Thermoplastic sheet compound

TSC Thermoplastic sheet compound, can be regarded as thermoplastic prepreg, has no shelf life problems. 

Thermoplastic resins are generally reinforced with short fibres (for use with injection moulding and not considered in this book), with long fibres (thermoplastic sheet compound, Chapter 5) or with glass mat (i.e. glass mat thermoplastics or GMT). Polypropylene is the resin most used as the matrix for GMT and the reinforcement is usually a random mat, primarily chopped strand but it may be continuous filament or needled mat. 

A bundle of continuous filaments that are untwisted. Thermoplastic sheet compound (see compound). 

Postforming laminates, unlike some thermoplastic sheet materials, cannot be formed into compound curves—but with appropriate techniques complex multiple internal and external bends ( S , U etc.) can be achieved easily. 

In use are stamping compression molding presses. Plastic used can be TS sheet molding compounds (SMCs) and stampable reinforced thermoplastic sheet (STX) material (STX is a registered tradename Azdel Inc., Shelby, NC). It is usually composed of a glass fiber-thermoplastic RTP (Chapter 15). 

TS plastics in reinforced sheets and compounds are usually used. Also used are reinforced thermoplastic sheets and compounds. With TSs compression molding (CM) can use preheated material (dielectric heater, etc.) that is placed in a heated mold cavity. The mold is closed under pressure causing the material to flow and completely fill the cavity. Chemical crosslinking occurs solidifying the TS molding material. 

Courtaulds developed many products [153] based on carbon fibers prepreg as warp sheet and tape, random fiber mats, preferred orientation mats, chopped fiber, thermoset and thermoplastic molding compounds and polytetrafluroethylene (PTFE) impregnated tow. Oxidized PAN fiber was available as continuous tow, tops, yarns, woven and knitted fabrics. 

Calendering n. The process of forming thermoplastics sheeting and films by passing the material through a series of rigid, heated rolls and rolling to press out voids. Four rolls are typical. The gap between the last pair of heated rolls determines the thickness of the sheet. Subsequent chilled rolls cool the sheet. The plastic compound is usually premixed and plasticated on separate equipment, then fed continuously into the nip of the first pair of calender rolls. 

Material to be molded is placed in a matched-metal-die mold cavity and the mold closed. The part is formed by compressing the material under heat and pressure until the resin is cured or sufficiently cool to allow removal. Suitable for she (SMC) or bulk molding compounds (BMC), jH-eforms, w resin applied to reinfracemoit in the mold (wet system molding) or reinforced thermoplastic sheet (hot stamping). 

Parallel to thermosetting SMCs and BMCs are thermoplastic moulding compounds in sheet form, known as glass mat thermoplastics (GMTs), and compounded into standard granules for injection moulding and extrusion. Most thermoplastics are theoretically capable of such combination with reinforcement, but the main types used commercially at present are polyamide (PA) and polypropylene (PP). 

HDPE, high density polyethylene PP, polypropylene EVA, ethylene—vinyl alcohol SMC, sheet-molding compound ERP, fiber-reinforced plastic LDPE, low density polyethylene PE, polyethylene BMC, bulk mol ding compound TPE, thermoplastic elastomer. 

Polyurethanes are formed by reacting diisocyanates and polyols (multihydroxy compounds) to form some of the most versatile of rigid to elastic plastics. A major use is for foams with good flexibility and high rigidity. Thermoplastic polyurethanes can be extruded as sheet of c.virviiic (imghness. 

Sheet molding compounds (SMCs) and bulk molding compounds (BMCs) are the dominant materials used in automotive applications. These composites of unsaturated polyester resin, fillers and fiberglass have advantages of high stiffness, heat resistance and low coefficient of expansion. Coupled with low creep resistance, which is a distinct advantage over thermoplastic competition, and low-profile additives, which can yield Class A surfaces, these materials are well suited for applications from exterior body panels to under the hood components. 

One problem with some of the technical data sheets on thermoplastic compounds, is lack of uniformity. The variations which exists between suppliers are in the size of the test specimens, the speed at which the particular test is performed, and in some cases the temperatures in which the test is performed. To accomplish increased uniformity, it is suggested that the size of test specimens be standardized for a particular test and not be varied to display a more impressive number. Test speeds should be established for the test and not for a particular type of thermoplastic. Also, standardization of temperatures to be used if data are reported at other than 73°F. 

Except for work on complete products, a test piece must be formed before the test can be carried out. In many cases, the test piece can be directly moulded but, particularly when tests on finished products are concerned, the specimens need to be cut and/or buffed to some particular geometric shape (Figure 4.1). It is convenient to consider separately, first the mixing and moulding leading up to a vulcanised (or thermoplastic) test piece or test sheet, and secondly the preparation of test pieces from moulded sheets or products. The preparation of test pieces for tests on raw rubber and unvulcanised compounds will be considered integrally with those tests in Chapter 6. 

The matrix can be either a thermoset or thermoplastic. The oldest and still widest used material for compression molded products is phenolic. The thermoset materials used to manufacture fiber reinforced compression molded articles is unsaturated polyester sheet or bulk, reinforced with glass fibers, known as sheet molding compound (SMC) or bulk molding compound (BMC). In SMC, the 25 mm long reinforcing fibers are randomly oriented in the plane of the sheet and make up for 20-30% of the molding compound s volume fraction. 

Separating Force between Rolls in an Experimental Calender A cellulose acetate-based polymeric compound is calendered on a laboratory inverted, L-shaped calender with 16-in-wide rolls of 8 in diameter. The minimum gap between the rolls is 15 mil. The sheet width is 15 in. Calculate the separation force and the maximum pressure between a pair of rolls as a function of exiting film thickness, assuming that film thickness equals the gap separation at the point of detachment. Both rolls turn at 10 rpm. The polymer at the calendered temperature of 90°C follows a Power Law model with m = 3 x 106 dyne.s"/cm2 and n = 0.5. [Data based partly on J. S. Chong, Calendering Thermoplastic Materials, J. Appl. Polym. Sci., 12, 191-212 (1968).]... 

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