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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Energy Saving Strategies For Plastics Injection Molding: Lubrication
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.
Effect Of Peroxide Loadings On The Rheological Behavior Of Pla Ternary Blends
With increasing interest towards biobased and/or biodegradable polymers that generate high performance composites, instead of petroleum based products, creates new opportunities and research challenges. Polylactide (PLA) is supposed to be one of the most promising biodegradable polyesters because of its high mechanical strength, high modulus and good biodegradability. However, the low melt strength of PLA has greatly limited its melt processing such as casting or blowing film, and finally limit its application as packaging. Therefore, firstly the mechanical properties of the PLA were modified by blending with PBS and PBAT; then the melt rheological properties of PLA ternary blends were modified by peroxide in reactive extrusion, and the enhancement effects were evaluated by rheological studies here. Rheological properties revealed that peroxide can greatly enhance the melt strength of PLA ternary blends. A PLA ternary blends/peroxide system can be a good candidate to fabricate biodegradable films with high toughness via stretching shaping process such as casting or blown film.
Poly(Trimethylene Terephthalate) Toughened With Biobased-Rubber: Morphological, Mechanical, And Blend Characteristics
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. 
Effect Of Cooling Time, Packing Pressure, And Antistiction Coating On Replication Of Micro Molded Substrates
Micro injection molding is one of the most widely utilized technologies to manufacture micro parts. One of the most challenging aspects in micro injection molding is to understand the role of different processing parameters on the quality of replication of the micro-features. This study will examine the effects of packing pressure in order to replicate micro features with high filling accuracy for micro molds with oval and cylindrical shapes. Moreover, part demolding is a critical factor where the chance of damaging the created patterns is high. So, cooling time is examined to eliminate micro pillar distortion during part demolding. Furthermore, the ability to mold micro pillars using a silicon mold without antistiction coating using Thermoplastic Polyurethane (TPU) is investigated. A key finding was that the degree of distortion of the micro pillars edges during demolding stage is strongly related to cooling time. Silicon molds were used in this study because of the ease of fabrication of cavities at a micron scale in these materials following deep reactive ion process even though silicon is not an ideal mold material as it is brittle and the polymers tend to adhere to silicon during processing. Keywords: micro/nano injection molding, microfabrication, packing pressure, cooling time, antistiction coating.
Aerobic Biodegradation Of Bioplastics Under Different Environmental Conditions
In recent years, the increasing concerns on the widespread use of petro-based polymers and the pollution problems associated with their inadequate disposal and handling are driving the development of new and more sustainable polymers, especially biodegradable plastics obtained from renewable resources. The biodegradability of biopolymers depends on their physical and chemical properties, but also on the environmental conditions of the biodegradation media, on which depends the type and availability of microorganisms involved directly in the biodegradation process. Biopolymers showed biodegradability in compost, soil and marine conditions, however, presents different biodegradation rates when compared between these environments. For example, polylactic acid (PLA) showed an excellent biodegradation in compost. Conversely, in marine environment, PLA presented low mineralization rates, while polyhydroxyalkanoates (PHAs) presented an excellent biodegradation in marine conditions. In this sense, a biopolymer with a biodegradation rate around 10% may not be considered as biodegradable in any condition and their accumulation in ecosystems can result harmful. In this study, biodegradation of bioplastics under different environmental conditions are discussed.
Polycarbonate-Polyester Blend Degradation Behavior
Objective of this paper is to document the efficacy of additives being used to minimize the antagonistic effects of ester interchange reactions that take place during high temperature processing of polycarbonate and polyester blends. Polycarbonate/polyester alloys suffer from loss of physical properties and moisture resistance due to ester interchange reactions. With right additives, the physical properties can be improved. Six different additives, that are phosphorous compounds and oxides of metals in nature were used to blend polycarbonate (PC) and polyesters. To improve the miscibility between the PC and polyethylene terephthalate (PET), a compatibilizer was added. Based on physical and analytical properties, certain additives have been identified as performing better than the rest. The properties selected to study are focused on understanding the impact of these additives on hydrolytic stability, tensile strength, heat deflection temperature, impact strength, and enthalpy and rate of crystallization. Degradation of physical properties and decrease in enthalpy of crystallization are indicative of loss of long term chain order and formation of unwanted copolymers in PC/Polyester blends.
Effect Of Nanoclay On Dimensional Stability Of Biocarbon-Filled Polyamide 6 Biocomposites
The aim of this paper is to study the influence of combining two fillers on the coefficient of linear thermal expansion (CLTE) of polyamide 6 (PA6) hybrid nanobiocomposites. The influence of a new environmentally friendly filler (biocarbon) on the CLTE of PA6 biocomposites was examined and compared to its hybrid additionally containing nanoclay. The results were supported by morphological and thermal characterization showing that the CLTE of the nanobiocomposites were enhanced with the inclusion of a small amount of nanoclay. Accordingly, properties and potential applications of PA6-biocomposites were discussed.
Rheology Of Molten Polyolefin Interfaces: Slip In Shear, Hardening In Extension
While barrier, optical, dielectric, and mechanical properties of multilayer polymer films have been studied extensively, there is comparatively little regarding the melt rheology of these multilayer films that would inform secondary processes such as thermoforming and biaxial orientation. Here we expand on our previous work regarding polyethylene/polypropylene (PE/iPP) solid-state adhesion to study the molten interface of 640 layer PE/iPP films. The interfacial tension of a metallocene linear low density polyethylene (mlE) and metallocene iPP (miP) system was measured by blending miP into mlE. The small amplitude oscillatory shear (SAOS) data was fitted with the Palierne model to extract an interfacial tension. Interfacial slip of the multilayer mlE/miP system was observed at shear stresses greater than 10 kPa. While neither mlE or miP homopolymer exhibited strain hardening behavior, the 640 layer mlE/miP system possessed a higher plateau extensional viscosity than anticipated as well as pronounced strain hardening behavior. These results suggest the molten interface has a significant impact in the secondary processing of extruded polyolefin films and may be an avenue to enhance thermoformability of iPP films.
Polyhydroxyalkanoate (Pha) Based Sustainable Biocomposites With High Mechanical And Barrier Properties In Packaging
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.
Solutions For Polyamide Impact Modification Based On Ethylene Copolymers And Elastomers
The type, amount, and composition of the modifier and its interaction with the polyamide matrix determines the stiffness-toughness-flow balance of its blends with polyamide. Beyond these primary requirements, depending on the application, low temperature impact, color, gloss, heat resistance, melt strength in extrusion and blow molded applications influence the choice of the right modifier. In glass filled nylon, glass fiber wetting is also an important consideration. Bulk handling options with some modifiers can help manufacturing efficiency. Finally, the choice of the nylon (for example PA 6 vs. PA 66), molecular weight and end group concentration all affect the end use properties. This paper gives a balanced overview of various differentiated solutions to modify polyamides using blends with various ethylene based reactor or grafted copolymers. Modification of both PA 6 and PA 66 is discussed.
Development Of New Solid Conveying Model Based On The Actual Measurement Of Polymer Processing Properties
A new analysis of the solids conveying of single screw extruders is developed. The new model is based on an assumption that the compressed solid are transported to down channel direction by pushing up of flight on the screw, initially relative movement of barrel to the stationary screw. The new analysis when tested with measured polymer processing properties such as data of dynamic friction date, bulk density, and two lateral stress ratios, was found to be in excellent agreement with all geometry and operating conditions for the available experimental data.
The Screw Rheomter: A Novel Rheometry For The Thermoplastic And Rubber Material
A new rheology measurement for the gum rubber and rubber compounds has been conducted using screw rheometer. This device uses a new viscometric flow analysis of single screw extruders to measure shear viscosity, which is based upon 'the closed dischage' extrusion characteristic equation. The screw rheometer, which is characterized by self-plasticating, self-deaeration, mixing during measuring and fast measuring time, shows the average polymer properties of the sample because the measurement volume is large enough. This study especially shows that shear viscosity and stress relaxation experiments of gum rubber and compounds can be performed by using this device. The measured viscosity is a function of shear rate, thus it can be used for the analysis of processing, machine design and quality control of the rubber manufacturing. Also, a rubber relaxation time experiment was devised as a method to confirm the relaxation time in the processing range and is named 'Engineering Relaxation Experiment'.
Preparation Of Maleated Thermoplastic Starch And Its Graft Copolymers Via Reactive Extrusion
This article elaborates the production and characterization of maleated thermoplastic starch (MTPS) and MTPS-g-PETG (glycol modified Polyethylene terephthalate) graft copolymers using reactive extrusion. Maleated thermoplastic starch (MTPS) was prepared by reaction with glycerol and maleic anhydride in a properly configured twin screw extruder. Maleic anhydride (MA) promoted cleavage of the starch molecule resulting in lower molecular weight and increased hydroxyl groups. The % of glycerol grafted on starch backbone was calculated using soxhlet extraction with acetone. MTPS was transesterified with PETG in 30:70 ratio w/w to obtain graft copolymers. Soxhlet extraction with dichloromethane (DCM) showed that around 30 % PETG was grafted on MTPS. The results were confirmed by TGA and FT-IR analysis of residue and extracts. The tensile strength and % elongation of graft copolymer was less as compared to neat PETG but much better as compared to brittle MTPS. Finally, dispersion of MTPS in PETG as continuous phase was observed using the images from scanning electron microscopy.
Reinforcing Phenomena Of Elemental Carbon: The Case Of Carbon Black Vs. Biocarbon In Composite Uses
Synthetic elemental carbon (carbon black) has many applications. Carbon black has been used as a coloring agent and filler for rubbers in the manufacturing of tires. However, natural carbon (biocarbon)—traditionally used as a soil amendment— is carving its way towards industrial applications as a natural colorant for plastics and as a reinforcing filler in plastic composites. The reinforcing properties of elemental carbon are well known. However, the mechanism is still described mostly as physical interlocking and in some cases as an affinity between the rubber to specific morphologies present in carbon black. Elemental differences between these two sources of carbon are discussed in this paper as well as the mechanical and thermal properties of both materials when used as reinforcing filler in a plastic matrix.
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.
Characterization Of Polyolefin Recyclates Sourced From An Informal Waste Picker Community In Kenya
The issue of plastic waste recycling and the idea of establishing a circular economy of plastics is receiving considerable interest from society, policymakers, and industry alike. A truly sustainable development in this field, however, can only be achieved when finding proper solutions to recycling challenges in world regions where formal waste management systems are lacking. In this work, polyolefin recyclates sourced from an informal waste picker community in Nairobi, Kenya were characterized in terms of material composition and basic mechanical properties. It was found that despite the absence of formal waste management systems in developing and emerging economies it is possible to produce technically useful recyclates that may compete with today’s commercially available recyclate grades.
Piezoresistive Polymer Nanocomposites And Their Foams As Smart Sensing Materials
Conductive polymer nanocomposites (CPN) filled with conductive filler have become increasingly popular due to their combined flexibility and low cost. This work explored the electrical properties and piezoresistive behaviors of CPN consisted of high density polyethylene (HDPE) and thermoplastic polyurethane (TPU) as well as multiwalled carbon nanotube (MWCNT) and/or graphene nanoplatelet (GnP), and their foams. The study investigated effects of CNT-to-GnP ratio on CPN’s structural morphology, foaming behavior, electrical conductivity, and piezoresistivity. The preliminary tests for the recoverability and reproducibility of the materials piezoresistive measurements look promising, and a reallife application using this material has been demonstrated by constructing a prototype sensing device.
Mechanical Characterization And Effect Of Water Absoprtion On Pla/Carbon Fiber Composites In Injection Molding
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.
Investigation On Gas-Assisted Injection Molding (Gaim) For Improving Metal Injection Molding (Mim) Molded Quality And Properties
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.
Effects Of Coupling Agent On The Properties Of Hybrid Composites Via Direct Injection Molding
Hybrid composites are made by incorporating two or more different types of fillers in a single tailorable matrix. This paper investigates a direct injection molding technique applied to hybrid composites made of conventional carbon fiber (CF), glass fiber (GF), and environmentally friendly wood fiber (WF). The favorable combination of these fibers would lead to enhanced mechanical properties and reduced cost. The target markets for the developed hybrid composites could be construction, auto industry, aerospace industry, etc. To meet the strict requirements for these applications, the burning behavior and water absorption behaviors of these hybrid composites were also investigated. Coupling agents (CA), normally used in polymer composites to enhance mechanical properties, were also investigated on their effects on burning and water absorption behaviors.
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