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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Flow Induced Coating of Polymer Processing Additives: Development of Frustrated Total Internal Reflection Imaging
In the extrusion of polyethylene (PE), fluoropolymer-processing additives (PPA) are used to eliminate the surface defect known as “sharkskin” by coating the die wall and inducing slip at the PPA/PE interface. We describe a method to carry out in situ measurements of the coating kinetics by exploiting the optical phenomenon of frustrated total internal reflection (F-TIR). The estimated coating thickness was found to be significantly lower (60 to 350) nm than reported previously (5 to 15) ?m. The proposed coating mechanism may have origins at the die entrance.
Radiation Processing for Modification of Polymers
Radiation processing has been demonstrated on a large commercial scale to be a very effective means of improving end-use properties of various polymers. It is a well-established and economical method of precisely modifying the properties of bulk polymer resins and formed polymer components. The reactions of cross-linking, degradation and grafting on polymers initiated by radiation have found many useful applications in plastic and rubber materials. Important properties of polymer materials, such as mechanical properties, thermal stability, chemical resistance, melt flow, processability and surface properties can be significantly improved by radiation processing. Modern high energy, high-power electron accelerators have made industrial irradiation processes attractive with high throughput, low cost and other advantages over conventional chemical processes such as lower emissions of volatile organic compounds (VOCs), better energy utilization and precise process control. This paper provides a review of the basic principles of and main applications for radiation processing of polymers, as well as the prospects for new applications of this technology in the future.
An Experimental Study on the Effects of UV Absorbers Stabilization of Slip Agents in Water Bottle Closures
This investigation is an attempt to identify potential effects of the degradation of polymer slip agent additives on the organoleptics of bottled water. Specifically, research was done to evaluate the effects of UV light degradation on LDPE water bottle closures. The scope of this study was to determine if the addition of UV absorbers would eliminate potential UV degradation of the slip agent, which can have adverse effects on the taste and odor (organoleptic) properties of bottled water. Sample chips containing various loading levels of UV absorbers and slip additives were produced. Taste surveys were then used to characterize the performance of the manufactured test samples.
Evaluation of Antioxidant Performance of a Natural Product in Polyolefins
Mixed tocopherols were evaluated for antioxidant performance in polypropylene and polyethylene in combination with a phosphite secondary antioxidant utilizing a 2-factor central composite experimental design with oxidation induction time as the response. A commonly used phenolic antioxidant and synthetic vitamin E (?-tocopherol) were evaluated in comparison. Mixed tocopherols were found to have a greater antioxidant effect than the phenolic control and a similar to slightly greater effect than vitamin E in both polypropylene and polyethylene. No significant effects of the phosphite on oxidation induction times were observed for either of the tocopherol based antioxidants.
Process Aid Optimization in Uni-Modal HDPE Blown Film
The performance of several fluoropolymer process aids was evaluated in a high molecular weight, uni-modal HDPE. The process aids were tested for the ability to eliminate melt fracture during blown film extrusion as a function of process aid concentration. Results indicate that process aid performance varies widely; most effective are those designed to control the morphology of the fluoropolymer – HDPE blend delivered to the extruder die. Further evaluations using white (TiO2) and extended white (TiO2 + Calcium salt) pigments during film production show that extended white pigments can negatively interact with fluoropolymer process aids, although the degree of interaction differs between process aid types. The most effective process aid was scaled-up in a plant trial, and found to match or exceed the predictions from the lab evaluations.
Effect of Elevated Temperature on Erucamide Partitioning in Polyolefin Films
Erucamide is incorporated into polymer films to reduce their coefficient of friction (COF). However, the COF reduction may be influenced by a film’s exposure to elevated temperatures during storage or subsequent processing. At elevated temperatures, erucamide may be lost from the film surface to the surroundings, undergo chemical change or decomposition, and/or migrate back into the film. The major objective of this work was to investigate the fate of erucamide upon exposure to a higher temperature. Based on results from ATR-FTIR spectroscopy and solvent washing on one surface of the film it appeared that, upon exposure to the elevated temperature (55°C), the initial reduction in erucamide surface concentration was due to migration of erucamide back into the film. A subsequent slight reduction may be due to the decomposition of erucamide.
Study of Phlogopite Mica as Fillers for Polyethylene and Polypropylene
Phlogopite mica is an abundant micaseous mineral being experimented of its usage as reinforcement in plastics. In this study the mechanical and rheological modifications due to phlogopite mica as filler in polyethylene and polypropylene materials were determined. And relative comparison was made with the fillers: talc and calcium carbonate, which are currently standard fillers for plastics.The phlogopite mica filler showed better tensile strength, and flexural modulus properties than calcium carbonate but lower than talc as filler. The cost of this mineral is lower than talc and CaCO3 (calcium carbonate) depending on the purity and particle size of the mineral.Phlogopite mica is hygroscopic, nontoxic and even has nutritious value, has light brown color and due to its higher aspect ratio gives higher shear stress and apparent melt viscosity than other fillers at the same concentration.
Percolation Behavior of Thermoplastic Polymer Composite
Model thermoplastic composites containing both micro and nano filler particles were prepared and their melt flow behavior investigated near the physical gel point or percolation threshold loading levels. The threshold loading level was found to be strongly correlated with the particles size of the fillers and independent of the extrusion shear rate. Since the processing and compounding of high-surface-energy nano-particle filled polymers is very complex and not well understood, this study demonstrated the validity and adequacy of percolation study of such composites in steady-state pressure-drive flows using capillary melt rheometer.
Properties of Polypropylene Nanocomposite Prepared by Different Way of Compounding
Sodium montmorillonite (MMT Na+) was modified by co-intercalation, i.e. simultaneous action of octadecylamine and stearic acid in different ratios. The amount of MMT Na+ was calculated as 5 wt % to the weight of PP. Co-intercalation was carried by the mechanism of ion-dipole reaction and the achieved result was measured by XRD technique. The modified MMT and polypropylene (PP) were mixed on a one screw KO Kneader Buss with maleic-anhydride-modified PP (PPMa) as a compatibilizer. The content of PPMa in mixtures was 5 wt % to the weight of PP. The level of MMT exfoliation in the nanocomposite systems was also studied by SEM technique. The properties of samples were evaluated by DMA analysis (E*modulus 50°C and 100°C) and by the measurement of mechanical properties (break point and break strain). To assess the systems´ morphology SEM technique was used. The influence of different ratios of the individual components on the properties of polypropylene nanocomposites is discussed.
Halogen-Free Flame Retardant Cable Materials: How Oligomeric Vinylsilanes Make the Difference
It has been almost 25 years since the first halogen-free flame retardant (HFFR) compounds were reported at the “International Wire and Cable Symposium”. The first generation of HFFR materials possessed excellent fire and smoke properties, but were physically weak and were slow to process when compared with the PVC compounds which they were replacing.Today the majority of thermoplastic HFFR cable materials is made of aluminum trihydrate (ATH) and ethylene vinylacetate (EVA) and occupies a rapidly growing and specialized area of cable production. Vinylsilane adhesion promoters make possible the high loading level of ATH required for effective flame retardation, improve the processability of highly-filled EVAs and enhance the mechanical properties of the finished product.This presentation provides an overview of recent HFFR developments with oligomeric vinylsilanes used as adhesion promoters to make highly demanding thermopastic HFFR cable materials. The formulation and compounding of HFFR cable materials and the impact of various vinylsilane adhesion promoters on tensile strength and elongation at break performance is reviewed. New oligomeric vinylsilanes outperform commonly used monomeric vinylsilanes, even at a lower dosage. In addition, the vinyl/peroxide ratio plays an important role in fine-tuning the formulation.
Tailoring the Fire Retardant Performance of Polymers Using Multi-Component Processing Technologies
The addition of fire retardants to polymers generally causes a deterioration in mechanical properties and an increase in melt viscosity, reducing processibility. These effects are exacerbated as additive levels are increased, as is usually the case with fire retardant fillers, such as magnesium and aluminium hydroxides. Although this drawback can be overcome to some extent using filler surface treatments and processing aids, costs are increased and fire retardant efficiency may be compromised.This paper considers the use of multiple-component processing technology as a means of minimising the deleterious effects of fire retardant fillers, by locating these functional additives in the surface regions of mouldings, where they are most effective in minimising ignition on exposure to a combustion source. In this way, the core of processed parts can be made from unmodified polymer or from material with reduced fire retardant loading, thereby maintaining mechanical integrity.Results will be presented demonstrating the potential benefits of this concept, by reference to various hydrated filler/polymer combinations, in parts made with different skin/core thickness ratios.
PET Surface Modification Using Hydrophilic Dendritic Polymers
PET is commonly used in biomedical applications because of its desirable bulk properties. However, the surface of virgin PET is prone to protein adhesion and hemocompatability problems. The goal of this study is to create PET with better wettability by grafting hydrophilic dendritic polymers to the surface. The grafting procedure includes plasma treatment of the PET surface, grafting of an intermediate epoxide-functionalized polymer, and final grafting of the dendritic molecules. Dendritic molecules with both hydroxyl and amine functionality were studied. Silicon wafers were also used as model substrates to investigate the sequence of surface-chemistry steps. Successful surface grafting was achieved on the silicon wafers with static water contact angles as low as 36° for the amine-terminated dendrimer. Preliminary experiments showed that the surface-modified PET films exhibited higher contact angles due to partial dewetting of the intermediate epoxy layer leading to incomplete surface coverage.
SBM Block Copolymers, or the Power of Nanostructuration
SBM is a new family of copolymers constituted of three blocks of linear chains covalently bonded to one another : polyStyrene, 1,4polyButadiene and syndiotactic polyMethylMethacrylate. Because of repulsive interactions between the three blocks, SBM self-organize at the nanometer scale.Blended with compatible polymers, SBM imposes a nanostructuration to host matrices yielding a combination of properties otherwise difficult to obtain.The polar and apolar moieties on the same molecule render SBM ideal interfacial agents for many incompatible systems, offering innovative possibilities in the design of new high performance polymeric materials.
Compatibilisation Studies of Blends of Polybutylene Terephthalate (PBT) with Metallocene Linear Low-Density Polyethylenes
PBT like many other polymers is a brittle material with a high modulus value not suitable for certain applications. Blending and compatibilising with an incompatible polyethylene phase may improve these properties. The compatibilising agent, maleic anhydridegrafted- LLDPE, is physically miscible with the polyethylene phase and has a chemical functionality with the carboxylic and hydroxyl end groups of the PBT phase. The use of a new generation mLLDPE (ENGAGE ™ by Dupont) was also studied to investigate its suitability as a modifier for the polyester grade. The influence of the percentage composition of the mLLDPE and the effect of the addition of the compatibiliser were both investigated for their effect on the mechanical properties and were both shown to significantly improve modulus and elongation properties of the final product.
Iinfluence of Carboxylic Acids Additives on the Flow Properties and Slip Behavior of Thermoplastic Melts
An experimental study of slippage induced in various thermoplastics in rheometers by the presence of small amount of different carboxylic acids as additives is described. Capillary and coneplate experiments are reported. A series of polymers of varying polarity including polyethylene, polypropylene, polystyrene, poly methyl methacrylate and polyamide-12 are compared. Both aliphatic fatty acids and aromatic carboxylic acids are used as additives. The aliphatic fatty acids include propionic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, eicosanoic acid and commercial stearic acid (mixture of tetradecanoicacid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid). The aromatic carboxylic acids include benzoic acid, p-toluic acid, and 3-phenylpropionic acid. The greatest effects were found in polyethylene and polypropylene. Little or no effects are found with the other polymers. The most effective additives were aliphatic fatty acids. Aromatic carboxylic acids had some effectiveness. Mechanisms for this behavior are discussed.
Polymer Layers Grown from Gold and Polymer Film via Surface-Confined ATRP
Surface-confined atom transfer radical polymerization (ATRP) was tested and characterized on gold (Au) and then used to modify ethylene-acrylic acid (EAA) copolymer surfaces. For reaction from the gold surfaces, self-assembled monolayers (SAMs) consisting of alkane and acid thiols were initially prepared. This allowed for the chemistry that was developed to be transferred directly to the EAA surfaces without alteration. For both EAA and the Au-SAMs, the acid groups were used to ultimately attach the bromo-initiator. Both poly(methacrylic acid) (PMAA) and poly(methacrylamide) (PMAAm) were polymerized from the Au-SAM and EAA surfaces. The progression of the reactions and properties of the subsequent modified surfaces were studied using ER-FTIR and ATR-FTIR spectroscopies. The polymer layer that was grown gave substantial change in the polymer surface properties, but more importantly the ability to graft polymerize from polymer surfaces offers substantial potential for advanced polymer surface and device design.
Breakthrough Polymer Finishing Technology: Manufacturing Productivity and Polymer Performance Enhancements
The viscosity of polymers can be reduced at typical molding stresses and temperatures by the addition of a small amount (? 2 percent by weight) of a micron-scale solid. Although many solids may exhibit some effect on polymer viscosity, naturally occurring, non-toxic, amorphous aluminosilicate glass is the only solid that is effective over a wide range of polymer compositions and temperatures while at the same time having no demonstrable effect on nucleation of semi-crystalline polymers. Extensive research on poly(propylene), used as a representative polymer, indicates that rheologic properties described herein are dependent on particle composition, size range and concentration. The effect of the solid on the liquid polymer can thus be selected depending on the chosen particle characteristics. For most finishing applications, the practical benefit of the solid additive includes increased productivity, but may also include lower molding temperature, increased mechanical properties of the finished polymer, improved dispersion of additives, and better fit and finish of the article.
Effects of Concentration, pH, and Temperature on Ink Removal from Printed High Density Polyethylene Sheets by Alkyl-Trimethylammonium Bromides
Ink removal from printed high density polyethylene surface was performed using three different cationic surfactants: dodecyl-, tetradecyl-, and cetyltrimethylammonium bromide (i.e., DTAB, TTAB, and CTAB, respectively). These surfactants are chemically different in the number of carbon atoms of the alkyl tail group (i.e., 12, 14, and 16, respectively, for DTAB, TTAB, and CTAB). It was found that increasing the carbon chain length of cationic surfactant increased the deinking efficiency. It was also found that an increase in pH level and concentration of surfactant helped promote the deinking efficiency, while an increase in the solution temperature from 30 to 45°C either increased or decreased the ink removal.
Melt Processing of Thermally Unstable Polymers Plasticized with CO2
The effects of plasticizing acrylic copolymers, in particular a 65% (molar) polyacrylonitrile/ 25% (molar) methyl acrylate/ 10% rubber (PAN/MA/rubber) copolymer, with carbon dioxide (CO2) are studied. Previous work included differential scanning calorimetry (DSC), used to evaluate the resulting shift in the glass transition temperature (Tg) following plasticization, and pressurized capillary rheometry to evaluate the melt rheology prior to and after plasticization. A series of capillaries is used to evaluate the entry pressure effects and to observe the pressure effects of CO2 on the copolymer. The plasticizing effects of CO2 on the AN copolymer are observed to have a nonlinear pressure dependence, possibly indicating a higher plasticizing effect at higher pressures.
Controlling the Performance and Rate of Degradation of Polylactide Copolymers
An important factor in the commercial development of biodegradable polymers is the ability to control the rate of degradation. Ideally, the polymer should not degrade during functional use, but degrade quite rapidly when discarded. This paper discusses various aspects associated with the control of the rate of degradation of polylactide copolymers; both from the perspective of stabilizing the polymer during processing and product use, and subsequently accelerating the rate of degradation after disposal. Of particular interest are the influences of molecular weight, crystallinity, end-capping and plasticization.
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