The influence of epoxide resin viscosity on impregnation of fiber reinforcement

J of Applied Polymer Sci

et al. 2017

A set of novel bio-based star-shaped thermoset resins was synthesized via ring-opening polymerization of lactide and employing different multi-hydroxyl core molecules, including ethylene glycol, glycerol, and erythritol. The branches were endfunctionalized with methacrylic anhydride. The effect of the core molecule on the melt viscosity, the curing behavior of the thermosets and also, the thermomechanical properties of the cured resins were investigated. Resins were characterized by Fourier-transform infrared spectroscopy, 13 C-NMR, and 1 H-NMR to confirm the chemical structure. Rheological analysis and differential scanning calorimetry analysis were performed to obtain the melt viscosity and the curing behavior of the studied star-shaped resins. Thermomechanical properties of the cured resins were also measured by dynamic mechanical analysis. The erythritol-based resin had superior thermomechanical properties compared to the other resins and also, lower melt viscosity compared to the glycerol-based resin. These are of desired characteristics for a resin, intended to be used as a matrix for the structural composites. Thermomechanical properties of the cured resins were also compared to a commercial unsaturated polyester resin and the experimental results indicated that erythritol-based resin with 82% bio-based content has superior thermomechanical properties, compared to the commercial polyester resin. Results of this study indicated that although core molecule with higher number of hydroxyl groups results in resins with better thermomechanical properties, number of hydroxyl groups is not the only governing factor for average molecular weight and melt viscosity of the uncured S-LA resins.

Section: Resultsmentioning

confidence: 99%

Synthesis and characterization of methacrylated star‐shaped poly(lactic acid) employing core molecules with different hydroxyl groups

Esmaeili

J of Applied Polymer Sci

et al. 2017

“…The resistance to flow of a liquid is expressed in terms of the viscosity. The viscosity is of importance for manufacturing processes, maximizing the production efficiency, improving processability as well as for improving the impregnation efficiency of the matrix to the reinforcement fiber for composite production [86]. It is believed that the linear PLA shows a long Newtonian plateau typical of polymers having a linear chain structure (at low to moderate oscillation frequencies <100 rad/sec).…”

Section: Rheological Properties and Curing Kinetics Of The Star-shapementioning

confidence: 99%

Star-shaped lactic acid based systems and their thermosetting resins; synthesis, characterization, potential opportunities and drawbacks

European Polymer Journal

2017

Shortcomings of the conventional PLA synthesis methods have encouraged researchers to investigate on alternative methods for PLA synthesis. Utilization of chain extenders is an effective way to achieve high MW polymers. The concept of using star-shaped resins as the reinforced matrices for biocomposites or in biomedical applications is gaining more and more attention day by day. Star-shaped lactic acid based resins are a class of branched resins with a multifunctional core molecule and lactic acid branches. In order to increase the reactivity of branches, the star-shaped resin oligomers can get end-functionalized which yields in a crosslinkable product. Changing the architecture of a polymer from a linear to a multiarm or hyperbranched one, would change its chemical, diffusional and physical-mechanical properties. This review paper presents the current state and recent advances in the synthesis, characterization, properties and applications of the star-shaped resins made from lactic acid and multi-hydroxyl core molecules with a focus on the role of the morphology of the polymer on the 3 properties of resins. Rheological, physiochemical and thermomechanical properties of to date synthesized star-shaped resins are compared and discussed. Special emphasis would be made on potential opportunities, probable applications and also gaps and drawbacks concerning these systems. This review aims to provide useful information to help future development of efficient, highly engineered bioresins which can be especially designed for a certain application.

“…Lactic acid (LA) is a renewable resource abundantly available via the fermentation of carbohydrates . A limitation of the impregnation of fibers with the thermoplast polylactic acid (PLA) viscous matrix is that it slows down the manufacturing process and also reduces the mechanical strength of the composites . Thermosets have the inherent advantage of lower viscosity, which results in better processability and improved impregnation of fibers.…”

Section: Introductionmentioning

confidence: 99%

“…1 -3 A limitation of the impregnation of fibers with the thermoplast polylactic acid (PLA) viscous matrix is that it slows down the manufacturing process and also reduces the mechanical strength of the composites. 4,5 Thermosets have the inherent advantage of lower viscosity, which results in better processability and improved impregnation of fibers. These characteristics make thermosets desirable for reinforced composite applications.…”

Section: Introductionmentioning

confidence: 99%

Effect of lactic acid chain length on thermomechanical properties of star‐LA‐xylitol resins and jute reinforced biocomposites

Esmaeili

2017

Polymer International

Star‐shaped bio‐based resins were synthesized by direct condensation of lactic acid (LA) with xylitol followed by end‐functionalizing of branches by methacrylic anhydride with three different LA chain lengths (3, 5 and 7). The thermomechanical and structural properties of the resins were characterized by 13C NMR, Fourier transform IR spectroscopy, rheometry, DSC, dynamic mechanical analysis (DMA), TGA and flexural and tensile tests. An evaluation of the effect of chain length on the synthesized resins showed that the resin with five LAs exhibited the most favorable thermomechanical properties. Also, the resin's glass transition temperature (103 °C) was substantially higher than that of the thermoplast PLA (ca 55 °C). The resin had low viscosity at its processing temperature (80 °C). The compatibility of the resin with natural fibers was investigated for biocomposite manufacturing. Finally, composites were produced from the n5‐resin (80 wt% fiber content) using jute fiber. The thermomechanical and morphological properties of the biocomposites were compared with jute‐PLA composites and a hybrid composite made of the impregnated jute fibers with n5 resin and PLA. SEM and DMA showed that the n5‐jute composites had better mechanical properties than the other composites produced. Inexpensive monomers, good thermomechanical properties and good processability of the n5 resin make the resin comparable with commercial unsaturated polyester resins. © 2017 Society of Chemical Industry