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.
Epoxy resins are known to have numerous applications. To improve their performance of the epoxy, we are applying molecular reinforcement by using polymer liquid crystals (PLCs). PLCs are well known for their excellent dimensional stability, good mechanical properties, high temperature usability, and outstanding environmental resistance. A novel retention class of LC thermosets can be obtained by endcapping mesogenic rigid rod molecules with reactive glycidyl groups. These thermosets potentially combine the performance of an epoxy resin with the excellent properties of LC. We have studied the simultaneous cure of the monomer liquid crystalline epoxy (diglycidyl ether of 4,4'-dihydroxybiphenol) with an anhydride cured diglycidyl ether of bisphenol F (DGEBP-F) epoxy. As a first step to determine optimum conditions for network formation, we report on the curing kinetics of molecular reinforcement of epoxy with a monomer liquid crystalline epoxy (MLC). The study was done by Differential Scanning Calorimetry (DSC) using autocatalytic expressions. Dynamic Mechanical Analysis (DMA) is used to verify compatibility of the blended systems by investigating the glass transition temperature as a function of %composition.
Plastic pallets and containers are used increasingly for storing, moving and warehousing various industrial and consumer products, thanks mainly to its several benefits besides environmental consciousness. The conventional wooden pallets are limited in their load capacity, useful life, cleanability, and above all, imaginative product-specific design. Contrarily, the structural foam molded plastic pallet, meets the demands heavy payloads, dynamic and impact loads, hostile weather conditions, size limitations, process effects, strength and stiffness requirements. Plastic pallets are used for up to 30000 lbs carrying capacity. Beyond their passive appearance, the plastic pallets are a product of engineering optimization encompassing materials, technology, design, stress analysis, and several end-use specific constraints. This paper is a review of the various considerations involved in the computer aided engineering of pallets as a product class.
In order to produce thermoformed products of consistent quality, an understanding of the effect of material and process parameters on end part performance is necessary. In this investigation the effect of pigment, nucleating agent, and recycling regrind on the nucleation of homopolymer isotactic polypropylene have been studied. Differential Scanning Calorimetry was used to reveal the effect of these additives on the crystallinity, type of crystals, crystallization and melting temperatures at different cooling rates. It has been found that percentage cystallinities were increased as the concentration of the nucleating agent and first and fifth generation regrinds increase up to the saturation level. Although more hexagonal ? crystals were formed by increasing the concentration of the pigment, the enthalpy of fusion was decreased.
Polyvinyl butyral (PVB) sheet is used as the energy absorbing interlayer in most safety glass applications including automobile windshields. A large supply of industrial and post-consumer PVB scrap is currently being disposed of by burning and landfilling. Polymeric modifiers can be used to compatibilize blends of PVB with PVC and polyolefins. These alloys can have a wide range of useful properties ranging from super-tough thermoplastics to thermoplastic elastomers.
As part of on-going studies on the manufacturing of re-engineered materials from waste plastic streams, rheological, mechanical and thermal characterization of recyclable plastics from old computer housings and used carpet materials were carried out, with anticipated use in thin-walled products. A combined stress and mold cavity flow analysis has been used to obtain optimum design and process parameters for the anticipated products.
The gelling of soy protein-based PRF wood adhesives is studied. Soy protein isolate, in combination with phenol resorcinol formaldehyde (PRF) resins is useful in the finger joining of lumber. This unique technology has several advantages including an ability to bond green lumber, very rapid set at room temperature, excellent water resistance, and reduced formaldehyde emissions. The goal of this study is to quantify the effect of soy protein hydrolysis conditions and amine functionality on the gelling and ultimate modulus of soy-derived wood adhesives.
The actuator arms in some hard drives were found to distort after being subjected to an 80°C environmental test. This distortion was believed to be due to a relaxation of thermal residual stresses in the glass filled polyphenylene sulfide component of the arm due to the molding process. Changes were made in the molding process and this diminished the problem but did not eliminate it. Differential scanning calorimetry test on the plastic revealed that physical aging of the PPS was occurring during the 80°C environmental test and the changes in the molding process would have little impact on the motion which resulted in this process.
One of the most common environmental exposures that nylon undergoes when used for automotive applications is that of salt splash, which commonly occurs during winter driving. This study looks at the effect of various salts (NaCl, KCl, CaCl2) on the mechanical and thermal properties of nylon when exposed to one and four molar aqueous salt solutions. Also, the partition of the salt/water solutions was studied, as well as the preferential absorption of one salt over another.
This research seeks to determine the effect of chlorinated hot water on slow crack growth resistance in polyethylene using a test methodology that is quick and inexpensive. This will be done through the use of three point bend tests on specimens completely immersed in a bath of chlorinated hot water. The results will then be compared with results from the same test run without chlorinated hot water. Comparative data will be used to determine chlorine's effect.
With the rising usage of plastic PET bottles and the rising need to recycle them, there is an increasing demand to refine the recycling process. It is very important to have the recycling process be cost and time efficient. The focus of this study is on the drying aspect of the recycling of PET. In this experiment, different parameters of the drying process were varied, specifically the time and the temperature. The strength was not significantly affected by time or temperature of drying. The melt index data showed that drying the PET at 177°C gave the best results. The overall best results seemed to be at 177°C, and a time around six hours. Longer or shorter drying times appear to degrade the material.
The selection of an automatic sortation system for separation of post-consumer bottles is of high importance for today’s recycler. The configuration of a modern recycling plant also needs to be carefully assessed, as different configurations in plant equipment have their own advantages and disadvantages and this can make the difference between a successful operation and a failure. This article examines the performance of spectroscopic sorting equipment in a recycling environment, which has to be viable at high speeds, problems associated with this technique as well as possible solutions to improve performance.
Environmental stress cracking (ESC) of acrylonitrile-butadiene- styrene (ABS) co-polymer caused by two kinds of non-ionic surfactants was studied by edge crack tension (ECT) tests. The dependence of the ESC on temperature and on the kind of surfactant was investigated. The fracture surfaces were investigated by a scanning electron microscope (SEM). It was found that the rise of temperature had a different effect on each surfactant. The crack propagation behavior of each surfactant at different temperatures was understood from the change of morphology at the crack tip.
Besides other facets of product development, it is imperative for medical device manufacturers to take great efforts through proper evaluation and consideration of material properties under practical conditions to prevent product failure at the end-uses. The environmental stress crack (ESCR) induced by chemical agents plays a significant role on material performances. In this contribution, in-depth studies have been carried out on different medical plastic materials, such as polycarbonate, copolyesters, ABS, acrylics, rigid thermoplastic polyurethane and their blends. More attention will be focused on a copolyester material for its unique ESCR behavior. Variation of chemical agents (such as different types of hospital disinfection solutions) have great impacts on physical and functional properties. Various plastics shows distinct environmental stress cracking phenomena under different conditions. Mechanisms of ESCR phenomenon under different environments have been explored. Fibril reinforcement by cold crystallization and chain session by hydrolysis of the copolyester may have contributed to its excellent chemical resistance against a wide range of chemicals and its catastrophic failure in acidic or basic environment. In addition, appropriate definition of product failures is also critical in making materials decisions.
Polylactic acid, PLA, is a relatively new biodegradable polymer primarily used for biomedical as well as mass-market packaging applications. PLLA is a polyester comprising repeating units of the lactide residue with an asymmetric carbon atom. Because of its biodegradability to nontoxic products and good plastic properties of that polymer makes it suitable for use in film studies. De Santis and Kovacs showed that the unit cell of PLLA is pseudo-orthorhombic with dimensions of a=10.7 Å, b=6.45 Å, c= 27.8 Å and ?=?=?=90°, where the molecules assume a 10/3 helical conformation. (1).Eling et al reported the existence of another modification, which they called ?-crystal modification (2) Hoogsteen et al. studied the influence of the preparation conditions on the presence of the crystal modification (3). Fischer et al investigated solution grown crystals of lactide polymers (4). Also Kalb and Pennings estimated the crystallization of PLLA from bulk state and solution (5). Tadakazu and Masuko investigated the relationship between the fine structure of PLLA and its physical properties (6). The need for polymeric biodegradable films is well established. The use of films occurs in the packaging and disposable article industries. In light of depleting landfill space and adequate disposal sites, there is a need for biodegradable films. Currently films from nylon, polypropylene, polyethylene, polystyrene, PVC, are noncompostable, which is undesirable from an enviromental point of view (7). In this paper, we present our results on the development of structure in uniaxial and biaxial stretching of PLA and subsequent heat setting process as followed by the new spectral birefringence technique we adapted for rapid acquisition of birefringence during the course of heat setting.
Fish oil or conjugated fish oil was copolymerized with divinylbenzene and norbornadiene or dicyclopentadiene using BF3·OEt2 as an initiator in an effort to develop useful biodegradable polymers with rationally designed structures from natural renewable resources. Dynamic mechanical analysis, DSC, TGA and nuclear magnetic resonance spectroscopy have been used to characterize the resulting fish oil polymers. The results show that viable fish oil products ranging from rubbers to hard plastics may be synthesized by changing the type and amount of the comonomers used. The fish oil products are thermosetting polymers having highly crosslinked structures, glass transition temperatures ranging from 50 to 130°C, room temperature modulus of about 109 Pa, and excellent thermal stability, making the products useful for applications where current biodegradable plastics are not useable.
Recycling of polyethylene films  is carried out by their disintegration into regular flakes - the process is difficult because of dimensional (large surface, small thickness) and property (flexibility and rebound) characteristics of the films. The disintegration is typically carried out with the knife mills  which constitute the first units of the recycling line. Traditional mills operate on the principle of pressurized knife cutting  since it allows to carry on the disintegration at a narrow slit between cutting edges of the fixed (stationary) and the mobile (rotary) knives of the mill. Because of parallel arrangement of the edges and large surfaces of the films which call for high cutting forces the process induces strong vibrations [3, 4]. The latter are eliminated in the hyperboloidal - rotary cutting mill developed recently and evaluated in our lab .
In-line granulation, the size reducing of plastic trim as it comes off an extruder, tenter, frame, slitter or other production machine has many advantages over conventional trim handling methods. Small granulator size is an inherent requirement because of the limited installation space around these production machines and sound pressure levels must be low because of the proximity of the granulator to the machine operator. Precision Cutters, Inc. (PCI), has developed a unique line of small, very efficient, high productivity in-line granulators that meet all size and operating requirements for use in this advanced, closed, one-step trim to granulate process. The engineering principles of film granulation and throughput rates in kgs/kw-hr (lbs/hp-hr) are covered.
A complex carpet residue is obtained as a byproduct in the tertiary recycling of nylon-6 fibers from used carpets. It consists of mainly polypropylene, styrene-butadiene rubber and calcium carbonate, and is potentially a low cost, high volume waste stream with consistent properties. In this study, composites of carpet residue with polyethylene were evaluated for building and construction applications. As received carpet residue was first compounded with low density polyethylene, homogenized and devolatilized in a twin screw extruder. Later, blocks were prepared by the intrusion process and tested for their mechanical and thermal properties as well as the leaching characteristics of heavy metals and organic carbon. It was demonstrated that the prototypes of these blocks can be potential candidates for use in a novel thermal spacer application.
Inflatable structures are gaining wide support in planetary scientific missions as well as commercial applications. For such applications a new class of materials made of laminating thin homogenous films to lightweight fabrics are being considered as structural gas envelops. The emerging composite materials are a result of recent advances in the manufacturing of lightweight, high strength fibers, fabrics and scrims. The lamination of these load-carrying members with the proper gas barrier film results in a wide range of materials suitable for various loading and environmental conditions. Polyesterbased woven fabrics laminated to thin homogenous film of polyester (Mylar) are an example of this class. This fabric/film laminate is being considered for the development of a material suitable for building large gas envelopes for use in the NASA Ultra Long Duration Balloon Program (ULDB). Compared to commercial homogenous films, the material provides relatively high strength to weight ratio as well as better resistance to crack and tear propagation. The purpose of this paper is to introduce the mechanical behavior of this class of multi-layers composite and to highlight some of the concerns observed during the characterization of these laminate composites.
On-going research focuses on understanding the mechanochemistry during Solid-State Shear Pulverization (S3P) of recycled polypropylene (PP) and its blends. Free radicals formed during this process act as compatibilizing agents for ordinarily incompatible polyolefin blends. It was observed earlier with Nuclear Magnetic Resonance spectroscopy that each S3P cycle converts a small portion of polypropylene chains from isotactic to atactic stereoregularity. Small amounts of such atactic chain segments impart additional levels of toughness, which offset, in part, the damage associated with the inevitable chain scission. We determined how many processing cycles S3P-made recycled PP can endure without significant loss of mechanical properties.
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