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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LOCAL PRESSURE FLUCTUATION AROUND A CAVITY SURFACE OF A HETEROGENEOUS NUCLEATION SITE
Heterogeneous nucleation in polymeric foaming processes forms at preferential sites such as phase boundaries or additives and requires less energy. Rough surfaces, especially cavities, on a processing wall or on additive particles are commonly found within a polymergas solution, and these are regions where cell nucleation can be initiated. In most previous studies on cell nucleation, a uniform pressure throughout the solution was assumed; and the discontinuity at the interfaces between the additives and surrounding material was neglected. A recent study  has shown that, the pressure and stress fields at discontinuities within a polymer-gas solution vary evidently from the surrounding areas due to the melt flow dynamic induced by the growth of nucleated bubbles; and regions at these discontinuities are the places where cells are propagated. However, the effect of surface geometry of an additive particle or the roughness of a processing wall, which is related to the underlying mechanisms of interfacial enhanced nucleation, has not studied. This paper presents a numerical analysis to investigate the pressure profile around a cavity surface inside a heterogeneous nucleation site. Such an investigation is expected to provide more insights to understand the cell nucleation phenomena.
EXTRACTABLES AND LEACHABLES: WHAT TO DO AND WHY TO DO IT?
The studies used to determine what chemicals (and how much of them) can move in some way from a source material (usually polymeric in nature) to another sink (food, pharmaceutical, the body, the air) falls into the general category of what is termed ƒ??extractablesƒ? and ƒ??leachablesƒ? studies. The reasons the studies are done are to meet regulatory guidelines and to aid risk professionals (toxicologists) in assessing a given products safety. In practice, it is the analytical methods used to detect, identify, and quantify the chemicals that migrate out of the base material that poses the most significant obstacle in helping risk assessors make a determination as to the risk posed by a given product.
A STUDY OF THE FACTORS INFLUENCING THE PERFORMANCE OF A DIRECT TO PLASTICS WATER BASED COATING FOR THERMOPLASTIC OLEFINS
There is an increasing trend towards the use of Thermoplastic Polyolefins (TPO) in the marketplace particularly in the automotive sector due to the desirable mechanical properties. In order to achieve adhesion of coatings to TPO, automotive manufacturers have traditionally used solvent based chemical adhesion promoters or other forms of surface pretreatment to overcome the lack of bonding sites on this low surface energy substrate. Each of these pretreatment methods has their own drawbacks and all add an extra step to the coating process. A water based direct to plastics (DTP) coating for TPO is therefore very desirable due to the lack of flammable, environmentally detrimental solvent as well as the elimination of the pretreatment step. The barriers to achieving adhesion to TPO with a water based coating include the inability to wet out water over such a low surface tension substrate and the lack of bonding sites on the substrate. Once the barriers to adhesion are overcome, the coating must still meet the performance requirements of the finished coating. This paper explores a water based DTP coating and the role that adhesion promoters, surface tension modifiers, and resin systems play in the adhesion and overall performance of the coating on TPO. The study indicates that the selection and concentration of each of these is very important in overcoming the barriers to applying a water based DTP coating to TPO and achieving the overall performance required. In addition, the curing schedule for the coating systems examined plays a critical role in achieving the desired results.
PHASE BEHAVIOR OF BLENDS CONTAINING POLY(RESORCINOL PHTHALATE-BLOCK-CARBONATE) AND POLY(ETHYLENE TEREPHTHALATE)
Polymer blends provide an efficient way of making new materials with improved properties. The miscibility of poly(resorcinol phthalate-block-carbonate)(RPC) and poly(ethylene terephthalate )(PET) blends is examined by differential scanning calorimetry and dynamical mechanical analysis. When the resorcinol phthalate level in RPC copolymers is as low as 20mol%, the blends show limited miscibility. As the resorcinol phthalate level increases from 40 to 80mol%, the blends go from being partially miscible to completely miscible. Understanding this phase behavior change in the context of the classical Flory-Huggin's theory is attempted.
POLYANILINE MODIFIED CLAY IMPACT ON POLYSTYRENE FOAMING ULTILIZING CARBON DIOXIDE BLOWING AGENT
Polyaniline-clay (PANI-MMT) nanocomposites were synthesized through in-situ polymerization of polyaniline with various dopants. Those nanocomposites were used to blend with polystyrene (PS) to form an expandable composite resin, which will significantly impact the foaming process using a CO2 blowing agent. The material composition and foam morphologies were characterized through various analytical techniques, such as, X-Ray diffraction (XRD), SEM, dielectric measurement, UV/vis, and FTIR. Based on our experimental results, we are proposing that the de-doped base form" of Pani-MMT nanocomposites and both "inorganic and organic salt-form" Pani-MMT nanocomposites will act as a "molecular CO2 reservoir" to control the CO2 releasing during the foaming. The selection and optimization on those compounds will be enormously important for developing a new inexpensive and environmental friendly blowing agent for the foam industry to achieve the final goal of replacing the existing CFCs /HCFCs /HFCs blowing agents!"
SIMPLE METHOD FOR CHARACTERIZING PURE MODE I INTERFACE FRACTURE COHESIVE LAW OF OF HYBRID JOINTS BONDED WITH DISSIMILAR ADHERENDS
The interface fracture process of most layered or bonded structures is commonly under the control of mixed mode cracking where the interface shear and normal fracture components exist simultaneously when the hybrid joints are bonded with different adherend materials. In this work, a simple and novel method is proposed to realize and characterize the pure mode I interface fracture for the hybrid joints with dissimilar substrates. The theoretical and experimental results indicate that the present method may be considered as a standard test method for the characterization of hybrid joints with dissimilar materials.
EFFECTS OF CHAIN BRANCHING ON THE FOAMABILITY OF POLYLACTIDE
In this work, polylactide (PLA) foams were prepared via a batch foaming system by using CO2 as a blowing agent. The foamability of four PLA grades were compared and the effect of chain branching on cell morphology was investigated. The thermal properties of PLA were analyzed by thermogravimetry and differential scanning calorimetry (DSC). The extensional viscosity of PLA was measured by using a rheometer with an extensional viscosity fixture (EVF). The relationship between the chain architecture, cold crystallization phenomenon, extensional viscosity and foamability of various linear and branched PLAs are explained in the conclusion.
INSPIRE At-Press TPO Technology
Traditionally automotive Thermoplastic Polyolefins (TPOs) have been made by compounding processes. The mixing of components at the molding press (At-Press) greatly reduces compounding cost while providing flexibility to dial in dimensional and mechanical performance. This technology also offers cost savings via inventory consolidation and simplified logistics. This paper presents results from Dow's INSPIRETM At- Press approach, which is designed to meet high end OEM specifications. The formulations are designed for mixing at the molding machine and delivering excellent talc and elastomer dispersion under the breadth of typical fabrication conditions. Part results validate good dispersion and distribution and equivalent properties to compounded TPOs. Consistency of At-Press process was demonstrated to be at the same level as compounded TPO. In this paper, At-Press blending is shown to be a very viable technology.
CONSTANT-TEMPERATURE EMBOSSING OF SUPERCOOLED POLY(ETHYLENE TEREPHTHALATE) BETWEEN TG AND TM
Constant-temperature embossing experiments were performed on supercooled amorphous PET films. The process was designed to achieve isothermal embossing so that cooling can be eliminated. Rather than using a conventional cooling process for solidification, the supercooled PET films, after rubbery softening, were hardened by crystallization at the same embossing temperature. The resulting cycle time is on the order of the characteristic crystallization time, approximately 1 min or shorter for supercooled PET in a large processing temperature window centered at 180?øC. In the testing experiments, parallel microtrenches of 20 ?¬m width and aspect ratio 2 were faithfully replicated from a silicon master onto the PET film without the cooling stage. The time and temperature dependent thermomechanical behavior of the supercooled PET film was studied to understand the underlying principle of this novel embossing process.
BREAKTHROUGH INVENTIONS IN POLYMER EXTRUSION
Vast improvements in polymer extrusion processinghave been achieved through innovations in machinery,screw and barrel designs, functional operations,monitoring and controls, resins, and fundamentals.Selected examples are given to illustrate the breakthroughmachinery inventions that occurred in the past 50 years inthis field. These inventions and their technical andindustrial significance will be discussed. Selectedexamples include the conception of the single and twinscrewextruders, and the vast functional improvements thataffected market demand of extruded products withconsistent quality at ever higher production rates. Storiesbehind some of the breakthrough inventions will also bepresented.
CYCLIC BLOCK COPOLYMER EXTRUSION CHARACTERIZATION
Extrusion experiments were performed on three Cyclic Block Copolymer (CBC) resins using a highly instrumented single-screw extruder. These materials are substantially fully hydrogenated styrenic block copolymer and they represent a class of optical polymers with excellent light transmittance and unique birefringence properties. The data collected indicate that a screw designed with a compression ratio near 3.0 and a compression rate of no more than 0.0045 mm/mm should work well for the targeted application. These experiments also revealed that CBC extrusion behavior is more sensitive to block copolymer composition than molecular weight across the ranges studied.
PLUG MATERIALS FOR THERMOFORMING: THE EFFECTS OF NON-PLUG MATERIALS FOR THERMOFORMING: THE EFFECTS OF NONISOTHERMAL
The plug-assisted thermoforming process is the largest and most important industrial thermoforming process. The main aim of this study was to investigate the interaction between the properties of the plug and the polymer sheet in thermoforming. Non-isothermal plug only thermoforming tests were carried out using identical plug designs for various combinations of plug and sheet materials. It was hoped that this study would help to improve the understanding of friction and heat transfer effects during the thermoforming process. The plug materials used included: Hytac-B1X (thermoplastic syntactic foam), Hytac-WFT (epoxy syntactic foam with added Teflon), Blue Nylon, and POM (polyoxymethylene). The sheet materials included aPET and polystyrene (HIPS). It was found that the magnitude of slip during plug contact was much higher with aPET than with HIPS and that this reduced as the temperature of the plug was increased. Different plug materials produced significantly different wall thickness distributions in the preforms. It was concluded that friction was the dominant effect during contact.
THIN-WALL INJECTION MOLDING OF OPTICAL GRADE POLYMERS
Thin-wall injection molding experiments and mold filling analysis were performed on four Cyclic Block Copolymer (CBC) resins. These materials are substantially fully hydrogenated styrenic block copolymer and they represent a class of optical polymers with excellent light transmittance and unique birefringence properties. These resins are currently under development for various optical applications including injection molded light guide panels and lenses. The thinwall injection molding behavior and impact performance of the four CBC resins was compared to a competitive polymethylmethacrylate (PMMA) resin.
EPOXY POLYMERS TOUGHENED BY TRIBLOCK COPOLYMERS
A poly(styrene ' butadiene ' methyl methacrylate) triblock copolymer (SBM) and a poly(methyl methacrylate ' butylacrylate ' methyl methacrylate) triblock copolymer were investigated as a toughening agents for a ductile epoxy resin. A carboxyl acid terminated copolymer of butadiene-acrylonitrile (CTBN) was used as a control (conventional toughening agent).The use of CTBN resulted in micron-size rubber particles (c.a. 3 microns diameter) and the use of SBM and MAM resulted in spherical, nanometer size rubber particles (c.a 40 nanometers in diameter). Interestingly, the SBM modifiers were found to be more effective toughening agents at high rubber contents. Scanning electron microscopy attributes the increase in toughness due to extensive matrix dilation and transmission optical microscopy suggests that more energy is dissipated per unit volume for the SBM modified epoxy.
THERMAL AND RHEOLOGICAL PROPERTIES OF PHB SYNTHESIZED WITH VARIOUS HYDROXYVALERATE CONTENT FOR POTENTIAL USE IN FOOD PACKAGING
PHB (Poly (3-hydroxybutyrate) families of naturally occurring polymers are extracted from micro-organisms.PHB behaves similarly to conventional thermoplastics, yet are fully biodegradable in common composting conditions.To improve flexibility for potential food packaging applications, PHB can be synthesized with various copolymers such as 3-hydroxyvalerate (HV). The objective of this study was to characterize the thermal and rheological properties of PHB synthesized with various valerate contents and relate these findings to potential food packaging applications.
STYRENIC BLOCK COPOLYMERS FOR THERMOPLASTIC POLYURETHANE MODIFICATION
Urethane based thermoplastic elastomers (TPU) have an impressive range of performance characteristics such as outstanding scratch/abrasion resistance, excellent oil resistance and high tensile and tear strengths. However, application of TPUs is limited when low hardness (<70 A) is required. Soft TPU materials with low level of hard segment are difficult to process. Commercially, low hardness products are produced by adding phthalate plasticizers, which are not desirable in some applications. The objective of this project is to study TPU hardness modification using styrenic block copolymers to achieve soft TPU alloys without significantly sacrificing other physical properties.
REAL-TIME MONITORING OF INJECTION MOULDING FOR PART MASS DETERMINATION
A methodology is presented for determining moulded part mass from a combination of continuous process measurement and known polymer material pressure-specific volume-temperature (pvT) characteristics. The methodology determines the mass of melt that has been delivered to the mould cavity through the swept volume of the injection screw, but taking into account melt compressibility. The screw position is continually monitored by a computerized system along with the melt pressure and temperature. Results show a good correlation between the predicted and measured specimen mass over a range of processing conditions.
AN OVERVIEW OF ENVIRONMENTAL ALTERNATIVES AS VIEWED BY A PLASTICS INDUSTRY ECONOMIST
The plastics industry has been under heavy criticism from environmentalists for contributing to pollution and litter, exposing consumers to toxic matter, and using more than its fair share of energy resources. Are any of these accusations valid? If so, has our industry been responsive to these challenges in a meaningful way? Do the solutions offered by the environmentalists, to the problems they raise, have merit? This paper will attempt to address major environmental issues at they concern the plastics industry from an economic and scientific viewpoint and summarize what makes sense and what does not.
CURRENT APPLICATIONS OF TITANATES AND ZIRCONATES - 2010
Titanate and zirconate coupling agents as invented by the author generate approximately six ACS CAS abstracted works (technical papers, articles and patents) per week. The author will review the literature and update ANTEC attendees on applications in thermoplastics and thermosets with an emphasis on the latest work in nano and green technologies such as biopolymers and landfill biodegradation. For example, investigators Lei, Yong; Wu, Qinglin; Yao, Fei; Xu, Yanjun from the School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA reported: Composites based on recycled high-polyethylene (RHDPE) and natural fibers i.e. pine wood flour and bagasse were made through melt blending and compression molding. The effects of the fibers and coupling agent type/concn. on the composite properties were studied. The use of maleated polyethylene (MAPE) carboxylated polyethylene (CAPE) and titanium-derived mixt. (TDM)-(20% pellet masterbatch of a neoalkoxy pyrophosphato titanate) improved the compatibility between the bagasse fiber and RHDPE and mech. properties of the resultant composites compared well with those of virgin HDPE composites. The modulus and impact strength of the composites had maxima with MAPE content increase. The composites had lower crystn. peak temps. and wider cryst. temp. range than neat RHDPE and their thermal stability was lower than RHDPE.""
FABRICATION AND CHARACTERIZATION OF POLYMER-BASED SILICA AEROGEL FOR ENHANCED MECHANICAL STABILITY
Silica aerogels have attracted attention for many applications due to their unique properties such as low density (0.003g/cm), mesoporosity (pore size 2-50nm), high thermal insulation and high surface area (500-1200m2/g). However, their fragility and environmental sensitivity restricts the use of monolithic silica aerogel. In this paper, silica aerogel that is cross-linked with diisocyanate is introduced and the effects of polymer concentration on aerogel properties, especially mechanical strength are discussed. Fracture of silicaaerogel mainly occurs at the interface of secondary particles that are formed during aging. It is believed that if the surface of silica aerogel is covalently bonded to nanocast polymer coating, the interparticle necks become wider and can reinforce the structure of the aerogel.
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