Impact resistance design

Modified nylons are blends of nylon resins and specially grafted nylon resins. In the Du Pont family of Zytel resin, certain blends have been designated Supertough to emphasize the improvement in impact that blends provide over standard resins. General Electric s Noryl GTX resins consist of a nylon matrix resin and a PPO resin in dispersed form. A highly sophisticated blend, it maintains a filled nylon s HPT with no sacrifice of impact resistance. 

Cured phenolics are universally brittle in nature. This is true of both resoles and novolacs and does not depend much on the source of methylene used to promote cure. Consequently, the fillers used in molded articles are highly important to the design of the manufactured product. With resoles, the fiber or filler are usually the primary component of the final composite, with the resole acting as a binder or impregnating agent. With novolacs the resin may be the major component in the molded part. Poly-silanes and other organic polymers are also added in some applications to promote impact resistance and toughness [192]. 

Typical applications for nylon include small gears, bearings, bushes, sprockets, housings for power tools, terminal blocks and slide rollers. An important design consideration is that nylon absorbs moisture which can affect its properties and dimensional stability. Glass reinforcement reduces this problem and produces an extremely strong, impact resistant material. Another major application of nylon is in fibres which are notoriously strong. The density of nylon is about 1100 kg/m. ... 

C. C. Chamis, M. P. Hanson, and T. T. Serafini, Impact Resistance of Unidirectional Fiber Composites, in Composite Materials Testing and Design (Second Conference), H. T. Corten (Chairman), Anaheim, California, 20-22 April 1971, ASTM STP 497, American Society for Testing and Materials, 1972, pp. 324-349. 

Designers with a background in using other materials will recognize both the similarities and the differences in the behavior of the plastics discussed. As an example, impact resistance has been a continuing issue with engineering materials, particularly certain metals with similarities to many of the phenomena observed in plastics. 

The ranges of properties in plastics encompasses all types of environmental and load conditions, each with its own individual, yet broad, range of properties (Fig. 1-9). These properties can take into consideration wear resistance, integral color, impact resistance, transparency, energy absorption, ductility, thermal and sound insulation, weight, and so forth. There is unfortunately no one plastic that can meet all maximum properties. Therefore, the designer has different options, such as developing a compromise because many product requirements provide options, particularly if cost is of prime importance. 

ISO 2897-1 1997 Plastics - Impact-resistant polystyrene (PS-I) moulding and extrusion materials - Part 1 Designation system and basis for specifications ISO 2897-2 2003 Plastics - Impact-resistant polystyrene (PS-I) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 14631 1999 Extruded sheets of impact-modified polystyrene (PS-I) - Requirements and test methods... 

Bowles, K.J, (1988). The eorrelation of low-vclocity impact resistance of graphite fiber reinforced composites with matrix properties. In Composite Materials Testing and Design (8th Conference), ASTM STP 972 (J.D, Whitcomb ed.), ASTM, Philadelphia, PA, pp. 124-142. 

Secondary Properties of Candidate Materials. In terms of maximum and minimum use temperatures, we must simply ensure that our final candidate materials meet the use temperature requirements listed in Table 8.10. This design specification is not particularly restrictive, so we will save it for last. The most common measure of impact resistance is using an Izod impact test (cf. Figure 5.79). A similar test is called the Charpy test, a schematic diagram for which is shown in Figure 8.15. We will find relevant impact resistance data for our candidate materials, if available, and ensure that this design criterion is met as well. 

Type designation Nominal thickness, mm Thickness tolerance, mm Wear resistance cycle Ball impact resistance, a mm MD CD Boiling water resistance J rating 5 Radiant heat resistance, s ... 

There are other proprietary systems such as polyacrylamate. It is Ashland Chemical s Airmax that is designed for use with preforms or glass mats. These reinforced plastics possess high flexural modulus, good impact resistance, and high temperature stability. Systems with similar performance from isocyanate-based polymers are also used. 

In foods, stmcture matters because it is responsible for many of the desirable properties, such as appearance, texture, and even flavour release. However, unlike other composites that are designed to provide final physical and mechanical properties from the structure (e.g., load-bearing bridges, impact-resistant fibre composites, etc.), food stmctures must break and fail under chewing action otherwise they are not consumable food. In a sense, physical properties of foods are opposite to those valuable to engineers. The search for relations between the stmcture and physical properties of foods started only in the 1980s. [See e.g., several chapters in Peleg and... 

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