Atualmente, os adesivos de contato de policloropreno base aquosa, possuem capacidade de adesão, variando entre 1,15 até 2,75 kgf/cm2. Em contrapartida, os adesivos de policloropreno base solvente, suportam tensões médias de cisalhamento de 3,8 kgf/cm2. Esta pesquisa apresenta uma proposta inovadora de condicionamento magnético do adesivo de contato de policloropreno base aquosa com o objetivo de aumentar a capacidade de aderência entre o adesivo e o substrato. Para promover um incremento na capacidade de adesão do adesivo de policloropreno base aquosa, formulou-se um adesivo utilizando um nanoaditivo, o gás carbônico como catalisador e um processo de condicionamento magnético precedente à etapa de aplicação sobre os substratos. Os resultados obtidos demonstraram aumento médio de 292 % na tensão de cisalhamento do adesivo condicionado magneticamente quando comparado com o adesivo de mesma formulação sem o condicionamento magnético, e quando comparado com um adesivo comercial de policloropreno base aquosa, o aumento foi de 122 %. / Currently, the aqueous based polychloroprene contact adhesive presents an adhesion capacity variation between 1,15 and up to 2,75 kgf/cm2. However, the solvent based polychloroprene adhesives support average tensions of shearing of 3,8 kgf/cm2. This research is an innovative proposal for magnetic conditioning of the aqueous based polychloroprene contact adhesive with the purpose of increasing the adherence capacity between the adhesive and the substrate. To promote an increase of adhesion to the aqueous based polychloroprene contact adhesive, we formulated one adhesive using a nano-additive, carbon dioxide as catalyst, and a magnetic conditioning process before the phase of application on the substrates. The results obtained show an average increase of 292 % in the shearing tension of the adhesive magnetically conditioned when compared with an adhesive of the same formulation without the magnetic conditioning and 122 % increase when compared to the commercial aqueous based polichloroprene adhesive.

Atualmente, os adesivos de contato de policloropreno base aquosa, possuem capacidade de adesão, variando entre 1,15 até 2,75 kgf/cm2. Em contrapartida, os adesivos de policloropreno base solvente, suportam tensões médias de cisalhamento de 3,8 kgf/cm2. Esta pesquisa apresenta uma proposta inovadora de condicionamento magnético do adesivo de contato de policloropreno base aquosa com o objetivo de aumentar a capacidade de aderência entre o adesivo e o substrato. Para promover um incremento na capacidade de adesão do adesivo de policloropreno base aquosa, formulou-se um adesivo utilizando um nanoaditivo, o gás carbônico como catalisador e um processo de condicionamento magnético precedente à etapa de aplicação sobre os substratos. Os resultados obtidos demonstraram aumento médio de 292 % na tensão de cisalhamento do adesivo condicionado magneticamente quando comparado com o adesivo de mesma formulação sem o condicionamento magnético, e quando comparado com um adesivo comercial de policloropreno base aquosa, o aumento foi de 122 %. / Currently, the aqueous based polychloroprene contact adhesive presents an adhesion capacity variation between 1,15 and up to 2,75 kgf/cm2. However, the solvent based polychloroprene adhesives support average tensions of shearing of 3,8 kgf/cm2. This research is an innovative proposal for magnetic conditioning of the aqueous based polychloroprene contact adhesive with the purpose of increasing the adherence capacity between the adhesive and the substrate. To promote an increase of adhesion to the aqueous based polychloroprene contact adhesive, we formulated one adhesive using a nano-additive, carbon dioxide as catalyst, and a magnetic conditioning process before the phase of application on the substrates. The results obtained show an average increase of 292 % in the shearing tension of the adhesive magnetically conditioned when compared with an adhesive of the same formulation without the magnetic conditioning and 122 % increase when compared to the commercial aqueous based polichloroprene adhesive.

Submitted in fulfilment of the requirements for the Degree Master of Philosophy: Quality Management, Durban University of Technology, 2017. / The proliferation of nanotechnology, whilst perceived to be positive for human advancement, introduces potential risks when applied to food. Silicon Dioxide (E551), a common food additive made up of particles in the nano-range, is found in spices, salt, sweets and some frozen foods and functions as an anti-caking agent to allow these food products to flow and mix evenly. According to Codex Alimentarius, E551 is generally regarded as safe (GRAS), provided that food manufacturers apply good manufacturing practice (GMP) principles and use the lowest possible amounts necessary. Smaller nanoparticles are more readily taken up by the human body than larger sized particles and could be injurious to human health. While the use of E551 is strictly regulated in some countries, there is growing debate regarding the health and safety implications for consumers and the quality of food. This study examined the quality of selected food products containing E551 (nanosilica) in South Africa (SA). A mixed method paradigm (qualitative and quantitative) and an experimental research strategy were adopted. Respondents were purposefully selected, their participation in this study was voluntary and confidentiality was maintained. Pilot studies were conducted for the semi-structured interviews and the survey, with a sample size of one food expert and three food technologists, respectively. The main study consisted of interviews, a survey and experimental work. The interviews, conducted with five food experts, were recorded and transcribed to ensure credibility. The results were interpreted and analysed against existing literature using thematic content analysis. The findings suggest that it was critical for food manufacturers to demonstrate the safe use of products without posing any safety risks to the consumer and the environment; and for the South African government to address and regulate the application of nanomaterials in food either by legislation or guidelines. The survey was conducted with a sample population of thirty food technologists who reported that public awareness of nanotechnology was limited as many consumers were not familiar with this technology. Descriptive and inferential statistics were used to analyse the quantitative data. Content validity ensured that the survey focused on concepts and constructs that emerged from the review of literature on the application of nanotechnology in food products. Cronbach’s alpha index was used to assess the reliability of the surveys and found α = 0.862 and α = 0.809 for food additives awareness and nanosilica safety in food, respectively. Different characterisation methods, such as Fourier Spectra Infrared Spectroscopy (FT-IR), Energy Dispersive X-ray Spectroscopy (EDX) and X-ray Diffraction (XRD), were used to determine the type and form of silica, and its levels in selected food brands available in SA. This was compared against similar products manufactured and packed in the European Union (EU) and Asia. This study benchmarked against the EU standard because of its more stringent guidelines in the field of nanotechnology and regulations. The results indicate that while the comparative EU food sample conformed to the European Food Safety Association (EFSA) permissible level of 1 %, the South African sample levels were higher. Even though the regulatory standards are different in both countries, the potential health effects remain the same. Significantly, the most prominent finding of this study is that the form of silica in some of the South African and Asian products were crystalline in nature, rather than synthetic amorphous silica (SAS), which is indicative of E551. Thus, it stands to reason that the generalised limit set by Codex Alimentarius was inadequate to regulate and control the quantity and type of E551 used as it varied from each of the selected samples. The identification of traces of crystalline silica is of concern since studies in literature showed that exposure to and ingestion of crystalline silica that was not food grade, is likely to induce perilous health effects such as cancer and fibrosis in humans. In light of this finding on the crystalline nature of silica in the studied brands, it is therefore imperative that specific limits and regulations be put in place and enforceable in SA to ensure that products sold are in line with acceptable standards as found in some developed countries like the United States of America (US) and EU. In view of the above, and to ensure proper monitoring and minimal risk exposure, a risk management framework, a ‘Hazard identification, Access the risks, Control the risks’ (HAC) model, was developed and recommended to ensure that the correct form and type, and limits of silica is used and the associated risk controls applied. / M