Powder Technology in Plastics Processing

Industrial processes involving handling of solid raw materials are highly dependent on our understanding of the fundamental characteristics and properties of the starting solid materials, as well as whether or not the related process hardware and operation are properly designed and optimized. This is true of almost all plastics manufacturing processes since particulate solids handling is the most elementary processing step.

This book provides a broad understanding of powder technology and the significance of particulate solid characteristics that are applicable to plastics manufacturing processes. It focuses on the particular characteristics of solid materials relevant to plastics manufacturing processes. Applications of engineering principles based on the selected solid characteristics which illustrate the uniqueness of the subject are also included.

The useful and practical information within offers engineers solutions to otherwise unclear problems commonly encou ntered in industry. The selected examples of research investigations provided should also inspire readers to formulate further fundamental as well as applied research studies on the inter- and intra-relationship between powder technology and plastics processing technology.

Contents:
- Introduction
- Polymers, Additives, and Processing
- Fundamental Parameters of Powder Characteristics
- Solid-Solid Mixing
- Storage and Discharge of Particulate Solids
- Pneumatic Conveying of Particulate Solids
- Gas Fluidization
- Interparticle Forces
- Effects of Particle Characteristics on Rheological Properties of Polymeric Melts

Leseprobe:

Not all plastics processing plants have the same facility layouts and designs. Some
may engage automation systems while others may rely more on the labor forces.
But as far as material flow systems are concerned, there is little difference among
them. Figure 3.1 shows a typical material flow diagram of a plastics processing
plant.
As can be seen from Figure 3.1, after a solid bulk material such as resin is brought
to the plant by trucks, it will be stored in storage tanks until it is needed for processing.
Transportation of the bulk material from the storage tanks to the hoppers
of the processing machines when needed is usually carried out in pipes by pneumatic
conveying systems. If the bulk material is the only required raw material for
making the products, it will be the only material fed into the hopper. But when
additional raw materials (e.g., other types of resins and additives) are needed for
processing, all the ingredients will then be ei ther separately discharged into the
hopper where they will be mixed and/or dehumidified, or they will be premixed
before being discharged into the hopper. In some circumstances, such as in making
masterbatches, dosing devices will be employed for monitoring the feeding into
the hopper that sits on a processing machine.
Finished products coming out from the processing machines need to be cooled and
solidified before they are stored in warehouses to wait for shipping. If the products
are semi-finished products like compounded resins or masterbatch concentrates,
drying and dewatering (if water baths are used for cooling) of the solidified strands
are required before they are pelletized, packed, and stored.
Echoing what was mentioned in Chapter 1 on the conceptual structural breakdown
of the plastics processing technology suggested by Tadmor and Gogos [1], the
above discussion on the basic flow of materials in the industry indicates that handling
particulate solids is the first processing component of the elementary steps
in plastics processing. Understanding of the fundamental characteristics of the particulate
solids (i.e., particles) is an essential prerequisite for proper hardware designs
and process controls. These fundamental material characteristics include mean
particle size and size distribution, particle shape, and particle density, which will
be discussed in the following sections of this chapter.