Colloidal silica processing aid slashes molding cycle times.Ultra-fine synthetic silica silica or silicon dioxide, chemical compound, SiO2. It is insoluble in water, slightly soluble in alkalies, and soluble in dilute hydrofluoric acid. Pure silica is colorless to white. particles have been shown in laboratory and commercial field trials to reduce injection molding injection molding n. A manufacturing process for forming objects, as of plastic or metal, by heating the molding material to a fluid state and injecting it into a mold. cycle times by 20% to 30% in polypropylene polypropylene (pŏl'ēprō`pəlēn), plastic noted for its light weight, being less dense than water; it is a polymer of propylene. It resists moisture, oils, and solvents. , filled and unfilled nylon, PBT PBT Provider Backbone Transport (networking technology adding determinism to ethernet) PBT Polybutylene Terephthalate PBT Profit Before Tax PBT Paper Based Test (education) , and ABS (Automatic Backup System) See backup program. . This processing advantage is accompanied by retention and even improvement of key physical properties. Other reported benefits are improved color dispersion dispersion, in chemistry dispersion, in chemistry, mixture in which fine particles of one substance are scattered throughout another substance. A dispersion is classed as a suspension, colloid, or solution. and reduced flow lines and surface defects. What's more, the silica additive additive In foods, any of various chemical substances added to produce desirable effects. Additives include such substances as artificial or natural colourings and flavourings; stabilizers, emulsifiers, and thickeners; preservatives and humectants (moisture-retainers); and is said to mix easily with resin pellets in a blender, so melt pre-compounding is not required. Nan-O-Sil ASD ASD abbr. atrial septal defect ASD Atrial septal defect, see there additive is high-purity, amorphous Unorganized or vague. A lack of structure. For example, the amorphous state of a spot on a rewritable optical disc means that the laser beam will not be reflected from it, which is in contrast to a crystalline state which will reflect light. See crystalline. , colloidal colloidal of the nature of a colloid. colloidal bath a bath containing gelatin, bran, starch or similar substances, to relieve skin irritation and pruritus. silica in the form of a white powder. The spherical spher·i·cal adj. Having the shape of or approximating a sphere; globular. particles range in size from 0.02 to 0.55 microns (20 to 550 nanometers). Nan-O-Sil ASD is manufactured and marketed by Energy Strategy Associates, Inc., which has been working with technical consulting and R&D firm RheoPlast Associates to develop applications for this additive. Headed by Dr. Pravin L. Shah, Rheo-Plast specializes in polymer rheology and its application to extrusion, injection molding, and compounding of engineering plastics and blends/alloys. Rheo-Plast conducted laboratory testing of Nan-O-Sil in a variety of resins. Dr. Shah supplied the test results to PLASTICS TECHNOLOGY for this article. EXPERIMENTAL RESULTS Injection molded sample bars were obtained by first tumbling resin pellets with Nan-O-Sil ASD for 15 min in a Conair blender. The additive coated the pellets well and uniformly, Shah reports. The most dramatic results with Nan-O-Sil ASD are the cycle-time reductions for PP, unfilled nylon 6, glass-filled nylon 66, unfilled PBT, and ABS (see Table 1). The additive also shows utility as a reinforcing filler fill·er 1 n. One that fills, as: a. Something added to augment weight or size or fill space. b. A composition, especially a semisolid that hardens on drying, used to fill pores, cracks, or holes in wood, plaster, that can raise the stiffness of PP and both stiffness and strength of nylon 6 and PBT (Tables 2 to 5). Depending on the resin and the amount of Nan-O-Sil used, there was little or no sacrifice of other properties, such as elongation elongation, in astronomy, the angular distance between two points in the sky as measured from a third point. The elongation of a planet is usually measured as the angular distance from the sun to the planet as measured from the earth. or toughness. In glass-filled nylons, using larger amounts of Nan-O-Sil ASD appears to have potential for reducing the amount of glass fiber required to improve strength and stiffness. One trial compared the physical properties of 13% glass or 10% Nan-O-Sil in nylon 6. As shown in Table 4, colloidal silica imparted a greater increase in tensile strength tensile strength Ratio of the maximum load a material can support without fracture when being stretched to the original area of a cross section of the material. When stresses less than the tensile strength are removed, a material completely or partially returns to its and flexural flexural pertaining to the flexure of a joint. flexural deformity fixation of joints in flexion. In the newborn called contracted calves or foals. modulus See modulo. than did the glass fiber. According to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. Shah, an in-depth study of combinations of Nan-O-Sil ASD and glass fiber is under way and results will be published next year. HOW IT WORKS Although the precise mechanism by which Nan-O-Sil ASD reduces cycle times and improves strength properties of molded plastics is still unclear, Shah says the additive has been shown to work at low addition levels of 0.4% to 0.8% as a heat sink A material that absorbs heat. Typically made of aluminum, heat sinks are widely used in amplifiers and other electronic devices that build up heat. Small heat sinks are the most economical method for cooling microprocessors and other chips. to reduce the amount of cooling required during molding. Based on Brabender torque rheometer rhe·om·e·ter n. An instrument for measuring the flow of viscous liquids, such as blood. data, he also postulates that the additive works as a processing aid to reduce the shear gradient gradient In mathematics, a differential operator applied to a three-dimensional vector-valued function to yield a vector whose three components are the partial derivatives of the function with respect to its three variables. The symbol for gradient is ∇. at the gate and facilitate melt flow orientation. Also not clearly understood at present is the apparent melting-point depression observed in PP, though no such effect was evident in nylon. Further work is under way to determine the additive's behavior in melt processing. CONTACT SUPPLIERS For more information on these companies and their products, visit www.ptonline.com/suppliers Energy Strategy Associates Inc., Old Chatham, NY (518) 794-0082 * www.nanosilasd.com Rheo-Plast Associates, Inc., Reading, PA (610) 678-1260 * www.rheopastusa.com By Lilli Manolis Sherman, Senior Editor
TABLE 1--
FASTER INJECTION MOLDING CYCLES WITH NAN-O-SIL ASD
Material w/ Avg. Cycle Time
0.8% Nan-O-Sil Reduction
PP, unfilled 22%
Nylon 6, unfilled 24%
Nylon 66, 33% glass 32%
PBT, unfilled 26%
ABS, unfilled 25%
TABLE 2--
NAN-O-SIL ALSO IN POLYDPROPYLENE
Tensile Str. Elongation Tensile
@ Yield @ Yield Mod.,
Material psi % psi
PIP Control 3000 9.7 145,000
PP/0.40/0 Nan-O-Sil 3020 8.9 151,000
PP/0.80% Nan-O-Sil 2930 8.2 144,000
Gardner Flexural Flex.
impact Modulus Str.,
Material in.-lb/in. psi psi
PIP Control 2.18 112,000 3350
PP/0.40/0 Nan-O-Sil 2.15 122,000 3570
PP/0.80% Nan-O-Sil 2.12 118,000 3520
MFI, Melt
g/10 Point,
Material min C
PIP Control 8.0 168
PP/0.40/0 Nan-O-Sil 8.2 163
PP/0.80% Nan-O-Sil 8.3 160
TABLE 3--
NAN-O-SIL ASD IN NYLON 6
Tens. Str. Elongation Tensile
@ Yield, @ Yield, Mod.,
Material psi % psi
Nylon 6 Control 8710 4.5 315,000
Nylon 6 + 0.4% Nan-O-Sil 8760 4.5 320,000
Nylon 6 + 0.8% Nan-O-Sil 9020 4.6 320,000
Gardner Flexural
Impact, Modulus,
Material in.-lb/in. psi
Nylon 6 Control 2.18 224,000
Nylon 6 + 0.4% Nan-O-Sil 2.18 227,000
Nylon 6 + 0.8% Nan-O-Sil 2.15 237,000
Flexural HDT @
Strength, 66 psi,
Material psi F
Nylon 6 Control 9300 140
Nylon 6 + 0.4% Nan-O-Sil 9330 140
Nylon 6 + 0.8% Nan-O-Sil 9840 140
TABLE 4--
NAN-O-SIL ASD VS. GLASS FIBER IN NYLON 6
Tens. Str. Elongation Tensile
@ Yield, @ Yield, Mod.,
Material psi % psi
Nylon 6 Control 8710 4.5 315,000
Nylon 6 + 13% Glass 8760 4.5 320,000
Nylon 6 + 10% Nan-O-Sil 9020 4.6 320,000
Gardner Flexural
Impact, Modulus,
Material in.-lb/in. psi
Nylon 6 Control 2.18 224,000
Nylon 6 + 13% Glass 2.18 227,000
Nylon 6 + 10% Nan-O-Sil 2.15 237,000
Flexural HDT @
Strength, 66 psi,
Material psi F
Nylon 6 Control 9300 140
Nylon 6 + 13% Glass 9330 140
Nylon 6 + 10% Nan-O-Sil 9840 140
TABLE 5--
NAN-O-SIL ASD IN PBT
Tens. Str. Elongation Tensile
@ Yield, @ Yield, Mod.,
Material psi % psi
PBT Control 7400 3.6 145,000
PBT+ 0.4% Nan-O-Sil 7400 3.4 151,000
PBT+ 0.8% Nan-O-Sil 7600 3.2 144,000
Gardner Flexural
Impact, Modulus,
Material in.-lb/in. psi
PBT Control 2.18 355,000
PBT+ 0.4% Nan-O-Sil 2.14 374,000
PBT+ 0.8% Nan-O-Sil 2.10 380,000
Flexural HDT @
Strength, 66 psi,
Material psi F
PBT Control 3350 8
PBT+ 0.4% Nan-O-Sil 3570 8.2
PBT+ 0.8% Nan-O-Sil 3520 8.1
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