Acetonite-treated acicular wollastonite can improve the hydrophilicity of wollastonite and improve the dispersibility of wollastonite in polypropylene resin. The properties of the polypropylene material after filling are improved in terms of tensile strength, flexural strength, elastic modulus and flexural modulus, and slightly decrease in toughness. While the material temperature resistance has been greatly improved.

Key words: acicular wollastonite polypropylene thermal deformation temperature

Polypropylene Engineering Fiber

Wollastonite [CaSiO3 or Ca3 (Si3O9)] belongs to the metasilicate mineral, the theoretical chemical composition (mass fraction) is 48.3% CaO, 51.7% SiO2. Wollastonite is usually needle-like, radial, fibrous aggregates. In the crystalline structure of wollastonite, the SiO4 tetrahedral and CaO6 octahedral columns are connected in the b-axis direction. The composite single-stranded by the CaO octahedral column and the SiO backbone is the basic unit of the wollastonite crystal structure. Special crystal morphology, high whiteness, good dielectric properties and high heat resistance properties, so wollastonite can be widely used in rubber, ceramics, plastics, coatings and paper and other fields. At present, with the vigorous development of the plastics industry, plastic applications continue to expand. However, polypropylene as one of the five major synthetic resin in an important variety, at home and abroad are very rapid development. In the global plastics with five synthetic resin, the production of polypropylene accounted for about 1/4 of the share, in 2006 the world's five major synthetic resin production capacity will reach 190 million tons, of which 48.78 million tons of polypropylene, the total capacity Of 25.6%. It is expected that the amount of plastic in the next few years will increase year by year. Therefore, with the increasing application of plastic products in engineering, the research on the application of plastic modification is deepening.

Polypropylene Engineering Fiber

Experimental methods and processes

As the wollastonite inorganic non-metallic materials, and organic polymer material compatibility is poor, directly applied to the polymer when the filling effect is not obvious or even part of the material performance degradation, it must be surface modification treatment Improve its hydrophobic pro-organic, so that the powder can be better in the polypropylene resin evenly dispersed and with the matrix material has a good affinity. Inorganic powder surface treatment Usually used in the surface modifier are: unsaturated organic acids, higher fatty acids and their salts, coupling agent. Coupling agents include silanes, titanates, aluminates, zirconates and aluminum-titanium composites. The long-term experimental study is ideal for silane coupling agents.

Polypropylene Engineering Fiber

Wollastonite Surface Modification

 Will be weighed wollastonite into the high-speed mixer to start stirring and heating temperature, to be 80 ~ 100 ℃ temperature (different modifier activation temperature is different) required to add surface modifier to modify, the modification time is about 10min, can be determined by the modified powder oil absorption rate, sedimentation value and activation degree of indicators to evaluate its modification effect, this article does not explain and explain in detail.

Sample preparation

According to different experimental formula requirements will be modified wollastonite powder, PP resin added to the twin-screw extruder melt granulation, extruder process parameters: host speed 300r / min; traction speed 150r / min; head temperature of 200 ℃; The temperature of the section 1 ~ 9 is 170 ℃, 180 ℃, 190 ℃, 200 ℃, 210 ℃, 210 ℃, 210 ℃, 200 ℃; head temperature of 200 ℃; The granulated granules were dried in a blast oven at 95 ° C for 2 h and then injected into a standard sample with an injection molding machine to be tested.

Polypropylene Engineering Fiber

Performance Testing

Tensile performance test in accordance with GB / T1040-2006 test, the tensile rate of 50mm / min; bending performance test in accordance with GB / T9341-2000 test, bending rate of 2mm / min; heat distortion temperature in accordance with GB / T1634-2004 test.

Experimental results and discussion

Effect of Modified Wollastonite on Properties of PP Composites

It can be seen from Table 1 that the impact toughness of the composites decreases with the increase of the wollastonite content in the resin, but the decrease is not significant. The tensile strength, flexural strength, elastic modulus and flexural modulus The increase in content becomes larger. Wollastonite special needle-like fiber structure, so that the performance of the composite material is superior. Compared with the increasing content of wollastonite in the composites, the collision between the particles will increase. The result of the collision will break the part of the particles and destroy the needle-like structure, resulting in the decrease of the aspect ratio and the influence of the wollastonite The effect of enhancing the composite material.

Effect of Wollastonite Particle Size on Plastic Modification

Not only the amount of wollastonite added to the performance of composite materials, and wollastonite particle size will have a greater impact on material properties. From the data in Table 2, it can be seen that the contribution of wollastonite powder with different particle size is obviously different from that of PP modification: the larger the particle size of wollastonite is more obvious for the strength and rigidity of the material, the finer the particle size, When the diameter is relatively small, the contribution of the toughness of the material is better. However, when the particle size is too large, there is a micro-stratification in the combination of the matrix resin, so that the composite material can not form an organic whole, not only can not improve the mechanical properties of its material, but it will cause the internal defects of the product, which will cause the product to be stressfully damaged. According to the requirements of the product hanging with a suitable size of wollastonite filled with modified.

Effect of Modified Wollastonite Filled PP on the Temperature Resistance of Composites

The thermal properties that affect the use of plastic products are mainly heat resistance and low temperature resistance. The heat-resistant temperature is mainly expressed by heat distortion temperature, Martin heat-resistant temperature and Vicat softening point. The low temperature resistance is generally expressed by brittle temperature. In this experiment, the heat distortion temperature is used as the index to measure the heat resistance of the plastic. The composite material of PPJ340 plastic is added according to different proportions of HJMF-1250 modified wollastonite. The heat distortion temperature is tested according to the standard requirements. The It can be seen that the needle-like wollastonite powder can enhance the mechanical properties of plastic, because of its excellent temperature resistance can significantly improve the temperature resistance of plastic, the powder added 30% when the heat distortion temperature than pure resin increased by nearly 60% , This will significantly expand the application of plastic and the scope of use.

Table 3   different content of silica lime under the composite material test deformation temperature

In conclusion

(1) resource-rich acicular wollastonite is fully utilized to the polypropylene and its resin filled with the modified, the composite material a number of indicators significantly increased, reducing the amount of resin, reduce costs.

(2) the effect of surface modification of wollastonite directly affect its filling effect in the resin.

(3) According to the experimental requirements to select the appropriate size and aspect ratio of wollastonite to achieve the desired effect, not the smaller the diameter of the larger diameter ratio can achieve the desired effect.

(4) the appropriate proportion of addition to reflect the unique properties of wollastonite-shaped fibers.

(5) acicular wollastonite to improve the heat resistance of PP plastic has a more intuitive help, but also on the processing performance of materials will not have much impact.