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.
Isothermal crystallization behaviors of poly (L-lactic acid) (PLLA) blended with different contents of Poly (D-lactic acid) (PDLA) were studied by wide-angle X-ray diffraction, differential scanning calorimetry and polarized optical microscopy. PDLA molecules added to PLLA formed stereocomplex crystallites in the PLLA matrix. The stereocomplex crystallites stayed unmelted at 190 °C and embedded in the PLLA molten matrix. Isothermal crystallization measurement at 100 °C revealed that the crystal radius growth rate decreased with an increase in the isothermal crystallization temperature. The spherulite growth rate has a peculiar PDLA concentration dependence. PLLA crystallization behavior might be affected by network structure and homogeneous dispersibility of stereocomplex crystal.
Recycled PET (RPET) is known to exhibit brittle behavior in the presence of notches. Therefore, we tried to improve the toughness and other properties of RPET by incorporating E-GMA, talc filler and engineering plastics as an impact modifier and talc to increase the rigidity and heat distortion temperature of RPET. As a result, these blends with E-GMA exhibited significantly higher stiffness and strength especially with increasing E-GMA content. In addition, these blends with talc filler indicated the high heat distortion temperature due to increase the crystalinity of RPET blends. Therefore, it was found that talc played an important role in enhancing the heat resistance of RPET. Some injection molding parts, i.e. tray, chopstick, and so on, were produced from these compound materials.
Conductive thermoplastic composite foams are a novel class of materials that can be an excellent candidate for producing cost-effective and lightweight products. In this work, electrically conductive polypropylene (PP) foams of various densities filled with varying contents of long stainless steel fibers (SSF) were successfully fabricated. The foaming of composites was achieved using a batch process and supercritical CO2 as the environmentally benign physical blowing agent. The PP-SSF foams maintained high level of electrical conductivity over a wide range of density reduction, depending on the initial loading of SSF. To better understand the conductivity behavior of solid and foamed composites, statistical percolation analysis was conducted. The analysis showed that the conductivity change with the foam density followed the percolation power law. The critical SSF concentration, calculated based on the sample’s final volume was 0.37 and 0.28 vol.% for the solid and foamed composites, respectively. In the current PP-SSF system, foaming decreased the weight up to ~70-80 % and lowered the percolation threshold by about 25%.
In order to keep the part quality under a stable mold temperature, a number of parts should be discarded until the mold temperature reaches to a stable condition. Depending upon process and environmental conditions, the time to a stable condition varies. In this work, influencing factors to the stabilized mold temperature condition are examined. The results show that ambient temperature significantly affects the stabilization time. To predict the stabilization time with consideration of heat transfer to the molding machine, heat sink attached model in the CAE analysis was suggested. It shows a good agreement with experimental result.
This paper describes the evaluation of the mechanical properties and flame resistance on bio-based polymer compounds of Poly (lactic acid) (PLA) and Polyamide 11 (PA11). A compounding technology and mechanical properties of PLA and PA11 using a compatibilizer were firstly studied to improve the thermal resistance and the impact strength of PLA. Some compositions of PLA/PA11 blends using a compatibilizer were investigated. After some flame retardants which were not halogenated and toxic materials were blended to the composition of PLA/PA11/compatibilizer, the mechanical properties and flame resistance were also evaluated as compared with the commercialized PLA and Polycarbonate (PC) alloy. The flammability test was conducted with the multi-cone calorimeter to obtain the relation between the heat release rate or the integrated heat release value and the combustion time.
High density polyethylene (HDPE) pipes have been used successfully in applications ranging from potable water lines to chemical fluid transmission for nearly four decades because of its superior mechanical and chemical properties over other thermoplastic piping materials. The standard method of joining HDPE pipe in the field is the butt fusion process. The quality of the butt-fused joints depends largely on environmental and joining surface conditions. The failure modes commonly observed in butt fused joints are poorly fused and contaminated joints and initiation of cracking at stress concentration defects in the fusion weld. In this paper, a case study of fusion joint failure in a fabricated elbow fitting due to poor manufacturing practices is presented. The mechanism and type of failure have been deduced from a detailed morphological examination of the fracture surface. Various factors responsible for a brittle failure of the butt fused joints have been identified. Analytical and thermal testing was performed to identify a specific material characteristic responsible for the failure.
This paper investigates the effect of fiber type and fiber content on the foaming behaviors of cellulose fiber reinforced polylactic acid composites. Two types of cellulosic fibers with different sizes were used: micro- and nano-sized fibers. The composites were prepared by a film casting and hot pressing method and then foamed via a batch foaming process with CO2. The morphology and volume expansion ratio of the samples with different cellulose fiber contents were compared. The results suggested that micro-sized fibers had negative effects on the foam morphology and nano-sized fiber positively influenced the foam morphology. It is speculated that the crystals generated around the fibers affected the cell morphology significantly.
Jute fiber has gained extensive use in recent years due to its advantage in environmental protection, low cost and low density. However, the limitation of its low mechanical property affects its application. Because of this reason, jute-glass hybrid fiber configuration was considered as an improvement. In this study, 2 kinds of jute-glass hybrid fiber configuration were employed to investigate the mechanical property and fracture behavior in different configuration. At the same time, different plies and different angle of the composite were analyzed. It was found the composite fabricated by B type fabric expressed better properties both on tensile and bending test. Scanning electron microscope observation was also found excellent matching between jute fiber and glass fiber in B type composite.
The recent push for environmentally friendly halogen?free products has resulted in significant changes in the of polymer materials used in consumer electronics industry. A series of halogen free polyphenylene sulfide (PPS) products were developed to enable consumer electronics original equipment manufacturers and their suppliers to design and make products that will comply with halogen?free industry standards. These halogen free PPS products offer inherent flame retardancy (UL-94 V0), high flow suitable for small connectors, and high dimensional stability for metal over molding parts without loss of superior mechanical properties.
An environmental friendly biodegradable polymer film was prepared from poly(lactic acid)/thermoplastic starch (PLA/TPS) blend by cast film process at 0, 5 and 10 wt% of TPS. The PLA/TPS blend films were heat sealed by a heat seal tester at a heat bar temperature of 90 and 100 °C. The heat seal time was varied from 0.5 to 2.0 s with a constant seal pressure of 0.2 MPa. The effect of heat seal conditions on heat seal properties of PLA/TPS films was investigated. Heat sealed strength was carried out by peel testing. Differential scanning calorimetry was used to analyze thermal properties and crystallinity of the heat sealed PLA/TPS films. From the results, heat sealed strength of PLA/TPS blend films decreased when increasing the heat sealed times. PLA films was peelable at the heat sealed temperature of 90 °C. PLA/TPS heat sealed films exhibited greater crystallinity than the PLA heat sealed film.
Electron induced reactive processing (EIReP) – an eco-friendly and sustainable reactive processing method based on the use of high energy electrons - was used for cross-linking of the elastomeric domain during melt mixing in order to prepare natural rubber (NR) and polypropylene (PP) based thermoplastic vulcanizates (TPVs). The electron treatment with various absorbed dose values showed a prominent effect on mechanical, rheological, and morphological characteristics of the PP/NR TPV. SEM and TEM studies confirmed that these TPVs can exist across the co-continuous or discrete phase morphology. The maximum set of mechanical properties (tensile strength of 15 MPa and elongation at break of more than 500 %) were obtained at an absorbed dose of 100 kGy for a 50/50 blend ratio of NR and PP without any addition of compatibilizer or chemicals. At higher absorbed dose values the degradation of polypropylene showed a negative impact on the mechanical properties of the TPVs. Depending on the morphology and the results of tensile test a structure-property co-relationship is drawn on the basis of common phenomenological understanding of the TPVs.
PBT/PC blends provide an excellent balance of chemical resistance, mechanical strength (especially at low temperature), and processability for a wide range of applications. Recently, appliance applications started to demand more sustainable, environmentally-friendly and green materials without sacrificing any properties for their new generation products. To respond to this market requirement, a high recycle content PBT/PC blend with excellent chemical resistance properties, good FR performance, and great mechanical properties was developed. The use of a high recycle based PBT/PC blend is the key to opening a new door to the more sustainable and green world for future appliance applications.
This work will focus on an approach to improve the impact toughness of poly (lactic acid) or PLA without compromising the biobased carbon content and compostability of PLA. Specifically, low-crystallinity and amorphous PHB copolymers were demonstrated to be very effective in improving the toughness of PLA at modest loading levels of 10-20 weight percent. This presentation will also compare the above approach with urethane, butadiene and acrylic impact modifiers along with the impact modification provided by other compostable polymers such as PBS and PBAT. Of particular significance is the extent of impact modification provided by an amorphous PHB copolymer (M4300 @ 10-20% loading) wherein the blend demonstrates a combination of mechanical properties that rival those of some engineering thermoplastics. Morphological considerations for the observed improvement in impact performance will also be highlighted.
Polylactic Acid (PLA) is the most widely available, renewable and compostable polymer with several unique features. However, PLA is poor in its ability to withstand elevated use temperatures above 55 °C. As such it is common practice to either compound PLA with additives that improve its heat deflection temperature or increase its crystallinity in mold or in an extra annealing step for use in injection molded applications. The objective of this research was to study the crystallization of three PLA grades and its effect on thermal properties including compostability. Crystallization was studied using DSC and Talc was used as a nucleating agent. Crystallinity was found to vary from 25% to 60% for the various grades. The PLA was converted into test bars and cutlery and its heat distortion temperature was tested before and after annealing. Additionally, the crystallized cutlery was sent to a local composting facility and was found to disintegrate within 4 weeks, which is much sooner than the requirements of the ASTM D6400 standard of 12 weeks.
In Mold Coating (IMC) has been applied to Sheet Molding Compound (SMC) as an environmentally friendly alternative to make the surface conductive; for subsequent electrostatic painting operations. Due to its successful application to exterior body panels made from compression molded SMC, the application of In Mold Coating for injection molded thermoplastic parts is being developed. In order to make the coating conductive, the filler used in IMC is carbon black (CB). However, the injection pressure needed to coat the part is significantly affected by the amount of CB in the coating material. Predicting injection pressures for IMC of thermoplastic parts is more critical than for IMC of SMC. To predict the coating pressures we need to measure the effect of CB on the IMC viscosity. In the present work, we studied the effect of CB on electrical conductivity and viscosity. The pressures needed for coating a typical IMC part with the required conductivity level are estimated.
In this study we have developed “dry-less pellets”, which absorbs less moisture and do not require additional drying prior to molding. The developing technique namely “Hot Air cooling System” involves coolinging the strands slowly with hot air on a metal conveyor. This study was carried out to clarify a relationship between moisture absorption fraction and crystalline structure of dry-less recycled poly(ethylene terephthalate) (RPET) pellets. Two diffent cooling systems of extrusion processes were performed including water cooling method and hot air cooling syatem. The effect of hot air cooling temperature on properties of RPET pellets was investigated. Karl Fischer moisture titration, differential scanning calorimetry (DSC) and density measurement were used to characterize the pellets to determine the structures of the dry-less pellets. From the results, we have succeeded for preparing the “dry-less pellets” by controlling the hot air cooling temperature condition in the extrusion process. The crystallization process of RPET pellets is an important characteristic for the “dry-less RPET pellets”.
Polymers are increasingly being used for engineering structures and medical devices because of their excellent corrosion resistance and low cost compared with metals. However, the lifetime of plastics used in severe environments is significantly reduced due to environmental stress cracking (ESC). Current understanding of ESC in polymers is mostly empirical. In this paper, a methodology for investigating ESC in polymers is presented. The proposed approach, based on the cohesive zone model (CZM), is capable to characterize the degradation in the fracture zone explicitly, independent from the bulk material. In our preliminary investigation, the fracture on an elastic-plastic material was simulated, and the results were compared to a published paper. The simulation outcome indicates that the CZM is an effective tool to study fracture propagation in polymers under ESC.
In the Beckers organization sustainability has become a very important topic. It is a broad topic and from here we have been deriving areas of focus for our sustainability program. One vital step towards the pursuit of sustainable development would involve an in-depth look into the carbon exposure of the organizations’ value chain and operation. The Beckers organization undertook this activity by completing a life cycle analysis of our 4 major paint products that are commonly used in the production of mobile consumer products. This investigation was part of an initiative that was take with the support of The Natural Step, a nonprofit organization that provides support to organization committed towards sustainable development. The life cycle analysis was conducted within defined boundary conditions and had revealed that various paint technologies appear to contribute to varied levels of equivalent CO2 emissions.
Injection molding of solid and foamed polypropylene/carbon fiber (PP-CF) composites with different carbon fiber contents (0-20 wt. %) was conducted. ~ 25% void fraction in the foamed composites was achieved using supercritical N2 as the environmentally benign physical blowing agent. The effects of foaming on the percolation threshold, through-plane electrical conductivity, permittivity and electromagnetic interference shielding effectiveness (EMI SE) were investigated. Compared to the solid composites, in addition to the reduced weight of the polymer matrix (25%), introduction of foaming lowered the electrical percolation threshold from 17 wt. % to 11 wt. %. The relationship between the structure and electrical properties was explained in terms of the changes in the fiber orientation and skin layer thickness. At 15 wt. % CF content, the foamed composites yielded an EMI SE of about 25 dB, significantly higher than that of the solid composite (13 dB) with the same CF content. In both solid and foamed composites, the dominant EM attenuation mechanism was found to be wave absorption not reflection. The results reveal the application of injection foam molding technology to manufacture lightweight conductive products with lower fiber content and enhanced EMI SE.
Compounding ground tire rubber (GTR) with thermoplastic polyolefins, such as polypropylene (PP), is a possible way to manufacture thermoplastic elastomers and also to recycle waste tires, thus solving a major environmental problem. The effect of ultrasonic treatment on the mechanical, rheological and morphological properties of PP and PP/GTR (ground tire rubber) blends in an ultrasonic single screw extruder (SSE) and an ultrasonic twin screw extruder (TSE) were investigated. PP and GTR was fixed at a ratio of 50:50. The treatment was carried out under amplitude of 5, 7.5 and 10 ?m, and at a flow rate of 2 lbs/hr. Pressure and ultrasonic power consumption were measured. Mechanical and rheological properties of untreated and ultrasonically treated PP indicated that TSE provided more degradation than in SSE. For 40 mesh blends from SSE, the mechanical properties improved with increasing ultrasonic amplitude. The viscosity indicated very little dependence on ultrasonic amplitude, which is evidence a formation of covalent bonds between PP and GTR. Viscosity of 140 mesh blends was lower than that of 40 mesh blends from both SSE and TSE, indicating a larger degree of degradation of blends with smaller rubber particle size. In addition, with smaller rubber particle size, much better elongation at break is obtained which indicates better adhesion between PP and GTR.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
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