Poly olefin s

Most practical uses of propylene polymer compositions require that the composition be stabilized with an acid scavenger. Typically, propylene polymers, which have been formed using catalysts containing halides, require some functionality of an acid scavenger to stabilize the polymer formulation against corrosivity for long-term uses (3). 

Zinc stearate and zinc oxide have been proposed as acid scavengers for poly(olefin)s (4). A particularly preferred acid scavenger comprises a mixture of aluminum hydroxide, zinc carbonate and zinc hydroxide (ZHT-4D, Kyowa) (5). Other acid scavengers are hydrotalcites and amorphous basic aluminum magnesium carbonates (6). 

In poly(olefin)s, fluoroelastomers are added sometimes as processing aids. It is believed that the fluoroelastomer and acid scavenger may have an unexpected effect as they modify the blocking and friction properties of the polymer synergistically (4). 

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The disadvantages of all biochemical routes is the lack of variable tacticity in the polymer and, even more important, the need for time-consuming purification. PHB materials of feasible properties are only achieved with high production costs. In the 1990s, ICl sold a copolymer of 3-HB and 3-HV (BIOPOL) for about 10-20 /kg whereas the price of PP was less than 2 /kg. Therefore, a fermentative synthesis is feasible for smaller applications but not cannot compete with packaging materials such as poly(olefin)s [43 5] (Fig. 10). 

LDPE), polypropylene (PP), poly(vinyl chloride) (PVC), and polyethylene tere-phthalate (PET) [48], completely new areas of application are preferred in which biodegradability is required for admission, such as applications in the medical field [50, 51]. The reason for this is obvious. When new materials enter the market, they are in competition with aheady established materials. In the case of PUB, due to its temperature stability, a competition with poly(olefin)s arises for all applications in which biodegradabUity is not required by law (Fig. 12). 

PVAc, PVA and PVB homopolymers as well as the different copolymers mentioned above all have a similar chemical motif in common. They exhibit an all carbon-carbon single bond backbone, which needs to be broken at some point in a potential biodegradation mechanism. With respect to the backbone, poly(vinyl ester)s are closely related to poly(olefin)s, poly(styrene)s and poly(acrylate)s. These three are known not to be biodegradable. Instead, they usually decompose by the impact of UV radiation, oxidation and hydrolysis reactions, which are not considered to be biological degradation. 

Materials. Poly (olefin sulfone)s were prepared by copolymerization of liquid mixtures of sulfur dioxide and the appropriate olefin using tert.-butyl hydroperoxide as initiator in the temperature range from —80 to 0°C. The poly (amino acid)s were obtained from Sigma Chemical Co. and used without further purification. The poly (olefin) s were provided by Mr. O. Delatycki and Dr. T. N. Bowmer and were prepared under controlled conditions. The aromatic polysulfones were prepared and purified by Mr. J. Hedrick. The purity of all polymers was checked by H and 13C NMR. 

The distribution of volatile products of low molar mass from the irradiation of poly (olefin) s is strongly dependent on the nature of substituents (short-chain branches) on the backbone chain. Hydrogen is the main volatile product with smaller quantities of alkanes and alkenes. 

The high specificity of elimination of alkyl side branches from poly (olefin) s is attributed to (1) enhanced scission of C-C bonds at tertiary carbon atoms, reflecting their lower bond energies, and (2) a cage effect which produces geminate recombination of many of the main-chain cleavages, whereas the mobility of fragments of low molar mass enables them to escape. 

Typically COC has a higher modulus than high density polyethylene) (HDPE) or poly(propylene) (PP). Thus, it is the more brittle than ordinary poly(olefine)s. 

Also within this category of application is the field of radiation grafting onto pre-existing polymeric substrates. E-beam or gamma sources can be used to initiate grafting onto a range of materials, for example poly(olefin)s, fluoropolymers, and cellulosics. The biocompatibility of poly(olefin)s can be greatly... 

PPAs are typically low in ductility as reflected by generally low values for elongation at break and the lack of significant extensibility in tensile testing. The ductility and rigidity can be improved by blending with poly(olefine)s. 

In general, the two polymer phases are incompatible. For this reason, a compatibilizer must be added to the blends in order to achieve good dispersing and mutual anchoring of the two polymer phases. Suitable compatibilizers are carboxylated or anhydride grafted poly(olefin)s. Such compatibilizers are generally commercially available, e.g.. Polybond , Exxelor , Hostamont , Admer , Orevac , Epolene , and Hostaprime [13]. 

FIG. 7 The dependence of the glass temperature of poly-(olefin)s on the mass/ flexible bond ratio of the monomeric units. 

Intumescent flame retardants are of interest for poly(propylene) and poly(olefin)s in general. In the case of fire, they develop very low smoke and toxic gases. Further, they reduce the notorious dripping during burning (9). 

A preferred process of adding the zinc salt to the poly(ester) is to make a masterbatch of the zinc salt of an organic acid in a polymer base material such as a poly(ester) or a poly(olefin). Suitable poly(olefin)s include poly(propylene) and LLDPE, or HOPE. The masterbatch is mixed in the course of the extrusion operation into the desired poly (ester). The concentration of zinc salt in the master-batch may range from 5-30%. 

Bis-(3,4-dimethylbenzylidene) sorbitol Disodium[2.2.1]heptanebicyclodicarboxylate Aluminum 2,2 -methylene-bis(4,6-di-tert-butylphenyl) phosphate Semi-crystalline branched or coupled poly(olefin)s (9)... 

Dibenzylidene sorbitol exists in the form of fibrils and usually acts as an effective nucleating agent to facilitate crystallization of poly-(olefin)s during manufacturing (12). In particular, when the dibenzylidene sorbitol concentration reaches a critical value, the fibrils will self-organize into a three-dimensional network when there is a decrease of temperature, but before crystallization takes place. The network of the fibrils may facilitate the subsequent process of nu-cleation and crystallization growth. An oriented deformation of the dibenzylidene sorbitol network could act as a template for anisotropic crystallization of PP, which then results in a high lamellar orientation level. 

Not all polymers are prone to hydrolytic degradation. For example the backbone of poly(olefin)s is essentially inert to hydrolytic degradation. However, poly(ester)s and poly(amide)s are more or less sensitive to hydrolytic degradation. 

Acid scavengers are also addressed as acid absorbers, antacids, or still less precisely as costabilizers. The addition of acid scavengers is necessary because catalyst residues from processing and manufacture may contribute to imdesired properties. This does not necessarily cause a diminished stability of the polymeric base material. Instead, residues from Ziegler-Natta catalysts in poly(olefine)s may contain traces of halogen that could cause corrosion reactions to metals that are in contact with the polymer. 

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