Plasticization, internal

J. Troit2sch, International Plastics Flammability Handbook, Hanser Pubhshers, Munich, Germany, 1990. 

H. Saechtiing, International Plastics Handbook, Hanser Vedag, Munich, Germany, 1983, pp. 156,162. 

Internal Plasticizers. There has been much dedicated work on the possibiUty of internally plasticized PVC. However, in achieving this by copolymerization significant problems exist (/) the affinity of the growing polymer chain for vinyl chloride rather than a comonomer implies that the incorporation of a comonomer into the chain requites significant pressure (2) since the use of recovered monomer in PVC production is standard practice, contamination of vinyl chloride with comonomer in this respect creates additional problems and (J) the increasing complexity of the reaction can lead to longer reaction times and hence increased costs. Thus, since standard external plasticizers are relatively cheap they are normally preferred. 

Solvation—Desolvation Equilibrium. From the observation of migration of plasticizer from plasticized polymers it is clear that plasticizer molecules, or at least some of them, are not bound permanently to the polymer as iu an internally plasticized resia, but rather an exchange—equiHbrium mechanism is present. This implies that there is no stoichiometric relationship between polymer and plasticizer levels, although some quasi-stoichiometric relationships appear to exist (3,4). This idea is extended later ia the discussion of specific iateractions. 

W. E. Brown, Proceedingsfrom International Plastics Congress, 1966, N.V. t Raedthuys, Utrecht, Netherlands, 1967. 

M. J. Howard, ed.. The International Plastics Selector, 1977, International Plastics Selector., Inc. of Codura PubUcations, La JoUa, Calif., 1977, p. 

Combinations of these strategies might be considered. For example, in many cases the presence of an external conductive layer on a plastic pipe will not by itself eliminate puncturing of the internal plastic wall, and if the layer does not provide containment it will not prevent external leakage. 

Use internally, plastic-coated drillpipe at all times. The coating must be holiday-free to be effective. 

Internal plastic thread The strength of plastic threads is limited, and when molded in a product involving either an unscrewing device or a rounded shape of thread similar to bottle-cap threads, they can be stripped from the core. Screw threads, when needed, should be of the coarse type and have the outside of the thread rounded so as not to present a sharp V to the plastic that can produce a notch effect. 

International plastics selector , 9th edition, Int. Plastics Selector, San Diego, CA (1987). Thermoplastics, thermosets, elastomers, and key property areas critical to plastics are extensively specification defined. 

J. Troitzsch, International Plastics Flammability Handbook Principles, Regulations, Testing and Approval, 2nd ed., Hanser, New York, 1990. 

Applications Although Soxtec combines the best qualities of reflux and Soxhlet extractions up to now fairly little evidence has been reported concerning the efficacy of this system for polymer and rubber analysis. Nevertheless, it appears that oligomers and other reaction residues, softeners, antioxidants (e.g. BHT) and several other additives used to modify polymers are easily extracted from PVC, PP, PE, PS, rubber and many other polymeric materials. Also, some leading international plastic, rubber and packaging companies have made Soxtec an integral part of their quality control routines. Some application examples where Soxtec has proved successful are [148] ... 

The increase in the length of the side chain results normally in an internal plasticization effect caused by a lower polarity of the main chain and an increase in the configurational entropy. Both effects result in a lower activation energy of segmental motion and consequently a lower glass transition temperature. The modification of PPO with myristoyl chloride offers the best example. No side chain crystallization was detected by DSC for these polymers. 

To facilitate and accelerate folding and crystallization of polymer chains, internal plasticizers are often added to PET to serve as crystallation promoters. Such additives are usually based on poly(ether ester)s. These plasticizers are liquids that are typically added at levels of 2-4 wt%. They reduce cycle time in injection moulding operations by increasing the rate of crystalline formation. They also plasticize the resin and act as processing aids by virtue of their lubricating action in the melt. On a molecular level, these plasticizers reduce the intermolecular... 

Copolymers. Mixtures of two or more different bifunctional monomers can undergo additional polymerization to form copolymers. Why copolymerize Well, polymers have different properties that depend on their composition, molecular weight, branching, crystallinity, etc. Many copolymers have been developed to combine the best features of each monomer. For example, polystyrene is low cost and clear, but it is also brittle with no toughness. It needs internal plasticization. By copolymerizing styrene with a small amount of acrylonitrile or butadiene, the impact and toughness properties are dramatically improved. 

It is possible that either Me has increased by degradation of the network structure or the resin is internally plasticized by free chain ends. If Me has increased, then the modulus in the rubbery plateau region for irradiated specimens should be less than that of a control. As discussed above, E (Tg+40) decreases up to a dose of 5000 Mrads. Between 5000 and 10,000 Mrads, E (Tg+40) increases but remains 6% below the control. For the 73/27 and 80/20 samples (10,000 Mrads) which have been sorbed/desorbed, E (Tg+40) is 18.5% greater than the control. 

Copolymerization of Styrene with Methyl Acrylate (Internal Plasticization)... 

To investigate the internal plasticization of polystyrene (Tg = 105 C) by insertion of methyl acrylate (Tg = 4°C),the samples are run on a DSC.Therefore, approximately 15 mg of each of the well dried polymers are weighed into small aluminum pans and measured by two heat-cool runs in a DSC apparatus.The glass transition is found as a characteristic jump in the heat capacity in the system.The glass transition temperature is evaluated after the second heating from the DSC plot. 

Seow, C. C., Thevamalar, K. (1993). Internal plasticization of granular rice starch by hydroxypropylation effects on phase transitions associated with gelatinization. Starch, 45, 85-88. 

The Tg values may also be reduced by random copolymerization with a monomer which produces more-flexible polymers. This lowering of Tg values by copolymerization is sometimes called internal plasticization. 

The phosphate groups impart several unique characteristics to this polymer series. It makes the polymer more soluble in common organic solvents. It also acts as an internal plasticizer, making the polymer more flexible. Finally the phosphate groups impart hydrophilicity to the polymer, thus giving the surface lower fouling characteristics via reduced protein adsorption. 

Internal Plasticizers. These are actually a part of the polymer molecule-e.g., a second monomer is copolymerized into the polymer structure, thereby making it less ordered, and therefore, more difficult for the chains to fit closely together. This softens the polymer-i.e., lowers the glass temperature (T0) or the modulus. Usually the internal plasticizer is a monomer whose polymer has good low temperature properties. A few representative values of Tg or 7 (brittle temperature) for homopolymers and copolymers are shown in Table I ... 

Internally plasticized systems consisting of simple random copolymers, designed for use in flexible plastic articles, generally have an unsatisfactorily narrow use temperature range, since they soften more sharply than analogous externally plasticized systems or polyblends (mixtures of two or more polymers). 

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