Biaxial rotation

Slow rotation gives the most uniform products. The pattern of biaxial rotation must be determined by trial and error. Heating is best done in a gas-fired oven with a fan for circulation. 

According to the test, five specimens (each 50 mm long, 100 mm wide, and 1 mm thick) are conditioned at ambient temperature as specified in the test, and placed in a forced draft oven equipped with a biaxial rotator. Specimens should be attached to the rotator by metal slips lined with fluoropolymer film and should not directly contact with the metal clips or metal parts of the oven. The frequency of rotation about the horizontal and vertical axes of the rotator should be 1-3 min . The time to failure is determined by regular visual examination of the specimens as the number of days after which the specimen shows localized crazing, crumbling, or discoloration, or a combination thereof. According to the standard procedure, the oven temperature shall be 150°C (302°F). 

ASTM D.1012. Thermal-oxidative stability of propylene plastics using a biaxial rotator. 1995. 

Fig. II. Biaxial rotation fatigue. (a,b) Thick polyester fibre, (c) Finer polyester fibre. For further explanation, see Fig. I.

Fi)i. 13. (a) Final stages of wear multiple splitting leads to rounded ends. Wool/polyester jaeket. (b,e) Direct breaks of nylon after a few eyelcs of severe biaxial rotation testing. For further explanation, see Fig. 1. 

Finally, although it is of more academie than praetieal interest, the complicated modes of deformation that can occur in fibres are shown by some breaks in the biaxial rotation test with a high angle of wrap round the pins. This generates high torque forces and probably some heating. Bulbous zones of disorientation are formed and direct breaks occur in a few cycles in very curious forms. Fig. 13b,c. 

Rotational moulding is one of the plastic processing methods for the production of hollow plastic products. Plastic powder is charged and subjected to biaxial rotation in an oven at a temperature of 200- 00 °C. The plastic powder melts inside the mould by heat transferred via convection through the mould wall. All the powder melts and the mould is moved out of the oven while maintaining the biaxial orientation. Exposure to air, or using a fan or water shower are usually employed to cool the mould. 

Polypropylene Plastics Using a Biaxial Rotator D4803 Test Method for Predicting Heat Buildup in PVC... 

Rotational molding. A thermoplastic powder is used in this method to which glass reinforcements in the form of chopped strands are added. The resin powder and glass reinforcement are charged into a split hollow mold, heated, and biaxially rotated. After the material has fused, the mold is cooled, opened, and the part removed. 

The use of biaxial rotation and heat for materials fabrication dates to R. Peters of Britain in 1855 for the manufacture of hollow artillery shells [41,42]. Rotational molding of polyethylene started in the early 1950s. 

Rotating specimens on rotary trays and/or attaching specimens to carrier wheels with a rotational period of 1 to several minutes. Ovens are available both with specimen holders rotating around a horizontal axis as well as with biaxial rotators ("Ferris wheels ), as described in ASTM D 3012 [239] for testing polypropylene. 

At first glance, rotational molding is a relatively simple process. It utilizes high molding temperatures, thin-walled metal or composite molds, biaxial rotation in two perpendicular axes, finely divided powder or liquid polymers, and cooling using air and/or water to produce hollow, seamless parts with relatively low levels of molded-in stress. 

Biaxial rotation Biaxial rotation is created by simultaneously turning the mold 360 degree in both the horizontal (major) and the vertical (minor) axis. The mold is mounted on an arm assembly that is geared to allow rotation on both axes. 

The most common form of molding is using biaxial rotation and there are two styles of arms commonly used for creating this motion straight and offset (dropped) arms (Figs. 15.12,15.13, and 15.14). 

Figure 9.2 An example of a biaxial rotational molding machine.

Figure 6. Optical photographs of rotomolded boxes from biaxial rotational molding.

Figure 7. Comparison of maximum stress of the biaxial rotationally molded LPP and LLDPE molded parts.

Rotational molding experiments were conducted on two separate machines - a uniaxial and a biaxial rotational... 

A ZN-PE was rotomolded on the biaxial rotational molding machine at different heating times and oven temperatures. Table 3 demonstrates the effect of different oven time on the percent crystallinity and roughness values for ZN-PE molded parts. A general trend can be seen. With increasing oven time the crystallinity and... 

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