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.
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.
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.
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.
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.
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.
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.
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.
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.
There has been little research on polyalkylene terephthalate modification by graft copolymerization with vinyl monomers. There is no reported information on graft polymerization in molten state. In this study, nadic anhydride was grafted onto polybutylene terephthalate (PBT) and polytrimethylene terephthalate (PTT) using a free radical initiator in an internal mixer. The influence of monomer and initiator concentrations on the degree of grafting was investigated. The degradation of these polymers during grafting reaction was investigated and characterized by complex viscosity.
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 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.
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.
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.
Conventional powder additive addition to high-density polyethylene was compared to the use of melt formulated (Type B), compacted pellet (Type C) and ultra-high concentration masterbatch (Type A) blends. Performance advantages observed for the melt formulated and ultrahigh masterbatch blends in a previous study were confirmed. These advantages are attributed to the depression of peak melting temperatures as measured by DSC and synergistic effects of the additives. Additional work showed that masterbatch and melt blend preparation conditions alter the efficacy of the blend.
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.
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.
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.
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.
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.
The microstructure, thermal and mechanical properties of a range of natural fibres, derived from arable crops, are examined with a view to using these as reinforcing additives for thermoplastics. The fibres were characterized prior to incorporation into the polymer using a range of techniques, including SEM, image analysis and thermogravimetric analysis, at room and elevated temperatures. The thermal and mechanical properties obtained are discussed in relation to the measured composition and structural form of the fibres. Particular emphasis is given to determining the nature and consequences of fibre damage induced during meltprocessing operations, fibre orientation occurring in mouldings, and possible interfacial adhesion between the matrix and fibres, with and without the use of bonding agents. Novel processing techniques, including integrated compounding/extrusion and direct compounding injection moulding processing technologies, are considered as means for improving the quality of processed parts and the economics of manufacture.
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