The Effect of the Type of Polyethylene on .the Grafting of Styrene onto Polyethylene. III. The Crosslinking Effect in the Grafting by Preirradiation in Vacuum

The graft-copolymerisation of styrene onto the free radicals trapped in vacuum-irradiated polyethylene was investigated. By an increase of the rigidity of the foils, the grafting rate is also increased, because the termination of the growing chains becomes more hindered. But further increase of the rigidity causes grafting to stop at comparatively low values. Crosslinking of the foils also increases this rigidity, while raising of grafting temperature partially eliminates its effect. Based on the experimental results, some kinetic and structural factors governing the grafting reactions are discussed and some former theories are revised

Síntesis de un revestimiento nanocompuesto basado en TiO2/ZnAl hidróxidos dobles en capas

The aim of this investigation was the synthesis of nanocomposite coatings based on Zn-Al layered double hydroxides (Zn-Al LDH) and TiO2. The Zn-Al LDH material, which acted as the catalyst support of the active TiO2 component (in the content of 3 and 10 wt. %), was synthesized by a low super saturation co-precipitation method. The interaction between the Zn-Al LDH and the active TiO2 component was accomplished by using vacuum evaporation prior to the mechanical activation and only by mechanical activation. The final suspension based on Zn-Al LDH and 10wt. % TiO2, impregnated only by mechanical activation, showed the optimal characteristics from the aspect of particle size distribution and XRD analysis. These properties had a positive effect on the functional properties of the coatings (photocatalytic activity and self-cleaning efficiency) after the water rinsing procedure.El objetivo de esta investigaci.n fue la preparaci.n de recubrimientos de nanocompuestos basados en Zn-Al hidr.xidos dobles en capas (Zn-Al LDH) y TiO2. El material de LDH Zn-Al, que actuaba como catalizador del componente activo TiO2 (en el contenido de 3 y 10 en peso.%), se sintetiz. por un m.todo de co-precipitaci.n con baja sobresaturaci.n. La interacci.n entre el Zn-Al LDH y el componente activo TiO2 se llev. a cabo mediante el uso de la evaporaci.n al vac.o antes de la activaci.n mec.nica y s.lo por activaci.n mec.nica. La suspensi.n final basada en Zn-Al LDH y 10wt. % TiO2, impregnada solamente por la activaci.n mec.nica, mostr. las caracter.sticas .ptimas desde el aspecto de la distribuci.n de tama.o de part.cula y an.lisis de XRD. Estas propiedades ten.an un efecto positivo sobre las propiedades funcionales de los revestimientos (actividad fotocatal.tica y eficiencia de auto-limpieza) despu.s del procedimiento de aclarado de agua

Preparación y caracterización de un recubrimiento protector autolimpiante de TiO2/caolín

The application of self-cleaning coatings presents one of the most effective ways to protect the surfaces of the building materials. The effect of TiO2/kaolin based coatings applied to three types of substrates: non-porous, porous and highly porous, was investigated. Mechanical activation was applied for the impregnation of the active TiO2 component (in content of 3 and 10 wt. %) into the kaolin support. Surface properties (roughness, hydrophilicity and micro-hardness) and functional properties (photocatalytic activity and self-cleaning efficiency) were studied in order to define the optimal formulation of the applied coatings. The effect of the photocatalytic behavior of the coated substrates in terms of self-cleaning ability was assessed by the photodegradation of Rhodamine B, performed before and after durability tests. The results obtained in this paper showed that photocatalytic activity of the TiO2/kaolin composite coating generally depends on the procedure of TiO2 impregnation into the kaolin clay and the loaded TiO2 content.La aplicación de recubrimientos autolimpiantes presenta una de las maneras más efectivas de proteger las superficies de los materiales de construcción. Se ha investigado el efecto de recubrimientos basados en TiO2/caolín, aplicados sobre tres tipos de sustratos: no poroso, poroso y altamente poroso. Se utilizó activación mecánica para la impregnación del componente de TiO2 activo (en contenido del 3 y 10% en peso) sobre el soporte de caolín. Se han estudiado las propiedades superficiales (rugosidad, hidrofilicidad y microdureza) y las propiedades funcionales (actividad fotocatalítica y eficacia autolimpiante) para definir la formulación óptima de las capas aplicadas. El efecto del comportamiento fotocatalítico de los sustratos revestidos en términos de capacidad de autolimpieza se evaluó mediante la fotodegradación de Rodamina B, realizada antes y después de las pruebas de durabilidad. Los resultados obtenidos en este trabajo mostraron que la actividad fotocatalítica del revestimiento de TiO2/ caolín, dependen en general del procedimiento de impregnación de TiO2 en la capa de caolín y el contenido utilizado de TiO2

Preliminary approach to bio-based surface healing of structural repair cement mortars

Mitigating the maintenance and repair costs of structures and infrastructures is a major problem in all countries. The aim of this research work is to analyse the performance of surface healing technique for crack control of cement-based mortars for structural repair in maritime environments. Microbiologically induced calcite precipitation (MICP) with ureolytic bacteria Sporosarcina pasteuri DSM 33 was introduced for crack-healing. Only main cracks were filled with the bioagent (bacterial cells and nutrients) for cost-saving purpose. It is intended to analyse the effectiveness of this technique for structural application in areas exposed to cyclic moisture changes. Hygric properties and their relation to durability increase were analysed through moisture buffering tests, capillary, porosity, compressive strength, SEM and microscopy analysis before and after bio-agent application to evaluate the evolution of the precipitation. For the first time, moisture buffering value (MBV) was used to evaluate the performance of the self-healed mortar and time needed for bacterial precipitation. The treated material can be classified as good in terms of MBV, and there was a general increasing trend of moisture buffering behaviour in self-healed samples. SEM analysis showed distinctive differences between the treated and non-treated cracks. The results show that bio-agent had remarkable effect on compressive strength recovery (over 87% of original value) after 21 days of healing and positively affected the initial stage of capillary absorption

Comparison of Microbially Induced Healing Solutions for Crack Repairs of Cement-Based Infrastructure

Reinforced concrete crack repair and maintenance costs are around 84% to 125% higher than construction costs, which emphasises the need to increase the infrastructure service life. Prolongation of the designed service life of concrete structures can have significant economic and ecological benefits by minimising the maintenance actions and related increase of carbon and energy expenditure, making it more sustainable. Different mechanisms such as diffusion, permeation and capillary action are responsible for the transport of fluids inside the concrete, which can impact on the structure service life. This paper presents data on microbially induced repair and self-healing solutions for cementitious materials available in the contemporary literature and compares results of compressive strength test and capillary water absorption test, which are relevant to their sealing and mechanical characteristics. The results of the repair and self-healing solutions (relative to unassisted recovery processes) were “normalized.” Externally applied bacteria-based solutions can improve the compressive strength of cementitious materials from 13% to 27%. The internal solution based solely on bacterial suspension had 19% improvement efficacy. Results also show that “hybrid” solutions, based on both bio-based and non-bio-based components, whether externally or internally applied, have the potential for best repair results, synergistically combining their benefits