Cooling comonomers

The crystallinity in PET soft drink bottles is about 25%. Because a more crystalline state is normal for PET, the amorphous content is increased intentionally by copolymerization and rapid cooling for the molten PET from the melt to a temperature below the glass transition temperature. Companies which perform high-speed blow molding of PET prefer PET resins made with small amounts of glycol and diacid comonomers. 

Fig. 12 Cooling (solid lines) and heating (dotted and dashed lines) crystallinity curves of random copolymers with variable comonomer mole fractions as denoted near the curves. The dashed lines start from the reduced temperature of 2 and meet the dotted curves at high temperatures [52]... 

Fig. 13 Cooling (solid line) and heating (dashed lines) curves of crystallinity and averaged length of crystallized sequences for slightly alternating copolymers with a comonomer mole fraction 0.24. The crystallized sequences are defined as the monomer sequences more than half of whose bonds are in crystalline states [124]...

Fig. 14 Snapshots of random copolymers with variable comonomer mole fractions at the reduced temperature of 1 in the cooling process of Fig. 12. a-f Comonomer contents of 0, 0.06, 0.12, 0.24, 0.36, and 0.44, respectively. Polymer bonds are drawn in cylinders and the bonds containing comonomers are shown in double thickness [52]...

Fig. 15 Cooling curves of crystallinity (solid line) and demixing parameter of comonomers (dashed line). The latter is defined as the mean fraction of neighboring sites occupied by other comonomers around each comonomer. The cooling program is a stepwise increase of Ep/(k T) from zero with a step length of 0.002 and a step period of 300 Monte Carlo cycles, a The slightly alternating copolymer with a comonomer mole fraction 0.36 b the heterogeneous copolymer with a comonomer mole fraction of 0.36 [52]...

The level of short-chain (SCB) and long-chain (LCB) branches control the solid resin density of a PE resin. For example, the level of SCB is controlled by the amount of alpha olefin comonomer incorporated into LLDPE resin as a pendant group. The random positioning of the pendant groups disrupts the crystailization process when the polymer is cooled from the molten state, causing the level of crystallinity to decrease with increasing amounts of alpha olefin comonomer. 

One of the drawbacks associated especially with slurry and solution CSTR processes is the necessity of removing the solvent or diluent in a post-production step. In a gas phase reactor the polymerisation takes place in a fluidised bed of polymer particles. Inert gas or gas mixture is used for fluidisation. The gas flow is circulated through the polymer bed and a heat-ex-changer in order to remove the polymerisation heat. Gaseous ethylene and comonomer are fed into the fluidisation gas line of the reactor, and a supported catalyst is added directly to the fluidised bed (Fig. 7). Polymerisation occurs at a pressure of about 20-25 bar and a temperature of about 75-110 °C. The polymer is recovered as a solid powder which is, however, usually pelletised. Due to the limited cooling capacity of the fluidising gas, reactor... 

During the semi-continuous polymerization, 4-5 small samples were withdrawn from the polymerization for the determination of the comonomer and copolymer composition. A few drops of the sample latex were mixed with hydroquinone, cooled in ice, and subjected to GC analysis to determine the amounts of unreacted monomer. The rest of the sample (5-8 ml) was poured into mixed solvent of ispropanol/hexane (45/55) containing hydroquinone, and the precipitated polymer, after it was washed with hexane, was dried in a vacuum oven at 45°C for more than 5 hours. A certain amount of the dried polymer was dissolved in dimethyl formamide (DMF), and titrated for the carboxyl content with NaOH solution using phenolphthalein as the indicator. 

Description Ethylene, initiator and, if applicable, comonomers are fed to the process and compressed to pressures up to 3,100 bar before entering the tubular reactor. In the TS mode, the complete feed enters the reactor at the inlet after the preheater in the TM mode, part of the gas is cooled and quenches the reactor contents at various points of injection. 

The following protocols (6-10) describe the synthesis of some cholesterol-based acrylates and their photopolymerization in an aligned cholesteric phase. The protocols utilize a modification of a system previously described by Shannon. 5 6 ip ie absence of a diacrylate comonomer, the cholesteric phase produced initially on copolymerization is not stable and reverts to a smectic phase on a single cycle of heating and cooling. In the presence of the diacrylate the first-formed phase is stable. This is one example of how crosslinking can stabilise the liquid crystal phase in liquid crystalline elastomers, others include, the so-called, polymer-stabilized liquid crystals and those described in the later protocols. 

In other words, when a homogeneous polyethylene solution was cooled at a constant rate, the point of beginning crystallization was reached. This point was indicated by the first visual turbidity. At all concentrations, homopolymer A had a point of beginning crystallization about 10°C higher than that of copolymer B. This finding seemed reasonable since the crystallization temperature depends on the comonomer content and on the degree of short-chain branching of the polyethylene. From the curve we concluded that the temperature at which styrene diffused into LDPE A was about 10°C above that for diffusion into LDPE B at a comparable rate of diffusion. 

Phosphine-derivatised poly(4-/i r/-butylstyrene) has been prepared for use as a soluble support in homogeneous catalysis.It was used in a monophasic medium and separation of the catalysts after reaction was effected either by cooling- or water-induced phase separation. The support was prepared by co-polymerisation of /i r/-butylstyrene with a phosphine oxide-containing styrene monomer (Scheme 19) A small quantity of a methyl red-labelled comonomer was also added to act as a colorometric tag to facilitate studies of the extent of separation and recycling of the polymeric material. The phosphine oxide was reduced to the free phosphine after the polymerisation step was complete. 

After less than 10% conversion the reaction tubes were cooled and the vacuum was released. The viscous solution was then precipitated in excess of dry hexane. The polymers were further purified by repeated dissolution and precipitation from THF into n-hexane so as to remove the unreacted comonomers and initiator species. 

Crystalline unit cell parameters depend on crystallite thickness. The comonomer amount, comonomer type, and crystallization conditions determine the crystallite thickness in ethylene copolymers. The major cause of lattice expansion in ethylene copolymers is due to decrease in lamellae thickness by exclusion of branch points from the lamellar crystals coupled with surface stress on thin lamellae (see references 24 and 25 for details). The table below is for butene-1 mLLDPE (My, = 122,000, Mw/M = 2), crystallized from the melt at a cooling rate of 7°Cmin . ... 

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