Thermogravimetry on wood powder-filled polyurethane composites derived from lignin

Novel polyurethane (PU) composites whose matrix is derived from lignin, molasses polyol and filler from wood powder were successfully prepared. Two kinds of polyol were mixed 0/100 to 100/0 in seven steps, and filler content was varied from 50 to 100 mass % to polyol content. Decomposition behaviour of PU composites was investigated by thermogravimetry. Apparent density and mechanical properties of the above composites were also measured. Surface texture was observed by scanning electron microscopy. Thermal decomposition of PU composites was found to occur in two stages. The first decomposition observed at 570–580 K (DT _d1, peak temperature of derivative curve) is attributed to the matrix of composites. The second stage decomposition depending on filler content, observed in a temperature range from 590 to 630 K (DT _d2), is attributable to filler homogenously associated with PU matrix. Marked differences were not found, when the kinds of lignin and molasses polyol composition were varied. The above PU composites were found to be thermally stabilised by the introduction of filler.     

Biodegradable Polyurethanes from Plant Components

Abstract

Polyurethane (PU) sheets and foams having plant components in their network were prepared by using the following procedure. Polyethylene glycol (PEG) was mixed with one of the following; molasses, lignin, woodmeal, or coffee grounds. The mixture obtained was reacted with diphenylmethane diisocyanate (MDI) at room temperature, and precured PUs were prepared. The precured PUs were heat-pressed and PU sheets were obtained. In order to make PU foam, the above mixture was reacted with MDI after the addition of plasticizer, surfactant (silicone oil), catalyst (di-n-butyltin dilaurate), and droplets of water under vigorous stirring. The glass transition temperature, tensile and compression strengths, and Young's modulus of the PU sheets and foams increased with an increasing amount of plant components. This suggests that saccharide and lignin residues act as hard segments in PUs. It was found that the PUs obtained were biodegradable in soil. The rate of biodegradation of the PUs derived from molasses and coffee grounds was between that of cryptomeria (Cryptomeria japonica) and beech (Fagus sieboldi).     

Thermal and mechanical properties of particulate fillers filled epoxy composites for electronic packaging application

Epoxy composites containing particulate fillers‐fused silica, glass powder, and mineral silica were investigated to be used as substrate materials in electronic packaging application. The content of fillers were varied between 0 and 40 vol%. The effects of the fillers on the thermal properties—thermal stability, thermal expansion and dynamic mechanical properties of the epoxy composites were studied, and it was found that fused silica, glass powder, and mineral silica increase the thermal stability and dynamic thermal mechanical properties and reduce the coefficient of thermal expansion (CTE). The lowest CTE value was observed at a fused silica content of 40 vol% for the epoxy composites, which was traced to the effect of its nature of low intrinsic CTE value of the fillers. The mechanical properties of the epoxy composites were determined in both flexural and single‐edge notch (SEN‐T) fracture toughness properties. Highest flexural strength, stiffness, and toughness values were observed at fillers content of 40 vol% for all the filled epoxy composites. Scanning electron microscopy (SEM) micrograph showed poor filler–matrix interaction in glass powder filled epoxy composites at 40 vol%. Copyright © 2007 John Wiley & Sons, Ltd.     

Preparation and properties of PU/MCMMT nanocomposites

The cetyltrimethyl ammonium bromide (CTAB) was used as a swelling agent to be intercalated into the galleries of the montmorillonite (MMT) platelets to get the organic MMT (CMMT). Then 4,4′‐diphenylmethane diisocyanate (MDI) were grafted on CMMT by the reaction between hydroxyls in organic MMT platelets and MDI to synthesize the MDI modified CMMT (MCMMT). Polyurethane (PU)/MCMMT composites were prepared by situ polymerization. The MCMMT platelets dispersed in a PU matrix in nanometer scale. The dispersion and intercalation degree of the MCMMT platelets decreased with increase in the content of MCMMT. Under the same content of fillers, the tensile strength and tear strength of PU/MCMMT nanocomposites were higher than those of PU/organic MMT nanocomposites. The reinforcing effect of the MCMMT platelets to the PU was better than that of the organic MMT platelets. With increase in the content of MCMMT, the tensile strength and tear strength of the PU/MCMMT nanocomposites were increased, while the extent of the increase slowed down. Compared with those of PU, the thermal stability of PU/MCMMT nanocomposites was increased. Copyright © 2009 John Wiley & Sons, Ltd.     

Aggregation of particulate fillers: factors,determination, properties

The aggregation tendency of 11 different CaCO₃ fillers with widely differing particle sizes was studied in polypropylene (PP) composites. The fillers were characterized by different techniques in powder form and in suspension. Homogenization and sample preparation were carried out by extrusion and injection molding, or in an internal mixer and compression molding, respectively. Thin slices were prepared from the composites and the relative area of aggregates was determined by image analysis. Tensile and fracture properties were studied as a function of filler content. The results proved that the extent of aggregation increases with decreasing particle size and increasing filler content. Surprisingly, extruded and injection molded samples contained more aggregates than those prepared by homogenization in an internal mixer followed by compression molding. Good agreement was found between the powder properties of the fillers and their performance in the composites. Deviations from the general tendency indicate that some factors, which were not accounted for in the study, also influence aggregation and composite properties.     

Effect of walnut shells and silanized walnut shells on the mechanical and thermal properties of rigid polyurethane foams

In the study walnut shells (WS) and silanized walnut shells (S_WS) were used as cellulosic fillers for novel polyurethane (PU) composite foams. The impact of 1, 2 and 5 wt% of WS and S_WS on the foaming parameters, mechanical and thermo-mechanical properties of obtained materials were evaluated. The results have shown that compared to untreated WS filler, the application of S_WS leads to PU foams with more regular structure and improved physico-mechanical behavior of PU materials. For example, compared to controlled WS_0 foam, PU foams enhanced with 1 wt% of the S_WS exhibited better mechanical properties, such as higher compressive strength (~15% of improvement), better impact strength (~6% of improvement), and improved tensile strength (~9% of improvement). The addition of S_WS improved the thermomechanical stability of PU foams. This work provides a better understanding of a relationship between the surface modification of the walnut shell filler and the mechanical, insulating and thermal properties of the PU composites. Due to these positive and beneficial effects, it can be stated that the use of WS and S_WS as natural fillers in PU composite foams can promote a new application path in converting agricultural waste into useful resources for creating a new class of green materials.     

Analysis of the use of an industrial waste as reinforcement in epoxy composites

A study was done to investigate the use of the waste generated at a hydrometallurgical zinc plant as filler in epoxy matrix composites. The waste was processed before its incorporation into the matrix and composites with volume fraction from 10 to 50% were fabricated with six different particle sizes. The results show that the mechanical properties increase with the decrease of the particle size until a threshold value is reached. Below this value the distance between particles became the controlling parameter. The results also show that this waste can be satisfactorily used as filler. Its advantages over commonly used fillers are its low cost and the environmental gain of its convenient disposal.     

Effect of nitrile butadiene rubber/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/YSZ fillers for PMMA denture base on the thermal and mechanical properties

This study is to investigate the effect of nitrile butadiene rubber (NBR as impact modifier) together with Al₂O₃/YSZ (toughening) as filler loading in PMMA denture base on the thermal and mechanical properties. PMMA matrix without fillers was mixed between PMMA powder and 0.5 mass% of BPO, and it is used as the control group. The liquid components consist of 90% of methyl methacrylate (MMA) and 10% as the cross-linking agent of ethylene glycol dimethacrylate. The denture base composites were fabricated by incorporating PMMA powder and BPO and fixed at 7.5 mass% NBR particles and filler loading (1, 3, 5, 7 and 10 mass%) of Al₂O₃/YSZ mixture filler by (1:1 ratio) as the powder components. The ceramic fillers were treated with silane (γ-MPS) and the powder/liquid ratio (P/L) according to dental laboratory practice. The TGA data obtained show that the PMMA composites have better thermal stability compared to unreinforced PMMA, while DSC curves show slightly similar Tg values. DSC results also indicated the presence of unreacted monomer content for both reinforced and unreinforced PMMA composites. The fracture toughness, Vickers hardness and flexural modulus values were statistically increased compared to the unreinforced PMMA matrix (P?<?0.05).     

Environmentally Compatible Hybrid-Type Polyurethane Foams Containing Saccharide and Lignin Components

Semi-rigid polyurethane (PU) foams were prepared using lignin-molasses- poly(ethylene glycol) polyols. Two kinds of lignin, kraft lignin (KL) and sodium lignosulfonate (LS), were used. Both lignin and molasses polyols were mixed with various ratios and were reacted with poly(phenylene methylene) polyisocyanate (MDI) in the presence of silicone surfactant and di-n-butyltin dilaurate. A small amount of water was used as a foaming agent. The apparent density of PU foams increased with increasing lignin content. The compression strength and elastic modulus linearly increase with increasing apparent density, suggesting that mechanical properties are controllable by changing reaction conditions. The PU foams were amorphous and glass transition was detected by differential scanning calorimetry. The glass transition temperature (T_g ) maintained an almost constant value, regardless of the mixing ratio. This indicates that both the phenolic group of lignin and the glucopyranose ring of molasses act as rigid components in PU crosslinking network structures, and both groups contribute to the main chain motion to the same extent. By thermogravimetry (TG), it was confirmed that PU foams are thermally stable up to around 300 °C. By differential scanning calorimetry, T_g was observed at temperatures from 80 to 120 °C.     

Biodegradable polyhydroxybutyrate as a polyol for elastomeric polyurethanes

In the proposed work, new elastomeric bio-polyol based polyurethanes (bio-PUs) with specific mechanical properties were prepared by a one-shot process without the presence of a solvent. Commercial non-degradable polyether polyol derived from petrochemical feed stock was partly (in the amount of 1 mass %, 5 mass %, and 10 mass %) substituted by the biodegradable polyhydroxybutyrate (PHB). Morphology of elastomeric PU composites was evaluated by scanning electron microscopy and mechanical properties of the prepared samples were obtained by both tensile measurements and prediction via the Mooney-Rivlin equation. Electron microscopy proved that the prepared materials have the character of a particle filled composite material, where PHB particles are regular with their size of about 1?C2 ??m in diameter. Tensile measurements demonstrated that the Young??s modulus, tensile stress at break, and tensile strain at break of each sample increase with the increase of the volume fraction of the filler. From the measured stress-strain data, the first and the second term of the Mooney-Rivlin equation were calculated. The obtained constants were applied to recalculate the stress-strain curves. It was found that the Mooney-Rivlin equation corresponds well with the stress-strain behavior of the prepared specimens.     

Nutmeg filler as a natural compound for the production of polyurethane composite foams with antibacterial and anti-aging properties

Polyurethane (PU) composite foams were successfully reinforced with different concentrations (1 wt%, 2 wt%, 5 wt%) of nutmeg filler. The effect of nutmeg filler concentration on mechanical, thermal, antimicrobial and anti-aging properties of PU composite foams was investigated. PU foams were examined by rheological behavior, processing parameters, cellular structure (Scanning Electron Microscopy analysis), mechanical properties (compression test, impact test, three-point bending test, impact strength), thermal properties (Thermogravimetric Analysis), viscoelastic behavior (Dynamic Mechanical Analysis) as well as selected application properties (thermal conductivity, flammability, apparent density, dimensional stability, surface hydrophobicity, water absorption, color characteristic). In order to Disc Diffusion Method, all PU composites were tested against selected bacteria (Escherichia coli and Staphylococcus aureus). Based on the results, it can be concluded that the addition of 1 wt% of nutmeg filler leads to PU composite foams with improved compression strength (e.g. improvement by ~19%), higher flexural strength (e.g. increase of ~11%), improved impact strength (e.g. increase of ~32%) and comparable thermal conductivity (0.023–0.034 W m⁻¹ K⁻¹). Moreover, the incorporation of nutmeg filler has a positive effect on the fire resistance of PU materials. For example, the results from the cone calorimeter test showed that the incorporation of 5 wt% of nutmeg filler significantly reduced the peak of heat release rate (pHRR) by ca. 60% compared with that of unmodified PU foam. It has been also proved that nutmeg filler may act as a natural anti-aging compound of PU foams. The incorporation of nutmeg filler in each amount successfully improved the stabilization of PU composite foams. Based on the antibacterial results, it has been shown that the addition of nutmeg filler significantly improved the antibacterial properties of PU composite foams against both Gram-positive and Gram-negative bacteria.     

Synthesis and thermal studies of flexible polyurethane nanocomposite foams obtained using nanoclay modified with flame retardant compound

This work presents thermal studies of nanocomposites based on the flexible polyurethane (PU) matrix and filled using montmorillonite organically modified with organophosphorus flame retardant compound. Flexible PU nanocomposite foams were prepared in the reaction carried out between reactive alcoholic hydroxyl and isocyanate groups with the ratio of NCO to OH groups equal to 1.05. The amount of an organoclay ranging from 3 to 9 vol% was added to the polyol component of the resin before mixing with isocyanate. The apparent density of PU foams was ranging from 0.066 to 0.077 g cm^?1. Thermal properties of the flexible PU nanocomposite foams were investigated by thermogravimetry and dynamical mechanical analysis. Glass transition temperatures (T _g) were defined as maximum peak on tanδ curve. Thermal decomposition was observed at 310–320 °C (calculated from the onset of TG curve). Tensile strength of the PU foams was determined using mechanical test. The microstructure of the nanoparticles and the composites was investigated by X-ray diffraction. Finally, it was confirmed that the thermal and mechanical properties of flexible PU nanocomposite depend on the amount of nanoclay.     

Glass transition and thermal degradation of rigid polyurethane foams derived from castor oil–molasses polyols

Rigid polyurethane (PU) foams having saccharide and castor oil structures in the molecular chain were prepared by reaction between reactive alcoholic hydroxyl group and isocyanate. The apparent density of PU foams was in a range from 0.05 to 0.15 g cm^?3. Thermal properties of the above polyurethane foams were studied by differential scanning calorimetry, thermogravimetry and thermal conductivity measurement. Glass transitions were observed in two steps. The low-temperature side glass transition was observed at around 220 K, regardless of castor oil content. This transition is attributed to the molecular motion of alkyl chain groups of castor oil. The high-temperature side glass transition observed in the temperature range from 350 to 390 K depends on the amount of molasses polyol content. The high-temperature side glass transition is attributed to the molecular motion of saccharides, such as sucrose, glucose, fructose as well as isocyanate phenyl rings, which act as rigid components. Thermal decomposition was observed in two steps at 570 and 620–670 K. Thermal conductivity was observed at around 0.032 J sec^?1 m^?1 K^?1. Compression strength and modulus of PU foams were obtained by mechanical test. It was confirmed that the thermal and mechanical properties of PU foams could be controlled by changing the mixing ratio of castor oil and molasses for suitable practical applications.     

聚吡咯/多壁碳纳米管及其聚氨酯导电复合材料的制备和性能

以羧基化多壁碳纳米管(MWCNTs)做模版剂,采用化学氧化法将吡咯(Py)在羧基化MWCNTs表面聚合制备PPy/MWCNTs导电材料,将其添加到溶剂型聚氨酯(PU)溶液中制备了PPy/MWCNTs/PU导电复合材料,研究了Py用量对PPy/MWCNTs及其PU复合材料性能的影响.研究表明,随Py用量的增加,PPy/MWCNTs的长度不变,管径增大,sp~2和sp~3杂化C含量先提高后减少,N的掺杂梯度降低,PPy/MWCNTs的导电率高于羧基化MWCNTs和PPy.当Py用量为羧基化MWCNTs的20%时,其导电率最大.PPy/MWCNTs中N元素的掺杂程度及其管径变化是引起PPy/MWCNTs/PU复合材料的性能不同的主要原因.增加Py用量,MWCNTs中亲水的羧基因对PPy掺杂而消耗,相同导电材料用量时纳米导电粒子数目相对减少,PPy/MWCNTs/PU复合材料的耐水性能提高,定向应力、储能模量和玻璃化温度降低,导电率先增加后减小.当Py用量为羧基化MWCNTs的15%时,导电率最大.     

Use of calcium carbonate – fumed silica mixtures as filler in polyurethane adhesives

Natural ultramicronized calcium carbonate and mixtures of fumed silica‐natural ultramicronized calcium carbonate are proposed as fillers of solvent based polyurethane (PU) adhesives. PU adhesive containing only calcium carbonate shows similar rheological, thermal, mechanical, surface and adhesion properties than the PU adhesive without filler. Addition of 90 wt% fumed silica +10 wt% calcium carbonate mixture to PU adhesive produced a similar performance than the PU adhesive containing only famed silica. The increase in the amount of natural calcium carbonate in respect to fumed silica in the filler mixture produced detrimental effect on the rheological and mechanical properties of the PU adhesives (in respect to those provided by the PU adhesive only containing fumed silica), although the surface and adhesion properties were not noticeably modified.     

五种植物纤维粉填充不饱和聚酯树脂复合材料的性能对比

以芝麻秸秆粉、水稻秸秆粉、玉米芯秆粉、菠萝叶粉、甘蔗渣粉五种不同植物纤维粉为填充体、不饱和聚酯树脂(UPR)为基体制作植物纤维粉/UPR复合材料,对比研究了秸秆种类对复合材料密度、力学性能及吸水性能的影响。结果表明,植物纤维粉粒径为100目、添加量为UPR用量的10%时,芝麻秸秆粉/UPR复合材料的综合力学性能最好,拉伸强度、弯曲强度和冲击强度分别为41.320 MPa、67.467 MPa和2.815 KJ/m^2,且每一浸泡阶段吸水率均最低。     

Mechanical and thermal investigation of thermoplastic nanocomposite films fabricated using micro- and nano-sized fillers from recycled cotton T-shirts

The thermal and mechanical performance of composites with nano-sized cotton fillers embedded in low-density polyethylene (LDPE) is investigated. Microfibrillated cotton was prepared by microgrinding mechanical treatment of pulverized cotton (pCot) derived from waste T-shirts, resulting in nano-sized fibrils of the cellulose that retain high crystallinity. Film composites of LDPE with pCot before and after microgrinding were fabricated through melt extrusion and the effect of filler size on mechanical, thermal and morphological properties of the composite was investigated. Compounding microfibrillated cotton with LDPE resulted in well-dispersed nanocomposites with no discoloration after 10 min of melt extrusion at 170 °C. At concentrations up to 10 % by weight, the composites showed increased modulus, increased tensile strength and a slight decrease in elongation to break. Further improvement in the dispersion and mechanical properties of the cotton-based fillers was realized by the use of LDPE powder instead of polymer pellets fed to the extruder. This research demonstrates the processing and applicability of the use of recycled cotton-based nano-sized fillers in melt-processing.     

Dispersion evaluation of microcrystalline cellulose/cellulose nanofibril-filled polypropylene composites using thermogravimetric analysis

Microcrystalline cellulose-filled polypropylene (PP) composites and cellulose nanofiber-filled composites were prepared by melt blending. The compounded material was used to evaluate dispersion of cellulose fillers in the polypropylene matrix. Thermogravimetric analysis (TG) and mechanical testing were conducted on composites blended multiple times and the results were compared with single batch melt blended composites. The residual mass, tensile strength, and coefficient of variance values were used to evaluate dispersion of the microcrystalline cellulose fillers in the PP matrix. The potential of using TG to evaluate cellulose nanofiber-filled thermoplastic polymers was also investigated and it was found that the value and variability of residual mass after TG measurements can be a criterion for describing filler dispersion. A probabilistic approach is presented to evaluate the residual mass and tensile strength distribution, and the correlation between those two properties. Both the multiple melt blending and single batch composites manufactured with increased blending times showed improved filler dispersion in terms of variation and reliability of mechanical properties. The relationship between cellulose nanofiber loading and residual mass was in good agreement with the rule of mixtures. In this article, the authors propose to use a novel method for dispersion evaluation of natural fillers in a polymer matrix using TG residual mass analysis. This method can be used along with other techniques such as scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD) for filler dispersion evaluation in thermoplastic composites.     

Novel filled polymer composites prepared from in situ polymerization via a colloidal approach: II. Blends of kaolin/Nylon-6 in situ composites with conventional Nylon-6 and -66

A novel in situ composite comprised of kaolin clay fillers and polyamide 6 (Nylon-6) was synthesized via a colloidal approach by suspending kaolin particles in aqueous caprolactam and then polymerizing the caprolactam under elevated temperature and pressure. This in situ polymerization technique enables the deposition of nylon molecules directly onto the filler surface. It offers a much larger contact surface area for the nylon molecules to interact with the filler particles and enhances filler/matrix interaction through polymer miscibility. The kaolin particles were shown to be uniformly dispersed in Nylon-6 matrix without appreciable agglomeration. In the highly clay-loaded composites such as the 50/50 kaolin/Nylon-6 in situ composite, the deposited nylon molecules probably form a coated layer on the filler particles. This kind of nylon coated fillers may be applied as a reinforcing entity to commercial Nylon-6 or −;66 by improving particle dispersion and melt processability. The 50/50 kaolin/Nylon-6 in situ composites have been used as a masterbatch for blending with commercial Nylon-6 and Nylon-66 to take advantage of their good properties and to reduce cost. Rheology and mechanical properties of the masterbatch/nylon composites have been investigated in comparison with those of the conventional melt-mixed composites. The improvement of rheological and mechanical properties of the in situ composites has been discussed in relation to the composite structure. © 1996 John Wiley & Sons, Inc.     

Comparative study of the mechanical and wear performance of short carbon fibers and mineral particles (Wollastonite,CaSiO3) filled epoxy composites

To improve the mechanical and tribological performance, two kinds of wollastonite fillers (fine or coarse) and short carbon fibers (5–15 vol %) were, respectively, incorporated into an epoxy resin. Fine wollastonite fillers remarkably enhanced the flexural modulus, strength, and toughness of the resin at some filler contents (i.e., 10 vol %) simultaneously, while coarse wollastonite fillers and short carbon fibers impaired most of mechanical properties except the modulus. The small particle size, low aspect ratio as well as the good adhesion to the epoxy matrix of the fine wollastonite particles are believed to be responsible for the improved strength and toughness. Tribological tests were performed under sliding and low amplitude oscillating wear conditions. All fillers enhanced the wear resistance and reduced the sliding coefficient of friction but to a different extent. Under sliding wear conditions, fine wollastonite particle‐filled epoxy displayed the highest wear resistance because of the formation of an effective transfer film and the low abrasiveness of the fillers. Under low amplitude oscillating wear conditions, both wollastonite fillers showed much higher wear resistance than short carbon fibers regardless of the filler content. The better adhesion between the wollastonite fillers and the epoxy matrix is responsible for the higher wear resistance under oscillating conditions. The wear tracks were inspected by microscopy to analyze the corresponding wear mechanisms. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 854–863, 2006