Mold operation 974 INDEX

A similar effect on hardness development can be obtained by mixing two polymers made with different chain extenders. Table 6 shows that a polymer made with 1,4-butanediol as chain extender and another with the bis(hydroxyethylether) of hydroquinone as chain extender each have hardness build-up index values higher than does a 50/50 blend of the two. It is suggested that the poor spatial fit of the mixed hard segments results in slow domain formation on cooling. There is an important practical consequence of this observation as it relates to the mixing of TPU elastomers from different suppliers in an industrial molding operation. 

Thermal Properties. Thermal properties include heat-deflection temperature (HDT), specific heat, continuous use temperature, thermal conductivity, coefficient of thermal expansion, and flammability ratings. Heat-deflection temperature is a measure of the minimum temperature that results in a specified deformation of a plastic beam under loads of 1.82 or 0.46 N/mm (264 or 67 psi, respectively). Eor an unreinforced plastic, this is typically ca 20°C below the glass-transition temperature, T, at which the molecular mobility is altered. Sometimes confused with HDT is the UL Thermal Index, which Underwriters Laboratories estabflshed as a safe continuous operation temperature for apparatus made of plastics (37). Typically, UL temperature indexes are significantly lower than HDTs. Specific heat and thermal conductivity relate to insulating properties. The coefficient of thermal expansion is an important component of mold shrinkage and must be considered when designing composite stmctures. 

The control of the deposition thickness is crucially important in the LCVD operation, regardless of the modes of operation. However, it is very difficult to measure the actual thickness of ultrathin film deposited on polymeric substrates. If an LCVD film is deposited on polymeric substrates, such as films, fibers, and molded articles, it is nearly impossible to determine the thickness by a simple nondestructive method that can be done quickly enough to monitor the LCVD operation. In order to circumvent this problem, the use of special substrates added or attached to the normal substrate is found to be satisfactory. A small piece of Si wafer is a typical case of this approach. Ellipsometer can measure the deposition on the Si wafer easily and quickly, which provides thickness and refractive index values. 

The software program is tailored for each molded piece. An operator, led by a menu, performs all the indicated measurements. All sampling, the period between the statistical analysis of the data, remarks of the inspector are recorded under the corresponding design number of the part on the data-disc. The results of the measurements appear on the monitor along with the actual and index values and tolerance limits. 

There are several differences between the major stretch blow molding machines in the industry. Cincinnati Milacron offered an indexing type machine. It had the advantages as being very rugged and versatile. It was also a relatively simple machine to operate and provided the user a machine that produced the lowest cost bottle per machine cost. TTie ovens could be moved to allow for equilibration time to be adjusted for each different style preform. 

Generally, the three stations are arranged in a circular pattern with three mold-carrying arms indexing from station to station around a common center-point. This style of machine is called a Carousel style because it operates similarly to carousels at amusement parks. It is also referred to as a turret machine— Eig. 15.17 shows a typical layout in production. 

Shrinkage and warpage are two important quality indexes of the plastic product and always the focus of the researchers[l-4]. Automatization of plastic production makes the molding optimization further complex by operations that move the products directly fi om the molding machine to assemble stations. So investigating the influence of the fiber content and proeessing... 

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