Polymer-based Products Research Articles

Lipid-based Nanoplatforms in Cancer Therapy: Recent Advances and Applications

Though modern available cancer therapies are effective, they possess major adverse effects, causing non-compliance to patients. Furthermore, the majority of the polymeric-based medication platforms are certainly not universally acceptable, due to their several restrictions. With this juxtaposition, lipid-based medication delivery systems have appeared as promising drug nanocarriers to replace the majority of the polymer-based products because they are in a position to reverse polymer as well as, drug-associated restrictions. Furthermore, the amalgamation of the basic principle of nanotechnology in designing lipid nanocarriers, which are the latest form of lipid carriers, has tremendous chemotherapeutic possibilities as tumor-targeted drug-delivery pertaining to tumor therapy. Apart from this, it is reported that nearly 40% of the modern medication entities are lipophilic. Moreover, research continues to be efficient in attaining a significant understanding of the absorption and bioavailability of the developed lipids systems.

Effect of Sodium Alginate Type on Drug Release from Chitosan-Sodium Alginate-Based In Situ Film-Forming Tablets.

Natural polymers are promising as the carrier of matrix-based sustained release tablets but limited by their diversity in source and structure properties. Our previous studies found that chitosan (CS)- and alginate (SA)-based tablets can form self-assembled polyelectrolyte complex (PEC) film on the surface, which controlled drug release with a novel mechanism. To elucidate whether PEC-based sustained drug delivery system could weaken the influence of single-matrix material diversity on drug release behavior, taking theophylline as a drug model, the effect of SA structure properties, including viscosity, G/M ratio, SA salt type, and degree of esterification on drug release profiles, swelling, and erosion of CS-SA composite system was investigated. The results showed that the viscosity, G content, salt type, and esterification degree of SA had a remarkable influence on drug release when SA alone was used as a matrix, but little effect of these parameters on drug release was observed in CS-SA combination system. SA of low viscosity is superior in controlling drug release from CS-SA combination system. Potassium, magnesium salt of SA, and esterified SA can help form PEC of higher thickness with different swelling and erosion extent. In conclusion, this study demonstrated that drug release diversity due to SA structure difference can be well eradicated by using CS-SA combination system, which is a promising strategy to manufacture natural polymer-based products with constant quality.

Analysis of General and Specific Standardization Developments in Additive Manufacturing From a Materials and Technological Approach

Additive manufacturing processes and products are very present in the current productive landscape, and in fact these technologies have been one of the most intensively studied and improved during the last years; however, there is still no defined and homogeneous regulatory context for this field. In this work, a thorough review of the main general and specific regulatory developments in design, materials and processes standards for additive manufacturing has been carried out, with special attention to the standards for mechanical characterization of polymer-based products. In many cases standards developed for other productive contexts are identified as recommended references, and some contradictory trends can be identified when different documents and previous experiences are consulted. Thus, as it is logical considering that all these technologies are involved in an intensive and continuous evolution process, there is a certain lack of clarity regarding the standards to be considered. This work aims to contribute to clarify the current standardization context in additive manufacturing and provide some guidelines for the identification of appropriate standards. The paper also emphasizes that the key for next regulatory developments in mechanical testing is to develop standards that consider particular AM processes along with materials. Moreover, a great gap between available standard about additive technologies based on metallic materials and polymer materials during the last years has been detected. Finally, the provided overview is considered of interest as support for research and practice in additive manufacturing, and both in intensive productive scenarios and for particular users and makers.

Human Engineered Cartilage and Decellularized Matrix as an Alternative to Animal Osteoarthritis Model.

(1) Objective: to obtain a reproducible, robust, well-defined, and cost-affordable in vitro model of human cartilage degeneration, suitable for drug screening; (2) Methods: we proposed 3D models of engineered cartilage, considering two human chondrocyte sources (articular/nasal) and five culture methods (pellet, alginate beads, silk/alginate microcarriers, and decellularized cartilage). Engineered cartilages were treated with pro-inflammatory cytokine IL-1β to promote cartilage degradation; (3) Results: articular chondrocytes have been rejected since they exhibit low cellular doubling with respect to nasal cells, with longer culture time for cell expansion; furthermore, pellet and alginate bead cultures lead to insufficient cartilage matrix production. Decellularized cartilage resulted as good support for degeneration model, but long culture time and high cell amount are required to obtain the adequate scaffold colonization. Here, we proposed, for the first time, the combined use of decellularized cartilage, as aggrecanase substrate, with pellet, alginate beads, or silk/alginate microcarriers, as polymeric scaffolds for chondrocyte cultures. This approach enables the development of suitable models of cartilaginous pathology. The results obtained after cryopreservation also demonstrated that beads and microcarriers are able to preserve chondrocyte functionality and metabolic activity; (4) Conclusions: alginate and silk/alginate-based scaffolds can be easily produced and cryopreserved to obtain a cost-affordable and ready-to-use polymer-based product for the subsequent screening of anti-inflammatory drugs for cartilage diseases.

Evaluation of effectiveness of methyl methacrylate as retarder additive in polymer concrete

It is a known fact that most thermoset resins are very sensitive to hot temperature, which hinders its ability to produce polymer-based products in a large scale. This study aims to investigate the potential of manufacturing polymer concrete in ambient room temperature of 30±2°C. A laboratory test was conducted with the introduction of polyester retarder additive into polyester resin formulation. All tests were carried out strictly in ambient room temperature (30±2°C). For comparison purpose, polyester resin without retarder additive was prepared as the control formulation under identical condition. Visual inspection was done on the fresh working life of polyester resin with 0%, 0.1%, 0.15%, and 0.2% of retarder additive in two different types of polyester resin-isophthalic and orthophthalic. Characterization on retarder additive was conducted under X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and, 1H and 13C Nuclear Magnetic Resonance (NMR). Investigation on the effects of polymer retarder additive on the physical and mechanical properties of polymer resin, polymer blended, and polymer concrete showed that the retarder additive had prolonged the working life and improved properties of polymer concrete. These proved the potential of adding retarder additive in polymer concrete in ambient room temperature of 30±2°C.

Adiabatic shear band formation as a result of cryogenic CNC machining of elastomers

The traditional method for producing polymer-based products is the use of moulding technologies such as injection moulding. CNC machining methods are predominantly used for metal part manufacture. The use of CNC machining methods for direct machining of polymers has been discussed in previous studies, particularly for hard polymers such as polypropylene. The CNC machining of soft elastomers, such as ethylene vinyl acetate (EVA), even at significantly reduced temperatures presents a number of challenges, with one being the formation of a machining phenomenon termed adiabatic shear bands, which can lead to increased part surface roughness and reduced part quality. The adiabatic shear band is an area on a chip where the ductile properties of the material being machined have been exceeded and the heat generated does not have sufficient time to be removed. This can lead to permanent material damage resulting in reduced fatigue resistance. The adiabatic shear formation has the potential to be even more evident with the machining of elastomers, leading to rapid material degradation, poor surface finish characteristics, and reduced material attenuation. In this paper the state of the art in cryogenic manufacturing is described and the concept of cryogenic CNC machining of elastomers is discussed. The experimental work consists of machining EVA and Neoprene utilizing the described cryogenic CNC machining facility. Sample chips are taken from the experimental testing and analysed using a scanning electron microscope to illustrate the adiabatic shear band formation in some cases. It is observed that in order to reduce this effect, correct machining parameters corresponding to the elasticity values need to be used and the glass transition temperature needs to be maintained.

Computer aided polymer design using multi-scale modelling

The ability to predict the key physical and chemical properties of polymeric materials from their repeat-unit structure and chain-length architecture prior to synthesis is of great value for the design of polymer-based chemical products, with new functionalities and improved performance. Computer aided molecular design (CAMD) methods can expedite the design process by establishing input-output relations between the type and number of functional groups in a polymer repeat unit and the desired macroscopic properties. A multi-scale model-based approach that combines a CAMD technique based on group contributionplus models for predicting polymer repeat unit properties with atomistic simulations for providing first-principles arrangements of the repeat units and for predictions of physical properties of the chosen candidate polymer structures, has been developed and tested for design of polymers with desired properties. A case study is used to highlight the main features of this multi-scale model-based approach for the design of a polymer-based product.

Application of the reaction engineering approach (REA) to model cyclic drying of thin layers of polyvinyl alcohol (PVA)/glycerol/water mixture

Rapid development of industrial polymer-based product requires considerable research in polymer drying. Cyclic or intermittent drying is used occasionally to save energy and improve product quality. Most published studies employ diffusion-based models. Reaction engineering approach (REA) is a lumped parameter model which is comparably simple and is now applied to cyclic situation for the first time. New definitions of equilibrium activation energy (Δ E v, b ) had to be introduced. With these definitions, very reasonable agreement between the predicted and published experimental data is shown. It has advantage over the diffusion model where in general complex diffusivity functions are used and had to be established using experimental data anyway. REA may be used in plant-wide simulations, where the drying kinetics has to be coupled with many other equations to be solved together. In this case, the computation time would be generally reduced if there is no need to solve the spatial distribution of water content inside the product.

Tuning the thermal conductivity of polymers with mechanical strains

The low thermal conductivity of polymers limits their heat spreading capability, which is one of the major technical barriers for the polymer-based products, especially electronics, such as organic light emitting diodes. It is highly desirable to enhance the thermal conductivity of polymer materials including polymer composites. Mechanical stretching could align polymer chains which are intrinsically low-dimensional material that could have very high thermal conductivity and thus enhancing the thermal conductivity of polymers. In this work, the all-atom model molecular-dynamics simulation is conducted to investigate the tuning of polymer thermal conductivity using mechanical strains. The simulation results show that the thermal conductivity of polymers increases with the increasing strain and the enhancement is larger when the polymer is stretched slower. Molecular weight also affects the thermal conductivity under the same stretching condition. More importantly, the thermal-conductivity enhancement could be exponentially fitted with the orientational order parameter which describes the chain conformation change. This study could guide the development of advanced reconfigurable and tunable thermal management technologies.

Equilibrium Isotherms of the Adsorption of Pyrolysis Gases from Polymer Products

There are many polymer products used in homes, and there is great concern about the toxic compounds which may be produced from these in the case of fire. Typical polymer-based products used in home...

Linear anionic polyacrylamide as an effective post-fire soil treatment: Understanding the chemistry and physical science

Controlling erosion, reestablishing vegetation, and overcoming the negative effects of hydrophobic soils has long been a challenge following catastrophic wildfire on forested lands and rangelands. A three-year controlled study was recently completed to compare polyacrylamide soil treatment to the traditional cover method using agricultural straw on high severity burned soils of the Red Bull Fire, which burned through the Uinta National Forest near Provo, Utah, in July and August of 2004. Weed free, recycled paper pellets containing polyacrylamide were found to be an effective Burn Area Emergency Rehabilitation treatment option on clay rich soils containing divalent cations (i.e., Ca2+) within the soil matrix. This study showed aerial application of the granular polyacrylamide pellets resulted in an even distribution of the polymer-based product on the soil surface. Through water activation, a blend of water-soluble linear anionic polyacrylamide copolymers are slowly released, which bind with the soil particles, structurally stabilizing the soil. When compared to agricultural straw, polyacrylamide results show improved revegetation, reduced soil hydrophobicity, and reduced soil erosion.

Squeeze flow as a tool for developing optimized gypsum plasters

This paper presents a rheological investigation of pure gypsum (PG) and a commercial gypsum–lime–filler plaster (CP) using the modified Vicat apparatus and squeeze flow method. The samples were tested at several different intervals after manual or mechanical mixing. The results confirmed squeeze flow to be more sensitive in determining fresh paste behavior than the modified Vicat apparatus. PG set faster when prepared in mechanical mixer than when manually mixed. Conversely, the CP composition presented longer setting when mixed mechanically. The study also included the analysis of two ready-to-use polymer-based products for leveling and rendering (drywall joint compound – DJC; acrylic putty – AP) measured by squeeze flow and compared to the commercial composition.

A systematic approach to the Kansei factors of tactile sense regarding the surface roughness

Designing products to satisfy customers’ emotion requires the information gathered through the human senses, which are visual, auditory, olfactory, gustatory, or tactile senses. By controlling certain design factors, customers’ emotion can be evaluated, designed, and satisfied. In this study, a systematic approach is proposed to study the tactile sense regarding the surface roughness. Numerous pairs of antonymous tactile adjectives are collected and clustered. The optimal number of adjective clusters is estimated based on the several criterion functions. The representative average preferences of the final clusters are obtained as the estimates of engineering parameters to control the surface roughness of the commercial polymer-based products.

Selection and Use of Polymer-Based Materials in the Repair of Concrete Structures

A large number of specialty repair concrete products are currently marketed and new products are being continually introduced leaving clients, engineers, and designers bewildered. The paucity of information on the mechanical and thermal properties of a given product complicates material selection. These difficulties force designers to adopt materials that have properties close to those of the original concrete. In so doing they often reject advantages offered by polymer-based products now on the market. The challenge is to understand the properties of each material and select the appropriate one. To assure predictable performance, the designer must have a good knowledge and understanding of the properties of the repair material, how it will interact with the environment in service, and a clear description of maintenance procedures and intervals. Typical properties of currently used polymeric materials in relation to the important aspect of selection based on compatibility with in-service conditions and suitability with the application procedures of the job are discussed.

Mechanical Behavior and Biodegradation of Poly(ε-caprolactone)/Starch Blends with and without Expansor

The use of biodegradable polymers has provided an alternative to the problem of polymer-based products discarded in the environment. Poly(e-caprolactone) (PCL) is a biodegradable polymer that has been used industrially, but it is very expensive. Starch is a potentially useful material for biodegradable plastics because of its natural abundance and low cost. The aim of this work was to examine the effect of adding azodicarbonomide (ADC) as an expansor to blends of PCL with corn starch. Different proportions, of ADC (0.1%, 0.2% and 0.3%, w/w) were added to pure PCL and to PCL/starch (50/50) blends and their properties were studied. Biodegradable blends of PCL with starch had a higher density than PCL alone and the addition of ADC reduced the density of the materials. The incorporation of starch increased the water absorption and ADC did not significantly alter this property. The incorporation of starch into PCL reduced the tensile strength and the elongation at break; ADC enhanced these reductions and also decreased the Young’s modulus of PCL. SEM showed that blends prepared with starch were immiscible, had a homogeneous dispersion of starch, and poor interfacial adhesion. The addition of ADC resulted in cells in the interior of the polymers. The 50/50 PCL/starch blends biodegraded faster than PCL, and ADC had no significant influence on the biodegradation of the blends but inhibited the biodegradation of PCL.

Developments in polymer architecture and design applicable to surface coatings

In order to improve existing polymeric materials, or to design new polymer-based products, one needs to be able to control the polymeric chains. Historically, ionic living and group transfer polymerisations have allowed the design of polymeric architectures with predictable molecular weights and narrow molecular-weight distributions. However, these methods are difficult to undertake as they demand complex experimental conditions. Recently, living radical polymerisation (LRP) has been reported as an efficient living polymerisation process, based on free radical polymerisation chemistry. The wide range of monomers which have been successfully polymerised, the ease of scaling up a reaction, and the high tolerance to functional groups makes it the most suitable process to obtain well-defined architectures (eg polymers with well-known degrees of polymerisation, molecular-weight distribution, end functionalities, chain architectures and composition). LRP is more cost-effective and easier to manipulate than other existing living polymerisation methods, and is therefore the most viable process for industrial development. This paper presents the recent developments in this technique with potential for use in the surface coatings industry.

Structural Bonding in Automotive Applications

With automotive adhesives becoming more and more accepted in various new functions in car body structures in recent years, the development of new innovative polymer-based products alone is no longer sufficient. Modern integrated development concepts therefore address the whole process chain, from the prediction of final adhesive performance to the line implementation in the car manufacturing plants.

Programmed-life plastics from polyolefins: a new look at sustainability.

The term "sustainable" is often assumed to be synonymous with "renewable". However, polymers made from renewable natural resources are not necessarily eco-efficient. Cellulose-based polymers utilize more nonrenewable fossil fuels and are more polluting during manufacture than petro-based polymers. Sustainable polymers also have to be industrially acceptable, and although ultimate biodegradability in the natural environment is important, polymer-based products are required to biodegrade in a controlled way. Service life may be a year or more before the commencement of environmental degradation occurs. Many natural polymers such as rubber, lignin, and humus, like the synthetic polyolefins, biodegrade by an oxidative mechanism (oxo-biodegradation), and consequently much of nature's biological waste cannot satisfy the rapid mineralization criteria currently advocated by standards committees for synthetic polymers. Although biometric tests are more convenient to use than full composting tests, they are meaningless when applied to hydrocarbon polymers, whether natural or synthetic, since oxo-biodegradation is a slower process than hydro-biodegradation at ambient temperatures. Biodegradation standards currently proposed are unrealistic and will need to be modified on the basis of recent scientific evidence.

New polymer-based prepacked column for the reversed-phase liquid chromatographic separation of peptides over the pH range 2–12

The aim of this paper was to investigate the properties of a new column, Source™ 5RPC, for the separation of peptides at pH 2, 4.5, 7, 9 and 12 and to compare this product with similar polymer-based products available on the market. All columns were prepacked with 5 μm polystyrene–divinylbenzene polymer bead matrices and had dimensions of 150×4.6 mm I.D. Separations of angiotensin peptides were achieved on these columns using different equilibration solvents in the pH range 2–12 and elution with acetonitrile gradients. The separation of the peptide mixture obtained on Source 5RPC column was compared with that of two other commercially available polymer-based matrices. Method scouting and optimisation were carried out using the novel chromatography system, ÄKTA™ purifier.