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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INITIAL STUDIES ON DOUBLE NETWORK GLASSES
DGEBA-based epoxy and stoichiometric blends of flexible aliphatic and rigid aromatic amines are cured in two stages to produce double-network glasses. The low reactivity of the aromatic amine permits the selective reaction of the aliphatic amine in the first stage, and mechanical properties are measured above Tg without significantly advancing the cure. The second stage reacts remaining epoxide and aromatic amine functionalities. Network properties depend strongly on composition and conversion, however no phase separation is observed. Experimental results are compared with theoretical models of blend properties to illuminate the nature of the interactions between the two amines in the networks.
MIXING OF POLYMER POWDERS IN A ROTATING MOLD
As rotational molding parts become more and more complex, understanding how the polymer moves inside a rotating mold is important for good parts quality. Since the polymer is in a powder form, a distribution in particle sizes is present and each size can have very different flow characteristics. In this work, powder mixing and flow behavior are studied in terms of homogeneity and time to achieve equilibrium. To do so, mixing experiments of free flowing polyethylene particles have been carried out in a rotating glass cylinder. The parameters studied are: rotational speed, filling ratio, relative powder composition and particles sizes. In order to follow particles of different sizes, the original powder was sieved and each sub-size group was differently colored to be tracked in motion. The experiments were filmed with a camera under different angles and image analysis is performed via the Grey Level Co-occurrence Matrix to quantify mixing dynamics and color intensity analysis (RGB) characterization to determine powder dispersion.
MORPHOLOGY AND MECHANICAL PROPERTIES IN WELD LINE OF INJECTION COMPRESSION MOLDINGS
The weld line of injection moldings often becomes a problem since they are the weakest part of the molding and would affect aesthetic properties, especially when rigid fibers are incorporated into the resin. Cracks would usually initiate from weld lines especially when the resin is sensitive to notches. Therefore, the injection-compression molding technique was applied in an attempt to improve the surface appearance as well as strength of weld line regions. The effect of injection-compression molding conditions on the morphology and mechanical properties of the weld line region is discussed.
MECHANICAL HOLE BURNING SPECTROSCOPY TO PROBE POLYMER HETEROGENEITY
Mechanical Hole Burning Spectroscopy (MSHB) was recently proposed as a method to probe the dynamic heterogeneity of polymeric materials. Here we show how the MSHB technique can be applied to a triblock copolymer and to polymer solutions. The heterogeneity of a styrene-isoprene-styrene block copolymer was investigated in the vicinity of its order-disorder transition temperature (ODT). It was found that MSHB is not only able to qualitatively distinguish the heterogeneous region from the homogenous one but also is sensitive to the ƒ??depthƒ? in the heterogeneous regime. We also examined the heterogeneity length scale represented by entanglement density by performing MSHB experiments on polystyrene solutions of various concentrations and molecular weights. We find that the MSHB response is not sensitive to the entanglement density while the behavior in the Rouse regime provides evidence of dynamic heterogeneity. The response appears homogeneous in the terminal regime.
EFFECTS OF DEFECT ON MECHANICAL PROPERTIES OF SHEET MOLDING COMPOUND
Sheet molding compound (SMC) consisting glass fiber mat and unsaturated polyester resin has been used to make many structural parts with complicated shapes. However during the compression molding, defects such as weld line and undulation of sheets would generated. Therefore at current study, static tensile test and tensile fatigue test were performed by using SMC molded plates with weld line and notch to investigate the effect of defects. It was found that the tensile strength of SMC molded plates with weld line was almost same as that of plates with notch in the static and fatigue tests. That is to say that weld line damages the strength of plates similar to notch. And both of tensile fatigue strengths of SMC plates with or without the weld line were about 28% of static tensile strength.
LASER SURFACE TREATMENT OF THERMOPLASTIC POLYMERS: INFLUENCE OF THE ATMOSPHERE NATURE
This work demonstrates that the affinity of a polymer with a polar liquid can be modified with a pulsed Nd:Yag laser technique. Our results concern experiments carried out on a technical thermoplastic polymer. The amplitude and the persistence of the laser treatment are explored by contact angle measurements carried out on irradiated polymers. The influence of parameters such as the intensity of the laser beam is clearly shown. The nature and the pressure of the treatment gas (air oxygen argonƒ??) are of first importance since they directly control the positive or negative evolution of the polymer-liquid affinity.
A NUMERICAL STUDY ON BLOW MOLDING FOR MANUFACTURING PET BOTTLE CONSISTED OF SINGLE BODY
Forming of PET bottle was performed by injection-stretch blow molding. Blow molding is the process of blowing pressured air into heated preform to make contact with mold cavity. In this paper, the aim was to improve reliability of technical stabilization for the PET bottle that is last productive product and process technology which was able to do maximization by a preform performance enhancement of the uniform thickness that took temperature and a characteristic of materials. Preform design and molds manufacture were conducted using injection blow molding analysis results. Therefore thickness error of 5% for PET bottle can be obtained in this paper.
FOAMING POLYPROPYLENE WITH NANOCLAYS
The object of this paper was to investigate extrusion foaming of different nanocomposites prepared with a linear polypropylene and chemically modified montmorillonite. A chemical blowing agent was used with dies of 2 mm diameter mounted in a single screw extruder. Although the filler loading was about the same in the two nanocomposites the quality of the foam produced was quite different: one of them was all closed cell and had a more uniform cell size distribution. This nanocomposite had two distinct characteristics: the melt displayed strain hardening in uniaxial extensional flow while the other did not and its crystallization temperature was higher than that of the other nanocomposite.
ULTRASOUND AIDED EXTRUSION PROCESS FOR PREPARATION OF POLYOLEFIN-CLAY NANOCOMPOSITES
A continuous ultrasound assisted process using a single screw compounding extruder with an ultrasonic attachment was developed to prepare polyolefin/clay nanocomposites. High density polyethylene (HDPE) and isotactic polypropylene (PP) were compared. The feed rate that controls the residence time of the polymer in the ultrasonic treatment zone was varied. Die pressure and power consumption were measured.Rheological properties morphology and mechanical properties of the untreated and ultrasonically treated nanocomposites were studied. Similarities and differences of obtained nanocomposites are discussed based on their properties and structural characteristics.
ON THE INTERFACIAL BONDING CHARACTERISTICS BETWEEN POLYOXYMETHYLENE AND POLY(LACTIC ACID)
Successful blending of polyoxymethylene (POM) and poly(lactic acid) (PLA) was possible due to the presence of compatible functional groups in both components. However, the extent of interfacial adhesion between POM and PLA is still unclear and therefore will be elucidated in this study. The interfacial bonding strength between POM and PLA was investigated by injecting these materials through separate injection units into a single mold cavity so that the two melt fronts meet to form a weld line. The effect of POM concentration at the interface on the bonding strength was also determined by blending it with varying amounts of PLA prior to injection. The highest strength was obtained when the weld line was formed between neat POM and neat PLA. The strength of the weld line exceeded that of the bulk materials and fracture occurred away from the weld region. The blending of POM with PLA significantly improved their ductility. However, the bonding between POM/PLA blends and neat PLA was weakened especially when the POM content was reduced to become a minor phase in the blend. Etching of the PLA phase at the fractured regions revealed very interesting spherulitic patterns, which indicates unidirectional propagation of POM spherulites across the interface to form transcrystlline regions. This effectively contributed towards the strengthening of the interfacial region.
CHALLENGE STABLE MOLDING PROCESSES WITH CONFIDENCE!
What is the hidden potential of stable molding processes where are the envelope borders? Difficult to answer indeed. The polymer phenomena the interaction with mold components the runner-system and the process can hardly be understood intuitively any longer. Advanced polymer system simulation is required to confidently find ways from a stable process-setup to a more profitable within the molding window. Imagine 6 existing similar 4-cavity-2-component molds and market demands pressure to invest into mold no. 7. This paper focuses on this two component process discusses the improvement found by 3D polymer system simulation and the gains which were realized.
CHALLENGE STABLE MOLDING PROCESSES, WITH CONFIDENCE!
What is the hidden potential of stable molding processes, where are the envelope borders? Difficult to answer, indeed. The polymer phenomena, the interaction with mold components, the runner-system and the process can hardly be understood intuitively any longer. Advanced polymer system simulation is required to confidently find ways from a stable process-setup to a more profitable within the molding window. Imagine 6 existing similar 4-cavity-2-component molds and market demands pressure to invest into mold no. 7. This paper focuses on this two component process, discusses the improvement found by 3D polymer system simulation and the gains which were realized.
MECHANICAL PERFORMANCE AND FRACTURE CHARACTERISTICS OF INJECTION MOLDED R-PET/PE-E-GMA BLENDS
The effect of the amount of reactive additive and screw speed during extrusion on the morphological characteristics and mechanical performance of recycled poly(ethylene terephthalate) (RPET) has been investigated. With the increase of E-GMA additive content, a gradual increment in Izod impact strength of the RPET/E-GMA blends was initially recorded. Subsequent increments in E-GMA content to above 13.5 wt% led to a drastic enhancement in the toughness of the blends. Meanwhile, the density of the blends decreased with increasing amount of additive E-GMA. The toughness and density of the blends were found to be dependent on screw speed during the extrusion. In addition, ductile and microporous structures could be observed from the Izod impact fracture surfaces.
LESSONS LEARNED THROUGH DEPLOYING AN UNCONVENTIONAL DESIGN FOR LEAN SIX SIGMA DEPLOYMENT PROGRAM
In early 2005 Xerox Corporation began deployment of their Design for Lean Six Sigma initiative. This unconventional program structure was built around elements such as a unique competency-based certification process and a push coaching model. Throughout the program development and deployment to the technology and product development community there were a series of lessons learn. These typically focused on what worked did not work and was ultimately could be characterized as interesting. This paper outlines what was learned and the impact these lessons had on the overall Design for Lean Six Sigma program.
EFFECTIVENESS OF TALC AS REINFORCEMENT FOR RECYCLED-PET/PE-G-MA BLENDS
Recycling post-consumer PET bottles is an essential and practical solution to reduce the amount of waste discarded at the landfills. Several methods are commonly used to recycle PET such as fiber making, sheet extrusion and injection molding. However, PET is known to exhibit low notched impact strength and low heat distortion temperature. In this study, an impact modifier was successfully used to enhance the toughness of recycled RPET (RPET). Subsequently, talc, which is typically used in polypropylene, was introduced into RPET and its effectiveness as a reinforcement was evaluated. It was noted that the heat distortion temperature (HDT) of the composites increased significantly with increasing talc content.
OPEN-CELLED THERMOPLASTIC FOAM FOR AQUEOUS-BASED FLUID ABSORPTION
The development of open-cell foaming technologies opens a new avenue in the search for less expensive alternatives to conventional absorbent materials used in personal care and hygienic products. This paper presents a systematic study conducted on the development of low density, open-celled thermoplastic foam for aqueousbased fluid absorption. Open-celled polystyrene foam structures were fabricated using extrusion foaming techniques with n-butane as blowing agent. Sulfonated polystyrene was introduced to the polymer system to improve the hydrophilicity of the polymer system. The effect of the addition of such surfactant on the cellular morphology and water absorption ability was examined.
EFFECTIVENESS OF SUPERCRITICAL FLUID FOR FOAMING OF POLY(LACTIC ACID) DURING INJECTION MOLDING
Poly(lactic acid) (PLA) is one of the most favorable candidates to replace conventional packaging materials due to its biodegradability and sustainability. However, its high viscosity and density often poses a challenge to melt processing especially injection molding. In this study, PLA was injection molded and foamed by using supercritical N2. Injection molding parameters such as mold temperature and SCF content were varied in order to investigate their effects on foam cell size. The effects of nucleating agent on the foam structure and cell size distribution were also elucidated by image analysis. Impact and dynamic mechanical performance of the foams were also evaluated.
EFFECT OF NATURAL FIBER SURFACE TREATMENT ON THE INTERFACIAL ADHESION AND MECHANICAL PERFORMANCE OF POLY (LACTIC ACID)-BASED TEXTILE INSERT MOLDINGS
Poly (lactic acid) (PLA) is known to be a relatively brittle material, which significantly narrows its window of application. Natural fibers such as jute have therefore been incorporated into PLA in order to improve its mechanical performance while maintaining its biodegradability. However, most injection molded PLA-based natural fiber composites consist of short fibers. This study involves the usage of textile insert molding technique to incorporate continuous natural fiber mats onto PLA substrates. This unique technique is extremely versatile, fast and most importantly prevents exposure of the natural fibers to high temperatures for long periods of time. A naturally derived surface treatment, i.e. aqueous shellac resin, was also used to treat the surface of the natural fibers to modify interfacial adhesion. The effect of shellac concentration on the mechanical performance of the moldings was elucidated.
GRADIENT MULTILAYER FILMS BY FORCED ASSEMBLY COEXTRUSION
A breakthrough in the design of novel uneven" split layer multiplying dies has enabled co-extrusion processing advancements from uniform to gradient layer thickness multilayered films. "Uneven" split layer multiplier and "forced assembly" technology provides flexibility in the design of gradient multilayer film distributions by (1) altering the die A/B split ratio and (2) changing the sequencing of a series of "uneven" split layer multiplying dies. Flexibility in the design of gradient layer distributions allows for the development of unique multilayered films for a variety of applications. Gradient films with layer thickness distributions in the micro- and nanometer scale have been shown to possess wide optical reflection bands which are envisioned to be used as light enhancers filters and reflectors in electronic and information devices. A breakthrough in the design of novel uneven" split layer multiplying dies has enabled co-extrusion processing advancements from uniform to gradient layer thickness multilayered films. "Uneven" split layer multiplier and "forced assembly" technology provides flexibility in the design of gradient multilayer film distributions by (1) altering the die A/B split ratio and (2) changing the sequencing of a series of "uneven" split layer multiplying dies. Flexibility in the design of gradient layer distributions allows for the development of unique multilayered films for a variety of applications. Gradient films with layer thickness distributions in the micro- and nanometer scale have been shown to possess wide optical reflection bands which are envisioned to be used as light enhancers filters and reflectors in electronic and information devices and controlled release applications. "
PROPOSAL OF WET REGULATED INSULATION MOLD SYSTEM (WRI-MOLD) FOR HIGH-GRADE SURFACE QUALITY UNDER LOW INJECTION PRESSURE
In most injection molded parts, the surface appearance is especially important to enhance aesthetic qualities. Surface irregularities such as sink marks, weld lines and flow marks are undesirable although often unavoidable. Therefore, a novel concept, known as WRI-molding, was introduced whereby the temperature of the mold cavity and core surfaces were carefully regulated in order to change the tackiness of the resin as well as to generate resin movement towards the cavity surface to compensate for any surface irregularities of the product. Another interesting aspect of this technique is the possibility of producing moldings with good surface appearance under low injection pressures, irrespective of whether the material involved is of a neat resin or a filled composite system. The effectiveness of the WRI-molding technique in surface replication and enhancement of surface gloss in moldings will be discussed.
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