Application of ACR low temperature impact modifier
PVC plastic doors and windows have been widely used because of their excellent properties of heat preservation, noise reduction and sealing. Especially in cold regions and areas prone to sandstorms, the full display of incomparable advantages. However, PVC window plastic after years of use also exposed a certain weakness, such as low-temperature impact resistance, cracking, aging and other problems.
Application of impact modifier at home and abroad
Since the introduction of PVC plastic doors and windows manufacturing technology in 1980s, the impact modifier is mainly CPE, and the production capacity of our country is very strong, the output is large, there is a trend of supply exceeding demand. Therefore, the domestic production of PVC window profile enterprises using CPE impact modifier is very common. Due to the fierce market competition in the production of CPE, individual manufacturers win by quantity and neglect product quality, which affects the stability of product quality in some PVC window profile production enterprises. If the thermal deformation temperature decreases, the process is unstable, and the impact property fluctuates with the quality of CPE, which directly affects the quality of PVC plastic window. Although many technicians have noticed some problems such as the low temperature impact resistance of PVC plastic window in the formulation design, the effect is not obvious because CPE is always used as modifier to improve the low temperature impact resistance. The appearance of the impact modifier ACR made in China has obviously improved the impact resistance of PVC plastic window at low temperature Since the 1990s, with the increase of the output of acrylate in our country, the cost has decreased and more PVC window profiles have been adopted. The advantages of ACR are more and more obvious in improving the low temperature impact resistance of PVC, reducing the cracking and improving the aging and color change. At present, the impact modifier used abroad, especially in Europe, is mainly ACR, which is obviously better than CPE as modifier. Therefore, the application of ACR is an important way to improve the performance of PVC plastic window.
Selection of impact modifier
The selection of impact modifier should pay attention to the following aspects:
1. The compatibility with PVC resin should be moderate. If the compatibility is too large, the two kinds of mixed materials will be in molecular level. The impact modifier may act as a plasticizer and adhere closely to PVC molecules, so that the impact force acts directly on the PVC chain Does not improve the impact of the role. On the contrary, if the compatibility is too small to reach uniform dispersion, lost the adhesion to PVC, can not absorb the impact force.
2. Low glass transition temperature can improve the impact resistance of PVC at low temperature.
3. The molecular weight should be high, if necessary, it is better to cross-link slightly in order to improve the enhancement effect.
4. It has no obvious effect on the performance and physical properties of PVC.
5, weather resistance to be good, die expansion is small.
6, and PVC blending process is good.
7. Good heat resistance (resistance to deformation, heat stability) .
Properties and application of acrylate series impact modifier
As the ACRYLATE is a "core-shell" structural elastomer, it is endowed with a series of advantages:
EXCELLENT IMPACT RESISTANCE
The impact resistance of "core-shell" structure is better than that of Network Structure Polymers (CPE, Eva) . As far as the glass transition temperature is concerned, CPE IS-10 °C ~-20 °C and the acrylate can reach-56 °C, so the low temperature impact property of CPE is obviously better than that of CPE. The newly developed AIM-50 glass transition temperature can reach above-60 °C, which can improve the low-temperature impact property of profiles significantly.
Wide Range of processing technology, STABLE OPERATION PROCESS
The processing temperature range of CPE is narrow, because the structure of CPE is close to that of PVC, the temperature is high (185 °C) , the blending property is good, and the network structure is easy to be destroyed. If the temperature is low, the plasticization is not good, the dispersion is not good, also affects the impact, appearance and other properties, but the acrylate impact modifier does not have the above problems, processing temperature is wide, easy to operate, high yield, good production stability.
Low thermal shrinkage, dimensional stability
The shrinkage of P v C profiles using ACR impact modifier is generally lower than 1.5% at 100 °C for 60 minutes. CPE is higher, generally above 1.5% (standard requirement ≤2.5%) . The practical significance of this project is to examine the Longitudinal stresses in PVC profiles. The influence factors of Longitudinal stress are the degree of plasticized gelation and the speed of technology traction. Therefore, the residual stress between the molecules is too large and local concentration is the main reason for the stress cracking of PVC profiles. The impact modifier ACR has an obvious effect on improving the stress cracking of profiles, and has less cracking in low temperature assembling.
It is suitable for high speed extrusion of profiles and has the function of flowing modifier
ACR impact modifier has reasonable physical structure, so it has wide processing range, fast extrusion speed, high shearing speed and suitable for high speed extrusion. The melting temperature is low, and the fluidity is good, so the ACR flow modifier can be saved and the cost can be reduced.
The product has a good surface gloss
ACR is easy to plasticize, low melt strength and High Gel degree, so the product surface gloss is high. The results showed that the gloss of modified CPE was between 20% and 40% , while that of modified ACR was between 40% and 65% .
Increase the strength of the Weld Angle
The application of ACR can improve the plasticizing property, improve the bulk property of PVC profile, and improve the welding strength because of the wide processing temperature and strong adaptability, so the welding angle strength is obviously improved.
The weather resistance of PVC profile is improved
At present, the dimming and yellowing of PVC profiles using Cpe anti-impact system occur in different degrees, which is directly related to CPE. The Whiteness of CPE irradiated by UV light changed greatly, reaching 50% , while the change of ACR was only 30% . Therefore seriously affects the appearance color change of PVC profile. The use of ACR is an important way to improve weather resistance and anti-photoaging color change.