Lifetime prediction of polymers

Hamid, Syed; Amin, Mohamed Bakr

doi:10.1002/app.1995.070551003

Cited by 86 publications

(43 citation statements)

References 7 publications

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“…8,9,22 Hamid and Amin studied both natural and accelerated weathering of low-density polyethylene. 23 They concluded that crosslinking and chain scission reactions occur simultaneously. However, during the initial stages of exposure of WF/HDPE composites to accelerated weathering, crosslinking in the matrix does not predominate.…”

Section: Crystallinity Changes Of Hdpementioning

confidence: 99%

Effects of pigments on the UV degradation of wood‐flour/HDPE composites

Wang

et al. 2010

J of Applied Polymer Sci

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ABSTRACT:The effects of different color pigments on the durability of wood-flour/high-density polyethylene composites (WF/HDPE) were evaluated by UV-accelerated weathering tests. WF/HDPE composites were dyed using three different color inorganic pigments, which were added at 2% based on the weight of the composite. Samples were weathered in Q-panel UV aging equipment for 1500 h. All samples showed significant fading and color changes in exposed areas. Changes in surface chemistry were studied using spectroscopic techniques. X-ray photoelectron spectroscopy (XPS) was used to verify the occurrence of surface oxidation. Changes in carbonyl groups (C¼ ¼O), PE crystallinity, cellulose CAO, and lignin aromatic C¼ ¼C were detected by Fourier transform infrared (FTIR) spectroscopy. The results indicate that surface oxidation occurred immediately within exposure 250 h for all samples; the surface of the control WF/HDPE composites was oxidized to a greater extent than that of the dyed WF/HDPE. This suggests that the addition of pigments to the WF/HDPE composites results in less weather-related damage. The surface configuration observed by scanning electron microscopy revealed that WF/HDPE composites degraded significantly on accelerated UV aging, with dense cracking apparent on the exposed surface. Carbon black had a more positive effect on color stability than the other pigments.

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Section: Crystallinity Changes Of Hdpementioning

confidence: 99%

Effects of pigments on the UV degradation of wood‐flour/HDPE composites

Wang

et al. 2010

J of Applied Polymer Sci

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“…In accelerated weathering, temperatures are elevated above that of the exposure temperatures of natural weathering. Hamid and Amin [14] studied both natural and accelerated weathering of low-density polyethylene (LDPE). They concluded that crosslinking and chain scission reactions take place simultaneously.…”

Section: Crystallinity Changesmentioning

confidence: 99%

“…The degradation reactions therefore occur predominantly in the amorphous region and are controlled by the diffusion of oxygen in this region [10]. While chain scission occurs in the amorphous phase of the polymer, UV-induced crosslinking occurs in imperfect crystalline regions [14].…”

Section: Introductionmentioning

confidence: 99%

“…FTIR spectroscopy has been used to monitor carbonyl group formation [9,11,12,[14][15][16][17], vinyl group formation [9,11,14], and changes in crystallinity [13,[18][19][20][21] of weathered polyethylene. X-ray photoelectron spectroscopy (XPS) has also been found useful to study the concentration of carbon to oxygen atoms of aged polyethylene [22,23] and wood-flour-filled polyvinyl chloride [7].…”

Section: Introductionmentioning

confidence: 99%

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Surface chemistry changes of weathered HDPE/wood-flour composites studied by XPS and FTIR spectroscopy

Stark

Matuana

2004

Polymer Degradation and Stability

348

149

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The use of wood-derived fillers by the thermoplastic industry has been growing, fueled in part by the use of wood-fiberthermoplastic composites by the construction industry. As a result, the durability of wood-fiber-thermoplastic composites after ultraviolet exposure has become a concern. Samples of 100% high-density polyethylene (HDPE) and HDPE filled with 50% woodflour (WF) were weathered in a xenon arc-type accelerated weathering apparatus for 2000 h. Changes in surface chemistry were studied using spectroscopic techniques. X-ray photoelectron spectroscopy (XPS) was used to verify the occurrence of surface oxidation. Fourier transform infrared (FTIR) spectroscopy was used to monitor the development of degradation products, such as carbonyl groups and vinyl groups, and to determine changes in HDPE crystallinity. The results indicate that surface oxidation occurred immediately after exposure for both the neat HDPE and WF/HDPE composites; the surface of the WF/HDPE composites was oxidized to a greater extent than that of the neat HDPE. This suggests that the addition of WF to the HDPE matrix results in more weather-related damage. The results also show that while neat HDPE may undergo crosslinking in the initial stages of accelerated weathering, WF may physically hinder the ability of HDPE to crosslink, resulting in the potential for HDPE chain scission to dominate in the initial weathering stage.

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“…A variabilidade dos elementos na natureza é o aspecto que mais dificulta a simulação da fotodegradação em laboratório, onde geralmente se utilizam condições padronizadas e controladas. Algumas tentativas de encontrar uma equivalência entre exposições naturais e artificiais foram realizadas e relatadas na literatura [17][18][19][20][21][22][23][24][25][26][27][28][29] , mas os resultados obtidos parecem ser insuficientes para se propor correlações mais abrangentes entre o ambiente e os sistemas de exposição. O tema ainda é muito controverso, carecendo de um maior número de estudos.…”

Section: Introductionunclassified

Avaliação da fotodegradação de poliolefinas através de exposição natural e artificial

Fechine¹,

Santos²,

Rabello³

2006

Quím. Nova

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Recebido em 23/3/05; aceito em 13/9/05; publicado na web em 14/3/06 THE EVALUATION OF POLYOLEFIN PHOTODEGRADATION WITH NATURAL AND ARTIFICIAL EXPOSURE. Samples of polypropylene (PP) and low-density polyethylene (LDPE) were submitted to ultraviolet radiation, in the natural environment and also in the laboratory. Chemical modifications were quantified by the carbonyl index (CI), mechanical properties and melt flow index. The degradation in the laboratory was comparatively faster than in the environment for both types of polymers. The accelerating factor was determined for the various properties investigated. This parameter, however, showed a large variation with the degradation criteria and the type of polymer. The existence of a "universal accelerating factor", therefore, was not observed in the current study.Keywords: polypropylene; low-density polyethylene; photodegradation. INTRODUÇÃOTodos os polímeros orgânicos não estabilizados são degradados sob exposição à luz solar na presença de oxigênio. Entretanto, as taxas de degradação fotooxidativa dependem fortemente da natureza química do polímero, com a vida útil variando desde poucos meses para o polipropileno, até alguns anos para o politereftalato de etileno (PET), poli(metacrilato de metila) (PMMA) e o politetrafluoretileno 1,2 . Os problemas da fotodegradação têm aumentado com o crescente uso de polímeros em aplicações exteriores aliado à necessidade da redução de custos com aditivos fotoestabilizantes. Durante o processo degradativo ocorrem mudanças físicas e químicas no polímero que levam à descoloração, fissuramento, perda de brilho e queda de resistência mecânica. Tais fenômenos estão quase sempre associados a processos de cisão de cadeia e, em alguns casos, ocorrem também reticulações 2 . A investigação da degradação foto-oxidativa de polímeros é um dos principais elementos que subsidiam o desenvolvimento do produto e sua expectativa de vida útil. Ao se expor o material às intempéries e avaliar os efeitos nas suas propriedades busca-se obter uma fotografia do que aconteceria durante a aplicação desse produto. Nesse tipo de investigação utilizam-se a exposição no ambiente natural e a exposição simulada, realizada em laboratório. Nas exposições em laboratório, as variáveis mais importantes são tipo de fonte geradora de radiação ultravioleta, intensidade de radiação, temperatura, umidade e ciclos térmicos [3][4][5][6][7][8] . A resposta do material à exposição depende, portanto, da intensidade dessas variá-veis. É comum a intensificação desses fatores para aceleração da fotodegradação e, assim, se obter resultados mais rápidos. Outra maneira de se investigar a resistência fotoquímica dos polímeros é a exposição ambiental, onde os diversos constituintes do ambiente, como radiação ultravioleta, luz visível, temperatura, intempé-ries, umidade, etc, afetam a estrutura química do polímero provocando degradação. A intensidade desses elementos do ambiente natural varia significativamente com o local de exposição, a época do ano e o período do dia, de tal modo qu...

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Lifetime prediction of polymers

Cited by 86 publications

References 7 publications

Effects of pigments on the UV degradation of wood‐flour/HDPE composites

Effects of pigments on the UV degradation of wood‐flour/HDPE composites

Surface chemistry changes of weathered HDPE/wood-flour composites studied by XPS and FTIR spectroscopy

Avaliação da fotodegradação de poliolefinas através de exposição natural e artificial

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