Micromechanical deformation processes responsible for toughening mechanisms in ultrafine monospherical inorganic particle-filled polyethylene were investigated in situ by a field-emission gun-environmental scanning electron microscope (FEG-ESEM) with low-voltage techniques. In general, the ultimate properties of polymer composites are largely dependent on the degree of dispersion of filler particles into the matrix. Very often, the agglomeration is one of inevitable occurrences in polymer composites, mixed with ultrafine filler particles. In the present work, the effects of agglomerates, consisting of ultrafine monospherical filler particles, were reexamined in polymer composites on the toughening mechanism. The results show that the dominant micromechanical deformation processes are the multiple debonding processes inside agglomerates, in which the ratio of the matrix strand and the size of agglomerate plays a great role of matrix yielding. In the specimen, where the agglomerates are isolated in the matrix, deformation begins at the equatorial region of agglomerates and propagates through them. However, in the case of closely placed agglomerates, deformation occurs homogeneously within the whole area inside the agglomerates. In both cases, in conjunction with the multiple debonding processes, the major part of energy during the deformation dissipates through the shear-flow processes of the matrix material. In particular, the micromechanical deformation processes observed in this work confirm that the agglomerates do not always have negative effects on the mechanical properties-at least, in the shear deformable semicrystalline polymer matrices. The agglomerates may be effectively used for the improvement of toughness. Furthermore, the FEG-ESEM with low-voltage techniques offers an extremely promising and efficient alternative method to study the morphology as well as in situ micromechanical deformation processes in nonconducting polymer systems.

Some exploratory work was done to look at novel applications, such as filler use and comonomers, for lignin in thermosetting unsaturated polyesters and vinyl esters. The solubility of different lignins (pine kraft, hardwood, ethoxylated, and maleinated) was determined in different resin systems (acrylated epoxidized soybean oil, hydroxylated soybean oil, soy oil monoglyceride, and a commercial vinyl ester) to give an idea of the compatibility of lignin with the resin systems that were used. Further, the use of lignin as a filler was studied. An increase in the glass-transition temperature was noticed, and the modulus at 20°C decreased because of the plasticizing effect of lignin. The lignin was modified to improve its effect on the matrix properties by adding double bond functionality, thus making it possible to incorporate the lignin molecule in the resin through free-radical polymerization. Modified lignin was introduced in several resins by a reaction with maleic anhydride and epoxidized soybean oil and was tested for its effect on the solubility, glass-transition temperature, and modulus. This modification improved the solubility of lignin in styrene-containing resins, as well as the chemical incorporation of lignin in the resin. Moreover, lignin was used to treat the surfaces of natural hemp fibers to utilize lignin's natural affinity for cellulosic fibers. The idea was to cure the surface defects on the natural fibers and increase the bonding strength between the resin and fiber. An optimum improvement was noticed that depended on the amount of lignin covering the fibers.

In this study, castor oil was alcoholyzed with both aliphatic alcohols, such as glycerol and pentaerythritol, and an aromatic alcohol, bisphenol A propoxylate. The resulting alcoholysis products were then malinated and cured in the presence of styrene. Soybean oil pentaerythritol glyceride maleates were also prepared for a direct comparison of the properties of the castor oil and soybean oil based resins. Castor oil was directly malinated as well to see the effect of the alcoholysis step on the properties of the castor oil based resins. The monomers synthesized were characterized by 1 H-NMR spectroscopy, and the styrenated resin liquid properties, such as viscosity and surface energy values, were determined. The conversion of polymerization was determined using time resolved FTIR analysis for the styrenated soybean oil pentaerythritol glyceride maleates, castor oil maleates, and castor oil pentaerythritol glyceride maleates. The effect of monomer identity and styrene content on the conversion of polymerization was explored.

Maleic anhydride modified soybean-and castor-oil-based monomers, prepared via the malination of the alcoholysis products of the oils with various polyols, such as pentaerythritol, glycerol, and bisphenol A propoxylate, were copolymerized with styrene to give hard rigid plastics. These triglyceride-based polymers exhibited a wide range of properties depending on their chemical structure. They exhibited flexural moduli in the 0.8-2.5 GPa range, flexural strength in the 32-112 MPa range, glass transition temperatures (T g ) ranging from 72 to 1528C, and surface hardness values in the 77-90 D range.The polymers prepared from castor oil exhibited significantly improved modulus, strength, and T g values when compared with soybean-oil-based polymers. These novel castor and soybean-oil-based polymers show comparable properties to those of the high-performance unsaturated polyester (UP) resins and show promise as an alternative to replace these petroleum-based materials.

ABSTRACT:In this study, rigid thermoset polymers were prepared from radical copolymerization of the soybean oil monoglyceride maleates with styrene. In the first part of the study, soybean oil monoglycerides (SOMGs) were obtained from the reaction of soybean oil with glycerol at 220 -240°C with an optimization of the reaction to maximize the monoglyceride yield. In the following step, SOMG were reacted with maleic anhydride at temperatures around 100°C to produce the SOMG maleate half esters. Different catalysts and different reaction conditions were examined to increase the maleate half esters' yields. The reactions were followed by IR and 1 H NMR, and the products were characterized by mass spectrometry. In the final step, the radical initiated copolymerization of the SOMG maleates with styrene produced rigid, thermoset polymers. The emulsion copolymerization of the SOMG maleates with styrene was also carried out successfully without the addition of an emulsifier. The obtained polymers were characterized by IR and the crosslinked network structure of the copolymers was examined with the swelling behavior in different solvents. Mechanical properties of the cured resin such as T g , dynamic flexural modulus, and surface hardness were also determined.

Blends of poly (L-lactide) (PLLA) and poly (ε-caprolactone) (PCL) with and without paclitaxel were prepared via solution casting. DSC analysis as well as SEM analysis of the PLLA/PCL blend solution cast films showed that these blends are all phase separated.%PLLA crystallinity was found to increase with increasing PCL content (up till 15 wt.%). The PCL phase is found to homogeneously disperse in the PLLA matrix as spherical domains where the pore diameters of the PCL domains significantly increased with increasing PCL content. The degradation profiles matched with the slower degrading component PCL rather than PLLA and also increasing PCL content of the blends increased the degradation rate relatively. The increased crystallinity of the PLLA phase with increasing PCL contents confirmed that the degradation occurred through PCL phase. Cell proliferation on PLLA/PCL blends showed that all these blends were suitable for the support of cellular growth. Apoptosis assay with the paclitaxel-loaded PLLA/PCL blends showed an increase in cell death throughout 7 days of incubation where the cell death was increased with increasing PCL contents. This was attributed to the faster release of paclitaxel which was at least partially affected by the faster degradation rate at increasing PCL contents. The paclitaxel release was shown to be degradation controlled in the initial stages followed by a faster diffusion-controlled release in the later stages. These polymer blends were found to be verysuitable paclitaxel release agents for which the paclitaxel release times can be altered with the composition of the blend and the film thickness.

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Cardanol is a renewable resource based on cashew nut shell liquid (CNSL), which consists of a phenol ring with a C15 long aliphatic side chain in the meta position with varying degrees of unsaturation. Cardanol glycidyl ether was chemically modified to form side-chain epoxidized cardanol glycidyl ether (SCECGE) with an average epoxy functionality of 2.45 per molecule and was cured with petroleum-based epoxy hardeners, 4-4′-methylenebis(cyclohexanamine) and diethylenetriamine, and a cardanol-based amine hardener. For comparison, cardanol-based diphenol diepoxy resin, NC514 (Cardolite), and a petroleum-based epoxy resin, diglycidyl ether of bisphenol-A (DGEBA) were also evaluated. Chemical and thermomechanical analyses showed that for SCECGE resins, incomplete cure of the secondary epoxides led to reduced cross-link density, reduced thermal stability, and reduced elongation at break when compared with difunctional resins containing only primary epoxides. However, because of functionality greater than two, amine-cured SCECGE produced a Tg very similar to that of NC514 and thus could be useful in formulating epoxy with renewable cardanol content.