Plastic level

Raw Materials. PVC is inherently a hard and brittle material and very sensitive to heat it thus must be modified with a variety of plasticizers, stabilizers, and other processing aids to form heat-stable flexible or semiflexible products or with lesser amounts of these processing aids for the manufacture of rigid products (see Vinyl polymers, vinyl chloride polymers). Plasticizer levels used to produce the desired softness and flexibihty in a finished product vary between 25 parts per hundred (pph) parts of PVC for flooring products to about 80—100 pph for apparel products (245). Numerous plasticizers (qv) are commercially available for PVC, although dioctyl phthalate (DOP) is by far the most widely used in industrial appHcations due to its excellent properties and low cost. For example, phosphates provide improved flame resistance, adipate esters enhance low temperature flexibihty, polymeric plasticizers such as glycol adipates and azelates improve the migration resistance, and phthalate esters provide compatibiUty and flexibihty (245). 

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. 

Plasticizer levels in surface waters are decreasing. The Netherlands National Institute of PubHc Health and Environmental Protection (RIVM) states that the level of phthalates in Lake Yssel fell by 75% to 0.3 -lg/L over the period 1980—1988 (56). 

Fig. 4. Oxygen permeability in a vinylidene chloride copolymer film at selected levels of plasticizer (Citroflex A-4). Plasticizer level in parts pet hundred resin...

MAFF (1996) Ministry of Agriculture, Fisheries and Food. Survey of plasticizer levels in food contact materials and in foods. Food Surveillance Papers No 21, UK... 

Effects of Curing Agent Type. Epoxide-Cured Propellant. Carboxyl-terminated polybutadiene is a linear, difunctional molecule that requires the use of a polyfunctional crosslinker to achieve a gel. The crosslinkers used in most epoxide-cured propellants are summarized in Table IV and consist of Epon X-801, ERLA-0510, or Epotuf. DER-332, a high-purity diepoxide that exhibits a minimum of side reactions in the presence of the ammonium perchlorate oxidizer, can be used to provide chain extension for further modification of the mechanical properties. A typical study to adjust and optimize the crosslinker level and compensate for side reactions and achieve the best balance of uniaxial tensile properties for a CTPB propellant is shown in Table V. These results are characteristic of epoxide-cured propellants at this solids level and show the effects of curing agent type and plasticizer level on the mechanical properties of propellants. 

Figure 7 (Figure 6 and Table I give explanations of Figures 7 to 12) shows the effect of increasing plasticizer content for a plastisol based on di-w-heptyl phthalate (DnHP). The transition from liquid to solid occurs at increasingly higher temperatures as the plasticizer level increases from 50 parts per hundred of resin (p.h.r.)... 

Figure 10 indicates the transition points for diisooctyl esters of normal aliphatic dicarboxylic acids of increasing molecular weight. The plasticizer level... 

Figure 12 shows the effect of mixing plasticizers at a total plasticizer level of 75 p.h.r. Qualitatively the results are as expected in that the transition and critical points for the blends lie between those for the individual components. 

The Declining Market for Linear Phthalates in Automotive Upholstery. The major market for linear phthalates has historically been automotive upholstery. However, the U.S. built share of the automotive market has continued to decline, and the trend (now a landslide) to smaller cars has resulted in a sharp decrease in demand for domestic vinyl upholstery. Besides this, fashion trends have turned to increased use of non-vinyl upholstery. Finally, the use of softer vinyls with higher plasticizer levels means increased opportunities in the automotive upholstery market for diisodecyl phthalate (DIDP). DIDP meets the low temperature requirements of these new softer vinyls, and at the same time offers reduced windshield fogging and lower cost on a... 

Fillers. Inert inorganic substances such as calcium carbonate, clay, silicates, and asbestos are often utilized in vinyl compositions where clarity is not a requirement. While the carbonates and clay are used ostensibly to reduce cost, beneficial results are forthcoming. The carbonates produce a dry, matte surface and are claimed, because of their alkaline nature, to benefit heat and light stability. Clay improves electrical insulation. Silicates enhance surface dryness. Asbestos fibers provide the reinforcement necessary for dimensional stability in floor tile. Antimony oxide, per se or as a surface coating on an inert carrier, provides flame retard-ance. Their only major adverse effects are to reduce tensile strength and elongation and require an increase in plasticizer level to compensate... 

Table IV. Outdoor Exposure Data at a Phosphate Plasticizer Level...

Journal of Materials Science. Materials in Medicine 14, No.10, Oct.2003, p.905-12 BLOOD RESPONSE TO PLASTICIZED POLYVINYL CHLORIDE. DEPENDENCE OF FIBRINOGEN ADSORPTION ON PLASTICIZER SELECTION AND SURFACE PLASTICIZER LEVEL... 

FIGURE 4 Effects of the plasticizer level and curing conditions (indicated in the figure) on theophylline release from pellets coated with HPMCAS in O.IM HCI (20% coating level). Ahhreviation HPMCAS, hydroxypropyl ntethylcellu-lose acetate succinate. Source From Ref. 46. 

C for 1-2 hours is typically sufficient to force complete film formation. Higher plasticizer levels may be used to avoid curing steps however, excessive tackiness of the substrates could result. 

From the same figure it is possible to analyze the size effect of HDPEflake and HDPEfine. For mix No. 1 with the two plastic levels, it is observed that the fine graded filler caused a bigger reduction in the strength than the strength decrease produced by the FIDPEflake. 

Slump was most affected by the size and shape of the plastic particles. Typically, small size and high angularity of the fillers caused a reduction in slump of the concrete batch. There were no noticeable effects on slump when 1 percent plastic was used regardless of the particle size and shape. A 4-percent plastic level, however, caused a reduction in... 

The abrasion resistance of concrete was generally enhanced with the fillers. An increase in the plastic level from 1 to 4 percent improved the resistance in all cases. 

Novel PVC foams are produced with wood fibers. Untreated and silane treated wood fibers were used. It was determined that by the selection of plasticizer level, foaming time, foaming temperature, and silane treatment of wood fiber, the foam of expected properties can be obtained. 

The volatile component is usually selected from true non-solvents for PVC resins such as the aliphatic hydrocarbons. The main purpose of the volatile ingredient is to lower the viscosity of the paste by contributing more liquid to the formulation. Very low plasticizer levels are then possible and higher durometer hardness values are attainable (as compared with plastisols). 

The 100% solid system of plastisols allows very thick coating weights to be applied. Because Increased plasticizer lowers viscosity and assists in coating application, very high plasticizer levels (for very soft films) are easily handled. The use of chemical blowing agents and mechanical air incorporation are easily adaptable to plastisol systems. 

Knappe [10] described the use of DMA to check the plasticizer level of polybutadiene/natural rubber blends. DMA can also be used to look at coatings on elastomer parts, an example being a polyurethane coating on an EPDM (ethylene propylene diene monomer) bumper part, where the low temperature storage modulus can be a key to component toughness. 

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