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Extruded polypropylene foams provide a balance of high strength to weight ratio as well as thermal and sound insulation relative to solid materials. In addition, PP foams offer sustainability advantages over thermoset foams, because PP foams are readily reextruded and recycled. Used alone or as components of multi-component structures, extruded PP foams can provide mechanical properties that are valuable in a wide variety of packaging, construction, and transportation applications. Recently, Braskem commercialized a new high melt strength polypropylene (HMS-PP,) with the tradename Amppleo.® This HMS-PP grade enables efficient processing of PP foams using extrusion processesi. Using PP foam in a specific application requires an understanding of the mechanical properties, which depend on density, cell size, and cell morphology. This report provides mechanical properties for a series of Amppleo® 1025MA foams, spanning a wide range of densities and cell morphologies.
The pressure for increased fuel economy and low CO2 emissions for automotive vehicles continues. In order to satisfy requirements, lighter vehicles will need to be manufactured making it necessary to replace metals in structural components with lightweight materials such as carbon fiber composites. The challenge associated with implementation of carbon fiber composites is to make them cost effective for high volume production because historically this class of materials was designed for low volume production scenarios. In order to apply carbon fiber prepreg derivatives to high volume automotive applications, the material must be designed so it can be robotically handled, and reduce expensive material usage inefficiencies while utilizing existing processing equipment. This work presents an innovative mechanical method to incorporate uncured carbon fiber reinforced polymer “in-process” scrap to completely utilize the waste material in three-dimensional reinforcing rib features of a structural automotive application, and demonstrates an efficient material use method to provide cost savings with aligned carbon fiber prepreg designs. This paper compares the mechanical properties of the discontinuous fiber reinforced composites prepared using virgin carbon fibers and reutilized carbon fiber prepreg scrap.
A unique combination of reactors, a multi-zone circulating reactor (MZCR) in cascade with a fluidized bed reactor (FBR), and proprietary catalyst used to polymerize multimodal HDPE has enabled the pilot-scale production of Ziegler-Natta (ZN) HDPE blow molding resins having processability similar to chromium (Cr) HDPE resins while maintaining the high environmental stress crack resistance (ESCR) of a ZN HDPE resin. Additionally, these pilotscale multi-modal ZN HDPE blow molding resins feature significantly lower gel levels, giving improved surface finish of blow molded articles. This unique combination of reactors is the basis of LyondellBasell’s new, proprietary Hyperzone PE technology. Resins were produced at the pilot-plant scale for both general-purpose small-container blow molding (SBM) and typical largepart blow molding (LBM) applications, such as intermediate bulk containers (IBC) and drums. This paper focuses on the pilot plant-produced SBM HDPE resin and vits properties.
New technological advances in the processing of woody biomass have established a new class of nano-structured biomaterials with properties ideally suited to reinforce thermoplastic. These materials, known generally as ‘nanocellulose’ materials, are renewable, biodegradable, and have exceptional properties that enable them to compete in applications traditionally reserved for high-performance synthetic nano-fibers. In the research discussed here, some preliminary results establishing the effect of nanocellulose on the strength and stiffness of polypropylene and polyamide are presented, along with a comparison with natural fibres and commercial reinforcing agents for automotive applications.
Under the aspect of sustainability and the use of alternative materials, engineering thermoplastics such as polybutylene terephthalate (PBT) will be reinforced with renewable raw materials such as regenerated cellulose fibers. The University of Kassel is developing cellulose regenerated fiber reinforced technical thermoplastics in a state-funded project with further companies. Since pure natural fibers cannot withstand the high operating temperature of engineering thermoplastics (Ts>230°C), regenerated cellulose fibers are used. These fibers consist of over 99% renewable raw materials. In addition to the ecological aspect, regenerated cellulose fibers are distinguished from conventional fillers such as glass fibers by their lower density and higher impact properties. Since the engineering plastics PBT are increasingly used in the electronics and automotive sectors due to their high heat resistance and excellent insulating properties, a suitable flame retardant concept is essential. The Department of Polymer Engineering at the University of Kassel has tested various halogen-free flame retardant additives in cellulose and glass fiber reinforced PBT. Flame retardant additives based on phosphorus and nitrogen from Chemische Fabrik Budenheim and Clariant were used. The material starts foaming due to the synergy effect of the two flame retardant additives during ignition. Foaming prevents the material from dripping off and generating flue gas during flame treatment.
Exactly defined and constant granulates become more and more important in recycling business. The material is very often mixed with virgin granulate, sold on the world trade market and manufactures must handle different material streams without process changes. For solving that issue, a new regulation model for pelletizing systems, based on specific data analyses, was developed. In comparison to standard regulation models, available on the market, the developed model was generated by using symbolic regression based on genetic programming and focuses on the combination of actual process parameters. The model was generated and tested with a broad range of in-house, post-industrial and post-consumer materials. It turned out that the new model enables a constant granulate size without remarkable changes during the production process and leads to a substantial equalization of the produced granulate size.
Non-isothermal crystallization kinetics of novel nano-structured bio-based poly(ε-caprolactone) (PCL)/tung oil blends prepared via in-situ compatibilization and cationic polymerization was investigated at different cooling rates for different blend compositions using differential scanning calorimetry (DSC). The non-isothermal crystallization kinetics of PCL in the blends was strongly influenced by the tung oil thermoset, i.e.; the kinetics of non-isothermal crystallization process was greatly inhibited in the blends with compositions of PCL<50 wt%. This ﬁnding suggested that the high concentration of thermoset, tung oil could signiﬁcantly restrict the dynamics of the PCL chain segments, thereby slow down the non-isothermal crystallization process. On the other hand, a considerable acceleration in the non-isothermal crystallization kinetics was observed for PCL/tung oil 50/50 wt% blend. The crystallization kinetics was analyzed as a function of composition at different cooling rates based on modified Avrami approach.
Poly(butylene terephthalate) (PBT) and its composites are widely used in a variety of applications including electronic housing and automotive parts. However, the low notched impact strength limits its utilization in toughness requires application. In this study, fabrication and characterization of a biobased sustainable polymeric blends of poly(lactic acid) (PLA) and PBT were carried out. The blends properties were further improved with reactive epoxidized styrene-acrylic copolymer chain extender to reduce the PLA degradation, and ethylene-n-butyl-acrylate-co-glycidyl methacrylate (EBA-GMA) to improve the notched impact strength of the blends. In comparison to pure PBT, significant enhancement in the notched impact strength (> 250%) was observed after incorporate of appropriate amount of chain extender and EBA-GMA. The scanning electron microscopy (SEM) confirmed the uniform rubber phase distribution and rough impact fractured surfaces. The superior toughness can be corresponding to the strong interfacial interaction between blend phases. The properties of the obtained blends are very suitable to be used to fabricate sustainable biocomposites for future applications where the high biobased and low impact toughness issues need to be addressed.
Efforts are reported herein to develop new generation flame retardants based on ionic liquids. It is believed that they can replace and expand the applications of traditional flame retardants with high “green chemistry” qualities, superior performance and enhanced properties. High clear flame retarding PMMA, UL V0@ 0.4mm with its transparency intact, was developed, which is the world’s first and only case. High clear flame retarding PC, UL V0 @0.4mm with its transparency intact, was also developed, while it is difficult to develop high clear thin (less than 1.6mm) flame retarding PC plastic products using traditional flame retardants. Finally, we’ve also developed highly effective flame retardant for TPU, which can afford TPU at only 3% or 4%, almost one tenth of traditional flame retardant loading level. These novel flame retardants based on ionic liquids show great potential in many applications.
Selective laser sintering (SLS) produces three dimensional shapes by repeatedly sintering and resurfacing a powder bed in a layer-by-layer fashion. Our short-term goal is to better understand the processing changes of a polyamide-11 powder laser sintered printing process when silica nanoparticles are added. Ultimately, we want to evaluate whether such nanocomposites results in superior z-axis strength and an overall increase in fracture resistance. Although polyamide-12 (PA-12) is more commonly used in SLS printed parts, polyamide-11 (PA-11) has the advantage of being a bio-based polymer. Like PA-12, PA-11 is a semicrystalline polymer but has a higher melting point (201 ⁰C powder / 191 ⁰C part). Rheology and solution viscometry tests confirm a molecular weight increase during printing, through a post-polymerization process. SLS printed PA-11 tensile specimens exhibit a 1.8 GPa modulus, an ultimate tensile strength of 55 MPa, and a strain to break of 66 %. Although it is not stiffer nor stronger than PA-12, PA-11 is significantly more ductile. The goal of the present study is to determine the effect of colloidal silica nanoparticle content (0 – 4 wt%) on processing behavior and mechanical properties.
This study focused on the performance of blends containing poly(trimethylene terephthalate) (PTT) with biobased elastomer through processing and injection molding techniques. An epoxidized natural rubber (ENR) was trialed for its impact enhancement at 40 wt.%, as well as maleated polybutadiene rubber (MR) for compatibilization. To determine the blend systems compatibility, rheometry, contact angle and scanning electron microscopy (SEM) were utilized. ENR was found to be more partially miscible in the PTT blend system from interfacial tension and work of adhesion results that were supported by increased shear viscosity and shear thinning behavior. Viscosity ratios were modeled for the thermoplastic-elastomer morphology which matched with SEM images, demonstrating that the elastomer is dispersed within the PTT. The compatibilizer decreased the size of the rubber phase as seen in SEM. MR provided increased crosslinking and noticeable alteration in the FTIR peaks, representative of chemical interactions between the PTT and maleic anhydride. This augmented the impact strength by more than 4 times that of the neat PTT and provided a greater modulus of toughness and elongation at yield. 
This research work is focused on the melt extrusion of poly (3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) with poly (butylene adipate-co-terephtalate) (PBAT) and nanoclay followed by preparing polymer nanocomposite sheets using compression moulding. The effect of nanoclay on various properties such as water barrier, tensile strength, differential scanning calorimetry (DSC) and rheology was investigated. The results conclude the addition of nanoclay in PHBV/PBAT blend matrix improved the water barrier and tensile strength up to ~12% and ~20% respectively. The differential scanning calorimetry (DSC) analysis shows a slight improvement in melting and crystallization temperatures of PHBV/PBAT blend matrix by adding nanoclay. The melt rheology has confirmed a good dispersion of nanoparticles in PHBV/PBAT blend matrix. Hence, such a polymer bionanocomposites may be one of the potential candidate for packaging applications. The developed biocomposites from biodegradable plastics show promise in sustainable packaging applications.
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.
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.
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.
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.
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.
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.
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.
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;
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