( A ) impact modifiers and processing modifier function
1 , the performance of impact modifier
To improve the impact properties of plastic additives added for the purpose referred to as impact modifier . These additives can not only improve the impact strength of the resin , but also to improve the processability of the resin . Impact modifier is typically used in rigid PVC , but in polypropylene, polystyrene and modified plastics has universal application. Currently , rigid PVC impact modifier used mainly plastic flame retardant some copolymer resin or a modified resin such as ABS, MBS, EVA, CPE , and thermoplastic rubber , thermoplastic elastomers , which are widely used as PVC, PE, PP, PS, AS, ABS, PMMA, PA, PC, PBT, PET and so on. Impact modifier may be added into a ductile plastic brittle plastics can be applied only in the normal temperature of the plastic into a plastic used at low temperatures , in addition , can effectively improve the processing properties of plastics .
Ideal resistance modifier should have the following properties:
① and modification of the substrate must have a good compatibility.
② modifier particle size, morphology medium a diameter of about 200nm is appropriate to protect the effect is a high impact strength .
③ modifier to lower the glass transition temperature is preferred.
④ impact modifier preferably has slightly crosslinked to improve the reinforcing effect .
⑤ modifier processing properties of the resin without prejudice to its apparent performance and physical and mechanical properties without adverse effects.
⑥ requires non-toxic, non-polluting and affordable.
2 , the processing performance modifier
Processing modifier for plastic processing performance is poor and development of a class of additives that are added to improve the polymer in the molten resin flow , and a thermal stability, heat distortion resistance and surface gloss of the material products . Currently, the processing modifier is mainly to improve the melt viscosity of PVC , improved flowability and processability.
Processing modifier primarily polymer, the application is more acrylic copolymer , such as methyl methacrylate / acrylic acid copolymer system (MMA / FA system ) , methyl methacrylate / butyl methacrylate acrylate / ethyl acrylate / methyl methacrylate copolymer systems (MMA / BMA / EA / EMA system ) , methyl methacrylate / ethyl acrylate / acrylonitrile copolymer system (MMA / EA / AN system ), etc. The amount of resin added is usually from 3% to 8%.
( Two ) impact modifiers and processing modifier classification and species
1 , impact modifiers and species classification
① acrylonitrile - butadiene - styrene copolymer (ABS): ABS resin is a graft copolymer of polybutadiene latex is added to the styrene and acrylonitrile monomers copolymerized . Impact modifier for PVC, ABS has a good effect, the toughening effect, while the tensile Impact modifier for PVC strength and elongation decrease is small, the general amount of 10% to 20%. ABS resin due to the presence of unsaturated structures , weather is poor, so products should not be long-term outdoor use . ABS resin is less than the compatibility with PVC, MBS, the product transparency is not as good MBS copolymer ; such as a transparent ABS and PVC blends can obtain a transparent products. When the ABS dosage of 20% to 30 %, the impact strength with excellent results.
② methyl methacrylate - butadiene - styrene copolymer (MBS): MBS is to polybutadiene or butadiene - styrene emulsion , methyl methacrylate graft copolymerized . Adding MBS resin can improve the impact toughness of PVC , polyvinyl chloride increase the transparency , but poor aging resistance of MBS , MBS higher rubber content , the higher the impact toughness . MBS added amount is generally 10% to 17 % is appropriate, more than 30 % of the brittle failure occurs .
③ chlorinated polyethylene (CPE): chlorinated polyethylene of high density polyethylene (HDPE) chlorination , chlorine content is generally 30% to 45% , depending on the resin component , the chlorine content , the molecular structure and morphology different , showing a rigid plastic from the rubber elastic body in different state changes. Molecular weight of 1,000,000 or more CPE is not only good impact resistance , and excellent weather resistance , ABS and MBS overcome the shortcomings of poor weather . In addition , CPE chlorine in a great effect on the size of the modified , low chlorine content , its high crystallinity and poor toughness , high glass transition temperature , poor compatibility with PVC . Chlorine content is too high , CPE 's cohesion is stronger , but relatively poor dispersion . CPE in PVC dosage is generally 5% to 15%. CPE, cold resistance, chemical stability , flame resistance, oil resistance and electrical insulating properties are good .
④ ethylene - vinyl acetate copolymer (EVA): EVA used as modifiers of PVC , the vinyl acetate content should be more than 40 ¥ . EVA good weather resistance, modified PVC products can be used outdoors, but the transparency and tensile strength have declined. The addition of EVA is generally 5% ~ 10%, EVA as the modifier , also be used in the dibasic lead stearate modified polyolefins , to improve weatherability , cold resistance .
⑤ styrene - butadiene = styrene copolymer (SBS): used mainly to change HIPS, PP, PS toughening , cold and impact strength . Added amount is generally 5 % to 10 %, can greatly improve the low temperature impact toughness .
⑥ synthetic rubber and thermoplastic elastomer impact modifier : synthetic rubber and thermoplastic elastomers have excellent toughness, flexibility , high elasticity and excellent low temperature performance, itself has good impact resistance , good impact resistance is changed Xing agent.
POE is an ethylene / octene copolymers, as PE, PP, PA impact modifier to good effect in toughening the same time, to lower rigidity .
EPDM rubber (EPDM), has good flexibility, elasticity , tear resistance , acid and alkali , weather resistance and impact resistance.
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