Search

In this study, a fully biodegradable ultra-light poly(lactic acid)/silicon dioxide (PLA/SiO2) aerogel nanocomposite with ultra-low thermal conductivity was successfully fabricated. PLA used was a produced from lactic acid, where the lactic acid has been produced from carbohydrates. The rheological properties of PLA were enhanced by diphenylmethane diisocyanate (MDI). The foaming properties, cell density, cell size uniformity, mechanical properties and thermal conductivity and thermal diffusivity of PLA were further improved by SiO2 aerogel, and finally the ultra-low density foamed material was prepared by supercritical CO2. The density of PLA foam can be as low as 0.02 g/cm3 and the thermal conductivity as low as 0.02628 W/m·K. The PLA-based composites can be used in many fields such as thermal insulation, vibration damping and packaging, and can be fully biodegradable and sustainable throughout their life cycle, which meets the global trend of energy saving and emission reduction.

Herein, we report the preparation and characterisation of fluororubber coated superhydrophobic Poly (ethylene tetrapthalate) (PET) fabric and polyurethane (PU) sponge. The coating surface structure...

Herein, dopamine is grafted onto multi-walled carbon nanotubes (MWCNTs), and then grafted dopamine is used as a chemical activation point to initiate the in-situ synthesis of silver nanoparticles (Ag-NPs). The foam technology with supercritical N2 (Sc-N2) gas was used to prepare a lightweight and flexible silicone rubber foam material with efficient electromagnetic shielding performance. The prepared material has uniform cells and a density of only 0.3 g/cm3. The electrical conductivity can be achieved as high as 5.69 S/m. At the same time, the optimal modified conductive filler MWCNTs conditions are determined: DOPA concentration is 2 g/L, deposition time is 18 h, formaldehyde concentration is 5 g/L and AgNO3 concentration is 16 g/L. From the perspective of electromagnetic interference shielding performance (EMI SE), the value of prepared silicone rubber foam with 15 parts of MWCNT-PDA-Ag (VMPA15) can reach 36 dB, far exceeding the commercial requirement (20 dB). The EMI shielding performance is also improved with the increased thickness of the sample. When the sample thickness is 10 mm, the EMI SE value can be as high as 52 dB; more importantly, this type of VMPA foam has a shielding mechanism based on absorption, which is the most effective for solving the problem of secondary magnetic pollution caused by electromagnetic wave reflection.

As a class of smart material, shape memory materials have a great attention due to its potential applications in sensors, textiles, aerospace engineering and medical devices. Herein, we prepared a trans-1,4-polyisoprene (TPI) foam with shape memory properties by radiation crosslinking with the supercritical CO2 foaming method. Firstly, TPI micro-crosslinks were prepared by radiation crosslinking, and then supercritical foaming were carried out. The effect of doses (30 kGy–150 kGy) on TPI foams was investigated. The shape memory behavior of the TPI composite material depends on the crystallinity of the material. The radiation crosslinking method is more suitable to improve the shape memory properties of TPI foam materials. The increase in the dose increases the degree of crosslinking of the material, however it will not crystallize the material significantly. The pores of the microcellular foam material always have a closed-cell structure with the increased dose. While the shape of the cell changes from a honeycomb structure to a circular structure, the cell density increases continuously along with the decreased cell size, and the cell wall changes significantly. As the cell wall thickness increases, the density also increases; the recovery rate of the material increases. The material can achieve a recovery rate of 85% or even ~100% in only 6 s at 100 kGy dose. TPI foamed materials with a high dose can undergo shape recovery at relatively low temperatures. Dielectric study reveals that the introduction of cells can greatly reduce the dielectric constant and dielectric loss of the materials, which improve the insulation performance of TPI. The prepared TPI shape memory materials can be applied in the field of item packaging with good protection and recyclability.

The current research work demonstrates preparation and characterization of Reduced Graphene Oxide (rGO)@ High-Density Polyethylene (HDPE) aerogel coated Natural Rubber Latex foam (NRLF) with superhydrophobic and superoleophilic character, good sorption capacity for oil-water separation, high electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) of the same were studied. The coated NRLF was prepared by using a solution of rGO and HDPE in xylene solvent with cooling process to result into thermally induced phase separation of the graphene and Polyethylene molecular network. The rGO modified HDPE aerogel coated NRLF showed superhydrophobicity with static water contact angle > 150°. The rGO@HDPE aerogel coated NRLF with 2 wt% rGO has reached EMI SE value of 24 dB, meeting commercial requirements. The electrical conductivity, EMI SE and the hydrophobicity of the composites significantly improved after mixing rGO into HDPE sol. This prepared superhydrophobic NRLF with high electric conductivity may find attractive application in oil-water separation and EMI Shielding, which would also be economically favored option in the current scenario.

Propylene/1-butene (PPB) copolymer foam materials are successfully prepared by supercritical CO2 and the effects of different 1-butene content on the mechanical, crystallization, foaming, and cushioning properties of prepared PPB foam material are investigated. The decrease in hardness value (from 90 to 67), tensile strength (from 37.8 MPa to 32.5 MPa), and bending strength (from 40.6 MPa to 34 MPa) of PPB materials along with the enhanced impact strength (from 3834.3 MJ/m2 to 6699.65 MJ/m2) are a result of high 1-butene content. The increased foaming ratio and broadened foaming temperature window of PPB materials achieved with increased 1-butene content. Energy absorption efficiency has enhanced (from 0.678 to 0.847), and ideal parameters also improved significantly (from 0.242 to 0.303) at the same density along with the cushioning performance of PPB foaming materials. Low-density, high 1-butene content PPB materials have a better energy absorption effect with a lower permissible stress.

Developing light-weight fluororubber foam is a challenging task mainly because of its high density and the easy shrinkage of foam. A promising approach to overcome this challenge is the use of supercritical fluid (SCF) foaming method. Herein, an ultra-light, heat-resistant, and adiabatic fluororubber foam was developed through preparing fluororubber gel, followed by using eco-friendly supercritical nitrogen (SC N2) as blowing agent and the properties of prepared foam with different graphene content (0, 2, 4, 6, 8, 10 phr) were investigated. The developed fluororubber foam has the closed-cell structure as the general rubber foam and ultra-light property (i.e. density of 9 mg/cm3). Good flexibility and compressibility, as well as excellent heat resistance (foam can withstand at high temperature above 200 °C for which there is no obvious change in fluororubber foam) and thermal insulation (thermal conductivity in the range 0.020−0.032 W/mK) meet well the desirable properties for thermal insulation application, which supports fluororubber foams to be a promising material.

Thermal insulation and excellent weatherability microcellular foams based on lightweight polymer are successfully developed from chlorinated polyethylene rubber/polyvinyl chloride (CM/PVC) compounds through electron beam irradiation cross-linking and chemical foaming technology. The effect of electron beam irradiation on the blends of CM/PVC foam prepared with different compositions starting from 70:30 to 50:50 (CM:PVC) with varied radiation doses from 30 to 70 kGy and varied chemical blowing agent contents from 10 to 20 phr has been studied. The aim was to investigate the influence of the different blending ratio, the chemical blowing agent content and the irradiation dose on physical and mechanical properties and morphology of the cellular structure in the produced foams. Thermal conductivity of CM/PVC compounds foams achieved in this study is as low as 0.0374W/mK.

The oil-water separation has made an attention due to over-increased production of oily water from the industrial process and everyday routine of humans. The current work reports on preparation and characterization of High-Density Polyethylene (HDPE) aerogel coated Natural Rubber Latex foam (NRLF) with superhydrophobic and superoleophilic character, good sorption capacity for oil-water separation application and were investigated. The HDPE aerogel and the coated NRLF material was prepared by a cooling process from a solution of HDPE in xylene solvent (HDPE sole, which resulted into thermally induced phase separation of the Polyethylene molecular network). The HDPE aerogel coated NRLF displayed a porous surface morphology with particle-like structural features. The HDPE aerogel coated NRLF showed superhydrophobicity with static water contact angle >150°. The effect and recyclability of the HDPE aerogel coated NRLF for oil-water separation was investigated using different model oil solvents to explore their repeatable application in oil spill clean-up process. Modified NRLF shows an excellent mechanical property (compressibility). The average modulus and average stiffness of the modified NRLF increased with the increase of the concentration of HDPE sol. The modified superhydrophobic sponge has good durability under acid and base conditions.