SRIM

The largest segment of the CASE family of polyurethanes are elastomers. Cast polyurethane elastomers reached a new dimension when high pressure impingement mixing led to reaction injection molding (RIM). This technology is used widely in the automotive industry, and reinforced versions (RRIM) and stmctural molded parts (SRIM) have been added in more recent years. 

Cast nylon is used for prototypes and small production runs processed by casting, roto-moulding and reaction injection moulding (RIM), possibly with structural reinforcements (SRIM) such as glass mat or fabric. 

General- purpose Self-lubricating SRIM glass mat or ... 

SRIM or SRRIM - structural (reinforced) reaction injection moulding - mats or fabrics are placed in the mould before injection of the resin, possibly reinforced with short glass fibres. 

Figure 4.5 (a) Comparison between the computed and measured displaced profiles SRIM-97 simulation versus experimental data. (From [63]. 1999 Elsevier B.V. Reprinted with permission.) (b) values for the C and Si sublattices in 6H-SiC versus ion dose for 300K implantation temperature. (From [31]. 2002 Elsevier B.V. Reprinted with permission.) (c) for the Si sublattice in 6H-SiC versus ion dose and ion mass for 180-190K implantation temperature. (From [63]. 1999 Elsevier B.V. Reprinted with permission.)... 

Figure 4.17 Ion implantation depth profile as calculated by SRIM. Al was implanted at 700°C. Multiple implants starting at 1 75 keV were used to achieve the box profile. (From [87], 2000 Trans Tech Publications Inc. Reprinted with permission.)...

J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Range of Ions in Solids, Pergamon Press, New York, 1985. Computer code available at http // www.srim.org. 

Ziegler JE, Biersack JP, Littmark U. (1985) The Stopping Power and Ran e of Ions in Matter, vol. 1. Pergamon Press, New York, http //www.srim.org... 

Since Ihe changes in. the poicni lal eiiei gy of the spring and iiie kinei ic eiiCTgv of the elevator nui.si srim to 7ero. 

According to the SRIM code (www.srim.org), lO cm Si ions introduced by the elastic energy losses about 130 displacements per atom (dpa), while Xe ions - less than 0.014 dpa. On the other hand, electronic energy losses of Si ions were -0.2 keV/nm, while for SHI they achieved 14keV/nm. Therefore, Si segregation and growth of the nanoprecipitates under Xe ion irradiation were mainly due to the electronic energy losses of SHI. 

Urethane-Modified Isocyanurate Foams. Urethane-modified isocyanurate foams are prepared by the trimerization of a polyisocyanate in the presence of a polyol, a trimerization catalyst, a blowing agent, and a surfactant. The foams have high flame and temperature resistance. The combined use of an isocyanurate foam and glass fiber not only improves the physical properties, e.g., flexural strength, friability, etc. but it also improves the flame resistance because the char formed from the foam acts as thermal barrier and protects it from flame and heat. This type of composite, therefore, is widely used for buUding applications in the U.S.A. Urethane-modified isocyanurate foam systems have also been used in the SRIM process (26, 36, 37). 

The latest trend in foamed composites is automotive structural parts produced by the SRIM (structural reaction-injection-molding) process. The SRIM process is a method of the reactive liquid injection molding (i.e., LIM). LIM includes RIM (reaction injection molding), RRIM (reinforced RIM) and RTM (resin transfer molding). IX M (Liquid Composite Molding) is a relatively new technical term which includes SRIM, RRIM and RTM (Resin Transfer Molding). 

The first step of the SRIM process is to place a fiber mat in a closed mold. Then, a low-viscosity foaming mixture is injected into the mold. The mixture penetrates into the mat and then expands to form a foamed composite. (SRIM is also called Mat-Molding RIM or MMRIM). SRIM is preferably used for making thin, large panels, such as door-trim panels, spare-tire covers, etc. 

Examples of the matrix resins employed for SRIM include rigid polyurethane (7,15, 16), or urethane-modified isocyanurate foam (9, 26, 35, 36). The matrix resins for foamed composites are required to have low viscosity and relatively slow cream time for better impregnation into fiber mat and fast-cure cycle time for higher j oductivity. 

Before the introduction of the SRIM process, an open-mold process was employed for making fiber-reinforced door-trim panels. The open-mold jH ocess is composed of the following steps ... 

An improvement in the production of foamed composite-door panels was reported by Schumacher et al (7). The process consists of the use of the SRIM process and a low-viscosity urethane foam system. In addition, vinyl- and glass-mat preform technology and IMR (internal mold release) were employed. The demold time at 75 C was 45 seconds, and molded densities were 400 to 800 g/cm. ... 

Nelson (16, 39) reported a method of making polyurethane-foam composites by means of the SRIM process. Two different types of polyurethane materials were used an amine-modified polyurethane suitable for static elastomer uses and a polyurethane material with high crosslink density designed for use as a microcellular structural material. 

Nelson investigated the relationship between density and physical properties, e.g., flexural modulus, Gardner impact, heat distortion, ten-sile/flexural strength, coefficient of linear thermal expansion, dynamic mechanical testing, and creep testing. The specific gravity of the SRIM obtained was changed from about 0.3 to 1.2. 

Kuyzin et al discussed a low-density SRIM made by using glass-fiber reinforcement and a urethane-modified isocyanurate foam system (26), or by using polyamide-coated polyester fibers and a urethane-modified isocyanurate-foam system (36). 

Table 47 shows typical material and jH ocess conditions for Elastolit SR low-density SRIM systems (36), and Table 48 shows the general mechanical ju operties for an Elastolit SR low-density SRIM system for interior trim applications. Elastolit is a trade mark for BASFs SRIM system (36). 

Table 47 Typical Material and Process for ElastoUt SR Low Density SRIM Systems (36) ...

Table 48 Approximate Mechanical Properties for an ElastoUt SR-Based Low Density SRIM System for Interior Trim Applications (with 13 wt % OCF Glass Mat Reinforcement of 1.5 mjt (36)...

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