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.
Plastics injection molding machines require an extensive amount of energy, and energy costs typically represent one of the major line items in a company’s operating budget. A typical injection molding operation spends almost as much on energy expenditures as it does on direct labor. As operators look to reduce costs and enhance sustainability, they typically turn to the more obvious levers – such as new equipment, lighting retrofits, and more. But, one of the easiest and most frequently overlooked opportunities to improve energy efficiency is lubrication. This paper outlines how lubrication influences energy efficiency, key lubrication-related energy saving opportunities, and how operators can implement the right lubrication strategy to reduce energy costs, improve their bottom line, and enhance sustainability.
Environmental stress cracking (ESC) is a common failure mechanism in a variety of polymeric materials. Despite this, the relationship between ESC agent concentration, applied stress, temperature, and polymer composition has not been thoroughly established for many commodity plastics. In this study, three common thermoplastic polymers (PC, ABS, and PMMA) were exposed to an environmental stress agent under different conditions (variable strain, temperature, or concentration). A process for acquiring critical strain curves for materials under these conditions is presented, providing a methodology for systematically assessing factors governing ESC failure of polymers. Additionally, fractographic and chemical analysis of polymer samples exposed to an environmental stress agent are reported.
In injection molding of thermally sensitive materials, the reduction of thermal stress often contradicts with the flow properties. Especially when processing small melt volumes, as often occurs in micro injection molding, long residence times lower the range of applicable materials. New processing strategies need to be developed to reduce the thermal load or improve flow behavior to open up new applications in medical technology. In this paper, the processing of blowing agent loaded bioplastics is investigated focusing on flow behavior in thin walled parts. In this feasibility study, a micro injection molding machine is modified to process plastics in a pressurized gas atmosphere in order to analyze flow behavior using a flow spiral and varying processing parameters.
Colour is essential to human experience. From pre-history, through ancient civilization into the modern era, cultures have strived to create colour in the objects around them. Early peoples exploited natural resources to create images from their surroundings, such as red earth, black soot and white chalk. With time people developed more sophisticated techniques to refine minerals to generate a wider palette with blue, green, bright red and yellow. Often toxic in nature, these early inorganic pigments formed the skeleton of the pigment manufacturing industry. With the discovery of coal tar in the 1800s, and the ensuing rapid industrialization of synthetic chemistry, an explosion of colour transpired, leading to the modern chemical industry. The historic generation of plastics followed a parallel path, beginning with use of natural materials such as ivory and tortoiseshell. Progression to processing of natural materials such as rubber, cellulose and shellac to generate more functional plastics, evolved to a place where coal tar chemistry provided a natural next step. This culminated in the discovery of Bakelite, the first fully synthetic plastic in 1907, which ignited the imagination for plastic materials, and the widespread production of consumer and industrial items accelerated. Colour and plastic developments went hand in hand, as by the 1950s the desire for brightly coloured, functional items sky-rocketed. Pigment chemistries were re-imagined with this new era in mind and from this point colour effects were generated specifically for plastic functionality. Textile fibers, automotive parts, plastic bottles, packaging and film; all un-thinkable now, without the effect of colour.
The aim of this work was to compare the effects of compatibilisation with a pre-fabricated additive and the in-situ generation of a similar additive in the melt for LDPE-PA6-blends and to investigate the effect of mixing protocol (i.e. compounding vs. dry-blending) of the prefabricated additive on the resulting properties of reprocessed LDPE-PA6 films. We found, that it is possible to compatibilize LDPEPA6-blends via the addition of maleic anhydride based compatibilizers, regardless of fabrication approach. This effect can be seen from the morphology of the samples as well as from mechanical properties. Also, the reprocessing of films from LDPE and PA6 with reasonable properties is possible when adding a compatibilizer. The best, i.e. the most balanced properties can be found when the compatibilizer is melt compounded, as this gives the best distribution. These results show that it is possible to reuse multilayer materials when considering the blend components and properly selecting a compatibilizer.
In order to increase added value of plastics in terms improved circular economy, an increased use of recycled polymers becomes more and more important, also for the plastic pipes industry. Unfortunately, compared to specially designed virgin pipe grades, recycled polymers show deteriorated long-term properties. The current paper investigates the influence of different polyolefin cross-contaminations on the slow crack growth (SCG) resistance of a polyethylene (PE) pipe grade. The investigation was conducted with the CRB test on blends of a virgin PE100 with different contents of polypropylene homopolymer (PP-H), blow molding PE-HD, and a recycled first generation PE-HD. The results demonstrate that 5% of cross-contamination content already results in a significant reduction of SCG resistance and that the highest reduction is caused by blending with PP-H.
Coatings on plastics is a very dynamic space driven both by the desire for more environmentally friendly coatings and by an ever increasing demand for improved performance and additional functionality. This presentation will discuss the reduction of the carbon footprint by use of waterborne coatings and UV coatings. In addition the importance of UV coatings to improve scratch and mar resistance, improve energy efficiencies and increase throughput will be discussed. Options for dual cure allowing for upgrade of conventional lines and coating formulations to meet customer needs will be covered. New innovations and future directions base on customer needs and expectations will be reviewed as well. The use of bright colors using Nano pigments and dyes, self-healing paint, easy to clean coatings for high gloss interiors, anti-glare coatings and UV reflective coatings to control interior temperature will be introduced.
Metal Injection Molding (MIM) is a manufacturing method combining injection molding with powder metallurgy. Since MIM involves numerous process characteristics, unstable product quality is a common problem. Defects such as warpage usually appear after debinding caused by the residual stress and non-uniform concentration during the injection molding process. MIM is a series of processes for producing small, complex, and precise metal parts. The metal product is processed through injection molding, de-binding, and sintering. The debinding process of MIM requires the longest time of these processes. If the volume of the product is large, de-binding time can double. This study used gas-assisted injection molding (GAIM) to form a hollow product. Several conventional MIM parameters and GAIM parameters were investigated. The purpose of the study was to reduce the de-binding process time by combining GAIM and MIM. The results show that using gas-assisted injection molding in metal injection molding can reduce the defects from powderbinder separation, and reduce the shrinkage of green parts. Because the product’s structure is hollow, the shrinkage from sintering may also be reduced. The de-binding time can be greatly reduced.
The global demand for epoxy is increasing at a fast pace, with projections of the industry having a worth of $11.5 billion by the year 2022. However, amidst growing concerns about eco-sustainability, the use of toxic and environmentally hazards chemicals in conventional epoxies has triggered efforts among researchers on developing epoxies from various bio-sources. Yet, such efforts have not been accompanied by a thorough analysis of the environmental performance of such bio-based epoxies vis-à-vis their conventionally derived counterparts. This work aims at understanding the environmental performance of two different bio-based epoxies and compare with petroleum derived epoxy. It also highlights the impact of petroleum-based epoxies on human health and human carcinogen toxic categories. Lignin based epoxy performed poor on all the impact categories mainly due to use of excessive amount of chemicals during molecular breakdown of lignin to Vanillin.
This study investigated the mechanical behaviors of injection molded polylactic acid (PLA) composites reinforced with carbon fiber (CF) at different fiber loading levels (5 wt%, 10 wt%, 15 wt% & 20 wt%). PLA, a biodegradable thermoplastic derived from renewable resources, has been replacing petroleum-based plastics in many applications due to its sustainability and low environmental impact. However, the low mechanical strength limits its wide structural applications. The addition of small amount of CF significantly increased the tensile strength and modulus while leading to reduced ductility. Compared to pure PLA, the composites with 5 wt% CF content had a 40% increase of tensile modulus and a 63% decrease of elongation-at-break. The effects of water absorption on the mechanical properties of PLA/CF composites were also studied.
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.
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