Plasticising capacity

The shot capacity is the full amount as a weight or volume of material injected during moulding from the screw. This is usually given as a shot capacity for polystyrene, and will vary with material. The shot size is the amount of material required to fully fill a moulding tool. 

This is the maximum rate at which the injection imit can deliver polymer melt. In extrusion this is a continuous process. However, it should be remembered that injection is an intermittent process. 

The effeetiveness of plastication depends on the shot size, eylinder capacity, screw design, serew speed and heater band power. It will also vary from material to material. 

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The negligible water absorption avoids the need for predrying granules. The low specific heat (compared with polyethylene) enables the polymer to be rapidly heated in injection cylinders, which therefore have a higher plasticising capacity with polystyrene than with polyethylene. The setting-up rates in the injection moulds are also faster than with the polyolefins so that faster cycles are also possible. 

Inadequate mixing Check homogeneity of melt and plasticisation capacity of cylinder. 

The amount of material that can be melted at any one time (plasticising capacity). 

For samples that meet the solubility requirements of the SEC approach, analyses were also reported for additives in polymers such as PVC and PS [28,29]. Direct SEC analysis of PVC additives such as plasticisers and thermal stabilisers in dissolution mode has been described [28,30,31 ]. In the analysis of a dissolved PS sample using a SEC column of narrow pore size, the group of additives was separated on a normal-phase column after elution of the polymer peak [21]. Column-loading capacity of HPSEC for the analysis of additives, their degradation products and any other low-MW compounds present in plastics has been evaluated for PS/HMBT, PVC/TNPP and PVC/TETO (glyceryl tri[l-14C] epoxyoleate) [31]. It was shown that HPSEC can be used to separate low-MW compounds from relatively large amounts of polymers without serious loss of resolution of the additives the technique has also been used for the group analysis of chlorohydrin transformation products of the TETO model compound [32]. 

A study has been carried out on the interactions of blood with plasticised poly(vinyl chloride) biomaterials in a tubular form. The influence of different factors such as the biomaterial, antithrombotic agent, blood condition and the nature of the application is represented when considering the blood response in the clinical utilisation of the plasticised PVC. The PVC was plasticised with di-(2-ethylhexyl)phthalate (DEHP) and tri-(2-ethylhexyl)trimellitate (TEHTM)and in-vitro and ex-vivo procedures used to study the biomaterial with respect to the selection of the plasticiser. The blood response was measured in terms of the measurement of fibrinogen adsorption capacity, thrombin-antithrombin III complex and the complement component C3a. X-ray photoelectron spectroscopy was used for surface characterisation of the polymers and the data obtained indicated that in comparison with DEHP-PVC, there is a higher reactivity... 

An example of the growth behavior of crazes in a liquid environment is shown in Fig. 20 which is taken from the results of Williams and Marshall They measured the craze length versus loading time at different Kj-values in PMMA specimens immersed in methanol. The time-depettdent craze-behavior was interpreted in terms of a plasticisation mechanism incorporating the effect of the fluid Due to its porous nature the craze has a very high area to volume ratio so that penetration of the fluid by only a small distance leads to a complete plasticisation of the fibrils and a subsequent drop in the load carrying capacity (t of the fibrils the material effectively behaves as one with a lower craze stress oojc (a < 1). 

World consumption of plasticisers was nearly 5.7 milUon tonnes in 2002. Global capacity utilisation in the plasticiser industry has been low it increased to 73% in 2002 from a very poor 67% in 1998, but only because of rationalisation, combined with strong demand in developing regions, mainly Southeast Asia, and a healthy residential construction market in North America. The value of the global plasticiser business was estimated at US 4.9 billion in 2003. Plasticiser demand growth is the lowest of any major additive, at rather less than 3% worldwide. 

The Emopean Council for Plasticisers and Intermediates put European consumption of plasticisers at 958,000 tonnes in 2001. It is now believed to be over one million tonnes. Flexible PVC has shown poor growth in Europe in recent years, even more noticeably than in the US. Growth has slowed to 1.6% in Western Europe and exports have dropped, leading to reduced capacity utilisation, lower profitability, and rationalisation caused by oversupply. 

Prices are also affected by available production capacity, recent plant outages etc. Surplus production capacity has been available in the recent past for several additives and for intermediates such as phthalic anhydride and epichlorohydrin. At the end of 2002, the two main US producers of sebacic acid, which is a precursor of specialised aliphatic plasticisers, both withdrew from the market in the face of competition from cheap Chinese imports, although another company entered the field instead. Melamine prices have reached 1300 euros/tonne in Europe, although they are lower in Asia. Capacity has fluctuated because of plant problems but considerable new capacity is being developed. 

The shot capacity of the injection unit does not depend on the size of the plasticising cylinder used ... 

Butyl and halobutyl rubbers are considered with respect to their chemical stmcture, market size, manufacture and plant capacities. The production of both types of rubbers is described, with details of grades and properties. Compounding butyl and halobutyl mbbers is discussed and the use and effect of fillers, plasticisers, tackifiers and processing aids is examined. Vulcanising systems are also described and it is found that butyl rubber requires highly activated cure systems and halobutyl mbber can be cured by zinc oxide with other accelerators and curatives added at low levels for modification of cure rate or state. CANADA... 

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