Curso: CIENCIA DE EMPAQUES

PROPIEDADES OPTICAS

Docente:Dr. Fernando Vargas

Alumno :Jaime Eduardo Basilio Atencio

UNIVERSIDAD NACIONAL AGRARIA LA MOLINA

ESCUELA DE POSGRADODOCTORADO EN CIENCIA DE ALIMENTOS

Propiedades ópticasPara medir las propiedades ópticas, usualmente se emplea el valor de opacidad (Haze, término en ingles) establecido de acuerdo a la Norma ASTM D1003 y de brillo con la norma: ASTM D2457.

OPACIDAD definida comúnmente como la porción de luz visible que es dispersada en ángulos más amplios de 2.5° y es una medida de la turbiedad de la pieza.

BRILLOEs la capacidad que tiene el material para reflejar la luz dirigida hacia su superficie. Normalmente, se debe elegir el ángulo de medición de acuerdo a:

Transparencia del polipropilenoLa transparencia depende principalmente de la estructura semicristalina, Por lo general se cumple que a mayor cristalinidad menor transparencia.

Para mejorar la transparencia usualmente se incorpora un comonómero en forma aleatoria (copolímero random) para reducir la regularidad estructural en la cadena hidrocarbonada y/o se adiciona aditivos clarificantes

Procesamiento que ayudan a la transparencia

Efecto del choque térmico en la morfología de una pieza inyectada; de izquierda a derecha mayor choque térmico a menor choque térmico. (Foto tomada de http://www.specialchem4polymers.com/resources/articles/articleweek.aspx).

La transparencia se mejora normalmente aumentando la orientación del polipropileno y usando choques térmicos fuertes (altas temperaturas de procesamiento y bajas temperaturas de enfriamiento).

New sustainable approach to reduce cassava borne environmental waste and develop biodegradable materials for food packaging applications. Food Packaging and Shelf Life 7 (2016) 8–19 Film optical properties were assessed using transparency and color parameters. Film transparency was determined with film strips (3x2 cm) Transmission was mea-sured using a spectrophotometer (Biochrom Libra S22 UV/vis) at 700 nm. Color difference (DE) was determined according to Ramírez- Navas and Rodríguez de Stouvenel (2012) using CR-400 Chroma Meter, Konica Minolta Sensing Japan without major changes. Measurements were taken on six different equal positions on a circular film piece for 3 samples of BP and BI each, and mean values used in CIELAB L*, a*, b*

BiorientacionBOPP (película de polipropileno biorientada) y el ISBM (inyecto estirado soplado moldeado). Esta biorientación mejora propiedades como mayor rigidez, alta resistencia a la tensión, excelentes propiedades ópticas (transparencia y brillo), buenas propiedades de barrera (como por ejemplo al vapor de agua), resistencia al aceite y a las grasas; para las películas BOPP se promueve el no arrugarse o encogerse por cambios

Fig. 3. Film visual images: Transparency of peeled (BP-A) and intact (BI-B) bitter cassava films as affected by peeling and extraction conditions (NaCl, H2SO4) I, as potential printable material (II) and bag manufacturing capability (III).

To further corroborate the transparency results, film color was determined and the analysis for the color difference (DEa*b*) Showed a higher significant (p < 0.05) impact on film color, thus confirming that BI films were more transparent than those of BP The higher BI L* value is a manifest of better visual characters (minimum haze) of these films when compared to BP.

ResultadosOptical properties Both peeled (BP) and intact (BI) bitter cassava films were transparent. The BI films showed lower values of transparency (3.64%) when compared to BP (11.94%)

The BI transparency was found to be comparable to the commercial NatureFlex NVS (NVS) (4.55%) and polylactide (PLA) (3.39%) but much lower than orientated polypropylene (OPP) (13.55%) films. Therefore, BI films were more transparent than OPP and with comparable transparency to other biobased films.

Influence of colloidal silica nanoparticles on pullulan-coated BOPP filmFood Packaging and Shelf Life 8 (2016) 50–55 Optical properties Haze was measured within the wavelength range 780–380 nm, in accordance with ASTM D 1003-00, using a UV–vis high-performance pectrophotometer (Lambda 650, PerkinElmer, Wal- tham, MA, USA) coupled with a 150 mm integrating sphere, which traps the diffuse, transmitted light.

Fig. 3. Illustrative drawing of the effect arising from the addition of CS nanoparticles on the amorphous pullulan network. A dense organization is obtained due to the interaction between pullulan chains and CS particles by hydrogen bonding.

Resultados

Noticeably, after the addition of the silica nanoparticles to the pullulan formulation, the haze value of the BOPP-coated films did not change significantly, with an outstanding mean value of 1.4%. This result clearly indicates the absence of scattering centers in the nanocomposite coatings, which is often encountered in nanocomposite systems where either unsuccessful exfoliation or re-aggregation phenomena have occurred. In our systems, the even dispersion of the CS nanoparticles in the main pullulan network was achieved and macro-sized clusters did not form (Fuentes- Alventosa et al., 2013).