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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The Incumbent Resin Effect for the Single-Screw Extrusion of Polyethylene Resins
Innovative polyethylene (PE) films are constantly being developed by switching the existing or incumbent resin with a new or challenger resin. If the extrusion equipment is designed properly, the film with the challenger resin will be acceptable for further testing and marketing. However, if the extrusion equipment is not designed properly, old degraded material from the incumbent resin will be pushed out of the extruder by the challenger resin, contaminating the test film. In many cases, the challenger resin incorrectly receives the blame for the gels. This paper describes the incumbent effect, presents a case study, and provides technical solutions.
Bioepoxy Foaming Using Polymethylhydrosiloxane
The Corporate Average Fuel Economy (CAFE) standards mandate that cars and light trucks have a fuel economy of at least 54.5 MPG by 2025 in an effort to eliminate 6 billion tons of cumulative CO2 emissions. This directive has spurred the automotive industry to focus on a variety of options. Among these are lightweight structural polymeric foams, which offer tailor-made solutions for significant weight reduction while not compromising on safety. However, most structural foams are petroleumbased, thereby contributing to the depletion of nonrenewable petroleum resources. Biopolymers, such as those from non-food based sources, offer a more environmentally-responsible alternative.
In this study, the effect of polymethylhydrosiloxane (PMHS) as a foaming agent on the properties of pine oilbased epoxy was investigated. The resulting materials were then tested for their compression properties, density, and microstructure. Lightweighting of up to 77 % was obtained and the delayed addition of foaming agent was shown to be more effective at improving specific mechanical properties, relative to immediate addition of foaming agent.
Thermal and Mechanical Properties of Epoxidized Pine Oil and Acrylated Epoxidized Soybean Oil Blends
Synthetic polymers derived from crude oil are widely used across various industries. However, increased environmental regulations tackling climate change have spurred interest in development of bio-sourced polymers. While promoting the cause of sustainability, biopolymers also possess inferior mechanical properties, limiting their widespread use. A plausible and cost-effective way of enhancing the properties of pure biopolymers is to blend them with other polymers and/or reinforce them with stiff fibers. This study investigates the thermophysical properties of bio-based thermoset blends of epoxidized pine oil (EPO) and acrylated epoxidized soybean oil (AESO). The blends were prepared via casting in five different ratios by volume (EPO/AESO): 100/0, 90/10, 80/20, 70/30, and 0/100. Mechanical properties of blends were studied via tensile testing and scanning electron microscopy, while chemical properties were analyzed using thermo-gravimetric analysis.
Production of Controlled Rheology Polypropylenes from Metallocene and Ziegler-Natta Resins
Peroxide induced controlled degradation of polypropylene has been well studied for commodity Ziegler-Natta based polypropylene (ZN-PP) resins and it is practiced industrially for producing resins of controlled rheological properties with accompanying narrower molecular weight distribution (MWD). In the present work, this technique was also tested on metallocene-based polypropylenes (mPP), possessing an initial narrow MWD. Kinetic model simulation results indicate that the polydispersity index (PDI) of the mPP remains almost unchanged while reducing molecular weight (MW) with increased peroxide concentration. Based on this observation, experiments were carried out to demonstrate the possibility of producing controlled rheology polypropylenes (CRPP) having targeted weight-average MW but varying PDI from different commodity resins of mPP or ZN-PP type.
Study of the Preparation and Superiority Properties of the Novel Propylene-Based Elastic HMAs
The novel propylene-based elastic hot melt adhesives (HMAs) with improved adhesive and elasticity were first reported and prepared by styrene-assisted melt free-radical grafting of maleic anhydride. The changes in chemical composition, thermal property, melt viscosity, and adhesive performance were measured by FTIR, GPC, TREF, rheology, TEM, melt flow indexer, and Intron universal testing machine, respectively. Compared to the commercial HMAs, the propylene-based elastic HMAs with special continuous phase distribution exhibited 20% increasing in peel strength, and doubled 100% tensile deformation recovery rate, which achieved a consistent of high degree of adhesion and elasticity. Meanwhile, the weather resistance test results also indicated that the propylene-based elastic HMAs had excellent resistance with high and low temperature shock, which alleviated the interface delamination caused by the different thermal shrinkage between the steel interface and plastic interface, further benefitting and extending the service life of steel composite pipe.
An Effective Way of Processing Immiscible PP/PS Blends into High Strength Fiber
A new method for processing high strength fiber from immiscible PP/PS blends was developed. In contrast to conventional melt spinning with high jet stretch, the new method adopts a low jet stretch ratio and a subsequent hot drawing step above the Tg of PS for making a blend fiber with a highly oriented PP phase. Initial results demonstrated that 70/30 PP/PS blend fibers processed by zero jet stretch and 8X hot drawing at 100°C can achieve a tensile strength above 300 MPa, 6 times higher than that of corresponding blend fibers produced by conventional high jet stretch. This process also provides a new route for recycling immiscible polymer waste mixtures and may have a high potential for industrial applications. By making immiscible polymer blends recyclable, this method can lead to improved design flexibility for system integration and achieving multi-functional products.
Polyethylene Pipe Performance – Observations and Insights from Experimental Investigations
Over the past number of years, we have conducted extensive investigations of the Rapid Crack Propagation (RCP) behavior of Polyethylene (PE) pipes. In this paper, we report on our findings on the relationship between the Small-Scale Steady State (S4) RCP test and the Full-Scale RCP test. We also report on the behavior of three different PE resins by generating the more extensive critical temperature – critical pressure maps (“failure envelopes”), which provide a more comprehensive view of the RCP behavior of PE. Next, using data generated in our laboratory, we report on a new observation relating critical temperature and critical pressure. Lastly, we report on the effects of extrusion rates and conditions on RCP performance. These results, taken together, allow us to make some interesting observations and offer newer insights about the RCP behavior of PE resins and pipes.
Development of a New Styrenic Elastomer Using Renewable Monomer
Utilizing a new renewable monomer called B-farnesene, Kuraray has developed a new hydrogenated styrene farnesene copolymer (HSFC) with unique chemical structure and differentiated properties. B-farnesene is produced from the fermentation of sugar extracted from sugarcane and is based on an innovative microbial engineering technology from Amyris. When B-farnesene is polymerized using anionic polymerization method, polymerization proceeds with conjugated diene moiety and poly-B-farnesene possesses a highly condensed, long alkyl side chain. This unique chemical structure results in differentiated features that conventional hydrogenated styrenic block copolymers (HSBC) do not have. In comparison to HSBC, HSFC exhibits higher flow ability, good adhesion, lower hardness without plasticizer, good permanent and compression set, and improved damping properties over a wide temperature range. With this property set, HSFC lends itself to applications such as adhesives, gels, low hardness compounds, and nonwovens. It is expected that HSFC will continue to expand and produce new market value to meet developing customer needs.
Rubber Toughened Polylactide (PLA) via Catalyzed Epoxy-Acid Interfacial Reaction
Polylactide (PLA) is a promising material, with favorable modulus, renewable sources, and biodegradability. However, its low extension at break (4-7 %) and toughness (notched Izod, 26 J/m) limit its applications . PLA toughening has been the subject of recent reviews [1,2], and is the basis for several commercial products. This work aims to increase PLA toughness using rubbery linear low density polyethylene (LLDPE), glycidyl methacrylate functional PE compatibilizer (EGMA), and novel catalysts that promote copolymer formation at the interface of immiscible blends of PLA and EGMA/LLDPE. Droplet size was reduced from 2.7 ?m to 1.7 ?m with addition of 5 wt% EGMA, and further to 1.0 ?m with the addition of cobalt octoate catalyst. Extension at break of 200 % is achieved with only 5 wt% reactive compatibilizer, 15 wt% LLDPE, and 0.01 M cobalt octoate.
Morphology and Strength of Die-Drawn Porous Sheets from Highly Filled Polypropylenes
Highly oriented porous sheets can be produced from solid phase die drawing of polymer composites below the melting temperature. Talc filled polypropylenes with two different grades of talc having different particle size distributions and different mean particle sizes at the same filler loading of 50 wt% or 23 vol% were drawn in the solid phase through a converging die at 128°C. The highest draw speed that could be achieved at 128?C for the composite with the lower mean particle size was twice the maximum speed that could be achieved with the other composite. The higher maximum draw speed for the composite with a greater fraction of smaller particles may be attributed to greater tensile strength during drawing from the reinforcement provided by the undebonded particles.
A Study on the Mechanical Properties of Recycling PC/ABS Blends Produced by Vent-Type Injection Molding
The mechanical properties of recycling PC/ABS blends produced by three kinds of molding conditions were discussed, including such parameters such as the cylinder temperature and the type of injection molding processes. Mechanical properties and the degradation rate with the increase of recycling times were investigated. The comparison of different cylinder temperature produced by vent-type injection molding was conducted, also the research between cent-type injection molding and non-vent-type injection molding, based on the detailed SEM observation on the fracture surfaces after Izod impact test. It can be found that, with the increase of recycling times, the material produced by vent-type injection molding machine demonstrated higher mechanical properties and lower degradation rate in mechanical properties than non-vent-type injection molding machine.
Research on Mechanical Coupling Strength and Coupling Design of the ABS Injection Molding
The ABS resin was widely used in automobiles, electric products, household appliances, building materials and household goods due to being inexpensive. Components which could be easily replaced were welcomed in structural design, as well. In the past, there had been much research on reinforced fiber plastics, but seldom on ABS resin. In this paper ABS resin specimens with an open hole were used to be tested and evaluated. The test specimens were fixed with both screws and rivet pin, which had the same diameter as the open hole. In this experiment, the specimens were placed between two flat steel plates and hand tight with screw (pitch 1mm and depth 0.7mm) or rivet pin. The load-displacement curves were recorded and analyzed, with the failure mode of the fracture section observed. By comparing the joint properties of ABS specimens on both cases including screw and rivet pin, it was obvious that screw had an advantage over rivet pin. In addition, the gate position relative to the flow direction had an influence. This experiment result was useful to shorten the design time, reduce costs and enhance the reliability of the products.
Fabrication of Glass mat Thermoplastic composite by Needling Punching Process
As well known, non-woven materials, because of simple preparation Process and wide range of applications, attract more and more attention. Needle punch process is widely used in textile area and expresses excellent performance. The introduced thickness-direction fibers via needle punched process play an important role to reinforce the composite in thickness which can minimizes delaminating problems. In this research, short glass fiber mat and plastic fabric produced by PP were used to fabricate thermoplastic composite through hot press process. The glass mat and thermoplastic mat were punched before hot pressing. This research mainly includes two parts, that is, effect of composites in different molding temperature on tensile properties, and the influence of composites in different needling density on tensile properties. Finally, cross sectional observations of molded sample were carried out using a scanning electron microscope (SEM), and the fracture characteristics were evaluated.
Critical Parameters of Generating PMMA Nanocellular Foam
In this study, Poly(methyl methacrylate) (PMMA) nano-cellular foams were successfully manufactured using two-step solid state foaming. PMMA of three different molecular weights was saturated in CO2 at 2000 psi (13.78MPa) and at different temperatures and the samples were subsequently foamed in a hot medium.
The results show that although the CO2 solubilities in PMMA of different molecular weights are similar, the morphology of the PMMA foams was very different. Nanofoams with a cell size of about 30-40 nm, and cell density of 1016cells / cm3 were successfully prepared using high molecular weight PMMA. The lowest relative density of the foam is around 0.25. However, PMMA of medium and low molecular weight could not generate nanocellular foams under the same processing conditions. The results first report that viscosity is one of the critical issues that affects the preparation of PMMA nanofoam.
Multi-Layer Rotational Molding of PE-PA Utilizing a Mulitphase Interlayer to Generate Mechanical Adhesion
Rotational molding is a plastic processing method for the production of seamless hollow bodies. Polyethylene is the by far most commonly used polymer in this process. Building up multi-layer parts containing a PE layer, is limited to few material combinations due to missing specific adhesion of PE to most other polymers. In this work, the possibility to produce multi-layer parts out of supposedly incompatible PE and Polyamide 12 is investigated. The adhesion between the layers was accomplished by mechanical adhesion within a multiphase interlayer. The peel strength was measured as a function of different processing parameters and layer setups. Additionally, the fracture behavior was characterized optically. Overall a significant increase of the peel strength was observed. The major influencing factors on the bonding strength were detected and characterized.
Development of a Predictive Power Law Relationship for Concentrated Slurries, Part 2: Experiment and Processing Implications
It is well established that the addition of solid particles into polymers can increase the melt viscosity significantly by perturbing the flow field and through particle-particle interactions or particle network formation [1-3]. Highly-filled polymer compounds can present processing challenges, including high screw shaft torque, energy consumption, pressure and melt temperature. This paper describes an evaluation of the effects of filler concentration on melt processing. The experimental results using a batch mixer are linked to the theoretical treatment of the rheology as a particulate percolating system with power-law behavior . The implications of the increase in viscosity with filler concentration on polymer processing will be discussed from a practical engineering perspective.
Rheology as a Tool to Evaluate Polymer/Active Pharmaceutical Ingredient (API) Solid Dispersions
Despite significant advances have been achieved in applying amorphous solid dispersion to enhance bioavailability of poorly soluble active pharmaceutical ingredients (APIs), there remain challenges in characterizing the microstructures of solid dispersions and correlating their performance with microstructures. This study focused on utilizing rheology as a tool to investigate and evaluate several model polymer/API solid dispersions prepared by various techniques with different mixing capabilities. Rheological responses of different model solid dispersions displayed a strong correlation between microstructures and viscoelastic properties. For the currently studied system, storage modulus and viscosities versus frequency of different solid dispersions indicated that the incorporation of API imparted a plasticizing effect to the polymer matrix. In comparison, crystalline/aggregated forms of the API exhibited a more elastic response than its amorphous/dispersed counterparts. In addition, a temperature ramp interrogation of a physical mixture of polymer and API captured a critical temperature, at which a transition in slope observed in the damping factor was attributed to the dissolution of crystalline API into the polymer.
Rheology Optimized Processing Temperature for Preparation of Amorphous Solid Dispersions via Hot Melt Extrusion (HME)
The production of amorphous solid dispersions via hot melt extrusion (HME) relies on elevated temperature, applied mechanical force and prolonged residence time, which can result in potential degradation and decomposition of thermally-sensitive components. In this study, the rheological properties of a physical mixture of polymer/active pharmaceutical ingredient (API) were utilized to guide HME processing temperature. A critical temperature, which is substantially lower (~13°C) than the melting point of crystalline API, was captured during a temperature ramp examination and regarded as the critical point at which the API molecularly dissolves into the polymer. After identification, solid dispersions were prepared by HME processing below, on, or above the recognized critical temperature and characterized by scanning electron microscopy, hot stage microscopy, Xray diffraction, differential scanning calorimetry and rheology. Physicochemical properties of resultant solid dispersions indicated that the obtained critical temperature is sufficient for the polymer/API system to reach a molecular-level mixing, manifested by the transparent and smooth appearance of extrudates, absence of API crystalline diffraction and melting peaks, and dramatically decreased complex viscosity. Once the critical temperature is achieved, further raising temperature only results in limited improvement of the dispersion, reflected by slightly reduced storage modulus and complex viscosity.
A Critical Review of a New Joint Test Proposed in NCHRP Report 190
Pipe joint performance is a critical factor in the overall pipe system success. Design of joints is more complex than the design of the pipe wall. There are many different joint designs manufactured and marketed by the pipe industry for non-pressure pipe designs. The recent National Cooperative Research Program (NCHRP) project report 190 attempts to address the structural performance, largely based on shear failure at the joint. This project did a very good job of analyzing the shear and rotation stresses for concrete, corrugated steel, PVC, and HDPE on a limited number of joints. There are practical issues with the recommended test. This paper focuses only on the thermoplastic pipe designs.
Bonding of Plastics
Many types of polymers are not weldable. For example, thermoset polymers cannot be welded. While thermoplastic polymers are considered weldable as a class, most combinations of dissimilar plastics cannot be welded. Even plastics within the same generic grouping may not weld easily because of high crystallinity or high melting temperature, widely differing melt flow indices, or high melt viscosity.
In this presentation, the basics of adhesive bonding of plastics will be given. This will serve as review for some and introduction for others. General topics include surface preparations and primers, joint design, selection of adhesives, and some specific ideas on bonding of difficult materials such as fluoropolymers and elastomers.
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