Commercial PVC resin

Differential scanning calorimetry (DSC) is fast, sensitive, simple, and only needs a small amount of a sample, therefore it is widely used to analyze the system. For example, a polyester-based TPU, 892024TPU, made in our lab, was blended with a commercial PVC resin in different ratios. The glass transition temperature (Tg) values of these systems were determined by DSC and the results are shown in Table 1. 

Polymer structure and formulation. As an example, Woo et al. [7] measured OIT values for series of commercial PVC resins and polyester thermoplastic elastomers (TPEs). The researchers used the ASTM D3895-80 procedure, but substituted air as the oxidising gas instead of pure oxygen. A dependency on thermal processing history of the TPE film samples appeared to influence the measured OIT in the PVC study, chemically different chain ends affected polymer stability and hence OIT values. 

The final step is termination of chain growth mostly by radical transfer reaction to monomer [306], whereas combination or disproportionation are observed only to a small extent. The monomer radical is able to start a new chain. The most widely used procedures for preparation of commercially PVC resins are, in order of their importance, suspension, emulsion, bulk, and solution polymerization. A common feature of the first three methods is that PVC precipitates in liquid VC at conversions below 1%. The free polymerization of VC in a precipitating medium exhibits an accelerating rate from the beginning of reaction up to high conversion [307]. This behavior is called autoacceleration and is typical for heterogeneous polymerization of halogenated vinyls and acrylonitrile [308]. 

Affolter [230] has discussed methods of characterisation and identification of polyester plasticisers. Polymeric and monomeric plasticisers were distinguished on the basis of molecular weight determination, TG, and TLC, and chemically identified by IR spectroscopy, and by the determination of monomeric units by saponification. These methods use sample sizes of about 1 g. Marcilla et al. [231] have studied the thermal degradation behaviour of ten commercial PVC resins by TG. TG was also used to study eight commercial phthalate and adipate plasticisers. Different kinetic models were suggested for the correlation of weight loss data at four heating rates for two resins and three plasticisers. 

Rubber, nylon, phenolic resins, cellulose and commercial PVC... 

Table I compares results obtained in this manner with those reported by Arro Laboratories for 3 broad-distribution PVC standards. Table II does the same for several PVC commercial suspension resins from Sha-winigan, using a Mark-Houwink expression as a basis for comparison of W values.

Figure 11 shows examples of commercial PVC compounds with different stabilizers which have been exposed at 180 °C. A comparison of Samples 2 and 3 shows a negative influence of low molecular epoxide resin on the performance of the organostannic stabilizer used. All three tests were carried out in air and are compared in Figure 12. 

PVC is inherently the most heat-sensitive of the major commercial thermoplastic resins. Stabilization consists primarily of a stabilizing action on labile chlorine atoms in the PVC resin in order to prevent dehydrohalogenation and secondly in the neutralization of HCl by incorporation of bases [138]. Worldwide consumption of heat stabilizers is slightly above 300 thousands of metric tonnes per annum [139] (Table 16). 

Industrial development of PVC resins began about 50 years ago. Full commercial scale production started in Germany in 1931 and in the United States in the late 1930s. U.S. production was sparked by the observation by Waldo L. Semon at B. F. Goodrich in 1933 that PVC, when heated in the presence of a high boiling liquid (a plasticizer), became a flexible material that resembled rubber or... 

Initial work to process PVC resin into manufactured products led many investigators to believe that the polymer was not a useful one. Some of the performance shortcomings of PVC were overcome by the advent of plasticizers and development of copolymers, both of which were responsible for the subsequent commercial growth of PVC. Although resins with improved stability and processing characteristics have since been developed, the tremendous growth of vinyl plastics is in no small measure due to the development of effective heat stabilizers as well as efficient processing equipment. 

Commercial PVC blends with either EVAc, or PVC-VAc have been offered for outdoor applications since the 1970 s as high impact strength, rigid formulations (e.g., Denkovinyl , Hostalit , Vinidur , Solvic , or Trosiplast ). The resins show good hardness, rigidity, adequate heat, chemical, and flame resistance. 

Purity of PVC is determined by the purity of the raw materials used in polymerization, oxygen eoneentration, and method of polymerization. Typical purity of monomer is in the range of 99.97 to 99.99%. Typical purity of commercial initiators is 95% and better. This shows that from the point of view of raw materials, PVC resin is expected to have high purity. 

Plastisols are the result of a special class of fine-particle PVC resin (dispersion grade) being dispersed in liquid plasticizers. Organosols are the product of a plastisol and a volatile diluent or a solvent. Commercial PVC copolymers include grades copolymerized with vinyl acetate, vinylidene chloride, and maleate and fiimarate esters. 

Typical Particle Size Distribution Information of a Commercial PVC Plastisol Resin. 

Change of Viscosity with Time for Selected Commercial PVC Plastisol Resins. 

Although thete have been a number of post- polymerization chemical modificalions of PVC recorded in the literature, the most commercially successful of these has been post-chlorinaliotL Processes for the chlorinalion reaction include a solution method (135 chlorinating a solvent-swollen, PVC resin chlorination of PVC as a dry powder (136-139 or chlorinating the suspended resin in water (140). The process employed can have a dramatic effect on the structure of the CPVC produced because the reaction is heavily depended upon the abihty of the chlorine radical to difiiise into the PVC. The most common reaction scheme is generation of free radicals of chlorine which then react with the PVC chain by ... 

SEM micrograph of (a) a vegetable oil-based epoxy resin and (b) a commercial PVC blend. 

The polymer can be made by suspension, emulsion, solution, or bulk polymerization methods. Most of the PVC used in calendering, extrusion, and molding is prepared by suspension polymerization. Emulsion polymerized vinyl resins are used in plastisols and organisols. ° Only a small amount of commercial PVC is prepared by solution polymerization. The microstructure of PVC is mostly atactic, but a sufficient quantity of syndio-tactic portions of the chain allow for a low fraction of crystallinity (about 5 percent). The polymers are essentially linear, but a low number of short-chain branches may exist. The monomers are predominantly arranged head to tail along the backbone of the chain. Due to the presence of the chlorine group, PVC polymers are more polar than polyethylene. The molecular weights of commercial polymers are M = 100,000 to 200,000 ... 

Table 19.7 Properties of some commercial, styrenic resin/PVC blends ...

The donor atom has a reasonable reactivity with a PVC polymer chain at 180-200 C, plastic molding temperatures of polyvinyl resins, but the bond of the donor atom with tin also has a reasonable stability as a PVC stabilizer during the processing. If PVC stabilizers begin to decompose at lower temperatures than the decomposition temperatures (90-130 C) of the commercial PVC and the disappearance rate of PVC stabilizer is high, then we cannot expect the effect to last. 

Poly(vinyl chloride) (PVC) is one of the oldest yet most important thermoplastic polymers. Commercially, PVC is manufactured by three main processes suspension, mass, and emulsion polymerization. The polymers produced by mass and suspension processes are similar and are used in similar applications. The suspension process is currently the dominating industrial PVC process (about 75% of the world s PVC capacity). The emulsion polymerization process is used to produce specialty resins for paste applications (e.g., coated fabric, roto-molding, slush molding). PVC manufactured by the mass process have properties similar to those of the suspension process. 

PVC usually polymerizes in a head-to-tail arrangement however, a small amount of branching is present in all commercially available PVC resin. The polymerized sequences tend to be atactic, but some syndiotacic sequences can form. These syndio-tactic sequences are believed to be responsible for the regions of crystallinity found in PVC polymers. The amount of crystaUinity present in the PVC polymer generally increases with molecular weight. The molecular weight of the polymer can be controlled by both reaction conditions and reaction time. The ability to control the molecular weight of the polymer enables the manufacture of resins with a wide variety of... 

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