Plastic Compatibility Research Articles

Impacts of Waste Rubber Products on the Structure and Properties of Modified Asphalt Binder: Part I—Crumb Rubber

The issue of forming a reliable and sustainable structure of crumb-rubber-modified binder is an important scientific and technical task. The quality of this task will increase the technical and economic efficiencies of road construction materials. This work is dedicated to developing a scientifically justified method of directed thermomechanical devulcanization, which ensures the solubility of the crumb rubber in the complex structure of a polydisperse composite material, preventing the formation of aggregates consisting of unsaturated crumb rubber particles, whose elastic aftereffect causes intensive cracking, especially during low-temperature road operations. The novelty in the first part of this article is due to the fact that, for the first time, the quantitative ratio of the polymer component in the crumb rubber was experimentally determined. The ratio of the polymer component to the total content of the other rubber components in the crumb rubber (CR) was determined to be, on average, 93.3 ± 1.8%. The stabilities of the compositions of crumb rubber from different batches were experimentally studied. The nature of the polymer component in the crumb rubber was determined. A hypothesis was formulated to obtain a thermodynamically stable and sustainable binder modified with crumb rubber. To evaluate the compatibility of hydrocarbon plasticizers with the studied CR samples, the following semi-empirical and thermodynamic compatibility parameters were calculated: Hildebrand solubility parameters based on evaporation energy and surface tension, Barstein’s compatibility parameter |X|, Traxler coefficient, and the mass ratio of paraffin naphthene:asphaltenes. It was shown that for the substances under study, it is advisable to justify the choice of plasticizer based on chemical compatibility criteria. It was established that a supramolecular plasticization mechanism occurs in the “hydrocarbon plasticizer–crumb rubber” systems under consideration. In the development of the crumb-rubber-modified binder, it was found that the use of activated crumb rubber (ACR) from large tires does not ensure the achievement of a stable and resilient structure of the crumb-rubber-modified bitumen.

Conventional and Green Rubber Plasticizers Classified through Nile Red [E(NR)] and Reichardt’s Polarity Scale [ET(30)

After a survey on polymer plasticization theories and conventional criteria to evaluate polymer–plasticizer compatibility through the solubility parameter, an attempt to create a polymer–plasticizer polarity scale through solvatochromic dyes has been made. Since Reichardt’s ET(30) dye is insoluble in rubber hydrocarbon polymers like polyisoprene, polybutadiene and styrene–butadiene copolymers and is not useful for the evaluation of the hydrocarbons and ester plasticizers, the Nile Red solvatochromic dye was instead used extensively and successfully for this class of compounds. A total of 53 different compounds were evaluated with the Nile Red dye and wherever possible also with Reichardt’s ET(33) dye. A very good correlation was then found between the Nile Red scale E(NR) and Reichardt’s ET(30) scale for this class of compounds focusing on diene rubbers and their typical hydrocarbons and new ester plasticizers. Furthermore, the E(NR) scale also shows a reasonable correlation with the total solubility parameter calculated according to the Van Krevelen method. Based on the above results, some conclusion was made about the compatibility between the diene rubbers and the conventional plasticizers, as well as a new and green plasticizer proposed for the rubber compounds.

Evaluation of the compatibility of energetic nitrocellulose/plasticizer blends through molecular dynamics simulation

ABSTRACT The compatibility of binders and plasticizers has a significant influence on the properties of polymer-bonded explosives. Molecular dynamics was employed to explore the compatibility between nitrocellulose (NC) with different nitrogen contents and three azido plasticizers by the solubility parameter, mean square displacement, binding energy, radial distribution function (RDF), radius of gyration, and volume distribution. With the increase of nitrogen content, the solubility parameters of NCs decreased and were in good accordance with the reporting results. 1,5-diazido-3-oxapentane (AZDEGDN) had a stronger diffusion ability in NC than that of the other two plasticizers. The introduction of the RDF suggested that the strong interaction between the NC and AZDEGDN mainly came from the hydrogen bonds between hydroxyl groups of NC molecules and the azido in plasticizers. AZDEGDN increased the free volume in NC/AZDEGDN blends, and the mobility of the molecular chains was enhanced, thus the radius of gyration of the NC molecular chains increased. The comprehensive performances demonstrated that AZDEGDN had a strong plasticizing effect on NC because of hydrogen bonds, presenting a potential option for optimizing explosives formulations.

Effects of Bulk LPSO Phases on Mechanical Properties and Fracture Behavior of As-Extruded Mg-Gd-Y-Zn-Zr Alloys

Despite the consensus on the constructive effect of LPSO (long-period stacking-ordered) phases, the true effect of bulk LPSO phases on strengthening and toughening in deformed magnesium alloys is still controversial. This article, which introduces the alloys Mg-8Gd-4Y-0.6Zn-0.5Zr, without bulk LPSO phases, and Mg-8Gd-4Y-1.6Zn-0.5Zr, containing bulk LPSO phases, details a systematically comparative analysis conducted to clarify the true contribution of bulk LPSO phases to the properties of as-extruded alloys. The results indicate that bulk LPSO phases significantly improve strength by refining grain sizes remarkably. But contrary to expectations, bulk LPSO phases themselves only provide a small strengthening effect and deteriorate plasticity, ascribed to the poor compatible plastic deformation of bulk LPSO phases. More importantly, this work may offer new insights into the strengthening and toughening of LPSO phases for further research and engineering applications of this series of alloys. Additionally, an example of a design strategy for Mg-Gd-Y-Zn alloys with superior strength and excellent plasticity is proposed at the end of this article.

Cellulose-based polypropoxy ether carboxylates as highly compatible, effective, and migration-resistant plasticizers for poly (lactic acid)

The utilization of cellulose for enhancing the strength, the PLA has received significant attention, however, poor interfacial compatibility of solid cellulose with PLA matrix still hinders their broader application. Herein, highly compatible cellulose-based polypropoxy ether carboxylates (CPPEC) were firstly manufactured via propoxylation of cellulose and following esterification with acetic acid, butyric acid, as well as oleic acid, respectively. Liquid CPPEC delivered excellent performances to PLA, especially, the values of elongation at break and low-temperature resistance of PLA blended with cellulose-based polypropoxy ether acetate (PLA/CPPEA) were respectively increased by 630.9 % and 146.3 % compared with those of neat PLA due to the synergistic effect of propyl and methyl groups in CPPEC with PLA matrix. Additionally, migration resistance of PLA/CPPEA increased 14.3 and 11.2 times, respectively, compared with those of PLA specimens blended with epoxidized soybean oil and dioctyl phthalate. All findings suggest that the CPPEC is suitable for large-scale application in the PLA industry.

A Novel Multi-Channel Tandem Applicator for Direction Modulated Brachytherapy

Intracavitary brachytherapy is a fundamental part of the treatment of cervical cancer that would be applied as boost therapy. However, the coverage of non-uniform targets is very challenging for this technique when dealing with the lateral extension of tumor, particularly when the tumor is too far superiorly to be covered by radiation dose from the ovoids or rings. In such situations, the conventional (single channel) tandem applicator would need to effectively provide the entire dose to the region yet have a very limited capacity for the intensity modulation due to the isotropic nature of radiation from the 192Ir HDR source. This limitation would require development of state-of-the-art interstitial-intercavitary applicators. In this study we aim to introduce a novel multi-channel tandem applicator design in alignment with the direction modulated brachytherapy (DMBT) concept to address this important issue. The novel multi-channel tandem applicator was designed using GEANT4 Monte Carlo simulations to consist of a base, made of MR compatible PEEK plastic, with a diameter of 6.5 mm and 19 channels each 1.1 mm in diameter, and in a honeycomb arrangement. The design also incorporated 18 iridium wires with a diameter of 0.9 mm that can actively enter the channels to provide intensity modulation at desired directions. A dosimetry study was then performed with different configurations of the 192Ir HDR source, also 0.9 mm in diameter, and up to 18 iridium wires inside the base. While offering the symmetrical dose distribution of the conventional tandem, the honeycomb design could produce a variety of directional dose distributions with different degree of extended lateral coverage. Additionally, this novel design with the configuration of 18 iridium wires inside the base covering the HDR source could reduce the radiation dose to approximately 15 % behind the shielded side at 1 cm from the tandem compared to the unshielded side. The results indicated that the honeycomb DMBT tandem design, as a noninvasive intracavitary approach, could be a promising solution for covering targets with lateral asymmetry/extension. Utilizing high-density material such as tungsten as the base material could reduce the radiation leakage through the base, improve the intensity modulation and hence lateral coverage.

Optimization of Crumb Rubber Modified Binder Formulation through Compatibility Analysis.

The research is devoted to developing the production of crumb rubber-modified bitumen with improved stability. It has been established that the most suitable semi-empirical coefficient for determining the compatible plasticizer to crumb rubber is based on the ratio of paraffin-naphthenic compounds to resinous-asphaltene compounds. With the help of differential scanning calorimetry, temperature regimes of crumb rubber destruction and preparation of rubber-containing components (210 °C) were studied and determined. It was established that determining the dynamic viscosity of hydrocarbon concentrates with crumb rubber on a rotary viscometer is not applicable due to elastic components, making it difficult to measure and obtain reliable data. The most suitable method is the shear viscosity method. Using fluorescent microscopy, it was established that the formation of a branched structure of crumb rubber is achieved in the waste industrial oil, indicating devulcanization processes. It was found that hydrocarbon plasticizer with high naphthenic oil content is the most compatible with crumb rubber. Synthetic wax was found to be of greater interest as a devulcanizing/stabilizing agent, and its application in an amount of 3% allows the formation of a stable CRMB structure and stabilizes the devulcanization process.

Efficient biobased oligomeric plasticizers from the renewable biomonomers, glycerol and adipic acid

With the recognition that traditional phthalate plasticizers readily migrate from a polymer matrix into which they have been incorporated, have become widespread environmental pollutants and pose risks to human health, the development of new, effective, nontoxic, nonmigrating plasticizers has gained urgency. A focus has been the generation of plasticizers from renewable, inexpensive, nontoxic biobased precursors. Many small molecule plasticizers have been prepared from readily-available bioprecursors. However, the most promising are branched oligomeric materials. Fully compatible oligomeric plasticizers do not migrate from a polymer matrix. Highly branched materials are effective in increasing free volume and display good plasticizing impact. Using new technology that permits the generation of hyperbranched poly(ester) without gelation and with control of molecular weight and endgroup identity, oligomeric materials have been prepared from the nontoxic biomonomers, glycerol and adipic acid. The monomers are readily available at modest cost. The oligomers may be obtained in a simple one-step process and function as very effective plasticizers for polymeric materials.

Inhibiting cracking and improving strength for additive manufactured Al CoCrFeNi high entropy alloy via changing crystal structure from BCC-to-FCC

Hot cracking in laser powder bed fused (LPBF) AlxCoCrFeNi high entropy alloys (HEAs) plague the production of high strength parts. Here we show that the body-centered cubic (BCC) phase with very high hardness (∼670 HV) in LPBF printed AlxCoCrFeNi(x = 1, 0.7) HEAs causes cracking due to the plastic incompatibility between grain boundaries. To mitigate this, we propose a BCC to face-centered cubic (FCC) transformation strategy in the AlxCoCrFeNi HEAs to inhibit cracking and found that the Al0.5CoCrFeNi alloy (i.e., when x = 0.5) with a single FCC crystal structure possess low cracking sensitivity and well intergranular plastic compatibility, accompanied with decreased residual stress confirmed by using X-ray diffraction testing. The mechanical properties of the LPBF printed Al0.5CoCrFeNi HEA can be further enhanced by precipitation heat treatment. Scanning electron microscope/ transmission electron microscopy analysis show that nano-sized B2, L12 and σ phases precipitated from FCC Al0.5CoCrFeNi HEA when aged at 700 °C for 1 h. The ultimate tensile strength (UTS) increases from 899 MPa (as-print) to 1552 MPa (aged) with the elongation decreasing from 35.6 % (as-print) to 7.1 % (aged) due to the Orowan bypass mechanism of nano-precipitates. An increased aging temperature to 800–1000 ℃, decreases the UTS while increases the elongation, accompanied by the L12-to-B2 transformation and B2 phase coarsening. The deformation mechanism is mainly dominated by dislocations and stacking faults in the Al0.5CoCrFeNi HEA sample.

A comparative assessment of the use of suitable analytical techniques to evaluate plasticizer compatibility

AbstractThe evaluation of novel phthalate‐free plasticisers for PVC formulations is hindered by the lack of a reliable quantitative method for testing plasticizer exudation from PVC formulations. Two methods of improving upon the ASTM D3291 exudation test have been trialed using ATR‐FTIR and GC–MS. The results of these methods are compared alongside a study of the glass transition temperatures (Tg) by dynamic mechanical analysis (DMA). FTIR is found to be unsuitable for determining plasticizer exudation as the method is not sufficiently sensitive to detect small changes in plasticizer distribution. Carbonyl peak positions in unstressed samples are instead investigated to determine the strength of interaction between the plasticisers and PVC chain. GC–MS is successfully used to quantify plasticizer exudation that could not be observed visually or by FTIR. Furthermore, these methods show limited correlation to each other, which highlights the importance of testing multiple aspects of compatibility when developing novel plasticisers for use in PVC.

Interface feature via key factor on adhesion of CrN multilayer and alloy substrate

CrN multilayer coatings were deposited on 316L stainless steel, which has a high modulus, and TC4 titanium alloy, which exhibits the opposite properties, to reveal adhesion mechanisms and deformation behavior of the coating/substrate systems. Because of the different microstructures, the coatings’ morphologies varied from single polygon on the 316L to polygon and rectangle-mixed shapes on the TC4. On 316L, the cracks initiated from the Cr/CrN interfaces and propagated into the CrN layer, which stopped within it. On TC4, the cracks propagated through the CrN layer. The coherent nanocrystal interfaces in CrN/Cr/316L exhibited orderly bending, revealing the presence of strong interfacial bonds. The undeformed interfaces in CrN/Cr/TC4 indicated incompatible deformation and weak bonds. This was consistent with the fact that on TC4, the Cr/CrN interface tensile stress was high, at 123.1 GPa, while it was lower on 316L, at 99.3 GPa. The Wp/We ratio of CrN/TC4, namely 1.94, was lower than that of CrN/316L, namely 2.61. This indicated that CrN/316L had a high energy-absorption ability because of compatible plastic deformation. The failure mechanism observed between the coating/TC4 was attributed to the differences in their moduli, which led to incompatible deformation, high interfacial tensile stress, and low absorption capability for external work.

Combined effects of plasticizers and D-lactide content on the mechanical and morphological behavior of polylactic acid

Nowadays, research into environmentally friendly, renewable materials is the focus of materials science. One of the best candidates for these purposes is polylactic acid (PLA), whose properties are determined mainly by its D-lactide content. PLA is often plasticized to achieve proper toughness. Our aim was to investigate the combined effects of plasticizers and D-lactide content on PLA. We investigated two different plasticizers: oligomeric lactide acid (OLA) and dioctyl adipate (DOA). An internal mixer was used to prepare the compounds, and then sheets were prepared by hot pressing. After mechanical and morphological analyses, we found that tensile strength and modulus of neat PLAs and PLA-OLA compounds decreased almost linearly with increasing D-lactide content. The mechanical properties of PLA-DOA compounds depended far less on D-lactide content than in the case of PLA-OLA compounds. Plasticizers promote the crystallization of crystallizable PLAs by their chain mobilizing effect—we obtained a higher crystalline fraction. The latter effect reduces the impact of the plasticizing effect of plasticizers in the product. The compatibility and dispersibility of plasticizers also have a significant effect on the properties of the materials. OLA is more compatible with PLA than DOA, which resulted in better plasticization, but caused more defects in the crystallites, thus reducing the crystalline melting temperature, and so the processing temperature of the compound containing plasticizers.

Microstructure-based intergranular fatigue crack nucleation model: Dislocation transmission versus grain boundary cracking

Intergranular fatigue crack nucleation has been reported to occur commonly at high angle grain boundaries (HAGBs) but seldom at low angle GBs (LAGBs) during persistent slip band (PSB)-GB interactions. However, the mechanistic understanding of the role of GB misorientation angles in affecting the GB fatigue cracking remains limited due to the lack of quantitative descriptions. Here a theoretical framework based on the competition between dislocation transmission across GB and GB cracking is established for investigating the GB fatigue crack nucleation. We show that, HAGBs usually provide higher resistances to dislocation transmissions compared with LAGBs, causing a more significant dislocation pile-up and stress concentration, which facilitates the GB crack nucleation. But the quantitative analysis indicates that even at HAGBs with poor plastic compatibility, the critical stress of GB cracking is much larger than the critical transmission stress. This demonstrates the crucial role of GB fatigue damage accumulation, which is associated with PSB extrusion growth, in promoting GB crack nucleation. In this study, the critical stress of dislocation transmission is derived in terms of the energy balance, and the nucleation criterion of GB crack is formulated using the fracture theory, both of which display the dependence on GB misorientation angles and grain sizes. It is found that the GB fatigue cracks preferentially nucleate at HAGBs with poor plastic compatibility and large grain sizes. The competition between dislocation transmission and GB cracking at varying fatigue cycles are also discussed. This theoretical framework offers quantitative analyses for the GB crack nucleation during PSB–GB interactions, clarifies the role of microstructures in affecting the critical cycles of GB cracking, and might offer important guidelines for designing fatigue-resistant metallic materials.

Evaluating the solid solution, local chemical ordering, and precipitation strengthening contributions in multi-principal-element alloys

Numerous theoretical and experimental studies suggest that the chemical ordering microstructure plays an important role for the strength and plastic deformation in the multi-principal-element alloy (MPEA). Despite the importance of this fact has been well confirmed, little is known about the influence of chemical ordering degree from the atomic scale to nano scale for the nanocrystal MPEA over a wide grain size range. In the present work, considering the abnormal local stacking fault energy originated from the heterogeneous chemical element concentration, the modified Hall-Petch relationship is elaborately established in MPEA, quite different from the traditional alloys. Additionally, the effects of the solid solution, local chemical ordering, and precipitation on the strengthening contribution and strain partition are evaluated. The increase of the chemical ordering degree improves the stacking fault energy and deformation gradient, as well as microrotation field. This trend leads to the yield strength owing to the formation of the slender shear bands. The geometry of the ordered structure is deformed and twisted to a certain extent, for the compatible plastic deformation. This work gives the atomic understanding of chemical-ordering-degree dominated strengthening mechanisms, to develop the strong and ductile MPEAs with desired properties. Data availability statementThe data that support the findings of this study are available from the corresponding author upon reasonable request.

PO18: An Efficient and Reproducible Autoradiography Technique for HDR-Gynecological Applicators Commissioning

<h3>Purpose</h3> High Dose Rate (HDR) brachytherapy commissioning of Elekta's gynecological (Gyn) applicator sets include a large inventory of CT/MR compatible plastic, applicator tubes of varying shapes and sizes. This often present a challenge to the efficiency of source autoradiography - an essential test to determine and verify final dwell position of the HDR source and its positioning/stepping accuracy. We present a technique of acquiring radiograph-autoradiograph combinations of HDR-Gyn applicators that allows testing of several applicators simultaneously, in a rigid and reproducible set-up. <h3>Materials Methods</h3> Elekta provides x-ray catheter (marker) sets as a required accessory to verify source positioning inside Gyn applicators. Once the markers are calibrated & Final Marker Position (FMP) characterized, using Elekta's Source Position Check Ruler & CT-scans, the technique of radiograph-autoradiograph superposition is recommended for determination of final dwell position (FDP) & verification of source positioning accuracy. To ensure a rigid & reproducible set-up, template trays to hold multiple applicator tubes & Gafochromic EBT3 film for recording multiple radiographs in unison were built using Styrofoam. Channels were carved in styrofoam creating tight narrow groves fitting applicators in place. Applicators were taped with tips laid flat & flush with the film secured to styrofoam base independently. Primary advantage of using styrofoam is that it offers no backscatter to radiography as well as gamma photons from the Ir-192 source. Additionally, it is readily available and easy to work with. Each tray held 4-6 applicators with markers allowing a simultaneous radiograph acquisition, &∼ 5 cm lateral spacing enabled independent images. Truebeam^TM Linear accelerator was used for radiography. Multiple pre-prepared template trays with applicators were exposed at a source-to-film-distance of 100 cm with 400 monitor units using 2.5 MV imaging beam. This technique provided best visualization of the plastic applicator & marker on a gafochromic EBT3 film. Once the multiple-applicator-radiograph is acquired, templates were transported to adjacent HDR suite, set on a rigid couch, markers carefully removed & transfer tube connected for acquisition of autoradiograph coincident with recently acquired radiograph, using Flexitron afterloader. For Ir-192 source's autoradiograph, a 10-15 seconds dwell time is adequate to darken film with marker visualization reasonably intact for analysis. Pre-prepared templates and availability of personnel allowed simultaneous use of linear accelerator & afterloader, for radiograph & autoradiograph acquisition, adding further efficiency. Source positioning & stepping accuracy was verified by coincidence of center of darkening at the exposed dwell-position & center of visualized markers, on a viewbox illuminator. <h3>Results</h3> Using techniques and workflow developed, 60 CT/MR compatible HDR-Gyn plastic applicators were commissioned. Autoradiography-radiography superposition with x-ray markers enabled verification of Elekta specified distances between the outer tip of the IU/ovoid tubes, inner tip & the final dwell position, & HDR source positioning & stepping accuracy within 1 mm. Figure 1-A shows Styrofoam templates with multiple channels for affixing applicators over EBT3 Gafochromic film for radiography, 1-B is HDR room setup for autoradiography and 1-C shows images of multiple different applicator tubes depicting the radiograph-autoradiograph overlay with marker visualization and HDR source positioning. <h3>Conclusion</h3> We present an efficient autoradiography technique for commissioning of a large inventory HDR-Gyn plastic applicators using a linear accelerator & HDR afterloader.

Assessing impact of chemical compatibility of additives used in asphalt binders: A case study using plastics

Economic and environmental factors mandate the use of engineered materials as well other waste or industrial by-products as an additive or extender in asphalt binders and mixtures. In most cases, the impact of these materials on the long-term performance of asphalt binders and concomitant mixtures is evaluated on an ad hoc basis. This study explores the use of chemical compatibility based on the Hansen Solubility Parameters (HSP) to better understand and predict the performance of modified asphalt binder blends. Specifically, this approach is applied to the case of plastic materials that are increasingly being evaluated as a value-added extender for binders. In order to investigate the role of chemical compatibility on the macroscopic performance of such modified blends, two different types of polyethylene (PE) plastics with varied compositional characteristics were studied, referred to as PE-1 and PE-2. Additionally, the impact of using elastomeric polymers as co-modifiers with plastics were also examined. From a solubility perspective, the results indicated that PE-1 and asphalt binders show reasonable compatibility, whereas PE-2 was incompatible. Further analyses were conducted to correlate these results using microscopic and rheological tools. PE-1 modified binders were seen to be well dispersed in the binder matrix and had acceptable performance, particularly with the combined use of co-modifiers. On the other hand, all PE-2 modified binders showed poor dispersion and consequently inferior rheological performance. The results also indicated that the addition of co-modifiers will only improve the compatibility of plastics in blends on a selective basis. Overall, the work conducted in this study demonstrates the impact of chemical compatibility on the macroscopic performance of different plastic modified blends. The approach used in this study can also be extended for use with other additives used in asphalt binders to better understand the chemo-mechanics of the different additive-binder blends and impact on performance.

Chemical, thermal and mechanical evaluation of poly(vinyl chloride) plastisol with different plasticizers

The most widely used plasticized polymer is poly(vinyl chloride) (PVC) due to its excellent plasticizer compatibility characteristics. Traditionally, PVC plasticizers belong to the phthalate family; however, they have harmful effects on human health and the environment. In this work, we evaluated the effect of six types of plasticizers (dioctyl phthalate, dioctyl adipate, Lestarflex (a polymeric polyester plasticizer), polycaprolactone, polyester polyol, and 1,2,3-propanetriol triacetate) on the properties of PVC plastisol used in manufacturing shoes and toys. The mechanical properties (hardness, tensile strength, tear strength, and elongation at break) were evaluated before and after accelerated aging tests (in an ultraviolet oven and at 50°C). A thermal study was also carried out using differential scanning calorimetry and thermogravimetric analysis, while possible structural changes during deformation were investigated using the small-angle X-ray scattering technique. In general, the results have shown that in the plasticization and stabilization of PVC, the plasticizer dioctyl phthalate can be replaced by dioctyl adipate or Lestarflex without relevant changes in the final properties of the material, even after accelerated aging.

Thermal, mechanical and morphological properties of plasticized polyurethane binders based on PEG and HTPB blends

Improving the properties of hydroxyl-terminated polybutadiene (HTPB) has always been one of the important topics for researchers in the propellant field. In this research work, a prepolymer from blend of HTPB and polyethylene glycol (PEG) is prepared with isophorone diisocyanate (IPDI). This prepolymer is mixed with glycerol for the synthesis of polyurethane (PU) elastomer. The compatibility of n-butyl nitroxyethylnitramine (n-BuNENA) as an energetic plasticizer with a non-energetic PU matrix was investigated. The properties of HTPB-PEG blend elastomer prepared with n-BuNENA plasticizer were compared with elastomers made by HTPB. The results of SEM analysis showed that incorporation of PEG improved the compatibility of plasticizer with PU matrices. DSC, FTIR spectroscopy and tensile analysis revealed that the phase separation degree and crystallinity in PEG-based PU were much higher than HTPB elastomer. It was determined by TGA results that the n-BuNENA plasticizer reduced the thermal stability of PU. Mechanical studies also indicated that the incorporation of PEG increases the modulus and tensile strength while the addition of plasticizer decreases the modulus and enhances the tensile strength and elongation.

Compatibility of Fuel System Elastomers and Plastics with a Fast-Pyrolysis Oil (Bio-oil) at Room Temperature

Compatibility of Fuel System Elastomers and Plastics with a Fast-Pyrolysis Oil (Bio-oil) at Room Temperature

A GAP Replacement, Part 2: Preparation of Poly(3-azidooxetane) via Azidation of Poly(3-tosyloxyoxetane) and Poly(3-mesyloxyoxetane).

Despite the variety of energetic polyoxetane binders, the oxirane-based glycidyl azide polymer (GAP) has largely succeeded in the market due to its advantageous properties. Nevertheless, it suffers from various drawbacks such as non-uniform chain termination, possible chlorine content (flame retardant), and toxic epichlorohydrin required for its synthesis. These problems can be bypassed using the structurally related poly(3-azidooxetane). Unfortunately, it is only accessible in moderate yield by polymerization of 3-azidooxetane. Herein, we describe its synthesis by polymer-analogous transformation using the new polymers poly(3-tosyloxyoxetane) and poly(3-mesyloxyoxetane) as precursors. This results in a significantly increased yield and improved safety as handling of the very sensitive 3-azidooxetane is avoided. The aforementioned prepolymers were prepared using boron trifluoride etherate as well as triisobutylaluminum as catalysts. The latter provides polymers of particularly high molecular weight, and the corresponding poly(3-azidooxetane) species was obtained and studied for the first time. In order to shed light on the applicability of poly(3-azidooxetane) as a GAP substitute, it was thoroughly studied with regard to thermal behavior, energetic performance (EXPLO5), plasticizer compatibility, and curing. Moreover, the aquatic toxicity of all involved monomers was analyzed and compared to epichlorohydrin. Here, poly(3-azidooxetane) turned out as a fully adequate, if not more environmentally benign, substitute.