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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Effect of Additives on the Structure and Properties of Wheat Straw-Polypropylene Composites
Natural fibers from agricultural activities have been emerged as alternative fillers in the thermoplastic industry. Crops such as wheat straw are renewable and low cost materials that combined with thermoplastics such as polypropylene provide engineering products with unique characteristics. Due to the wide range of thermoplastics and potential agricultural fillers the influence of additives in the systems is one of the points yet to be determined for different combinations of matrix and filler. In this study composites containing 30 wt-% of wheat straw (WS) fibers and polypropylene (PP) were prepared in a batch mixer. The individual effects of two coupling agents and a lubricant in the composites were investigated. Scanning electron microscopy (SEM) was used to examine the morphology of wheat straw particles and composites. The water absorption behavior and mechanical properties were assessed for those composites prepared. Results showed a strong interaction between filler and matrix in compositions containing coupling agent; differences were observed in the performance of the two coupling agents tested. Furthermore the lubricant used contributed to the water absorption of the composites.
Hybrid Bio-Based Composites from Nano-Reinforced Bio-Petro Polymer Blends & Natural Fibers
Natural fiber composites or biocomposites have recently gained much attention due to their low cost environmental friendliness and their potential to compete with glass-fiber composites. However the use of all-natural resins is limited due to performance concern and hence the blending bio-resins in petroleum resins has gained importance due to their improved toughness and environmental friendliness. Nevertheless addition of bio-resins generally compromises stiffness barrier and thermal properties. The enhancement of polymer stiffness and barrier properties with small concentrations of layered silicates is well established. With this context the paper presents the development and thermo-physical characterization of a hybrid composite material with increased environmental friendliness that can retain stiffness without sacrificing toughness barrier and thermal properties. Hybrid biocomposites were made from bio-based resins (blends of unsaturated polyester and epoxidized soya bean oil) reinforced with organo-nanoclays and natural fibers (unprocessed industrial hemp). Results show that an optimum material design that maximizes the synergy of the constituents is possible and provide an initial benchmark in identifying such balance.
Differentiated Compression Molding: A New Process Innovation Creates Dramatic Cost Savings & Product Improvements for Compression-Molded Applications
Long glass fibre thermoplastics (LGFT) used in compression moulded applications has grown dramatically due to metal replacement by composites and the derived benefits in both cost and weight savings. In order to make thin walled parts from higher viscosity thermoplastic materials as opposed to thermosetting resins machine producers have been challenged in terms of clamp size and tooling. In this paper a revolutionary new process called differentiated compression moulding (DCM) is described and compared with traditional compression moulding. Using new tool designs the process allows for reductions in press sizes of up to 70%. This in turn allows for significant cost savings in machine investment tooling and energy consumption. Larger projected areas and thinner walled investment tooling and energy consumption. Larger projected areas and thinner walled parts can be made on smaller machines. The paper discusses the physics and rheological conditions that allow for this innovation and a test case is compared to current technology.
Development of a Tool to Measure Bond-Line Read Through
The Automotive Composites Consortium Joining Working Group (ACCJWG) teamed with Visuol Technologies and EOS Technologies to develop a measurement system for quantifying the severity of “bond-line read-through” (BLRT). BLRT is a visual defect that can occur when two panels are bonded together. The measurement system is based on the ONDULO technology developed by Visuol Technologies. To develop the metric the ACCJWG provided Visuol Technologies a set of forty-eight panels with varying amounts of BLRT. Curvature maps for each of the panels were captured using the ONDULO technology. Visuol Technologies then used the in formation in the curvature maps to develop an algorithm for calculating a BLRT “score” that quantifies the severity of the defect. The algorithm first filters out any pixels in the curvature map below a certain magnitude. The remaining pixels are grouped by their proximity to one another to create discrete defects. Since there were many small defects found in the curvature maps a defect?s mean amplitude and aspect ratio are required to fall within certain thresholds to be included in the final score. The score for each individual defect is the product of its mean amplitude size and aspect ratio. The final BLRT score for a panel is a sum of the scores for each defect on the surface. Since the original algorithm was developed using panels made with continuous beads of adhesive the algorithm is being modified to properly assess other types of defects. For the set of panels used to develop the initial algorithm the score developed was shown to correlate well to the visual assessment of the panels. Furthermore since the metric is based on measured physical characteristics of the defects it provides a unique method for objectively quantifying the severity of BLRT defects.
Evaluating Extrusion Compression Molding for Imparting Better Surface Finish in Long Fiber Thermoplastics Using In-Mold Film Technology
Automotive applications of compression molded products with a thermoplastic matrix have been growing rapidly within the last few years as demonstrated by increased use in applications including front-ends bumper beams dashboards and under body shields. Long fiber thermoplastics (LFTs) have received much attention due to their processability by conventional technologies. However applications of LFT materials have been limited in external body parts that require a good surface finish. Painting LFT parts is rare and requires considerable equipment investment. Further painting is often associated with environmental concerns such as Volatile Organic Compounds (VOCs) and high energy consumption. This paper innovates the process of extrusion compression molding for long fiber thermoplastic parts by placing a film (with a thermoplastic olefin backing) in-mold that melt bonds to the LFT material. This results in a compression molded LFT part that has the nice surface finish required for exterior applications. In order to evaluate the process variables potentially contributing to the surface quality are identified and analyzed. A Design of Experiments is carried out to investigate thoroughly yet economically the effect of four process variables. Gloss chip resistance and adhesion of film to substrate are tested according to ASTM standards. These test results are used to evaluate the effect of the processing variables considered and to establish optimum operating parameters.
RTM Technology Improvement with Tool Surface Heating by Induction
With the goal of weight and cost reduction in the automotive industry the need for a technology able to produce highly structural composite parts in a short cycle time is very important. That's why RocTool adapted its Tool Surf ace Heating Technology to the RTM process. The inductive phenomena allows this technology to heat fast and cool down quickly the tool surface leading to many advantages for the RTM process such as : overall cycle time reduction filling time reduction and safer filling of the mould injection time reduction warpage reduction because of extraction of cold parts surface quality improvement.
Exfoliated Graphite Nanoplatelet - Vinyl Ester Nanocomposites
Recent research at Michigan State University has shown that it is possible to exfoliate natural graphite into platelets having thicknesses of less than 10nm and diameters of any size from sub-micron to 15 microns or greater. Since graphite is one of the stiffest materials found in nature (Young’s Modulus = 1060 GPa) having a modulus several times that of clay and also has excellent electrical and thermal conductivity the addition of these nanographite platelets to polymers can impart a combination of desirable mechanical electrical thermal and barrier properties to the resulting nanocomposite. We have investigated the addition of exfoliated graphite nanoplatelets (xGnP) to a vinyl ester resin to achieve a nanocomposite with an optimum combination of conductivity and mechanical properties. It was found that the flexural modulus increased with increasing the content of xGnP regardless of the dimensions of the particle. The flexural strength decreased with increases in the content of xGnP dependent on the size of xGnP. The impact strength of the nanocomposite reinforced with xGnP having a diameter about 1 micron (xGnP-1) increased compared to the nanocomposite reinforced with xGnP-15. The electrical impedance (resistivity) of the xGnP reinforced vinyl ester nanocomposite and particularly the percolation threshold depended strongly on the size of xGnP. The nanocomposite reinforced with xGnP-1 has a higher percolation threshold and resistivity compared to the one reinforced with xGnP-15. It will be shown that by blending xGnP-1 and xGnP-15 it is possible to obtain a combination of good mechanical properties as well as resistivity
Development & Thermo-Physical Properties of Bio-Based Polymer / Clay Nanocomposites
Bio-based resin systems obtained as blends of functionalized vegetable oils and petroleum based resins have been found to increase toughness of petroleum based resins and improve their environmental friendliness. Nevertheless this improvement in toughness generally compromises the stiffness of the resin system. Nano-scale layered silicate (nano-clay) polymer nanocomposites exhibit enhanced mechanical and physical properties at relatively low weight fractions of inclusions. The reported study shows that proper stiffness – toughness balance along with enhancement in many other physical properties can be obtained by incorporating nano-scale layered silicates in bio-blended polymers. Polymer nanocomposites with varying clay contents and varying bio-blend (epoxidized soya bean oil) in unsaturated polyester resins were manufactured. Tensile properties and moisture absorption properties were studied. Fracture surface morphologies and characterization of nanocomposites were performed using electron microscopy. The resulting bio-blended polymer nanocomposites exhibit promising results for use in structural applications.
Nano-Fibrillated High-Modulus Ductile (HMD) Technology in Environmentally Sustainable Xenoy iQ* Resins
Recently General Electric Plastics launched a series of High Modulus Ductile (HMD) products as an expansion to the Xenoy product line. In these HMD products a highly fibrillated nano network is combined with state of the art mineral filler technology allowing for retention of impact and tensile properties whilst increasing the modulus of molded articles. We have been successfully able to incorporate this technology in the Xenoy* (PC/PBT and PC/PET) resin which has resulted in superior chemical resistance low CTE excellent tensile strength fatigue and low temperature ductility. We will present a case study where HMD technology was combined with our environmentally sustainable low carbon footprint Xenoy iQ* resin offering excellent part performance lighter weight and increased first pass yield during processing.
Exfoliated Graphite Nanoplatelet (xGnP) / Polypropylene Nanocomposites
Graphite is an abundant natural mineral and one of the stiffest materials found in nature (Young's Modulus ~1060Gpa) with excellent electrical and thermal conductivity. Research underway at MSU on polymer matrices reinforced with new filler exfoliated graphite (~10nm thickness) has shown that nanoreinforcement concentrations of up to 10 vol% in thermosets and 25 vol% in thermoplastics are easy to achieve and appropriate processing can result in composites with the best mechanical thermal and electrical properties. Research is to explore the fabrication method and processing conditions via factorial design of experiments and how they influence the properties of exfoliated graphite nanoplatelet (xGnP)/PP nanocomposites. A significant development is a new compounding method i.e. premixing of xGnP and PP powder in isopropyl alcohol using sonication to disperse the xGnP by coating individual PP powder particles prior to compression molding. This premixing method is more effective than the widely used melt compounding method in terms of lowering the percolation threshold of thermoplastic nanocomposites (NC) and enhancing the probability that the large platelet morphology of xGnP can be preserved in the final composite. The flexural strength and modulus of pellet -type PP/xGnP-1NC was higher than that of powder-or flake-type PP/xGnP-1 NC. In the electrical conductivity study the percolation threshold of the flake and the pellet type PP is only 0.6 wt% of xGnP-1. This lower percolation threshold is due to network formation of xGnP on the surface of PP. The results of this study provide a fundamental understanding of how the processing and resulting distribution of xGnP within the final composite can affect the physical and mechanical properties of xGnP/PP nanocomposites.
Development and Build of the Ford Focus FCV Lightweight Carbon Fiber Decklid
Ford Motor Company contracted Multimatic to develop and supply a niche volume low investment cost and lightweight decklid for the Focus Fuel Cell Vehicle (FCV) program. An aluminum solution was considered by the program however dedicated stamping tools would have been required and thus was considered infeasible. A carbon fiber solution was proposed as it would offer low investment cost at very low weight however a fully production ready North American AEM Class A carbon composite closure had never been attempted at the time of this program. The decklid would not only be required to meet the Class A finish requirements but would also have to be fully engineered to accept all carry-over components and hardware including seals meet all production component engineering requirements and then be certified to meet the Production Part Approval Process (PPAP) requirements all while providing mass savings. This paper will describe the methodology used to conduct the decklid engineering and development which includes the design and CAE assessment prototype fabrication physical testing and production build. The decklid assemblies were manufactured using carbon fiber/epoxy prepreg materials and aramid honeycomb core materials and were autoclave cured using single-sided tooling. Having met all PPAP requirements the completed assemblies became the first North American OEM production carbon fiber decklids and were shipped to the Ford assembly site primed and ready for paint and final assembly. The final composite decklid assembly mass reduction was 60% compared to the baseline production Focus steel decklid resulting in a mass saving of approximately 6.3 kg.
Innovative Structural Thermoplastic Air Conditioning Roof Cover Door for Mass Transit Bus
This paper deals with the design and analysis of an air conditioning (AC) cover roof door of an articulated mass transit bus using advanced thermoplastic composites. Innovative thermoplastic composites materials and thermoforming processing technologies have been demonstrated to form an AC door that has an outer skin on thermoplastic polyolefin (TPO) and an inner rib-stiffened liner made of AZDEL SuperLite a glass mat polypropylene (PP) material. The thermoplastic AC door is approximately 40% lighter than the metal counterpart and can be readily molded in a mass-produce able cost-effective manner.
New Long Fiber Reinforced Plastics: A Single Pellet Solution with Enhanced Properties
Long fiber-reinforced (LFRT) thermoplastics are widely used in automotive and industrial markets and are frequently used in metal replacement applications. Common automotive uses include front-end modules instrument panel substrates battery trays sunroof beams mirror brackets and fuel rails. The LFRT composites offer exceptional mechanical performance high rigidity with outstanding strength and resistance to impact failures. More and more LFRT compounds are finding use in demanding structural applications and the industry is looking for added effects incorporated to these products such as a range of colors UV resistance flame retardancy and others. Currently these properties are incorporated using pellet blends of LFRT products with master-batches which restrict the product design freedom. We have developed a new technology that provides a “single pellet solution” to impart multiple effects in LFRT products breaking the limitation of dry blending of colorants additives flame retardants or other properties. This paper reviews three distinct product families that deliver single pellet solutions with enhanced color consistency robust non-brominated flame retardancy superior UV and weathering resistance without compromising the balance between stiffness and impact offered by LFRT products. The enhancement in design freedom as seen in product properties improvement in surface finish of molded parts utilizing a heat-cool process and application development are discussed in detail.
Pedestrian Safety Validation of a High-Performance thermoPlastic Composite Hood
GE Plastics pioneered the use of thermoplastics for vertical body panel applications (such as fenders door skins and lift-gate skins) and now a thermoplastic composite material for horizontal automotive body panel applications (such as hoods roofs and trunk lids) is underdevelopment. One of the challenges to be met by a new material for hood applications is to meet the new requirements for pedestrian protection that have been introduced in Europe and Japan. As one of the key technology developments carried out for the Hyundai HED -4 QarmaQ advanced technology demonstration vehicle developed by Hyundai and GE Plastics a new hood design was created for manufacture with the HPPC sandwich. Semi-production compression-molding tooling was built and parts were produced to enable a series of head-impact tests to be completed. The test results indicated that the energy absorption characteristics of HPPC allow such a hood to meet the pedestrian safety requirements without the need for extra intrusion into the engine bay.
Injection Molded Long Glass Fibre Polypropylene Composites for Automotive Applications
The introduction of long-fibre reinforcements into the matrices of polymeric materials has lead to the development and introduction of many engineered solutions for applications which had once solely been the province of metal designs. The combination of long glass fibre with a highly economical and processable polymer such as polypropylene has significant advantages for both the designer in terms of weight reduction design flexibility and cost savings as well as to the moulder in terms of efficiency and productivity. The utility of this polymeric solution is further enhanced when it can be combined with unique bonding materials to allow it to be bonded with metal for structural enhancement. This paper will review the development of a long glass fibre polypropylene polymer in concert with the development of a unique adhesive solution to form a polymer- metal hybrid solution. This utility and effectiveness of this solution will be demonstrated in the structural modular application of an automotive front end carrier.
Investigation of Sheet Molding Compound Fabricated from Soy-Based & Petroleum-Based Resins
Plaques fabricated from sheet molding compound (SMC) with soy-based resins in both glass fiber-reinforced and carbon fiber-reinforced versions are compared with the equivalent SMC with petroleum-based resins. Since soy-based resins are less sensitive to the price of petroleum than petroleum-based resins these materials represent potential cost savings to the automotive industry if the price of petroleum continues to increase as well as providing opportunities to decrease overall carbon dioxide emissions. Soy beans are also a renewable resource. Material thermal properties including dynamic mechanical analysis (DMA) and coefficient of linear thermal expansion (CLTE) are evaluated as are mechanical properties including tensile and compressive characterizations. The effect of humidity aging was evaluated by moisture absorption as well as residual tensile and compressive properties. For as-received properties the glass-reinforced version of the soy-based material is found to be similar in performance to the petroleum-based material. However the carbon-reinforced soy resin material has lower mechanical properties than the petroleum-based SMC probably due to a lack of fiber-matrix adhesion. In humidity aging the petroleum based materials absorbed less moisture than the soy-based although the relative property loss caused by humidity aging was similar for the petroleum-based and the soy-based materials.
Composite Design Innovations: The Nissan Trunk Divider Hybrid Panel
The 2007 redesigned Nissan Sentra includes a unique trunk divider panel system that utilizes several different composite materials. The multi-piece (hybrid) main panel consists of a compression molded SMC ‘inner’ panel an in-mold carpeted flax fiber-filled polypropylene ‘outer’ panel integral glass-filled grocery hooks and two-way latching mechanism. The divider panel is mounted to the vehicle via a compression molded SMC ‘upper’ panel that mounts to the vehicle’s sheet metal package shelf as well as two glass-filled polypropylene hinges that mount to the vehicle’s trunk floor. To add versatility the panel can be used in a closed position to form two trunk compartments folded flat to the floor to transport wet or muddy items or removed entirely from the vehicle for clean-up or outside use. This system meets all required cost mass performance / functionality and quality targets. This presentation will focus on the design development materials testing and manufacturing methods applied to bring this ‘hybrid’ composite system to market.
Designing with Thermoset Composites
Automotive OEMs cite the difficulty in modeling composites as a significant barrier to their wider use. Unlike metals whose properties are isotropic composites have behavior that may be more difficult to model and to predict. Accurate materials characterization is increasingly important in allowing engineers to create the most cost-effective and reliable designs. In addition as carmakers make greater use of computer-aided tools detailed characterization becomes a basic requirement to consider a material for a particular application. This paper surveys some of the tools available for optimizing high volume automotive designs in thermoset composites namely sheet molding compound (SMC) and describes the range of resources from qualitative design guides to quantitative prediction models.
Plant Trials for Powder Priming of SMC
Based on the information generated at GM R&D Center six SMC formulations were developed and produced by SMC suppliers and subsequently molded into automotive body panels for powder primer application readiness tests. The panels were evaluated in the lab for shrinkage moisture absorption adhesion to the conductive coating and powder application. Based on the results all six formulations were approved for plant trials. The trials took place in Shreveport and Lordstown assembly plants. It was noted that the use of infrared heating to bake the powder is detrimental to SMC as it causes rapid heating of SMC substrate resulting in a high flux of moisture in a short period of time. It was also learned that the experimental conductive coating improves the powder prime capability of SMC and allows powder priming after an extended exposure to the plant environment.
Reduction of Styrene Evolution from Thermoset Polyester Resin Composites
The incomplete reaction of polyester resins in fiber reinforced composites results in residual styrene monomer that slowly evolves from the polymer matrix over many years. In cars and trucks where extensive use of such composites are open to the interior of the passenger compartment the odor of styrene can become strong enough to be objectionable to the vehicle occupants. A design goal for the development of coupe sports car which makes extensive use of polyester SMC and liquid molded composites was to assure that the styrene concentration in the passenger compartment is not offensive. Simple test methods were devised to assess styrene evolution at the material component and vehicle levels. Through the systematic study of resin paste formulations process modifications coatings and part design features this design goal was met before the launch of the vehicle.
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