Molding conditions

Compression molding in an 800 kN SATIM press with two independently heated plates was started by heating the molding zone up to 230 C and then 

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Let us analyze the molding condition of such a product and assume that one side is made to minimum specifications and the opposite to maximum specifications where the gate is unfortunately located. Result is that the resistance to plastic flow decreases with the third power of the thickness, which means that the thick side will be filled first, while the thin side will fill from all sides. 

When using molded plastics parts such as the connectors and the circuit supports, it is important to make sure that the moldings, in addition to being made to close tolerances, be made under molding conditions that make for stable products. Electrical products are subjected to strong electrical fields in addition to the usual environmental abuse. Distortion of the product can lead to serious electrical malfunction by changing spacings that will alter electrical characteristics and if... 

To be successful, molded optical elements of plastics must be produced with careful control of the fabricating process. In the case of these optical products it is particularly important that the molding conditions be carefully controlled to minimize molded-in stress. In addition to these stresses reducing the dimensional stability of the products leading to distorted images, the stresses themselves affect the quality of the image. This is a result of the fact that the stresses/strained areas have a different refractive index from that of the... 

This interplay of the many variables is extremely complex and involves a matrix of the many variables. As an example in the molding simulation TMconcept system programmed Molding Cost Optimization (MCO) of Plastics Computer Inc., Dallas, TX, there are well over 300 variables. It is not reasonable to expect a person using manual methods to calculate these complex interactions even if molding only a modest shaped product without omissions or errors. Computerized process simulation is a practical tool to monitor the influence of design alternatives on the processability of the product and to select molding conditions that ensure the required product quality (3). 

Polyethylene terephthalate is injection blow molded to make water and carbonated drink bottles, and other liquid food packages. High stiffness, excellent clarity, and good resistance to carbon dioxide permeation are the principal attributes of these bottles. We carefully control molding conditions to promote transparency and surface gloss, which are prized for food... 

A comparison of the mechanical and physical properties of PTT, PET and PBT [67], measured from injection molded American Society of Testing Methods (ASTM) Type II samples, is given in Table 11.4. The mechanical properties of PET and PTT are highly dependent on injection molding conditions due to... 

Another important variable to consider is the fiber orientation. This is affected by many variables such as the injection molding conditions, fiber length, resin viscosity and part thickness. The fiber orientation can be determined experimentally by optical methods [44], or it can be estimated from the modulus of the molded part as follows [45-47] ... 

It has been found that the incorporation of a MMBS polymer into a composition containing a PC resin and a copolymer of MA and styrene facilitates the production of molded articles over a wide range of molding conditions without deleteriously affecting the strength or the thermal properties of the molded articles (4). 

Mineral-filled nylon 6/6 composites. Kaolin (Burgess) was treated with the appropriate silane in a Patterson Kelly 8-qt. twin shell blender with intensifier bar. Treatment levels were 1% active silane. The kaolin was compounded with nylon 6,6 (Vydyne 21x—Monsanto) in a Leistritz twin screw extruder. The compounds were tested in a dry as molded condition in accordance with ASTM D-638 (see Table 5). 

Usually a melt is molded vertically downwards, however, as it is seen in Fig. 23, the molded canvas is located in the extension zone at an angle (which sometimes may be rather large) to the vertical. Canvas in the extension zone can be practically flat (dashed line in Fig. 23) or may sag under the action of gravity (continuous line in the same figure) which is determined by the specific molding conditions, primarily by the tensile force and thickness of the extruded blank. 

The range obtained depends upon molding conditions and compositions. 

Table III. Injection Molding Conditions (Van Dorn 6 oz. Screw-Type Machine)...

Typical physical properties for an injection-molded transparent acrylic polyblend resin are given in Table II. The injection molding conditions used are given in Table III. Tensile, flexural, and impact properties are within the range reported for typical ABS and high impact polystyrene resins. Optical properties approach those of the acrylics [i.e., poly (methyl methacrylate)]. The strength properties are on the low side of those reported in the first paper for the transparent diene... 

Table I lists some properties of SMC and BMC. These are a function of resin composition, reinforcement, and molding conditions atid may be regarded as typical. This will serve as a frame of reference as to the property levels obtained with SMC and BMC. The differences which exist between SMC and BMC in tensile, flexural, and impact strengths are attributable to more than just the difference in glass loading. Fiber attrition arising from the compounding techniques for BMC as well as the shorter input fiber length account for the lower strengths.

Another practical approach to the question of moldability, especially in comparing one polymer with another, is the use of a standard spiral mold cavity and the measurement, under prescribed molding conditions, of the spiral length filled (7). 

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