Basic Introduction Of Plastic Packaging Raw Materials

Author : Guangzhou Lefeng Plastic Bags Co.,Ltd

Update time : 2022-04-23 11:14:06

Today we will share the basic knowledge of plastic packaging raw materials so that we can understand more about plastic bags in our company.

1. Representation method: (English abbreviation thickness.)

Example: BOPP30 (English abbreviation + thickness, unit μm, often omitted)

1μm=10¯ 6m

1 micron = 10¯ 6 meters

Usually the plastic materials we use are thermoplastic materials.

2. Commonly used plastic films:

①, PE (the most used in the world, also known as "plastic flower". LDPE, MDPE, HDPE, LLDPE, metallocene PE);

②, PVC;

③, PP (including BOPP, KOP, YOPP, CPP, etc.);

④, PS;

⑤, PET;

⑥, NY (PA);

⑦, PC;

⑧, AL aluminum foil (metal in a broad sense).

3. The molding process of plastic film mainly includes:

①, Casting - example: CPE, CPP (under normal circumstances, those containing the letter C are casting)

②, stretching - example: BOPP

③, extrusion - also known as blow molding, for example: PP

④, rolling - multi-fingered metal, such as AL

4. Introduction to the properties of commonly used plastic films

(1), PE polyethylene. Also known as "plastic flower", the main types of PE are low density LDPE, medium density MDPE, high density HDPE, linear low density LLDPE. Generally, PE can only be used for boiling below 90°C, while LLDPE can be boiled at 100°C, which is higher than that of LDPE, but cannot be used for high-temperature cooking. 70℃-80℃ boiled, that is ≤100℃. Boil around 100℃, and high temperature cooking type RCPP can be used if it is greater than or equal to 120℃. HDPE is not suitable for individual films because it is too brittle. The heat sealing performance of HDPE is better than that of LDPE.

Basic properties of PE:

①, Translucent (transparency is not very good);

②, good softness (touch by hand, PE is not as stiff as OPP, soft and somewhat curled);

③, can be stretched (not suitable for very thin films, usually about 20μm).

Because PE film has good flexibility and tensile properties, it is easy to be scratched and perforated. According to the process, PE in a broad sense can be CPE after casting (that is, not stretched), and PE in a broad sense is blown, which is what we usually call ordinary PE (with micro-stretchability).
CPE and PE:

① The heat sealing performance of CPE is better than that of PE, and it is suitable for the inner layer of plastic bags, that is, the heat sealing layer;

②, CPE has tensile properties, but the tensile strength is not as good as PE, that is, the tensile strength of CPE is less than that of PE; CPE can only be printed on No. 3 and No. 4 machines, mainly because No. 1 and No. 2 machines belong to the early Hong Kong machine, the tension system is not good, and CPE has tensile properties, so it is easy to cause inaccurate positioning;

③, CPE has good moisture-proof performance;

④, CPE is not resistant to high temperature;

⑤ . Due to the poor adhesion of PE to the ink, the printing performance is not good. If you want to improve it, you can use: corona treatment (that is, to generate a high-voltage electric field), which can increase the surface energy and enhance the adhesion to the ink. The most basic should be ≥ 38dgn(dyne);

Methods of surface pretreatment:

a. Flame treatment (that is, cooling after heating);

b. Corona treatment;

c. Chemical corrosion (using chemicals to soak the film);

d. Mechanical grinding (increase the surface roughness of the film);

e. gluing;

⑥ The gas barrier property of PE is general (that is, the barrier property to oxygen is general, and it is not suitable for packing greasy articles). The two most common heat sealing materials: PE, CPP. The cold resistance of PE is very good, generally -18 ℃, the cold resistance of CPP is poor, and it becomes brittle below 0 ℃ (the packaging bag using CPP is easy to burst in the north in winter)

⑦, good cold resistance. It is mainly used for the heat sealing layer of the packaging of frozen items (-18℃).

⑧, poor oil resistance. If PE is used to package oily items, the oil is easy to penetrate into the PE layer, resulting in a waxy smell. For example, the oily package of instant noodles should not use PE.

⑨, PE has poor UV resistance. After three times of ultraviolet radiation, it is easy to age and become brittle.
(2), PP polypropylene. It is the lightest resin of all plastics and the least dense.

①, high transparency;

②, good printing performance;

3. The mechanical strength is higher than that of PE, that is, it is not easy to stretch, especially the performance of biaxial stretching is relatively low;

④, good moisture resistance, often used to package the surface of biscuits;

⑤ , acid, alkali, grease performance is good, such as oil, the inner heat sealing layer usually use CPP instead of PE;

⑥, the gas barrier performance is general;

⑦, high temperature resistance is better than PE, worse than PET, NY;

⑧ , not cold-resistant (except for BOPP biaxial stretching);

Types of PP:

a, BOPP biaxially oriented polypropylene, used for surface printing, no heat sealing performance, cold resistance temperature can reach -30 ℃ - -40 ℃.

b. CPP cast polypropylene (unstretched polypropylene) has good heat sealing performance and is not cold-resistant. Mainly divided into cooking RCPP: high temperature resistance, high price; ordinary CPP: poor high temperature resistance;

c. If it is expressed as PP, it is blow-molded polypropylene, which has heat-sealability, which is between BOPP and CPP in heat-sealability and cold resistance.

(3), double-sided heat-sealed polypropylene. For example, Procter & Gamble's Tide laundry detergent uses double-sided heat-sealed polypropylene, and its biggest feature is that both sides can be heat-sealed.

(4), PL polypropylene pearlescent film (including pearlescent masterbatch). There is heat sealability, but the heat sealability is not good.

Classification of PL:

① 、Ordinary PL, with transparency;

② , whitened PL, no transparency; the outer label of the bottle used for Coca-Cola is this kind of raw material.

(5), YOPP biaxially oriented polypropylene matte film. It is coated with a layer of matte film on the outside of BOPP, which can absorb ultraviolet rays, play a partial shading effect, have a "matt" effect, and have a decorative effect.

①, no heat sealing performance;

②, similar to BOPP.

Okay,this is the basic information of plastic packaging raw materials,next we will introduce printing process knowledge,please pay attention to our next news,thank you.

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