Poly- 4-methylpent-l-ene

Factors affecting laboratory polymerisation of the monomer have been discussed and these indicate that a Ziegler-Natta catalyst system of violet TiCl3 and diethyl aluminium chloride should be used to react the monomer in a hydrocarbon diluent at atmospheric pressure and at 30-60°C. One of the aims is to get a relatively coarse slurry from which may be washed foreign material such as catalyst residues, using for example methyl alcohol. For commercial materials these washed polymers are then dried and compounded with an antioxidant and if required other additives such as pigments. 

The isotactic form is the only polymer of commercial importance. An unusual feature is that bulk polymer is transparent because the molecular chain is only very slightly birefringent. A second unusual feature is that the crystalline density and the amorphous density are very similar. The transparency is further enhanced by nucleation giving finer texture, and by balancing crystalline and amorphous densities even more closely, by copolymerization. The monomer is obtained by the dimerization of propylene. 

P4MP is suitable for laboratory ware because it has good chemical resistance, transparency and high-temperature performance. For medical 

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Industrial equipment is a continuing area of development for plastics. Pipes, pumps, valves and sight glasses, made from such materials as PVC, PTFE and poly-4-methylpent-l-ene, have become well established on account of their corrosion resistance. The nylons are used for such diverse applications as mine conveyor belts and main drive gears for knitting machines and paper-making equipment. These and other materials are widely used where such features as toughness, abrasion resistance, corrosion resistance, non-stick properties, electrical insulation capability and transparency are of importance. 

There are thus no solvents at room temperature for polyethylene, polypropylene, poly-4 methylpent-l-ene, polyacetals and polytetrafluoroethylene. However, as the temperature is raised and approaches F , the FAS term becomes greater than AH and appropriate solvents become effective. Swelling will, however, occur in the amorphous zones of the polymer in the presence of solvents of similar solubility parameter, even at temperatures well below T. ... 

A great attention was paid to grafting of light stabilizers onto polyolefins. 2-Hydroxy-4-methacryloyloxybenzophenone was grafted onto LDPE, HDPE, PP, poly(4-methylpent-l-ene) or ABS in extruders in the presence of peroxides or onto LDPE or PP in the melt without peroxide. Grafting on PS was very efficient. 

There are a number of occasions where a transparent plastics material which can be used at temperatures of up to 150°C is required and in spite of its relatively high cost, low impact strength and poor aging properties poly-(4-methylpent-l-ene) is often the answer. Like poly(vinyl chloride) and polypropylene, P4MP1 is useless without stabilisation and as with the other two materials it may be expected that continuous improvement in stabilising antioxidant systems can be expected. 

Evidently the crystallites in poly (4-methylpent-l-ene) are permeable to oxygen. The crystalline and amorphous forms of the polymer have nearly the same densities and oxidation patterns at 100°C (see Fig. 2) and consume tenfold more oxygen than the linear polyethylene. 

Figure 2. Exhaustive oxidation of molded (O) and solution-crystallized linear polyethylene and poly(4-methylpent-l-ene)...

The fluorescence and phosphorescence excitation and emission spectra of commercial polypropylene and poly(4-methylpent-l-ene) are examined using a fully compensated spectrofluorimeter. The excitation spectra of the polymers are compared with the absorption spectra of model chromo-phores of those believed to be present in the polymers. The fluorescence emission is associated primarily with the presence of enone and the phosphorescence is associated with dienone impurity chromophoric units. Bromination of cold hexane extracts of the polymers reduces significantly the intensity of the fluorescence confirming the presence of ethylenic unsaturation. The behavior of the luminescent enone and dienone groups during irradiation under sunlight-simulated conditions is examined also. Possible mechanisms for the participation of these chromophoric units in the photooxidation of the polymers are discussed. 

In this paper we report on the identification of the luminescent impurity carbonyl species in two of the most light-sensitive polyolefins, polypropylene and poly(4-methylpent-l-ene) and examine the behavior of these groups during irradiation under sunlight-simulated conditions. 

Materials. Commercial polypropylene and poly(4-methylpent-l-ene) powders containing no commercial additives were supplied by I.C.I. (Plastics Division) Ltd. The powders were vacuum pressed into film of 200-/x thickness at 190° and 280°C respectively, for 1 min. The n-hexane was of spectroscopic quality. 

Polymer Luminescence Spectra. Figure 1 shows typical fluorescence and phosphorescence excitation and emission spectra obtained from commercial polypropylene film (or powder). Poly(4-methylpent-l-ene) exhibits similar spectra to those of polypropylene. The excitation spectrum for the fluorescence has two distinct maxima at 230 and 285 nm while that of the phosphorescence has only one distinct maximum at 270 nm with rather weak and diffuse structure above 300 nm. It is clear from these results that the fluorescent and phosphorescent chromophoric species cannot be the same. This, of course, does not rule out the fact that both may arise from carbonyl emitting species, as will be shown later, since these chromophoric groups when linked to ethylenic unsaturation can have quite distinct absorption (14) and emission spectra (15,16,17). 

A further interesting feature of the phosphorescence emission from the polymers is that it is long-lived (5). For the polypropylene and poly(4-methylpent-l-ene) samples examined in this study the emission lifetimes were 1.2 and 0.7 sec, respectively. Long-lived phosphorescence... 

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