Ethylene Propylene Diene Monomer Composites Research Articles

Use of expanded perlite as green filler for the preparation of EPDM‐perlite rubber composites with improved thermal stability and insulation properties

AbstractThe present study investigated the use of expanded perlite (e‐perlite) as a sustainable and cost‐effective filler for EPDM (ethylene propylene diene monomer) rubber composites. Various amounts of e‐perlite were incorporated into EPDM to assess its impact on the composite properties, such as curing characteristics, physical and mechanical properties, crosslink density, thermal conductivity, thermal stability, surface roughness, and contact angle. The composite with 15 phr of e‐perlite exhibited approximately 20% higher crosslink density and a 12% increase in hardness, while slight decreases were observed in elongation at break and tensile strength. The FE‐SEM (field emission‐scanning electron microscopy), atomic force microscopy, and contact angle analysis have been performed to investigate the surface morphology and the hydrophobicity. The thermal properties of the composites were assessed through thermogravimetric analysis, thermal aging tests, and thermal conductivity measurements. The results showed that e‐perlite significantly improved the aging resistance and the thermal stability. The composites with 15 phr e‐perlite exhibited a 21% reduction in thermal conductivity and enhanced thermal isolation properties compared to the EPDM composite without e‐perlite. This work demonstrated the potential utilization of e‐perlite in EPDM as a green sustainable filler to enhance the thermal insulation and the stability properties of the composites, which may have practical applications in automotive, aerospace, construction, and electronic industries.Highlights E‐perlite enhances the thermal insulation property of EPDM rubber composites. Higher e‐perlite content increases composite hardness and crosslink density. The thermal conductivity of EPDM is reduced by increasing e‐perlite content. EPDM/e‐perlite exhibits improved thermal stability and aging resistance. Potential uses in automotive, aerospace, construction, and defense industries.

Thermal Oxidative Aging and Service Life Prediction of Commercial Ethylene-Propylene-Diene Monomer Spacer Damping Composites for High-Voltage Transmission Lines.

The aging behavior and life prediction of rubber composites are crucial for ensuring high-voltage transmission line safety. In this study, commercially available ethylene-propylene-diene monomer (EPDM) spacer composites were chosen and investigated to elucidate the structure and performance changes under various aging conditions. The results showed an increased C=O peak intensity with increasing aging time, suggesting intensified oxidation of ethylene and propylene units. Furthermore, the surface morphology of commercial EPDM composites displayed increased roughness and aggregation after aging. Furthermore, hardness, modulus at 100% elongation, and tensile strength of commercial EPDM composites exhibited a general increase, while elongation at break decreased. Additionally, the damping performance decreased significantly after aging, with a 20.6% reduction in loss factor (20 °C) after aging at 100 °C for 672 h. With increasing aging time and temperature, the compression set gradually rose due to the irreversible movement of the rubber chains under stress. A life prediction model was developed based on a compression set to estimate the lifetime of rubber composites for spacer bars. The results showed that the product's life was 8.4 years at 20 °C. Therefore, the establishment of a life prediction model for rubber composites can provide valuable technical support for spacer product services.

Multiscale simulation study on radiation aging of EPDM and preparation of radiation-resistant materials

With the wide application of ethylene propylene diene monomer (EPDM) in the field of nuclear engineering, exploring the radiation aging mechanism of EPDM is of great significance to improve the radiation resistance of EPDM composites. In this paper, the radiation aging mechanism of EPDM was investigated by a combination of experiments and multiscale simulations, and EPDM composites with excellent radiation resistance were prepared. The radiation aging mechanism of EPDM involves the crosslinking and degradation of molecular chains. The aging of EPDM starts from the breakage of α-H in the 5-ethylidene-2-norbornene monomer. In addition, the screening strategy of radiation-resistant additives was proposed. Antioxidants N, N′-diphenyl-p-phenylene-diamine (H), N, N′-ditolyl-p-phenylenediamine (DTPD), and N, N′-di-2-naphthyl-p-phenylenediamine (DNP) were taken as the main research objects, and quantitative analysis was carried out from the aspects of chemical protection and physical protection. The screening results showed that DNP has excellent radiation resistance and migration resistance. The prepared EPDM-DNP composites showed outstanding radiation resistance with 94% tensile strength retention after 300 kGy irradiation. This work contributes to understand the mechanisms of radiation-induced material damage and guides the design of radiation-resistant materials.

Design and Study of Novel Composites Based on EPDM Rubber Containing Bismuth (III) Oxide and Graphene Nanoplatelets for Gamma Radiation Shielding.

The mechanical, thermal and gamma radiation attenuation properties of ethylene-propylene-diene monomer (EPDM)-based composites containing graphene nanoplatelets (GNs) and bismuth (III) oxide nanoparticles (B) were investigated. The use of polyethylene glycol (PEG) as a compatibilizer to improve the dispersion of the fillers was also investigated. The results showed that the combined use of these fillers resulted in a drastic increase in mechanical properties, reaching 123% and 83% of tensile strength and elongation at break, respectively, compared to those of EPDM. In contrast, the addition of PEG to composites containing EPDM GNs and B resulted in composites with lower values of mechanical properties compared to the EPDM/B/GN-based composite. However, the presence of PEG leads to obtaining a composite (EPDM/B/GNP) with a mass attenuation coefficient to gamma radiation (137Cs, 662 keV) superior to that composite without PEG. In addition, the composite EPDM, B and PEG exhibited an elongation at break 153% superior to unfilled EPDM. Moreover, the binary filler system consisting of 100 phr of bismuth (III) oxide and 10 phr of GN leads to reaching 61% of the linear damping coefficient of the EPDM composite compared to that value of the unfilled EPDM. The study of the morphology and the state of filler dispersion in the polymer matrix, obtained using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively, provides a useful background for understanding the factors affecting the gamma radiation attenuation properties. Finally, the results also indicated that by adjusting the formulation, it is possible to tune the mechanical and thermal properties of EPDM composites reinforced with bismuth oxide and graphene nanoplatelets.

Nano‐BN/Nano‐TiO2 and micro Mg(OH)2 loaded hybrid ethylene propylene diene monomer elastomer composites for outdoor high‐voltage insulation application

AbstractThis work deals with the synthesis, characterization of hybrid ethylene propylene diene monomer (EPDM) composites loaded with nano‐boron nitride (nano‐BN)/nano‐titanium dioxide (nano‐TiO2) and micro Mg(OH)2 particles for its suitability towards high‐voltage insulation application. The elastomer samples were prepared by carefully dispersing the micro and nano fillers during the mastication process of EPDM polymer using a two roll mill, followed by vulcanization. The samples were characterized for mechanical, morphological, thermal, and electrical insulation properties. The highest tensile strength among the composite samples was noted for 1 phr nanoparticles loaded samples. Fourier Transform Infrared (FTIR) results show no change in the chemical moiety upon addition of nano‐BN/nano‐TiO2 in EPDM composites. Enhancement in hydrophobicity is observed for 3 phr nano‐TiO2 loaded composites, which shows a maximum static contact angle of 110°. Meanwhile remarkable enhancement in the thermal conductivity and volume resistance of the composites are contributed to the addition of nano‐BN, thereby achieving maximum dielectric breakdown voltage (i.e., ~21 kV/mm for EMB3). Scanning electron microscope images and atomic force microscopy (AFM) topography highlight that low concentration (i.e., 1 phr) based composites have homogeneous dispersion in matrix and excessive nano filler addition deteriorates properties by forming filler aggregates and increasing surface roughness.

Sulfur Free Crosslinking of EPDM Composites via Silane Grafting and Silica Incorporation.

This study aims at evaluating and developing an environmental-friendly and sulfur-free cured ethylene propylene diene monomer (EPDM) composites. Silane grafted EPDM (SiEPDM) composites incorporated with silica is prepared via a solvent-free, one-step reactive mixing process. The silane grafting and silica filler bonding are characterized using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The mechanical properties of the developed composites are examined. The fracture morphology is observed using an environmental scanning electron microscopy. The rheology and thermomechanical properties are evaluated by using a rotational rheometer and dynamic mechanical analyzer. Notably, a robust bonding between silica and the grafted silane is established, yielding a crosslinking network within the composite structure. This phenomenon is substantiated by the observed gel efficiency and rheology behavior. Consequently, a pronounced augmentation of up to 75% in tensile strength and 29% in tear strength are observed in the optimized SiEPDM-silica composites, distinguishing them from their EPDM-silica counterparts. The introduction of paraffin oil contributes to enhanced processability; however, it is concomitant with a reduction in gel efficiency and associated mechanical properties. Furthermore, subsequent UV weathering test unveils that the SiEPDM-silica composites exhibit the highest levels of residual tensile strength and modulus, indicative of their exceptional UV stability.

Development of EPDM composites reinforced by CNTs@SiO2 for thermal protection systems of aerospace propulsion: Significant improvement in oxidation and ablation resistance properties

Carbon Nanotubes (CNTs) reinforced Polymer-Matrix Composites (PMCs) is widely used as insulation materials in thermal protection system of aerospace propulsion. However, CNTs are prone to oxidation and have high thermal conductivities, which makes it difficult to improve the ablation resistance of insulation materials that contain CNTs. SiO2 was encapsulated onto the surface of CNTs (CNTs@SiO2), which were then added to Ethylene Propylene Diene Monomer (EPDM) rubber to prepare the insulation materials. Thermogravimetric analysis and ablation test were used to evaluate the resistance of the insulation materials to thermal oxidation and ablation. Additionally, scanning electron microscopy was performed to analyze their microstructures. Results revealed that the addition of CNTs@SiO2 could visibly reduce the effects of hot corrosion and ablation on insulation materials. The C-CNTs@SiO2-1 formulation had the best ablative resistance. Further, compared with the unencapsulated formulation (C-CNTs-10), the C-CNTs@SiO2-1 formulation reduced the line ablation rate by 51% to 0.0130 mm/s after oxygen-acetylene experiments. Lastly, the ablation mechanism was investigated based on the effects of the CNTs@SiO2 additive on their properties. Thus, the improvement in ablation performance may be attributed to CNTs@SiO2-induced decreases in thermal conductivity, improvement in the hot corrosion resistance in the char layer, and changes in the microstructure.

Carbon nanotubes and hexagonal boron nitride nanosheets co‐filled ethylene propylene diene monomer composites: Improved electrical property for cable accessory applications

AbstractRubber‐based composites based on ethylene propylene diene monomer (EPDM) with excellent non‐linear electrical conductivity are preferred to serve as reinforced insulation in cable accessories, which can self‐adaptively regulate electric field distribution and avoid electric field concentration due to the non‐linear conductivity. The conductive carbon nanotubes (CNT) are filled into EPDM to improve the non‐linear conductivity, while the insulating hexagonal boron nitride nanosheets (h‐BN) are used to reconcile the electric breakdown strength. The results show that with the increase of CNT loading content, the non‐linear conductivity of CNT/h‐BN/EPDM composites becomes more prominent, accompanying the decrease of threshold field strength and increase of non‐linear coefficient. However, the electric breakdown strength of CNT/h‐BN/EPDM composites seriously deteriorates due to the increase of CNT content and temperature. By incorporating 10 wt.% h‐BN into the composites, the reduction percentage of breakdown strength can be significantly lowered, which is 19.95% of neat EPDM and 13.74% of CNT/h‐BN/EPDM composites at 70°C, respectively. The COMSOL Multiphysics simulation results demonstrate that using the CNT/h‐BN/EPDM composite as the reinforced insulation can eliminate the electric field concentration of the cable accessory as well as enable the cable accessory with good lightning shock resistance.

A comprehensive study on the thermal and electrical conductivity of EPDM composites with hybrid carbon fillers

In this study, ethylene-propylene-diene monomer (EPDM) composites reinforced with graphene nanoplatelets (GnPs) and carbon black (CB) fillers and their hybrid combinations of various contents were prepared and examined. The size effect (lateral size and specific surface area) of GnPs and filler hybridization effects between GnPs and CB on the electrical and thermal conductivity of the EPDM composites were examined. The lateral size of GnPs is a more decisive factor in the thermal conductivity of composites than their specific specific surface area, and GnPs with a higher lateral size give better thermal conductivity. The addition of GnPs with a high lateral size and low specific specific surface area results in an almost one-fold increase in thermal conductivity. After a certain filler concentration, a synergistic effect of GnPs and CB on the thermal conductivity can be observed. Up to 20 phr GnPs, the specific surface area or lateral size of GnPs has a slight effect on the electrical conductivity of EPDM/GnPs composites. Higher electrical conductivity was achieved when hybrid fillers, 50 phr CB and 7 phr GnPs with higher lateral size were used for composite preparation. The morphology of the composite samples and the dispersion of all used fillers and hybrids were examined using transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

Nanoarchitectonics of ethylene propylene diene monomer (EPDM) composites reinforced with Cu–Al–Zn-alloy for ultrasonic array transducers’ fabrication

In response to the continuous demand for industry progress and the need for low-cost alternative materials that have superior properties than the present ones, a new coupling agent was used to treat composites, which were used as new backing materials in ultrasonic array transducers. In array transducers, back-echo reverberation to the piezoelectric elements occurs, so backing materials are critical in reducing these echoes. The Cu–Al–Zn-alloy was treated with a coupling agent before being incorporated into ethylene propylene diene monomer (EPDM) composites. Cu–Al–Zn-alloy/EPDM composites were assessed using rheometric, mechanical, and morphological properties. The division of cu-alloy at the EPDM matrix was visualized using a scanning electron microscope (SEM). TGA and DSC techniques were used to study the thermal characterization of the EPDM composites. As a result, the treated Cu-alloy improved the thermal, mechanical, and morphological characteristics of EPDM composites. Ultrasonic measurements ensured the composites' effectiveness as backing materials in ultrasonic array transducers. Furthermore, the composites’ properties were similar to those of the most commonly used epoxy/tungsten backing material. Finally, linear ultrasonic-phased array transducers were fabricated using Cu–Al–Zn-alloy/EPDM composites. They had a low signal-to-noise ratio, and this ensured the effectiveness of Cu–Al–Zn-alloy/EPDM composites as backing materials.

The effect of MWCNTs on the properties of peroxide vulcanized ethylene propylene diene monomer (EPDM) composites

Multiwalled carbon nanotubes (MWCNTs) were incorporated in EPDM matrix in an internal mixer. Characterization of the prepared MWCNTs/EPDM composites using RAMAN spectroscopy reveals a minor deterioration of the CNTs’ structure, in terms of intensities ratio of D and G bands (ID/IG ratio), probably due to the intensive mixing conditions of internal mixer. The thermal stability of MWCNTs/EPDM composites was improved, as it was observed by thermogravimetric analysis (TGA) results, whereas the glass transition temperature (Tg) remained almost unaffected. In addition, MWCNTs/EPDM composites showed significant improvement in their modulus of elasticity and a decrease in swelling after immersion in benzene, in comparison with the pristine elastomer. The study of dielectric properties for MWCNT’s/EPDM nanocomposites determined the percolation threshold between 2 and 3 phr MWCNTs content. Enhancement in electromagnetic interference (EMI) shielding effectiveness of MWCNTs/EPDM composites was also recorded by the increase of filler content in the elastomeric matrix, with the reflectance being the main shielding mechanism. A slight increase in thermal diffusivity and conductivity was observed at EPDM composites with low MWCNTs content (1–5 phr) which became more significant at higher loads (8 & 10 phr).

Effect of CNT content and size on the high-temperature particle-erosion resistance of ablative materials for thermal protection systems

Advanced spacecraft development requires high-performance thermal protection systems composed of materials with high particle-erosion resistance. In this study, a particle-erosion test motor was designed to produce a high-temperature particle jet. Subsequently, the effects of carbon nanotube (CNT) content and size on the particle-erosion resistance of ethylene propylene diene monomer (EPDM) composites were analyzed. Composites with an optimum CNT content exhibited the lowest ablation rates; extremely high or low CNT contents increased the ablation rate. Furthermore, the charring rate of the composites with long CNTs were 78.0% and 43.6% lower than those with the baseline-formula composition and those containing conventional CNTs, respectively. Here, the influence of CNT content and size on the particle-erosion resistance of EPDM composites was analyzed from the perspective of the thermal stability of the composites, as well as the char-layer characteristics and vapor deposition.

Investigate the effect of ground tyre rubber as a reinforcement filler in natural rubber hybrid composites

ABSTRACT This paper investigates the effect of various proportions of Ground Tyre Rubber (GTR) blends with Natural Rubber (NR)/Ethylene Propylene Diene Monomer (EPDM) or NR/Chloroprene Rubber (CR) composites. The NR (95 phr) composites were developed with 5 phr of EPDM or 5 phr of CR along with different ratios of GTR (0, 10, 20, 30, and 40 phr) by a two-roll mill and hydraulic press. The interfacial adhesion of NR/EPDM and NR/CR composites was improved with the addition of nylon 6 at 5 phr. Hence, the silica (20 phr) and carbon black (10 phr) were used as conventional fillers in these composites. The mechanical and curing properties of the developed NR-based hybrid composites were evaluated and compared with control samples. It was noted that the maximum tensile strength, tear strength, hardness, and Young’s modulus were increased by 8%, 9.39%, 6.35%, and 18.31% in NR/EPDM/GTR (95/5/10), while for NR/CR/GTR (95/5/10), 17.1%, 10.71%, 6%, and 31.72% over the control sample. The elongation at break was reduced by 29.11% in NR/EPDM/GTR (95/5/10), but for NR/CR/GTR (95/5/10) was 21.65% over the control sample. The cure properties like scorch time (tS2) and cure time (tC90) were decreased, while minimum torque (ML) and maximum torque (MH) were enhanced with the incorporation of GTR 10 phr in both the composites when compared with the control sample. The addition of GTR increased the sulfur in the cured composites, which was confirmed in EDS analysis. Based on the microstructure and thermogravimetric analysis, GTR particles were uniformly distributed, and the thermal stability was increased by 19.6% and 21.5% in NR/EPDM/GTR (95/5/10) and NR/CR/GTR (95/5/10) composites, respectively, over the control sample. The absorption peaks of NR, EPDM, CR, and GTR elements in the developed composite were identified using Fourier Transform Infrared spectroscopy (FTIR). In the NR/EPDM composite, the glass transition temperature (Tg) was increased from −60.7°C to −58.17°C, but for the NR/CR composite, it was −61.43°C to −58.96°C. Finally, the inclusion of 10 phr of GTR was recommended to be suitable for NR with EPDM or CR composites.

Hydrogen gas permeation in peroxide‐crosslinked ethylene propylene diene monomer polymer composites with carbon black and silica fillers

AbstractThis study investigated the effect of two types of fillers, carbon black (CB) and silica, on the H2 permeation of peroxide‐crosslinked ethylene propylene diene monomer (EPDM) polymers at different pressures (1.2–9.0 MPa). The H2 uptake was linearly correlated with the exposure pressure in all specimens. The H2 solubility in the filled EPDM composites also increased linearly with an increase in the filler content. The H2 solubility was determined by the absorption of polymer networks and adsorption at the filler surface in the CB‐filled EPDM. Meanwhile, the H2 solubility in neat and silica‐filled EPDM was dominated by the polymer network absorption. In the filled EPDM, H2 diffusivity decreased because the filler increased the tortuosity of the polymer. The effects of filler on H2 permeation were largest in the high‐abrasion and semi‐reinforcing furnaces, while the effects were lowest in the silica filler. This trend was associated with the surface area and interface of the fillers. The correlations of the average diffusivity (or permeability) with the filler content and crosslink density of the composites were observed and discussed. From the resulting relationships, we can predict the H2 permeation properties of the compounded EPDM candidates, when used as seal materials, under high‐pressure environment in H2‐refueling stations.

Prediction for snow melting process of conductive ethylene propylene diene monomer composites based on machine learning approaches

Accurate prediction for snow melting process of conductive ethylene propylene diene monomer (EPDM) composites is an important prerequisite for engineering applications. In this paper, the snow melting process of conductive EPDM composites on roads was determined and three machine learning approaches were compared. The snow melting process was tested several times in outdoor environment. Multiple linear regression (MLR), back propagation neural network (BPNN) and support vector regression (SVR) models were analyzed and developed. The three machine learning models were optimized by a cross validation approach. Finally, a suitable model was selected to predict the snow melting process. The results show that conductive EPDM composites can melt snow on roads at low voltages. In addition, the snow melting process is controlled by adjusting the input voltage. The rate of snow melting is affected by snow thickness, input voltage, and ambient temperature. The results of the MLR model are poor with a coefficient of determination (R2) less than 0.85. Moreover, the BPNN model with three neurons has better prediction results. The R2 of the BPNN model ranges from 0.93 to 0.95. The R2 of the SVR model with radial basis kernel function is greater than 0.95. Among the three machine learning models, the SVR model can accurately predict the snow melting process. This study not only provides a new idea for active snow melting but also provides a theoretical basis for the engineering application of conductive EPDM composites.

Thermal stability of gamma irradiated ethylene propylene diene monomer composites for shielding applications

AbstractThe effect of gamma‐irradiation on the ethylene propylene diene monomer (EPDM) based composites, loaded with tungsten and barium sulfate were investigated for radiation resistance properties. The tungsten and barium sulfate fillers were added in different proportion (wt%) to EPDM matrix and prepared using compression molding technique. The developed EPDM composites were exposed to 60Co gamma radiation doses from 0 to 400 kGy. The swelling index of the composites were studied for the irradiated samples and found to decrease with higher gamma doses. Tensile characterization was also carried out and elongation at break, tensile strength and modulus at 100% elongation have been determined for gamma irradiated EPDM based composites. Tensile properties were modified in the irradiated samples and elongation at break is decreased whereas the modulus increases as a function of gamma dose due to increases in crosslinking after irradiation. Thermogravimetric analysis was performed and observed improvement in thermal stability of gamma irradiated EPDM composites.

Synergistic effect of polyphosphazene nanotubes and graphene on enhancing ablative resistance of ethylene propylene diene monomer insulation composites

AbstractMany advanced fillers were used in ethylene propylene diene monomer (EPDM) insulation composites to enhance the ablative resistance by strengthening char layer. However, the structures of fillers and char layer were usually neglected. In this work, a new type of cross‐linked network‐like polyphosphazene nanotubes (PNTs) was added in EPDM composites in combination with graphene. The results showed that the ablation performance of EPDM composites was improved by 21.6% with the synergistic effect of PNTs and graphene. Moreover, the ablation mechanism was studied by analyzing ablated char layer using X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and Raman spectroscopy. PNTs served as skeleton to build the cross‐linked network char layer and graphene played a role in enhancing the properties of char layer. The findings of this work emphasize the synergistic effect of structures and properties of fillers when performing ablative modification, which provides a new idea to enhance the ablation properties of EPDM composites.

Anti‐migration performance of EPDM composite improved by octadecylamine‐functionalized graphene oxide

AbstractIn this paper, the ethylene propylene diene monomer (EPDM) was used as a composite matrix and octadecylamine‐functionalized graphene oxide (GA) was applied as insulation nanofiller to prevent plasticizer migration. To study the anti‐migration behavior of EPDM under plasticizer environment and different temperatures, we investigated the diffusion of dioctyl phthalate (DOP) in EPDM and its composites. The migration kinetics of DOP into EPDM composites with respect to filler and temperature were observed by the immersion absorption method. The process is dynamic and conforms to Fick's law. The composite show a 90% increase in tensile strength and 151% improvement in elongation at break by the addition of 5 phr filler of GA. Meanwhile, the EPDM/GA composite show an obviously improved anti‐migration performance, compared to pure EPDM at different temperatures, the composite show a 22.68%, 17.35%, 14.95%, 7.63% increase. Well layer‐structure of graphene offers a chance to improve the anti‐migration performance of insulation.

Effect of different nanostructured SiC on thermal, ablation and char layer mechanical properties of ethylene propylene diene monomer composites

AbstractSiC nanowire (SiC‐NW) and SiC nanopowder (SiC‐NP) were used to reinforce ethylene propylene diene monomer (EPDM) composites to improve their ablation and erosion resistance. The mechanical and thermal properties of the composites were investigated. The ablation resistance and thermal insulation performance of the composites were evaluated based on the oxyacetylene ablation and ablation motor experiments. In addition, the particle erosion resistance of the char layer was characterized. The test and experimental results show that, compared with the basic formulation, the ablation resistance of the formulations containing SiC‐NW and SiC‐NP increased by 85.54% and 71.08%, respectively. The particle erosion resistance of the char layer increased by 80.61% and 63.39%, respectively. Meanwhile, the SiC nanofiller reduced the thermal insulation performance of the EPDM composites. Compared with the basic formulation, the maximum back temperature of the SiC‐NW and SiC‐NP formulations increased by 39.23% and 13.08%, respectively. It inferred that during the ablation process, the SiC nanofiller can not only promote the deposition reaction of pyrolysis gas, but also react with oxidizing components and the char layer at different temperatures, thus improving the ablation resistance of the EPDM composites and the strength of the char layer. However, the high thermal conductivity of SiC nanofiller reduces the thermal insulation performance of the composites.

Enhancing Thermal Insulation of EPDM Ablators via Constructing Alternating Planar Architectures.

Ethylene–propylene–diene monomer (EPDM) composites were usually enhanced with ablative additives to protect solid rocket motor (SRMs) casings. However, the poor thermal insulation caused by the high thermal conductive ablative fillers can lead to rocket motor failure. Herein, the novel EPDM composites containing alternating layers of ablative EPDM (AM) and heat-insulated EPDM (HM) were prepared through layer-multiplying extrusion. Compared with conventional EPDM ablative material, the multilayer composites showed enhanced thermal insulation and mechanical properties that could be further improved by tuning the number of layers. The ablation and thermal insulation properties possessing in AM and HM layers could be combined by forced assembly during co-extrusion, and the alternating multilayer composite was capable of showing the effect of each component. In particular, compared with AM, the maximum back-face temperature with 40 alternating layers of AM/HM decreased from 96.2 °C to 75.6 °C during oxyacetylene test, while the good ablation properties were preserved in the AM component. This significant improvement was attributed to the planar orientation and densification of ablative additives, and the interruption of conductive pathways in the through-plane direction of AM/HM alternating laminate. The anisotropic EPDM composites featuring mechanical robustness, good ablative resistance and thermal insulation suggest considerable potential application in the aerospace industry.