Lubrication RPSexdoll (physical doll) must select an adaptation plan based on the material properties, thermoplastic elastomer (TPE) material is suggested to utilize a viscosity of 350-450mPa·s water-based lubricant, its pH value shall be rigidly controlled between the scope of 6.5-7.2. Test data show that silicone lubricants will increase TPE expansion rate 2%-3% (mass change rate ±0.8%), and medical grade mineral oil (kinematic viscosity at 40℃ 22-25mm²/s) will lower the friction coefficient of joints from 0.65 to 0.38, extending skeleton bearings’ service life by 32%. Dollfie Dream’s official Japanese maintenance guide makes it very obvious that the lubricant per square centimeter has to be within 0.02-0.03mL accuracy, and more than 0.05mL/cm² use will raise the material’s porosity by 15% and the aging rate by 1.5 times. During the year 2023, the mixed lubricant with 2% polydimethylsiloxane remained adhered to the surface of TPE up to 98%, the time taken for continuous lubrication was increased to 72 hours, and the efficiency of the pure water-based product improved by 240%.
In cost saving, the price of 100mL food grade lubricant is 8−12, every maintenance requires approximately 5mL, and the unit price is 0.4−0.6, which represents 92% saving compared to the return lubrication service ($50/time). Statistics obtained from RealDoll USA indicate that using SILICOO™ silicone lubricant (viscosity index 160), specialized for rpsexdoll, restored hip motion Angle from 110° to 145°, and maintenance rate of load capacity (to 50kg) from 78% to 95%. When it is working, it must be evenly distributed in a circulating direction (rotating speed 30-40rpm) so as not to allow the local pressure exceed 0.3MPa, otherwise the micro-crack generation rate will increase by 19%. A report from Dongguan foundry in China shows that addition of a lubricant with nanoscale graphene additives (0.5% concentration) is able to increase the surface wear resistance of TPE by 40% and reduce the peak frictional heat temperature from 42 ° C to 29 ° C.
Safety risk control should be based on chemical compatibility, glycerin content of lubricant more than 10% will increase swelling rate of silicone material by 1.8%, and propylene glycol concentration higher than 5% can lead to the increase of TPE hardness (Shore A) by 3-5 degrees. In accordance with EU EN 71-3 regulation, heavy metal migration value of lubricant should be lower than cadmium ≤75mg/kg and lead ≤90mg/kg. Synthetics Lab based in Korea has developed a pH self-regulating lubricant (buffer range 6.8±0.2) which has reduced the risk of material damage from 12% to 1.5% employing ion exchange technology, and antibacterial rate (E. coli) is 99.9%. The smart lubrication system unveiled at CES 2024 is equipped with a microflow pump (accuracy ±0.01mL) and an infrared sensor that can monitor the thickness of the lubricating layer in real time (target value 50-80μm) with an error control within ±5μm.
In terms of temperature and environmental conditions, lubrication operation should be performed at 20-25 ° C and relative humidity 45%-55%RH, temperature above 35 ° C will accelerate the evaporation rate of the lubricant by 3 times, while temperature below 10 ° C will increase the viscosity by more than 200%. Comparative trials with Abyss Creations in the United Kingdom showed that lubricant warming to 30 ° C would deliver an improvement in penetration depth by 0.2mm and reduce the resistance to motion of the joints by 18%. It is pointed out that the lubrication flow rate (flow rate ≤2mL/s) of RPSexdoll cavity structure needs to be regulated by a dropper, otherwise 67% risk of residual liquid accumulation will take place, which may lead to microbial breeding (total number of colonies >10³ CFU/g). Market trends are that in 2023 the global RPSexdoll special lubricant market size is $120 million, self-healing microcapsules (5-10μm diameter) product growth rate is 27%, rupture release lubricant’s response pressure threshold is 0.15-0.2MPa, and this exactly matches the conditions for daily use.