Orientation, crystallization, and haze development in tubular film extrusion

White, James L.; Çakmak, Mükerrem

doi:10.1002/adv.1988.060080105

Cited by 33 publications

(17 citation statements)

References 118 publications

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“…O fluxo é um efeito reológico conhecido, que pode finalmente ser correlacionado à estrutura molecular. Avalia-se que a aspereza da cristalização ocorra devido à formação de agregados cristalinos na superfície dos filmes ou próximos dela [27] . [27] estudaram uma grande faixa de materiais semicristalinos (PEBD, PEAD, PELBD, PP e PBT) e amorfos (PS e PMMA), constatando que a cristalização é a razão principal para a aspereza da superfície, enquanto o efeito reológico desempenha um papel secundário, mas importante.…”

Section: Coeficiente De Fricção -Cofunclassified

“…Avalia-se que a aspereza da cristalização ocorra devido à formação de agregados cristalinos na superfície dos filmes ou próximos dela [27] . [27] estudaram uma grande faixa de materiais semicristalinos (PEBD, PEAD, PELBD, PP e PBT) e amorfos (PS e PMMA), constatando que a cristalização é a razão principal para a aspereza da superfície, enquanto o efeito reológico desempenha um papel secundário, mas importante. Para os filmes soprados de PEBD convencional, a elasticidade da massa fundida é a principal causa da aspereza, ao mesmo tempo uma maior aspereza no PEAD é atribuída ao seu elevado grau de cristalização [28] .…”

Section: Coeficiente De Fricção -Cofunclassified

“…Constata-se também um maior número de cristalitos do PEAD com o aumento da RS, isso permite mais tempo para a formação dos cristalitos e que eles se formem em maior quantidade, como comprovado pela literatura [27] .…”

Section: Microscopia óPtica -Mounclassified

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Estudo comparativo da influência da razão de sopro nas propriedades de filmes tubulares de PEBD e PEAD

Ferreira

Santana

2015

Polímeros

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ResumoO objetivo deste trabalho é avaliar a influência do tipo de poliolefina e da razão de sopro (RS) nas propriedades físicas e térmicas de filmes produzidos em processo de extrusão tubular. No processamento foram utilizados um polietileno de baixa densidade (PEBD) e um polietileno de alta densidade (PEAD) transformados numa linha de extrusão de filme tubular com três RS de 1,5:1; 2,5:1 e 3,5:1. Os resultados das caracterizações físicas dos filmes mostraram maior variação de espessura no perímetro dos filmes tubulares de PEAD, quando comparados aos de PEBD. O aumento da RS causou uma diminuição de amplitude desta variação nos filmes tubulares de PEBD e diferenças nas propriedades ópticas. O coeficiente de atrito (COF) dos filmes foi menor para o PEAD e não teve variação significativa com o aumento da RS utilizada. Em relação às propriedades mecânicas, os filmes de PEAD apresentaram maior resistência à tração e menores valores de deformação no ponto de escoamento em ambas as direções. As RS maiores apresentaram similaridade nas tensões e nas deformações entre as direções da máquina (DM) e transversal (DT). A RS ideal, constatada para os filmes processados com PEBD, é 2,5:1 e com PEAD, é 3,5:1. Os filmes de PEAD apresentaram opacidade maior e menor brilho, quando comparados aos filmes de PEBD. Os resultados comprovaram valores conhecidos na literatura, entretanto introduziu-se uma inovação neste estudo: a utilização da técnica termográfica digital portátil, que permite visualizar, de maneira instantânea (on-line), as variações de temperatura no perímetro do balão, na zona de névoa (região de cristalização ou solidificação do filme). Palavras-chave: PEBD, PEAD, PELBD, razão de sopro, linha de névoa, filme tubular, termográfica. AbstractThe purpose of this study is to evaluate the influence of the polyolefin type and the blow-up ratio (BUR) on the thermal physical properties of films produced in a blown film extrusion process. It was used low density polyethylene (LDPE) and high density polyethylene (HDPE) processed in a blown film extrusion line at three BUR of: 1.5:1; 2.5:1 and 3.5:1. The results of physical characterization on these films demonstrated that the increase in the BUR shows a higher thickness variation in the perimeter of tubular films and, therefore, optical properties variation. The coefficient of friction (COF) of the films was smaller for HDPE and did not have significant variation with the increase in the BUR applied. Regarding mechanical properties, HDPE films showed higher tensile strength and lower strain values in the yield point, in both directions. The largest BUR showed higher similarity of the tensions and strains between the machine direction (MD) and transverse direction (TD). The ideal BUR observed for films processed with LDPE is 2.5:1, for HDPE this number is higher and close to 3.5:1. The HDPE films showed more opacities and less brightness when compared to LDPE films. The results prove well known values in the literature, however, there was an innovation introduced in this study ...

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Section: Coeficiente De Fricção -Cofunclassified

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Estudo comparativo da influência da razão de sopro nas propriedades de filmes tubulares de PEBD e PEAD

Ferreira

Santana

2015

Polímeros

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“…the crystallization starting, occurs at the same axial location With reference to the last point, the frost line height depends essentially on the cooling air flow; in particular, increasing the air velocity reduces the frost line height [11]. The experiments having been carried out without changing the cooling conditions and the blow up ratio, the position of the frost line is approximately constant.…”

Section: Experimental Testsmentioning

confidence: 99%

Thermography for polymers film blowing

Berardi¹,

Cuccurullo²,

Maio³

1998

Proceedings of the 1998 International Conference on Quantitative InfraRed Thermography

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Polymer temperature distribution in film blowing was investigated by means of an IR thermography system sensing in the window between 2 and 5Jlm. Since in this band polymers behave as selective emitters, the emission and reflection of the radiation are bulk and surface phenomena. Thus, a preliminary study on the film radiative behaviour is presented in order to characterise the thermography readout on semitransparent sheets. Then, experiments on film blowing extrusions have been performed with polypropylene on a pilot plant in order to measure the on-line film temperature distribution for different working conditions.

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“…This was recognized by Stein5–7 and Wilchinsky8, which resulted in different equations to represent biaxial orientation. These subsequently were modified by White and Spruiell,9 and the resulting equations are most commonly employed today to describe the biaxial orientation state of blown films 3, 4, 9–11. The White–Spruiell biaxial orientation factors quantify the orientation of the unit/segment of interest with respect to the machine direction (MD) and transverse direction (TD) of blown films as follows: In the above equations, ϕ 1 and ϕ 2 are the angles made by the orienting segment of interest (seg) with respect to the MD and TD of the blown film, respectively.…”

Section: Introductionmentioning

confidence: 99%

Training evaluation of a course in diabetic retinopathy screening

Pauli

Huber

Duncan

et al. 2005

European Diabetes Nursing

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The success and effectiveness of diabetic screening programmes are dependent on the availability of appropriately trained image graders. This study was designed to evaluate graders enrolled on a locally devised, formal training course by means of a performance-based measure. The course consisted of four days of classroom-based tuition followed by three months of practice-based learning in the workplace. The aim was to establish whether trainees showed an improvement in their ability to grade images, and secondly whether test sets of images are useful in measuring training outcome. Thirteen trainees were required to grade a test set of 24 single images both before and after training. A significant improvement in sensitivity (from 35% before training to 45% after training) was observed as a result of training but at a cost of a decline in specificity. Trainees' confidence ratings measured on a five-point scale increased from an average of 2.4 to 4.1 (p<0.01). We concluded that the course needs to focus more on trainees' ability to discriminate between normal and abnormal images as well as improving grading accuracy in line with increased grading confidence. Test-based course evaluation can be seen to be a valuable instrument in establishing a quality standard for stated learning outcomes. In this research it has clearly indicated weaknesses of the training programme in its current form. Copyright © 2005 FEND.Eur Diabetes Nursing 2005; 2(2): 58-62.

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Orientation, crystallization, and haze development in tubular film extrusion

Cited by 33 publications

References 118 publications

Estudo comparativo da influência da razão de sopro nas propriedades de filmes tubulares de PEBD e PEAD

Estudo comparativo da influência da razão de sopro nas propriedades de filmes tubulares de PEBD e PEAD

Thermography for polymers film blowing

Training evaluation of a course in diabetic retinopathy screening

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