Polypropylene Unsaturation

The types of unsaturation that can occur in polypropylene are listed next  

Identification of the free radicals produced when polymers are irradiated (usually by gamma-radiation from °Co or by fast electrons from an electron accelerator tube) can sometimes give vital information regarding structural features, saturated and unsaturated, of the original polymer. 

In the spectrum of amorphous polypropylene irradiated with a dosage of 4000 Mrad at -196 °C and measured at -130 °C, in addition to the band at 6.08 pm, a weaker band appears with a maximum near 6.00 pm, possibly due to internal bonds  

When the spectrum of the specimen is recorded after it is heated to +25 °C, this maximum disappears, leaving only a shoulder on the strong band at 6.08 pm. The extinction coefficient [65] of the hand at 6.00 pm is less than that of the 6.08 pm band by a factor of 6.7. Supplementary evidence of the formation of internal double bonds in irradiated polypropylene is provided by the presence in the spectrum of bands in the 12.27-11.69 region. In this region lie bands due to deformation vibration of CH at double bonds in groups, existing in various conformations [43]. The appearance of bands at 12.27 pm and 11.69 pm in the spectrum of irradiated polypropylene can be regarded as an indication of the formation of internal double bonds in the polymer  

In the latter case, D6.08 is the sum of the optical densities of the vinylidene and vinyl absorption bands in this region. An optical density ratio for these bands of approximately this value was found (1.75 to 3.3) for the products of thermal degradation of polypropylene. It is seen that only in the case of amorphous polypropylene irradiated with gamma-radiation from Co is the ratio (D11.23 + D10.99)/D6.08 close to the value calculated from the extinction coefficients of these bands. In the spectra of irradiated isotactic polypropylene, the intensity of the 6.08 pm band is greater than would be expected if only vibration of terminal double bonds contributes to absorption in this region. This increase in absorption in the 6.08-pm region can be related to absorption by the internal double bond in the allyl radical, the vibrational frequency of which is lowered by conjugation of the Jt-electrons of the double bond 

The appearance of bands at 8.15 and 8.55cm (12.27 and 11.69 pm) in the spectrum of irradiated polypropylene can be regarded as an indication of the formation of internal double bonds in the polymer. 

---

Eversorb 75 is a benzotriazole type UV absorber. It has a high and broad absorption in the wavelength of 300-400 nm. Eversorb 75 is particularly effective in polyethylene, polypropylene, unsaturated polyester and styrenic polymers. 

Polypropylene polymerized with triethyl aluminum and titanium trichloride has been found to contain various kinds of chain ends. Both terminal vinylidene unsaturation and aluminum-bound chain ends have been identified. Propose two termination reactions which can account for these observations. Do the termination reactions allow any discrimination between the monometallic and bimetallic propagation mechanisms ... 

The use of TAG as a curing agent continues to grow for polyolefins and olefin copolymer plastics and mbbers. Examples include polyethylene (109), chlorosulfonated polyethylene (110), polypropylene (111), ethylene—vinyl acetate (112), ethylene—propylene copolymer (113), acrylonitrile copolymers (114), and methylstyrene polymers (115). In ethylene—propylene copolymer mbber compositions. TAG has been used for injection molding of fenders (116). Unsaturated elastomers, such as EPDM, cross link with TAG by hydrogen abstraction and addition to double bonds in the presence of peroxyketal catalysts (117) (see Elastol rs, synthetic). 

Their physieal properties are essentially those of the alkanes. It is the unsaturated linkages that dominate the ehemistry and the main reaetion is one of addition (e.g. hydrogen, halogen, and hydrogen halides) aeross the double bond to produee saturated eompounds. This reaetivity is utilized in the manufaeture of long-ehain polymers, e.g. polyethylene and polypropylene. 

Poly(ethylene terephtlhalate) Phenol-formaldehyde Polyimide Polyisobutylene Poly(methyl methacrylate), acrylic Poly-4-methylpentene-1 Polyoxymethylene polyformaldehyde, acetal Polypropylene Polyphenylene ether Polyphenylene oxide Poly(phenylene sulphide) Poly(phenylene sulphone) Polystyrene Polysulfone Polytetrafluoroethylene Polyurethane Poly(vinyl acetate) Poly(vinyl alcohol) Poly(vinyl butyral) Poly(vinyl chloride) Poly(vinylidene chloride) Poly(vinylidene fluoride) Poly(vinyl formal) Polyvinylcarbazole Styrene Acrylonitrile Styrene butadiene rubber Styrene-butadiene-styrene Urea-formaldehyde Unsaturated polyester... 

The surface energy of fibers is closely related to the hydrophilicity of the fiber [38]. Some investigations are concerned with methods to decrease hydrophilicity. The modification, of wood cellulose fibers with stearic acid [43] hydrophobizes those fibers and improves their dispersion in polypropylene. As can be observed in jute-reinforced unsaturated polyester resin composites, treatment with polyvinylacetate increases the mechanical properties [24] and moisture repellency. 

Polyolefins Plastics such as polyethylene (PE), polypropylene (PP), and polybutylene (PB) that are derived from unsaturated hydrocarbons (also called olefins). 

One such reported example is the synthesis of polypropylene-6-polymethyl-methacrylate (PP-6-PMMA) copolymers utilizing metallocene catalysis and the borane chemistry. In the initial step, PP with chain-end olefinic unsaturations was prepared using metallocene catalysts such as Et(Ind)2ZrCl2/MAO. The unsaturation sites were then hydroborated by 9-borabicyclo[3.3.1]nonane (9-BBN) to produce borane-terminated PP (43) (Fig. 30), which was selectively oxidized and interconverted to a... 

Figure 30 The hydroboration strategy of chain end olefinic unsaturation in polypropylene with 9-BBN for further conversion into block copolymers via polymer radicals. (Adapted from refs. 66 and 67.)...

Figure 3 Comparison of chemiluminescence runs from saturated and unsaturated hydrocarbon polymers having tertiary carbons (polypropylene, polyisoprene) in the main chain.

P.Y.110 lends color to polystyrene and styrene containing plastics. It is a suitable candidate for unsaturated polyester and other cast resins, as well as for polyurethane. P.Y.110 is used to an appreciable extent in polypropylene spin dyeing, it is very lightfast in this medium. It is utilized in polyacrylonitrile spin dyeing and sometimes also in polyamide. Its fastness properties, however, especially its lightfastness, do not meet special application conditions (Sec. 1.8.3.8). 

P.B.15 3, like stabilized a-Copper Phthalocyanine Blue, markedly affects the hardening of unsaturated polyester cast resins. The list of applications also includes PUR foam materials, office articles, such as colored pencils, wax crayons, and water colors, as well as spin dyeing of polypropylene, polyacrylonitrile, secondary acetate, polyamide, polyester, and viscose. Used in polyester spin dyeing, P.B.15 3 satisfies the thermal requirements of the condensation process (Sec. 1.8.3.8). 1/3 and 1/25 SD samples equal step 7-8 on the Blue Scale for lightfastness. Textile fastnesses, such as stability to wet and dry crocking are perfect. 

A line of research that has aroused much interest in recent years is the study of head-to-head, tail-to-tail polymers (96-98). Their direct synthesis has little likelihood of being successffil as head-to-tail sequences usually predominate in vinyl polymerization. One possibility for their preparation is through the chemical modification of suitable preformed polymers. In the case of the head-to-head, tail-to-tail polypropylene, different stereoisomeric forms have been isolated, depending on the method of preparation. In the general scheme, the precursor is an unsaturated polymer obtained by polymerization of the disubsti-tuted butadiene (2,3-dimethylbutadiene or 2,4-hexadiene) then, by chemical or catalytic reduction, this polymer is converted into the desired polypropylene, whose stmcture can then be examined by NMR spectra. Head-to-head, tail-to-... 

---