How to change the hardness of PE plastic bottles?

PE plastic bottles are widely used in packaging containers for personal care, daily chemical, industrial chemical, food and more industries. Polyethylene (PE) is one of the five synthetic resins, PE material has excellent properties: good resistance to high and low temperatures, good mechanical properties, resistant to oil, fat, dilute acids and alkalis, and most solvents. These characteristics made PE plastic bottles durable and strength.

While in practical applications, based on different purposes of use, customers will have different needs, some customers want hardness bottles, such as detergent bottles, shampoo bottles, lotion bottles. And some customers need softer bottles to control the liquid volume, such as squeeze bottles, sauce bottles, eye drops, hair applicator bottles, and some need medium soft and hard bottles. So how to adjust the hardness of PE bottles? As professional pe lotion bottle supplier, we can meet the different needs of customers in our pe lotion bottle factory.

Hardness is the ability of a material to resist the pressure of other harder objects into its surface. Plastic blending improvement method is to blend high hardness resin in low hardness resin to improve its overall hardness. Common blending resins are: PS, PMMA, ABS and MF, etc. The resins to be modified are mainly PE, PA, PTFE and PP, etc.

Below are different ways for modify the PE bottles by plastic blending improvement method.

1. PE Plastic Bottles Blending of HDPE and LDPE

Polyethylene is divided into different types: low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE) .LDPE is softer, but it is not suitable for making various hollow containers and other products because of its poor strength and air tightness, on the other hand, HDPE is harder and lacks flexibility to make soft products. The blending of two densities of polyethylene can produce soft and hard polyethylene materials, which can be adapted to a wide range of applications.

Table 1 .give the relationship between the properties and composition of two different densities of polyethylene blends.

HDPE:LDPE	​Density（g/m³）	​Crystallization Degree	Hardness Shore (D)	Melt index(g/10min)	Softening point(℃)	Tensile strength (MPa)	Elongation at break(%)
0：100	0.920	48	49~51	1.86	106.5	0.13	750
​10：90	0.923	50	53~55	3.24	109.2	0.12	400
20：80	0.926	52	52~55	5.94	109.4	0.13	275
30：70	0.929	54	53~56	10.58	110	0.14	100
40：60	0.931	55	56~57	17.06	115	0.15	75
50：50	​0.933	57	55~57	33.00	115.6	0.17	25
60：40	0.937	59	58~59	60.0	115.6	0.17	10
70：30	0.934	64	59~61	76	118.3	0.16	10
80：20	0.947	63	61~62	144	118.8	0.15	10
90：10	0.950	69	62~64	255	119.4	0.14	10
100：0	0.952	70	63~65	467	121.1	0.14	10

As can be seen from Table 1, a series of blends with intermediate properties can be obtained after blending two polyethylenes with different densities in various ratios. The variation of these polyethylene properties, such as density, crystallinity, hardness, softening point, etc., is quite regular and conforms to the linear summation values calculated according to the blending ratio of the raw materials. However, the changes in elongation at break and tensile strength are slightly special. When the ratio of blending in HDPE is less than 60:40, the elongation at break is basically unchanged, both when the ratio is 50:50, but then the tensile strength appears a great value.

2.PE Plastic Bottles Blending of PE and ethylene vinyl acetate (EVA).

Hdpe and ethylene vinyl acetate (EVA) blends have excellent flexibility, processability, better permeability and printability, and are therefore widely valued.

EVA is a random copolymer of ethylene and vinyl acetate (VAC). EVA has a certain degree of crystallinity when the vinyl acetate content is low.

EVA for blending, low crystallinity requirements, so the application of VAC content of 40% to 70% of EVA. in addition, when EVA in VAC content in the range of 10% to 20% for plastic materials, and VAC content of more than 30% is an elastic material.

EVA is often blended with other polymers, as the latter's modifier, which is due to EVA has good flexibility, toughness, stress cracking resistance and bonding properties.

PE and EVA blends can vary in a wide range of performance, which is due to the content of VAC in the EVA used, the molecular weight of EVA, the amount of blending of EVA, blend preparation and processing molding conditions and many other factors affect its performance.

3.PE Plastic Bottles Blending of PP and PE

PP and PE blends are usually blended using mechanical blending method, easy to operate, the blend composition than easy to change, so the blend performance is easy to adjust. PP and PE blend tensile strength generally decreases with the increase in PE content; PP and PE blend, toughness has improved, for example, blended with 10% to 40% high-density polyethylene (HDPE) polypropylene blend, at -20 ℃ when the ball impact The strength is more than eight times higher than that of PP, and the processing fluidity is increased, so it is suitable for injection molding of large containers.

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