SPE Library

Wood composites based on recycled polypropylene (PP) were fabricated by melt processing. Different formulations involving two different types of coupling agents two different types of reactive additives and an impact modifier (IM) were used. The reinforcements were in the form of wood sawdust. The mechanical performance of the resulting composites was evaluated before and after conditioning in water for 1 and 7 days. The composites show superior mechanical properties when compared with the pristine matrix and resist humidity very well. The results also demonstrate the effect of formulations on the performance of the recycled composites.

Natural fiber-reinforced composites are increasingly being used in applications in the automotive furniture or building industry. The processing and physical properties of these composite materials are the very important parameters in respect to the design layout and product guaranty. This paper presents the results of the study of processing and physical properties of environmentally friendly wood fiber reinforced poly(lactic acid) (PLA) composites that were produced by a micro-compounding molding system. Wood fiber-reinforced polypropylene (PP) composites were also processed and compared to PLA/wood fiber composites. The mechanical thermal-mechanical and morphological properties of these composites have been studied. PLA/wood fiber composites have mechanical properties of sufficient magnitude to compare with conventional thermoplastic composites. The tensile and flexural properties of the PLA/wood fiber composites were significantly higher when compared with the virgin resin. The addition of 20 wt % of wood fibers in PLA/wood fiber composite improved the flexural strength of PLA by 19 % the flexural modulus by 115 % and the tensile strength and tensile modulus by 5 wt % and 77 % respectively. The flexural modulus (8.9 GPa) of the PLA/wood fiber composite (30 wt % fiber content) was comparable to that of traditional (i.e. polypropylene/wood fiber) composites (3.4 GPa). Incorporation of the wood fibers in PLA resulted in a considerable increase of the storage modulus (stiffness) and a decrease in the tan delta values. The addition of the maleated polypropylene coupling agent (MAPP) improved the flexural and Izod impact properties of the wood fiber reinforced composites. The morphology as indicated by scanning electron microscopy (SEM) showed good dispersion of wood fiber in the PLA matrix. Microstructure studies also indicated a significant interfacial bonding between the matrix and the wood fibers. The specific performance evidenced by the wood fiber reinforced PL

Blends of polylactide with thermoplastic starch are prepared using a one-step extrusion process. These materials, subsequently processed via injection molding, possess interesting properties. The tensile properties in these samples are related to the composition of the blends and also to the glycerol plasticizer content in the thermoplastic starch. These materials possess an advantage for the environment since they are fully biodegradable and are derived principally from renewable sources.

The effects of chain extension and branching on the properties of nanocomposites produced from recycled poly (ethylene-terephthalate) and organically modified clay were investigated. As the chain extension/branching agent, maleic anhydride (MA) and pyromellitic dianhydride (PMDA) were used. Both MA and PMDA improved the mechanical properties of the nanocomposite owing to the branching and chain extending effects that increase the molecular weight. However, PMDA gave better results at lower content.

Recent advancements in the field of polyolefin resins in the area of PP+PE copolymers, impact co-polymers, and homopolymers have allowed for the creation of a new class of thermoplastic foam products. These new products are capable of improved performance due to the advancements that have been made in the area of polyolefin resin catalyst systems. These new Metallocene catalysts are being used to create resins with improved mechanical properties that otherwise were not available using the traditional Ziegler- Natta catalyst systems currently being used to produce a majority of the thermoplastic materials available today.This paper describes these recent advancements and how they allow for improved properties in the area of moldable expanded bead foam used in the automotive, marine and recreational occupant safety and cushioning system designs. This technology allows for improvements in the mechanical properties of these thermoplastic foam components, while allowing them to be produced on existing processing equipment. This paper will also compare these advancements to those currently being used, and demonstrate how improvements in performance, system integration, and cost can be realized. Compliance to existing and new environmental substance regulations and restrictions are also addressed.

Blends of Virgin and Recycled Nitrile Rubber within a blend ratio of 10-30 %wt recycled NBR were studied. Reference was made to mechanical and physical properties. Results obtained indicate that a maximum percentage of 20%wt recycled rubber can be added to a NBR formulation without diminishing considerably final properties, since higher percentages promote a premature vulcanization. Concerning chemical resistance, an excellent oil resistance and a very low resistance to polar solvents were obtained for all formulations.

Nanocomposites based on biodegradable polycaprolactone (PCL) and mica clay organically modified with L-arginine were prepared through solvent blending. Their properties were analyzed with TGA, DSC, and tensile testing. The addition of the organically modified clay caused an increase in properties, but at large incorporation, properties began to decrease. Samples of 3%, 5% and 10% organically modified clay were compared to pure PCL.

Thermoplastic olefin (TPO) is currently the material of choice for automotive bumpers and fascias. The part is generally painted with thermoset paint after molding. Unless removed, this paint layer creates problems during recycling of rejected parts. It causes a change in the processing characteristics and properties. The techniques used for removing the paint layer from the TPO create additional steps in the process and adds extra costs. The concept studied is the possible reuse of painted regrind by reducing the paint particle size in an injection molding process; possibly eliminating the need for paint removal in some recycling applications.A modified progressive double row grater screw was used to reduce the particle size of the paint flakes. The physical properties of these material blends are compared to similar blends obtained using a general-purpose screw. It is shown that reducing the paint flake size has a marginal effect on mechanical properties. However, the surface finish is greatly enhanced when the paint flake size is reduced.

This paper reports about the comparative behaviour, regarding PET, of biodegradable biopolymers such as PCL, PLA and PHBcoV and their nanobiocomposites, in terms of thermal and retorting resistance (thermal humid processes) and oxygen, water vapour and aroma barrier by means of time-resolved synchrotron radiation, FT-IR and permeation methods.

Recent reports have shown the fibers made from polyp- phylenebenzobisoxazole show a significant reduction in properties after relatively mild exposure to environmental conditions. This paper discusses potential mechanisms responsible for the degradation and reports results on degradation of fiber properties due to various environmental exposure conditions.

This paper presents an investigation on the design and optimization of plastic milk crates using the finite element method (FEM) with the aim of reducing the mass and simplifying the shape of a standard milk crate. The paper also explores the possibility of manufacturing such milk crates using recycled High Density Polyethylene (HDPE) instead of virgin HDPE or virgin polypropylene (PP) to make it more cost effective.

Biodegradable blends of amorphous Poly(lactic acid) (PLA) and polycaprolactone (PCL) have been developed by melt blending. The morphology of these materials was characterized by means of WAXD and TEM, showing that silicate layers of the kaolinite (chemically modified kaolinite) were intercalated and evenly distributed within the biodegradable matrix. Mechanical, thermal and gas barrier properties of the different blends and nanocomposites were studied and the effect of clay addition on the above-mentioned properties was evaluated.

Responding to environmental, sustainability, business and market needs, DuPont has recently commercialized a new polymer platform Sorona®. Sorona® polymer is produced from fiber-grade 1,3- propanediol (PDO). It is a linear semi-crystalline polymer with a melting temperature of ~228°C and a glass transition temperature of about 50°C. (See Figure 1)

A wide variety of bioactive composites for bone regeneration have been developed and investigated over the last decades. In order to promote bioactivity, certain types of glasses, ceramics and minerals are incorporated into biodegradable or biostable polymers. In this study, several established and novel fillers such as calcium phosphates, silicates and glasses were screened for bioactivity. Promising candidates were then incorporated into two different grades of poly-?-caprolactone by solution mixing, and testing was conducted in a simulated body fluid to determine in vitro bioactivity. At different time periods the exposed samples were characterized by SEM, EDX and FTIR microscopy in order to investigate the formation of the apatite layer needed for bone ingrowth. The screening results of this work produced suitable polymer/filler combinations for further in vitro and in vivo testing in different types of tissue engineering applications.

Biobased neat unsaturated polyester materials containing epoxidized methyl soyate (EMS) and their clay nanocomposites were processed with cobalt naphthenate as a promoter and 2-butanone peroxide as an initiator. A certain amount of unsaturated polyester resin (UPE) was replaced by EMS. The combination of the UPE and EMS resulted in an excellent combination, to a new biobased thermoset material showing relatively high elastic modulus and the constant glass transition temperature with up to 25 wt.% replacements with EMS. Izod impact strength was almost constant while changing the amount of EMS and adding clay nanoplatelets.

Three types of polylactide (PLA) composites, namely, PLA/nanoclay, PLA/core-shell rubber, and PLA/nanoclay/ core-shell rubber were melt compounded via a co-rotating twin-screw extruder. The effects of two types of organically modified nanoclay (i.e., Cloisite®30B and 20A), two types of core-shell rubber (i.e., Paraloid EXL2330 and EXL2314), and the combination of nanoclay and rubber on the mechanical properties of the composites were investigated. In comparison with pure PLA, both types of PLA/5wt% nanoclay composites showed an increased modulus, a slightly reduced tensile strength, a similar impact strength, and a significantly reduced strain at break. PLA/EXL2330 composites with a rubber loading level of 10wt% or higher exhibited much higher impact strength but lower modulus and strength when compared to pure PLA. The simultaneous addition of 5wt% nanoclay (Cloisite®30B) and 20wt% EXL2330 resulted in a PLA composite with a 134% increase in impact strength, a 6% increase in strain at break, a similar modulus, and a 28% reduction in tensile strength as compared to pure PLA.

Four case studies are presented to illustrate environmental stress cracking (ESC) within automotive components. ESC is a very important mode of plastic component failure. The presented cases illustrate how the failure analysis process was used to identify the failure mechanism as well as the primary factors responsible for the failures. The four cases depict representative automotive failures involving varied designs and service conditions.

Polymeric and composite materials from plant derived fiber (Natural/Bio-fiber) and crop-derived plastics (Bio-plastic) are novel materials of the 21st century and have the potential to be of great importance to the materials world, not only as a solution to growing environmental threat but also as a solution to alleviating the uncertainty of petroleum supply. As this new generation of biobased polymers enters the commercial market, success in competing with established petroleum based polymers will depend on their performance, properties and cost as determined primarily in the commercial marketplace. While environmental consciousness continues to grow, and some governmental programs have been established to assist with the entrée of biobased materials into the marketplace. E.g., the US Research and Development Act of 2000 along with Presidential Executive Orders 13134 & 13104 and the “Farm Bill” signed by President Bush on May 13, 2002, have a goal of achieving a performance/cost ratio competitive with petroleum-based polymers for value-added applications. The technology road map for plant/crop-based renewable resources 2020, sponsored by the U.S. Department of Agriculture (USDA) and the U.S. Department of Energy (DOE), has set a goal of increasing the utilization of basic chemicals from biobased renewable resources of 10% by 2020, and further increase to 50% by 2050.While the chemistry, reaction pathways and processing steps to producing biobased chemicals and polymers are relatively straight forward, it is the use of these materials in high performance, value-added applications that will be critically important to achieve sustainability and economic viability. The most promising path to achieve sustainability and economic viability is through the addition of biofibers to biobased polymers to produce biocomposites. Research underway in the Composite Materials and Structures Center at Michigan State University and other Universities has been directed at defining, de

It has been found that some thermoplastic systems survive accelerated UV weathering but fail in true environmental conditions. This is because quartz filters pass artificially high levels of 275 nm - 340 nm light, but artificially lower levels of longer wavelengths. For systems that are more reactive to longer wavelengths, the accelerated exposure tests provide false assurances of true weatherability. A specific example of this phenomenon occurring within polypropylene will be shown and discussed in detail.

This work probes a hypothesis for initiation of environmental stress cracking (ESCR) based on a thermodynamic criterion for localized stress induced swelling. The threshold metric involves observation of solid-vapor surface energy and contact angle of a liquid on a loaded polymer substrate and thus inference of solidliquid interfacial surface energy with respect to substrate stress. The intent is to develop a screening technique for ESCR that is not limited by the kinetics of the crazing event.