Matters Needing Attention in the Design of Toughening Formula
Publish Time: 2018-12-04 Origin: Site
1. The compatibility between elastomer and resin should be good.
The polarity of plastics is:
Cellulose plastics > PA > PF > EP > PVC > EVA > PS > PP/HDPE/LDPE/LLDPE;
The polarity of the elastomer is:
Butadiene > Chloroprene > butadiene > cis-butadiene > natural rubber > ethylpropyl.
High polarity resin is used as high polarity elastomer and low polar resin is used as low polarity elastomer.
2. Compatibilizer: a suitable compatibilizer can improve the compatibility of both. The commonly used compatibilizers are maleic anhydride or acrylic acid grafted with resin or toughener.
3. Synergistic effect of elastomer: different varieties of elastomer have synergistic effect when added together, for example, in PP toughening formula, EPDM and ABS have good toughening effect.
4. Other factors to be considered: transparent grade —— MBS; flame retardant grade—— CPE, ACR, EVA; low cost—— CPE and EVA; The order of prices of different elastomers is MBS > ACR > ABS > NBR > CPE > EVA.
5. Rigidity compensation: in order to compensate for the loss of rigidity, the rigid fillers such as calcium carbonate, talc powder and mica powder should be added to the formula, and rigid organic resins such as AS,PMMA can be added to the toughening system of elastomer.
6. The amount of elastomer: in general, the amount of elastomer has an optimal value. If MBS is added to PVC, the maximum amount is 15%.
7. Synergistic addition of processing aids: for the toughening formula with large amount of elastomer, the viscosity of melt can be increased except ACR elastomer. Therefore, lubricant or processing aids are needed to improve the processing performance.
8. The particle size of elastomer: the particle size of elastomer has great influence on toughening effect. According to the toughening theory of elastomer, the particle size of brittle resin such as PS,PP can be relatively larger, but for better toughness resin such as PVC,POM,PET, the particle size of elastomer can be relatively small.