Ivan Javni

Thermal stability of polyurethanes based on vegetable oils

A series of polyurethanes from polyols derived from soybean, corn, safflower, sunflower, peanut, olive, canola, and castor oil were prepared, and their thermal stability in air and nitrogen assessed by thermogravimetric analysis, FTIR, and GC/MS. Oil-based polyurethanes generally had better initial thermal stability (below 10% weight loss) in air than the polypropylene oxide-based polyurethane, while the latter was more stable in nitrogen at the initial stage of degradation. If weight loss at a higher conversion is taken as the criterion of stability, then oil polyurethanes have better thermal stability both in air and in nitrogen.

Structure and properties of polyurethane–silica nanocomposites

Nanocomposites with different concentrations of nanofiller were prepared by adding nanosilica filler to the single-phase polyurethane matrix. A control series was prepared with the same concentrations of micron-size silica. The nanosilica filler was amorphous, giving composites with the polyurethane that were transparent at all concentrations. The nanocomposites displayed higher strength and elongation at break but lower density, modulus, and hardness than the corresponding micron-size silica-filled polyurethanes. Although the nanosilica showed a stronger interaction with the matrix, there were no dramatic differences in the dielectric behavior between the two series of composites.

Rigid polyurethane foams based on soybean oil

Both HCFC- and pentane-blown rigid polyurethane foams have been prepared from polyols derived from soybean oil. The effect of formulation variables on foam properties was studied by altering the types and amounts of catalyst, surfactant, water, crosslinker, blowing agent, and isocyanate, respectively. While compressive strength of the soy foams is optimal at 2 pph of surfactant B-8404, it increases with increasing the amount of water, glycerin, and isocyanate. It also increases linearly with foam density. These foams were found to have comparable mechanical and thermoinsulating properties to foams of petrochemical origin. A comparison in the thermal and thermo-oxidative behaviors of soy- and PPO-based foams revealed that the former is more stable toward both thermal degradation and thermal oxidation. The lack of ether linkages in the soy-based rather than in PPO-based polyols is thought to be the origin of improved thermal and thermo-oxidative stabilities of soy-based foams.

Structure and physical properties of segmented polyurethane elastomers containing chemical crosslinks in the hard segment

Two series of segmented polyurethanes, one containing 50% soft segments and the other with 70% soft segments were synthesized. Chemical crosslinks were introduced through the hard segment in a controlled way. Chemical polyurethane networks were characterized by swelling. The effect of the degree of crosslinking on properties was examined. It was found that chemical crosslinks in the hard segment reduce the mobility of the soft phase and destroy the crystallinity of the hard phase, but they improve heat stability of the hard domains.

Effect of Nano-and Micro-Silica Fillers on Polyurethane Foam Properties:

Two series of rigid and flexible polyurethane foams were prepared with two types of silica fillers. The density of the flexible foams was 60 kg/m 3 and that of rigid 30 kg/m3. The fillers were micro-silica of the average particle size of 1.5 mm and nano-silica of the average particle size of 12 nm. The concentration of fillers varied from 0–20%. The micro-silica filler did not show any significant effect on density of either rigid or flexible foams. Nano-silica increased the density of both types of foams only at concentration above 20%. Nano-silica lowered the compression strength of both types of foams at all concentrations while micro-silica exhibited the same effect at concentrations above 10%. The hardness and compression strength in flexible polyurethane foams with nano-silica was increased and the rebound resilience decreased. Reduced density of foams was not changed by nano-silica concentrations up to 20%. It is assumed that the nano-filler, as an additional physical crosslinker, increased modulus of the flexible segment in the polyurethane matrix, resulting in increased hardness and compression strength. The micro-filler in flexible foams lowered hardness and compression strength, but increased rebound resilience. Wide angle X-ray scattering (WAXS) showed amorphous morphology of both flexible and rigid foams filled with nano-silica. WAXS of the micro-silica filled foams showed the presence of randomly oriented crystalline quartz particles and the amorphous structure of the polymeric matrix.

Structure and properties of flexible polyurethane foams with nano- and micro-fillers

The feasibility of using mineral nano- and micro-fillers as replacement of copolymer polyols in flexible foams was examined. Nano-fillers were nano-clays, a natural montmorillonite (Cloisite Na+) and montmorillonite modified with an organic quaternary ammonium salt (Cloisite 10A), and nano-silica dispersed in methylethylketone. Micro-fillers were micronized clay and silica. Flexible foams were prepared from the ethylene oxide caped polyether triol and toluene diisocyanate with water as the chemical blowing agent. All foams had good morphology except those with nano-clay. The open cell content was above 95%, but air flow was very low in all samples. Micro-fillers did not significantly change cell structure and morphology of hard domains. They moderately increased density, hardness, compression strength, and compression set and decreased elongation at break. The other properties were not affected. Cloisite Na+ (non-treated montmorillonite) and nano-silica with a hydrophilic surface increased hardness, compression strength, and rebound resilience of the foams, whereas Nano-clay 10A (surface-treated montmorillonite) decreased the modulus, hardness, and compression strength. Tensile and tear strengths decreased with the addition of nano-clay fillers, but increased with nano-silica.

Plastics and Composites from Soybean Oil

Useful composite matrix materials have been prepared from a series of soybean oils. Their properties are primarily affected by crosslink density. The utility of these resins was demonstrated on two series of laminates prepared from two types of polyols and several types of reinforcements: glass fabric, carbon fiber, polyester, and cotton and jute fabrics. Polyurethane matrix resins are a viable alternative to epoxy and polyester matrix resins and they are already being used commercially in selected farm combine and automotive applications.

Mechanical and dielectric properties of segmented polyurethane elastomers containing chemical crosslinks in the hard segment

Mechanical and dielectric properties of two series of segmented polyurethanes having soft segment concentration of 50 and 70% and a varying degree of crosslinking through the hard segment were studied. The degree of crosslinking in each series was varied by varying the butane diol/trimethylol propane ratio in the chain extender mixture. Tensile strength, elongation at break decrease, but elastic recovery increases monotonically with increasing crosslinking. The plateau modulus in the dynamic mechanical test decreases and then increases with increasing TMP content. Crosslinking causes broadening of the soft segment glass transition as seen by permittivity and loss factor measurements. It also affects high temperature behavior (above the glass transition of the hard segment); it lowers permittivity, loss factor, and ionic conductivity.

Biological Oils as Precursors to Novel Polymeric Materials

This paper reviews a part of the rich fi eld of oleochemicals, their synthesis and applications as precursors for polymers by referring to published data rather than discussing details of different reactions. The hope is to help readers in fi nding leads in the vast research area carried out over a long period of time, to avoid traps and to inspire new ideas for oil-based products and processes.

Polyurethane molded foams with high content of hyperbranched polyols from soybean oil

This paper examines the feasibility of using polyols from vegetable oils as base polyols (i.e. with 50% or more in a blend with petrochemical polyols) for flexible molded polyurethane foams. A series of hyperbranched (HB) polyols were synthesized by transesterification of hydroxy fatty acid methyl esters and different modifiers to control viscosity, hydrophilicity, molecular weight, and functionality. All HB polyols had hydroxyl numbers around 85 mg KOH/g, with the exception of one which was 105 mg KOH/g. When mixed with petrochemical polyols with OH numbers 35 and 28 mg KOH/g, the HB polyols acted primarily as high molecular weight crosslinkers that increased the stiffness of the polymeric network and the load-bearing properties but decreased the tensile strength, elongation, and tear strength. However, most of the foams met the targeted tensile and tear strength values while some of the foam formulations provided satisfactory elongation. The best mechanical properties were obtained from foams with phthalic anhydride-modified HB polyols. It was demonstrated that flexible molded foams with satisfactory properties can be obtained with 50% and 65% of HB soy polyols in a blend with PPO polyols.