Polymer Engineering

Standard fused filament fabrication (FFF)-based 3-D printers fabricate parts from thermopolymers, such as polylactic acid (PLA). A new range of metal based PLA composites are available providing a novel range of potential engineering materials for such 3-D printers. Currently, limited material data, specifically thermal property characterization is available on these composites. As a result, the application of these materials into functional engineered systems is not possible. This study aims to fill the knowledge gap by quantifying the thermal properties of copperFill, bronzeFill, magnetic iron PLA, and stainless steel PLA composites and provide insight into the technical considerations of FFF composite 3-D printing. Specifically, in this study the correlation of the composite microstructure and printing parameters are explored and the results of thermal conductivity analysis as a function of printed matrix properties are provided. Considering the relative deviation from the filament raw bulk analysis, the results show the printing operation significantly impacts the resultant component density. Experimentally collected thermal conductivity values, however, do not correlate to the theoretical models in the literature and more rigorous quantitative exercises are required to determine true percent porosity to accurately model the effect of air pore volume fraction on thermal conductivity. Despite this limitation, the thermal conductivity values provided can be used to engineer thermal conductivity into 3-D printed parts with these PLA-based composites. Finally, several high-value applications of such 3-D printed materials that look metallic, but have low thermal conductivity are reviewed.

In order to assist researchers explore the full potential of distributed recycling of post-consumer polymer waste, this article describes a recyclebot, which is a waste plastic extruder capable of making commercial quality 3-D printing filament. The device design takes advantage of both the open source hardware methodology and the paradigm developed by the open source self-replicating rapid prototyper (RepRap) 3-D printer community. Specifically, this paper describes the design, fabrication and operation of a RepRapable Recyclebot, which refers to the Recyclebot's ability to provide the filament needed to largely replicate the parts for the Recyclebot on any type of RepRap 3-D printer. The device costs less than $700 in mate rials and can be fabricated in about 24 h. Filament is produced at 0.4 kg/h using 0.24 kWh/kg with a diameter ±4.6%. Thus, filament can be manufactured from commercial pellets for <22% of commercial filament costs. In addition, it can fabricate recycled waste plastic into filament for 2.5 cents/kg, which is <1000X commercial filament costs. The system can fabricate filament from polymers with extrusion temperatures <250 °C and is thus capable of manufacturing custom filament over a wide range of thermopolymers and composites for material science studies of new materials and recyclability studies, as well as research on novel applications of fused filament based 3-D printing.

Advanced modulation formats can enable >40 Gb/s data rates in waveguide-based optical interconnects without the need for high-specification optoelectronic components. Record 56Gb/s PAM-4 data transmission is demonstrated over a 1 m-long multimode polymer waveguide.

The rheological and thermokinetic aspects of the cure of epoxy based composite laminates are analyzed by means of a computer program developed using the heat transfer and heat generating characteristics of a polymerizable system. In particular, the temperature and degree of cure influence on the resin viscosity have been first considered, then the temperature profiles, calculated according to an appropriate kinetic and heat transfer modeling, have been used to predict the corresponding viscosity profiles. Molecular and thermocalorimetric parameters are used for the prediction of the theoretical chemorheological behavior. Commercial epoxy systems commonly used in the preparation of carbon fiber laminates have been characterized by Differential Scanning Calorimetry (DSC) and dynamic viscosity measurements and the results are compared with the theoretically predicted values.

The transport phenomena across polymeric membrane may be enhanced by applying various strengths inside or outside the system. Recently, polymer inclusion membrane (PIM) has been considered one of the most popular methods that acts as a sink for the contaminant and immobilizes it. In the literature, there is no report about how to achieve the synthesis of multi-layer PIMs. In this paper, an improvement of a novel category of membrane without carrier for performing ion separation is reported. Different membranes were elaborated from binary mixtures of polymers, cellulose triacetate (CTA), polymethyl methacrylate (PMMA) and polyvinyl chloride (PVC) using 2-nitrophenyl octyle-ether (NPOE) as plasticizer and carrier in the same time, in order to increase specific interactions between the different polymers. The membranes (Polymer 1– NPOE – Polymer 2) were synthesized by phase inversion method modified by changing the procedure of a plasticizer/carrier addition and characterized by FTIR, ...

Fumed silica dispersions in mineral or silicone oil are used to fill fiber-optic cables to prevent macro-bending of the fibers and to provide environmental protection. Adequate control of the rheology is essential for the effectiveness of the filling compounds: the materials must be sufficiently viscous to minimize stresses on the fibers but have considerable elasticity so as not to drip with time or temperature. The effects of shear history, aging, temperature, and water contamination on the rheological properties of two commercially available systems are studied using steady and dynamic measurements. The results are interpreted in terms of the microstructure resulting from the aggregation of submicron silica particles and their interactions with different solvents.

The presence of additives influences the state of segregation of filler particles in the polymer matrix which in turn controls the electrical and mechanical properties of poly(vinyl chloride)-copper composites. The liquid plasticizer seems to form a coating on the filler surface which introduces quasirandomness in the segregated network. In accordance with the mathematical model proposed earlier, the strength properties were found to be proportional to dm−½ where dm is the mean free path between the filler particles. Calculations of dm were based on two different models, one for segregated network (unplasticized and low plasticized composites) and the other for quasi-random distribution of filler particles (plasticized composites). Extruded samples in general show more randomness in the filler distribution than the compression molded samples.

The present study deals with preparation and swelling properties of micrometer-sized poly(N-isopropylacrylamide) (PNIPAM) hydrogel particles. Aqueous precipitation polymerization of NIPAM with N,N 0 -methylenebisacrylamide (MBAAm) was performed with varying electrolyte concentrations in the polymerization media. Sodium chloride was used as an electrolyte. According to the particle size analysis by transmission electron microscope, the particle size increased in the range of 0.55 to 1.60 mm with an increase in the electrolyte concentration up to 1.6 wt %. The concentration is based on the NIPAM monomer weight. Dynamic light scattering data showed that swelling ratio of PNIPAM hydrogel particles in water varied from 10 to 40 as the electrolyte concentration at particle preparation increased from 0 to 1.6 wt %. Time-course analysis of particle size showed that an increase in particle size would be caused by aggregation of smaller particles. In conclusion, micrometer-sized PNIPAM particles with high swelling capacity can be obtained by the addition of an electrolyte in polymerization media.

A new experimental technique for studying the dynamics of bubble growth in thermoplastics using scanning electron microscopy is developed. The influence of temperature, saturation pressure, molecular weight, and the nature of physical blowing agent are investigated. The experimental results show that the above process variables control the growth of foams during processing. The existing Newtonian model for the growth of a single bubble in an infinite amount of polymer has been modified to account for the non-Newtonian effects by modeling the polymer as a power law fluid. The experimental data has been compared with the appropriate viscoelastic cell model which considers the growth of closely spaced spherical bubbles during the foaming process. The simulation results indicate that the predictions of the cell model are in qualitative agreement with the trends of the experimental data and the quantitative agreement is reasonable. The cell model also gives an equilibrium radius which agrees with the experimental data. Other viscous models do not predict the equilibrium radius of the bubble and underpredict the experimental data.

Microphase-separated poly(styrene-b-ethylene-co-butyleneb-styrene) copolymers of different molecular weights with polystyrene (PS) volume fraction / 5 0.30 are investigated. Linear dynamic viscoelastic data reveal the blocking effect of the ordered PS microdomains, which produces a predominantly elastic response at low frequencies, associated with a mechanical relaxation. These results are correlated with tack and extrusion flow measurements, which involve polymer/metal adhesion processes. Nonlinearity implied in some experiments alters the ordered morphology of low molecular weight samples producing a viscous dominant behavior. Dissipation is reflected in viscous-like adhesion and lack of viscoplastic response in extrusion flow experiments. For the highest molecular sample, only a rubbery or entangled state (G 0 > G 00 and G 0 > 10 5 Pa) is observed in the linear viscoleastic regime. This is associated with the lack of adhesion seen in both, probe tack experiments and capillary flow measurements. This lack of adhesion gives rise to a plug-flow as the polymer slips in the capillary wall.

Although the environmental benefits of recycling plastics are well established and most geographic locations within the U.S. offer some plastic recycling, recycling rates are often low. Low recycling rates are often observed in conventional centralized recycling plants due to the challenge of collection and transportation for high-volume low-weight polymers. The recycling rates decline further when low population density, rural and relatively isolated communities are investigated because of the distance to recycling centers makes recycling difficult and both economically and energetically inefficient. The recent development of a class of open source hardware tools (e.g. RecycleBots) able to convert post-consumer plastic waste to polymer filament for 3-D printing offer a means to increase recycling rates by enabling distributed recycling. In addition, to reducing the amount of plastic disposed of in landfills, distributed recycling may also provide low-income families a means to supp...

Linear viscoelastic, steady shear behaviors, and morphologies of starch formate/poly(e-caprolactone) (PCL) blends, compatibilized by oligomers and obtained by reactive extrusion, have been investigated as a function of formic acid (FA)/starch ratio, nature, and molecular weight of the oligomer. The rheological properties of these blends have been compared with those of a commercial starch-based thermoplastic, namely Mater-Bi 1 ZF03UA. In presence of FA, starch is destructured to starch formate and oligomers are used as plasticizers. The linear viscoelastic response of blends is quite similar to that of nanocomposite materials: the low frequency behavior is attributed to a percolated network of destructured starch particles, and the high frequency behavior is that of the polymer matrix. The viscosity curve presents a profile characterized by two plateau regions, at low and high shear rates. The plateau region at low shear rates corresponds to the viscous response of the blend while that observed at high shear rates can be attributed to the PCL matrix. The compatibilization is enhanced in the presence of starch formate and increases with increasing the oligomer molecular weight. The use of PCL oligomer was shown to improve this compatibilization effect.

Two kinds of polyesters containing 2-pyrone-4,6-dicarboxylic acid (PDC) moieties in poly(L-lactic acid) (PLLA) and poly(butylene succinate) (PBS) main chains were for the first time employed as an additive to PLLA for improvement of the mechanical properties. Solution casting of a mixture of PLLA and PDC polyesters provided the blend films, which were comprehensively characterized by thermal analyses, tensile measurements, and crystallinity evaluation. Differential scanning calorimetry measurements revealed that PDC incorporation into polymer main chain dramatically improves the miscibility with PLLA. PDC-incorporated PBS showed better miscibility than PDC-incorporated PLLA. Optical microscopy measurements also suggested the superior orientation of PDC-incorporated PBS over PDC-incorporated PLLA in the blend films. The fracture strain of the blend films could be linearly increased by a draw ratio in the region of low PDC polyester content. On the contrary, the fracture strain decreased at high PDC polyester content due to the restricted strain caused by the strong dipolar interactions between PDC moieties. Elongation at break was significantly varied as a function of PDC polyester content, whereas tensile modulus was almost independent of the additive content and draw ratios. It is concluded that the blend films containing <10 wt % of PDC-incorporated PBS as an additive show the best tensile property.

In this research the variation of mechanical and rheological properties of the composite as a function of different processing parameters and ethylene propylene diene monomer (EPDM) rubber content was studied. The optimum amount of dicumyl peroxide (DCP) to achieve the highest percentage of grafting of maleic anhydride to EPDM was obtained by Fourier transform infrared (FTIR) spectroscopy. In general, immiscibility between nylon 66 and EPDM, and their high interfacial tension makes their blending difficult. Maleic anhydride was grafted to EPDM to reduce interfacial tension between two phases. Also the blends were prepared at highest possible speed of mixing (screw speed in extrusion) and lowest temperature to reach a well mixed sample which can be seen in scanning electron microscopy (SEM) images and impact strength results. Dynamic mechanical thermal analysis (DMTA) tests were conducted to evaluate the miscibility of the components and to measure the glass transition temperature of...

Biocompatible poly(vinyl alcohol)/poly (vinylpyrrolidone) iodine/poly(ethylene glycol) fibers containing (hydroxypropyl)methyl cellulose (HPMC) and aloe vera were successfully prepared by electrospinning their aqueous solution. Aloe vera which is known to be effective in the treatment of various wounds was added to the polymer solution. HPMC was added to the system as the water retention agent. The hybrid fiber mats were subjected to detailed analysis using a differential scanning calorimeter, a scanning electron microscope (SEM), and a Fourier transform infrared spectrometer. Images obtained from the SEM showed that the polymer fibers were linear, homogenous, and contained no beading. The fiber diameters ranged between 100 and 900 nm. It was seen that the electrospun mats obtained could potentially be used as a material for dressing wounds. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

In this work, graphene was used as a filler for banyan aerial root fibers
reinforced epoxy composites at various compositions. The synergetic effect of graphene and banyan fibers, on the physical and mechanical characteristics of the epoxy thermoset, was studied. The mechanical tests, hardness, water absorption behavior and morphology of the composites were studied. Significant improvement in tensile strength, flexural strength, shore D hardness and substantial reduction in the percentage of water absorption was observed. This paper also discusses the ideal proportion of banyan fibers with graphene powder for the development of the improved epoxy composites. The optimum concentration of the composites was observed at 4% of graphene powder in the 40% banyan fiber-reinforced hybrid epoxy composites. From the results, it is proved that graphene combined with 40% banyan fiber-reinforced epoxy hybrid composites will efficiently improve the strength of the composites.

The thermoplastic polymer blends of commercial interest generally need a phase compatibilization to reduce the interfacial tension, to stabilize the morphology, and to increment the interfacial adhesion. This work deals with the compatibilization of PP/PS blends by addition of a tailor-made copolymer, which is prepared from the pure homopolymers by a Friedel-Crafts reaction. This addition compatibilization process comes out as an economic alternative applicable to the recycling of mixed plastics from urban and industrial wastes. The influence of compatibilizer concentration and blending time on the emulsifying effect, morphology, and mechanical properties of the resulting blends are analyzed. The compatibilization process effectiveness is assessed through the improvement in phase adhesion, emulsification and ductility of the compatibilized with respect to the physical blends. An increase of three times in ductility is achieved using very low compatibilizer concentrations (0.5-0.7 wt%). No appreciable detriment in yield strength or modulus is observed in these compatibilized blends. POLYM. ENG. SCI., 46:329 -336, 2006.

The dynamic mechanical properties in terms of the storage modulus E′, loss modulus E″, and the loss tangent δ has been studied for highly filled magnetic polymer composites. The effect of surface treatment on the relaxation spectra has been clearly elucidated and quantitative values indicating the extent of polymer–filler interactions have been given. Various models have been tested for describing the viscoelastic behavior of such highly filled systems. The Wiechert model using a single-arm with a Cole–Cole parameter has been shown to effectively fit the Argand diagram in the case of the present highly filled systems

Presents rheological data on a number of polymers, making use of the master curve approach to determine unified curves for each generic type of polymer. The text offers a step-by-step procedure for developing a speadsheet computer program to obtain accurate thermoplastic rheograms at any tempertature without using sophisticated rheometres. It includes possible correlations of melt flow index with various parameters involved in polymer manufacture, product fabrication and property evaluation.

Review
This book offers an interesting, practical approach to the rheology and processing parameters of thermoplastic materials. . . This book is recommended for engineers and processors who may benefit from the use of the spreadsheet program to predict the behavior of thermoplastic materials as a function of processing parameters.
---Polymer News

One of the major problems in the plastic injection process of thin wall parts is warpage. In addition, the increase demand on smaller parts with reducing thickness has posed a great challenge to product design engineers, mold designers as well as manufacturing engineers. Studies on the significant factors that influenced warpage on general plastic parts had been conducted by many researches, however studies on warpage of ultra-thin parts are still lacking. This paper reports on the investigation of warpage on ultra-thin shell part of dimension 50mm x 40mm x 5mm and thickness 0.3mm using a three plate mold with a pin point gating system. Experiments were simulated using Autodesk Moldflow Insight (AMI) and warpage of the ultra-thin shell part was evaluated with and without considering the differences effect on mold temperature (core and cavity plates). Thermoplastic Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS) was used as the plastic material and Taguchi method was adopted to establish the optimum parameters of the injection molding process. Finally the results were analyzed statistically using ANOVA to obtain the most significant factors affecting the warpage. Results showed that the mold temperature of cavity and core plates are the most significant factor affecting the warpage in ultra-thin shell part while the temperature difference on the core and cavity plates was not significant.

In many applications, polymer materials undergo a large variety of mechanical loading conditions, wherein the influences of temperature and strain rate are of prime importance. Mahieux and Reifsnider [Mahieux CA, Reifsnider KL. Polymer 2001;42:3281. [19]] have proposed a statistical model to describe the stiffness variation of polymers over a wide range of temperatures. However, this model does not consider any frequency/strain rate dependence of the stiffness modulus. Starting from this consideration, we propose here to transform this latter model into a robust physically based model for the prediction of the stiffness modulus for a wide range of temperatures and frequencies/strain rates. This new formulation has been successfully validated for two amorphous polymers, polymethylmethacrylate (PMMA) and polycarbonate (PC), using dynamic mechanical analysis and uniaxial compression testing. Good agreement has been found between theory and experiment for the non-linear behavior of the initial Young's modulus, at the very high strain rates.

The rheology of filled polymer systems is an ever expanding field in the polymer industry today. Using a concise, practical and simple format this comprehensive work explains the concepts behind filled polymer systems and the rheological techniques involved in studying their behaviour. Aware that the readers of the book may come from differing background, the first three chapters familiarize the reader with the basics about polymers, fillers and physicochemical interactions between them, rheology and rheometry. Covering such topics as preparation of filled polymer systems, steady shear viscous properties and extentional flow properties, this book covers the areas of importance from an introductory level through to more complex issues.

Review
`Rheology of Filled Polymer Systems will be of most interest to those involved in injection molding and similar processes. [...]if you are interested in molding processes, and especially in the theoretical background, then this book is for you. [...]The main feature which distinguishes this book from others on polymer rheology is its focus on filled systems. The addition of fillers (particles, fibers, flakes, etc.) makes such systems behave much differently than unfilled polymers. [...]the writing is quite good [...] Shenoy does a good job of presenting data for a variety of systems, explaining the trends intuitively, and then showing how it all fits in with the theories developed earlier in the book.'
Barry Berenberg in Composite.About.com

Demon3 on November 22, 2000Format: Hardcover
Book Review - Rheology of Filled Polymer Systems Aroon V. Shenoy

Kluwer Academic Publishers ISBN 0-412-83100-7

As a researcher in the area of particulate-filled composites I am continually looking for good books on this subject. Such books are hard to find, possibly because the topic is so multi-disciplinary that few authors manage to bring together the knowledge from polymer science (processing, stability, mechanical properties), surface science (dispersion, wetting, surface-treatment) and rheology (compounding and processing).

One area where it is especially difficult to find good information is that of filled polymer rheology. This topic is vital to understanding the behaviour of a filled polymer melt. For example, extruder throughput and mould filling during injection moulding are critical factors that must be understood when formulating a good particulate-filled polymer composite. I have found it hard to understand most texts on filled polymer rheology and therefore I was relieved when I read this book. The author must be congratulated on having presented such a complex field in a focussed and interesting way. All aspects of rheological measurement techniques are covered. First of all is an introduction to the rheological behaviour of un-filled polymers. Basic rheological concepts are presented followed by a comparison of the different measurement techniques. Steady shear and unsteady shear are both treated in detail where the author highlights the trends such as the influence of particle size, shape, distribution, concentration and surface treatment. Another chapter discusses the different types of polymer processing equipment and their relative merits and drawbacks for preparing polymer composites.

One especially intriguing section shows that even MFI data, which is simple and inexpensive to obtain, can be used as a powerful tool for estimating the rheological response of a filled polymer melt. The author shows that just by knowing the MFI and the Tg of the polymer, it is possible to calculate an approximate rheological response of the filled polymer melt. This estimation has sufficient accuracy to be of use in predicting the flow behaviour of the filled polymer melt during processing. Thus, even the humble MFI technique is shown to be a powerful tool and I expect that Shenoy's Unification approach will prove useful for many people, including myself.

I highly recommend this book to anyone interested in filled polymers. It is clearly written by someone with an excellent grasp of the subject. The text is concise and easy to read whilst the content is well organized and interesting.

Flexible Polyurethane (PU) foam is the material most widely used among urethanes. The foams were synthesized via the reaction of soy polyol, mixtures of isocyanates MDI:TDI (80:20), in the presence of water (blowing agent) with molding process. This experiment was to analyze the physical properties of soy polyol and elaborate the principle of catalyst within the synthesis. The use of liquid and solid catalyst on the polyol synthesis results in significant cellular morphology and properties of polyurethane foam. It is found that the PU which was synthesized using bentonite catalyst has an irregular form of cell morphology, and it has higher density than using sulphuric acid catalyst.

In the Upper Peninsula of Michigan, over 500 million tons of copper rich rock were removed from mines and treated in chemical baths to extract copper. Toxic substances have been seeping into the watersheds from the resultant waste stamp sands. Recent work on developing a circular economy using recycled plastic for distributed manufacturing technologies has proven promising, and this study investigates the potential to use this approach to form stamp sand and acrylonitrile styrene acrylate (ASA) composites. Specifically, this study found the maximum amount of stamp sand that was able to be added to waste ASA by mass with a single auger recyclebot system for compounding was below 40%. The mechanical properties of the composite were evaluated up to 40%, and the addition of stamp sand reduced the material's ultimate tensile strength by about half compared to the strength of raw recycled ASA, regardless of the percent stamp sand in the composite. However, this strength reduction plateaus and the tensile strength of the ASA and stamp sand composites can be compared favorably with acrylonitrile butadiene styrene (ABS) at any level. This makes waste ASA-stamp sand composites potential replacements for outdoor applications of ABS as well as some current ASA applications. These results are promising and call for future work to evaluate the technical, economic and environmental potential for waste ASA-stamp sand composites.

Polymeric porous membranes were prepared from polytetrafluoroethylene (PTFE) fine powder by a series of mechanical operations, such as extrusion, rolling, and stretching. The structure of the prepared porous membrane was well characterized by a spatial periodicity of nodes (domain of agglomerated PTFE particles) and fibril domains. The fibrils were highly oriented in the direction of the stretching operation, providing pores in the polymeric membrane as slit-like voids between adjoining fibrils. The unit size of the periodic structure varied depending on the number averaged molecular weight of PTFE and the stretching conditions, the temperature of stretching, and the stretching rate and stretching ratio. A fibril consisted of several thread-like structures that were easily formed between PTFE particles due to the rolling operation in parallel with their direction. The dependence of the steady tensile stress in the stretching operation on the PTFE molecular weight was much weaker than that presumed for noncrystalline polymeric systems. The activation energy of 11.3 kJ/mol for the growth of fibrils was only several times as large as the thermal energy at the ambient temperature. These results imply that the thread-like structures can easily be pulled out of PTFE particles. This view is in accordance with the previously proposed microstructure in PTFE particles.

Archaeologists have defined past civilizations by the materials that predominated in their societies. The evolution of the use of these materials—stone, bronze, and iron—enabled significant and concurrent changes in the cultures that mastered them. The ability to develop, shape, and use these substances has been one of the measures of a civilization’s capabilities, so much so that we now identify them as the Stone Age, Bronze Age, and Iron Age. Historians have also associated the comings and goings of other, more recent, periods with the prevalence of particular types of materials. Brooke Hindle identified America’s pre-Civil War period as its “Wooden Age,” and he characterized the society as one that was “pervasively conditioned by wood.”  This dependence slowly subsided after 1850 and was replaced in part by metals and the corresponding products of industrialization. 

There was one common characteristic that defined these former ages. The materials in question all came from nature. However, at the dawning of the twentieth century, scientists and engineers began to master a new class of materials called polymers. Although some of these occurred in nature (like spider silk or natural rubber), other polymers were made in laboratories and factories and had properties superior to those existing in the natural world. Over the past century, the ability to create and manipulate natural and synthetic polymers has resulted in a revolutionary transformation of our own material culture. One hundred years ago, the artifacts of everyday life were made of wood, stone, textiles, glass, or metal. This is no longer the case, as polymers now often replace these substances and enhance the quality of the products made with them. The result is that the emergence of polymers has become one of the most significant scientific and engineering achievements in the past century. The father of polymer education, Herman Mark, suggested in 1982 that society was “coming to an age in polymer science.”  In 1976, an author in Chemical Week simply christened this the “polymer age.” 

Although it is often difficult and arbitrary to pinpoint dates of when “ages” like this begin or end, it might be argued that the Polymer Age had its beginnings in the late 1970s. While the earliest polymer discoveries took place in the 1920s, it was not until a half century later that the consumption of synthetic polymer materials overtook metals in the United States.  In 1973, the United States produced the same amount of synthetic polymers as it did steel—15.5 million cubic meters.  In 1976, the United States consumed more plastics than metal on a per volume basis for the first time, and plastics became the most consumed synthetic material in the country.  The rapidity with which polymers became so prevalent is an astonishing story.  In the 1930s, the United States produced virtually no polymers. Forty years later, it produced twenty-three million metric tons. In 1900, only a handful of chemists concerned themselves with materials that would later be known as “polymers,” and none knew what they truly were. Today, half of all chemists work with them in one form or another.  Statistics like these are strong indicators that a new material age has begun.

Cultural indicators also point to a sea change since the 1970s in how we value polymer or plastic products. Consider how the idea of plastics was interpreted by Hollywood and pop music stars in the 1960s. In the 1967 film The Graduate, Benjamin Braddock (played by Dustin Hoffman) was told by one of his father’s colleagues that the future lay in one word—“plastics.” To Braddock, this suggestion conveyed a sense of conformity, selling-out, boredom, and cheap imitation. The audience of the 1960s easily understood how the mere suggestion of “plastics” symbolized the dull life Braddock would eagerly try to escape. It reminded viewers of a similar song released that same year by pop duo Sonny and Cher, who sang about the “plastic man.” Their lyrics warned about a man not to be trusted, like someone selling cars on television. He was working day and night, not disclosing he was recruiting everyone for his commercial desires. They sang, “He’s doing everyone he can . . . Plastic Man.” The Beatles Rubber Soul album, released in the mid 1960s, further exemplified the negative connotation of another polymer term.

Significantly, an important cultural shift has occurred since then. By the 1970s, the image of plastics began to lose its substandard connotations and instead conveyed the belief that polymers represented a new and potentially better way of life.  Symbolizing this phenomenon was an unlikely musician who recognized the emergence of polymers as a new dominant material reality. From 1976 to 1979, legendary punk rock singer Marion Elliot adopted the pseudonym “Poly Styrene” to make a statement about the significance of the changes she saw happening around her.  She created a character who idealized the glamour of plastic and echoed a youth movement that would eventually come to embrace a new polymer world. She chose the name Poly Styrene for this persona as she herself became infatuated with “plastic” society. One of her songs, a top-thirty hit in London, was called “The Day the World Turned Day-Glo;” in its lyrics she observed that polymers were over taking society.

This song paralleled the dawn of a new material era—a Polymer Age.

While it is now nearly impossible to go about a normal day without interacting in significant ways with polymers, they have ironically become something of a unseen substance. As Steve Love, Akron journalist and coauthor of Wheels of Fortune, wrote, “Polymers have an identity problem. They are, comparatively speaking, invisible . . . .” 

This invisibility needs to change.

After the process of vulcanization was established in 1839, natural rubber quickly became one of the vital material components of society. The dependence upon it grew so great that during World War II, when the United States realized that it could be easily cut off from the world’s sources of natural rubber, its entire military operation nearly ground to a halt. Without rubber, the greatest military nation in the world would be quickly rendered powerless. The quest to develop synthetic rubber during World War II led in part to the predominance of the synthetic polymer materials that surround us almost invisibly. We are living in the midst of a Polymer Age, and few of us realize it, or even know what this means. As Jeffrey L. Meikle argued in his book American Plastic, “most people ignored . . . that the United States entered the ‘Plastics Age’ in 1979 when the annual volume of plastic exceeded that of steel.”  We can no longer ignore its presence in our lives, and the history of its emergence requires telling.

With some notable exceptions, there is a disproportionate relationship between the significance of polymers and the number of historical, scientific, and popular discussions that analyze their development.

Compared to the number of scholarly studies on other scientific and technological developments like computers, automobiles, and electricity, historians have also been surprisingly quiet on the subject of polymers.  The retrospective studies that do exist were largely written by former polymer practitioners. These “insider” stories include memoirs, review articles, and autobiographies. Ffor the most part, biographical treatments have far superseded the institutional perspective of the history of polymers.

There is no question that institutions have been essential to the emergence of the Polymer Age, and their historical neglect is an oversight that requires attention. An institutional perspective can help us understand the intellectual and social foundations from which polymer science and engineering developed. Much as an individual’s biography yields important insights into a particular historical context, so, too, does an institutional focus reveal key perspectives. The Polymer Age arose through an international network of researchers working within large academic, industrial, and governmental organizations that over time developed the scientific and engineering skills to create and commercialize polymers. Among these institutions are academic programs (including the University of Akron, the University of Massachusetts-Amherst, Case Western Reserve University, California Institute of Technology, the University of Southern Mississippi, and Brooklyn Polytechnic), industrial organizations (including IG Farben, DuPont, Dow Chemical, Goodyear, Bridgestone/Firestone, B. F. Goodrich, and General Tire), and various government agencies and scientific societies like the Rubber Division of the American Chemical Society.

It is beyond the scope of this book to present a sweeping account of the entire network of institutions responsible for the emergence of the Polymer Age over the past century. Instead, this book examines the story within the framework of one academic institution that has played the longest, and arguably the most influential, role in creating and shaping the Polymer Age—the University of Akron. This university has played a signal role in the emergence of the Polymer Age starting in 1909 when Charles Knight offered the world’s first complete course in rubber chemistry, marking the birth of a new academic discipline. This course has now evolved into an entire college—the College of Polymer Science and Polymer Engineering—which has been ranked for the last ten years as one of the top two academic institutions in the United States in the field.  An examination of the near century in between the foundation of the course and the flourishing of the college, demonstrates how these long polymer chains became chains of opportunity for an academic discipline, an economic region, and a university.

Although additive layer manufacturing is well established for rapid prototyping the low throughput and historic costs have prevented mass-scale adoption. The recent development of the RepRap, an open source self-replicating rapid prototyper, has made low-cost 3-D printers readily available to the public at reasonable prices (<$1,000). The RepRap (Prusa Mendell variant) currently prints 3-D objects in a 200x200x140 square millimeters build envelope from acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA). ABS and PLA are both thermoplastics that can be injection-molded, each with their own benefits, as ABS is rigid and durable, while PLA is plant-based and can be recycled and composted. The melting temperature of ABS and PLA enable use in low-cost 3-D printers, as these temperature are low enough to use in melt extrusion in the home, while high enough for prints to retain their shape at average use temperatures. Using 3-D printers to manufacture provides the ability to both change the fill composition by printing voids and fabricate shapes that are impossible to make using tradition methods like injection molding. This allows more complicated shapes to be created while using less material, which could reduce environmental impact.

As the open source 3-D printers continue to evolve and improve in both cost and performance, the potential for economically-viable distributed manufacturing of products increases. Thus, products and components could be customized and printed on-site by individual consumers as needed, reversing the historical trend towards centrally mass-manufactured and shipped products. Distributed manufacturing reduces embodied transportation energy from the distribution of conventional centralized manufacturing, but questions remain concerning the potential for increases in the overall embodied energy of the manufacturing due to reduction in scale. In order to quantify the environmental impact of distributed manufacturing using 3-D printers, a life cycle analysis was performed on a plastic juicer. The energy consumed and emissions produced from conventional large-scale production overseas are compared to experimental measurements on a RepRap producing identical products with ABS and PLA. The results of this LCA are discussed in relation to the environmental impact of distributed manufacturing with 3-D printers and polymer selection for 3-D printing to reduce this impact. The results of this study show that distributed manufacturing uses less energy than conventional manufacturing due to the RepRap's unique ability to reduce fill composition. Distributed manufacturing also has less emissions than conventional manufacturing when using PLA and when using ABS with solar photovoltaic power. The results of this study indicate that open-source additive layer distributed manufacturing is both technically viable and beneficial from an ecological perspective.

Reducing the residual monomer content is a desire of every polymer producer, as a product with no or very low levels of residual monomer would have a different commercial appeal. The presence of residual monomer may create hazards to workers as a result of long-term exposure during polymer processing and sometimes even to customers. There are several techniques for reducing residual monomer content and the industrial importance that has been given to the presence of residual monomers in polymeric products is reflected in the number of patents involving residual monomer reduction techniques. Nevertheless, choosing the best, or the most adequate, technique is not always a n easy task, and one still observes a relative lack of scientific literature on this subject. The technique to be employed will depend upon polymer application, which determines the grade of purity, and also on polymer quality, as some monomer reducing techniques might change polymer properties. The main objective of this review is to summarke and discuss the principal methods employed for reducing residual monomer content.

Corn fibers and luffa peels were evaluated for removing toxic heavy metal ions and dissolved organic dyes from water. Fresh peels were pretreated to remove all soluble components before using them for extraction studies. Presence of eOH and eCO 2 H functional groups on the surface of the peels and rough morphologies were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy investigations, respectively. Corn fibers and luffa peels showed maximum extraction effi-ciencies within the pH range of 4e10 and adsorption reached a steady state within 2e3 h. Prewashed corn fibers and luffa peals extracted 159 mg g À1 and 90 mg g À1 of alcian blue, 70 mg g À1 and 124 mg g À1 of methylene blue, 50 mg g À1 and 108 mg g À1 of neutral red as well as 35 mg g À1 and 40 mg g À1 of coomassie brilliant blue from water, respectively. Both materials did not show significant extraction affinity towards heavy metal ions such as Pb 2þ (1 mg g À1), Ni 2þ (4 mg g À1 for corn fiber and 12 mg g À1 for luffa peels), and chromate (3 mg g À1 for corn fibers and 6 mg g À1 for luffa peels) ions from water. The Langmuir and Freundlich isotherms were used to understand the adsorption process on the surface of the adsorbents. Langmuir isotherm model yielded the best fit for the data obtained in the study, indicating a monolayer adsorption of pollutants on the adsorbent surface. Both adsorbents can be regenerated at acidic pH and could be reused for up to five cycles without significant loss of efficiency. Our experimental results suggest that both natural materials are effective towards removing dissolved dyes from water.

Carbon-nanotubes (CNTs) have been used with polymers from the date of their inception to make composites having remarkable properties. An attempt has been made in this direction, in order to enhance mechanical and tribological properties of the composite materials. The latter, were achieved through the injection molding of high density polyethylene (HDPE) reinforced with specific volume fraction of CNTs. A considerable improvement on mechanical properties of the material can be observed when the volume fraction of CNT is increased. The composite reinforcement shows a good load transfer effect and interface link between CNT and HDPE. The volumetric wear rate is calculated from the Wang's model, Ratner's correlation and reciprocal of toughness. The results obtained clearly show the linear relationship with CNT loading which supports the microscopic wear model. It is concluded that both Halpin-Tsai and modified series model can be used to predict Young's modulus of CNT-HDPE composites. From thermal analysis study, it is found that melting point and oxidation temperature of the composites are not affected by the addition of CNTs, however its crystallinity seems to increase.

The open source introduction of fused filament fabrication (FFF) enables distributed manufacturing of consumer products. However, with a wide range of low-cost FFF 3-D printers and settings possible, there is a lack of information on the variability in printed mechanical properties. This paper utilizes a large pool of 47 user-assembled 3-D printers to quantify the mechanical property variations of ultimate tensile strength (UTS) and yield strength of FFF printed components using ASTM D638-14 horizontally-oriented Type I and IV geometries for poly lactic acid (PLA). The results indicate that utilizing Type IV tensile test piece geometry may overestimate the UTS relative to the Type I. Furthermore, anisotropic mechanical property variances were quantified for Type IV specimens (vertical and horizontal orientations). Vertical tensile specimens had an ultimate tensile strength 47.9% less than horizontal. Finally, the abundant supply of PLA 3-D prints suggest open-source printers assembled by individual operators can produce quality plastic components although the mechanical performance of the given part can vary dramatically based on the operator selection of printing parameters that provide a visually acceptable part.

In this study, processing–structure–mechanical properties relationships in expanded wood fiber polystyrene composites (EPSC) made with a physical blowing agent were investigated. A systematic investigation was performed based on a statistical experimental design. The samples were saturated with carbon dioxide at high pressure and ambient temperature and the saturated specimens were expanded at elevated temperatures. The relations between impact and tensile properties of EPSC and foaming process and structure were studied. Fiber content was found to be the most important parameter controlling impact strength and tensile modulus. The impact strength of EPSC was increased about three times when the fiber content increased to 20%. Using the Halpin–Tsai equation, a model was developed to relate tensile modulus to the density of EPSC.
(citation # 48)

There is a growing concern with worldwide deterioration of traditional materials such as concrete, steel, and timber. Recently, attention has shifted to the use of fiber reinforced polymer composites (FRPs) as alternative materials. As FRPs are non-corrosive, high strength and modulus values compared to their density, light weight, acceptable deformability, tailored design and excellent formability enable the fabrication of new elements and the structural rehabilitation of the existing parts made of traditional materials. Furthermore, the resistance of FRP materials to corrosion means that they can be used to replace steel and reinforced concrete in situations when they would be exposed to corrosion. FRP therefore has wide application prospects in civil engineering ranging from reinforcing rods and tendons, wraps for seismic retrofit of columns and externally bonded reinforcement for strengthening of walls, beams, and slabs, to all-composite bridge decks, and even hybrid and all-composite structural systems. This paper is a review of the application of FRPs in civil engineering. Firstly, the paper will elucidate the basic information about FRP composites, including the definition, description of the components such as fibers and matrices. Then it pointed some fabrication processes, mechanical properties. Finally, it will focus on the application of FRP in civil engineering.

3-D printing shows great potential in laboratories for making customized labware and reaction vessels. In addition, affordable fused filament fabrication (FFF)-based 3-D printing has successfully produced high-quality and affordable scientific equipment, focusing on tools without strict chemical compatibility limitations. As the additives and colorants used in 3-D printing filaments are proprietary, their compatibility with common chemicals is unknown, which has prevented their widespread use in laboratory chemical processing. In this study, the compatibility of ten widely available FFF plastics with solvents, acids, bases and solutions used in the wet processing of semiconductor materials is explored. The results provide data on materials unavailable in the literature and the chemical properties of 3-D printable plastics that were, are in line with literature. Overall, many 3-D printable plastics are compatible with concentrated solutions. Polypropylene emerged as a promising 3-D printable material for semiconductor processing due to its tolerance of strongly oxidizing acids, such as nitric and sulfuric acids. In addition, 3-D printed custom tools were demonstrated for a range of wet processing applications. The results show that 3-D printed plastics are potential materials for bespoke chemically resistant labware at less than 10% of the cost of such purchased tools. However, further studies are required to ascertain if such materials are fully compatible with clean room processing.