Epoxidation of high-linolenic perilla oil was carried out in the presence of solid acidic ion-exchange resin at varying reaction temperatures for 8 h. A pseudo two-phase kinetic model that captures the differences in reactivity of double bonds at various positions in the fatty acid of a triglyceride molecule during both epoxy formation and cleavage was developed. The proposed model is based on the Langmuir-Hinshelwood-Hougen-Watson (L-H-H-W) postulates and considers the adsorption of formic acid on the catalyst as the rate-determining step. To estimate the kinetic rate constants of various reactions, genetic algorithm was used to fit experimentally obtained iodine and epoxy values of epoxidized perilla oil. A re-parametrized form of Arrhenius equation was used in the proposed model to facilitate the precise estimation of parameters with least computational effort. The obtainment of the least error between experimentally determined and theoretically predicted iodine and epoxy values indicates the robustness of the proposed model.
Major limitation for use of epoxy thermosets in engineering applications is its sudden brittle failure. In the present study dipropylene glycol dibenzoate (DPGDB) based plasticizer is used to modify diglycidyl ether of bisphenol A (DEGEBA) based epoxy resin system via simple blending technique. Bio‐based epoxidized linseed oil was also used to modify epoxy resin system and compared with DPGDB modified resin. For DPGDB modified resin storage modulus and loss modulus of the epoxy system modified with 10% plasticizer increased by 7.54% and 12.24%, respectively. The primary mechanism responsible for such behavior is improved crosslinking density. With 5% plasticizer loading, flexural strength increased by 21%. There was an improvement of 312.74% in strain at failure for 10% plasticizer loading, while preserving its mechanical strength. It was found that DPGDB based modification was better than epoxidized linseed oil modification.
more » « less- Award ID(s):
- 1735971
- NSF-PAR ID:
- 10452563
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Applied Polymer Science
- Volume:
- 138
- Issue:
- 28
- ISSN:
- 0021-8995
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
The performance of bonded joints of carbon fiber reinforced polymer (CFRP) and steel relies on the mechanical properties of the adhesive used. Despite the high strength and modulus of epoxy adhesives, their brittleness limits their application to defect‐sensitive structures. The development of interpenetrating polymer networks (IPNs), either homogeneous or phase separated, provides a route to toughen the epoxy while maintaining its high strength and modulus. Microphase separated IPNs consisting of a diglycidyl ether of bisphenol A‐based epoxy resin and a thermoset with high toughness, polydicyclopentadiene (PDCPD), has been previously shown to demonstrate superior combinations of strength and toughness. This work investigates the most critical adhesive properties that affect bond strength by characterizing CFRP‐steel double‐lap shear joints containing the epoxy resin–PDCPD blend as the adhesive, using a wet lay‐up manufacturing technique. The epoxy resin–PDCPD blend adhesives realized much higher bond strengths compared to either neat epoxy or neat PDCPD. Correlations between the bond strength and the bulk material properties are presented. Theoretical calculation of the bond strength indicates that the higher bond strength that can be achieved by using the epoxy resin–PDCPD blend adhesive is due to the increased shear toughness of the new formulations. POLYM. ENG. SCI., 60:104–112, 2020. © 2019 Society of Plastics Engineers
-
null (Ed.)Fully biodegradable unidirectional green composites with excellent tensile properties were fabricated by combining one of the highest specific strength liquid crystalline cellulose (LCC) fibers as the reinforcement and microfibrillated cellulose (MFC) strengthened nonedible avocado seed starch (AVS)-based resin. MFC/AVS resin was crosslinked using 1,2,3,4-butane tetracarboxylic acid as well as plasticized using sorbitol or glycerol. Combination of alkali, mechanical and thermal treatments improved LCC fiber fracture stress from 1.5 GPa to over 1.9 GPa and Young’s modulus from 49 to 64 GPa. While the type and amount of plasticizer used changed the fracture strain of MFC/AVS resin, they also showed significant influence on the mechanical properties of the unidirectional composites. These composites prepared by hand lay-up, based on modified LCC fibers resulted in fracture stress of over 380 MPa and Young’s modulus of 19.5 GPa with less than 40% fiber content. Results suggest that there is scope to improve the properties further by using higher fiber content and automated manufacturing. These ‘green’ composites with excellent strength and stiffness may be used in many applications such as construction, automobile and others.more » « less
-
more » « less
ABSTRACT Hyperbranched aromatic polyamide (HBP) was grafted successfully onto carbon fibers (CFs) on the basis of solution polymerization to enhance the interfacial adhesion strength of CF‐reinforced epoxy resin composites. The microstructure and interfacial properties of the CFs before and after decoration were researched. The results indicate that HBP was deposited uniformly onto the CFs with γ‐aminopropyl triethoxysilane as the bridging agent. The active groups, roughness, and surface energy of the modified fiber [hyperbranched aromatic polyamide grafted carbon fiber (CF–HBP)] increased visibly in comparison with those of the untreated CFs. The CF–HBP composites revealed simultaneous remarkable enhancements (65.3, 34.3, and 84.8%) in their interfacial shear strength, flexural strength, and modulus, respectively; this was attributed to the improvement in the fiber–epoxy interface through enhanced chemical interactions, mechanical interlocking, and wettability. These agreed with the scanning electron microscopy observations from the fracture surface morphologies of the composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci.
2019 ,136 , 47232. -
null (Ed.)Semi-crystalline carbon biochar is derived from spent coffee grounds (SCG) by a controlled pyrolysis process at high temperature/pressure conditions. Obtained biochar is characterized using XRD, SEM, and TEM techniques. Biochar particles are in the micrometer range with nanostructured morphologies. The SCG biochar thus produced is used as reinforcement in epoxy resin to 3 D print samples using the direct-write (DW) method with 1 and 3 wt. % loadings. Rheology results show that the addition of biochar makes resin viscous, enabling it to be stable soon after print; however, it could also lead to clogging of resin in printer head. The printed samples are characterized for chemical, thermal and mechanical properties using FTIR, TGA, DMA and flexure tests. Storage modulus improved with 1 wt. % biochar addition up to 27.5% and flexural modulus and strength increased up to 55.55% and 43.30% respectively. However, with higher loading of 3 wt. % both viscoelastic and flexural properties of 3D printed samples drastically reduced thus undermining the feasibility of 3D printing biochar reinforced epoxies at higher loadings.more » « less
