Photothermal characterization of low density polyethylene food packages

Abstract

The present work discuss the applicability of photothermal techniques for determining diffusion coefficients of oxygen and carbon dioxide of commercial low-density polyethylene (LDPE). The methodology involves the monitoring of diffused gas by a photoacoustic analyzer. Diffusion coefficients measured for CO2 and O2 were 2.77 x 10-8 cm²/s and 1.68 x 10-7 cm²/s, respectively. To support the gas diffusion results, thermal properties were studied using photoacoustic spectroscopy and crystallinity was determined using X-ray diffraction. Values obtained for thermal diffusivity and specific heat capacity were 1.65 x 10-3cm²/s and 2.33 J.cm-3K-1, which are in good agreement with values available in the literature for pure LDPE and thus assure reliability of diffusion coefficients values

Characterization and Analysis of Commercial Polyethylene Bags as a Prior Step to their Mechanical Recycling: A case Study in Granada, Spain

“…Commercial high density polyethylene may have melting temperatures between 120-130 °C, but in most cases the values are closer to 130 °C or even higher, such as those obtained by some authors and in the analyses carried out in this paper [19][20][21]. On the other hand, the melting temperature of low-density polyethylene is usually between 115 -125 °C, but it can vary above or below these values, since other authors have obtained melting temperatures of 113 °C or 127 °C [22][23][24].…”

Estabilidade oxidativa de óleo de peixe encapsulado em diferentes tipos de embalagem em condição ambiente

“…Para evitar os processos peroxidativos, a embalagem utilizada deve apresentar boa barreira ao oxigênio, à umidade e às radiações luminosas. Quanto mais insaturações possuírem os lipídios, maior deverá ser a proteção da embalagem, preservando a saúde do consumidor (COUTINHO, 2003;SARANTOPOULOS et al, 2002;PETTERSEN;GÄLLSTEDT;EIE, 2004;POLEY et al, 2004;FARIA, 1991;LOCKART;PAINE, 1996). Neste quesito, o filme mais utilizado comercialmente, nos blísters para cápsulas é o cloreto de polivinila, conhecido pela sigla PVC (BARKMAN, 2008;HOLLANDER, 1998) e o grau de proteção que oferece é bastante discutível.…”

Compatibilization of cellulose acetate/poly(3-hydroxybutyrate) blends by grafting copolymer

“…Specific thermal capacity of CA/PHB blends was obtained by the photothermal technique through the use of an experimental arrangement composed by an argon laser (Omicron Model 543‐AP) whose beam was modulated with a mechanical chopper (EG&G Model 650). The technique is essentially based on the measurement of temperature fluctuation of a given sample due to the absorption of modulated radiant energy .…”

“…The thermocouple monitors the variations of the temperature (Δ T ) with time ( Eq. 2 ) . where I 0 is the intensity of the white light, l s is the film thickness, ρC p is the specific thermal capacity of bulk unit, t is the time.…”

“… where I 0 is the intensity of the white light, l s is the film thickness, ρC p is the specific thermal capacity of bulk unit, t is the time. The τ is l s ρC p /(2 H ), where H is the coefficient of thermal exchange by radiation given by H = 4 σ , where σ is the Stefan‐Boltzmann constant . The specific thermal capacity of the bulk unit was obtained by argon laser (488 nm) with a potency of 11 mW.…”