Technical Polymer Research Articles

Wastewater phosphorus enriched algae as a sustainable flame retardant in polylactide

Revolutionizing our polymer industry for adaption to a sustainable carbon circular economy has become one of today's most demanding challenges. Exploiting renewable resources to replace fossil-fuel—based plastics with biopolymers such as poly(lactic acid) (PLA) is inevitable while using waste streams as a raw material resource at least is promising. When it comes to using PLA as technical polymer, its high flammability must be addressed by flame retardants compatible with the thermoplastic processing of PLA and its compostability. This study proposes microalgae enriched with phosphorus from wastewater (P-Algae) as an elegant way towards a kind of sustainable organophosphorus flame retardant. The concept is demonstrated by investigating the processing, pyrolysis, flammability, and fire behavior of PLA/P-Algae, while varying the P-Algae content and comparing P-Algae with four alternative bio-fillers (phosphorylated lignin, biochar, thermally treated sewage sludge, and metal phytate) with different P-contents as meaningful benchmarks.

Effect of Al-Cu-Fe Quasicrystal Particles on the Reinforcement of a Polymer–Matrix Composite: From Surface to Mechanical Properties

We examined the effect of Al59Cu25Fe13B3 (at.%) quasicrystalline (QC) reinforcement particles on the mechanical and surface properties of a polymer-matrix composite by applying a technical polymer polyphthalamide (PPA). The observed increase in the tensile Young’s modulus ranged from 1810 MPa for the pure polymer to 4114 MPa for the composite with a QC filling of 35 vol.%. The elongation at fracture decreased with the filling fraction, being equal to 16.9% for a pure polymer and dropping to 4.8% for the composite with a QC filling of 35 vol.%. The same trend was noticeable with flexural Young’s modulus, which ranged from 100 MPa for a pure polymer to 125.5 MPa for the composite with 35 vol.% of QC. It was found that the increase in the mechanical strength led to a simultaneous increase of brittleness, which was reflected in a decrease of the impact strength for a pure polymer from 98.5 kJ/m2 to 42.4 kJ/m2 for composites with a QC filling of 35 vol.%. In contrast, when filled with 5 vol.% of QC, the impact strength increased by 8%. The friction coefficient against 100C6 steel dropped from 0.15 for pure PPA down to 0.10 for 5 vol.% of the QC filling, followed by an increase to 0.26 for further QC fillings up to 35 vol.%. Interestingly, a local minimum of friction was achieved at filling factors between 5 to 20 vol.% of QC. Independently, a clear surfenergy minimum was also found for the composite material with 20 vol.% of QC filling associated with a net drop in the polar component of the surfenergy. Surfenergy refers to the surface energy related to the top of the oxide layer under ambient conditions. We hypothesise that this is related to the percolation threshold at about 13 vol.% QC, reflected in the observed behaviour of both the friction coefficient and surfenergy. For the pure QC annealed in air for 1 h at 500 °C significant wear tracks were observed accompanied by a wear debris formation. On the other hand, a pure polymer exhibited slightly visible wear tracks with no apparent debris formation, and for the composites with different QC filling factors, the wear traces were barely visible with negligible debris formation.

Lightweight hybrid composite sandwich structures with additively manufactured cellular cores

This study focuses on advancing sandwich structures by designing and fabricating complex two- and three-dimensional cellular cores combined with Carbon Fiber Reinforced Polymer (CFRP) skins. Numerical analysis is used to investigate the effect of core design and density on the bending performance. Optimal configurations are identified and experimentally validated. Professional Fused Filament Fabrication (FFF) equipment with a heating chamber is employed for manufacturing the core samples to enhance layer cohesion and material joint stiffness. A high-performance technical polymer with a superior strength-to-weight ratio is employed to maximize structural capabilities. Hybrid sandwich structures with PEI Ultem cellular cores demonstrate stiffness and strength comparable to reference materials, outperforming foam cores while slightly trailing behind Nomex® and aluminum honeycombs. In addition, the results demonstrate more efficient cell morphologies achievable through additive manufacturing technologies, surpassing the hexagonal design. This work provides valuable insights into hybrid composite materials and the potential of additive manufacturing in creating lightweight, high-performance sandwich panels.

Incorporation of olive pomace as a natural filler in to the PA6 matrix: Effect on the structure and thermal properties of synthetic Polyamide 6

In recent years, due to less environmental pollution, ecological products are recommended more and more by the different environmental unions and cooperation. To achieve this, industries have studied the use of composite materials based on natural resources because of their lightness, their resistance to corrosion, their biodegradability, and their wide availability. In the same context, the current work may open up a new way of developing an original biocomposite material by taking advantage of integrating Olive Pomace Powder (OPP) as a filler on the PA6 matrix. This technical polymer is one of the most widely used polymers thanks to its chemical and physical stability, thermal resistance, low cost, and availability.The dry OPP is used without any additional chemical treatment; it had particle sizes (160–250 μm). The PA6/OPP was prepared thanks to polymerization in situ, a new innovative way to fabricate our biocomposite. The rate of OPP varies from 5% to 20% by weight. The structural, physicochemical, and thermal behavior was determined using FTIR, XRD, DSC, and TGA-DTA techniques. The morphology of the samples was analyzed with the SEM technique. The results show that the addition of OPP does not diminish the properties of PA6 till a ratio of 20% by weight. The density and the crystallinity of PA6/OPP were almost unchangeable than PA6. It was also found that after adding 20% OPP, the crystalization temperature Tc and melting temperature Tm were the same as PA6, while the decomposition temperature Td increases slightly. These results show that this incorporation can be a way to valorize the OPP and on the other hand reduce the cost of the final product fabricating with the PA6 matrix.

ИССЛЕДОВАНИЕ ДЕФОРМАЦИОННЫХ СВОЙСТВ КОМПОЗИТОВ С ГИБРИДНОЙ МАТРИЦЕЙ МЕТОДОМ ДИНАМИЧЕСКОГО МЕХАНИЧЕСКОГО АНАЛИЗА

Polymer and composite materials (PCMs) are widely used in various industries for production of small but complex parts and large-sized body parts subjected to significant loads. The production of more critical parts from PCM has led to the need to develop new compositions, structures and technologies for molding composites. The manufacturing technology of PCMs with a hybrid matrix is presented, one of the components of which retains its "liquid" state after the molding of the products, and the second is completely solid. In the resulting composite, the “liquid” components form an independent phase and together with the main binder material, the PCMs represent a hybrid matrix. The results of dynamic mechanical analysis (DMA) of basalt plastics with hybrid matrices, in which the composition of the “liquid” component are anaerobic technical wax and organosilicon polymer materials, are presented. DMA is performed on samples of two types: № 1 - samples with a low content of "liquid" components in the matrix and № 2 - samples with a high content of "liquid" components in the matrix. According to the results of the tests carried out, the best characteristics among PCMs with various types of hybrid matrices are possessed by samples with an organosilicon polymer material in the matrix

The Polymer Film Casting Process – An Overview

Abstract Cast film extrusion allows producing technical polymer films for packaging and coating applications. Different kinds of defects may be observed. For packaging applications, the challenge is to obtain very thin films in stable conditions at the highest throughput. For coating applications, the challenge is to master the film width reduction (called neck-in) and the induced non-uniform film thickness (called dog-bone defect). Well instrumented experiments point out the influence of the polymer and of the processing conditions on the occurrence of these defects. Numerical models of increasing complexity allow capturing the main experimental features and this makes possible to propose technological solutions to delay or even to suppress defects occurrence.

Creation of Basalt Plastics with Different Types of Hybrid Matrices

Basalt plastic, thanks to its complex of valuable operational properties, has a potential variety of applications. the article describes the technology of production of basalt plastics with various types of hybrid matrices, one of the components of which is cured in the molding process, and the second-like a binder in natural materials, retains its viscoelastic state. The viscoelastic component makes it possible to increase the deformation properties in the zones of their location, preventing cracking under increased loads. As a result of the conducted mechanical tensile tests, the average values of absolute breaking forces, tensile strength and elongation during fracture of basalt plastic samples with different types of hybrid matrices were obtained. The addition of viscoelastic components (such as technical wax, anaerobic, and organosilicon polymer materials) to the basalt plastic matrix allows to increase the elongation at fracture by 2...5%. Anaerobic polymer material in the basalt plastic matrix allows to increase the tensile strength of the composite material, as well as significantly reduce the dispersion of the measured values. This provides an effective prediction of the operational properties of the structural material in the design of products. On the basis of microanalysis of the structure of basalt plastics with different types of hybrid matrices, an explanation of the causes of changes in the mechanical properties of the resulting composite materials is given.

High Performance PA 6/Cellulose Nanocomposites in the Interest of Industrial Scale Melt Processing.

On an industrial scale, it is a challenge to achieve cellulose based nanocomposites due to dispersion issues and high process temperatures sensitivity. The current study describes methods to develop mechanically strong and thermally stable polyamide 6 (PA 6) and cellulose nanofibers (CNF) composites capable of tolerating high processing temperatures. With PA 6 being a very technical polymer matrix to be reinforced with CNF, good dispersion can be achieved with a high speed kinetic mixer and also shield the CNF from excess thermal degradation by implementing extremely short processing time. This paper presents an industrially feasible method to produce PA 6/CNF nanocomposites with high CNF composition processed by a high speed kinetic mixer (GELIMAT®) followed by compression molding to obtain a homogenous and thermally stable nanocomposites aimed at high performance applications. PA 6 was reinforced with three different wt % formulations (5, 15 and 25 wt %) of cellulose nanofibers. The resulting nanocomposites exhibited significant increase in Young’s modulus and ultimate strength with CNF content, owing to the effective melt processing and the surface charge density of the CNF, which necessitated the dispersion. The thermal stability and polymer crystallinity with respect to CNF composition for the PA 6/CNF nanocomposites were examined by TGA and DSC analysis. Rheology studies indicated that viscosity of the composites increased with increase in CNF composition. Overall, this work demonstrates industrially viable manufacturing processes to fabricate high performance PA 6/CNF nanocomposites.

Industrial-waste agave fibres in flame-retarded thermoplastic starch biocomposites

Flame-retarded biocomposites of thermoplastic starch and natural fibres are successfully processed according to state-of-the-art extrusion and injection moulding. Using agave fibres and henequen fibres recovered from local industrial waste is a convincing contribution to sustainability. A systematically varied set of biocomposites is investigated comprehensively, e.g. electron microscopy is used for characterizing the morphology, rheology for the melt viscosity, tensile and impact resistance for the mechanical properties, thermal analysis for the pyrolysis, UL 94 burning chamber and oxygen index for the flammability, and cone calorimeter for the fire behaviour. Achieving sufficient mechanical properties was not the goal in our pre-competitive study but may be tackled by adding compatibilizer in future. The combination of well-dispersed natural fibres, aluminium diethylphosphinate (AlPi) and a special silicone synergist (Si) is proposed as promising innovative route for V0-classified biocomposites. The flame-retardancy modes of action in the gas phase (fuel dilution and flame inhibition) and in the condensed phase (charring, protective layer formation) are discussed in detail, as is the role of combining the ingredients. This work is a convincing proof of principle of how to prepare industrial-waste fibres biocomposites, to apply the synergistic combination of AlPi and Si for future flame-retarded technical polymer materials that are based on renewable resources and compostable.

Influence of titanium oxide-based colourants on the morphological and tribomechanical properties of injection-moulded polyoxymethylene spur gears

Abstract Regardless of colouration for functional or aesthetic purposes, technical polymer parts, like gears, require consistent properties. However, there is a lack of research into the effect of colourants on the tribomechanical properties of gears. Therefore, the effects of two pigments, titanium dioxide (white) and chrome antimony titanium oxide (yellow), and three delivery methods, masterbatch, liquid colour and direct compounding, on part morphology, dimensions, tribological and mechanical performance of injection-moulded polyoxymethylene (POM) spur gears are investigated in this paper. The white pigment accelerates the crystallisation of POM, causing fine and highly-crystalline morphological structures and smaller dimensions. However, the yellow pigment decelerates crystallisation, resulting in a coarser morphology with highly crystalline core material and bigger parts. Furthermore, the delivery method affects only the tribomechanical properties. Using a masterbatch decreases loads at break and increases deflection at break, since the carrier material acts as an impact modifier and a weak spot. The liquid colour decreases wear due to lubricating properties, whereas the pure pigments increases abrasion, especially in combination with a coarse microstructure. However, the effects of carrier systems and changes in morphology are always superimposed. Considering the performance and tolerance of technical components, colourants have to be carefully selected to ensure beneficial properties.

Bio-inspired “fluidic diode” for large-area unidirectional passive water transport even against gravity

In this paper, we describe the design, fabrication and functional principle of microfluidic diodes – devices for directional liquid transport. They are passive (i.e., need no external energy input) and are capable of unidirectional water transport even vertically against gravity, i.e. they prevent backflow of liquid. In designing the devices with an area of several cm2, we used a capillary channel network that was bio-inspired by the skin of the Texas horned lizard (Phrynosoma cornutum). By means of a CO2 laser, we engraved the microfluidic structures into plates made of poly(methyl methacrylate) (PMMA), a low-cost technical polymer commonly used in disposable microfluidics. We then characterized the topography of the fabricated 3D structures by optical coherence tomography (OCT). Theoretical analysis of the OCT data enabled us to determine their working principle which differs from that presented previously in the literature. We accessed the fluid transport properties of the device by measuring distance, velocity, wetted area and flow asymmetry. Biomimetic abstraction led to a simplified structure which was validated experimentally. All tested devices allowed unidirectional liquid transport at velocities in the range of a few mm/s in the forward direction while preventing backflow of volumes of about 0.5 ml in the backward direction on an area of approximately 28 mm x 14 mm. The transport velocity of about 1 mm/s was found to be nearly constant for a distance of approximately 2 cm, beyond which it decreased. The application spectrum ranges from biomedical microfluidics, lab-on-a-chip and micro-analysis devices to filtration, lubrication, cooling of electronics and e-ink displays.

Temporal evolution of an ion pair with a perfectly reflecting recombination sphere

We have examined the temporal evolution of an ion pair with fully suppressed geminate recombination. For this purpose, the Smoluchowski–Debye equation for a pure Coulomb potential with a reflecting boundary condition on the recombination sphere has been solved numerically and analytically (in the last case, only approximately). It has been shown that the probability of the pair non-dissociation decreases in time roughly as a power law. We also discussed the applicability of the conductivity method for studying the non-Langevin recombination in low mobility solids. An example of such an analysis is given for one technical polymer. The relation of these results to the concept of the coulombic traps has also been discussed.

Cyclic tests on cracked round bars as a quick tool to assess the long term behaviour of thermoplastics and elastomers

The aim of this work is to demonstrate the applicability of the cracked round bar test recently developed for PE-HD to other polymeric materials. The main advantage of this new test method are rather short testing times for PE-HD materials used in long-term applications such as piping. Therefore, this test is of high interest for other polymers used in similar applications.Five thermoplastic materials used for plumbing (PE-HD, PP-B, PB, PVC-U, PA12), a technical polymer (POM) and an elastomeric material (H-NBR) have been tested. Scanning electron microscopy has been applied to investigate fracture surfaces.Results show that the test method seems to be basically applicable to all tested materials. Most materials showed similar fracture behaviour as postulated in literature, despite the high acceleration factor of the cyclic CRB test.

Inverse estimation of the crystallization kinetic function of semi-crystalline polymers and short fibre reinforced composites in moderate cooling conditions

An instrumented injection mould was designed to determine the crystallization kinetics of semi-crystalline polymers and short fibre reinforced bulk composites. This set-up is an interesting alternative to other characterization devices since it is more representative of injection process conditions, and bulk samples are more suitable for studying reinforced polymers.We developed a methodology to estimate the Nakamura kinetic function K(T) by solving an inverse 1D heat conduction problem coupled to the kinetic equation. Estimated parameters are obtained in a temperature range which depends on the cooling rate. We first validated the experimental approach with a well characterized isotactic polypropylene. Then, we used this setup to determine the kinetic function of a technical polymer (poly m-xylylene adipamide–MXD6), for which the crystallization is complex since it contains nucleating agents. Our results are compared with a literature empirical model and with those obtained by DSC.

Kinetics of bulk polymerisation and Gompertz's law

The kinetics of bulk photo-polymerisation of multifunctional monomers, leading to highly cross-linked polymers, has been investigated by in situ real-time Raman spectroscopy. The decrease with time of the monomer content is described by a modified Gompertzian function originally developed for population dynamics. This function is flexible enough to take into account inhibitor effect, gel effect and glass effect which are characteristic for curing of technical polymer coatings. Layers of commercial acrylic resins with a thickness of 50 μm, with commercial initiators, are taken as model systems for the UV-curing. The proof-of-concept is presented that the combination of Raman hardware and Gompertzian software enables systematic laboratory tests of curable systems.

Investigation of pervaporation hybrid polyvinylchloride membranes for the separation of toluene– n-heptane mixtures — case of clays as filler

The transport properties of hybrid membranes based on polyvinylchloride (PVC) was studied for the separation of Toluene– n-Heptane mixtures by pervaporation (PV). Aromatic-alkane mixtures are difficult to fractionate by conventional processes and PV has already been shown as a promising technology in this case. PVC was chosen as starting material in this study because it gathers two key advantages: firstly, it is a technical polymer which is readily available, conversely to speciality polymers often developed for membrane application; secondly, PVCis a polar polymer endowed with a good affinity for aromatic solvents. Thus mixed matrix PVC membranes were studied to determine if it was possible to obtain interesting separation properties from this simple and cheap polymer. We report the results obtained with several types of clay used as fillers to get hybrid PVC membranes. Hence, PVC based mixed matrix membranes were prepared with Maghnite H, Maghnite H +, Wyoming, Kaolin and Nanocor clay particles. It was found that the PVC transport properties could be drastically modified both by the amount and by the type of clay incorporated. According to the fillers incorporated in the polymer matrix, it was shown that the transport properties could be easily tuned either as barrier materials or as Toluene selective membranes with strongly enhanced flux compared to initial PVC membranes.

Controlled Pore Functionalization of Poly(ethylene terephthalate) Track-Etched Membranes via Surface-Initiated Atom Transfer Radical Polymerization

A new method for surface-initiated atom transfer radical polymerization (ATRP) on the technical polymer poly(ethylene terephthalate) (PET) has been developed which allows controlling and estimating the layer thickness of the grafted polymer in the isocylindrical pores of track-etched membranes. After PET surface treatment by oxidative hydrolysis, the bromoalkyl initiator was immobilized on the PET surface in a two-step solid-phase reaction; the isoporous membrane structure was preserved, and the pore diameter was increased from 760 to 790 nm. Poly(N-isopropylacrylamide) (PNIPAAm) was grafted under ATRP conditions from a methanol/water mixture at room temperature. Both monomer concentration and reaction time could be used as parameters to adjust the degree of grafting. Effective grafted layer thickness and its response to temperature were estimated from pure water permeability. All data, especially the high polymer densities (0.37 g/cm3) in the swollen layers at 25 degrees C, indicate that grafted PNIPAAm with a "brush" structure has been achieved. For dry PNIPAAm layer thicknesses on the PET pore walls of up to 80 nm, a temperature-induced swelling/deswelling ratio of approximately 3 had been observed. Reduction of the brush grafting density, via composition of the reaction mixture used in solid-phase synthesis for initiator immobilization, led to an increase of that swelling/deswelling ratio. Further, density and temperature response of the grafted PNIPAAm layers synthesized via ATRP were compared with those obtained in the same membranes by less controlled photografting, leading to lower grafting density and larger gradients in grafted layer density and, consequently, much higher swelling/deswelling ratios (>15).

Nanostructure formation in polymer thin films influenced by humidity

AbstractThe influence of relative humidity (RH) during the film preparation on the surface morphology and on the material distribution of the resulting technical polymer blend films consisting of poly (methyl methacrylate) (PMMA) and poly (vinyl butyral) (PVB) is investigated by atomic force microscopy. Both pure polymers and polymer blends with different compositions of PVB/PMMA dissolved in tetrahydrofuran (THF) were used. Polymer films prepared under dry conditions (RH < 20%) are compared with those that have the same polymer composition but were prepared under increased humidity conditions (RH > 80%). The films consisting of the pure polymers showed a nonporous surface morphology for low‐humidity preparation conditions, whereas high‐humidity preparation conditions lead to porous PVB and PMMA films, respectively. These pores are explained as the result of a breath figure formation. In the case of the polymer blend films containing both polymers, porous or phase‐separated surface structures were observed even at low‐humidity conditions. A superposition of the effects of phase separation and breath figure formation is observed in the case of polymer blend films prepared under high‐humidity conditions. Atomic force microscopy (AFM) images taken before and after the treatment with ethanol as a selective solvent for PVB indicate that PMMA is deposited on top of a PVB layer in the case of the low‐humidity preparation process whereas for high‐humidity conditions the silicon substrate is covered with a PMMA film. Copyright © 2006 John Wiley & Sons, Ltd.

Quantitative characterization of a polystyrene/poly(alpha-methylstyrene) blend by MALDI mass spectrometry and size-exclusion chromatography.

The use of coupled size-exclusion chromatography and MALDI mass spectrometry for quantitative measurement of the composition of technical polymer blends at the molecular level is described. The method is illustrated with a model binary blend consisting of polystyrene and poly(alpha-methylstyrene), both polymers having similar molecular weights and polydispersities. The proposed MALDI data treatment allows determination of the chemical composition of the blend, the molecular weights of the constituents, and the distributions of the homopolymers.

Quantitative analysis of technical polymer mixtures by matrix assisted laser desorption/ionization time of flight mass spectrometry

We report quantitative MALDI-TOF measurements for polydimethylsiloxane (PDMS) of two different molecular weights using the relative ratio of the signal intensities of integrated oligomer distributions for these two molecular weight distributions. By reporting the ratio of intensities of the integrals of two oligomer distributions, we assume that the ionization and desorption efficiencies, crystallization conditions and other factors affecting intensity are similar. Poly(methyl methacrylate) (PMMA-33,000) was mixed with PDMS samples to show whether the presence of another material might affect the desorption efficiency. Quantitative values for the number-average molecular weight (M n), weight-average molecular weight (M w) and polydispersities (D) were calculated using the oligomer distributions. The results show a linear relationship between the analyte concentrations and the signal intensities in the range from 1,000 Da to 10,000 Da, and the desorption efficiency of these two PDMS materials was the same even in the presence of PMMA.