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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THERMAL AND MECHANICAL PROPERTY OF PLA STEREOCOMPLEX WITH IMPACT MODIFIERS
Polylactide, polyester derived from renewable resources, can be synthesized using either L-lactide or D-lactide. A unique crystallization behavior of poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA) stereocomplex(SC) was observed when a PLLA/PDLA blend was subjected to the specific melting conditions. Therefore, we tried to blend PLLA and PDLA at overall compositions to form PLA stereocomplexes. Moreover, impact modifier was added to enhance the mechanical properties such as impact strength. The presence of the SC in the PLLA matrix was verified by differential scanning calorimetry (DSC). Thermal and mechanical property of stereocomplexes were investigated by DSC, HDT, Izod impact tester, UTM.
MODIFICATION OF BIOPOLYMERS, ESPECIALLY POLYLACTIDES, FOR TECHNICAL APPLICATIONS
Next to the established packaging market the interest for biopolymers in technical application increases more and more. Especially automotive industry is interested in substituting oil-based polymers with biopolymers. In view of that, the focus of the work described here was on optimization of injection molding of polylactide (PLA) in order to improve material performance for technical applications. Furthermore, the effects of poly-D-lactide (PDLA) as nucleating agent, fibers and modifiers on material properties (e.g. heat resistance, mechanical properties) are reported.
DEVELOPMENT OF A CHANGEABLE MANUFACTURING SYSTEM FOR THE PRODUCTION OF THERMOPLASTIC FUCTIONAL ASSEMBLIES
New and innovative production systems are required in order to withstand the growing pressure of costs and competition in the plastics processing industry. Changeable manufacturing systems are one potential solution. These enable companies to adjust to repeatedly changing market conditions by themselves. At the University of Kassel's Institute of Materials Engineering, a changeable production system has been developed which is specially tailored to the requirements of plastics processing. The potential and limits of a changeable system for plastics processing are to be established on the basis of the pilot plant that is currently under construction.
STUDY ON THE EFFECT OF VARIOUS WF, GF AND POLYMER TYPES ON CHARACTERISTICS OF DIRECTIONAL COMPRESSION MOLDED WPC AND COMPARISON WITH PROFILE EXTRUDED WPC
A compression molding system was custom built to impart directional flow properties in Wood plastic composites (WPC). Wood fiber (WF) and glass fiber (GF) of two different fiber lengths and HDPE of two different melt flow index (MFI) was used as matrix polymer to study their effect on mechanical properties of WPC. Tensile strength and flexural strength of the composites were determined. Experiments were also carried out to compare flexural strength of profile extruded and compression molded WPC with various WF contents to understand changes in mechanical property. The paper presents these results and compares with each other.
INFLUENCE OF PROCESSING CONDITIONS ON THE THERMOFORMABILITY OF PP-SHEET MATERIAL
The quality of semi-finished products, as they are used in thermoforming, highly depends on the raw material used and their processing history. As a consequence, variations in sheet quality are often observed with their influence on processibility and product properties. Currently, there is no standard test for thermoforming sheet materials available, which means it is not possible to accurately predict how a material will behave in thermoforming. This study deals with the prediction of the thermoformability of sheet materials. A novel test method (Thermoforming Material Characterization TMC) to predict thermoformability is presented.
IN VITRO DEGRADATION OF LACTIDE BASED POLYMERS AND COPOLYMERS
This study evaluates the in vitro degradation of scaffolds and films prepared from lactide based polymers and copolymers. The materials studied were poly(L-lactide)(PLLA), poly(DL-lactide)(PDLLA), a poly(L-lactide/æ-caprolactone) copolymer (PLCL) and a poly(DL-lactide/glycolide) copolymer (PLGA). The effect of the addition of bioactive particles such as hydroxyapatite and bioglass in the degradation kinetics was also investigated. It was found that the degradation in cast films was faster than the degradation in porous scaffolds; in addition, bioactive particles delayed the degradation of polymers studied.
IMPROVING INTERFACIAL ADHESION IN WOOD PLASTIC COMPOSITES
The aim of this work was to improve the interfacial adhesion between the matrix and the wood particles in polypropylene based wood plastic composites with the addition of chemical agents at the wood particle surface. We found, that with the addition of rather small, linear molecules, e.g. e-Caprolactone, interfacial adhesion, and therefore tensile strength, was improved up to 10% additionally to the benefits of a common maleic anhydride based compatibilizer. Furthermore, we found that also the chemical composition of the molecules added at the surface shows an influence at the extent of the improvement.
EFFECT OF AGING ON MECHANICAL BEHAVIOR OF A BIODEGRADABLE POLY(LACTIDE-CAPROLACTONE) COPOLYMER
Poly(L-lactide/æ-caprolactone) (PLCL) was physically aged at 36§C and 40% of relative humidity (RH) to study the evolution of its structure and mechanical properties with time. Samples with an initial amorphous PLCL matrix, obtained by fast quenching from the melt were characterized before and during aging. The changes in structure and mechanical properties were studied using differential scanning calorimetry (DSC), X-Ray diffraction (WAXS) and tensile tests. As a result of aging, PLLA crystals were formed within the multiblock copolymer prompting to an increase in stiffness and to a loss of its elastomer-thermoplastic behavior of PLCL.
EFFECT OF SOFT SEGMENT MOLECULAR WEIGHT ON THE MECHANICAL AND STRUCTURAL PROPERTIES OF SILICA FILLED POLYURETHANES
In this work, we consider the effect of the addition of functionalized silica to a series of poly (tetramethylene oxide) (PTMO) based polyurethanes. We have synthesized urethanes with different molecular weight soft segments (PTMO) and evaluated both structural and mechanical properties. The mechanical data show a reinforcing effect occurs when the urethanes is filled. The FT-IR spectra show that the hard domain hydrogen bonding is unaffected by incorporation of silica. However, at elevated silica levels, the silica appears to attach onto the free carbonyls. These effects are dependent on the MW of the PTMO soft segments.
CONCURRENT AND CRYSTAL FORMATION DURING ISOTHERMAL CRYSTALLIZATIONS OF POLY (L-LACTIDE)
The effects of temperature on crystallizations of Poly (L-lactide) (PLLA) have been studied by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and atomic force microscopy (AFM). The quantification of both ñ and ñ crystal structures into the crystallized PLLA samples was determined for 90 ?§C < Tc < 150 §C. The shortest crystallization times were achieved at Tc =107.1 §C, where both ñ and ñ crystal develop in the same proportion. The crystal structure changes have also been observed by WAXD . AFM images show a crystallization temperature dependence of surface roughness, spherulite diameter and nucleation density.
FLAME RETARDANT PROPERTIES OF HIGH HEAT POLYCARBONATE RESINS
Applications such as certain lighting components and face shields require clear materials that offer a combination of high heat resistance and low flammability. The flame performance of a new class of polycarbonates, ranging in Tg from 165?§C to 185?§C, was evaluated to understand their suitability for such applications. The new high heat polycarbonates showed superior flame performance in comparison to conventional and other high heat polycarbonates. Further, the flame performance was maintained in presence of pigments. The improvements in flame retardant properties did not adversely affect the use temperature with respect to color or molecular weight retention at elevated temperatures.
EFFECT OF CHAIN EXTENSION ON THE PROPERTIES OF PLA/TPS BLENDS AND FILM BLOWING PROCESSING
The effect of a multifunctional epoxy-acrylic-styrene copolymer as chain extender (CE) on the properties of PLA/Thermoplastic Starch (PLA/TPS) blends was investigated and its effect on the processing of blown films was clarified. The PLA/TPS blends were prepared by twin-screw extrusion, which comprised 27%TPS in the PLA matrix and 36% sorbitol/glycerol mixtures as plasticizers in TPS. The viscosity of the blends was dramatically increased by adding a small amount of CE. This is of great interest for film-blowing since this process requires materials with high melt strength, which has been demonstrated by the successful lab-scale film blown trials.
BIAXIAL ORIENTATION AND PROPERTIES OF POLYLACTIDE/THERMOPLASTIC STARCH BLENDS
The biaxial stretchability of polylactide/thermoplastic starch blends was investigated. Blends were prepared via twin-screw extrusion. Water, glycerol and sorbitol were used as plasticizers. Interfacial modification was performed by grafting the PLA with maleic anhydride. A chain extender was also used. The addition of the grafted PLA yielded a finer TPS dispersed phase. These blends were drawn using a laboratory biaxial stretcher. The addition of TPS, grafted PLA and chain extender affected the biaxial stretchability of the neat PLA. Adding TPS to PLA resulted in a decrease of the tensile modulus but increased the elongation at break in some cases.
FABRICATION OF MICRO-DIES FOR EXTRUSION OF POLYMER MELTS
The ongoing trend for miniaturization demands research in the field of micro-extrusion. This work compares two techniques for manufacturing micro-dies; mechanical manufacturing and laser ablation. A micro-die needs to fulfill requirements such as fast nozzle exchange and high accuracy. The nozzle channel needs to have a diameter of less than 0.5 mm, a high quality and high aspect ratio. The disadvantages and advantages of both techniques are discussed while experimental data supports the discussion. The results go well with the expected behavior based on the nozzle channels geometry. Laser ablation is the tool of choice when manufacturing micro-dies for extrusion.
SEAL LAYER MATERIALS CHARACTERIZATION IN TERMS OF CRYSTALLINITY AND RHEOLOGY
A series of commercial seal layer grades ethylene vinyl acetate (EVA) resins were investigated in terms of thermal and rheological properties. The effect of vinyl acetate (VA) content in Differential scanning calorimetry (DSC) experiments revealed that the increase of VA content leads to decrease in melting point and heat of fusion. In oscillatory shear measurements the effect of long-chain branching on high shear sensitivity and long relaxation time of resins was revealed. In addition, a significant strain hardening behavior in extensional viscosity measurements was observed which indicated high melt strength of these resins.
CRITICAL ASSESSMENT OF SCRATCH VISIBILITY DETERMINATION METHODOLOGIES
The major objective of this work is to critically assess the similarity and differences between the two industrial scratch visibility determination methodologies: Erichsen and ASTM/ISO scratch tests. The assessment relies on the two evaluation methodologies: L for Erichsen and contrast for ASTM/ISO. A good correlation between the two methods can only be established if a contrast criterion is also utilized for the Erichsen test. The surface deformation that gives rise to light scattering such as the scratch profile and the surface roughness on the scratch path were studied for both methods and their implication on scratch visibility will be discussed.
ACCELERATED ENVIRONMENTAL AGEING OF MATERIALS USED FOR COLLAPSIBLE FUEL STORAGE TANKS
The purpose of this work was to perform a comparative analysis of various candidate nitrile coated fabric materials supplied by potential vendors to be used as fuel storage tanks and compare the results to the currently fielded polyurethane storage tanks. Our strategy is to utilize advanced environmental ageing methods to simulate extended weathering conditions. Our results demonstrate that the nitrile coated fabrics performed well in our evaluation. Their breaking strengths are about equal to the currently fielded urethanes and they performed comparably when subjected to environmental ageing conditions.
HIGH TEMPERATURE MECHANICAL PROPERTIES OF PEROXIDE CROSS-LINKED ETHYLENE-OCTENE COPOLYMER
Ethylene-octene copolymer (EOC) was cross-linked by dicumyl peroxide (DCP). Thermoplastic vulcanizate (TPV) based on polypropylene (PP)/EOC-DCP was prepared by dynamic vulcanization. Gel content was noted. Tensile creep properties of these samples at elevated temperatures (70- 200?øC) were studied. Residual strain after 100% and 200% elongation were examined. EOC cross-linked with lower peroxide levels underwent creep failure easily at lower temperatures even with small loads. EOC with 0.6 wt. % of DCP was found to be the strongest even at higher temperatures and lower temperatures with heavier loads.
A STUDY ON INJECTION-STRUCTURE COUPLED ANALYSIS FOR THE PREDICTION OF INTEGRATED METAL INSERT INJECTION MOLDING PARTS
This study proposes an injection-structure coupled analysis to quickly predict the deformation of the insert parts of small precise connectors. The flow pattern was determined through an analysis of the plastic injection molding of small precise connectors, and a structural analysis was performed using injection pressure. For this purpose, an injection-structure mapping program was developed to use the injection molding pressure as the input to the boundary condition of the structural analysis. The effect of injection molding, which varies according to the process conditions of the metal insert parts of small connectors, was analyzed through structural analysis.
COMPARISON OF SERVO AND PNEUMATIC ULTRASONIC WELDING OF HDPE SHEAR JOINTS
Pneumatic and servo-driven ultrasonic welding of HDPE shear joints were studied. For pneumatic ultrasonic welding, the effects of weld force, down speed, and amplitude of vibration on weld strength were studied. For servo-driven ultrasonic welding, the effects of velocity, velocity profiling and collapse distance during hold on weld strength were studied. Our goal was not to optimize the welding conditions but rather compare the operation of the two systems. Both systems worked well and produced consistent welds. More work is needed with both systems to better understand the ramification of some of the controllable parameters.
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