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Highly efficient production of ultra-lightweight clay-aerogel materials and their integrated composites for building insulation

Final Report Summary - ICECLAY (Highly efficient production of ultra-lightweight clay-aerogel materials and their integrated composites for building insulation)

Executive Summary:
40% of energy consumption and 36% of CO2 emissions in Europe are directly related to the buildings due mainly to inefficient insulation materials and systems. Currently required insulation performance may only be achieved either by installing extremely thick ordinary insulation materials and sacrificing living spaces or by using unaffordable the state-of-the-art insulation materials (e.g. silica aerogel). Specially, refurbishment cost-effective actions using traditional insulation materials will hardly be space-effective, whereas the use of thin cutting-edge materials with very low thermal conductivities is generally quite costly. The ICECLAY project aims at creating a new generation of low cost and most efficient insulation materials for EU building construction and hence enhancing the competitiveness of SMEs in EU construction sector. The project is to develop nano-structured ultra-lightweight clay-aerogel and its integrated composites by using harmless and inexpensive nano-scale minerals, water and eco-friendly or soluble/dispersible low-cost polymers, through innovative and cost effective freeze-drying processes.
The ICECLAY will provide, due to their extremely porous structure and reduced thickness, the superior thermal insulation specially designed for highly energy efficiency for buildings retrofit and advanced HVAC systems. The developed innovative thin and flexible lightweight ICECLAY board will claim to be an excellent and cheaper alternative to the unaffordable high-performance insulation materials. Additionally, possibilities of producing new products in the form of flexible tapes and as pelletized/powdered materials have been envisaged, with the objective of minimizing thermal bridging and to be used as cavity wall filling granules or filler integrated in conventional building materials.
ICECLAY aerogel can be produced in form of boards, slim strips, granules and powder. The boards can be tailored to different sizes, from small up to large 400×300 mm size panels and with 20 mm thickness, as well as the sticker slim tapes with thickness varying from 10 to 20 mm. Granules having an average diameter ranging from 1-4 mm and presenting spherical or random shape and aerogel powder (<1 mm diameter) can also be created through the production techniques developed.
ICECLAY materials are easy to handle, cut and install and non-dusty and revealed to have the physical and chemical characteristics to be integrated in several conventional building materials. Its incorporation in all the products evaluated is advantageous from a thermal insulation point of view, since it was possible to attain clear thermal conductivity level reductions with minor concentrations of aerogel, when compared with the one registered by the non-additivated base products. At the same time, it was also possible to reduce the density of some of the building construction products like cement and gypsum, which is also directly related with the possibility of having more lightweight final structures and, in some cases, like for the gypsum boards, lower transport costs and easier handling on site. In addition to the possible uses in construction solutions, other interesting applications can be foreseen for ICECLAY aerogels, for instance as thermal insulation products for high temperatures applications since it is possible to produce a specific formulation having fire resistant properties (Class A), to use as filler for cavities insulation or for vacuum insulation panels production.

Project Context and Objectives:
About 40% of energy consumption and 36% CO2 emissions in Europe are directly related to the buildings due mainly to inefficient insulation materials and systems. The 2010 recast of the Energy Performance of Buildings Directive (EPBD) sets the year 2020 as the target for all new constructions to be “Nearly Zero Energy Buildings” (nZEB), for which the public buildings are even sooner. Currently required insulation performance may only be achieved either by installing extremely thick ordinary insulation materials and sacrificing living spaces or by using unaffordable the state-of-the-art insulation materials (e.g. silica aerogel or fumed silica VIP), which in fact is normally prohibited when it comes to deal with a low budget renovation action for ordinary average householders.
The ICECLAY project aimed at creating a new generation of low cost and most efficient insulation materials for EU building construction and hence enhancing the competitiveness of SMEs in EU construction sector. While common aerogels are generally unaffordable expensive and based on hazardous production processes, the proposed porous lightweight composite solution has been made by a versatile and environmentally-benign freeze-drying process, using only harmless and inexpensive raw materials, e.g. natural occurring nanoclay minerals, water and eco-friendly low cost polymers. Our main goal was to develop a really competitive aerogel material, specially targeted for the retrofit market, where low cost and living space area savings are as important as the need for outstanding insulation ranks. These aerogels can achieve low thermal conductivity values with other properties similar to those of typical foamed polymers, such as, expanded polystyrene (EPS) and rigid polyurethane (PU) produced from non-renewable resources. ICECLAY materials could also be tailored for different applications while altering its composition and/or modifying its production process set-ups, offering the market alternative and wide-spreading aerogel solution materials. ICECLAY products could be flexible, large boards, granules or powders with good super- insulating and good acoustic properties. The moisture and fire resistance and mechanical strength can also be tailored to suite many kinds of building insulation applications and HVAC systems.
Major scientific objectives of the ICECLAY project were to effectively control and understand all clay aerogel production technologies from the gel formation to the cryogenic freezing and lyophilisation stages, and understand the role of processing parameters plaid upon the final properties of ICECLAY products and how materials can be tailored to various functionalities, in conjunction with the understanding of building and retrofit requirements for construction, sufficiently for building constructions and retrofit applications. Technologically the objectives of the project are:
1) To identify the best clays and polymers to be used in ICECLAY aerogels materials in order to achieve the best clay/polymer composite material with the desired properties for building insulation;
1) To up-scale ICECLAY technology from a laboratory testing environment to a large industrial production scale;
2) To create simulation tools that can successfully aid the development of the best clay aerogel compositions and integrations of clay aerogel with traditional building materials. Models allow to not only assess thermal performance of both ICECLAY aerogels and its integrated building products, but also guide more accurate and time and energy saving experiments of clay aerogels, and correct formulation of building components;
3) To combine the best technical properties with the least embodied energy necessary for large scale manufacturing and the lowest production costs;
5) To produce ICECLAY aerogel in several forms with low thermal conductivity, lightweight, good fire resistance to be versatile in the building sector;
6) To assess the ICECLAY versatility to be used with traditional building materials as a thermal enhancer.

Project Results:
1) ICECLAY product compositions
Based on the characterisation of several clay materials 4 clays were selected to achieve the desired properties for Iceclay aerogel. The group of selected clays included an unprocessed and cheaper sodium bentonite, nanosized and very pure sodium bentonite, natural hectorite and a synthetic hectorite. The last two were identified as the best candidates for Iceclay production for being able to produce highly thixotropic water-gel suspensions.
Pure clay aerogels were firstly produced and some conclusions were taken such as hectorite clays generally produce stronger gels than the bentonite ones and also hectorite clays interact much better with polymers, forming stronger structures. It was inferred that the insulation capability of pure clay aerogels is driven by the density so the strategy to get lowest thermal conductivity is minimizing the density and the pore size should be as small as possible.
Then, many compositions of bicomponent systems and tricomponent systems have been developed. For bicomponent systems, the bridges built between clay platelets are few, which results in the crack during freezing. The only way to get aerogel with high mechanical strength is to increase the load of materials clay or polymer, but this would sacrifice the thermal conductivity of aerogel. PVA, Cellulose, Casein and Starch were identified as the most promising polymers. PVA and starch were considered to be more effective to strengthen clay aerogels. In the tricomponent system cellulose nanowhisker was introduced and with less than 0.5% of nanowhiskers is possible to obtain stronger aerogels. However, cellulose nanowhiskers are quite expensive so cellulose microfribil were tried out. Similar results were obtained with the cellulose microfribil.
Additionally, compositions for the production of ICECLAY with water resistance have been generated. The method of cross-linking aerogel to form three dimensional network to provide aerogel water resistance and better shape recovery has been identified and tested.
2) ICECLAY manufacturing process
Manufacturing processes for various compositions have been thoroughly investigated with many important outcomes. The mixing and clay-water gel formation processes for ICECLAY were defined through rheological tests. It was found that the mixing of clay in water has to be done quickly at very high shear speed in order to promote the delamination and exfoliation of the original face-to-face association clay platelets aggregates and to favour the formation of an open tri-dimensional face-to-edge house of cards particle network structure. The highly energetically initial mixing stage should be followed by a lower shear mixing that can ease the aeration of the suspensions (avoiding air bubble entrapment). The ageing of the suspensions proved to bring not to many advantages in terms of improvement of the final aerogel properties, meaning that the subsequent mixing of the polymer should only ensure the homogenization and stabilization of the clay-polymer system in water before making the freezing stage.
Several types of freezing conditions for possible ICECLAY aerogel production were conducted, including different temperatures, from sub-zero down to cryogenic ones. The optimum freezing steps were defined. The freeze-drying process, covering from pre-freezing to secondary drying stages, has been studied. Several factors were found highly influential determining the need for a delicate set-up definition to achieve a properly freeze-dried product. All freeze-drying cycle parameters were recognised and a set up cycle was defined for laboratory production.
The samples should be frozen as fast and homogeneously as possible to promote the formation of small ice crystals that will originate subsequently smaller pore sizes within the bulk clay aerogel bodies, enhancing the thermal conductivity of the final products. The aerogels presenting the best thermal insulation properties were obtained by using a LN2 bath (-196ºC) freezing condition. However, in order to reduce the formation of cracks due to ice thermal expansion, the suspensions should be preferably frozen at a higher temperature than the glass transition of ice (-137C). Under this context, a lab ultrafreezer working at temperatures of -80ºC have produced similar results as the LN2 bath, while being possible to repeatedly obtain large frozen boards without fissuring. The mould material and design evaluation made proved that, in order to generate the best (and homogenous) results, the mould used should have one side open in order to avoid the formation of structural discontinuities due to the advance of opposite ice crystal fronts. Moreover, the most suitable material for the mould to be used was aluminium;
3) Up-scaling production and ICECLAY insulation panels
Four industrial up-scaling productions have been carried out and up-scaling processing parameters have been compiled. Specific considerations for the up-scaling productions identified for the successful production of ICECLAY. Potential compositions of developing the improved ICECLAY with balanced thermal conductivity and mechanical resistance have also been investigated. To prevent the fracture and further improve the thermal insulation, the incorporation of fibres was carried out, having the produced aerogels a smooth surface on the top, excellent integrity in shape and fine structure. Improved water resistance and many water repellents have been attempted to improve the properties of ICECLAY.
Lyostat analysis helped to describe the behaviour of the frozen ICECLAY material. It was found that ICECLAY exhibits a ‘collapse zone’. It is recommended that the formulations should be frozen below the collapse zone and maintained below these temperatures until the end of the primary drying process.
Optimizing the freezing conditions by lowering the temperature down to -65ºC, as part of a pre-cooling stage inside the freeze-dryer chamber, aerogels clearly develop better properties. Under these conditions, the resulting boards have showed many improvements, both in structural integrity and surface roughness, as well as it was possible to reduce the average pore size of the bodies, as result of smaller ice crystals being generated. At this stage the production of aerogels, in combination with slight optimizations of the formulation, leads to the development of ICECLAY products with densities as low as 40 kg m^-3 and with thermal conductivity ranks of 0.033 W m^-1 K^-1.
4) Software tools for ICECLAY product definition and performance simulation
Numerical models and user manuals for the thermal behaviour/conductivity of clay aerogels have been developed and the parameters needed were generated by sub-models starting from the individual pore within the nanostructured clay aerogel materials. The unit-cell model and global models have been tested with the experimental data of ICECLAY products with positive and accurate agreement of experimentally measured and modelled results. A series of studies have been conducted by using the developed multi-scale numerical models for assessing the influence of microstructures of different ICECLAY aerogels on their thermal behaviour. Thermal insulation of ICECLAY products has been comprehensively compiled by optimizing the microstructural parameters with the aid of the developed numerical models. The developed models have been used to guide the experimental designs for the desired performance if the ICECALY is used for the certain building components.
5) ICECLAY datasheet
A comprehensive list of performance laboratory tests was executed for ICECLAY final products and technical compliance, according to EU or ASTM standards, with focus on the evaluation of thermal insulation, mechanical behaviour, density, moisture and acoustic absorption and fire resistance. For evaluation purposes, ICECLAY panel products were compared with traditional commercial products. Complementary characterization tests were also performed with further technical information necessary for future legislation compliance and market entrance.
Performance database is established. ICECLAY bulk products have revealed to be technically competitive and clearly superior to materials like XPS, EPS or mineral wool, e.g. density of 30 kg m^-3 and thermal conductivities ranks of 0.028 W m^-1 K^-1, when composed 100% with clay and 0.030 W m^-1 K^-1 as clay polymer composites with increased mechanical strength.
6) ICECLAY integrated building materials
The ability and versatility of ICECLAY as thermal enhancing material have been evaluated for integration with conventional building materials. Many possibilities of producing new products in the form of flexible tapes and pelletized/powdered materials have been tested. ICECLAY materials were successfully integrated as fillers into a broad range of building products such as: concrete and gypsum boards and paints.
The thermal performance improvement given by the novel ICECLAY aerogels was assessed by means of the evaluation of the composites thermal performance. ICECLAY materials have revealed to have the necessary physical and chemical characteristics to be integrated without any special concerns during the mixture and drying production steps of the different products used.
Figure 1 (attached) shows the products developed in the project and in Table 1 (attached) are summarized the ICECLAY major outputs and their functionality in building sector.

Potential Impact:
Buildings are responsible for 40% of energy consumption and 36% of EU CO2 emissions. Energy performance of buildings is a key for achieving the EU Climate & Energy objectives, namely the reduction of a 20% of the Greenhouse gases emissions by 2020 and a 20% energy savings by 2020. Improving the energy performance of buildings is a cost-effective way of fighting against climate change and improving energy security, while also creating job opportunities, particularly in the building sector. Strategies for reducing CO2 emissions for building materials can be divided into ‘doing the same with less’ (increased efficiency/enhanced resource productivity) and direct ‘substitution’29. ICECLAY project can reduce the energy/CO2 impact of the building industry by either one or the other approach or combining both approaches. The project offers solutions to the problems which have been defined in the Directive on energy performance of buildings (2002/91/EC and the 2010/31/EU).
ICECLAY offers new products to the building retrofitting sector, capable of having exceptional thermal insulation abilities with only small thicknesses, reducing the space needed to comply with the new thermal efficiency regulations, thus contributing not only for indoor comfort but also for the buildings valorisation. On the other hand, the development of ICECLAY with reduced production costs: cutting up to half the costs of the conventional silica aerogels made by supercritical drying, makes ICECLAY aerogel capable of competing in terms of price with standard polymer insulation products, such not only significantly improving the competitive status of SMEs involved in the project, but also providing industries with forefront technology which should be versatile for a range of innovations. With a highly efficient and cost effective insulation solution, ICECLAY could play an important market role in ambitious major renovation programs and thus helping, both SMEs producers and end-users, to enhance their activity and economic process.
While there has still been no scaled commercial production of the developed ICECLAY due to the specific needs of the investment of a production line, the upscaling production and the performance database indicated that the developed products should be able to bring significant economic, societal and other impacts across the Europe. The coordinator (Active Aerogels) and Devan are planning the construction of a pilot plant to produce ICECLAY aerogels, and the other SMEs RAMA, ECOTERRA and SGG will have preferential access to ICECLAY technology.