Characterization of polymer modified bituminous roofing membranes using thermal analysis

The thermal properties influencing seam performance of polymer modified bituminous roofing membranes are investigated using thermogravimetry and differential scanning calorimetry. Ten different commercial roofing materials are included: three atactic polypropylene (APP) modified bitumens and seven styrene-butadiene-styrene copolymer (SBS) modified bitumens. The results show that the difference in specific heat among different SBS or APP products was small. However, the specific heat of APP products was approximately 0.2 J g⁻¹ K⁻¹ higher than that of SBS products. It may indicate that for APP products a higher amount of energy is required for welding. Overheating of the membranes above 200°C during heat welding may cause decomposition in the polymer modified bitumen, since the degradation of pyrolysable organics begins at ∼200°C.

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Resume Ce travail a été consacré à l'étude des caractéristiques thermiques qui exercent une influence sur les performances des joints soudés des membranes d'étanchéité de bitume polymère. Dix membranes d'étanchéité du commerce, trois à base de bitume modifié par du polypropylène atactique (APP) et sept à base de bitume modifié par un copolymère styrène-butadiène-styrène (SBS) ont été étudiées à l'aide de la thermogravimétrie et de l'analyse calorimétrique différentielle. Les résultats de cette étude ont montré que les différences de chaleur spécifique entre les différents produits SBS out APP sont faibles. Toutefois, la chaleur spécifique des produits APP était plus élevée d'environ 0.2 J g⁻¹ K⁻¹ que celle des produits SBS. Ceci pourrait indiquer que les produits APP nécessitent une quantité d'énergie plus élevée pour leur soudage. La surchauffe des membranes au-dessus de 200°C durant le soudage peut provoquer une décomposition du bitume polymère, du fait que la dégradation de leurs composés organiques pyrolysables débute à environ 200°C.

     

Characterization of polymer modified bituminous roofing membranes using chromatography

This is part of a broad study to characterize polymer modified bituminous roofing materials studied for seam performance. Ten different commercial roofing materials, three of atactic polypropylene (APP) modified bitumen and seven of styrene-butadine-styrene copolymer (SBS) modified bitumen, were studied using high performance liquid chromatography for the analysis of the original bitumen binders and high performance gel permeation chromatography for the qualitative and quantitative analysis of the polymers. The results show that the oxidized bitumen has the highest asphaltene content at about 30%. The asphaltene content of the original bitumen in APP products is higher than in SBS products. The difference in the amount of polymer in each product is not great, and no correlation with seam strength is observed. The degradation of the polymer, which refers to the decrease in molecular weight or the increase in molecular weight distribution can be identified.

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Resume Le but de cette étude était de caractériser les lés d'étanchéité de bitume polymère sur lesquels on avait examiné les performances des joints soudés. Dix lés d'étanchéitè du commerce, dont trois à base de bitume modifié par du polypropylène atactique (APP) et sept à base de bitumen modifié par un copolymère styrène-butadiène-styrène (SBS) one été étudiés à l'aide de la chromatographie haute performance en phase liquide pour l'analyse des liants bitumineux d'origine, et à l'aide de la chromatographie haute performance par perméation sur gel pour l'analyse qualitative et quantitative des polymères. Les résultats montrent que le bitume oxydé présente la teneur en asphaltène la plus élevée avec environ 30%. La teneur en asphaltène du bitume original des produits APP est plus élevée que celles des produits SBS. Les différences de teneur en polymère entre chaque produit étaient faibles et aucune corrélation entre ces différences et la résistance des joints n'a été observée. La dégradation du polymère, qui s'exprime par une diminution de poids moléculaire ou par une augmentation de la distribution du poids moléculaire, peut être identifiée.

     

Study on seam performance of polymer-modified bituminous roofing membranes using T-peel test and microscopy

The aim of the study was to understand how the T-peel strength of heat-welded seams in polymer-modified bituminous roofing membranes depends on the welding method and on the material properties. Seam samples of ten different commercial products, three of Atactic Polypropylene (APP)-modified bitumen and seven of Styrene-Butadiene-Styrene copolymer (SBS)-modified bitumen, were prepared by different welding methods with different heating media, i.e. hot air or gas torch, welding speed and weight of pressure roller joining seams. The welding conditions were precisely controlled during the preparation, and the temperature in the seam sample was measured. T-peel tests were carried out at 23°C and at ?10°C on specimens cut out from each heat-welded sample to measure the T-peel strengths. The fracture propagation during T-peel testing was studied visually. Some seam specimens were also studied using microscopy. In order to identify the material properties and differences in the material compositions influencing the seam strengths, each product was characterised by different chemical and thermal methods, which were described in recently published reports [1,2]. It was concluded that the choice of welding speed and pressure weight for the optimum design of welding machine should make reference to the thermal properties, such as specific heat, and to the rheological properties, such as viscosity.     

Effect of resin infiltration on the thermal and mechanical properties of nano-sized silica-based thermal insulation

Several kinds of nano-sized silica-based thermal insulation were prepared by dry processing of mixtures consisting of fumed silica, ceramic fiber, and a SiC opacifier. Infiltration of phenolic resin solution into the insulation, followed by hot-pressing, was attempted to improve the mechanical strength of the insulation. More than 22% resin content was necessary to increase the strength of the insulation by a factor of two or more. The structural integrity of the resin-infiltrated samples could be maintained, even after resin burn-out, presumably due to reinforcement from ceramic fibers. For all temperature ranges and similar sample bulk density values, the thermal conductivities of the samples after resin burn-out were consistently higher than those of the samples obtained from the dry process. Mercury intrusion curves indicated that the median size of the nanopores formed by primary silica aggregates in the samples after resin burn-out is consistently larger than that of the sample without resin infiltration.     

Effect of mixing on thermal and mechanical properties of aerogel-PVB composites

Silica aerogels were synthesized via solvent exchange/surface modification of wet gels from waterglass using IPA/TMCS/n-Hexane solution. The densities, porosities, and specific surface areas of the aerogel were in the range of 0.128–0.153 g/cm³, 93–95%, and 598–795 m²/g, respectively. Aerogel-PVB composites were manufactured by hot pressing. Aerogels were crushed and mixed with PVB. Three mixing methods were performed. The aerogel-PVB composites had densities of 0.19–1.09 g/cm³, and thermal conductivities of 0.03–0.12 W/(m · K). Density and thermal conductivity can be controlled by aerogel volume fraction and the mixing method. The modulus of rupture of aerogel-PVB composites was in the range of 0.15–46.5 MPa.     

Analysis of the influence of binder properties on the mechanical response of bituminous mixtures

Asphalt mixtures are composed by a mass of aggregates (more than 90% of their total weight), which are bonded by a bituminous binder. Despite the fact that the binder is not the main component of these materials (around 5% of their total weight), it exerts a high influence on their mechanical response. In this sense, the service life of asphalt pavements will directly depend on the type of binder used, and thus an adequate choice is crucial to construct more durable roads. Because of this fact, it is necessary to know the characteristics of the bitumen in order to reduce the impact of different distresses that appear on roads. For this purpose, this paper studies the influence of the binder properties in the appearance of the main distresses that affect asphalt pavements around the world (stripping, fatigue cracking and plastic deformations). Five bitumens with different properties have been analysed during this research using diverse binder (UCL, multiple stress creep and recovery test and dynamic shear rheometer time sweep) and mixture (water sensitivity, wheel tracking and UGR-FACT) tests. The results obtained show that the properties of the binder influence the long-term performance of bituminous mixtures. In this sense, it can be said that flexible binders which are able to recover plastic deformations could extend the service life of the pavements.     

Effect vapor grown carbon nanofiber on thermal and mechanical properties of epoxy

In the present investigation, dynamic mechanical analysis (DMA), thermo gravimetric analysis (TGA), tensile tests, fatigue tests and the single edge notch tensile (SENT) tests were performed on unfilled, 1, 2 and 3 wt.% vapor grown carbon nanofiber (CNF) filled SC-15 epoxy to identify the loading effect on thermal and mechanical properties of the composites. DMA studies revealed that filling the 3% carbon nanofiber into epoxy can produce 65% enhancement in storage modulus at room temperature and 6 °C increase in T _g. However, TGA results show that thermal stability of composite is insensitive to the CNF content. Tensile tests were carried out at the strain rate range from 0.02 min⁻¹ to 2 min⁻¹. Results show that CNF/epoxy are strain rate sensitive materials, the modulus and tensile strength increased with increasing of strain rate. Experimental results also indicate that modulus of the nanophased epoxy increases continuously with increasing CNF content. But the 2% CNF infusion system exhibit maximum enhancement in tensile strength, fatigue performance and fracture toughness as compared with other system.     

含碳纳米管的PEI纤维膜对环氧树脂力学性能的影响

采用高压静电纺丝法制备了含多壁碳纳米管(MWCNTs)的聚醚酰亚胺(PEI)纳米纤维取向薄膜,用SEM和TEM观察其微观形貌.将PEI纳米纤维薄膜铺放于环氧树脂中,通过实验测试其冲击和拉伸性能.结果表明,含MWCNTs的PEI纳米纤维膜对环氧树脂具有良好的增韧效果.Ⅰ型层间断裂韧性(GIC)测试表明,用含质量分数3％活性碳纳米管(a-MWCNTs)的PEI纤维膜对T700碳纤维/环氧树脂复合材料进行层间增韧能够明显改善其层间断裂韧性.     

含碳纳米管的PEI纤维膜对环氧树脂力学性能的影响

采用高压静电纺丝法制备了含多壁碳纳米管(MWCNTs)的聚醚酰亚胺(PEI)纳米纤维取向薄膜, 用SEM和TEM观察其微观形貌。将PEI纳米纤维薄膜铺放于环氧树脂中, 通过实验测试其冲击和拉伸性能。结果表明, 含MWCNTs的PEI纳米纤维膜对环氧树脂具有良好的增韧效果。Ⅰ型层间断裂韧性(G_IC)测试表明, 用含质量分数3%活性碳纳米管(a-MWCNTs)的PEI纤维膜对T700碳纤维/环氧树脂复合材料进行层间增韧能够明显改善其层间断裂韧性。     

Effect of DMPA-clay-POSS content on thermal and mechanical properties of nanostructured ionomeric polyurethanes

Two series of ionomeric waterborne polyurethane (WBPU)/POSS-clay hybrid nanocomposites were synthesized using various amounts of a diol-functionalized polyhedral oligomeric silsesquioxane (POSS)/clay (Cloisite 15A) component with two different 2,2-dimethylol propionic acid (DMPA) contents (13.58 mole% and 23.89 mole%). The Tg of WBPU/POSS-clay hybrid nanocomposite was shifted towards higher temperatures in comparison to virgin WBPU and WBPU/clay nanocomposites. The thermal stability of the investigated WBPU/POSS-clay hybrid nanocomposites also dramatically improved compared to pristine WBPU and WBPU/clay nanocomposites. The higher Young's modulus of the WBPU/POSS-clay hybrid nanocomposites as a function of optimal POSS content suggests that the organic-inorganic hybrid networks are significantly reinforced by the inclusion of POSS.     

Effect of amyl acetate sorption on mechanical and thermal properties of polypropylene packaging

Sorption kinetics of amyl acetate in polypropylene is studied at 23, 40 and 55°C. Diffusion (D) and partition (Kp) coefficients were determined by fitting the sorption curves with a theoretical curve calculated from Fick's diffusion equation. The role of temperature and concentration of amyl acetate was investigated. The results show that D is not affected and Kp decreases with increasing concentration of amyl acetate in the solution. The sorption rate or total amount absorbed increased considerably with temperature. Concentration profiles were calculated by using a numerical algorithm based on a finite element method. The effect of amyl acetate concentration on the mechanical and thermal properties of the polymer was investigated. Copyright © 2007 John Wiley & Sons, Ltd.     

Effect of isotropic interlayers on the mechanical and thermal properties of carbon/carbon composites

Multilayer which consists of isotropic (ISO) interlayer and rough laminar (RL) and single RL structure carbon/carbon (C/C) composites have been prepared by isothermal chemical vapor infiltration at 5 and 1 kPa. Mechanical and thermal properties of both composites have also been studied. Experimental results indicate that ISO interlayer between fiber and matrix plays an important role on fracture behavior and strength of the composites. Comparing with single RL structure composites, the strength decrease of composites with ISO interlayers is about 28-40%. ISO interlayer is the main source of fracture due to its low density and micropores between crystallites. The low thermal conductivity of ISO interlayers also results in the thermal property degradation of obtained C/C composites. By reducing infiltration pressure, the ISO interlayers are substituted by compact RL matrix which improves the general properties of C/C composites.     

Effect of rapeseed oil on the rheological,mechanical and thermal properties of plastic lubricants

A strong difference in the physico-chemical properties of the plastic lubricants studied was found in this study through pressure drop, thermal analysis, vibration damping, texture hardness and rheological measurements. Oxidation aging of the lubricant sample containing rapeseed oil additive was proposed. Its higher thermal sensitivity was simultaneously confirmed by frequency dependent complex shear modulus of elasticity measurements as well as by rheological testing. Rapeseed oil modified lubricant showed a higher decrease in both storage and moduli losses due to a temperature increase from 16 to 26 ° C compared to the rapeseed oil free sample. Simultaneously, the flow curves were shifted to the higher shear stresses (for plastic lubricant without rapeseed oil additive) typical for rheopectic fluids. For the rapeseed oil modified lubricant, the flow curves were shifted to the lower shear stresses, indicating its thixotropic fluid behaviour. The synthetic lubricant without rapeseed oil additive exhibited higher dissipative rheological behaviour as reflected by decreasing first resonance frequency peak position compared to the rapeseed oil modified lubricant as obtained from vibration damping measurements. It was found that the synthetic lubricant exhibited better vibration damping properties and mechanical energy dissipation into heat due to its higher viscous friction than the rapeseed oil modified lubricant under experimental conditions.

     

Effect of compatibilization on mechanical and thermal properties of polypropylene–soy flour composites

A new biobased composite was developed by adding soy flour (SF) to polypropylene (PP). This composite shows an enhanced tensile strength and modulus but decrease in elongation at break. The compatibilizer (coupling agent) appears to have a synergistic effect on tensile strength. The presence of the compatibilizer improves the dispersion of SF in the PP matrix. The addition of glycerol plasticizer to the composite improves the processability resulting in improved performance, as compared to composites without glycerol plasticizer. The optimal compatibilizer content appears to be 6%.     

Effect of silane coupling agents on mechanical and thermal properties of polyester resin concrete

Polyester resin-quartzite aggregate composites have been investigated for the effect of two silane coupling agents (γ-aminopropyl triethoxy silane andγ-methacryloxy propyl trimethoxy silane) on the mechanical and thermal properties. The integral blend additive method of application of the coupling agent was used in the preparation of the samples. Variation of the thermal stability and the compressive strength with the nature and the content of the silane coupling agent were quite consistent. The properties showed maxima around a certain value of the coupling agent content, which is suggested as the optimum value. Results are also presented on the samples containing an additional filler, namely, the CaCO₃.     

Effect of SiC coated MWCNTs on the thermal and mechanical properties of PEI/LCP blend

Multiwalled carbon nanotubes (MWCNTs) were modified by polycarbosilane derived β-SiC particle to improve its dispersion in the polymer matrix. Formation of β-SiC particle onto MWCNTs was conformed by XRD study. Polyetherimide (PEI)/liquid crystalline polymer (LCP) blends with unmodified and modified MWCNTs were prepared by melt blending and the dispersion of the nanofillers in the polymer blend was studied by high resolution transmission electron microscopy, which showed improved dispersion of modified MWCNTs compared to pure MWCNTs. Viscosity of ternary blend with modified MWCNTs was found to be lower than the ternary blend with pure MWCNTs. Incorporation of modified MWCNTs improved the fibrillation of LCP in ternary blend as compared to pure MWCNTs. Thermal analysis revealed the higher thermal stability of the modified MWCNTs added nanocomposites compared to unmodified MWCNTs. Mechanical properties of nanocomposites with SiC coated MWCNTs were found to be higher than that of pure MWCNTs added nanocomposites.     

Effect of NiCrAlY platelets inclusion on the mechanical and thermal shock properties of glass matrix composites

NiCrAlY platelets modified glass matrix composites were prepared. Their microstructures were characterized, their Young's modulus, fracture strength in bending, Vickers hardness, and indentation toughness were measured, and their thermal shock resistance was studied using quenching-strength and indentation-quench methods. With increasing NiCrAlY content, evident enhancements of the Young's modulus and indentation toughness were obtained. The NiCrAlY alloy inclusion could exert significant influences on the retained bending strength of the samples after quench tests, from 9.6 MPa for NiCrAlY-free glass to 32.0 MPa for 30 wt.% NiCrAlY-containing composites. The indentation-quench tests showed that NiCrAlY alloy inclusion elevated the critical quenching temperatures for propagation of pre-crack, from 150 °C for NiCrAlY-free glass to 225 °C for 30 wt.% NiCrAlY-containing composites. Inclusion debonding and intersection, crack deflection and bridging were observed, and are likely the micromechanisms accounted for the improvement of fracture resistance.     

Effect of high thermal expansion glass infiltration on mechanical properties of alumina-zirconia composite

This work studies the effect on the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabilized) composite by infiltrating glass of a higher thermal expansion (soda lime glass) on the surface at high temperature. The glass improved the strength of composite at room temperature as well as at high temperature. This could be attributed to the drastic drop in the coefficient of thermal expansion due to the compositional change in the soda lime glass during infiltration. There was a significant improvement in the Weibull modulus after glass infiltration. Glass infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the penetrated glass.