Renewable pressure-sensitive adhesive (PSA) is an emerging field in adhesive industries as it is an excellent green alternative to depleting petroleum-sourced adhesives. Herein, we report the development of novel bio-sourced UV-curable PSAs with ∼50% biomass content originating from alkali lignin, cardanol, and linseed oil. Bio-based prepolymers cardanoldiol acrylate (CDA) and acrylated epoxidized linseed oil (AELO) were synthesized and used to prepare polyurethane acrylate (PUA)-based PSA systems. Alkali-lignin-based acrylates (LAs) in the liquid phase were incorporated into the PUA/AELO PSA system at 10–30 wt % loading to tune the functional properties. The Fourier transform infrared spectroscopy (FTIR) analysis showed weakened cross-linking in the PSA systems on LA addition, which is desirable for removable PSA applications. The single glass-transition temperature (T g) noticed in all of the PSA formulations revealed good miscibility among the oligomers/prepolymers. The viscoelastic window also confirmed that the incorporation of 10–20% LA could improve the viscoelastic properties effectively to be used as removable PSAs. The addition of 20% LA into the PUA-based PSA system showed reasonable tackiness, lap shear adhesion (166 kPa), and 180° peel strength (∼2.1 N/25 mm) for possible nonstructural or semistructural applications. Lignin improved the thermal stability by hindering the degradation rate even at higher temperatures. Therefore, lignin-based PSAs with a high bio-based content paved the way of replacing petro-sourced PSA by proper tuning of the lignin content and modifications.
Abstract. High-energy mechanical alloying method was used to prepare Al-12Si-xZrC (x = 0, 5, 10, 15 wt. %) nanocomposites. Cylindrical preforms were prepared with an initial preform density of 89% by using a suitable die and punch assembly. The preforms were sintered in a muffle furnace with an inert gas atmosphere at a temperature of 550°C, followed by cooling until room temperature has been attained. Scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques were used to characterize the composites. Pin-on-disc wear testing machine was used to determine the tribological properties of the prepared composites. The results show that the wear loss reduced with increasing the reinforcement content and coefficient of friction increases gradually. Normally, solid state methods are used to produce composites with high mechanical properties, because these methods deliver a uniform distribution of reinforcing phase particle in the matrix material [6][7][8][9][10]. Some trials were conducted to fabricate Al-12Si-xZrC nanocomposites using different techniques, but the mechanical alloying method is a suitable technique to fabricate Al-12Si-xZrC nanocomposites. No attempt has been made to fabricate Al matrix composites reinforced with ZrC particles using the P/M method. In this present paper, an effort is made to study the outcome of wear behavior of Al-12Si-xZrC nanocomposites prepared with the mechanical alloying method. These composites were characterized using SEM and XRD. The wear behavior was calculated using the weight loss method. The worn surfaces and wear debris were characterized using SEM. Experimental procedure2.1. Materials. Aluminium and silicon with 99.5% purity and particle size of 44 µm were purchased from Metal Powder Company Limited, Thirumangalam, Tamilnadu, India, and the ZrC powder with a high, 99.9% purity and particle size of 400 nm was purchased from US Research Nanomaterials, Inc., USA. The individual powders were pulverized and mixed in a high-energy ball mill with ball-to-powder weight ratio of 20:1. The milling was done at a constant speed of 300 rpm in a wet medium with a presence of toluene to avoid oxidation and agglomeration. Scanning electron microscope images were used for the analysis of mixed powder particles. Fig. 1 shows the received powders of aluminium, silicon, and zirconium carbide. From the SEM images, it can be visualized that aluminium was spherical in shape, silicon was flattened and nano-zirconium carbide had a cubic crystal shape.
Green and sustainable pressure sensitive adhesive (PSA) with higher biomass content is an upcoming area in the adhesive industries, owing to its potential to replace crude-oil-based nonrenewable PSAs. Herein, we report a novel bio-based PSA with 89–92% biomass content, majorly derived from cardanol, a component derived from cashew nut shell liquid (CNSL) and from vanillin, a lignin derivative. The control PSA copolyesters were synthesized by the copolymerization of epoxidized cardanol with sebacic acid. Vanillin epoxide (VE) was incorporated into the prepolymer in different proportions (10–30 wt %) to tune its functional behavior through ring opening esterification and etherification. A single glass transition temperature (T g) of all the samples revealed good miscibility of the system with desired transition temperature range (−16 to −21 °C) as applicable for PSAs. The 90° peel strength of the formulations gradually improved upon an increase in VE loading with an optimum value of 4.82 ± 0.38 N/25 mm, revealing their suitability for nonstructural and semistructural applications. A similar trend is noticed for the lap shear analysis of metal joints, wherein the PSA with 30% VE loading showcased excellent shear resistance of 2.61 ± 0.08 MPa. The PSA showed reasonable shear adhesive performance for plastics joints and also good adhesion even after exposure to water and liquid nitrogen. The viscoelastic properties of uncured PSA formulations were found to satisfy the criteria for removable PSAs. The samples are found to be thermally stable up to 180 °C without any sort of degradation, indicating potential for high temperature PSA applications. Thus, vanillin and cardanol incorporated PSAs with ∼90% biomass content pave the way for substituting the petro-based PSAs for nonstructural and semistructural applications being renewable and eco-friendly.
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