( 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 magnesium stearate 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 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 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 PVC flame retardant 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 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.
From ethylene , propylene copolymer made of ethylene propylene rubber (EPR), an amorphous rubber, has good impact properties.
Nitrile rubber (NBR), generally used in acrylonitrile content of 26 % to 32 % of impact modifier .
Others include styrene-butadiene rubber , butadiene rubber , chloroprene rubber, butadiene rubber , etc., can be used as impact modifiers , General addition of 10% to 20%. Currently there are more commonly used ethylene-propylene rubber and nitrile rubber, for the modification of PVC, PP, HIPS, PS and other thermoplastic resins.
2 , processing modifier classification and species
① ACR: ACR is methyl methacrylate and acrylic acid ester copolymer. ACR has a core / shell structure of the polymers. Is a crosslinked butyl acrylate (BA) rubber-like polymer as the core and poly (methyl methacrylate) (PMMA) as the shell , the outer shell of his good compatibility with PVC, PMMA , and its inner layer of mild crosslinked core, the core and the shell or by a concentration gradient method of controlling with other polymers gradual transition , a transition layer is formed , so that the shell core and the compatibility is improved, which greatly improves the impact resistance results. It is not only the PVC processing modifier , impact modifier is a thermoplastic polyolefins and coupling agents . ACR models are more varieties .
ACR-201: white powder, the relative density of 1.05 to 1.20 , the particle size of 98 % passing 30 mesh . And close to the solubility parameter of PVC , it has good compatibility and moldability . As the PVC processing modifier generally ACR was 1% to 3%.
ACR-401: Appearance white powder, is methyl methacrylate, ethyl acrylate, butyl acrylate , styrene monomer is copolymerized four kinds . The molecular structure of the core-shell structure, molecular weight of 250,000 ~ 750,000 . Intrinsic viscosity of 0.5 to 1 Fineness 98% passed through a 40 mesh , the glass transition temperature of 54 ℃, the thermal decomposition temperature of 268 ℃, insoluble in water, soluble in acetone , methyl ethyl ketone . Non-toxic fire retardant.
Due to the crosslinked butyl acrylate rubber elastic body is formed as a shell structure , and therefore have good processing flowability and impact toughness.
② P-83: P-83 full name CHEMIGUM-P83, which is copolymer of butadiene and acrylonitrile , i.e., a new type of powdered nitrile rubber , a loose powder , has a special three-dimensional structure . Which is characterized by good compatibility with PVC , PVC overall improvement in performance. Improved processability , thermal stability , low temperature resistance , abrasion resistance , flexibility and the like .
And P-83 similar processing aids are: Canadian production KPYNAC-1122 and DuPont ELVALOY-741, 742 , etc.
③ poly- α- methylstyrene : the α- methylstyrene oligomer . Also known as AMS or R-18. Phenol and acetone production by-product , but also by cumene dehydrogenation. AMS molecular weight of 300 to 350 is liquid ; molecular weight of 700 to 1000 , known as M-80 resin , is brittle solid , a softening point of 93 ~ 105 ℃. AMS except for PVC , but also for the PU, PS, ABS and CPE and other cold weather processing modifier .
④ 820-G: is a chlorinated paraffin and polypropylene oxide - ethylene made by free radical grafting of flame retardant a surfactant , and a silane coupling agent after the chlorine composed of surface-treated carrier . Can significantly improve the processability of rigid PVC , and when adding 10 % to 15 %, the impact strength can be improved and increased surface gloss , replace part of ACR, that the products costs.
⑤ NPA: a polyolefin resin, a fluorine-containing resin , silicone , waxes and other preparation . NPA-6, NPA-8 is a linear low density polyethylene processing aids , the appearance of a white powder , melting at 105 ~ 110 ℃, molecular weight of 1,000 to 1,500 , a melt index of 50 ~ 55g/10min. NPA has a smoothness and processing mobility. Added amount is generally from 2% to 4%.
⑥ Many of the impact modifier MBS, ABS, CPE, EVA, SBS such as impact modifier , is processing modifier .
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