Polypropylene optical properties

Optical Properties. The optical properties of a plastic which are important are refraction, transparency, gloss and light transfer. The reader is referred to BS 4618 1972 for precise details on these terms. Table 1.9 gives data on the optical properties of a selection of plastics. Some plastics may be optically clear (e.g. acrylic, cellulosics and ionomers) whereas others may be made transparent. These include epoxy, polycarbonate, polyethylene, polypropylene, polystyrene, polysulphone and PVC. 

Sometimes the hazy optical properties of polypropylene are a detriment to its use in thin films. To address this problem, as well as to improve physical properties and reduce material costs, we can orient the molecular chains by stretching the polymer film after it has left the extrusion die. There are two methods of orienting films, film blowing, shown in Fig. 11.6, and tentering, shown in Fig, 19.6. 

Polyolefins are well adapted to the mono-material concept talc-filled polypropylene and LFRT for structural parts, foamed polyethylene and polypropylene for damping, polypropy-lene/EPDM alloys or copolymers for skins. Some other functions need incompatible polymers with specific characteristics such as optical properties. Without claiming to be exhaustive, the other thermoplastic materials are ... 

For some operations, the chill roll method does not provide rapid enough cooling. In that case, a water-filled quench tank may be used for cooling and solidifying the plastic, as shown in Fig. 7.5. After solidification, the film is dried, trimmed, and rolled up. Drying may be accomplished by evaporation alone, or air jets, heated rolls, or radiant heat maybe used. The film characteristics are controlled by the die dimensions, extrusion rate, melt temperature, drawdown, and water temperature. This method used to be widely used for polyethylene and polypropylene, but is now much less common, since chill roll casting can provide better control over optical properties and thickness. 

Monika, P. Upadhyaya, N. Chand, Vi Kumar, Effect of poly lactic acid on morphological, mechanical, and optical properties of compatibilized polypropylene and high density polyethylene blend. Compos. Interfaces 21, 133-141 (2014)... 

The optical properties, clarity and gloss, are also improved and biaxially oriented polystyrene and polypropylene films are used for envelope windows and overwraps. Biaxially oriented polyvinylidene chloride film is also used for food packaging in view of its good mechanical and optical properties, but for economic reasons it is only used if its low permeability to gases, especially oxygen, is required. The electrical properties are improved by biaxial orientation and the applications of polyester, polycarbonate and polypropylene films in capacitors are expected to show a rapid growth. In these electrical applications crystalline films are always annealed in order to improve the dimensional heat stability. 

Polypropylene/polyethylene, PP/LDPE, blends were compatibilized by addition of 2-22 wt% EPR. Blending was done in two stages, curing EPR before the second part of PP was added. The resulting materials had good mechanical, low-temperature impact, and optical properties... 

Posudiyevskii, O. Yu., Myasnikova, I. G., and Chuiko, A. A., Optical properties of the polypropylene surface modified by implantation of fluorine ions (in Russian), Dokl. Akad. Nauk SSSR, 319, 196-199 (1991). 

In order to rival current synthetic polymers used in packaging, such as polyethylene (PE), polypropylene (PP) or polystyrene (PS) for example, PHAs suite of both physical and chemical properties need to be comparable (Figure 8.5). Here, we describe the various mechanical, thermal and optical properties afforded by PHA and how they compare to their synthetic counterparts. Table 8.4 provides an example of both tensile and thermal properties for a variety of commercially available PHAs. 

Radwen [62] investigated the effect of electron beam irradiation in the optical properties of polypropylene. 

There is, however, another aspect of the chirality of isotactic polymers, which is associated with the helical form of isotactic polypropylene first observed in the X-ray diffraction experiments conducted in Milan by the Natta group. In this manner, Natta discovered the reason for the crystalline properties of this polymer synthesized from the catalyst developed by Karl Ziegler. But, in a sample of isotactic polypropylene, or other isotactic polymers arising from vinyl monomers, both left- and right-handed helical conformations are present so that no chiral optical property is observed. Each crystalline state in a sample of isotactic polypropylene is a racemic mixture of helical forms. 

There is more to the story of isotactic polypropylene arising from Piero Pino s interest in answering the following question Does the helical property of isotactic polypropylene in the crystalline regions of the sample extend into the amorphous regions, as in the melted state Pino decided to address this question by observing the possibility of chiral optical properties in structural variatiOTis of polypropylene. 

Menyhard A, Gahleitner M, Varga J, Bernreeitner K, Jaaskelainen P, 0ysaed H, Pukanszky B (2009) The influence of nucleus density on optical properties in nucleated isotactie polypropylene. Eur Polym J 45 3138-3148... 

Chapter 5 discusses in detail the current application of recycled PET. In particular, the applications of recycled PET are discussed in the fields of food packaging, construction, textile industry, injection moulding and other manufacturing processes, wood-plastic composites and so on. On the other hand. Chapter 6 describes the optical properties of polyolefins upon recycling. Optical properties of different plastics play a key role in packaging applications, so this chapter primarily focuses on the different structural aspects and properties of isotactic polypropylene. 

When a molded material contacts a strongly oxidizing medium, such as nitric acid, sulfuric acid, chlorine, bromine, and ozone, oxidative attack has to be expected. Table 5.68 shows the influence of chlorine on polyethylene resistance. Polymers with double bonds or with tertiary bound hydrogen atoms, such as polypropylene, are particularly prone to oxidation. Degradation due to oxidizing substances causes significant changes in mechanical, electrical, and optical properties. 

Borstar polypropylene random copolymers are characterized by excellent optical properties. The product portfolio also includes specialty grades for pressure pipe applications and copolymers with very low seal initiation temperatures. 

More recently, (+)-l,2-diethylpropane, a model diether for the repeating unit of propylene oxide, was prepared by Furukawa et al [101,102] and its behavior in solution regarding ORD and NMR was compared with those of the polymer. It was found that the model compound and polypropylene oxide show essentially the same optical properties in solution. By using the Brewster model of optical activity, it was concluded that the sol-vatation of the polymer may well modify the polarizability of the OA species so as to cause changes in the order of the polarizability of four atoms directly attached to the asymmetric carbon. 

---