General purpose plastics

Unplasticized. Decreases to 1.30-1.32, depending on the formulation used when plasticized. General purpose, not expanded. 

Figure 9. A linear polyester plasticizer. General-purpose polymeric plasticizers have molecular weights of about 2000.

These plasticizers can be further grouped in a number of ways one convenient distinction is into general purpose and speciality plasticizers. General purpose types include the three phthalates di-2-ethylhexyl phthalate (DEHP or DOP), di-isononyl phthalate (DINP) and di-isodecyl phthalates (DIDP). These are the esters of phthalic anhydride with the alcohols 2-ethylhexanol, iso-nonanol and isodeconal respectively, and they account for about 75% of plasticizer usage in Western Europe. Other phthalates are also manufactured, but find use more in applications where specific properties are required. 

Resistant to extraction by solvents and oils. Polymeric plasticizers are much more resistant to extraction by solvents and oils than most monomeric plasticizers. General purpose phthalates are particularly poor in resistance to solvents compared with polymeric plasticizers. Polymeric plasticizers provide very significant improvements in performance for applications such as hoses used in contact with solvents or oils. 

Laboratory tests indicated that gamma radiation treatment and cross-linking using triaHylcyanurate or acetylene produced a flexible recycled plastic from mixtures of polyethylene, polypropylene, general-purpose polystyrene, and high impact grade PS (62). 

Cjcolac Brand ABS—General Purpose Blow Molding Grades, Technical PubHcation SR-616, GE Plastics, Pittsfield, Mass., 1989. 

TrioctylPhosphate. Trioctyl phosphate [1806-54-8/, C24H 04P, has been employed as a specialty flame-retardant plasticizer for vinyl compositions where low temperature flexibHity is critical, eg, in military tarpaulins. It can be included in blends along with general-purpose plasticizers (qv) such as phthalate esters to improve low temperature flexibHity. 

Plasticizers. Monomeric (mol wt 250—450) plasticizers (qv) are predominantiy phthalate, adipate, sebacate, phosphate, or trimeUitate esters. Organic phthalate esters like dioctyl phthalate (DOP) are by far the most common plasticizers in flexible PVC. Phthalates are good general-purpose plasticizers which impart good physical and low temperature properties but lack permanence in hot or extractive service conditions and are therefore sometimes called migratory plasticizers. Polymeric plasticizers (mol wt up to 5000 or more) offer an improvement in nonmigratory permanence at a sacrifice in cost, low temperature properties, and processibiHty examples are ethylene vinyl acetate or nitrile polymers. 

The and C q iso-phthalates (DINP and DIDP) generally compete with DEHP as commodity general-purpose plasticizers. Other iso-phthalates are available at opposite ends of the carbon number range (eg, diisoheptyl phthalate (DIHP), C, and diisotridecyl phthalate (DTDP), but these serve more speciaUty markets. The Cg iso-phthalate, diisooctyl phthalate (DIOP), has also had traditional sales ia the commodity plasticizer markets where it is seen as an equivalent to DEHP. 

Adhesives. Poly(vinyl alcohol) is used as a component in a wide variety of general-purpose adhesives to bond ceUulosic materials, such as paper and paperboard, wood textiles, some metal foils, and porous ceramic surfaces, to each other. It is also an effective binder for pigments and other finely divided powders. Both fully and partially hydrolyzed grades are used. Sensitivity to water increases with decreasing degree of hydrolysis and the addition of plasticizer. Poly(vinyl alcohol) in many appHcations is employed as an additive to other polymer systems to improve the cohesive strength, film flexibiUty, moisture resistance, and other properties. It is incorporated into a wide variety of adhesives through its use as a protective coUoid in emulsion p olymerization. 

Plasticizers (qv) are usually present at lower concentrations compared to general-purpose mbber-based compounds, because of their volatility at typical ACM service temperatures and/or their partial extractabiflty by the aggressive fluids where acryflc elastomers are employed. Other additives are therefore required to improve processibiflty. These processiag aids act as lubricating agents and enhance the release characteristics of the acryflc compound and/or reduce compound viscosity. 

As the author pointed out in the first edition of this book, the likelihood of discovering new important general purpose materials was remote but special purpose materials could be expected to continue to be introduced. To date this prediction has proved correct and the 1960s saw the introduction of the polysulphones, the PPO-type materials, aromatic polyesters and polyamides, the ionomers and so on. In the 1970s the new plastics were even more specialised in their uses. On the other hand in the related fields of rubbers and fibres important new materials appeared, such as the aramid fibres and the various thermoplastic rubbers. Indeed the division between rubbers and plastics became more difficult to draw, with rubbery materials being handled on standard thermoplastics-processing equipment. 

The nylons have found steadily increasing application as plastics materials for speciality purposes where their toughness, rigidity, abrasion resistance, good hydrocarbon resistance and reasonable heat resistance are important. Because of their high cost they have not become general purpose materials such as polyethylene and polystyrene, which are about a third of the price of the nylons. 

In general, the thermoplastic elastomers have yet to achieve the aim of replacing general purpose vulcanised rubbers. They have replaced rubbers in some specialised oil-resistant applications but their greatest growth has been in developing materials of consistency somewhat between conventional rubbers and hard thermoplastics. A number of uses have also been developed outside the field of conventional rubber and plastics technology. 

I mentioned in the preface to the sixth edition that when I began preparation of the first edition of this book in the early 1960s world production of plastics materials was of the order of 9 million tonnes per annum. In the late 1990s it has been estimated at 135 million tonnes per annum In spite of this enormous growth my prediction in the first edition that the likelihood of discovering new important general purposes polymers was remote but that new special purpose polymers would continue to be introduced has proved correct. 

Polytetrafluorethylene (p.t.f.e.) This polymer does not absorb water, has no solvents and is almost completely inert to chemical attack molten alkali metals and sodium in liquid ammonia are the rare exceptions. Furthermore it does not soften below 320°C, is electrically inert and has a very low coefficient of friction. It is more expensive than general purpose plastics, requires special fabrication techniques, is degraded by high energy radiation, and has a low creep resistance. 

When polyethylene was first produced in the early 1940s, physicists in England, USA, and Germany predicted a tremendous potential for it. At that time the properties of PEs were much lower than those presently available. Out of that original general-purpose PE, have been developed specific PEs in this polyolefin family of plastics such as LDPE, HDPE, UHMWPE, and so on. In turn their different properties, as well as other plastics, continually increase and their variables continue to be reduced and/or easier to process to tighter tolerances. 

Plasticator A very important component in a melting process is the plasticator with its usual specialty designed screw and barrel used that is used in different machines (extruders, injection molding, blow molding, etc.). If the proper screw design is not used products may not meet or maximize their performance and meet their cost requirements. The hard steel shaft screws have helical flights, which rotates within a barrel to mechanically process and advance (pump) the plastic. There are general purposes and dedicated screws used. The type of screw used is dependent on the plastic material to be processed. 

One commercial adhesive is marketed with the following claims High Strength Adhesive Durable Bonding Fast Acting Bonds Metals, Rubber, Ceramics, Plastics, Glass, Wood, Veneers, Fabrics, Vinyl, Cardboard, Cork, Leather, Nylon, and Other Similar Surfaces. 1 How can one substance act as a general purpose adhesive with affinity for so many types of surfaces ... 

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