The Effect of Glycol Derivatives on the Properties of Bio-Based Unsaturated Polyesters

The scope of the present study was to prepare fully bio-based unsaturated polyester resins (UPRs) with comparable properties to the commercial formulations. The focus was set on the determination of the optimal prepolymer formulation using the same set of diacids (itaconic and succinic acid) and different diols (propylene glycol, isosorbide and neopentyl glycol) or its equimolar mixtures, keeping the fixed molar ratio of 1:1:2.1 in all feed compositions. Instead of commonly used styrene, bio-based dimethyl itaconate was used as a reactive diluent (RD). The rheology of the obtained resins was studied in detail. The effect of the used diol on structural (FTIR), thermal (DSC), thermomechanical (DMA), and mechanical (tensile) properties was explained. The properties of UPRs were found to be highly dependent on the diol used in the prepolymer formulation. The UPR with an equimolar ratio of propylene glycol and neopentyl glycol was shown to be the most promising candidate to compete with the commercial petroleum-based resins.

Bio-based reactive diluents as sustainable replacements for styrene in MAESO resin

Four different biorenewable methacrylated/acrylated monomers, namely, methacrylated fatty acid (MFA), methacrylated eugenol (ME), isobornyl methacrylate (IM), and isobornyl acrylate (IA) were employed as reactive diluents (RDs) to replace styrene (St) in a maleinated acrylated epoxidized soybean oil (MAESO) resin to produce bio-based thermosetting resins using free radical polymerization. The curing kinetics, gelation times, double bond conversions, thermal–mechanical properties, and thermal stabilities of MAESO-RD resin systems were characterized using DSC, rheometer, FT-IR, DMA, and TGA. The results indicate that all four RD monomers possess high bio-based carbon content (BBC) ranging from 63.2 to 76.9% and low volatilities (less than 7 wt% loss after being held isothermally at 30 °C for 5 h). Moreover, the viscosity of the MAESO-RD systems can be tailored to acceptable levels to fit the requirements for liquid molding techniques. Because of the introduction of RDs to the MAESO resin, the reaction mixtures showed an improved reactivity and an accelerated reaction rate. FT-IR results showed that almost all the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C double bonds within MAESO-RD systems were converted. The glass transition temperatures (T_g) of the MAESO-RDs ranged from 44.8 to 100.8 °C, thus extending the range of application. More importantly, the T_g of MAESO-ME resin (98.1 °C) was comparable to that of MAESO-St resin (100.8 °C). Overall, this work provided four potential RDs candidates to completely replace styrene in the MAESO resin, with the ME monomer being the most promising one.

This paper reports four promising, sustainable reactive diluents to completely replace styrene for a commercially available MAESO resin.

Simple One-Pot Synthesis of Fully Biobased Unsaturated Polyester Resins Based on Itaconic Acid

For the preparation of fully biobased unsaturated polyester resins (UPRs), the replacement of styrene with alternate nonpetroleum-based monomers turned out to be one of the most challenging tasks. Its complexity lies in the fact that reactive diluents (RD) have to have low viscosity and volatility, good compatibility with prepolymer, and capability to homopolymerize and copolymerize with its unsaturations. In this context, we directed our efforts to develop fully biobased UPRs using the dialkyl itaconates as an alternative to styrene. Therefore, a series of 100% biobased UPRs were prepared from itaconic acid and 1,2-propandiol and diluted by dialkyl itaconates. The resins were characterized by Fourier transform infrared spectroscopy, NMR, volatility, and viscosity measurements, while the cured samples were characterized by dynamic mechanical properties, thermomechanical analysis, thermogravimetric analysis data, and tensile tests. The influence of RD structure on the properties of cured samples was discussed in detail. It was shown that the prepared resins had evaporation rates of dialkyl itaconates of several orders of magnitude less compared to styrene. The cured resins with dimethyl itaconate showed comparable or even better thermal and mechanical properties compared to the one with styrene. This investigation showed that itaconic acid and dialkyl itaconates are promising bioresources for the preparation of fully biobased UPRs for mass consumption.

The Influence of Crosslink Density on the Failure Behavior in Amorphous Polymers by Molecular Dynamics Simulations

The crosslink density plays a key role in the mechanical response of the amorphous polymers in previous experiments. However, the mechanism of the influence is still not clear. In this paper, the influence of crosslink density on the failure behavior under tension and shear in amorphous polymers is systematically studied using molecular dynamics simulations. The present results indicate that the ultimate stresses and the broken ratios (the broken bond number to all polymer chain number ratios) increase, as well as the ultimate strains decrease with increasing crosslink density. The strain concentration is clearer with the increase of crosslink density. In other words, a higher crosslink density leads to a higher strain concentration. Hence, the higher strain concentration further reduces the fracture strain. This study implies that the mechanical properties of amorphous polymers can be dominated for different applications by altering the molecular architecture.

Cure kinetics of exfoliated bio-based epoxy/clay nanocomposites developed from acrylated epoxidized castor oil and diglycidyl ether bisphenol A networks

A bio-based epoxy monomer was synthesized by acrylation of epoxidized castor oil (ECO). Subsequently, acrylated ECO (AECO)-toughened diglycidyl ether of bisphenol A (DGEBA) nanocomposites were prepared via sol–gel process with the addition of organically treated montmorillonite nanoclays. In this study, the curing kinetics of anhydride-cured DGEBA/AECO monomer with and without clays was studied by non-isothermal differential scanning calorimetry analysis. The apparent activation energy obtained by Flynn–Wall–Ozawa method was reduced from 63 to 59 kJ mol−1 and 69 to 61 kJ mol−1, respectively, with the addition of 1 wt% clay to the DGEBA/10 wt% AECO and DGEBA/20 wt% AECO systems, respectively. The two-parameter Šesták–Berggren autocatalytic model was used to obtain the reaction orders m and n, respectively. The curves obtained by the Málek method show good agreement with the experimental data for bio-based epoxy systems.

Effect of chain architecture on the compression behavior of nanoscale polyethylene particles

Polymeric particles with controlled internal molecular architectures play an important role as constituents in many composite materials for a number of emerging applications. In this study, classical molecular dynamics techniques are employed to predict the effect of chain architecture on the compression behavior of nanoscale polyethylene particles subjected to simulated flat-punch testing. Cross-linked, branched, and linear polyethylene chain architectures are each studied in the simulations. Results indicate that chain architecture has a significant influence on the mechanical properties of polyethylene nanoparticles, with the network configuration exhibiting higher compressive strengths than the branched and linear architectures. These findings are verified with simulations of bulk polyethylene. The compressive stress versus strain profiles of particles show four distinct regimes, differing with that of experimental micron-sized particles. The results of this study indicate that the mechanical response of polyethylene nanoparticles can be custom-tailored for specific applications by changing the molecular architecture.

Synthesis and Characterization of Soybean Oil Based Unsaturated Polyester Resin

A novel soybean oil monoglyceride based unsaturated polyester resin (SOMGUPR) was prepared using two step polymerization with soybean oil,glycerol,1.2-propanediol,maleric anhydride and phthalic anhydride. FT-IR spectroscopy ,Gel Permeation Chromatography (GPC) and 1H-NMR spectroscopy were employed to study the chemical structure and molecular weight of this unsaturated polyester resin. The results show that 190°C is the optimal temperature to controll the extent of estification reaction.The number-average molecular weight(Mn) decrease with the increasing value of nglycerol:nsoybean oil in SMOGUPR.Also,the side reaction between SOMG and maleric anhydride has not occured as evidenced by 1H-NMR spectroscopy.

Experimental investigations and optimization of processibility of sheet moulding compound

Sheet moulding compound (SMC) is a combination of glass fibers and filled polyester resin. It is processed by a compression moulding process and finds extensive applications in structural, automotive, electrical and electronic industries. The compression moulding process is characterized by the flow behavior of SMC under heat and pressure in the press mould. This paper is focused on the prediction of ideal processibility conditions of SMC. The qualitative aspect of a properly thickened (matured) moulding compound could be seen from its tack-free nature, which was quantitatively calibrated in terms of penetration depth, measured by a specially constructed softness indicator. The weight (wt)% of calcium carbonate (CaCO3) as filler, magnesium oxide (MgO) as thickener, graphite (C) and zinc stearate [Zn (C18H35O2)2] (ZnSt) as lubricants along with the maturation time (Tm) were selected as process variables. Taguchi’s scheme of experimental design was adapted to perform the experiments. It was found that the higher levels of MgO and CaCO3 were favorable for a good penetration depth as well as a reduced maturation time. We have also found that a penetration depth of at least 5 mm was required for achieving good processability conditions of SMC. An optimization study was under taken to find the right blend of additives and fillers, at their minimal weights and in the least possible maturation time, to achieve the desired processability. This study is particularly useful in a production run to make moulded parts from SMC.

Mechanical Properties of UP Resin from Soybean Oil

In this paper, a kind of unsaturated polyester resin (UPR) was prepared by using renewable soybean oil, glycerol, propylene glycol and anhydride as raw materials. In this process, soybean oil firstly reacted with glycerol to yield monoglyceride, then, propylene glycol partly replaced by monoglyceride reacted with anhydride to yield UPR. The effect of weight content of monoglyceride on the mechanical properties of UPR was systematically studied. Results showed that with the increase of weight content of monoglyceride, the curing exothermic peak of UPR was dropped; the curing shrinkage and flexural strength and tensile strength were decreased. But the impact strength and the tensile elongation were increased. When the weight content of monoglyceride was 40%, the impact strength and the tensile elongation could reach 102.074 kJ/m2 and 27.69%, respectively. The prepared UPR had some advantages such as low-cost, flexible and high production efficiency.