Olefin Block Copolymer Research Articles

Enhancement and Compatibilization of Waste-Sourced Biocomposites Through Elastomer Blending and Matrix Grafting Modification

A novel elastomer-modified multicomponent, multiphase waste-sourced biocomposites, was prepared for converting waste biomass and plastic into value-added products. The effects of blending elastomer–olefin block copolymer (OBC) and maleic anhydride (MAH), and divinylbenzene (DVB) co-grafting of recycled polypropylene (rPP) matrix on the adhesion interface, structure, and properties of high wood flour-filled (60 wt.%) composites were thoroughly investigated. The results indicated that DVB introduced branched structures into the polymer matrix molecular chain and increased the MAH grafting rate. Co-grafting rPP/OBC blends enhanced the interfacial adhesion among rPP, OBC, and wood flour. Additionally, MAH-grafted OBC was prone to encapsulating rigid wood flour, thereby forming an embedded structure. Notably, the tensile modulus and impact strength of the final three-component composites increased by 60% and 125%, respectively, compared with the unmodified composites. Additionally, dynamic mechanical analysis revealed that DVB-induced branching promoted the formation of microvoids in the OBC shell layer surrounding the wood, which in turn induced significant plastic deformation in the polymer matrix. This work offers a facile and efficient method for preparing high-toughness, high-stiffness, and low-cost waste PP-based composites for automotive interiors, and indoor and outdoor decoration.

Synergistic performance enhancement of lead-acid battery packs at low- and high-temperature conditions using flexible phase change material sheets

Thermal management of lead-acid batteries includes heat dissipation at high-temperature conditions (similar to other batteries) and thermal insulation at low-temperature conditions due to significant performance deterioration. To address this trader-off, this work proposes a thermal management solution based on flexible phase change materials (PCMs) with moderate thermal conductivity and other favourable properties including high specific heat capacity and high latent heat. A novel type of flexible PCM sheets is prepared with paraffin, olefin block copolymers (OBC) and expanded graphite using the co-melting method. The flexible PCM sheets are attached to a common type of lead-acid battery packs (12 Ah, dimensions of 151 × 98 × 97 mm) and thermal management performance is experimentally investigated at –10 °C and 40 °C as low- and high-temperature conditions, respectively, along with 25 °C as a baseline case for comparison purposes. Thermal properties of the battery packs such as temperature regulation and electric properties including charge/discharge capacities and rates are studied synchronously based on a standard high-performance battery detection facility. The results indicate that at –10 °C condition, the PCM sheet enhances thermal insulation of the battery pack and significantly promotes the service temperature during the charging processes. Compared with a benchmark pack attached with an encapsulated sheet, the charge and discharge capacities of the PCM-attached pack are improved by 3.7% and 5.9%, respectively. At 40 °C condition, phase transition of the PCM sheet restrains the temperature rise of the battery pack, with a maximum temperature decrease of 4.2 °C during the charging processes relative to the benchmark pack, and the temperature of the PCM-attached pack is maintained below 45 °C across 60% of the overall charge period. The overcharge and overdischarge have also been alleviated by 3.2% and 2.8%, respectively, and thus the running stability and service lifespan can be improved. The proposed PCM sheets with preferable thermal properties demonstrate potential to promote performance of lead-acid battery packs and such components are also expected to improve heat dissipation and thermal insulation in similar applications including building energy saving, thermal management of electronic chips and thermal regulation of electronic devices.

Upcycling of polyethylene/polypropylene mixtures promoted by well-controlled multiblock olefin copolymers

Polyethylene (PE) and isotactic polypropylene (iPP) are two of the most widely used polymer materials, whose huge consumptions urge people to tackle their recycling problem. The incompatibility of PEs and PPs has resulted in their waste streams being recycled into low-value products with poor mechanical properties. Herein, a series of iPP-based olefin block copolymers (OBC) with up to five alternating hard/soft blocks were prepared via coordinative chain transfer polymerization. The facile synthetic strategy of multiblock OBCs not only overcame the inefficiency and diseconomy of living coordination polymerization, but also avoided the critical requirements of complex dual-catalyst systems for chain shuttling polymerization, making it suitable for low-cost and large-scale production of OBCs. These well-designed OBCs provided excellent elastomeric properties combining high strength, high elongation, and high elastic recovery. More importantly, they also demonstrated a strong ability in the upcycling of PE/PP mixtures, transforming brittle blends into tough materials. The PE/PP blends compatibilized with OBCs exhibited greatly improved interfacial adhesion and mechanical properties, with up to 25 times higher elongation at break compared to uncompatibilized blends. It was further demonstrated by the extruding-blow-molded bottles prepared using post-consumer PE/PP products, where recycled bottles containing OBCs exhibited much better mechanical properties than those without OBC. The synthetic strategy of OBCs and the upcycling route of PE/PP blends in this work are not only of great academic value, but also of substantial economic and environmental significance, providing insights into the sustainable development of plastics.

The comparative study of PP-b-PE block copolymer and ethylene-octene block copolymer on crystallization, structure and mechanical property of high-density polyethylene/polypropylene blends

Olefin block copolymers can improve the compatibility between polyethylene (PE) and polypropylene (PP). The work studied the impact of ethylene-propylene multiblock copolymer (PP-b-PE) and ethylene-octene block copolymer (OBC) on the crystallization behavior, mechanical properties, phase structure, and interfacial interactions of HDPE/PP blends. The result showed that PP-b-PE promotes the crystallization temperature and rate of both HDPE and PP, while OBC primarily affects the crystallization behavior of HDPE. The addition of PP-b-PE, as evidenced by small angle X-ray scattering (SAXS), further weakened the interface region between HDPE and PP compared to OBC, indicating enhanced compatibility between HDPE and PP, further confirmed by the stronger adhesion of PP-b-PE to PP and HDPE compared to OBC in peel test. Surface morphology and surface energy analysis demonstrated that PP-b-PE can form a core-shell structure with PP by encapsulating PP, similar to OBC-PP core-shell structure, reducing the interfacial tension between HDPE and PP that effectively transfers stress to the PP phase. The improved compatibility of HDPE/PP resulted in higher elongation at break and equivalent impact strength to HDPE.

Using Probability Models to Design the Microstructure of Linear Olefin Block Copolymers

Using Probability Models to Design the Microstructure of Linear Olefin Block Copolymers

Inspection of microwave self‐healing efficiency in carbon nanotube reinforced polymer composites for aerospace applications

AbstractThe aerospace industry is evolving very rapidly every day, and due to the low operational and maintenance costs, unmanned aerial vehicles (UAVs) are utilized for many duties, including imaging, patrol, surveillance, and delivery. Flying platforms prioritize effective load‐carrying capacity and light weight. To achieve this, lightweight materials with sufficient strength are utilized, and design optimizations are implemented. This study investigates material development for a UAV propeller, taking into account the possible consequences of a bird strike or hard landing such as micro damage occurrence. In this study, a twin‐screw extruder was used to produce hybrid composites by blending a thermoplastic, polyamide‐6 (PA6) with olefin block copolymers (OBC) and carbon nanotubes (CNT). After manufacturing test specimens by injection molding, tensile and Charpy impact tests were performed. OBC increased the elongation capacity and impact resistance of the PA6 through maleic anhydride (MAH) grafting while reducing the tensile strength. CNT incorporation compensated for this drop, but it rendered the composites more brittle. More importantly, due to the CNT's microwave (MW) absorption capacity, the hybrid composites have gained self‐healing properties. Extended MW exposure time and high MW powers may cause localized burning of the material, resulting in a decrease in its self‐healing efficiency. Following the failure of the examined composites, SEM microscopy revealed various toughening mechanisms in the composites. The use of a modified Halpin‐Tsai model to estimate the elastic characteristics of CNT‐reinforced composites revealed promising results, with minimal discrepancies when compared to experimental data.Highlights CNTs were found efficient for the self‐healing behavior which is critical for improving the lifetime and planning maintenance for UAV propellers. CNT content, MW power & exposure time all impact the self‐healing efficiency. Extended MW exposure time and high MW powers can cause localized burning of the material, resulting in a decrease in its self‐healing efficiency. CNTs created bridge effects, ultimately leading to an enhancement in the strength of the composites. The use of a modified Halpin‐Tsai model yielded good accuracy with experimental data.

Reactive melt‐grafting of maleic anhydride onto olefin block copolymer toward high‐performance polar polyolefin thermoplastic elastomer

AbstractThe block structure of olefin block copolymer (OBC) elastomer gives it good elasticity and heat resistance relative to other polyolefin elastomers. However, the non‐polar nature of OBC chains limits its comprehensive properties like dyeing and toughening for polar engineering plastics. In this work, maleic anhydride (MA) and dicumyl peroxide (DCP) were selected as a typical polar monomer and a radical initiator to modify the polarity of OBC elastomer. During the melt‐grafting process, the DCP content was tuned to optimize the grafting efficiency while the MA‐to‐OBC ratio was fixed at 5 wt%. It was found that all the melt‐grafting reactions show high efficiency and can be finished in 3 min at 170 °C. With the increase of DCP content, the estimated grafting degree of OBC‐g‐MA elastomer increases from 0.40% to 1.16% along with increased gel content from 4.27% to 22.44%. A suitable grafting process was obtained with a DCP content of 3.0 wt% by balancing grafting efficiency and final mechanical properties. The optimized OBC‐g‐MA elastomer with a grafting degree of 0.92% has a mechanical strength of 17.15 MPa, a Young's modulus of 26.35 MPa, elongation of 1564% and strain recovery of 59.73%. Additionally, the contact angle test shows that polar grafting can increase surface hydrophilicity while excessive crosslinking promotes hydrophobicity. Therefore, our work has demonstrated the feasibility of the reactive melt‐grafting method to prepare OBC‐g‐MA elastomer and can also provide a processing reference for other chemical functionalization of polyolefin thermoplastic elastomers. © 2024 Society of Industrial Chemistry.

Preparation and characterization of isotactic polypropylene-based block copolymers with cyclic units

Olefin block copolymer is one class of promising high-end material that has the potential to combine the performance advantages of individual blocks. In this work, a series of isotactic polypropylene (iPP)-based diblock copolymers was designed and synthesized by coordinative chain transfer polymerization using a dimethyl(pyridylamido)hafnium/[Ph3C][B(C6F5)4]/AliBu3 catalytic system. The prepared diblock copolymers were composed of the regular iPP segments and the propylene/1,5-hexadiene (1,5-HD) random segments. The incorporated 1,5-HD existed exclusively as methylene-1,3-cyclopentane units in the polymer chains, because of the complete cyclization selectivity of the employed dimethyl(pyridylamido)hafnium catalyst. These block copolymers possessed high melting temperatures over 158 °C. Moreover, the block copolymers exhibited remarkably improved mechanical properties with respect to iPP, which could be systematically tuned by adjusting the content of 1,5-HD. In the 1,5-HD content range of 3.4–11.0 mol%, the block copolymers exhibited both high yield stress and high elongations at break. The copolymerization approach of block copolymers provided an effective method to achieve the strength-ductility balance of iPP-based copolymers.

Novel composite phase change materials supported by oriented carbon fibers for solar thermal energy conversion and storage

Phase change materials (PCMs) have aroused significant interest as promising materials for solar thermal energy conversion and storage. However, the long-standing shortcomings of liquid leakage, low thermal conductivity, and weak solar absorptance limit their practical applications. Herein, novel composite phase change materials (CPCMs) with anisotropic heat conduction are manufactured by mixing continuous carbon fibers (CFs) and palmitic acid (PA)/olefin block copolymer (OBC) mixtures using pressure induction and vacuum treatment. Because the oriented CFs in the vertical direction can offer heat transfer channels inside the composites, the vertical and horizontal thermal conductivities of the CPCMs are 5.84 W·K−1·m−1 and 1.34 W·K−1·m−1, respectively, resulting in a relatively high anisotropic degree of 4.36. Furthermore, to improve the absorption of solar radiation for the composite, carbon black is applied to the upper surface of the CPCMs, achieving a high total solar absorptance of 0.966. Due to the combination of the high solar absorptance of the carbon black and the high vertical thermal conductivity within the composites, the CPCMs exhibit outstanding solar-to-thermal efficiencies of 87.54% ∼ 95.08% at 1– 3 kW·m−2. In addition, stability testing also confirms that the CPCMs have excellent leakage-proof properties, thermal stability, and cyclic stability for long-term utilization. This work can provide an efficient route to synthesize high-performance CPCMs for solar thermal applications.

Covalent adaptable networks and thermosets of multi-block ethylene/1-octene copolymers made by free-radical processing: Effects of melt flow index and crystallinity on thermomechanical properties and reprocessability

Chain shuttling polymerization has facilitated the rapid development of olefin block copolymers (OBCs) such as ethylene/1-octene multi-block copolymers. The properties of OBCs stem from various parameters such as average block length, number of blocks per chain, etc., which lead to complexity associated with establishing structure–property relationships between precursor OBCs and properties of cross-linked OBCs. Additionally, permanent cross-linking of OBCs sacrifices their recyclability, and cross-linked OBCs capable of being reprocessed have seldom been reported. Here, permanently cross-linked OBCs (OBCXs) and dynamically cross-linked OBCs, or OBC covalent adaptable networks (CANs), were synthesized by melt-state reactive processing of neat OBCs with various crystallinities and melt flow indices (MFIs). The OBC CANs are capable of dialkylamino disulfide dynamic chemistry via the grafting of bis(2,2,6,6-tetramethyl-4-piperidyl methacrylate) disulfide, or BiTEMPS methacrylate, cross-linkers onto OBC backbone chains. Thermomechanical characterizations indicate that increasing crystallinity and decreasing MFI in precursor OBCs lead to higher cross-link densities in OBCXs and OBC CANs. Dynamically cross-linking OBCs into CANs also significantly improves their elevated-temperature creep resistance. Stress relaxation results of OBC CANs indicate an increased average relaxation time with greater cross-link density. Distinct from other CANs capable of dialkylamino disulfide chemistry, the stress relaxation behaviors of OBC CANs of higher cross-link density show evident dependence on their network viscoelasticities. In OBC CANs of lower cross-link density, the dynamic chemistry more strongly governs their stress relaxation behaviors. Finally, the OBC CANs exhibit full cross-link density and thermomechanical property recovery after reprocessing, whereas the OBCXs cannot be reprocessed due to their irreversible cross-links.

Ultraflexible, cost-effective and scalable polymer-based phase change composites via chemical cross-linking for wearable thermal management

Phase change materials (PCMs) offer great potential for realizing zero-energy thermal management due to superior thermal storage and stable phase-change temperatures. However, liquid leakage and solid rigidity of PCMs are long-standing challenges for PCM-based wearable thermal regulation. Here, we report a facile and cost-effective chemical cross-linking strategy to develop ultraflexible polymer-based phase change composites with a dual 3D crosslinked network of olefin block copolymers (OBC) and styrene-ethylene-butylene-styrene (SEBS) in paraffin wax (PW). The C-C bond-enhanced OBC-SEBS networks synergistically improve the mechanical, thermal, and leakage-proof properties of PW@OBC-SEBS. Notably, the proposed peroxide-initiated chemical cross-linking method overcomes the limitations of conventional physical blending methods and thus can be applicable across diverse polymer matrices. We further demonstrate a portable and flexible PW@OBC-SEBS module that maintains a comfortable temperature range of 39–42 °C for personal thermotherapy. Our work provides a promising route to fabricate scalable polymer-based phase change composite for wearable thermal management.

Research of the thermal storage properties of thermally conductive carbon fiber-reinforced paraffin/olefin block copolymer composite phase change materials with thermotropic flexibility

This study focuses on the fabrication and evaluation of paraffin (PA)/olefin block copolymer (OBC)/carbon fiber (CF) composite phase change materials (CPCMs) prepared using the melt impregnation process. The resultant PA/OBC/CF CPCMs exhibit superior thermal stability below 200 °C and maintain excellent shape stability at 60 °C. These characteristics are attributed to the alternating soft and hard segments of OBC, wherein the hard segments prevent liquid leakage from PA. The distinct structure of OBC further lends flexibility and recyclability to the PA/OBC/CF CPCMs. The latent heat of these CPCMs ranges from 169.1 to 197.6 J/g. Notably, the CPCMs variant (PA/OBC/CF-1) with 2 wt% CF addition retains 95 % of its initial latent heat even after 100 thermal cycles, thereby demonstrating superior cycling stability. The thermal conductivity of CPCMs with 10 wt% CF is 1.3 times that of pure PA. This significant improvement in thermal conductivity is attributed to the heat conduction pathways provided by the fibrous CF. These results indicate that the fabricated CPCMs offer substantial promise for utilization in low-temperature waste heat recovery applications.

A novel flexible composite phase change material with enhanced toughness and shape stability for battery thermal management

The application of flexible composite phase change materials (FCPCM) in the thermal management of batteries has been widely studied. However, flexible materials can sometimes tear, so improved toughness and morphological stability are required. In this work, a new stable flexible composite phase change material, with good toughness is prepared, which is composed of paraffin, Styrene Ethylene Butylene Styrene (SEBS), Olefin Block Copolymer (OBC) and Expanded Graphite (EG). The thermal properties, toughness, morphological stability, and other properties of the fabricated FCPCMs are tested, and battery thermal management experiments are conducted to explore its thermal management potential. The results show that the elongation at break are about 150 % and 240 % of the FCPCM at the same temperature with OBC as the supporting material at 25 °C and 40 °C, respectively, which shows good toughness. It can still maintain a stable form under the high-temperature condition of 110 °C. The physical and chemical compatibility of each component of the FCPCM is good. The 24 h leakage rate is maintained below 1 %, which is only 56 % of the leakage rate of the FCPCM with OBC as the support material. In general, 8 wt% SEBS and 8 wt% OBC are the best ratio. In addition, the battery thermal management experiment shows that the FCPCM can control the battery temperature at 49.3 °C at a 2C rate, which is 10 °C lower than the condition without FCPCM. The FCPCM reduces the temperature fluctuation of the battery by at least 1 °C, whether it is charged at 1C or 2C. This shows good thermal management potential.

Flexible composite phase change material with improved hydrophobicity and thermal conductivity characters for thermal management

Phase change materials (PCMs) are increasingly popularized in the field of passive thermal management. However, several inherent defects such as strong rigidity, weak hydrophobicity and poor thermal conductivity have seriously hindered their widespread development. This work introduces a novel composite PCM with thermally-induced flexibility as well as enhanced hydrophobic and thermally conductive abilities, which is synthetized by physical melting and mixing of palmitic acid (PA), olefin block copolymer (OBC) and hexagonal boron nitride (h-BN). Experimental results demonstrate that OBC helps to realize flexibility and hydrophobicity, while h-BN is essential to spurring thermal conductivity growth but incapable of impairing surface wettability. 66.5 wt% PA, 28.5 wt% OBC and 5 wt% h-BN are convinced to be the appropriate formula of composite for the hydrophobic modification and the weighing between thermal conductivity and thermal storage capacity. The as-prepared flexible PCM reverses its surface wettability from hydrophilicity to hydrophobicity, accompanied by 27.0 % increment in water contact angle compared with the case of using only PA. The resultant also presents fine physiochemical compatibility, suitable phase transition parameters, and excellent thermal stability and reliability. Furthermore, highly reliable hydrophobicity is confirmed under four harsh conditions for prolonged application.

Hexagonal boron nitride-induced lamellar-structured flexible phase change film for temperature-controlled information storage and wearable thermal regulation

The development of multifunctional composite phase change materials has emerged as a popular research field to achieve efficient thermal energy storage and management across diverse application scenarios. Herein, a novel flexible reversible thermochromic phase change film (TC-PCMs/nBN/OBC) has been proposed. The film comprises a thermochromic compound, hexagonal boron nitride (h-BN), and olefin block copolymers (OBC), and features a layered structure with h-BN embedded laterally in OBC. This design enhances thermal conductivity and confers reversible thermochromic ability, as well as excellent flexibility. The TC-PCMs/nBN/OBC film can perform multiple functions, including thermal storage, light-to-thermal conversion, and temperature-controlled information storage. Additionally, a sandwich-like structure of the multifunctional smart flexible device (TC-PCMs/10BN/OBC-CC) is fabricated using TC-PCMs/10BN/OBC and conductive cloth via easy layer-by-layer assembly. This flexible device is simple to prepare, retains the excellent comprehensive properties of TC-PCMs/nBN/OBC. Moreover, the presence of conductive cloth enabled this device to achieve good electric-to-thermal conversion efficiency (86.5 %). Overall, the results demonstrate that TC-PCMs/10BN/OBC can meet diverse application requirements.

One-step reactive processing of vitrimeric thermoplastic polyolefin elastomer with greatly improved thermo-mechanical property

Chemically crosslinking can enhance mechanical strength, dimensional stability and heat-resistance of thermoplastic polyolefin elastomers. However, chemically crosslinked elastomers suffer from reduction of flowability and strong shrinkage after reprocessing. In this work, inspired by vitrimer concept, olefin block copolymer (OBC) elastomer was chemically modified with dynamic boronic ester bond through one-step reactive processing. Based on the swelling test, FT-IR sperctra and DMA investigation, OBC vitrimer with tunable composition of dynamic Boron–Oxygen(B–O) bonds has been successfully prepared. Based on classical Arrhenius theory, the calculated activation energy (Ea) of OBC vitrimers ranges from 7.838 kJ/mol to 46.851 kJ/mol due to combined effect of chemical and dyanmic crosslinks. The prepared OBC vitrimers shows good creep-resistance, great reprocessability and good mechanical properties including tensile strength up to 15 MPa, elongation at break of 2300%, and elastic recovery of 90% at 300% strain. Interestingly, OBC vitrimers show significantly improved high-temperature mechancial property, i.e., tensile strength of ∼0.12 MPa and elongation excess 1200% at 120 °C where both OBC and OBC-DCP samples break instantly. Therefore, our work shows a promising industrial-scale strategy to prepare vitrimer elastomers via reactive processing, and provides guidance for molecular design of high-performance vitrimeric polyolefin elastomers.

Resilient and reprocessable physical gels based on crystalline olefin block copolymer elastomer and mineral oil toward optically transparent electronic packaging

Due to the urgent demand of high-performance electronic packaging materials, thermoplastic elastomer physical gels (TPEG) have emerged as a promising alternative to traditional hydrogels and crosslinked rubbers due to their good thermal stability and reprocessability. In this work, olefin block copolymer (OBC) elastomer was blended with soft-block selective mineral oil (MO) to tune the mechanical property and transparency. It was found that the MO molecules can disperse well within amorphous phase with effective filling ratio ranging from 9.85 wt% to 44.82 wt%. The hard segments pack into spherulites and gradually develop into segregated crystals of ∼800 nm with the increase of MO concentration. Interestingly, fast quenching induces breakout crystallization morphology while thermal annealing at 130 °C can result in confined crystallization morphology with increased domain spacing due to the selective distributed MO since the corrected crystallinity remains constant and the crystal structure maintains as orthogonal crystals. Due to the combined effect of weak mesophase separation and decreased crystal size, OBC gels has an increased transparency up to 80% in visible region. The extensibility and cyclic property of OBC-based TPEG were finely tuned along with high transparency and excellent dielectric insulation property. Furthermore, the OBC gels are highly stable over a wide temperature and can be recycled. Overall, our work highlights the potential of thermoplastic elastomer physical gels as a sustainable and high-performance alternative for transparent electronics packaging materials.

Preparation and Characterization of Flexible Phase Change Material for Compact Electrical Applications

The development of advances in digital technologies, the compact electronic devices plays an important role but the space constraints and irregular surfaces in the device makes it hard to dissipate heat with the help of external medium. They overheat in most of the cases and become a common cause for failure of the device. Phase Change Materials (PCM) release or absorb heat at its melting temperature to its better thermal management. But the PCM have limitations as its brittleness could not occupy the irregular surfaces of compact electronic devices and undergo deformations during operation, a new class of material Flexible PCM (FPCM) developed to endure a certain amount of deformation and make compact contact with irregular surfaces of objects, making them ideal for many smart applications. In this work, the newer thin film FPCM are prepared using Olefin Block Copolymer and paraffin wax at different combinations on mass basis and field emission SEM and XRD characterization of samples are studied and reported. This paper presents selection of optimal PCM and copolymer, preparation of FPCM and detailed analysis of the sample report and electrical device applications. This report provides a basis for implementing and optimizing phase change thermal management techniques in electrical devices. The experimental results shows PCM 45 and 55 wt% co-polymer combination of FPCM having better thermal management in Electrical Applications. Thermal analysis will be studied in future. HIGHLIGHTS Flexible Phase Change Materials (FPCM) prepared and properties are studied Olefin Block Copolymer and paraffin wax at different combinations on mass basis developed and studied FPCM used for Compact Electronic Applications considered as LED Lamb GRAPHICAL ABSTRACT

Lightweight olefin block copolymers foams with shrinkable and recoverable performance via supercritical CO2 foaming

Thermoplastic elastomer foams with gas-rich structures occupy a high specific surface/volume ratio, which will take up lots of space for storage and transportation. Herein, micro-crosslinked olefin block copolymers (OBC) foams with shrinkable and recoverable functions were prepared via supercritical CO2 foaming to subtly solve the storage problem, and the shrinkage and recovery mechanisms were studied. The storage volume of OBC foams could shrink up to ∼78.5 % and maintain low volume condition for a long time through vacuum sealing technology. Meanwhile, the shrunk OBC foams could also be quickly and fully recovered by N2-assisted post-processing because of the regulation of gas exchange. And OBC foams with a density of 0.028 g/cm3 were prepared successfully. The compressive properties of OBC foams were investigated. Related design strategies can significantly reduce the transportation costs and energy consumption of OBC foams and are expected to be applied to other thermoplastic elastomers.

A novel form-stable phase change material based on elastomeric copolymer and carbon nanotubes with photo-thermal conversion performance

In this paper, the composite form-stable phase change materials (FSPCMs) with a photo-thermal conversion function for solar thermal energy storage were prepared using paraffin wax (PW) as a PCM, both styrene ethylene butylene styrene (SEBS) and olefin block copolymer (OBC) as supporting materials, and carbon nanotubes (CNT) as an efficient light-absorbing material. The PW/SEBS + OBC composite with 80 wt% PW can maintain a stable shape without leakage above the phase change temperature. The latent heat of the PW/SEBS + OBC/CNT composite with 8 % CNT is 136.2 J/g, and the entrapment efficiency is 71.2 %. The prepared composite FSPCMs have good flexibility, thermal reliability, and thermal stability. And the absorbance of PW/SEBS + OBC/CNT composite is higher than that of pure PW and PW/SEBS + OBC. Moreover, the photo-thermal conversion efficiency of PW/SEBS + OBC/CNT composite with 2 wt% CNT, 4 wt% CNT, 6 wt% CNT, and 8 wt% CNT is 72.9 %, 81.9 %, 82.3 %, and 83.2 %, respectively. The prepared composite FSPCMs have a promising application in the field of solar energy storage.