PSI - Issue 13

Mark Kopietz et al. / Procedia Structural Integrity 13 (2018) 143–148 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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2

polymers (GFRP) as key repair material. For manufacturing, a glass fiber fabric mat is impregnated by hybrid resin, and then applied on an inflatable packer which is subsequently placed at the damaged position. After blowing up the packer and curing of the resin the resulting GFRP in the sewer pipe represents an impermeable and mechanical resistant “pipe -in- pipe” system. Organic/inorganic hybrid resins came up in the end of the 90’s of the last century as matrices in glass fiber reinforced plastics for trenchless sewer repair as well as grouting materials in mining and tunneling. They impress by their outstanding media and heat resistance. These hybrid resins are produced by an indirect reaction between water (from water glass, WG) and isocyanate (from polymeric methylene diphenyl diisocyanate, PMDI), further emulsified by additives. In the first step a primary amine is built (eq. 1) which immediately reacts in a nucleophilic reaction with another isocyanate to build the (poly)urea group (eq. 2). Released carbon dioxide is simultaneously bonded by the sodium silicate to generate carbonate crystals and (poly)silicate particles (eq. 3) R N C O R NH 2 + CO 2 + H 2 O (1)

O

R N C O

n

R

R

(2)

N N H H

R NH 2

n

m Na 2 O · n SiO 2 · x H 2 O + m CO 2

n SiO 2 · ( x – y )H 2 O + m Na 2 CO 3 + y (H 2 O)

(3)

Due to the water-in-oil character of both components suitable emulsifiers are deeply necessary to earn well-mixed and highly reactive emulsions. Market established 3P Resins® ( p olyi-socyanates, p olysilicates, p hosphates) contain organic phosphates (e.g. isopropylphenyl phosphate, tris(2-chloro-1-methylethyl)phosphate)) in different amounts [1]. Because of REACH regulations for substituting dangerous chemicals (EG 1907/2006), and furthermore, to prevent an unfavorable diffusion of the chemically non-bonded phosphates into the environment past studies successfully focused on replacing them either through melamine-formaldehyde [2], or epoxy [3], or vinyl ester resin [4]. However, these substitutes are all petroleum based. This is why recent studies further focused on the replacement of organic phosphates by functionalized vegetable oil made from renewable resources to increase the bio-content of the matrix and decrease the greenhouse effect via reduction of CO 2 emissions. Improved mechanical properties regarding bending and com pression stiffness were obtained [5]. Furthermore, such substituted systems have demonstrated an improved adhesion between fibers and matrix, further enhanced through the addition of suitable coupling agents or surfactants [6]. Nevertheless, applied systems are not only stressed by abrasion in waste water but also by corrosive media, i.e. acid or alkaline solutions. Capillary effects lead to penetration of media into the composites structure. Chemical destruction of both, the matrix and the fiber as well as the adhesion between them may occur. This alters the load transfer between matrix and fibers and results in less stable composites. Thus, the impact of different media on such composites was investigated in this work. Both, 3P and 2P two-component formulations consisted of components A (WG) and B (PMDI with respective emulsifier and additive), and they were prepared in constant volumetric ratio of 1:2. To homogenize both components the mixture was stirred by a turbine stirrer for 1 min at 500 rpm. The necessary chemicals were used as received, Table 1. While for 3P Resin® component B was purchased in a premixed state, the novel 2P resin had to be mixed manually. Thus, neat 2P consisted of Ongronat® 2500 and Lankroflex™ L (15 vol% related t o whole PMDI/WG volume). Nonionic surfactant Efka® WE 3110 with the amount of 1 vol% of was added for further modification and improvement of the fiber/matrix adhesion. 2. Experimental 2.1. Materials and Sample Preparation