SPE Library
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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Recycling
Various topics related to sustainability in plastics, including bio-related, environmental issues, green, recycling, renewal, re-use and sustainability.
Preliminary Study On Impact Evaluation Of Rpet Samples Using Reactive And Non-Reactive Modifiers
The demand for recycled plastics in food contact packaging by consumers, brand owners, and regulatory agencies has put pressure on suppliers and converters to increase post-consumer content. Recycled polyethylene terephthalate (RPET) has been widely adopted for use retail environments for refrigerated and ambient products. This increased demand for post-consumer recycled (PCR) content in food packaging is fundamental to meeting environmental sustainability objectives and thus must be available for application in all cold chain markets. However, reduced impact performance due to increasing PCR content and feedstock variation has limited broader market adoption in low temperature and frozen products. The purpose of this study was to evaluate the potential of reactive and non-reactive impact modifiers to increase the impact performance of PCR and RPET in commercially manufactured cake trays. Results of this study found the optimum loading ratio and performance in RPET was realized using a reactive modifier at 15% for an increase of 51-118% in impact performance. This study will help provide solutions for users of RPET looking to increase performance in refrigerated and frozen products.
Processing Of Poly(Lactic Acid) Blown Films With Food Grade Chain Extenders For Packaging Applications
Poly(lactic acid) or PLA films are brittle and difficult to manufacture due to PLA’s insufficient melt strength, which are overcome by chain branching with melt strength enhancers (MSEs). Thus, the effectiveness and efficiency of two newly developed and FDA-approved food grades MSEs with different epoxy equivalent weights (low and high) in chain extending PLA were studied first using a torque rheometer. Both multifunctional epoxies chain-extended PLA effectively since they significantly increased the torque during mixing. However, the MSE with lower epoxy equivalent weight was more efficient in chain branching PLA due to its higher reactivity. Secondly, the feasibility of utilizing this most efficient MSE in extrusion-blown PLA film processing was assessed. Chain extension reactions also occurred during film production as confirmed by its increased molecular weight. However, film manufacture was only feasible for blends with up to 0.5% MSE, becoming unprocessable above this content due to the increased viscosity. Chain branching of PLA film was found beneficial in overcoming its brittleness since its impact strength increased almost linearly with the chain extender content. These sustainable ductile films have tremendous potential for food packaging applications.
Recycled Cellulose Polypropylene Composite Feedstocks For Polymer Additive Manufacturing
With the rapidly expanding polymer additive manufacturing space, re-use and recycling of thermoplastics should be considered. Recent research has shown the recycling of some commercial grade filaments such as acrylonitrile-butadiene-styrene (ABS) and polylactic acid (PLA) is feasible. In addition, consumer-grade thermoplastics used in packaging can be considered a low-cost and sustainable feedstock for material extrusion additive manufacturing processes, providing a high-value output for waste plastics. Green composite filaments made by incorporating recycled cellulose and rubber-based materials can lead to 3-D printed parts with improved stiffness, toughness and/or reduced distortion. Plastic recycling is currently limited due to the low value of recycled content and high transportation and collection costs. But distributed manufacturing via additive manufacturing, in which 3-D printing filament is generated from local plastic waste, represents an economically viable solution to plastic recycling. This paper presents work in the reinforcement of recycled polypropylene using cellulose waste materials to generate a green composite feedstock for extrusion-based polymer additive manufacturing. Dynamic mechanical analysis showed a ca. 20-30% increase in storage modulus with the addition of cellulose materials. Tensile results show that elastic modulus increased 38 % in virgin polypropylene with the incorporation of 10% cellulose.
Recycling Of Polyethylene Grocery Bags Into High-Strength Fibers And Yarns Without Using Melt Processing
A critical issue facing man kind is how to effectively recycle plastic grocery bags. Currently, the most proven practice for bag recycling is to create numerous returning sites throughout the nation. However, the success is compromised by the voluntary nature of such activities. In this work, we investigate an alternative approach to bag returning, by diverting recycling activities directly to consumers or end users at home. Specifically, a simple process for converting waste bags into high-strength fibers and yarns is designed and tested in a feasibility study. The results demonstrate that by twisting and hot drawing, high-strength polymer yarns with mechanical properties at least comparable to those of commodity polymer fibers can be created. This may open up a new paradigm in plastic bags recycling and allow part of the recycling burden to be shifted to local residential communities.
Resistance Heating Of Carbon Fiber Reinforced Thermoplastics – Influences On Heating Rate And Temperature Distribution
Continuous fiber reinforced thermoplastics (CFRTP) experience increasing demand by industry. Compared to their thermoset counterpart, they are considered to allow for shorter production cycles and offer more and better joining and recycling solutions. Usually, continuous fiber reinforced semi-finished parts are produced and then prepared for a back injection molding process to add functional integration. The resistance or joule heating process utilizes the electrical conductivity and accompanying heat dissipation of embedded carbon fibers. Thus, a short and homogenous heating process can be achieved. The main challenges that arise with resistance heating are the optimization of the electrical contact pieces as well as the shape and build of the semi-finished part. The heating process of several variations of contact pieces and shapes are monitored using thermal imaging. An algorithm is developed to automatically analyze key aspects of the heating process allowing for easy comparison of different parameter sets. Key results show that rounded edges for copper contact pieces and high contact forces yield homogenous temperature distributions and prevent hot spots while higher voltages result in less homogenous temperature distributions but higher heating rates.
Rheological Method Development: Using Rheological Tools To Predict Thermoformability
Extrusion thermoforming of very large parts such as those used in the appliance industry can exceed the melt strength limits of a given polymer. This study was undertaken to define new rheological tests capable of defining the molecular design required to avoid excessive sag in the heating step of the thermoforming process and to identify the optimum temperature for forming. Damping factor (tan = G’’/G’), also known as “tan delta”, can be used as a tool to identify fabrication conditions, molding window size, and the effect of added recycle streams. In addition, we compare polymer families that challenge our ability to thermoform large parts. Semi-crystalline materials must be run at or above their melting point temperature (Tm). Tm is well above the glass transition temperature (Tg) and the temperature delta (Tm - Tg) may exceed the width of any rubber plateau region in the melt state. These rheological characteristics are related back to the entanglement density of a given polymer and compared to the width of the rubber plateau.
Statistical Modeling Of The Squeak Noise Occurrence Of Natural Rubber
In this study, the occurrence of the squeak noise according to various material / environmental factors of natural rubber was found through friction test using custom built friction tester. Material factors such as rubber hardness, surface roughness and additive content, and environmental factors such as heat aging, temperature, surface moisture, friction speed and frictional load are considered. And the hypothesis test was conducted to determine whether there was a significant correlation between each factor and the occurrence of squeak noise. Afterwards, logistic regression analysis and neural network analysis, which considers the interactions among these factors, were performed using the statistically significant factors in the occurrence of squeak noise obtained by the hypothesis test, and a probability model of the occurrence of the squeak noise was developed. And we compared the occurrence of the squeak noise predicted by the two models with the actual occurrence of the squeak noise, and the result shows 88.15% and 87.16% of accuracy, respectively. We also verify the accuracy of two models by using receiver operating characteristic curve (ROC curve), which illustrates the diagnostic ability of a model.
Study On Thermal Characteristics And Mechanical Properties Of Poly(Lactic Acid)/Paraffin Wax Blends
Poly(lactic acid) (PLA) plastics have been popularly applied on many bio-degradable products and claimed as a green polymer materials for environmental concerns. In this study, a poly(lactic acid) (PLA)/paraffin wax (PW) composites with blends containing different amounts of PW and different compounding times have been developed and investigated. These composites blends were prepared by a micro-compounder with twin screw. Then, a neat PLA and the PLA/PW composites have been used to fabricate tensile specimens by micro injection molding machine. Effects caused by different compounding time and PLA/PW ratios, the thermal behavior and mechanical properties have been tested and investigated. Moreover, distribution and dispersion of PW in the PLA matrix have been observed in optical microscope and then calculated for comparison. Experimental results showed that the addition of PW yields significant improvements in ductility and toughness compared to that of neat PLA. The crystallinity and complex viscosity have also been improved. Finally, the samples of PLA/PW made by longer compounding time exhibits better distribution. Results of this study can be used for developing PLA/PW composites for bio-prosthesis for implants applications. Keywords: poly(lactic acid); paraffin wax; compounding time; injection molding;
The Effect Of Hygrothermal Exposure On The Thermal Conductivity Of Nanocellulose Based Foams
Environmentally friendly insulation and packaging materials, driven by consumers and growing stringent global regulations against plastics, make biobased alternative materials a competitive market. Cellulose-based foams, consisting mainly of cellulose, are a greener replacement option over traditional petroleumbased insulation materials. One of the challenges associated with cellulose-based foams is their susceptibility to moisture, especially at elevated temperatures. Composite foams of nanocrystalline cellulose (NCC) and polyvinyl alcohol (PVA) were fabricated using a freeze casting method with a wide range of cooling rates during freezing. The physical properties of the foams, i.e., density, porosity and thermal conductivity were then evaluated before and after hygrothermal exposure at 40 °C with a relative humidity range from 96 to 77%. The results showed that the foams prepared with the highest rate of freezing exhibited the lowest relative density (0.019 g/cm3) and the lowest thermal conductivity (20 mW/mK). In general, the foams’ thermal conductivity increased after hygrothermal exposure. However, the foams with the highest freezing rate exhibited recoverable thermal conductivity behavior after exposure to heat and moisture. The possible mechanism for the differences were also discussed.
Why Titanates And Zirconates Are Better Than Silanes
Added to the hopper just like a color concentrate, 2 to 3 parts of a phosphato titanate or zirconate in pellet masterbatch form per 1,000 parts of filled or unfilled compound provides a method (Function 1-Coupling) for in-situ interfacial nano-surface modification of most all inorganic and organic materials in a compound independent of the interface’s hydroxyl content and absent the need for water to effect hydrolysis for coupling as with silanes while providing metallocene-like repolymerization catalysis (Function 2-Catalysis) and (Function 3) nano-intumescence for flame retardance resulting in: the use of larger amounts of regrind and recycle; copolymerization of blends of dissimilar addition and condensation polymers such as HDPE, PP and PET; prevention of delamination of PP/HDPE blends; faster production cycles at lower temperatures producing thermoplastic parts having less heat stress differentials, better finish, and increased stressstrain strength; and control of burn rate and burn rate exponent. Compounds having subject additives age better due to the removal of water at the polymer-reinforcement interface normally left when using a silane or no additives that cause loss of adhesion during water boil tests.
Open Cell Foams - An Emerging, Low-Cost Bacteria Adhesive Surface for Energy And Environmental Applications
Bacteria adhesive surfaces (BAS) have diverse applications, such as water treatment, biofuels, and solvents production. However, currently their large-scale usage is hindered by high materials cost. Inexpensive open-cell foams can potentially serve as substrates for low-cost BAS, enabling their wider usage. This work demonstrates a passive approach for attachment of Escherichia coli or E. coli to a polyester polyurethane open-cell foam surface using pH of the wastewater. The foam’s ionic-responsive charge property was used to bind negatively charged bacteria to its pore surface at different pH conditions. At the best pH condition, the foam adsorbed E. coli with over 99% efficiency. The pH-driven bacteria adhesion to foam surface is simple, effective, and passive, therefore has potential for industrial-scale applications.
SPE Sustainability 2018 4th Quarter Newsletter
Read the 2018 4th Quarter issue of the SPE Sustainability Division newsletter.
SPE Sustainability 3rd Quarter 2018 Newsletter
Read the 3rd Quarter 2018 issue of the SPE Sustainability Division newsletter.
SPE Sustainability 2nd Quarter Newsletter
Read the latest issue of the SPE Sustainability Division newsletter.
ReFocus 2018 - Recycled Carbon Fiber Thermoplastic Compounds(2).pptx
This paper will discuss the use of recycled carbon fiber as a reinforcing filler in thermoplastic compounds, and how this material adds value to both prime and recycled plastic resins. Background,Validating, Prime vs. Recycled Carbon Fibers, Improvements to Recycled Resins, Improvements to Prime Resins, Applications
3D Printing Feedstock From Recycled Materials
United States Army warfighters in theater are often faced with the challenge of broken, damaged, or missing parts necessary to maintain the safety and productivity required. Waste plastics can be utilized to improve the self-reliance of warfighters on forward operating bases by cutting costs and decreasing the demand for the frequent resupplying of parts by the supply chain. In addition, the use of waste materials in additive manufacturing in the private sector would reduce cost and increase sustainability, providing a high-value output for used plastics. Experimentation is conducted to turn waste plastics into filament that can be used in fused deposition modeling. The effect of extrusion temperature and number of extrusion cycles on polymer viscosity and crystallinity are explored. The effect of blends and fillers to impart additional functionality are also examined. Tensile specimens were tested and compared to die-cut and injection molded parts. Parts printed from recycled polyethylene terephthalate had the highest tensile strength of all recycled plastics evaluated (35.1 ± 8 MPa), and were comparable to parts printed from commercial polycarbonate-ABS filament. Elongation to failure of all recycled plastics was similar to their injection molded counterpart. In addition, select military parts were printed with recycled filament and compared to original parts. This research demonstrates some of the first work on the feasibility of using recycled plastic in additive manufacturing.
A Characterization Of Soy Additives In Biobased Polyethylene Films
Four different soy additives were compounded into Linear Low Density Polyethylene (LLDPE). The four different additives were compounded and pelletized by FKuR. After a film was produced for each of the four batches, the mechanical, barrier, and thermal properties of each batch was characterized and compared to a control sample. The use of soy in polymeric films improved mechanical properties in LLDPE, reduced the cost and amount of plastic used, and improved water vapor barrier of the polymer. The modulus of each film increased with the use of filler. However, the ultimate extension and ultimate tensile strength decreased in the samples containing soy fillers. The films showed increased crystallinity in samples containing soy fillers. Additionally, thermal analysis indicated large amounts of weight loss in the soy loaded films when heated.
Accelerated Aging Of Medical-Grade Resins: Q10 Factors And Material Aging Models
Accelerated aging is used throughout the Medical Device sector and other sectors to evaluate materials and devices in an accelerated fashion. If used properly, it can shave years off of validation efforts. If used improperly, it can generate misleading or completely incorrect data about the resins and products in question. This paper explores the fundamental principles and provides supporting data. It is critical to understand the four primary modes of aging for polymers: (1) physical aging (embrittlement and loss of free volume); (2) chemical aging, which includes oxidation, chemical damage, sterilization, etc.; (3) sustained strain cracking, creep rupture, and environmental stress cracking; and (4) fatigue. For sustained strain or sustained load environments, stress relaxation and creep are also key factors. A case study is presented for polycarbonate and copolyester resins that are undergoing physical aging, sustained strain cracking, and environmental stress cracking (ESC), and a model presented to account for the various factors.
Developing Ultrasonic Processing Of Cnt Nanopaper/Solventless Epoxy Prepreg
In this work, we propose an environmentally friendly innovative ultrasonic process to impregnate solventless epoxy into carbon nanotube (CNT) nanopaper (NP) (approximately 50 um thick) for fabricating prepreg nanocomposites. Both multi-wall carbon nanotube (MWNT) NP and single-wall carbon nanotube (SWNT) NP are used for prepreg fabrication. The prepregs show multi-functional performance in EMI shielding and sand erosion resistance. Process parameters including ultrasound time, amplitude level and pressure are studied for the fabrication process.
Automotive Lightweighting With Reduced Density Polyamide Blends
Schulamid RD “reduced density” nylon is obtained through an immiscible polymer blend which requires the optimization of the compatabilization system, component viscosities, and, most of all, design of the compounding process. In addition to low density, low moisture absorption is achieved which provides part designers with more predictable physical properties and part dimensions when their application is exposed to real environmental conditions. For processors, lower moisture absorption means less moisture to remove. Cost savings can be realized by the reduced melt temperatures that can be used due to the improved flow characteristics of Schulamid RD. Less heat added means less heat to remove which reduces energy consumption for the entire process. A tailored heat stabilization technology has allowed use in under the hood applications like active grille shutters, fan shrouds, and other components requiring temperatures up to 150C.
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