Internal plasticization effect

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. 

Copolymers, as the name implies, are produced from the polymerization of two different materials. Probably one of the most widely used copolymer emulsion adhesives is that based on vinyl acetate ethylenes, commonly referred to as VAEs (see Ethylene vinylacetate copolymers). These are produced by the copolymerization of vinyl acetate and 10-20% ethylene, the resulting polymer base possessing some superior properties over the PVA-based emulsions referred to above. These superior properties relate principally to the increased inherent flexibility of the dry VAE film due to the internal plasticization effect of the ethylene component in the polymer, which enhances adhesion to many difficult surfaces. There are, however, a number of other polymers and copolymers that are used as the formulating basis for alternative specialized emulsion adhesive systems. 

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. 

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. 

Internal plasticizing demands a chemical relationship between the components which constitute the product. Therefore, good effects can be expected from copolymers of styrene and isobutylene, ethylene, or diolefins like butadiene or isoprene. Internal plasticizing of PVC can be effected by copolymerizing vinyl chloride with acrylates of higher alcohols or maleates and fumarates. The important ABS products are internal copolymers of butadiene, styrene, and acrylonitrile. The hardness of the unipolymers of styrene and acrylonitrile can be modified by butadiene which, as a unipolymer, gives soft, rubberlike products. As the copolymerization parameters of most monomers are known, it is relatively easy to choose the most suitable partner for the copolymerization. When the product of the r—values is l, there is an ideal copolymerization, because the relative reactivity of both monomers toward the radicals is the same. Styrene/butadiene, styrene/vinyl thiophene, and... 

In summary, our studies have show n that graft copolymers of PVN with PEO form homogeneous, rubbery materials. The properties of copolymers having low PEO content remain to be investigated to evaluate the use of PEO as an internal plasticizer. Also, the effect of the size of side chains will have to be considered. 

PLASTICIZERS. High-boiling solvents or softening agents, usually liquid, added to a polymer to facilitate processing or to increase flexibility or toughness, (Where these effects are achieved by chemical modification of die polymer molecule, e.g., through copolymerizadon, the resin is said to be internally plasticized. )... 

These results obtained can be interpreted, at least, in terms of the effect of external plasticization caused by the deposition of polystyrene within wood cell wall in addition to the insufficient internal plasticization previously provided by the acylation. 

There have been various attempts to obtain stable copolymers of vinyl chloride by using comonomers from which the desired stabilizing effect was to be expected on the basis of their structure. [We suggested some time ago that in analogy to internal plasticization, this method of stabilizing a polymer be called internal stabilization (4).]... 

All of the above factors come into play in determining the effect of pendant groups on Tg. An aromatic pendant group raises Tg while an aliphatic pendant group can act as an internal plasticizer and lower Tg. However, if the pendant group is long enough, it may crystallize and raise Tg. 

When copolymerizing VCM with vinyl esters it appears to be the combination of two competing effects which determines the latex stability. A stability increasing effect seems to arise from increasing the polarity of the polymer particle surface, and a stability decreasing effect from increasing the softness of the polymer particles by internal plasticization. 

A comparison of the extensive data sets available for LCCEs has recently produced the recognition that the thermal characteristics of cellulose esters are the result of an internal plasticization by methylene groups, for the most part (O Fig. 22). Whereas the highest plasticization effect is observed for C2 to C6 triesters, most LCCEs with substituents greater than hex-anoate experience a plasticization effect of ca. 2.5° C/CH2(wt.%). Plasticization with methylene groups is reduced by the presence of OH-groups, and by the formation of liquid crystalline phases [89]. 

Internal lubricants are added as part of the formulation during plastics processing. Depending on their compatibility with the resin they can have a more pronounced internal lubrication effect mainly interacting with the molecules of the polymer melt or they can have a more pronounced external effect, i.e. additionally reduce friction at the interface between processed plastic melt and metallic machinery parts [121, 151-153]. Lubricants in resin systems improve flow characteristics and reduce adhesion in the polymer melt. Added in very small quantities... 

Methylene (-CH2-) units in side groups generally cause "internal plasticization" and lower Tg. The only common exceptions to this rule are hydrocarbon polymers with very long side chains, where side chain crystallization and/or other nonbonded interactions between side groups may counter this effect, and cause a slight increase of Tg with increasing number of methylene units after a certain side chain length is exceeded. 

These results were obtained with electrical insulation type compounds, all formulated to equivalent initial modulus. These high-temperature conditions used to assess volatility effects are so severe that internally plasticized polymers can fail on property retention because of oxidative cleavage. 

It is generally observed that as longer spacer units are introduced, the Tg of the polymer is lowered by internal plasticization and the tendency for the more ordered smectic phase to develop is increased. A similar ordering effect is also encouraged by lengthening the alkyl tail unit (see Table 5.7). Both these phenomena reflect the known tendency for long side chain to order and eventually to crystallize, when sufficiently long, and this condition persists also in the liquid crystal state. 

Typically, rigid PVC formulations use about twice as much lubricant as semirigid and flexible formulations. This is because plasticizers act similar to internal lubricants as they interact with PVC, making it more mobile, and flexible. Lubricant was found to affect impact properties because these are controlled by fusion which is affected by lubricant type and concentration. Lubricant also had a plasticizing effect on polymer, which had tensile strength higher without lubricant. ... 

Use of this plasticizer, which is commercially available (Fyrolflex RDP) permits to obtain, non-fogging, flame retarded polyurethane foam. Incorporation of halide (preferably chlorine) in trialkyl plasticizer results in an ignition resistant, UV stable plasticizer. Effect of a plasticizer on heat stability of PVC, flexibility of plasticized material at room and low temperatures is usually balanced by the selection of a required proportion between aryl and alkyl components. Low temperature properties can be improved by alkylphettylation with special attention to isopropyl substituents. Also haze can be eliminated in PVC composition by use of alkylated derivatives (e.g., methylphosphonate). Matty efforts were made by international groups of specialists to analyze reasons for increased toxicity of some phosphates such as tricresyl and triphenyl phosphates. Their extensive findings are reported elsewhere. ... 

Figure 10.5. The effect of triethyl citrate concentration on tensile strength of internally plasticized cellulose diacetate. [Data from Seung-Hwan Lee Shiraishi N, J. Appl. Polym. Sci., 81, No.l, 5th July 2001, p.243-50.]...

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