Fire risk potential of carton packaging as a thermal insultation materialAbstract
Long-life packaging is being used informally as an alternative to improve thermal insulation in single-family wooden houses. Its usage is backed by environmental concerns to reuse these solid residues as a radiant barrier for heat transmission. However, some published studies have only analyzed its thermal insulation efficiency, without considering the material performance in fire situations. Given this scenario, the objective of this research is to present the analysis and classification to a fire reaction of long-life packaging. In addition to the non-combustibility test, ignitability, radiant wall panel, optical smoke density and single burn item (SBI) tests were carried out. The results showed that the material is combustible and is classified as fire reaction class VI, according to the criteria for special materials. Thus, on the findings of this study, it can be concluded that long-life packaging should not be used as a lining for the internal surfaces of buildings.
Keywords:
Fire safety; Thermal performance; Tetra Pak ® packages; Recycled material.
Resumo
As embalagens do tipo “longa-vida” estão sendo utilizadas, informalmente, como alternativa para melhorar o isolamento térmico em edificações residenciais unifamiliares de madeira. Sua utilização é justificada por questões ambientais, a fim de reaproveitar estes resíduos sólidos urbanos, e por sua caraterística como barreira radiante na transmissão de calor. Porém, alguns estudos publicados analisaram apenas sua eficiência no isolamento térmico, sem considerar o comportamento do material em situações de incêndio. Sendo assim, o objetivo deste trabalho é apresentar a análise e classificação de reação ao fogo de embalagens cartonadas do tipo “longa vida”. Além do ensaio de não combustibilidade, foram realizados testes de ignitabilidade, painel radiante de parede, densidade ótica de fumaça e single burn item (SBI). Os resultados evidenciaram que o material é combustível, sendo classificado com classe de reação ao fogo VI, conforme critérios para materiais especiais. Sendo assim, com base nos resultados encontrados, pode-se indicar que as embalagens cartonadas não devem ser utilizadas como um produto para revestir o interior de edificações.
Palavras-chave:
Segurança contra incêndio; Desempenho térmico;
Embalagens Tetra Pak
®
; Material reciclado.
Introduction
Thermal comfort can be achieved in different ways once a house is occupied: with direct action by the occupants to change their environment, with passive strategies without a significant increase in energy consumption, or with more direct solutions to achieve the desired temperature, without worrying about an increase in energy consumption (Ramos et al., 2020). The increase in energy consumption due to the use of equipment to provide thermal comfort has been an important indicator of the need for these adaptations (Abrahão; Souza, 2021). However, part of the Brazilian population cannot afford the increase in their electricity bills. As a result, the inhabitants themselves may find many makeshift solutions after occupying the property (Simões; Leder; Labaki, 2021). Thus, there is a scenario where people without adequate technical responsibility make decisions about the installation of materials that may not be suitable for use in buildings.
Even with an appeal to sustainability, it is unacceptable for materials that do not meet safety requirements to be considered for their use in any built environment. In this context, the use of Tetra Pak® packaging in homes, as a way to compensate for the lack of thermal insulation, is a common sight in humbler neighborhoods. Besides the proven improvement in internal thermal comfort (Sebeen et al., 2021), this type of packaging is also accessible, inexpensive, and considered environmentally friendly, as its reuse is characterized as the repurposing of urban solid waste. Its application is performed and encouraged by volunteers from a non-governmental organization, in the "Brasil sem Frestas" project, and its visibility is present in various digital media (Custódio; Bruxel, 2019; Ecycle, 2018).
Thermal, acoustic, lighting, and fire safety performance criteria seem to be conflicting, leading to individual evaluations that must be critically analyzed within the broader scope of application in a building (ABNT, 2021). Concerning the responsibilities and tasks of the interveners in the application of NBR 15575 (ABNT, 2021), it is indicated that the designer should request information from the product manufacturer when there is no characterization in specific standards. However, the characterization of recycled and/or reused materials is already a widespread practice in the academic community, where papers are produced with indications for use in buildings, even without the endorsement of the manufacturer.
Although there are studies indicating the thermal performance and energy efficiency of construction systems with lining of Tetra Pak® packaging, few studies analyze the other performance requirements, as layers of this packaging are composed of materials characterized by high flame propagation. The materials used to manufacture the packaging are polyethylene and cardboard paper. According to Gallo and Agnelli (1998), polyethylene is the polymer that presents the greatest capacity for flame propagation. In other words, it is a material composed of combustible layers and is being indicated to cover houses that, in most cases, are built with reused wood. It can also be mentioned that safety in these residences is even more compromised in cases where alignments, setbacks, and separations that allow access for the fire department are not respected, as the proximity between housing units can favor the spread of a potential fire to other residences.
Considering this context, this study was based on a real problem of using packaging as lining to qualify thermal insulation in residences, without due consideration of fire safety. Therefore, this article aims to present the analysis and classification of the fire reaction of Tetra Pak® type packaging boxes.
Theoretical framework
Fire reaction in civil construction
According to Thevega et al. (2022), some of the most catastrophic building fires have been attributed to the low performance of cladding materials when exposed to high temperatures. The authors indicate that the integration of lightweight and flammable polymeric materials in cladding systems increases the risk of ignition and causes a very quickly fire spread. This increased spread is a significant parameter in the selection of cladding materials, as it can impair the structural performance of the building, exposing the structure to high temperatures and compromising the planned compartmentalization. Thus, among the parameters in the selection of cladding materials, the reaction to fire ends up being one of the most critical.
A fire is basically composed of the ignition phase, flashover (when the fire is already on a large scale), and the extinction phase (Janssens, 2005). The flammability of materials influences the first stage of a fire, contributing to the increase of flames towards flashover. The flammability of the material also includes characteristics that do not directly affect ignition and fire growth but are pertinent to the fire risk to humans, such as the generation of smoke and the consequent release of toxic combustion products (Silva, 2020). In addition to flames and smokes, during a fire there is a liberation of the heat resulting from the burning of materials, which leads to chemical reactions difficult to predict when it comes to composite materials.
The development and spread of a fire are related to basic physical phenomena of thermal energy transfer from conduction, convection, and radiation processes. It is also important to consider the influence of materials and cladding products that define how much a fire may develop (Silva, 2020).
Hossain et al. (2021) indicate that the composition adopted in cladding systems is determinant of their reaction to fire, including the materials exposed on the surface, air cavities, and the form of their installation. Polymeric materials such as polyethylene (PE), polyurethane (PU), phenolic foam (PF), and different polystyrenes (XPS and EPS) are commonly used in the composition of cladding systems. However, unfortunately, most of these polymeric materials are highly combustible, with their initial degradation temperatures between 80-90 °C for both polyethylene terephthalate (PET) and PE and 250 °C for extruded polystyrene (XPS).
The appropriate use of products for cladding and the need to reduce costs is a current challenge for civil construction professionals, but the complexity is even greater due to the limited understanding of the fire performance and compliance requirements of building cladding among such professionals (Thevega et al., 2022). According to the authors, the performance of cladding materials is governed by their fire reaction properties, which in turn depend on how they are installed in the building. Of all these parameters, the type of material used in the cladding system plays an important role in the overall fire performance.
Furthermore, Hossain et al. (2021) cite that recent research works have revealed that the air cavity, openings, and gaps in the cladding system are crucial factors in the rapid growth of fires in tall buildings. The fire can quickly enter the air cavity of the cladding system and can increase the length of the flame by 5 to 10 times. In this situation, the development of the fire occurs inside this system, in a non-visible area, which makes it difficult to identify the spread of flames.
Fire reaction classification
To define the fire reaction classes of products used in civil construction, laboratory tests are conducted that consider the contribution of these products to the generation and propagation of fire and smoke in indoor environments. Initially, the product must be characterized as combustible or non-combustible. If it is combustible, tests are carried out to classified the response of the product response in a flashover fire situation.
Janssens (2005) asserts that controlling the flame spread characteristics of internal finishes is essential so that evacuation of the premises can be delayed, providing sufficient time for occupants to exit. Therefore, understanding the burning behavior of materials is crucial to comprehending their contribution to the development of a fire.
Fire reaction characteristics such as time to ignite, heat release rate, mass loss rate, and smoke generation are defined in a set of classification tests. If the material is combustible, it is necessary to proceed with a set of characterization tests based on the classification of the use according to NBR 16626 (ABNT, 2017) and the Fire Department of each Brazilian state. The number of tests to be performed depends on this initial classification. Thus, correct classification greatly influences the understanding of how the products are installed.
Table 1 presents the tests required for the classifications for floor covering products, for general construction products, and for construction products with special characteristics, according to NBR 16626 (ABNT, 2017).
Silva (2020) highlights that the mass loss and heat release of a material during burning are the main characteristics that determine the degree of risk. This rate of loss determines the amount of heat released and the possibility of producing toxic gases, as well as depends on the exposure to heat flux and the physical characteristics of the materials, such as the heat flux of the flame, the heat flux loss, and the latent heat of gasification. The heat release rate is an attribute that expresses how much heat generated by the burning material will provide the additional thermal energy necessary to grow and spread the fire.
Ignition time is another characteristic to be evaluated. It refers to the response of a material in direct contact with a flame and indicates the time to the start of burning in the combustion process under a constant heat flux (Hossain et al., 2021). After ignition, the material burns and increases its temperature, resulting in the spread of fire. The time until ignition is used to characterize the fire risk and the fire performance of materials.
However, Janssens (2005) states that these tests, in isolation, can give a false sense of security, as materials that for example pass the ignitability test may later show unsatisfactory performance when exposed to more severe conditions in a real fire. There are codes and standards for civil construction that specify the fire response characteristics of materials and building systems, based on tests that expose the material to different forms of ignition onset.
In summary, fire tests on small-sized samples can provide appropriate reference parameters for individual components, i.e., cladding and insulation materials of the cladding systems (Hossain et al., 2021). However, it may require further testing on real-scale samples.
In the case of cladding composed of boards, fire reaction tests should consider the method of installation so that the different faces of the material that may be exposed to flame incidence are considered (CBESP, 2022). It should be noted that the same material can have different fire reaction classes, depending on how they are installed in a building system.
Research indicates that one of the main causes of catastrophic fires is the use of cladding products that do not meet fire performance criteria (Thevega et al., 2022). Unfortunately, the degree of rigor in the drafting and application of these codes and standards often depends on the occurrence of large fires and the respective number of fatalities (Gragnani et al., 2017; Rodrigues; Rodrigues; Silva Filho, 2017).
One of the solutions to qualify the fire reaction of materials is the use of flame retardants. However, Troitzsch (2023) states that the durability of fire performance of products containing flame retardants can be significantly affected after aging and mechanical recycling. Mechanical recycling is possible for halogenated and non-halogenated flame-retardant systems but has only been studied for virgin thermoplastics that may be available from post-industrial waste. Also according to the authors, post-consumer waste may be unsuitable due to its mixed content, since the service life of products containing flame retardants can last decades in indoor applications and probably a much shorter period in outdoor applications.
Currently, in Brazil, there are two documents that recommend criteria for the classification of fire reaction of products used in building cladding: NBR 16626 (ABNT, 2017) and Technical Instruction no. 10/2022 (IT 10/2022) of the São Paulo State Fire Department (CBESP, 2022).
Although they present identical classification tables, there is a difference in the considerations about the interpretation of the ignitability test results. In both, when the corners and edges of the products are exposed in a real installation situation, two flame incidences should be contemplated in the ignitability test. However, in the description of the classification, ABNT specifies only the application of flame on the surface and does not mention the incidence of the flame on the edge of the specimen. On the other hand, IT 10/2022 indicates as a criterion the flame front on the surface of the material, which encompasses the two possible forms of flame incidence in the performance of the test.
The use of Tetra Pak®packaging in civil construction
This type of packaging was launched in Brazil in 1957 by Tetra Pak®. The company established itself commercially with the function of expanding the distribution of industrialized foods and increasing the shelf life of the product. It is made up of layers of cardboard paper and sheets of aluminum intercalated and finished on both the inside and outside with layers of polyethylene (Tetra Pak, 2023). The metallic-looking internal part may serve the capacity of a radiant barrier, based on the low emissivity of 0.04 of its surfaces (Vittorino; Sato; Akutsu, 2003), which could qualify the thermal performance of buildings if there were proof of the safety of its use. It is noteworthy that the manufacturer of the product indicates the use of the packaging solely for food purposes.
Because the material has adhered layers with distinct properties, recycling these packages becomes more complex. It is necessary to use a hydropulper to separate the polyethylene and aluminum, in addition to the processes of incineration, pyrolysis, thermo-injection, or thermal plasma, depending on its final use. This way, a high quantity of waste is generated (Nascimento et al., 2007). According to the report from Tetra Pak®, 192 billion packages were sold in the year 2022, with 50 billion intended for recycling, through projects formally supported by the company itself.
Studies that demonstrate energy efficiency and/or indicate it as a possibility for increasing thermal insulation of this material are present in various scientific publications, dated from the 2000s (Michels; Lamberts; Güths, 2008a, 2008b; Vittorino; Sato; Akutsu, 2003) and present up to current years. Even after the publication of the Brazilian standard NBR 15575 (ABNT, 2021), which elucidates the need for a global analysis of building systems, some studies still encourage the use in construction systems of packaging that should be discarded or destined for recycling (Cravo; Sartori; Fiorelli, 2017; Durante et al., 2023; Negrão et al., 2020; Santos Neto et al., 2019; Sebeen; Silva; Cunha, 2020).
Thermal performance with carton packaging
The use of long-life type packaging as internal cladding in residences is done by joining the opened boxes with staplers or stitching to form panels that are fixed with screws on the internal surfaces of walls and/or coverings of houses (Brasil sem Frestas, 2016). When the aluminized part is facing inside the environment, this system functions as a radiant barrier, indicated to increase thermal resistance in regions with both cold and hot days. There is also the possibility of using two systems together, forming a "sandwich," composed of two layers of opened boxes, with both aluminized faces exposed outward. Thus, theoretically, a radiant barrier that reduces heat transmission is created.
Michels, Lamberts and Güths (2008b) contextualize that in tropical countries, where the greatest thermal gain occurs through the roof of a house. In Brazil, it is very common to use simple roof tiles without lining, with intense heat transfer to the internal environment, potentially causing thermal discomfort to residents. The authors indicate that one way to reduce heat flow by radiation is with the use of radiant barriers. They also claim that the use of this type of barrier in Brazil began in the mid-1990s. Since then it has become popular for the thermal insulation of building roofs.
In research conducted in Italy, D’Orazio et al. (2013) state that the use of insulation materials with low emissivity in buildings to reduce energy consumption in summer is spreading across southern Europe. The authors conducted a study to analyze the performance of a low emissivity material in buildings located in hot and temperate climate regions, compared with other roofing system solutions. The authors compared the thermal performance of a roof with and without the radiant barrier, both installed in a large-scale experimental building constructed in the city of Ancona, Italy. The results indicated that the insulation provided by a low emissivity surface is very limited to meet the thermal performance criteria of the Italian regulations.
The lack of data on the thermal properties of carton packaging and tests on the thermal conductivity of Tetra Pak® type packaging for application in under-roofing was one of the justifications for the research by Durante et al. (2023). The authors conclude that there is potential for reusing these packages for the purpose of increasing the thermal insulation in buildings, and they also highlight the low cost of the material, easy access to the material, and sustainability.
In another study, Negrão et al. (2020) investigated the use of different materials in the composition of tiles, under criteria of cost and efficiency in thermal insulation. According to the authors, PET bottles, with high application potential, are lightweight and ecologically sustainable, but their cost would still be high compared to what is available in the market. This research concluded that tiles produced with Tetra Pak® packaging, in addition to their environmental benefits, proved to be the most appropriate, as they have quality, low cost, and are efficient for the use in popular houses,
In the city of Santa Maria, in southern Brazil, characterized by a winter with low temperatures, Santos Neto et al. (2019) conducted a study to analyze the thermal performance of residences of socially vulnerable residents, which are clad with long-life type packaging. In this research, the authors analyzed the thermal performance of the residences on typical summer days and concluded that there is a need to revise the project that indicates the use of these packages due to the high temperatures and high humidity rates measured on-site.
Michels, Lamberts and Güths (2008a) comparatively analyzed the efficiency of some types of radiant barriers found in the construction market, with sheets manufactured from urban solid waste and long-life carton packaging. The authors conclude that all the radiant barriers tested have the same efficiency in the thermal insulation of buildings.
The use of Tetra Pak® packaging in homes installed in precarious settlements has become an alternative for cladding, mainly for sealing gaps resulting from the precariousness of construction, as stated by Sebeen, Silva e Cunha (2020). The authors developed a study for a dwelling in a socially vulnerable situation, located in an irregular urban occupation in Passo Fundo, in southern Brazil. The dwelling is constructed with discarded materials and internally clad with carton packaging. From the results of their research, the authors conclude that using only the carton packaging as thermal insulation does not reduce discomfort levels, especially caused by the cold.
Method
The fire response of the packaging was determined in the laboratory, based on tests prescribed in the ABNT NBR 16626:2017 standard for fire reaction classification.
Initially, products must be classified into one of the four end-use categories. According to the Brazilian standard, Tetra Pak® packaging was classified in the special characteristics group, since in real installation conditions, they form joints through which fire can propagate or penetrate (ABNT, 2017).
For this reason, in addition to the non-combustibility, ignitability and single burn item (SBI) tests, radiant wall panel tests were carried out to characterize the development of fire on surfaces adjacent to the fire focus. Additionally, a smoke density optical test was conducted with the smoke generated by burning.
The size of the specimens is variable, depending on the standard for each test. Except for the SBI test, all the other tests use sample sizes smaller than the standard Tetra Pak pack size, as indicated below.
Materials are categorized into classes from I to VI, according to the results of the tests. All non-combustible materials are considered class I and the other classes apply to those considered combustible. From class II onwards, the letters "A" or "B" are added to differentiate the products according to the SBI and ignitability results, as detailed below. Thus, the reaction to fire classification is indicated as I, II-A, II-B, III-A and so on, up to class VI. Class VI is used for combustible materials with high heat release, rapid smoke development and accelerated flammability.
All tests were conducted at the Technological Institute of Performance and Civil Construction of Unisinos University - Brazil.
Non-combustibility
The first test conducted was for non-combustibility, following the method proposed by the ISO 1182 (ISO, 2020a) standard. The test aims at determining the non-combustibility characteristics of the sample when exposed to a constant temperature of 750°C. During the test, the release of heat, development of flames, and mass loss of the sample are checked. The test uses a cylindrical oven 150 mm in height, with an internal diameter of 75 mm and a wall thickness of 10 mm, internally heated by electrical resistances, and externally enveloped by a structure with thermal insulating material (Figure 1).
A cylindrical test specimen with dimensions of 45 mm in diameter by 50 mm in height was used. To meet these dimensions, the packaging was cut to the specified diameter, stacked, and pressed on top of one another, without the use of adhesive material (Figure 1a). Before the test, the test specimen was conditioned in a ventilated oven at a temperature of 60 ± 5°C for 24 hours and subsequently cooled in a desiccator with an external temperature of 23 ± 2°C until a constant mass was obtained.
The cylindrical samples are inserted into the oven and coupled to a support. Continuous monitoring is carried out with 3 thermocouples positioned inside the oven, in the center and on the surface of the sample. Figure 1b presents a schematic of the positioning of the test specimen inside the oven.
To be classified as non-combustible, or Class I, according to NBR 16626 (ABNT, 2017), the mass loss after the test must be less than 50%, the increase in the oven temperature cannot exceed 30 °C, and/or the time of flame emission cannot exceed 10 seconds. The results of the temperature difference (∆T), the mass difference (∆m) and the flame emission time (t) are then generated.
Ignitability
The ignitability tests followed the guidelines of the ISO 11925-2 (ISO, 2020b) standard. The test determines the ignitability characteristics of the sample in intermittent contact with a flame produced by a standard sliding burner. The flame is applied to the sample intermittently, with spacer templates used to define the point of flame application.
Two tests are carried out with the flame applied to the lower edge of the sample (Figure 2a) and two tests with the flame applied to the surface of the sample (Figure 2b).
During the test, resistance to ignition, speed of flame propagation, and release of flammable particles are evaluated. After defining the critical situation between the two points of flame application, six tests are conducted with the incidence of the flame in the worst situation.
For the test, an ignitability chamber, a pressure manometer, support for the test specimen, anemometer, templates for measuring the flame, and a stopwatch were used as indicated by the ISO 11925-2 (ISO, 2020b) standard. The fuel used was 99.5% pure propane gas at a pressure of 50 kPa.
In order to make the test specimens, the material was cut into pieces measuring 90 x 250 mm which were then conditioned in an environment controlled for temperature and humidity (23 ± 2ºC and 50 ± 5%, respectively) for 48 hours.
For classification purposes, the time it takes for the flame front (Fs) to reach a 150 mm height mark on the test specimen during the first 30 seconds of contact with the flame is measured in both flame application situations. If the flame front does not reach the mark in 60 seconds, the material is classified as Class II, III, or IV. If the mark is reached in 60 seconds or less, it is Class V or VI, and the test must be conducted again with 15 seconds of flame application. In this second test, if the flame front reaches the 150 mm mark in less than 20 seconds, the material is defined as Class VI.
Radiant wall panel
This test evaluates flame spread, occurrence of brightness peaks (flashing), flaming drippings, smoke release, and any other relevant occurrences.
The radiant wall panel test followed the guidelines of NBR 9442 (ABNT, 2019), using equipment with air and propane gas supply, mounted vertically on a metal structure, with a radiant surface 305 mm wide and 460 mm high, with pressure regulators, air filter, control valves, exhaust chimney, a pilot burner made of stainless steel, and 8 type K thermocouples with insulation resistant to 1,200 °C, in compliance with NBR 9442 (ABNT, 2019).
The test specimen is installed on a support with a 60° inclination for the incidence of the pilot flame at the top of the sample (Figure 3), and markings every 76 mm. The test environment is free of air currents, having only exhaust with an air flow at a speed of 0.4 m/s to 0.5 m/s, and controlled temperature and relative humidity, with records taken before starting the test.
During the test, flame propagation is checked with the aid of two rulers positioned next to the sample, evaluating the flame with a precision of 10 mm and the maximum temperature in the chimney thermocouples. The test is considered finished when one of three situations occurs first: the maximum temperature of the chimney thermocouples does not vary more than 5 ºC in 5 minutes, the flame front reaches all the marks on the standard support, or after a test period of 15 minutes. During the test, the occurrence of flashing is observed, which, according to the standard, are flame fronts under the surface of the specimen, lasting 3s or less.
For classification purposes, this test provides the flame spread index (Ip), which is the product of the flame spread factor by the heat evolution factor, with the result expressed as the nearest whole number multiple of 5, according to NBR 9442 (ABNT, 2019). The classification is obtained according to the criteria presented in Table 2.
Optical smoke density
In this test, materials are classified as A or B concerning specific smoke density, obtaining the maximum smoke development parameter (Dm). The specimens are tested with dimensions of 76.2 mm x 76.2 mm, and the test method used is prescribed by E662 (ASTM, 2021).
The specific smoke density is evaluated based on the analysis of the attenuation of a light beam that propagates through the smoke generated by the burning of the sample. The material is exposed to a radiant heat source at a temperature of 93±3ºC and to the contact of a flame produced by a standard burner for a maximum period of 20 minutes. The test chamber uses 99.5% pure propane gas at a pressure of 50 kPa and has an internal wall surface temperature of 35±2 ºC. The radiant heat source is applied in front of the sample surface, using spacer templates, with the point of flame application at the lower part of the test specimen.
The material is considered class A if Dm < 450 and class B if Dm ≥ 450.
Single Burning Item (SBI)
The SBI test is mandatory for materials characterized as special and, according to recommendations from the BS EN 13823 (BSI, 2020) standard, the sample is constructed inside a chamber to represent the juncture of two walls forming a right-angle corner of an internal environment. One wall is 500 mm (+/- 5mm) wide and 1,500 mm (+/- 5mm) high, and the other is 1,000 mm (+/-5mm) wide and 1,500 mm (+/- 5mm) high. The flame for this test is produced by a standard burner, through the combustion of propane gas and ignition of 30.7 kW (± 2.0 kW) and diffused in a triangular box with sand located on the edge of the two walls.
Figure 4 shows the panels joined to fulfill the dimensions required for the test and the test specimen installed. The packages were joined by staples and fixed to a wooden structure, according to the installation guidelines in Brasil sem Frestas (2016). It should be noted that only the SBI test used samples with larger dimensions, in order to show the influence of the type of product installation.
The test lasts a total of 26 minutes, and during this time, the lateral flame spread (LFS) is also checked, characterized by the spread of sustained flames (minimum 5s) to the edge of the larger wall between the heights of 500 mm and 1,000 mm.
When the SBI test is carried out, the Heat Release Rate Index (FIGRA) was generated. FIGRA is the maximum of the quotient of heat release rate from the specimen and the and the time of its occurrence. Two different total heat release of the specimen values were used, resulting in FIGRA0.2MJ and FIGRA0.4MJ.
The smoke growth rate (SMOGRA) and the total smoke production from de specimen (TSP) are also obtained through SBI test. SMOGRA is calculated as the maximum of the quotient of smoke production rate from the specimen and the time of its occurrence, and the TPS is defined in the first 600 s of exposure to the main flames (TSP600s).
The material is considered class A if SMOGRA ≤ 180 m²/s² and TSP600s ≤ 200 m²; and class B if SMOGRA > 180 m²/s² and TSP600s > 200 m².
It is also observed whether there is the release of flaming particles and disintegration of the sample.
Results
Non-combustibility
In the non-combustibility test, the temperature in the equipment increased by 114 °C, the mass of the material reduced from 34.012 to 4.148 grams resulting, and the maximum flame duration exceeded 2 minutes.
The results of the non-combustibility test were: ∆T = 114 °C; ∆m = 87.8 %; and t > 2 minutes. This result classifies the material as combustible, since the mass loss was more than 50%, the increase in oven temperature was above 30 °C, and the maximum flame duration exceeded the 2-minute limit by 10 seconds. Thus, the material failed all three normative criteria. Figure 5 shows the moment of checking the mass before and after the test and the final appearance of the material after the non-combustibility test.
Ignitability
The ignitability test, which characterizes the surface spread of flames, resulted in the failure of the material from 14 seconds of testing in the edge situation, as the standard establishes a minimum of 1 minute of flame containment up to the 150 mm mark. However, in the surface test, it maintained itself for the minimum required time. This result highlights the importance of correctly considering the material installation method for fire reaction classifications.
Figures 6 and 7 show some moments of the test for the two flame application situations. At 5 seconds, the difference in the response of the same material with the flame incidence on different parts of the sample can be visualized. In the edge test at 14 seconds, it can be seen that in addition to the propagation on the front part of the sample, burning of the back surface occurs, which can be seen through the mirror positioned at the back of the test equipment. At 30 seconds, the flame already reaches the upper edge of the sample (Figure 6), while with the flame applied on the surface, the material did not change response, without the occurrence of fire spread (Figure 7). After 30 seconds, with the burner removed, the fire extinguished when the flame was applied to the surface, but in the situation where the burner was initially placed on the lower edge, the test specimen continued to burn.
Therefore, the flame front (FS) reached the mark in 14 seconds with flame incidence at the edge of the specimen.
Radiant wall panel
The results of the radiant wall panel test express low factors of flame spread and heat evolution compared to other results. This factor may be justified due to the exposed side of the material. The long-life packaging was exposed with the aluminum side out, instead of the side with cardboard paper. This change, coupled with the fact that the wall panel test does not consider joints, led to a reduction of values compared to the other tests. To verify this behavior, the test was repeated, swapping the exposed side of the material. As expected, due to the high flame propagation of cardboard paper, the values increased, as can be seen in Table 3 and Figure 8.
Optical smoke density
In the smoke density test, there was no increase in smoke, remaining stable throughout the test period. This occurs because the material burns right at the start of the test, generating an increase in pressure and then stabilization. Due to the low density of the burned material, the smoke generated was insufficient for the photomultiplier tube to register the difference.
Single Burning Item (SBI)
In Figure 9, three moments of the SBI test can be observed. Immediately after the burner ignition, the flames already reach a height corresponding to half the height of the sample. After 2 seconds, the material begins the process of disintegration of the plates positioned in the corner. The result after 26 minutes of the test is the total destruction of the fire incidence area.
The most significant result in the test was the FIGRA, which revealed a high contribution to heat development. This value occurs due to a sudden increase in the early moments of the test, generating a temperature peak. The other values show that smoke was not generated in significant amounts and that its fixture to the cementitious board prevented lateral flame spread.
The results of the Single Burning Item test were obtained according to Table 4.
Classification
Considering that the product proved to be combustible, the ignitability test with the flame incidence on the edge of the product was crucial for the definition of the material as ClassVI, according to the criteria of IT 10/2022.
As can be seen in Table 5, considerations regarding the exposed face of the product determined its classification.
Had the ignitability test been conducted only with the flame incidence on the surface of the material, that is, without considering the exposure of the edge due to the type of installation, it would have been classified as Class V-A.
For it to be used as wall or partition lining in residential buildings, it would need to meet Class IV-A at most. Therefore, classified as VI for fire reaction, long-life packaging is unsafe for use in the civil construction, posing a serious safety risk in residential buildings.
Conclusions
The application of reused and/or recycled materials in civil construction can offer several advantages. However, it is imperative that safety conditions are prioritized.
The use of carton packaging as lining and thermal insulation may initially seem like a solution to improve the condition in buildings, presenting itself as a sustainable practice due to the reuse of this waste material. However, due to the predominance of combustible materials in its composition, which tend to ignite quickly when exposed to fire, this option becomes highly risky for such a purpose.
The results of the tests allowed a broad understanding of the response of Tetra Pak®-type packaging when used, without technical specification, as cladding inside buildings. With the results obtained in this study, the high flame spread in the ignitability and radiant wall panel tests, high decomposition in the non-combustibility test, and significant influence on the temperature increase in the environment were proven. However, the material showed low lateral spread and little smoke production from the packaging samples.
An important aspect to be highlighted in the results is the difference in the time it took for the flame front to reach the normative mark of the test specimen. In the ignitability test, the situation of flame contact with the lower edge of the material resulted in the rapid spread of fire, as its exposed layers increased the burning material contribution to the development of a fire.
For the classification of the material, the ignitability test was crucial in framing the material in Class VI, as it failed in 14 seconds. Thus, its use in civil construction is not permitted, according to IT 10/2022 of the São Paulo State Fire Department (CBESP, 2022).
It is difficult to predict the responsive behavior of a material, element, or building system to an actual future fire situation, as the way and time a fire can develop is the result of a combination of different factors. However, it is possible to define how much a product can increase or reduce the chances of a fire developing.
The way a product is installed and its location in a building define the type of exposure to flames, which is the fundamental aspect for estimating its contribution in a fire situation. The presence of cavities resulting from the type of installation and the presence of exposed edges can increase the risks of fire development. In the case of the use of carton packaging, should there be a mishap or incident within these houses, such as a flame coming into contact with the edge of the boxes, the propagation would be very rapid, with enormous difficulties in stopping it. As analyzed in this study, it is at the edge that the propagation is faster and more aggressive, and consequently, the flame would transition to other materials with larger masses and fire loads (such as wooden walls, upholstered furniture, mattresses, etc.), thus forming a chain reaction.
The high risk posed by the use of this product inside homes has therefore been proven, and the reuse of long-life packaging in construction should be banned.
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