Interaction of Chloroprene and Nitrile-Butadiene Rubber with Lubricating Greases and Base Oils

The present communication addresses compatibility of two synthetic rubber types,chloroprene and nitrile-butadiene ones,with a number of base oils of petroleum origin and lubricating greases produced thereof.Four base oils,including three naphthenic products with varying degrees of refining and one paraffinic product,were compared with each other in terms of their effect on the rubbers.Degenerative changes occurring in the rubbers on contact with the oils and greases were studied using accelerated ageing tests.Alterations in rubber parameters,such as hardness,weight and glass transition temperature,caused by interaction with oil were monitored.The main physicochemical mechanisms standing behind the changes observed in the rubber properties were found to be(i) migration of plasticizer from rubber into the oil phase,(ii) absorption of oil by rubber,and(iii) oxidation of rubber.An increase in glass transition temperature(Tg) of rubber aged in a base oil or grease was considered as an indirect indication that the plasticizer had migrated out of rubber;the plasticizer accumulation in the oil phase being directly confirmed by gas chromatography.In order to suppress the plasticizer migration,oil additivation with dioctyl adipate(DOA),a common plasticizer used in rubber formulations,was attempted.However,the DOA-additivated oils,while reducing plasticizer migration,were found to cause more swelling than the original oils in the case of chloroprene rubber.As an alternative,replacement of DOA by an alkylated aryl phosphate in nitrile-butadiene rubber formulations was considered,but it did not solve the problem either.The results of this study suggest conclusively that the type of rubber,the plasticizer,and the base oil are all the crucial parameters that should be considered when matching rubber with oil in real-life applications.Interaction of rubber with base oils and with greases produced thereof is largely controlled by(i) solvency of the base oils and(ii) polarity and cross-linking density of the rubber matrix.Higher temperatures accelerate ageing in all cases.

Emulsion cold mix asphalt in the UK: A decade of site and laboratory experience

Cold mix asphalt manufactured using bitumen emulsion, by its very nature, has struggled to gain market penetration in the UK due to lack of design guidance and specifications and the need to comply with prevailing hot mix asphalt specification requirements. Despite this, a number of contractors have successfully utilized emulsion cold mix asphalt materials containing recycled asphalt planings on various categories of road. Whilst the majority of schemes in the UK have been on lower category traffic roads, in this paper we discuss the use of one material which has been used on a strategic highway(trunk road) in2008 which saved 43 t of CO2 during construction and is still performing well in situ to this day. Site construction details along with an analysis of traffic loading are presented. Laboratory simulations of in-situ curing of material supplied to site demonstrated an indirect tensile stiffness modulus at 10℃ of 5 GPa was achieved within 6 months. Binder recovered from site cores was found to be in line with comparable hot mix materials, whilst wheel tracking of site cores demonstrated excellent deformation resistance which has been borne out by site performance over the last decade. The continued development of standards enabling engineers to design and specify cold mix asphalt in the UK is also reviewed.

Chemical,morphological and rheological characterization of bitumen partially replaced with wood bio-oil:Towards more sustainable materials in road pavements

Nowadays,sustainability and circular economy are two principles to be pursued in all fields.In road pavement engineering,they can be put into practice through the partial substitution of bitumen with industrial residues and by-products deriving from renewable materials.Within this framework,this paper presents an extensive investigation of the chemical,morphological and rheological properties of bio-binders obtained by mixing a conventional 50/70 bitumen with different percentages by weight(0,5%,10%and 15%)of a renewable bio-oil,generated as a residue in the processing of wood into pulp and paper.Results show that overall the bio-oil provides a softening effect,which,in terms of performance,leads to an improvement of the low-temperature behaviour and fatigue resistance with respect to the control bitumen,in spite of an increased tendency to permanent deformation.Although no chemical reaction appears to occur after blending,the peculiarities of the bio-oil affect the chemistry of the resulting bio-binders,whereas no phase separation is observed from the microscopic analysis.In addition,a Newtonian behaviour,an unchanged temperature susceptibility and a good fitting of 1 S2 P1 D model to the rheological data are found,regardless of the bio-oil percentage considered.These promising outcomes suggest that such bio-binders can be favourably employed for several applications in road pavements.

Chemical and rheological analysis of unaged and aged bio-extended binders containing lignin

The use of alternative renewable sources to totally or partially replace bitumen is one of the most current challenges in the road pavement sector.The growing energy cost and environmental concerns lead to the necessity to find alternative solutions,by supporting at the same time sustainability and circular economy principles.Within this framework,this paper presents the application of a powder lignin,a natural bio-polymer deriving from byproducts of wood pulp and paper industry,to replace part of bitumen.The bituminous blend consisting in 70%of bitumen and 30%of powder lignin(by weight)was made in laboratory through the use of a high shear stirring mixer,and a reference plain bitumen characterized by a similar consistency(i.e.,same penetration grade)was used as comparison.Then,an extensive investigation on chemical and rheological properties of the bio-binder is presented.Fourier transform infrared spectroscopy(FTIR),saturates,aromatics,resins and asphaltenes(SARA),bending beam rheometer(BBR),frequency sweep tests and multiple stress creep recovery tests(MSCR)with a dynamic shear rheometer(DSR)were performed.Moreover,unaged,short-and long-term aging conditions were considered.Results indicated that powder lignin dominates the rheological behavior of the bio-binder and,from chemical analysis,it seems that it partially acts as a filler and partially as a binder.This would result in improved performances at both low and high temperatures,leading to a wider temperature range of performance grade(PG).Moreover,despite a stiffening effect is recognized,lignin also offers an antioxidant potentiality,reducing the aging susceptibility of the investigated bio-binder.

Influence of morphology on high-temperature rheological properties of bitumen modified with styrene-butadiene-styrene(SBS)copolymer

Different microstructures of the same polymer-modified bitumen(PMB)were obtained by subjecting the bitumen modified with styrene-butadiene-styrene(SBS)copolymer to isothermal annealing at various temperatures.The effects of the morphology on the rheological properties of SBS-modified bitumen were investigated within the hightemperature range.The PMB microstructures were quantitatively evaluated using image analysis.A dynamic shear rheometer was used to measure the rheological parameters of the PMB samples and perform the multiple stress creep and recovery(MSCR)test.A quantitative basis could be established on which to discuss the relationship between the PMB morphology and rheology.The image analysis indicated that conditioning by isothermal annealing evidently led to a difference in the microstructure of the samples.Variation of the thermal history is demonstrated to be a practical way to vary the morphology of the PMB with the same raw materials and formulation.Compared with the two-phase morphology,the single-phase microstructure tended to have a narrower linear viscoelastic(LVE)region of the PMB.Within the LVE region,especially at low frequencies,the homogenous PMB can store more energy when experiencing loadings and is more elastic.Outside the LVE region,based on the MSCR test results,the homogenous morphology could assist in reaching a higher percentage of strain recovery after the creep period.