Thermoplastic polymer binder

The debinding of powder injection molding workpieces, which consist of about 60 vol.% of a solid matrix (metal or ceramic powders) and thermoplastic polymer binders, was examined by extraction with scC02 [1]. By this technique the debinding time could be reduced from 1-2 days for pyrolysis to 1-2 hours for SFE. 

Examples of plasticizers include adsorbed water and ethylene glycol for vinyl binders, stearic acid and oleic acid for wax binders, glycerine and ethylene glycol for clay bodies, and molten oils and waxes for thermoplastic polymers used in injection mol ding. 

The quantity of conductive component varied from 15wt% to 30wt%. Solution of thermoplastic polymer in organic solvent was prepared separately. Then, a mixture of dry components Ni(OH)2 + graphite was added to that solution and mixed one more time. Content of polymer binder in composition of a dry electrode was 5-10wt%. 

The two binders, the ENG and the thermoplastic polymer, are inert concerning the methane adsorption. The methane quantity delivered depends only on the activated carbon adsorption isotherm and its apparent density in the adsorbent composite block (Table 1). For pure methane, the quantity delivered at 298K between 3.5 and 0.1 MPa is equal to 89 (v/v). 

As an additional component, various thermoplastic polymers can be used. As a binder for copper clad laminates, a solution of solid epoxide resin (Epikote 1001), BPA/DC prepolymer, Zn acetate and poly(phenylene sulfide) was used [83], Other binders for reinforced plastics contain polysulfone. Such compositions consist of liquid BPA/ECH epoxide resin, BPA/DC prepolymer, polysulfone and bis(4-hydro-xyphenyl)sulfone [85]. Bis(4-aminophenyl)sulfone can be also added [86]. In such systems the bisphenol reacts with the epoxide resin as a chain extension agent, whereas the diamine crosslinks the diepoxide. The Tg values are close to 200 °C. They can be increased a little, if the BPA/ECH epoxide resin is replaced by the tetra-epoxide A,A,A, A -tetrakis(2,3-epoxypropyl)diaminodiphenylmethane [87]. 

In practice, binder system may consist of three or four additives that differ in their volatility and chemical decomposition. Furthermore, interactions between the binder and the particle surfaces may alter the decomposition kinetics of the pure polymer. In view of its complex nature, a detailed analysis of thermal debinding is not useful. Instead, we consider the basic features of the process for a simplified system consisting of a powder compact with a single binder [e.g., a high molecular weight thermoplastic polymer such as poly(methyl methacrylate), poly(propylene), or poly(vinyl butyral)]. 

Polymer concrete consists of a mineral filler, for example an aggregate, and a polymer binder, which may be a thermoplastic, but more frequently is a thermosetting polymer (Figure 1.1). 

These are obtained by dispersion of one or more solid fillers in a binder. The binder should be either inorganic (silica based ceramic) or organic (thermosetting or thermoplastic polymers) depending on the environmental conditions. Fillers are composed of ferrite described above with granulometry comprised between 12 and 100 pm and also of simple ferromagnetic compounds (Fe, Co, Ni) or complex alloys. 

Thermoplastic carbon composite materials are a favonrable material combination for bipolar plates becanse they can be mannfactnred by the mass production process of injection monlding [102]. Electrical condnctivity of a carbon composite requires a high content of carbon, nsnally a mixtnre of graphite and active coal. The percolation limit of the graphite in the polymer binder has to be exceeded, leading to direct contact between graphite particles. Additionally, a basic condnctivity of the polymer matrix by the smaller active carbon particles is achieved. The injection... 

Some liquid Cl can be plasticizers (PI) of the polymer binder at the same time. Many oil-soluble Cl show this property towards polyoileflns. The Cl soluble in PI, solvents and other CM expand their limits of blending with thermoplastic binders. 

Plastic products formed of the blends of compatible components commonly acquire perfect mechanical properties. Nevertheless, sometimes process peculiarities and specifics of their operation conditions as well as economical reasons force the manufacturer to introduce ingredients that are either incompatible or have restricted compatibility with the polymer binder and other CM components. For instance. Cl of inhibited plastics are, as a rule, highly polar materials poorly compatible with non-polar polymers, including PE, PP, PS and other thermoplastics widely adopted as binders (see 1.3). 

In FDM the source material is a thermoplastic polymer filament that is heated and extruded to form the product as shown in Figure 23.14. The product is formed in a layer-by-layer manner similar to building up layers of icing on a cake. The computer controls the jc-y position of the filament and the deposition rate. The filament can be loaded with up to 60 vol% ceramic powders once the part is completed the binder is removed and the part is sintered. Most of the work in the RP of ceramic parts by FDM has involved Si3N4. The feasibility of making components out of AI2O3, SiOi, and PZT has also been demonstrated. The abbreviation FDC (fused deposition of ceramics) is used to identify this special application of FDM. 

Regarding the asphalt s characteristic Marshall properties, the use of thermoplastic polymer-modified bitumen increases stability and decreases when compared to the same asphalt with the same binder content. 

Laminates are plastic materials formed by bonding together reinforcing sheets or webs with a polymer or plastic. Heat and pressure are usually required. The reinforcing sheets may be fabric, mats, or paper, and the binder polymer may be either a thermoset or thermoplastic polymer. Table L.l shows the properties of laminates that are reinforced with different types of fibers. 

Although both thermosetting resins and thermoplastic polymers are nsed as binders in laminates, the thermosetting materials are more conunon becanse they generally provide superior stability, thermal resistance, and electrical properties. 

The term binder is used to mean the matrix in which the fibres are embedded or treated. The binders, sometimes called adhesives or matrixes, in this chapter refer to polymeric materials having reasonable mechanical properties. The binder may be thermosetting or thermoplastic polymers. 

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