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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Effect of part thickness on the potential to induce cold crystallinity in nylon 6,6 injection molded samples
Tensile bars of two different thicknesses were injection molded from Nylon 6,6 under controlled conditions and DMA results compared. Early analysis indicates that cold crystallization can be induced for improved mechanical properties on the 2mm thick samples, but not for the 4mm samples. This is due to the more prominent shear-induced orientation layers inherent in the thinner sample re-orienting during the annealing process. Results indicate there may be applications where the crystalline distribution through the thickness of a part may be critical to the plastic performance in cyclic or thermal load bearing applications.
Sustainable In-Machine Mold Cleaning and Part Deburring & Deflashing Using Dry Ice - Changing the Game Rules with CO2
For plastic processors there is a great demand to increase the productivity of their equipment and the quality of their parts, while maintaining healthy margins. This can be a balancing act between using the most effective technology while working within a shrinking budget. This paper discusses the advantages of dry ice blasting as a replacement for solvent and/or mechanical cleaning for the removal of contaminants from tooling as well as its use to deburr and deflash plastic parts. While the principles discussed herein are applicable to multiple plastics processes (BM, Ext., etc.), the focus of this paper will be on injection molding and the various steel and aluminum mold substrates commonly used. The reader will achieve a benchmark understanding of the role and relevance of dry ice in mold cleaning, part deburring & deflashing and its impact on product quality, production cost, production efficiencies, worker safety and health and environmental responsibility. Research from several industry case studies will be discussed. The results confirm that dry ice cleaning can remove contaminant layers from various common mold metals and is a good alternative to other commonly used manual, abrasive methods as well as successfully deburr and deflash plastic parts.
Bridging the Gap: Using Injection Molding Simulation to Determine Realistic Plastic Tolerances
Dimensions on plastic parts are affected by material shrinkage and can limit the dimensional stability of a final product. Incorporating injection molding simulation into the design and manufacturing process allows companies to better determine the dimensional changes that occur due to molding. Moldflow, an injection molding simulation program, was used to import CAD geometry and select processing conditions to predict part shrinkage. These shrinkage results were compared to measured molded parts to determine variations in dimensions. By understanding the correlation between processing conditions and molded part dimensions, manufacturers can control the sensitivity of the molding process and the ability to maintain products within specifications.
Influence of exfoliated carbon nanotubes on crystal structure and tensile properties of polypropylene
The objective of this work is to investigate the microstructural mechanisms responsible for the observed remarkable increase in modulus and strength of polypropylene (PP) containing only trace amounts of multi-walled carbon nanotubes (MWCNTs). The functionalized MWCNTs were individually dispersed in commercial polypropylene matrix by using our novel nanoplatelet-assisted dispersion approach, followed by compatibilization of MWCNT in a small amount of stabilizing surfactant. We also report on the morphology and dynamic mechanical properties, and propose a novel mechanism for reinforcement of thermoplastic materials with individual MWCNTs.
Study of Interfacial Interactions in Exfoliated Graphite Nanoplatelets/Polyamide 12 Nanocomposites
The interfacial nano-reinforcement -polymer interactions in polymer nanocomposites (PNCs) are key in fabrication of PNCs with engineered properties. Our study showed the presence of an immobilized layer or interphase around nano-reinforcements and investigated possible correlations between interfacial interactions and macro-scale properties of PNCs. Polyamide 12 (PA12) based PNCs reinforced with 0-15 wt% of exfoliated graphite nanoplatelets (xGnPs) were fabricated. The results indicated occurrence of attractive interactions at the interface of xGnP and polymer leading to formation of a stiff interphase a few tens of nanometers thick. The altered dynamics of the immobilized layer was suggested to develop a dominant secondary mechanism contributing to the macroscopic properties of the PNCs.
UV Monocoat: Ad Advanced Coating Technology for Consumer Electronics
Surface coatings on plastic substrates with excellent physical performance, low application cost, and minimum environmental impact are highly desirable for various commercial applications. Here we describe PPG’s ultraviolet (UV) monocoat technology for consumer electronics, which afforded both protection and decoration of plastic substrates with a single-layer colored coating system. Studies demonstrated that UV monocoat applied on plastic computer and cellphone parts successfully met or exceeded customers’ specifications, showing good adhesion to plastic substrates, excellent abrasion and scratch resistance, good chemical resistance, and high weathering stability. UV monocoat also enabled a variety of colors with a wide range of gloss for decoration of plastic substrates. In addition, UV monocoat uniquely combined a single-layer design with UV cure technology, which significantly increased on-line coating capacity and efficiency and dramatically reduced application cost and environmental impact.
ToolingEDGE - High Performance and Sustainable Production
The strong emergence of new" economical and industrial regions on the globe supported by lower hand labor costs puts European Engineering & Tooling face to new challenges that evidence the necessity to develop new and revolutionary ways of making things. It is in this context and to answer to the new global challenges it was created an industrial and scientific Cluster the Portuguese Engineering and Tooling Cluster (E&T). This cluster represents an industrial value chain with specialized skills and competences from Design and Engineering to Tooling and Plastic Products. The E&T cluster is responsible for setting up a national strategy for the development and sustainability of this important economic sector combining a strong investment in technological and organizational innovation that will support a constant and progressive evolution on technical and organizational efficiency. The E&T strategic plan within 10 years is to be recognized worldwide as one of the most advanced in technological point of view and having the capacity to offer added value in the design and production of molds special tools and precision machined parts produced by injection or in materials with specific features for new applications. The R&D project ToolingEDGE - High Performance and Sustainable Production is one example of research activities being held by E&T cluster. The project aims to deploy technological solutions to prepare the E&T sector for sustainable competitiveness and to enable the penetration in new and/or added value markets considered strategic for the E&T notably: the aeronautics medical devices electronics automotive and packaging industries."
In-situ Monitoring of a Gas-Liquid Reaction with NIR Spectroscopy
Fourier Transform Near Infrared (FT-NIR) spectroscopy may be used to analyze industrial processes in- situ. In this case study, FT-NIR data is presented which tracks the reactants and final products ensuing from a catalytic gas-liquid process used for the production of vinyl melamine monomers. This reaction presents an alternate pathway to the polymerization of melamine in lieu of its traditional reaction pathway using formaldehyde, a known carcinogen. The analysis shows changes in rates of reaction and end-product concentrations based on differing temperatures, catalyst concentration, and stirring speed.
The Assessment of Uncertainty in Spectrophotometry
Ideally, manufacturer specifications provide performance characteristics and specifications that can be used to evaluate the suitability of colorimeter and spectrometer measuring and test equipment for a given application. However, understanding specifications and using them to compare equipment from different manufacturers, the quality of products, and its adherence to specifications can be a perplexing task. This primarily results from inconsistent terminology, units, and methods used to develop and report equipment performance specifications. This paper discusses how to determine if manufacturer specifications are adequate for the intended purpose, and how to interpret and assess colorimeter and spectrometer performance and reliability. Recommended practices are presented and an illustrative example is given for combining components values into a specification.
Gas Chromatography Applications in Food Flexible Packaging Covering Food Safety, Process Control, Polymer Additive Analysis and Analysis of New Generation Packaging with a Compendium of Illustrations
Gas Chromatography (GC) is used extensively in Food Flexible Packaging for quick and accurate analysis of solvents retained from solvent based liquid printing inks, adhesives and coatings. This paper covers recent a recent development in Head Space technology, the Dynamic Head Space with Purge & Trap, which ensures complete extraction of high boiling points solvents such as ethyl cellosolve, propyl cellosolve, toluene and methyl iso butyl ketone in addition to low boiling point solvents such as ethyl alcohol, ethyl acetate and methyl ethyl ketone. Identifying all solvents in full measure is critical for food safety. The paper mentions the fast GC concept, with suitable spilt injection ratio, a special shorter length capillary column and Flame Ionization Detector (FID) with high sampling frequency and data acquisition capability which can help in quick analysis for control of speed, drying hood air flow and dryer temperature station wise in printing, lamination and coating. Analysis of the levels of slip and anti-block additives after production of the sealant layer film, after lamination, after curing and post storage needs to be measured for validation and standardization of processes and sourcing of raw materials.GC analysis is relatively fast and simple. Nano-technology is being increasingly used in food packaging for performance improvement. SiOx coating on Bi-axially Oriented Polyester (BOPET) Films improves barrier to levels matching aluminium foil and thereby facilitates see-through packaging. The paper describes a method for analysis of performance of such coatings. The aim of the paper is to help the food flexible packaging industry to fully exploit the capabilities of advanced Gas Chromatography to ensure food safety, optimize processes and enhance shelf performance.
Synthesis and Characterization of Antimicrobial Polyvinyl Pyrrolidone Hydrogel as Wound Dressing Hints
A novel antimicrobial hydrogel (PVP-GP) was prepared by covalently bonding polyvinyl pyrrolidone (PVP) with poly(hexamethylenediamine guanidine hydrochloride). The products were characterized by 1H NMR, FTIR, SEM, and their performances for wound dressing applications were also evaluated. Swelling study showed that the water absorptivity of PVP-GP hydrogels decreased as the crosslinking density increased either in water or in physiological saline solution. The water vapor transmission rates (WVTR) of PVP and PVP-GP hydrogels were in the range of 1727 ~ 2320 g/m2/day, indicating that the prepared hydrogels were suitable for wound dressings without dehydrating the wound surface or accumulating exudates. Kirby-Bauer inhibition zone tests and microbe penetration assay proved that the PVP-GP hydrogels had high antimicrobial activity.
Superior Processability and Economics of Single Site LLDPE vs. Conventional Metallocene LLDPE Blown Films
Over the past 15 years, the polyethylene industry has increasingly focused on metallocene and single-site catalyzed LLDPE as the route to higher performance. Unfortunately, the improvement in physical properties over conventional Ziegler-Natta (Z/N) LLPDE is counterbalanced by a dramatic decrease in output rates which directly impacts the economics of these film structures. To compensate, blown film producers add 10%-20% of LDPE into these resins to the detriment of the film physical properties. A unique class of single-site catalyzed LLDPEs (sLLDPE) has been developed which overcomes the processability issues encountered with the traditional metallocene LLDPE (mLLDPE) resins thus reducing the demand for LDPE and maintaining the enhanced physical property performance. This paper focuses on: The comparison of bubble stability and maximum output of sLLDPE vs. mLLDPE resins. The economic cost associated with mLLDPE vs. sLLDPE in a commercial film structure via a case study.
An Investigation of the Effects of Bound Selection on the Numerical Formulation of Kinetic Parameters
Kinetic modeling is used to predict the rate of conversion of a partially cured thermosetting plastic subjected to catalytic conditions of temperature and pressure. Parameters for these models can be determined from experimental data obtained through differential scanning calorimetry (DSC). In the present study, kinetic parameters are determined from dynamic DSC scans of the Pro-Set 117LV/229 resin system. The primary contribution of this paper is an evaluation of the sensitivity of empirical kinetic parameters to the selection of reaction bounds. This study is performed using a finite difference approach to obtain parameter sensitivity. The results suggest that the kinetic parameters are insensitive to bound selection for this particular resin system. Additionally, the kinetic parameters obtained from dynamic scans are applied to isothermal DSC results, which indicates the importance of the accurate determination of kinetic parameters at low degrees of conversion and the evaluation of diffusion control. The effects of gelation and vitrification are also considered.
Manufacturing Induced Curvature of Carbon Fiber Laminates: Experimental Observation and Model Validation
The use of carbon fiber reinforced composites is becoming increasingly implemented throughout the entire aerospace, automotive and many niche industries, in large part due to their high strength to weight ratios. Unfortunately, effective design of the fabrication process and the final part performance poses increased engineering difficulties over alternative manufacturing approaches. This work focuses on the residual strains that occur within the processed laminate as induced during manufacture. These residual strains are due to a combination of the curing kinetics of the thermoset and the induced thermal strains caused by a coefficient of thermal expansion mismatch for the resin and carbon fiber. In the present paper, we present results for a cross-ply (un-balanced) laminate. We use micromechanical theories to predict the stiffness and the coefficient of thermal expansion of an individual lamina from the constitutive properties for the fiber and the matrix, and couple the lamina results with a finite element structural and coupled thermal-structural analysis to predict the observed macroscopic deformation and curvature of an unloaded processed laminate. The finite element results are compared with the measured results and show exceptional qualitative agreement with experimental observations. Suggestions for improvements on the method are introduced along with a discussion of the need for the quantification of the relevant constitutive material properties for future modeling and experimental studies.
Prediction of Fiber Orientation Tensor in Glass Fiber Reinforced Polymer
Application of chopped glass fiber reinforced polymer components from injection and compression molding process are rapidly increasing in automotive industry due to the light-weight and their mechanical properties. Material properties of such components strongly depend on fiber orientation. Therefore it is very important to estimate the fiber orientation distribution in such materials. In this paper we are presenting a practical method to estimate the fiber orientation from CT scan image. A 3D image of fibers is created and 2nd order orientation tensors are calculated using the coordinates of the end of fibers. The approach is demonstrated on a 3-D box shaped structure. The measured orientation tensors are compared with the predicted values from the mold-fill simulation. Key challenges in measuring the orientation tensor for the long fibers is also discussed.
Insert Injection Molding Simulations for Lens Encapsulation of Liquid Crystal Displays
An insert injection-compression molding process was used to encapsulate cholesteric liquid crystal displays with flexible and rigid lens. For this purpose, a complex hot runner mold was designed and constructed. Thermoplastic polyurethanes (TPU) were found to be the best candidates for this application after a vigorous search on desired physical properties for lenses including transparency, low melt viscosity and melting temperature and mechanical properties. Three different hardness grades of TPUs were selected to demonstrate the range of encapsulation from soft to hard. In this process, the encapsulation was accomplished in two steps: first, injecting the TPU on the front of the display from an edge pin gate and subsequently the back side of the display is encapsulated. A flow simulation is completed on Autodesk Moldflow Insight to help pre-visualize the changing process parameters effect on part quality and to compare with experimental results. The quality of encapsulation and shrinkage related problems and their elimination are discussed in this study.
Using the Flexural Modulus to Evaluate the Accuracy of Existing Fiber Interaction Models for Predicting the Fiber Orientation in Injection Molded Thermoplastics
Advances in modeling the mold filling process have led to better designs and manufacturing efficiencies of short?fiber fiber reinforced thermoset plastics. The flow characteristics during processing dictate the spatial varying fiber orientation, and thus the spatially varying mechanical properties. Knowledge of the fiber orientation allows for part optimization of both the mold design and the processing parameters. The classical fiber?fiber interaction model Folgar?Tucker (1984) for calculating the fiber orientation for fiber filled thermoplastics has seen extensive use within the industry for nearly 30 years. Recent modifications of the classical model include the reduced strain closure (Wang et al., 2008) and the anisotropic rotary diffusion model (Phelps and Tucker, 2009). Each of these models yield quite different characteristics in the resulting predicted fiber orientation. In this paper we suggest that the predicted flexural modulus from these different fiber interaction models may be quite different and may be an effective macroscopic structural test to identify acceptable diffusion models and possibly to quantify the appropriate empirical parameter ranges for acceptable interaction models. In this work, the velocity gradients are computed along streamlines of a complex domain of an injection?molded ASTM flex bar. The fiber orientation is then obtained along each streamline from the velocity gradients and then from an in?house code the local stiffness tensor is obtained as a function of position within the entire part. Lastly, the nodal stiffness values are imported back into the finite element software to perform structural bending tests as a function of length along the part. The results show a structural response that is significantly different between the different fiber interaction models, and thus lends credence to the possibility that flex tests may be a useful experimental technique to compare fiber interaction models.
Poly(butylene succinate)/fumed silica nanocomposite: functionality and rheology
Plastics Engineering Department, University of Massachusetts Lowell Nanocomposites based on biodegradable poly(butylene succinate) (PBS) and silica fillers were prepared by a melt-blending process. Two types of unmodified fumed silica and octadecyltrichlorosilane (OTS) functionalized silica were used as fillers. Rheology was used to study relaxation dynamics and viscoelastic properties of these nanocomposites in the melt state. The effects of polymer-particle and particle-particle interactions on viscoelastic properties of nanocomposite materials were investigated. Linear viscoelastic data indicate a transition to a solid-like response at low oscillation frequencies for particle weight fractions as low as 5%. The long-time response upon a step shear strain demonstrates that liquid-like behavior persists in the nanocomposites below 5 wt% loading, which is related to the relaxation of the temporal polymer-particle network. Dynamic viscoelastic and dynamic mechanical thermal analysis (DMTA) measurements of the PBS/silica nanocomposite reveal that fumed silica with the smallest primary particle size has the largest dynamic moduli over the testing temperature range. The hydrophobic functionalization of silica filler does not appreciably change the thermal transition temperatures in the nanocomposites.
Flowability Software for Powder Produced By Raleigh Disturbances for SLS
Powders for additive manufacturing processes such as Selective Laser Sintering (SLS) are currently produced by costly cryogenic milling or precipitation processes for a limited selection of resins. A nowel technique allows production of pellets in the micrometer-scale by extruding a polymer melt through a capillary and perturbing it with a hot air stream which can be used for the SLS processes. Due to the fact that this micropelletization process is used to produce powder particles from different materials, the developed software is very helpful to predict the flowability of these different particle shapes and different materials and its usage for the SLS process. This software will determine the flowability characteristics of different grain shapes and will be evaluated by comparison of results provided by both, software and experimentation. In a second step, different micropelletized materials surface smoothnesses will be compared and evaluated towards their competitiveness. This validation will show a comparison of quality and performance between the different powder production processes. The goal of this work is, to produce more cost effective but competitive powders out of different micropelletized materials.
Process Parameters Effects on Microstructure and Properties of Porous PP/TiO2 Nanocomposite Films
Nanocomposites porous film based on polypropylene (PP) and titanium dioxide (TiO2) nanoparticles were prepared by the uniaxial stretching method. Effects of drawing temperature, extension rate, stretching ratio and composition of the base films on final properties and microstructure of the stretched films were studied. Water vapor permeability results showed significant decrease in permeability of the films stretched at temperatures higher than 60°C. Water vapor permeation in the porous nanocomposite films had a direct relation with nanoparticle content, extension rate and stretching ratio. Study on morphology of stretched films, using SEM, revealed that the pores form due to PP/TiO2 interfacial debonding at lower stretching ratio while higher stretching ratios cause an enlargement of the pores and formation of PP fibril structure parallel to the stretching axis. Apparent porosity values, BET surface area measurement and quantification of dye absorption on pores showed smaller dependency on process parameters.
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