RTP 200E SI 2 is a compounded amorphous polyamide (Am. PA) containing a nominal 2% by weight silicone internal lubricant. The designation places the material within RTP Company’s 200-series amorphous nylon line, where “SI” denotes a silicone additive and “2” indicates the additive loading. The amorphous polyamide matrix does not exhibit a sharp crystalline melting point; it softens through a glass transition region, which gives the compound near-isotropic mold shrinkage, lower post-mold warpage, and a different thermal profile than semi-crystalline polyamides such as nylon 6 or nylon 6/6. Product-specific values for RTP 200E SI 2 are available from the manufacturer’s current data sheet, which is typically structured around mechanical, thermal, rheological, and tribological test methods. The silicone in “SI 2” is not a surface coating; it is distributed through the polymer melt during compounding and is intended to migrate slowly to the part surface during use.

An amorphous polyamide of this class is usually selected where dimensional stability, low anisotropic shrinkage, and reduced warpage are more important than the high crystallinity and solvent resistance of nylon 6/6. The silicone additive modifies surface and wear behavior. In sliding contact, the migrating silicone film reduces static coefficient of friction and can suppress stick-slip noise. However, the low-energy surface also reduces adhesion for bonding, coating, and printing. Bond strength should be verified after surface treatment by a cross-cut or peel method such as ASTM D3359-23 or ISO 2409:2020 before post-mold decoration is specified.

When a 2% Silicone Modifier Is Compounded into an Amorphous Polyamide Matrix

At the compounding stage, the silicone is typically introduced downstream in a co-rotating intermeshing twin-screw extruder with an L/D ratio of at least 40:1 and vacuum venting. Downstream feeding prevents the full thermal history of the base resin from degrading the silicone phase and minimizes phase inversion. On similar amorphous nylon compounds, side feeding after the primary melt seal and before the vacuum vent maintains a fine dispersed-silicone domain structure. The downstream vent is critical because low-volatile silicone carriers can otherwise create splay in molded parts. Process records on related compounds indicate that within-lot coefficient of friction variation is influenced more by screw temperature profile than by total throughput, because silicone migration depends on thermal mobility and not merely on additive concentration.

Pre-drying follows amorphous polyamide handling practice. Intrinsic moisture content should be reduced to below 0.10% before molding. Desiccant dryers with a dew point of −40°C or lower are specified, and drying at 80°C for 4 h is common for amorphous nylon grades, though the manufacturer’s recommended time and temperature must govern. If open hoppers are exposed to relative humidity above 60%, hydrolysis of the polyamide chain can occur during melt processing, producing lower melt viscosity, gas splay, and reduced tensile elongation. Closed feed-throat dryers and dry-air conveying are used when ambient humidity exceeds 60%.

The barrel temperature profile for amorphous polyamides is usually higher and narrower than for crystalline nylon 6/6. Prolonged melt residence above 300°C should be avoided, and residence time at upper melt temperatures should not exceed 15 min unless documented on the production line. Mold temperatures of 80°C to 120°C are commonly required to reduce molded-in stress and to allow the amorphous polymer to relax before cooling below its glass transition. Because the material does not crystallize, the holding-pressure profile must control gate freeze rather than pack against a crystallization plateau. Injection molders transitioning from nylon 6/6 should not expect the same cavity-pressure decay signature; the amorphous melt remains more temperature-responsive than crystallization-driven, so gate-seal time must be established from melt-pressure curve data rather than by crystallinity-based assumptions.

What Test Standards Govern the Published Property Set for RTP 200E SI 2?

Published property values for amorphous polyamide compounds are meaningful only when specimen type, conditioning history, and test speed are held constant. Mechanical specimens are generally injection molded according to ASTM D3641-21 and conditioned at 23 ± 2°C and 50 ± 5% relative humidity for 40 h in accordance with ASTM D618-21 before testing. The following matrix lists the standard methods that appear in typical RTP Company product data sheets for the 200-series amorphous nylon family. Specific values for RTP 200E SI 2 are not reproduced in this document because current lot data and datasheet revisions are held by the manufacturer; the matrix is provided as an inspection and validation reference.

ASTM D1894-14 and ISO 8295:1995 are planar sliding tests and do not provide wear-rate data. ASTM D3702-94(2019) uses a thrust washer configuration that applies a prescribed end-load and rotational speed; it yields both wear factor and friction in self-lubricating rubbing contact. A low coefficient of friction in ASTM D1894 does not predict low wear under ASTM D3702 because contact geometry and surface replenishment of the silicone film differ. Validation programs should therefore specify both methods when wear is critical. Break-in time in a thrust washer test can be 1–4 h for related silicone-modified amorphous polyamides before a stable transfer film develops, so short-duration tests may overestimate wear.

By comparison with unmodified amorphous nylon, RTP 200E SI 2 provides a lower static coefficient of friction and lower ejection force, but the addition of a soft silicone phase can modestly reduce tensile modulus and tensile strength. The actual difference is grade-specific and should be read from the supplier’s data sheet. The silicone phase also changes the fracture surface; impact energy absorption may be retained because the amorphous matrix can promote ductile deformation, but unmodified amorphous nylons remain more notch-sensitive than impact-modified crystalline grades. Components with sharp corners should therefore be evaluated for notched Izod impact under ASTM D256-23 at the intended operating temperature.

In relation to PTFE-containing amorphous nylon, the silicone system typically offers lower specific gravity and less visible transfer layer, but it may have a lower pressure-velocity limit in continuous sliding. The comparison should be made using ASTM D3702-94(2019) wear factor tests at the same contact pressure and speed. Published data for this specific configuration is limited, so product-versus-product screening on the final part geometry is required before substitution. PTFE is generally preferred when dry-running bearings operate at higher surface speeds; silicone is often evaluated when the dominant requirement is low stick-slip, quiet motion, or mold release with cosmetic surfaces.

Against semi-crystalline nylon 6/6, the amorphous polyamide base of RTP 200E SI 2 produces lower isotropic mold shrinkage and less warpage in large-area parts. Semi-crystalline nylon 6/6 has a narrow crystallization temperature and a sharp melt transition, while the amorphous grade has no crystallization peak. This difference removes differential shrinkage associated with crystalline skin-core morphology, but it also changes chemical resistance. Amorphous polyamides are often more susceptible to polar organic solvents, strong acids, and alcohol-based cleaners than semi-crystalline nylons. Chemical compatibility should be confirmed through ASTM D543-21 immersion testing for 1,000 h at the maximum service temperature, with mechanical retention measured by ASTM D638-22.

In fluid-contact applications such as sensor housings or pump wear components, hygroscopic expansion must be accounted for. Amorphous polyamides absorb moisture to a grade-specific equilibrium level under high relative humidity, and uptake is measured by ISO 62:2008. The 2% silicone phase does not eliminate moisture uptake, although it can reduce surface coefficient of friction in high-humidity environments. Dimensional stability after exposure can be assessed by ISO 62:2008, but part-level validation should also include thermal humidity cycling. Linear thermal expansion values are grade-specific and are measured by ISO 11359-2:2021.

RTP 200E SI 2 is unfilled; it does not contain glass fiber, carbon fiber, or mineral reinforcement. The absence of reinforcement gives the compound more ductility in thin-wall sections but lower tensile modulus and higher coefficient of thermal expansion than glass-fiber-reinforced amorphous nylon grades. If load-bearing or creep resistance is required, creep testing under ISO 899-1:2017 at the service temperature and load is required because amorphous nylons can creep at elevated temperatures even below the glass transition. Spiral flow and thin-wall filling should not be based on nylon 6/6 viscosity data; capillary rheometry according to ISO 11443:2021 at shear rates from 100 s⁻¹ to 10,000 s⁻¹ is more useful for injection molding simulation. The presence of 2% silicone can slightly reduce screw torque and melt pressure at high shear rates in related formulations.

Mold designers evaluating RTP 200E SI 2 should use the manufacturer’s parallel and normal shrinkage values rather than substituting nylon 6/6 data. Amorphous nylon mold shrinkage is typically less than 0.6%, while nylon 6/6 can shrink between 1.0% and 2.0% depending on orientation and wall thickness. These are class-level ranges and are not grade-specific. Gates, runners, and cooling circuits should be sized for a melt that does not crystallize; hold pressure is maintained until gate freeze, and cooling time is governed by reaching a stable ejection temperature below the glass transition. Mold deposits from silicone migration can appear as a faint transparent film after several thousand cycles. On production lines, cleaning intervals for polished molds are better established by monitoring ejection force or cavity-pressure signature drift than by waiting for visible deposit.

Silicone migration makes pad printing, painting, and adhesive bonding less robust. Plasma, corona, or chemical adhesion promoters can raise surface energy, but adhesion must be verified by a cross-cut or peel test such as ASTM D3359-23, ISO 2409:2020, or ASTM D6862-11(2021). In laser welding or hot-plate welding, the migrating silicone can reduce weld factor; if structural welds are required, weld strength should be measured on welded specimens according to ISO 527-1:2019 or an equivalent weld standard. A lower-silicone or non-migrating lubricant should be evaluated when weld factors below the product requirement are unacceptable.

For food-contact, drinking-water, or medical applications, the final part must meet the relevant regulatory framework. Nylon resins may be listed under FDA 21 CFR 177.1500, but the specific compound with silicone additive must be confirmed by the manufacturer’s regulatory statement. EU 10/2011 food-contact compliance requires overall migration testing, and silicone may be subject to separate limits. No regulatory approval is assumed here; the supplier’s certificate should be tied to the specific lot and production site.

Before specifying RTP 200E SI 2 for a new application, the engineering evaluation should include moisture-conditioned mechanical testing, ASTM D1894-14 and ASTM D3702-94(2019) tribological screening, ASTM D543-21 chemical immersion, and part-level mold shrinkage verification. Published data for this specific configuration is limited; therefore, the manufacturer’s current datasheet and technical service group remain the authoritative source for lot-specific values, processing windows, and regulatory status.