Parts per hundred

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). 

Economics. As with the alkyl tin stabilizers, the market pricing of the mixed metal stabilizers tend to be directed by the particular appHcation. The calcium—zinc and barium—cadmium packages are typically used at 2.0—4.0 parts per hundred of PVC resin (phr) in the formulation. These completely formulated products are sold for 2.50— 4.40/kg for the Hquid products and 3.20— 6.50/kg for the soHds and pastes. The higher efficiency products aimed at rigid appHcations tend toward the higher end of the cost range. 

The carbon black in semiconductive shields is composed of complex aggregates (clusters) that are grape-like stmctures of very small primary particles in the 10 to 70 nanometer size range (see Carbon, carbon black). The optimum concentration of carbon black is a compromise between conductivity and processibiUty and can vary from about 30 to 60 parts per hundred of polymer (phr) depending on the black. If the black concentration is higher than 60 phr for most blacks, the compound is no longer easily extmded into a thin continuous layer on the cable and its physical properties are sacrificed. Ionic contaminants in carbon black may produce tree channels in the insulation close to the conductor shield. 

Ingredient Parts by weight Parts per hundred resia (phr) % By weight... 

Plasticizer Efficiency. This is a measure of the concentration of plasticizer required to impart a specified softness to PVC. Such a softness of material may be measured as a British Standard Softness (BSS) or a Shore hardness (Pig. 1). Por a given acid constituent of plasticizer ester, ie, phthalate, adipate, etc, plasticizer efficiency decreases as the carbon number of the alcohol chain increases, eg, for phthalate esters efficiency decreases in the order DBP > DIHP > DOP > DINP > DIDP > DTDP. An additional six parts per hundred in PVC of DIDP rather than DOP is required to give a hardness of Shore 80 when ah. other formulation ingredients remain constant. The consequence of this depends on the overall formulation and product costs. In addition to size of the carbon number of the alcohol chain, the amount of branching is also significant the more linear isomers are of greater efficiency. 

Fig. 1. Relative efficiency of plasticizers where H represents Cg phthalate +, C q phthalate A, phthalate and , phthalate phr = parts per hundred mbber. Values for the trimeUitates fall in the shaded area. BSS 35 is equivalent to a Shore A hardness of 80, test method BS2782.

The effect of plasticizers and temperature on the permeabiUty of small molecules in a typical vinyUdene chloride copolymer has been studied thoroughly. The oxygen permeabiUty doubles with the addition of about 1.7 parts per hundred resin (phr) of common plasticizers, or a temperature increase of 8°C (91). The effects of temperature and plasticizer on the permeabiUty are shown in Figure 4. The moisture (water) vapor transmission rate (MVTR or WVTR) doubles with the addition of about 3.5 phr of common plasticizers (92). The dependence of the WVTR on temperature is a Htde more comphcated. WVTR is commonly reported at a constant difference in relative humidity and not at a constant partial pressure difference. WVTR is a mixed term that increases with increasing temperature because both the fundamental permeabiUty and the fundamental partial pressure at constant relative humidity increase. Carbon dioxide permeabiUty doubles with the addition of about 1.8 phr of common plasticizers, or a temperature increase of 7°C (93). 

Fig. 4. SmaH-angle x-ray scattering pattern from PVC plasticized with 20 parts per hundred resin of dioctyl phthalate (18).

Siding. The resin most used for siding is poly(vinyl chloride) homopolymer, compounded with modifiers, stabilizers, and pigments. Modifiers are most often acryhc esters, followed by chlorinated polyethylene or ethylene—vinyl acetate, used at 6—8 phr (parts per hundred resin). The modifier increases the impact strength of the rigid PVC. 

Plasticizers. These are used to improve compound processibiHty, modify vulcani2ate properties, and reduce cost. Por many appHcations, where cost and processibiHty are the objective, naphthenic and aromatic oils are preferred. They are inexpensive yet effective in improving processibiHty at high filler levels. The compatibiHty of the naphthenic oils is limited to about 20 parts per hundred mbber. Aromatic oils are more compatible and can be used at higher levels (132). 

Low levels of ultraviolet absorbers (typically 0.2-0.8 pphr [parts per hundred resin]) can also be useful in preventing initiation of degradation mechanisms. Modified benzophenones and benzotriazoles are in widest commercial use. 

One inherent weakness of Vulkollan-type materials is their susceptibility to hydrolysis. Life in a humid environment may, however, be doubled by the incorporation of 2 pphr (parts per hundred resin) of a carbodiimide. 

Tsai et al. have also used RAIR to investigate reactions occurring between rubber compounds and plasma polymerized acetylene primers deposited onto steel substrates [12J. Because of the complexities involved in using actual rubber formulations, RAIR was used to examine primed steel substrates after reaction with a model rubber compound consisting of squalene (100 parts per hundred or phr), zinc oxide (10 phr), carbon black (10 phr), sulfur (5 phr), stearic acid (2 phr). 

Parts per billion (ppb) Parts of a contaminant in a billion parts of air or water. Care has to be taken in ensuring the term billion is the correct one. In the past in the UK, a billion was 10 -, but in the U.S, a billion is 10 , It is now assumed that current practice relates to the latter. Other terms encountered are parts per hundred million (pphm) and parts per million (ppm). 

Toxicity and Hazards. The odor cf ozone can be detected in concn as low as several parts per hundred million by vol (pphm). The threshold limit value (TLV) is O.lppmor 0.2mg/m3 its toxic dose level (TDL), 50% kill concn is 2ppm (Ref 6) Pure 100% liq ozone may be kept safely at 90°K (cooled by liq oxygen) for indefinite periods of time, but the smallest provocation, such as a spark or fast warming, even only up to bp (161°K), causes detonation. The evapn of liq ozone, for example, in the process of the prepn of pure gaseous ozone is, therefore, a dangerous procedure (Ref 3, p 224)... 

The term percentage or percent (%) means parts per hundred. 

Alkanesulfonates are widely used as an internal antistatic agent for poly(vinyl chloride) (PVC). Since alkanesulfonates cause hazing of unplasticized PVC in the normally used quantities of 1.0 to 1.5 parts per hundred parts resin (phr), its main use is in the manufacture of opaque PVC-calendered film. To produce transparent unplasticized articles, the addition of alkanesulfonates should not exceed 0.3 phr. Figure 40 shows the antistatic effect of alkanesulfonates in PVC. 

In bacterial cells, marker compounds are present at the part per hundred to part per thousand level. In environmental samples, which represent a complex mixture of components, such markers are often present at the part per ten thousand to part per hundred thousand level. In certain clinical samples, in some instances, these markers may be present as low as parts per... 

Abbreviation for parts per hundred of rubber. Phthalocyanine Dyes... 

This is a sample that is typical of the parent material for the characteristic under inspection. You have to be careful in the way that you define the characteristic of interest. A sample may be adequate and representative if the concentration of the analyte is at a 5% mass/mass level (i.e. 5 parts per hundred) but it may not be acceptable if the analyte is present at the 5 mg kg-1 level (i.e. 5 parts per million). Knowledge of the method used for the analysis is also important. If the method produces results with an uncertainty of 30% (see Chapter 6, Section 6.3), the method of sampling need not be so finely controlled as in the case of a method which produces results with an uncertainty of only 5%. 

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