Processing Of Polymer Blends Research Articles

(Invited) Organic Photoelectrochemical Cells for Overall Solar Water Splitting

Solar-driven water splitting to produce hydrogen and oxygen offers a promising avenue for reducing reliance on fossil fuels as hydrogen can be converted into electrical energy using a fuel cell or transformed into useful chemical feedstocks. Despite its potential, the search for cost-effective light harvesting semiconductors suitable for industrial-scale deployment remains a challenge. Organic photoelectrochemical cells (OPECs) utilizing organic semiconductors (OSs) coupled with co-catalysts have recently attracted great attention as alternative photoelectrodes for solar water splitting, considering the unique features of OSs such as precisely tunable optoelectrical properties and solution-processability at low temperatures. However, the conversion efficiency and stability of OPECs (both photocathode and photoanode) have remained particularly poor. Herein, I present high-performance and robust organic photoelectrochemical cells by employing a bulk heterojunction (BHJ) blend of semiconducting polymers as a photoactive layer. The in-depth study using sacrificial agents for photoreduction and photooxidation unveils critical parameters that significantly affect the performance and operational stability of OPECs: (i) rational selection of semiconducting polymer donor and acceptor to generate free charges efficiently and ensure chemical stability upon illumination, (ii) large surface roughness of interlayers to improve interfacial adhesion, and (iii) mitigation of charge accumulation at the interfaces. By leveraging these findings, the optimized polymer BHJ photocathode and photoanode show outstanding performance and robustness compared to previous OPECs, demonstrating a new benchmark of OPECs in solar water splitting. Consequently, this advancement, combined with the simplicity of the polymer blending process, establishes the use of polymer BHJs as a promising route for efficient and scalable solar-driven water splitting technology.

Expanded Polystyrene/Tyre Crumbs Composites as Promising Aggregates in Mortar and Concrete.

A composite material comprising expanded polystyrene (EPS), granulated tyre rubber (GTR), and a compatibilizer is demonstrated as a possible replacement for fine and coarse agglomerates in mortar and concrete systems, respectively. Two different polymer blending processes (solvent/low shear blending and melt/high shear blending) are used, and the resulting composite material utilized as aggregate to replace sand and cement for mortar and concrete block development. Critical properties such as workability, compressive and flexural strengths, water absorption, bulk density, and porosity are measured before and after aggregate replacement. The novel composite material led to significant improvements, boosting compressive strength by 7.6% and flexural strength by 18% when sand was replaced and further increasing compressive strength by 22.2% and flexural strength by 5.26% with cement replacement. However, a decrease in compressive and flexural strength was observed when plain EPS and plain GTR were used separately as aggregate replacements. This work proposes a pathway for the successful reincorporation of difficult-to-recycle materials such as EPS and GTR, otherwise destined for landfill, back into the supply chain for the construction industry. Moreover, this research represents the first reported work where the overall properties of mortar have surpassed those of standard mortar when substituted with recycled EPS or GTR.

In-Line Chemical Composition Monitoring for the Injection Molding Process of Biodegradable Polymer Blends Using Simultaneous Measurement of Near-Infrared Diffuse Reflectance and Transmission Spectra.

In the processing of polymer blends and composites, in-line near-infrared (NIR) spectroscopy enables monitoring of the composition and its composite uniformity and contributes to rapid process development and quality control. However, in the injection molding process, the study of the composition of polymer materials has been delayed due to high-pressure conditions. Our research group developed NIR probes for transmission and diffuse reflectance measurements that can withstand high-pressure and temperature conditions up to 130 MPa and 200 °C. In this research, transmission and diffuse reflectance spectra were measured inline during the injection molding process of polymer blends of poly(lactic acid) and polybutylene succinate adipate. The intensity of each polymer band in the second-derivative spectra exhibited a monotonic increase or decrease in response to changes in the blend ratio. Using transmission and diffuse reflectance spectra as explanatory variables of the partial least squares regression model simultaneously, the model showed high estimation accuracy for the entire region of the blend ratio. Finally, this model was applied to monitor the polymer changeover operation, and the change in the blend ratio in the molded product was successfully estimated in line.

Amphoteric polyelectrolyte ultrafiltration membranes with high permeability property via in-situ modified by PES-N and PES-COOH

Ultrafiltration membrane is one of the most commonly used separation materials for wastewater treatment, due to its low operating pressure, high flux and large specific surface area. In this work, we utilized PES polymer as a polymer precursor to prepare a series of amphoteric polyelectrolyte membrane with different content of amphoteric polyelectrolyte group via simple polymer blending processes. The amphoteric polyelectrolyte groups in amphoteric polyelectrolyte membrane could effectively regulate the retention ability and significantly improve the water flux of membrane. The amphoteric polyelectrolyte membrane with the content ratio of 4:6 (PES-N/PES-COOH) exhibited the highest water flux of 467 Lm−2 h−1 and BSA retention factor of 94.2% than that of other ultrafiltration membranes owning to the abundant porosity and suitable thickness of the top layer. Moreover, the results of static BSA adsorption and flux recovery ratio also proved that the amphoteric polyelectrolyte membrane have a good BSA rejection and antifouling performance. Therefore, these results reveal a simple synthesis and design strategy for constructing the high-performance amphoteric polyelectrolyte membrane for water treatment and provide theoretical and technical guidance for water treatment process based on membrane technology.

Immiscible thermoplastic polymer blends with alternative layered encapsulation structure: Modeling and processing

“Encapsulation” is a common phenomenon during polymer melting processing, which supplied great opportunities for fabricating high-performance polymer products. In this work, two immiscible polymers, high density polyethylene (HDPE) and polyketone (PK), were used for preparing polymer blends with viscous encapsulation structures. Moreover, the effects of interfacial tension, viscosity ratio, and shear rate on the phase morphology evolution of HDPE/PK blends were investigated by numerical simulation and high-pressure capillary extrusion (HCE). Meanwhile, the formation mechanisms of HDPE/PK alternating layered encapsulation structure were explored by tracking the trajectory of PK droplets via numerical simulation. The results show that an alternative layered encapsulation structure of HDPE/PK was formed under the shear rate from 50 to 1000 s−1 with the interfacial tension over 1.35 mN/m. Moreover, it was found that the revealed mechanism in HCE was also applicable to the injection molding process. Therefore, this unique “microstructure-intelligent prediction-control” strategy of polymer blends is suitable for the industrial processing of high-performance polymer blends for desired applications.

Sustainable Construction: Optimization of Road Potholes Repair with Polymer Mix Aggregates

The roads in Banyuwangi city have sustained considerable damage; the asphalt supply has not met the need because 45% of the roads are built using gravel and soil. Another problem is related to plastic, which is a type of waste that is difficult to recycle. Thereby, to solve these two problems, we conducted research in making polymer-modified asphalt by utilizing food packaging plastic waste. The process followed the standard specification of Highway Construction Division 6, revision 3: the polymer blending process was performed when the hot asphalt mixing temperature was 145℃-155℃. The research results found that the variation of asphalt content used in the mixture was 4.5%, 5%, 5.5%, and 6%. Moreover, the optimal asphalt content was 6%. The polymer was mixed with the optimal asphalt content of 0%, 1%, 2%, 3%, and 4%. The test results showed that the optimal polymer content was 1% polymer. For optimizing and repairing road potholes, polymer asphalt with asphalt content of 6% mixed and 1% polymer can be chosen as a solution. Polymer-modified asphalt had a high stability value, which was 1181.9 kg. The discovery of this mixture of materials is very appropriate for sustainable road construction in Indonesia.

OPTIMIZATION OF POLYMER AGGREGATE WITH SAND AND ASPHALT MIX FOR ROAD POTHOLES REPAIR

The roads in Banyuwangi city have sustained considerable damage; the asphalt supply has yet to meet the need because 45% of the roads are built using gravel and soil. Another problem is related to plastic, a type of waste that is difficult to recycle. To solve these two problems, we conducted research in making polymer-modified asphalt by utilizing food packaging plastic waste. The process followed the standard specification of Highway Construction Division 6, revision 3: the polymer blending process was performed when the hot asphalt mixing temperature was 145°C- 155°C. The research results found that the variation of asphalt content used in the mixture was 4.5%, 5%, 5.5%, and 6%. Moreover, the optimal asphalt content was 5.3%. The polymer was mixed with the optimal asphalt content of 0%, 1%, 2%, 3%, and 4%. The test results showed that the optimal polymer content was 0.5%, with a maximum of 1%. Polymer-modified asphalt had a high stability value of 23.64% greater than conventional. In addition, the air cavity value in the mixture was 5.74% greater than conventional asphalt. The discovery of this mixture of materials is very appropriate for sustainable road construction in Indonesia.

Fabrication, morphological, mechanical and biological performance of 3D printed poly(ϵ-caprolactone)/bioglass composite scaffolds for bone tissue engineering applications

Several techniques, such as additive manufacturing, have been used for the manufacture of polymer-ceramic composite scaffolds for bone tissue engineering. A new extruder head recently developed for improving the manufacturing process is an experimental 3D printer Fab@CTI that enables the use of ceramic powders in the processing of composite materials or polymer blends. Still, the manufacturing process needs improvement to promote the dispersion of ceramic particles in the polymer matrix. This article addresses the manufacture of scaffolds by 3D printing from mixtures of poly(ϵ-caprolactone) (PCL) and a glass powder of same composition of 45S5Bioglass®, labeled as synthesized bioglass (SBG), according to two different methods that investigated the efficiency of the new extruder head. The first one is a single extrusion process in a Fab@CTI 3D printer, and the other consists in the pre-processing of the PCL-SBG mixture in a mono-screw extruder with a Maddock® element, followed by direct extrusion in the experimental Fab@CTI 3D printer. The morphological characterization of the extruded samples by scanning electron microscope showed an architecture of 0°/90° interconnected struts and suitable porosity for bone tissue engineering applications. Scaffolds fabricated by two methods shows compressive modulus ranging from 54.4 ± 14.2 to 155.9 ± 20.4 MPa, results that are compatible to use in bone tissue engineering. Cytotoxicity assays showed non-toxic effects and viability for in vitro MG-63 cell proliferation. Alizarin Red staining test showed calcium deposition in all scaffolds, which suggests PCL/SBG composites promising candidates for use in bone tissue engineering. Results of cell morphology suggest more cell growth and adhesion for scaffolds fabricated using the pre-processing in a mono-screw extruder.

Wax and bentonite blends for prototyping industrial clay development: preliminary results

Wax and bentonite blends for prototyping industrial clay development: preliminary results

Polydimethylsiloxane Microdomains Formation at the Polythiourethane/Air Interface and Its Influence on Barnacle Release.

In this study, polydimethylsiloxane (PDMS)/polythiourethane (PTU) composite reinforced with tetrapodal shaped micro-nano ZnO particles (t-ZnO) was successfully produced by a versatile, industrially applicable polymer blending process. On the surface of this composite, PDMS is distributed in the form of microdomains embedded in a PTU matrix. The composite inherited not only good mechanical properties originating from PTU but also promising fouling-release (FR) properties due to the presence of PDMS on the surface. It was shown that the preferential segregation of PDMS domains at the polymer/air interface could be attributed to the difference in the surface free energy of PDMS and PTU. The PDMS microdomains at the PTU/air interface significantly reduced the barnacle adhesion strength on the composite. Both the pseudo- and natural barnacle adhesion strength on the composite was approximately 0.1 MPa, similar to that on pure PDMS. The pseudo-barnacle adhesion on reference surfaces AlMg3 and PTU reached approximately 4 and 6 MPa, respectively. Natural barnacles could not be removed intact from AlMg3 and PTU surfaces without breaking the shell, indicating that the adhesion strength was higher than the mechanical strength of a barnacle shell (approximately 0.4 MPa). The integrity of PDMS microdomains was maintained after 12 months of immersion in seawater and barnacle removal. No surface deteriorations were found. In short, the composite showed excellent potential as a long-term stable FR coating for marine applications.

Effects of Injection Molding Parameters and their Interactions on Mechanical Properties of PMMA/PC Blend

A combination of Polycarbonate (PC) material and Polymethylmethacrylate (PMMA), fabricated using an injection molding machine, has been investigated to determine its advantages, as studied in Ref. 1). This paper aims to investigate the optimization of PMMA/PC blend for both tensile yield strength and impact strength. Furthermore, interaction effects of process conditions on mechanical properties including tensile yield strength and impact strength of PMMA/PC blend by injection molding process are interpreted in this study. Tensile and impact specimens are designed following ASTM, type V, and are fabricated by injection molding process. The processing conditions such as melt temperature, mold temperature, packing pressure, and cooling time are applied; each factor has three levels. As a result, in comparison with optimization of separated responses, mechanical properties of PMMA/PC are found to decrease when optimizing both tensile and impact strengths simultaneously. The melt temperature is found to be the most significant interaction parameter with the mold temperature and packing pressure. In addition, there is more interaction between the mold temperature and cooling time. This investigation provides a useful understanding of the control of injection molding processing of polymer blends in optical application.

Correlative analysis between solid-state NMR and morphology for blends of poly(lactic acid) and poly(butylene adipate-co-butylene terephthalate)

Morphological changes in polymer blending process were investigated using integrated analyses by solid-state NMR and magnetic relaxation. The study examined previous reported mechanical properties of polymer blends incorporating poly(lactic acid) (PLA) and poly(butylene adipate-co-butylene terephthalate) (PBAT) over a range of compositions, along with a crosslinking reagent. The X-ray diffraction (XRD) and the differential scanning calorimeter (DSC) results showed that the crystallinity of PLA decreased with increasing the PBAT content. According to the integrated analysis data and imaging by micro-focus X-ray computed tomography (CT), polymer tensile properties were dominated by interfacial affinity between the molecular mobilities of PLA and PBAT; depending on the blending ratio, the polymer morphology changed from a discontinuous “sea-island” form to a bicontinuous morphology. Addition of a crosslinking reagent was observed via X-ray CT to homogenize the PLA and PBAT blend at the micron length scale, even though both polymers were still heterogeneous at the nanoscale as elucidated by NMR analysis. As well as the morphological change in micro scale, the molecular mobility changes of the total polymer blend system, which could be evaluated by the integrated solid-state NMR analyses, brought about greater elongation at the break point in dynamic tensile testing.

Description of the Droplet Size Evolution in Flowing Immiscible Polymer Blends.

Control of the phase structure evolution in flowing immiscible polymer blends during their mixing and processing is fundamental for tailoring of their performance. This review summarizes present state of understanding and predictability of the phase structure evolution in flowing immiscible polymer blends with dispersed structure. Results of the studies of the droplet breakup in flow, important for determination of the droplet breakup frequency and of the size distribution of the daughter droplets, are reviewed. Theories of the flow-induced coalescence providing equations for collision efficiency are discussed. Approximate analytic expressions reliably describing dependence of the collision efficiency on system parameters are presented. Available theories describing the competition between the droplet breakup and coalescence in flow are summarized and approximations used in their derivation are discussed. Problems with applicability of available theories on prediction of the droplet size evolution during mixing and processing of immiscible polymer blends, which have not been broadly discussed so far, are addressed.

Attaining Melt Processing of Complementary Semiconducting Polymer Blends at 130 °C via Side-Chain Engineering

Complementary semiconducting polymer blends (c-SPBs) have been proposed and tested to achieve melt-processed high-performance organic field-effect transistors (OFETs). Prior to this study, melt processing requires temperatures as high as 180 °C. To implement this technique into low-cost and large-area thin-film manufacturing for flexible organic electronics, semiconducting materials meltable at temperatures tolerable by ubiquitous plastic substrates are still needed. We report here the design and melt processing of a c-SPB consisting of a matrix polymer (DPP-C5) and its fully conjugated analogue. By utilizing a siloxane-terminated alkyl chain and a branched alkyl chain as solubilizing groups, the matrix polymer DPP-C5 presents a melting temperature of 115 °C. The resulting c-SPB containing as low as 5% of the fully conjugated polymer could be melt-processed at 130 °C. The obtained OFET devices exhibit hole mobility approaching 1.0 cm2/(V s), threshold voltages below 5 V, and ION/IOFF around 105. This combination of efficient charge-carrier transport and considerably low processing temperatures bode well for melt processing of semiconducting polymer-based organic electronics.

Reactive extrusion of bio-based polymer blends and composites – Current trends and future developments

Reactive extrusion is a cost-effective and environmentally-friendly method to produce new materials with enhanced performance properties. At present, reactive extrusion allows in-situ polymerization, modification/functionalization of polymers or chemical bonding of two (or more) immiscible phases, which can be carried out on commonly used extrusion lines. Although reactive extrusion has been known for many years, its application for processing of bio-based polymer blends and composites is a relatively new direction of scientific research. This work presents a literature review on recent advances in the processing of bio-based polymer blends and composites via reactive extrusion. We described compatibilization mechanisms for different types of biodegradable polymeric materials based on: (i) aliphatic polyesters, (ii) aliphatic polyesters/starch and (iii) aliphatic polyester/natural rubber systems. A special attention was focused on conventional and dynamic cross-linking of bio-based polymer blends and composites as an effective way to prepare new materials with unique properties e.g. biodegradable thermoplastic elastomers or shape-memory materials. Advantages and limitations affecting future trends in development of biodegradable polymer blends and composites reactive extrusion are also discussed.

Controlling the continuity and surface migration of conductive poly(ether-block-amide) in melt processed cast-film blends

Polymer migration to the film surface during the melt processing of polymer blends is an important phenomenon, but has been limited in study. In this work, melt extruded cast films of conductive poly (ether-block-amide) (PEBA) with low-density polyethylene (LDPE) and polystyrene (PS) are prepared and the critical roles of phase continuity, interfacial tension and viscosity on PEBA surface migration are studied. When blended with high viscosity LDPEs, PEBA tends to migrate to the film surface, but significant surface enrichment only occurs at high PEBA continuities (typically > 50%). A possible surface migration mechanism based on the draining of PEBA through the connected networks is proposed and the migration process is facilitated by high interfacial tension. In compatibilized LDPE/PEBA and in PS/PEBA, the surface migration of PEBA is fully suppressed even at high continuity levels due to the low interfacial tension between the components. The surface resistivities of the binary blends are critically determined by the continuity of PEBA with a limited influence from surface enrichment. It appears that the continuity threshold to influence surface resistivity is lower than that for surface migration. A ternary LDPE/PS/PEBA blend with double percolation can simultaneously reduce the film surface resistivity and control PEBA surface migration by confining PEBA within a continuous low interfacial tension PS phase.

Zone‐Annealing‐Assisted Solvent‐Free Processing of Complementary Semiconducting Polymer Blends for Organic Field‐Effect Transistors

AbstractSemiconducting polymer thin films, which are usually formed by solution‐casting from their organic solutions, are critical in the development of flexible and printed electronics. To seek out a method that can further improve the electrical properties of semiconducting polymers and also be industrially applicable is of vital significance. In this study, the impact of zone annealing on the charge‐transport properties of diketopyrrolopyrrole‐based complementary semiconducting polymer blends in field‐effect transistor devices is investigated. An average mobility increased from 0.66 to 0.87 cm2 V−1 s−1, with a highest of 1.6 cm2 V−1 s−1, is observed. It is also demonstrated that zone annealing can be integrated with melt processing to realize a solvent‐free process for polymer thin films for organic field‐effect transistors (OFETs) and achieve improved charge transport characteristics with a record mobility of 0.54 cm2 V−1 s−1 among melt‐processed OFETs. This work provides an alternative, green, and sustainable processing method to advance polymer‐based organic electronics.

Reactive blends based on polyhydroxyalkanoates: Preparation and biomedical application

Polyhydroxyalkanoates (PHAs) are a class of natural polyesters as carbon and energy reserves by >300 species of microorganisms. They are fully biodegradable, biocompatible and piezoelectric biopolymers that have attracted much attention recently as the biomaterial of choice for medical applications. However, the toughness, processability and hydrophilicity of PHAs need to tune to expand their applications as tissue engineering scaffolds or drug delivery systems. Reactive polymer blending is one of the most economic and versatile way to produce materials combining the desired properties via forming the compatibilizing agents in situ or inducing the chemico-physical interactions between polymer blends. This review focuses on the PHAs-based reactive blends aiming to present a brief introduction to the mechanism of reactive polymer blending technique, including the formation of H-bonding, branching/crosslinking copolymers, graft copolymers or complex copolymers during polymer blending process.

Prediction of the Phase Structure Evolution during Processing of Polymer Blends. Results and Problems

SummaryThe paper summarizes state of art in the description of the droplet breakup, coalescence, and competition between them in flowing immiscible polymer blends. It has been shown that, in contrast to the conditions for the start of droplet breakup, knowledge of the dependence of the droplet breakup frequency on system parameters is quite limited. It has been demonstrated that the switch between expressions for the matrix drainage between spherical and highly deformed droplets leads to a reasonable description of the flow induced coalescence. This method makes it possible to include the effect of the matrix elasticity into the calculation of the probability of coalescence. The analysis of the competition between the droplet breakup and coalescence leads to the conclusion that knowledge of the mechanism and frequency of the droplet breakup is essential for at least qualitative prediction of the droplet size dependence on system parameters. The article addresses main features of flowing polymer blends, not adequately reflected in available theories.

Phase diagrams of thermally stable, polymer‐dispersed liquid crystals: Exploring the impact of chain length and chemical structure

Polymer‐dispersed liquid crystals (PDLCs) have garnered significant interest and motivated the investigation of the phase behavior of thermally stable smectic liquid crystals (LCs) via thermally induced phase separation (TIPS). In this study, we examined a series of two, biphenyl‐based smectic LCs suitable for high temperature polymer blend processing. Phase diagrams for LC/polystyrene (PS) blends at various compositions (0–60 wt%) were constructed. Less than 15 wt% of 8B8 (1,1′‐biphenyl‐4,4′‐diyl dioctanoate) LC in PS led to good polymer miscibility, while phase separation was induced at concentrations higher than 15 wt%. The LC concentration at saturation decreased with increasing aliphatic chain length. We also investigated the chain length (C6‐C16) effect on the PS glass transition temperature (Tg) at the LC saturation point. The Tg increased with increasing chain length due to reduced plasticization. We further examined the role of chemical structure (relatively less polar ether vs. more polar ester) on the phase diagram regions and the Tg of the nonpolar PS matrix, respectively. It is anticipated that these LC/PS phase diagrams will benefit elevated temperature processing for TIPS by highlighting the role of LC chemical structure and chain length on blend morphology. POLYM. ENG. SCI., 56:388–393, 2016. © 2016 Society of Plastics Engineers