simultaneously reduce warp in molded parts / articles fabricated from these formulations, as well as decrease the co-efficient of linear thermal expansion. The main challenge from a property balance perspective is to achieve high impact and toughness values in conjunction with high stiffness and tensile strength properties, since these properties typically tend to go in opposing directions. In this paper, routes based on employing surface treated mineral reinforcements to achieve exceptional impact properties are explored and discussed.
Consideration of the dimensional dependence and inlet fiber orientation assumptions in fiber orientation prediction modeling for fiber-filled thermoplastic composites
Computer predictive modeling of real-world physical systems has become of great interest in the recent years to optimize the design of manufactured parts. The plastic composites field have also benefited from computer modeling of the injection molding process to achieve the final mechanical properties of the processed part. This simulation uses fiber orientation models to predict the final orientation states throughout the part and then uses micromechanics models to predict the composite’s stiffness. The prediction of the fiber orientation is very complicated due to the fiber-fiber interactions. Several fiber interaction models have been proposed in literature; however, the global mechanical properties have not been compared to experimental testing to determine the most accurate interaction model. In order to compare the stiffness predictions from different fiber interaction models with experimental testing, an accurate simulation must be created to match the experimental conditions of the actual test. However, as typically is the case, the more detailed models require more computer power. In this poster, a two-dimensional model will be compared with a three-dimensional model of an ASTM flexural bar to determine if a two-dimensional assumption still maintains the necessary accuracy in the final predicted stiffness. In addition, a comparison of the inlet conditions of the fiber orientation will be investigated to determine the extent of their effect on the overall fiber orientation and resulting stiffness throughout the flexural bar.
Slow Crack Growth in High-Density Polyethylene Part II: Simulation Using Crack Layer Model
This paper aims to simulate slow crack growth in high-density polyethylene by using Crack Layer Model. We first derived the analytical approximations of stress intensity factor and crack opening displacement for finite geometries using close form solution of a semi-infinite crack and the numerical solutions for corresponding geometries. We then use the approximate solutions to assess the size of the process zone accompanying the crack, slow crack growth rate and mechanisms as well as the lifetime in brittle fracture of high-density polyethylene.
The Benefits of a Multivariate Analysis System on Fault Detection in a Wire and Cable Coating Process
The benefits of using a multivariate analysis system to improve closed loop control of a wire or cable extrusion line in order to improve process control are being studied. Multivariate analysis systems are currently most common in injection molding processes, but their potential for increased process monitoring on extruder systems is significant. The use of a multivariate analysis system has the potential to increase automation, process consistency, increase productivity, and reduce labor costs. The focus will be on biaxial dimensional stability through the monitoring of puller speed, screw speed, and the temperatures of the water bath, melt, and die.
On Process-Morphology-Property of Semicrystalline Poly (ether-block-amide) Pebax® Thermoplastic Elastomers in Micro Injection Molding Process
Polymer melts under micro injection molding process experience high shear rates and high thermal gradients, resulting in some unique morphology features. This paper examined the morphology of Pebax 7233 SA01 under designed experimental conditions. With measurement by cavity pressure and temperature (PT) sensors, shear rates and thermal gradients were quantitatively evaluated and related to morphology evolution. Unique spherulites were formed beside the skin layers, having a much larger size than its adjacent larger while the central region had no visible spherulite structure. Their formation, and the related thermomechanical history, were examined. Macro mechanical properties and local mechanical properties of micro molded samples and micro features were evaluated by tensile testing and nano-indenation. The relationship between process, morphology and properties were evaluated and correlated by statistical analysis.
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